a. Universe b. Galaxy c. Plasma d. Environment.
Q3. Distinguishing Boson Stars from Black Holes and Neutron Stars from Tidal Interactions in Inspiraling Binary Systems. Noah Sennett, Tanja Hinderer, Jan Steinhoff, Alessandra Buonanno, Serguei Ossokine. (Submitted on 27 Apr 2017): ABSTRACT: Binary systems containing boson stars---self-gravitating configurations of a complex scalar field--- can potentially mimic black holes or neutron stars as gravitational-wave sources. We investigate the extent to which tidal effects in the gravitational-wave signal can be used to discriminate between these standard sources and boson stars. We consider spherically symmetric boson stars within two classes of scalar self-interactions: an effective-field-theoretically motivated quartic potential and a solitonic potential constructed to produce very compact stars. We compute the tidal deformability parameter characterizing the dominant tidal imprint in the gravitational-wave signals for a large span of the parameter space of each boson star model. We find that the tidal deformability for boson stars with a quartic self-interaction is bounded below by Λmin ≈280 and for those with a solitonic interaction by Λmin≈1.3. Employing a Fisher matrix analysis, we estimate the precision with which Advanced LIGO and third-generation detectors can measure these tidal parameters using the in-spiral portion of the signal. We discuss a new strategy to improve the distinguishability between black holes/neutrons stars and boson stars by combining deformability measurements of each compact object in a binary system, thereby eliminating the scaling ambiguities in each boson star model. Our analysis shows that current-generation detectors can potentially distinguish boson stars with quartic potentials from black holes, as well as from neutron-star binaries if they have either a large total mass or a large mass ratio. Discriminating solitonic boson stars from black holes using only tidal effects during the in-spiral will be difficult with Advanced LIGO, but third-generation detectors should be able to distinguish between binary black holes and these binary boson stars. Phys. Rev. D 96, 024002 (2017) arXiv:1704.08651 [gr-qc].Nuclear Physics B. Volume 564, Issues 1–2, 3 January 2000, Pages 185-203. EWM et al: The present surge for the astrophysical relevance of boson stars stems from the speculative possibility that these compact objects could provide a considerable fraction of the non-baryonic part of dark matter within the halo of galaxies. For a very light `universal' axion of effective string models, their total gravitational mass will be in the most likely range of ∼0.5 M⊙ of MACHOs. According to this framework, gravitational microlensing is indirectly “weighing” the axion mass, resulting in ∼10^−10 eV/c^2. This conclusion is not changing much, if we use a dilaton type self-interaction for the bosons. Moreover, we review their formation, rotation and stability as likely candidates of astrophysical
a. scenario b. view c.significance d. importance
Q4. arXiv:1911.09691 [astro-ph.GA]: Modeling the magnetized Local Bubble from dust data. V. Pelgrims, K. Ferrière, F. Boulanger, R. Lallement, L. Montier. (Submitted on 21 Nov 2019) ABSTRACT: The Sun is embedded in the so-called Local Bubble (LB) -- a cavity of hot plasma created by supernova explosions and surrounded by a shell of cold dusty gas. Knowing the local distortion of the Galactic magnetic field associated with the LB is critical to model interstellar polarization data at high Galactic latitudes. This paper relates the structure of the Galactic magnetic field on the LB scale to three-dimensional (3D) maps of the local interstellar medium (ISM). In a first part, we extract the geometry of the LB shell, particularly its inner surface, from 3D dust extinction maps of the local ISM. We expand the shell inner surface in spherical harmonics, up to a variable maximum degree, which enables us to control the level of complexity of the modeled surface. In a second part, we apply to the modeled shell surface an analytical model for the ordered magnetic field in the shell. This magnetic field model is successfully fitted to the Planck 353 GHz dust polarized emission maps over the Galactic polar caps. Our work represents a new approach in modeling the 3D structure of the Galactic magnetic field. We expect our methodology and our results to be useful both to model the local ISM as traced by its different components and to model the dust polarized emission, a most awaited input for studies of the polarized foregrounds to the Cosmic Microwave
a. structure b. Background c. caps d. dust.
Q5. arXiv:1911.09719 [astro-ph.HE]: Low frequency view of GRB 190114C reveals time varying shock micro-physics. . K. Misra, et al., (Submitted on 21 Nov 2019): ABSTRACT: We present radio and optical afterglow observations of the TeV-bright long Gamma Ray Burst (GRB) 190114C, which was detected by the MAGIC telescope at a redshift of z=0.425. Our observations with ALMA, ATCA, and uGMRT were obtained by our low frequency observing campaign and range from ~1 to ~140 days after the burst and the optical observations were done with the 0.7-m GROWTH-India telescope up to ~25 days after the burst. Long term radio/mm observations reveal the complex nature of the afterglow, which does not conform to the predictions of the standard afterglow model. We find that the microphysical parameters of the external forward shock, representing the share of shock-created energy in the non-thermal electron population and magnetic field, are evolving with time. The kinetic energy in the blast-wave is almost an order of magnitude higher than that measured in the prompt
a. observation b. shock c. emission d. blast.
Q6. arXiv:1911.09774 [astro-ph.HE]: Cosmic ray transport in starburst galaxies. Mark R. Krumholz, Roland M. Crocker, Siyao Xu, A. Lazarian, M. T. Rosevear, Jasper Bedwell-Wilson. (Submitted on 21 Nov 2019): ABSTRACT: Starburst galaxies are efficient γ-ray producers, because their high supernova rates generate copious cosmic ray (CR) protons, and their high gas densities act as thick targets off which these protons can produce neutral pions and thence γ-rays. In this paper we present a first-principles calculation of the mechanisms by which CRs propagate through such environments, combining astrochemical models with analysis of turbulence in weakly ionised plasma. We show that CRs cannot scatter off the strong large-scale turbulence found in starbursts, because efficient ion-neutral damping prevents such turbulence from cascading down to the scales of CR gyroradii. Instead, CRs stream along field lines at a rate determined by the competition between streaming instability and ion-neutral damping, leading to transport via a process of field line random walk. This results in an effective diffusion coefficient that is nearly energy-independent up to CR energies of ∼1TeV. We apply our computed diffusion coefficient to a simple model of CR escape and loss, and show that the resulting γ-ray spectra are in good agreement with the observed spectra of the starbursts NGC 253, M82, and Arp 220. In particular, our model reproduces these galaxies' relatively hard GeV γ-ray spectra and softer TeV spectra without the need for any fine-tuning of advective escape times or the shape of the CR injection
a. energy b. spectrum c. diffusion d. starburst.
Q7. arXiv:1911.09850 [astro-ph.CO]: Signals of Axion Like Dark Matter in Time Dependent Polarization of Light. So Chigusa, Takeo Moroi, Kazunori Nakayama. (Submitted on 22 Nov 2019): ABSTRACT: We propose a class of new possibilities for the search of axion-like particles (ALPs) by using time series data of the polarization angle of the light. If the condensation of an ALP plays the role of dark matter, the polarization plane of the light oscillates during the propagation through the condensation of the ALP. Thus, we may be able to detect the signal of the ALP by continuously observing the polarization plane. We study the sensitivities of the ALP search of this class, paying particular attention to the light coming from astrophysical sources such as protoplanetary disks, supernova remnants, the foreground emission of the cosmic microwave background, and so on. We show that, for the ALP mass of ∼10^−22 --10^−19 eV, the ALP search of our proposal may reach the parameter region which is unexplored by other searches
a. yet b. not found c. failed d. unconfirmed.
Q8. arXiv:1911.10064 [astro-ph.IM]: Balloon-borne video observations of Geminids 2016. Francisco Ocaña, et al.,(Submitted on 12 Nov 2019): ABSTRACT: We investigate the observation of meteors with video cameras in stratospheric balloons, overcoming tropospheric handicaps like weather and extinction. We have studied the practical implementation of the idea, designed and tested instrumentation for balloon-borne missions. We have analysed the data of the Geminids 2016 campaign, determining the meteoroid flux just before the maximum. This text is an adaption of the work by the first author for his PhD Thesis: Techniques for near-Earth interplanetary matter detection and characterisation from optical ground-based observatories (Ocaña, 2017). Refer to his thesis for further detail. The lines here are a summary of the presentation given, for the sake of completeness of these proceedings of the IMC 2018 in Pezinok-Modra. The multimedia material shown during the presentation at IMC 2018 can be found in the Zenodo repository for the ORISON Project and Daedalus
a. experiment b. scenario c. Project d. research.
Q9. arXiv:1911.09855 [gr-qc]: Strong Cosmic Censorship in higher curvature gravity. Akash K Mishra, Sumanta Chakraborty. (Submitted on 22 Nov 2019): ABSTRACT: Deterministic nature of general relativity is ensured by the strong cosmic censorship conjecture, which asserts that spacetime cannot be extended beyond Cauchy horizon with square integrable connection. Although this conjecture holds true for asymptotically flat black hole spacetimes in general relativity, a potential violation of this conjecture occurs in charged asymptotically de Sitter spacetimes. Since it is expected that Einstein-Hilbert action will involve higher curvature corrections, in this article we have studied whether one can restore faith in the strong cosmic censorship when higher curvature corrections to general relativity are considered. Contrary to our expectations, we have explicitly demonstrated that not only a violation to the conjecture occurs near extremality, but the violation appears to become stronger as the strength of the higher curvature term
a. decreases b. oscillates c. dominant d. increases.
Q10. arXiv:1911.11836 [astro-ph.GA]: Testing Modified Gravity with Acceleration Relations in the Milky Way. Tousif Islam, Koushik Dutta. (Submitted on 26 Nov 2019): ABSTRACT: The dynamical mass of galaxies and the Newtonian acceleration generated from the baryons have been found to be strongly correlated. This correlation is known as 'Mass-Discrepancy Acceleration Relation' (MDAR). Further investigations have revealed a tighter relation - 'Radial Acceleration Relation' (RAR) - between the observed total acceleration and the (Newtonian) acceleration produced by the baryons. So far modified gravity theories have remained more successful than Λ CDM to explain these relations. However, a recent investigation has pointed out that, when RAR is expressed as a difference between the observed acceleration and the expected Newtonian acceleration due to baryons (which has been called the 'Halo acceleration relation or HAR'), it provides a stronger test for modified gravity theories and dark matter hypothesis. Extending our previous work \citep{kt2018}, we present a case study of modified gravity theories, in particular Weyl conformal gravity and Modified Newtonian Dynamics (MOND), using recent inferred acceleration data for the Milky Way. We investigate how well these theories of gravity and the RAR scaling law can explain the current
a. theory b. observation c. relation d. data.
Q11. arXiv:1911.12024 [astro-ph.HE]: Probing the emission states of PSR J1107-5907. Jingbo Wang, et al., (Submitted on 27 Nov 2019): ABSTRACT: The emission from PSR J1107-5907 is erratic. Sometimes the radio pulse is undetectable, at other times the pulsed emission is weak, and for short durations the emission can be very bright. In order to improve our understanding of these state changes, we have identified archival data sets from the Parkes radio telescope in which the bright emission is present, and find that the emission never switches from the bright state to the weak state, but instead always transitions to the off state. Previous work had suggested the identification of the off state as an extreme manifestation of the weak state. However, the connection between the off and bright emission reported here suggests that the emission can be interpreted as undergoing only two emission states: a bursting state consisting of both bright pulses and nulls as well as the weak-emission
a. rate b. archival c. state d. dominance.
Q12.arXiv:1911.12025 [astro-ph.HE]: A peculiar cyclotron line near 16 keV detected in the 2015 outburst of 4U 0115+63? Bai-Sheng Liu, et al., Submitted on 27 Nov 2019): ABSTRACT: In 2015 October, the Be/X-ray binary 4U 0115+63 underwent a type II outburst, reaching an X-ray luminosity of about 10^38 erg/s. During the outburst, Nuclear Spectroscopic Telescope Array ({\it NuSTAR}) performed two Target of Opportunity observations. Using the broad-band spectra from {\it NuSTAR} (3−79 keV), we have detected multiple cyclotron lines of the source, i.e., ∼12, 16, 22 and 33/35 keV. Obviously, the 16 keV line is not a harmonic component of the 12 keV line. As described by the phase-dependent equivalent widths of these cyclotron lines, the 16 keV and 12 keV lines are two distinct fundamental lines. We propose a model, in which the two line sets are formed in different regions of the same magnetic pole. That is, the former is produced in the outer-region of the column base, and the latter is at a height of ∼1 km inside the column if the magnetic dipole field is assumed. Thus the magnetic field, deduced from the cyclotron line near 16 keV, is ∼{1.4*10^12}
a. M b. G. c. D d. F.
Q13.arXiv:1912.04904 [astro-ph.EP]: Mass-Metallicity Trends in Transiting Exoplanets from Atmospheric Abundances of H2O, Na, and K: Luis Welbanks et al.,(Submitted on 10 Dec 2019): ABSTRACT: Atmospheric compositions can provide powerful diagnostics of formation and migration histories of planetary systems. We investigate constraints on atmospheric abundances of H2O, Na, and K, in a sample of transiting exoplanets using latest transmission spectra and new H2 broadened opacities of Na and K. Our sample of 19 exoplanets spans from cool mini-Neptunes to hot Jupiters, with equilibrium temperatures between ∼300 and 2700 K. Using homogeneous Bayesian retrievals we report atmospheric abundances of Na, K, and H2O, and their detection significances, confirming 6 planets with strong Na detections, 6 with K, and 14 with H2O. We find a mass-metallicity trend of increasing H2O abundances with decreasing mass, spanning generally substellar values for gas giants and stellar/superstellar for Neptunes and mini-Neptunes. However, the overall trend in H2O abundances, from mini-Neptunes to hot Jupiters, is significantly lower than the mass-metallicity relation for carbon in the solar system giant planets and similar predictions for exoplanets. On the other hand, the Na and K abundances for the gas giants are stellar or superstellar, consistent with each other, and generally consistent with the solar system metallicity trend. The H2O abundances in hot gas giants are likely due to low oxygen abundances relative to other elements rather than low overall metallicities, and provide new constraints on their formation mechanisms. The differing trends in the abundances of species argue against the use of chemical equilibrium models with metallicity as one free parameter in atmospheric retrievals, as different elements can be differently
a. decreased b enhanced c. abundant d. formed.
Q14.arXiv:1912.05290 [astro-ph.SR]: The Single Star Path to Be Stars. Ben Hastings, Chen Wang, Norbert Langer. (Submitted on 11 Dec 2019): ABSTRACT: Be stars are rapidly rotating B main sequence stars, which show line emission due to an outflowing disc. By studying the evolution of rotating single star models, we can assess their contribution to the observed Be star populations. We identify the main effects which are responsible for single stars to approach critical rotation as functions of initial mass and metallicity, and predict the properties of populations of rotating single stars. We perform population synthesis with single star models of initial masses ranging between 3 and 30 solar masses, initial equatorial rotation velocities between 0 and 600 kms^−1 at compositions representing the Milky Way, Large and Small Magellanic Clouds. These models include efficient core-envelope coupling mediated by internal magnetic fields and correspond to the maximum efficiency of Be star production. We predict Be star fractions and the positions of fast rotating stars in the colour-magnitude diagram. We identify stellar wind mass-loss and the convective core mass fraction as the key parameters which determine the time dependance of the stellar rotation rates. Using empirical distributions of initial rotational velocities,our single star models can reproduce the trends observed in Be star fractions with mass and metallicity. However,they fail to produce a significant number of stars rotating very close to critical. We also find that rapidly rotating Be stars in the Magellanic Clouds should have significant surface nitrogen enrichments, which may be in conflict with abundance determinations of Be stars. Single star evolution may explain the high number of Be stars if 70 to 80% of critical rotation would be sufficient to produce the Be phenomenon. However even in this case, the unexplained presence of many Be stars far below the cluster turn-off indicates the importance of the binary channel for Be star
a formation b. evolution c. production d. abundance.
Q15. arXiv:1912.05343 [astro-ph.SR]: Spectroscopic characterization of nine binary star systems as well as HIP107136 and HIP107533. T. Heyne, et al., (Submitted on 11 Dec 2019): ABSTRACT: We present the results of our 2nd radial velocity monitoring campaign, carried out with the Échelle spectrograph FLECHAS at the University Observatory Jena in the course of the Großschwabhausen binary survey between December 2016 and June 2018. The aim of this project is to obtain precise radial velocity measurements for spectroscopic binary stars in order to redetermine, verify, improve and constrain their Keplerian orbital solutions. In this paper we describe the observations, data reduction and analysis and present the results of this project. In total, we have taken 721 RV measurements of 11 stars and derived well determined orbital solutions for 9 systems (7 single-, and 2 double-lined spectroscopic binaries) with periods in the range between 2 and 70 days. In addition, we could rule out the orbital solutions for the previously classified spectroscopic binary systems HIP107136 and HIP107533, whose radial velocities are found to be constant on the km/s-level over a span of time of more than 500 days. In the case of HIP2225 a significant change of its systematic velocity is detected between our individual observing epochs, indicating the presence of an additional companion, which is located on a wider orbit in this
a. system b. order c. solution d. change.
Q16. arXiv:1912.05548 [astro-ph.GA]: Molecular Gas Inflows and Outflows in Ultraluminous Infrared Galaxies at z∼0.2 and one QSO at z=6.1 R. Herrera-Camus, et al. ,(Submitted on 11 Dec 2019): ABSTRACT: Aims. We aim to search and characterize inflows and outflows of molecular gas in four ultraluminous infrared galaxies (ULIRGs) at z∼0.2−0.3 and one distant QSO at z=6.13. Methods. We use Herschel PACS and ALMA Band 7 observations of the hydroxyl molecule (OH) line at rest-frame wavelength 119μm which in absorption can provide unambiguous evidence for inflows or outflows of molecular gas in nuclear regions of galaxies. Our study contributes to double the number of OH observations of luminous systems at z∼0.2−0.3 , and push the search for molecular outflows based on the OH transition to z∼6. Results. We detect OH high-velocity absorption wings in three of the four ULIRGs. In two cases, IRAS F20036-1547 and IRAS F13352+6402, the blueshifted absorption profiles indicate the presence of powerful and fast molecular gas outflows. Consistent with an inside-out quenching scenario, these outflows are depleting the central reservoir of molecular gas at a similar rate than the intense star formation activity. In the case of the starburst-dominated system IRAS 10091+4704, we detect an inverted P-Cygni profile that is unique among ULIRGs and indicates the presence of a fast (∼400 km s^−1) inflow of molecular gas at a rate of ∼100 M⊙yr ^−1towards the central region. Finally, we tentatively detect (∼3σ) the OH doublet in absorption in the z=6.13 QSO ULAS J131911+095051. The OH feature is blueshifted with a median velocity that suggests the presence of a molecular outflow, although characterized by a modest molecular mass loss rate of ∼200 M⊙yr^−1. This value is comparable to the small mass outflow rates found in the stacking of the [CII] spectra of other z∼6 QSOs and suggests that ejective feedback in this phase of the evolution of ULAS J131911+095051 has
a. sacked b. shifted c. subsided d. enhanced.
Q17. arXiv:1912.05605 [astro-ph.SR]: The Role of Magnetic Fields in Protostellar Outflows and Star Formation. Ralph E. Pudritz, Tom P. Ray. (Submitted on 11 Dec 2019): ABSTRACT: The role of outflows in the formation of stars and the protostellar disks that generate them is a central question in astrophysics. Outflows are associated with star formation across the entire stellar mass spectrum. In this review, we describe the observational, theoretical, and computational advances on magnetized outflows, and their role in the formation of disks and stars of all masses in turbulent, magnetized clouds. The ability of torques exerted on disks by magnetized winds to efficiently extract and transport disk angular momentum was developed in early theoretical models and confirmed by a variety of numerical simulations. The recent high resolution ALMA observations of disks and outflows now confirm several key aspects of these ideas, e.g. that jets rotate and originate from large regions of their underlying disks. New insights on accretion disk physics show that magneto-rotational instability (MRI) turbulence is strongly damped, leaving magnetized disk winds as the dominant mechanism for transporting disk angular momentum. This has major consequences for star formation, as well as planet formation. Outflows also play an important role in feedback processes particularly in the birth of low mass stars and cluster formation. Despite being almost certainly fundamental to their production and focusing, magnetic fields in outflows in protostellar systems, and even in the disks, are notoriously difficult to measure. Most methods are indirect and lack precision, as for example, when using optical/near-infrared line ratios. Moreover, in those rare cases where direct measurements are possible - where synchrotron radiation is observed, one has to be very careful in interpreting derived values. Here we also explore what is known about magnetic fields from observations, and take a forward look to the time when facilities such as SPIRou and the SKA are in routine
a. system b. operation c. radiation d. measurement.
Q18.arXiv:1912.05632 [astro-ph.HE]: Search for Gamma-ray Spectral Lines from Dark Matter Annihilation in Dwarf Galaxies with the High-Altitude Water Cherenkov Observatory. The HAWC Collaboration. (Submitted on 11 Dec 2019): ABSTRACT: Local dwarf spheroidal galaxies (dSphs) are nearby dark-matter dominated systems, making them excellent targets for searching for gamma rays from particle dark matter interactions. If dark matter annihilates or decays directly into two gamma rays (or a gamma ray and a neutral particle), a monochromatic spectral line is created. At TeV energies, no other processes are expected to produce spectral lines, making this a very clean indirect dark matter search channel. With the development of event-by-event energy reconstruction, we can now search for spectral lines with the High Altitude Water Cherenkov (HAWC) Observatory. HAWC is a wide field of view survey instrument located in central Mexico that observes gamma rays from <1 TeV to >100 TeV. In this work we present results from a recent search for spectral lines from local, dark matter dominated dwarf galaxies using 1038 days of HAWC data. We also present updated limits on several continuum channels that were reported in a previous publication. Our gamma-ray spectral line limits are the most constraining obtained so far from 20 TeV to
a. 40 TeV b. 60 TeV. c. 80 TeV d. 100 TeV.
Q19. arXiv:1912.05857 [astro-ph.GA]: Metal abundances in the MACER simulations of the hot interstellar medium. S. Pellegrini (1), Z. Gan (2,3), J.P. Ostriker (2), L. Ciotti (1) ((1) Dept. of Physics and Astronomy, University of Bologna, (2) Dept. of Astronomy, Columbia University, (3) Shanghai Astronomical Observatory): (Submitted on 12 Dec 2019): ABSTRACT: A hot plasma is the dominant phase of the interstellar medium of early-type galaxies. Its origin can reside in stellar mass losses, residual gas from the formation epoch, and accretion from outside of the galaxies. Its evolution is linked to the dynamical structure of the host galaxy, to the supernova and AGN feedback, and to (late-epoch) star formation, in a way that has yet to be fully understood. Important clues about the origin and evolution of the hot gas come from the abundances of heavy metals, that have been studied with increasing detail with XMM-Newton and Chandra. We present recent high resolution hydrodynamical simulations of the hot gas evolution that include the above processes, and where several chemical species, originating in AGB stars and supernovae of type Ia and II, have also been considered. The high resolution, of few parsecs in the central galactic region, allows us to track the metal enrichment, transportation and dilution throughout the galaxy. The comparison of model results with observed abundances reveals a good agreement for the region enriched by the AGN wind, but also discrepancies for the diffuse hot gas; the latter indicate the need for a revision of standard assumptions, and/or the importance of neglected effects as those due to the dust, and/or residual uncertainties in deriving abundances from the X-ray
a. spectra b. diffraction c. studies d. resolution.
Q20. arXiv:1912.05894 [astro-ph.IM]: A Mini-Imaging Air Cherenkov Telescope. S. Njoh Ekoume, et al., (Submitted on 12 Dec 2019): ABSTRACT: In this paper we describe the different software and hardware elements of a mini-telescope for the detection of cosmic rays and gamma-rays using the Cherenkov light emitted by their induced particle showers in the atmosphere. We estimate the physics reach of the standalone mini-telescope and present some results of the measurements done at the Sauverny Observatory of the University of Geneva and at the Saint-Luc Observatory, which demonstrate the ability of the telescope to observe cosmic rays with energy above about 100 TeV. Such a mini-telescope can constitute a cost-effective out-trigger array that can surround other gamma-ray telescopes or extended air showers detector arrays. Its development was born out of the desire to illustrate to students and amateurs the cosmic ray and gamma-ray detection from ground, as an example of what is done in experiments using larger telescopes. As a matter of fact, a mini-telescope can be used in outreach night events. While outreach is becoming more and more important in the scientific community to raise interest in the general public, the realisation of the mini-telescope is also a powerful way to train students on instrumentation such as photosensors, their associated electronics, acquisition software and data taking. In particular, this mini-telescope uses silicon photomultipliers (SiPM) and the dedicated ASIC,
a. CITIR b. CITIRAC c. CIOTIROC d. CITIROC.
Q21. A word is represented by only one st of numbers as given in any one of the alternatives. The sets of numbers given in the alternatives are represented by two classes of alphabets as in two matrices given below. The columns and rows of Matrix I are numbered from 0 to 4 and of Matrix II are numbered from 5 to 9. A letter from these matrices can be represented by its row and next by its column. e.g., A can be represented by 00, 13 and T can be represented by 56, 68, 89 etc. Question: Identify the set for the word POET.
Matrix I Matrix II
0 1 2 3 4 5 6 7 8 9
0 A U O T B 5 P T A M E
1 T E P A W 6 O I O T M
2 R M G G T 7 E A L T M
3 U M M C L 8 R A R L T
4 P L N E C 9 N P E O P
a) 56, 43, 32, 97 b) 89, 43, 40, 12 c) 96, 02, 75,10 d) 78, 11, 12, 10.
Q22. arXiv:1912.11057 [astro-ph.GA]: Cosmic-ray Particles in the Galactic Center: Blowing in the Wind. F. Yusef-Zadeh, M. Wardle, I. Heywood, W. Cotton, M. Royster. (Submitted on 23 Dec 2019):ABSTRACT: Recent results from multi-wavelength observations of the inner few hundred pc of the Galactic center have added two new characteristics to the ISM in this unique region. One is the cosmic ray ionization rate derived from H+3 measurements is at least two orders of magnitudes higher than in the disk of the Galaxy. The other is the bipolar thermal X-ray and synchrotron emission from this region, suggesting a relic of past activity. We propose that the high cosmic ray pressure drives a large-scale wind away from the Galactic plane and produces the bipolar emission as well as highly blue-shifted diffuse gas detected in H(+3) absorption studies. We then discuss the interaction of large-scale winds with a number of objects, such as cloudlets and stellar wind bubbles, to explain the unusual characteristics of the ISM in this region including the nonthermal radio filaments. One of the implications of this scenario is the removal of gas driven by outflowing winds may regulate star formation or black hole
a. accretion b. destruction c. region d. filament.
Q23. arXiv:1912.11178 [astro-ph.EP]: Ring Morphology with Dust Coagulation in Protoplanetary Disks. JT Laune,et al. (Submitted on 24 Dec 2019): ABSTRACT: Tidal interactions between the embedded planets and their surrounding protoplanetary disks are often postulated to produce the observed complex dust substructures, including rings, gaps, and asymmetries. In this Letter, we explore the consequences of dust coagulation on the dust dynamics and ring morphology. Coagulation of dust grains leads to dust size growth which, under typical disk conditions, produces faster radial drifts, potentially threatening the dust ring formation. Utilizing 2D hydrodynamical simulations of protoplanetary disks which include a full treatment of dust coagulation, we find that if the planet does not open a gap quickly enough, the formation of an inner ring is impeded due to dust coagulation and subsequent radial drift. Furthermore, we find that a "buildup" of sub-mm sized grains often appears in the dust emission at the outer edge of the dust
a. buildup b. disk c. formation d. coagulation.
Q24. arXiv:1912.11453 [astro-ph.CO]: Dark matter with excitable levels. Andrew J. Wren. (Submitted on 24 Dec 2019):ABSTRACT: This paper explores the possibility that dark matter particles are objects with a set of excitable levels, as for a string or drum. A change in excitation is associated with the absorption or emission of a photon, and the probability of such a change is dependent on the ambient photon energy density. Particle mass comes entirely from excitations. Such dark matter with excitable levels, or DMWEL, particles have a distribution of masses which freezes out to its present-day form during the early universe. In the particular model considered, consistency with Plank CMB anisotropy observations implies a cautious lower bound on the energy of the first excitable level of 2 to 200 eV for a set of reference parameters. While laboratory detection looks to require a considerable increase in the power of controlled light-sources, it might be possible in the near future to detect or constrain DMWEL further through improved anisotropy observations, closer determination of the CMB's maximum deviation from a blackbody shape, or from gravitational probes of the dark matter power spectrum. For certain parameters near to the boundary of the region allowed by CMB anisotropies, DMWEL dark matter is cold, but with a cut-off halo mass many orders of magnitude greater than that typical for WIMP cold dark
a. detection b. matter c. future d. source.
Q25.arXiv:2001.04988 [astro-ph.GA]: The Pristine survey VIII: The metallicity distribution function of the Milky Way halo down to the extremely metal-poor regime. K. Youakim, et al., (Submitted on 14 Jan 2020): ABSTRACT: The Pristine survey uses narrow-band photometry to derive precise metallicities down to the extremely metal-poor regime ([Fe/H] < -3), and currently consists of over 4 million FGK-type stars over a sky area of ∼2 500deg2. We focus our analysis on a subsample of ∼80 000 main sequence turnoff stars with heliocentric distances between 6 and 20 kpc, which we take to be a representative sample of the inner halo. The resulting metallicity distribution function (MDF) has a peak at [Fe/H] = -1.6, and a slope of Δ(LogN)/Δ[Fe/H]=1.0±0.1 in the metallicity range of -3.4 < [Fe/H] < -2.5. This agrees well with a simple closed-box chemical enrichment model in this range, but is shallower than previous spectroscopic MDFs presented in the literature, suggesting that there may be a larger proportion of metal-poor stars in the inner halo than previously reported. We identify the Monoceros/TriAnd/ACS/EBS/A13 structure in metallicity space in a low latitude field in the anticenter direction, and also discuss the possibility that the inner halo is dominated by a single, large merger event, but cannot strongly support or refute this idea with the current data. Finally, based on the MDF of field stars, we estimate the number of expected metal-poor globular clusters in the Milky Way halo to be 5.4 for [Fe/H] < -2.5 and 1.5 for [Fe/H] < -3, suggesting that the lack of low metallicity globular clusters in the Milky Way is not due simply to statistical
a. significance b. understanding c. undersampling d. degradation.
Q26. arXiv:2001.04994 [astro-ph.HE]: Bounds on secret neutrino interactions from high-energy astrophysical neutrinos. Mauricio Bustamante, Charlotte Amalie Rosenstroem, Shashank Shalgar, Irene Tamborra (Bohr Inst. & U. Copenhagen (main) & DARK): (Submitted on 14 Jan 2020): ABSTRACT: Neutrinos offer a window to physics beyond the Standard Model. In particular, high-energy astrophysical neutrinos, with TeV-PeV energies, may provide evidence of new, "secret" neutrino-neutrino interactions that are stronger than ordinary weak interactions. During their propagation over cosmological distances, high-energy neutrinos could interact with the cosmic neutrino background via secret interactions, developing characteristic energy-dependent features in their observed energy distribution. For the first time, we look for signatures of secret neutrino interactions in the diffuse flux of high-energy astrophysical neutrinos, using 6 years of publicly available IceCube High Energy Starting Events (HESE). We find no significant evidence for secret neutrino interactions, but place competitive upper limits on the coupling strength of the new mediator through which they occur, in the mediator mass range of 1-100 MeV.
a. 1-100 MeV b. 1-1000 MeV c.1-10 MeV d. 100 MeV.
Q27. arXiv:2001.05007 [astro-ph.EP]: Observations of Protoplanetary Disk Structures. Sean M. Andrews. (Submitted on 14 Jan 2020): ABSTRACT: The disks that orbit young stars are the essential conduits and reservoirs of material for star and planet formation. Their structures, meaning the spatial variations of the disk physical conditions, reflect the underlying mechanisms that drive those formation processes. Observations of the solids and gas in these disks, particularly at high resolution, provide fundamental insights on their mass distributions, dynamical states, and evolutionary behaviors. Over the past decade, rapid developments in these areas have largely been driven by observations with the Atacama Large Millimeter/submillimeter Array (ALMA). This review highlights the state of observational research on disk structures, emphasizing three key conclusions that reflect the main branches of the field: (1) Relationships among disk structure properties are also linked to the masses, environments, and evolutionary states of their stellar hosts; (2) There is clear, qualitative evidence for the growth and migration of disk solids, although the implied evolutionary timescales suggest the classical assumption of a smooth gas disk is inappropriate; and (3) Small-scale substructures with a variety of morphologies, locations, scales, and amplitudes -- presumably tracing local gas pressure maxima -- broadly influence the physical and observational properties of disks. The last point especially is reshaping the field, with the recognition that these disk substructures likely trace active sites of planetesimal growth or are the hallmarks of planetary systems at their formation
a. event b. system c. stint d. epoch.
Q28.arXiv:2001.05433 [astro-ph.SR]: Cyclic variations in the main components of the solar large-scale magnetic field. V. N. Obridko et al. Moscow, Russia): (Submitted on 15 Jan 2020): ABSTRACT: We considered variations the dipole and the quadrupole components of the solar large-scale magnetic field. Both the axial and the equatorial dipoles exhibit a systematic decrease in the past four cycles in accordance with the general decrease of solar activity. The transition of the pole of a dipole from the polar region to mid latitudes occurs rather quickly, so that the longitude of the pole changes little. With time, however, this inclined dipole region shifts to larger longitudes, which suggests an acceleration of the dipole rotation. The mean rotation rate exceeds the Carrington velocity by 0.6%. The behavior of the quadrupole differs dramatically. Its decrease over last four cycles was much smaller than that of the dipole moment. The ratio of the quadrupole and dipole moments has increased for four cycles more than twice in contrast to the sunspot numbers, which displayed a twofold decrease for the same time interval. What about quadrupole rotation, the mean longitude of the poles of one sign decreased by 600 degrees over four cycles, which suggests that the mean rotation rate was lower than the Carrington velocity by 0.28%. We do not see however any conclusive evidence that, in the period under discussion, a mode of quadrupole symmetry was excited on the Sun along with the dipole
a. moment b. expression. c. mode d. excitation.
Q29.arXiv:2001.04993 [gr-qc]: Which part of the stress-energy tensor gravitates? Yigit Yargic, Laura Sberna, Achim Kempf. (Submitted on 14 Jan 2020). ABSTRACT: We consider the possibility that, in the semiclassical Einstein equation for cosmological spacetimes, gravity is sourced by the amount of stress-energy that is above that of the instantaneous ground state. For this possibility to be consistent, the Bianchi identities must continue to hold. This is nontrivial because it means that the ground state expectation value of the stress-energy tensor must be covariantly conserved in spite of the fact that the ground state is generally a different state at different times. We prove that this consistency condition does hold. As a consequence, we find that the vacuum stress-energy which is above the instantaneous ground state does not renormalize the cosmological constant, as long as the instantaneous ground states and the instantaneous adiabatic vacua exist. DETAILS:In the semiclassical Einstein equation, the cosmological constant receives contributions from the stress-energy of the vacuum of all matter fields [1–3]. However, the measured value of the cosmological constant is extremely small compared to the scale of each known contribution and one must also expect large contributions from new particles that might emerge at energies higher than probed so far. In addition, and most importantly, the required fine tuning is unstable in the sense that it needs to be repeatedly re-fine tuned as more loops are taken into account in the calculation of the vacuum polarization. This problem of radiative instability is an essential part of the cosmological constant problem. A key question in this context is which part of the in principle infinite stress-energy of a quantum field actually gravitates and therefore contributes to the righthand side of the semiclassical Einstein equation. CONCLUSIONS: We here considered the possibility that the source of gravity in the semiclassical Einstein equation is the difference in stress-energy expectation value between the state of the Universe and the instantaneous ground state. We proved that for homogeneous and isotropic cosmological spacetimes, for which one can of course identify the instantaneous ground state, the proposed stress-energy tensor satisfies the Bianchi identity. Finally, it will be very interesting to explore to what extent our results can be developed beyond highly symmetrical cosmological backgrounds. It will also be intriguing to understand if and how existing quantum gravity models can accommodate a first principles derivation for our
a. suggestion b. proposal c. deduction d. enumeration.
Q30. arXiv:2001.05064 [math-ph]: Quantum Walk and Dressed Photon. Misa Hamano, Hayato Saigo. (Submitted on 14 Jan 2020):ABSTRACT: A physical model called dressed photons, a composite system of photons and excitation of electrons in the nano-particles, is effectively used in the realm of near-field optics. Many interesting behaviors of dressed photons are known, especially the rapid energy transfer and the accumulation to singular points, e.g., points with strong dissipation. We propose a new modelling of dressed photons based on quantum walks, especially Grover walks on semi-infinite graphs which we call jellyfish graphs, and show a universal accumulation phenomena around the point with strong dissipation. DETAILS: The dressed photon is a useful concept to consider the behavior of a quantum field formed by combining a photon field and an electron (excitation of) field of a nanoparticle when light as a quantum field is incident on a nanoparticle system. Light and nanomaterials combine to form a quantum field that has an overwhelmingly larger number of modes (momentum and energy) than the incoming light itself. Of these modes, the momentum and energy ”relatively high” modes manifest themselves as ”a small grain of light” localized to the ”interval” of the nanoparticle. This is the dressed photon (”relatively low” modes are thought to function as a kind of heat bath.). Simply put, the dressed photons are a new kind of quantum created ”between” nanoparticles when light combines with the nanoparticle system. CONCLUSIONS: This is because when we consider the ”random walk” on a jellyfish graph, the probability in the limits is equal on all sides (The amount Jis, so to speak, the amount of deviation from ”random walk” and it can be said that it measures a kind of ”symmetry breaking”). Then, only the number of sides to which the vertices are connected, or ”degree” is important, which contradicts the importance of dissipation. Moreover, the large dissipation is often inconsistent with the fact that the order is rather ”small” (End points, etc.). These phenomena suggest that the model of ”Quantum Walk on a Jellyfish Graph” is appropriate for the analysis of the behavior of
a. dressed photons b. symmetry photons c. behavior photons d. photons.
Q31. arXiv:2001.05160 [physics.app-ph]: A phase-field model for the evaporation of thin film mixtures. Olivier J.J. Ronsin, DongJu Jang, Hans-Joachim Egelhaaf, Christoph J. Brabec, Jens Harting. (Submitted on 15 Jan 2020): ABSTRACT: The performance of solution-processed solar cells strongly depends on the geometrical structure and roughness of the photovoltaic layers formed during film drying. During the drying process, the interplay of crystallization and liquid-liquid demixing leads to the structure formation on the nano- and microscale and to the final rough film. In order to better understand how the film structure can be improved by process engineering, we aim at theoretically investigating these systems by means of phase-field simulations. We introduce an evaporation model based on the Cahn-Hilliard equation for the evolution of the fluid concentrations coupled to the Allen-Cahn equation for the liquid-vapour phase transformation. We demonstrate its ability to match the experimentally measured drying kinetics and study the impact of the parameters of our model. Furthermore, the evaporation of solvent blends and solvent-vapour annealing are investigated. The dry film roughness emerges naturally from our set of equations, as illustrated through preliminary simulations of spinodal decomposition and film drying on structured
a. model b. transformation c. substrates d. concentrations.
Q32.arXiv:2001.07742 [astro-ph.GA]: The orbital phase space of contracted dark matter halos. Thomas M. Callingham, et al. (Submitted on 21 Jan 2020): ABSTRACT: We study the orbital phase-space of dark matter (DM) halos in the AURIGA suite of cosmological hydrodynamics simulations of Milky Way analogues. We characterise halos by their spherical action distribution, a function of the specific angular momentum, and the radial action, of the DM particles. By comparing DM-only and hydrodynamical simulations of the same halos, we investigate the contraction of DM halos caused by the accumulation of baryons at the centre. We find a small systematic suppression of the radial action in the DM halos of the hydrodynamical simulations, suggesting that the commonly used adiabatic contraction approximation can result in an underestimate of the density by ~ 8%. We apply an iterative algorithm to contract the AURIGA DM halos given a baryon density profile and halo mass, recovering the true contracted DM profiles with an accuracy of ~15%, that reflects halo-to-halo variation. Using this algorithm, we infer the total mass profile of the Milky Way's contracted DM halo. We derive updated values for the key astrophysical inputs to DM direct detection experiments: the DM density and velocity distribution in the Solar
a. neighbourhood b. region c. expanse d. halo.
Q33. arXiv:2001.08087 [astro-ph.GA]: Cold gas and dust: Hunting spiral-like structures in early-type galaxies. M.K. Yıldız, R. F. Peletier, P.-A. Duc, P.Serra. (Submitted on 19 Jan 2020): ABSTRACT: Observations of neutral hydrogen (HI) and molecular gas show that 50% of all nearby early-type galaxies (ETGs) contain some cold gas. Molecular gas is always found in small gas discs in the central region of the galaxy, while neutral hydrogen is often distributed in a low-column density disc or ring typically extending well beyond the stellar body. Dust is frequently found in ETGs as well. The goal of our study is to understand the link between dust and cold gas in nearby ETGs as a function of HI content. We analyse deep optical g−r images obtained with the MegaCam camera at the Canada-France-Hawaii Telescope for a sample of 21 HI-rich and 41 HI-poor ETGs. We find that all HI-rich galaxies contain dust seen as absorption. Moreover, in 57 percent of these HI-rich galaxies, the dust is distributed in a large-scale spiral pattern. Although the dust detection rate is relatively high in the HI-poor galaxies (∼59 percent), most of these systems exhibit simpler dust morphologies without any evidence of spiral structures. We find that the HI-rich galaxies possess more complex dust morphology extending to almost two times larger radii than HI-poor objects. We measured the dust content of the galaxies from the optical colour excess and find that HI-rich galaxies contain six times more dust (in mass) than HI-poor ones. In order to maintain the dust structures in the galaxies, continuous gas accretion is needed, and the substantial HI gas reservoirs in the outer regions of ETGs can satisfy this need for a long time. We find that there is a good correspondence between the observed masses of the gas and dust, and it is also clear that dust is present in regions further than 3~Reff. Our findings indicate an essential relation between the presence of cold gas and dust in ETGs and offer a way to study the interstellar medium in more detail than what is possible with HI
a. medium b. observations c. results d. predictions.
Q34. arXiv:2001.08043 [physics.optics]: Radially polarized light beams from spin-forbidden dark excitons and trions in monolayer WSe2 . Sven Borghardt, Jens Sonntag, Jhih-Sian Tu, Takashi Taniguchi, Kenji Watanabe, Bernd Beschoten, Christoph Stampfer, Beata Ewa Kardynal. (Submitted on 22 Jan 2020): ABSTRACT: The rich optical properties of transition metal dichalcogenide monolayers (TMD-MLs) render these materials promising candidates for the design of new optoelectronic devices. Despite the large number of excitonic complexes in TMD-MLs, the main focus has been put on optically bright neutral excitons. Spin-forbidden dark excitonic complexes have been addressed for basic science purposes, but not for applications. We report on spin-forbidden dark excitonic complexes in ML WSe2 as an ideal system for the facile generation of radially polarized light beams. Furthermore, the spatially resolved polarization of photoluminescence beams can be exploited for basic research on excitons in two-dimensional materials.
a. surfaces b. excitons c. purposes d. materials.
Q35. arXiv:2001.08227 [astro-ph.SR]: Abundances in the Milky Way across five nucleosynthetic channels from 4 million LAMOST stars. Adam Wheeler et al., (Submitted on 22 Jan 2020): ABSTRACT: Large stellar surveys are revealing the chemodynamical structure of the Galaxy across a vast spatial extent. However, the many millions of low-resolution spectra observed to date are yet to be fully exploited. We employ The Cannon, a data-driven approach to estimating abundances, to obtain detailed abundances from low-resolution (R = 1800) LAMOST spectra, using the GALAH survey as our reference. We deliver five (for dwarfs) or six (for giants) estimated abundances representing five different nucleosynthetic channels, for 3.9 million stars, to a precision of 0.05 - 0.23 dex. Using wide binary pairs, we demonstrate that our abundance estimates provide chemical discriminating power beyond metallicity alone. We show the coverage of our catalogue with radial, azimuthal and dynamical abundance maps, and examine the neutron capture abundances across the disk and halo, which indicate different origins for the in-situ and accreted halo populations. LAMOST has near-complete Gaia coverage and provides an unprecedented perspective on chemistry across the
a. universe b. Milky Way c. binary pairs d. metallicity.
Q36. arXiv:2001.08263 [astro-ph.GA]: X-CIGALE: fitting AGN/galaxy SEDs from X-ray to infrared. uang Yang (Texas A&M), et al., Submitted on 22 Jan 2020): ABSTRACT: CIGALE is a powerful multiwavelength spectral energy distribution (SED) fitting code for extragalactic studies. However, the current version of CIGALE is not able to fit X-ray data, which often provide unique insights into AGN intrinsic power. We develop a new X-ray module for CIGALE, allowing it to fit SEDs from the X-ray to infrared (IR). We also improve the AGN fitting of CIGALE from UV-to-IR wavelengths. We implement a modern clumpy two-phase torus model, SKIRTOR. To account for moderately extincted type 1 AGNs, we implement polar-dust extinction. We publicly release the source code (named X-CIGALE). We test X-CIGALE with X-ray detected AGNs in SDSS, COSMOS, and AKARI-NEP. The fitting quality (as indicated by reduced χ2) is good in general, indicating that X-CIGALE is capable of modelling the observed SED from X-ray to IR. We discuss constrainability and degeneracy of model parameters in the fitting of AKARI-NEP, for which excellent mid-IR photometric coverage is available. We also test fitting a sample of AKARI-NEP galaxies for which only X-ray upper limits are available from Chandra observations, and find that the upper limit can effectively constrain the AGN SED contribution for some systems. Finally, using X-CIGALE, we assess the ability of Athena to constrain the AGN activity in future extragalactic studies. INTRODUCTION. Supermassive black holes (BHs) commonly exist in the centers of massive galaxies. BHs grow their mass (MBH) by accreting local material. During this process, a significant amount of the gravitational energy of the accreted material is converted to radiation, and the system shines as an active galactic nucleus (AGN). The typical spectral energy distribution (SED) of AGNs covers a broad wavelength range, from X-ray to infrared (IR). Some of these photons are scattered to X-ray energies by the hot corona above the disk (i.e. inverse Compton scattering). Some of the UV/optical photons might also be absorbed by dust. The dust is thus heated and reemits the energy as infrared radiation. SUMMARY: We have developed a new X-ray module (§2.2). The module is mainly designed to connect the intrinsic X-ray emission with other
a. wavelengths b. properties c. SED d. AGN.
Q37. arXiv:2001.08325 [astro-ph.GA]: A population of dust-enshrouded objects orbiting the Galactic black hole. Anna Ciurlo, et al., (Submitted on 23 Jan 2020): ABSTRACT: The central 0.1 parsecs of the Milky Way host a supermassive black hole identified with the position of the radio and infrared source Sagittarius A*, a cluster of young, massive stars (the S stars) and various gaseous features. Recently, two unusual objects have been found to be closely orbiting Sagittarius A*: the so-called G sources, G1 and G2. These objects are unresolved (having a size of the order of 100 astronomical units, except at periapse, where the tidal interaction with the black hole stretches them along the orbit) and they show both thermal dust emission and line emission from ionized gas. G1 and G2 have generated attention because they appear to be tidally interacting with the supermassive Galactic black hole, possibly enhancing its accretion activity. No broad consensus has yet been reached concerning their nature: the G objects show the characteristics of gas and dust clouds but display the dynamical properties of stellar-mass objects. Here we report observations of four additional G objects, all lying within 0.04 parsecs of the black hole and forming a class that is probably unique to this environment. The widely varying orbits derived for the six G objects demonstrate that they were commonly but separately
a. enhanced b. evolved c. formed d. sighted.
Q38. arXiv:2001.10023 [astro-ph.GA]: Hot atmospheres of galaxies, groups, and clusters of galaxies. Norbert Werner, François Mernier. (Submitted on 27 Jan 2020): ABSTRACT: Most of the ordinary matter in the local Universe has not been converted into stars but resides in a largely unexplored diffuse, hot, X-ray emitting plasma. It pervades the gravitational potentials of massive galaxies, groups and clusters of galaxies, as well as the filaments of the cosmic web. The physics of this hot medium, such as its dynamics, thermodynamics and chemical composition can be studied using X-ray spectroscopy in great detail. Here, we present an overview of the basic properties and discuss the self similarity of the hot "atmospheres" permeating the gravitational halos from the scale of galaxies, through groups, to massive clusters. Hot atmospheres are stabilised by the activity of supermassive black holes and, in many ways, they are of key importance for the evolution of their host galaxies. The hot plasma has been significantly enriched in heavy elements by supernovae during the period of maximum star formation activity, probably more than 10 billion years ago. High resolution X-ray spectroscopy just started to be able to probe the dynamics of atmospheric gas and future space observatories will determine the properties of the currently unseen hot diffuse medium throughout the cosmic web. DETAILS: Composite optical and X-ray images show the hot, X-ray emitting atmospheres pervading the massive galaxy cluster Abell 1689 and the massive elliptical galaxy NGC 5813 in the centre of a group. Courtesy:NASA/CXC/SAO. Most of the matter in the Universe remains unseen. In the inner most parts of galaxies the hot,strongly ionised, X-ray emitting plasma is often referred to as interstellar medium (ISM) and at large radii, well beyond the stellar component, as circumgalactic medium (CGM), in groups of galaxies as intragroup medium (IGrM), in clusters of galaxies as intracluster medium (ICM), and in the filaments of the cosmic web as intergalactic medium (IGM) or warm hot intergalactic medium (WHIM). Since the hot phases of all these media share crucial similarities - e.g. they can be well described by equations of ideal gas in a gravitational potential-we will refer to them at all scales a shot atmospheres. CONCLUSIONS: Will finally enable us to build the Cosmic Web Explorer mission, which will survey the physical properties of most of the medium permeating the cosmic
a. sea b. ocean c. senario d. survey.
Q39. arXiv:2001.10135 [astro-ph.CO]: Tracing the high energy theory of gravity: an introduction to Palatini inflation. Tommi Tenkanen. Submitted on (28 Jan 2020): ABSTRACT: We present an introduction to cosmic inflation in the context of Palatini gravity, which is an interesting alternative to the usual metric theory of gravity. In the latter case only the metric gμν determines the geometry of space-time, whereas in the former case both the metric and the space-time connection Γλμν are a priori independent variables - a choice which can lead to a theory of gravity different from the metric one. In scenarios where the field(s) responsible for cosmic inflation are coupled non-minimally to gravity or the gravitational sector is otherwise extended, assumptions of the underlying gravitational degrees of freedom can have a big impact on the observational consequences of inflation. We demonstrate this explicitly by reviewing several interesting and well-motivated scenarios including Higgs inflation, R^2 inflation, and ξ -attractor models. We also discuss some prospects for future research and argue why r=10^−3 is a particularly important goal for future missions that search for signatures of primordial gravitational
a. waves b. repulsion c. attraction d. oscillations.
Q40. arXiv:2001.10404 [astro-ph.SR]:The Impact of Metallicity on the Evolution of Rotation and Magnetic Activity of Sun-Like Stars. L. Amard, S. P. Matt. (Submitted on 28 Jan 2020): ABSTRACT: The rotation rates and magnetic activity of Sun-like and low-mass (< 1.4 Msun) main-sequence stars are known to decline with time, and there now exist several models for the evolution of rotation and activity. However, the role that chemical composition plays during stellar spin-down has not yet been explored. In this work, we use a structural evolution code to compute the rotational evolution of stars with three different masses (0.7, 1.0, and 1.3)Msun and six different metallicities, ranging from [Fe/H]=-1.0 to [Fe/H]=+0.5. We also implement three different wind-braking formulations from the literature (two modern and one classical) and compare their predictions for rotational evolution. The effect that metallicity has on stellar structural properties, and in particular the convective turnover timescale, leads the two modern wind-braking formulations to predict a strong dependence of the torque on metallicity. Consequently, they predict that metal rich stars spin-down more effectively at late ages (> 1 Gyr) than metal poor stars, and the effect is large enough to be detectable with current observing facilities. For example, the formulations predict that a Sun-like (solar-mass and solar-aged) star with [Fe/H]=-0.3 will have a rotation period of less than 20 days. Even though old, metal poor stars are predicted to rotate more rapidly at a given age, they have larger Rossby numbers and are thus expected to have lower magnetic activity levels. Finally, the different wind-braking formulations predict quantitative differences in the metallicity-dependence of stellar rotation, which may be used to test
a. these b. rotation c. currents d. them,
Q41.arXiv:2001.10672 [astro-ph.SR]: Clues to the origin and properties of magnetic white dwarfs. dela Kawka. (Submitted on 29 Jan 2020): ABSTRACT: A significant fraction of white dwarfs possess a magnetic field with strengths ranging from a few kG up to about 1000 MG. However, the incidence of magnetism varies when the white dwarf population is broken down into different spectral types providing clues on the formation of magnetic fields in white dwarfs. Several scenarios for the origin of magnetic fields have been proposed from a fossil field origin to dynamo generation at various stages of evolution. Offset dipoles are often assumed sufficient to model the field structure, however time-resolved spectropolarimetric observations have revealed more complex structures such as magnetic spots or multipoles. Surface mapping of these field structures combined with measured rotation rates help distinguish scenarios involving single star evolution from other scenarios involving binary interactions. I describe key observational properties of magnetic white dwarfs such as age, mass, and field strength, and confront proposed formation scenarios with these
a. properties b. structures c. formations d. multipoles.
Q42. arXiv:2001.10690 [astro-ph.HE]: Merger rate density of binary black holes formed in open clusters. Jun Kumamoto, Michiko S. Fujii, Ataru Tanikawa. (Submitted on 29 Jan 2020): ABSTRACT: Several binary black holes (BBHs) have been observed using gravitational wave detectors. For the formation mechanism of BBHs, two main mechanisms, isolated binary evolution and dynamical formation in dense star clusters, have been suggested. Future observations are expected to provide more information about BBH distributions, and it will help us to distinguish the two formation mechanisms. For the star cluster channel, globular clusters have mainly been investigated. However, recent simulations have suggested that BBH formation in open clusters is not negligible. We estimate a local merger rate density of BBHs originated from open clusters using the results of our N-body simulations of open clusters with four different metallicities. We find that the merger rate per cluster is the highest for our 0.1 solar metallicity model. Assuming a cosmic star formation history and a metallicity evolution with dispersion, we estimate the local merger rate density of BBHs originated from open clusters to be ∼70 yr^−1 Gpc^−3. This value is comparable to the merger rate density expected from the first and second observation runs of LIGO and Virgo. In addition, we find that BBH mergers obtained from our simulations can reproduce the distribution of primary mass and mass ratio of merging BBHs estimated from the LIGO and Virgo
a. findings b. estimates c. observations. d. clusters.
Q43. arXiv:2001.10943 [astro-ph.CO]: How dark are filaments in the cosmic web? Tianyi Yang, Michael J. Hudson, Niayesh Afshordi. (Submitted on 29 Jan 2020): ABSTRACT: The cold dark matter model predicts that dark matter haloes are connected by filaments. Direct measurements of the masses and structure of these filaments are difficult, but recently several studies have detected these dark-matter-dominated filaments using weak lensing. Here we study the efficiency of galaxy formation within the filaments by measuring their total mass-to-light ratios and stellar mass fractions. Specifically, we stack pairs of Luminous Red Galaxies (LRGs) with a typical separation on the sky of 8h^−1 Mpc. We stack background galaxy shapes around pairs to obtain mass maps through weak lensing, and we stack galaxies from the Sloan Digital Sky Survey (SDSS) to obtain maps of light and stellar mass. To isolate the signal from the filament, we construct two matched catalogues of physical and non-physical (projected) LRG pairs, with the same distributions of redshift and separation. We then subtract the two stacked maps. Using LRG pair samples from the BOSS survey at two different redshifts, we find that the evolution of the mass in filament is consistent with the predictions from perturbation theory. The filaments are not entirely dark: their mass-to-light ratios (M/L=351±87 in solar units in the r-band) and stellar mass fractions (Mstellar/M=0.0073±0.0020) are consistent with the cosmic (and with their redshift evolutions).
a. data b. values c. evolutions d. redshifts.
Q44.arXiv:2001.11042 [astro-ph.EP]: Pebble drift and planetesimal formation in protoplanetary discs with embedded planets. Linn E.J. Eriksson, Anders Johansen, Beibei Liu. (Submitted on 29 Jan 2020):ABSTRACT: Nearly-axisymmetric gaps and rings are commonly observed in protoplanetary discs. The leading theory regarding the origin of these patterns is that they are due to dust trapping at the edges of gas gaps induced by the gravitational torques from embedded planets. If the concentration of solids at the gap edges becomes high enough, it could potentially result in planetesimal formation by the streaming instability. We test this hypothesis by performing global 1-D simulations of dust evolution and planetesimal formation in a protoplanetary disc that is perturbed by multiple planets. We explore different combinations of particle sizes, disc parameters, and planetary masses, and find that planetesimals form in all these cases. We also compare the spatial distribution of pebbles from our simulations with protoplanetary disc observations. Planets larger than one pebble isolation mass catch drifting pebbles efficiently at the edge of their gas gaps, and depending on the efficiency of planetesimal formation at the gap edges, the protoplanetary disc transforms within a few 100,000 years to either a transition disc with a large inner hole devoid of dust or to a disc with narrow bright rings. For simulations with planetary masses lower than the pebble isolation mass, the outcome is a disc with a series of weak ring patterns but no strong depletion between the rings. Lowering the pebble size artificially to 100 micrometer-sized "silt", we find that regions between planets get depleted of their pebble mass on a longer time-scale of up to 0.5 million years. These simulations also produce fewer planetesimals than in the nominal model with millimeter-sized particles and always have at least two rings of pebbles still visible after
a. 10 Myr b. 20 Myr c. 1 Myr d. 100 Myr.
Q45. arXiv:2001.11105 [astro-ph.GA]: Exploring the dispersion measure of the Milky Way halo. Laura C. Keating, Ue-Li Pen. (Submitted on 29 Jan 2020):ABSTRACT: Fast radio bursts offer the opportunity to place new constraints on the mass and density profile of hot and ionized gas in galactic haloes. We test here the X-ray emission and dispersion measure predicted by different gas profiles for the halo of the Milky Way. We examine a range of models, including entropy stability conditions and external pressure continuity. We find that incorporating constraints from X-ray observations leads to favouring dispersion measures on the lower end of the range given by these models. We show that the dispersion measure of the Milky Way halo could be less than 10 cm^−3 pc in the most extreme model we consider, which is based on constraints from O VII absorption lines. However, the models allowed by the soft X-ray constraints span more than an order of magnitude in dispersion measures. Additional information on the distribution of gas in the Milky Way halo could be obtained from the signature of a dipole in the dispersion measure of fast radio bursts across the sky, but this will be a small effect for most
a. cases b. constraints c. sky d. halos.
Q46. arXiv:2001.11319 [astro-ph.SR]: Spectroscopic orbits of three dwarf barium stars. P. L. North et al., (Submitted on 30 Jan 2020):ABSTRACT: Barium stars are thought to result from binary evolution in systems wide enough to allow the more massive component to reach the asymptotic giant branch and eventually become a CO white dwarf. While Ba stars were initially known only among giant or subgiant stars, some were subsequently discovered also on the main sequence (and known as dwarf Ba stars). We provide here the orbital parameters of three dwarf Ba stars, completing the sample of 27 orbits published recently by Escorza et al. with these three southern targets. We show that these new orbital parameters are consistent with those of other dwarf Ba
a. Nuclei b. masses c. components d. stars.
Q47.arXiv:2001.11329 [physics.app-ph]: Vanadium oxide thin films and fibers obtained by acetylacetonate sol-gel method. Olga Berezina, et al., (Submitted on 8 Jan 2020):ABSTRACT: Vanadium oxide films and fibers have been fabricated by the acetylacetonate sol-gel method followed by annealing in wet nitrogen. The samples are characterized by X-ray diffraction and electrical conductivity measurements. The effects of a sol aging, the precursor decomposition and the gas atmosphere composition on the annealing process, structure and properties of the films are discussed. The two-stage temperature regime of annealing of amorphous films in wet nitrogen for formation of the well crystallized VO2 phase is chosen: 1) 25-550 C and 2) 550-600 C. The obtained films demonstrate the metal-insulator transition and electrical switching. Also, the effect of the polyvinylpyrrolidone additive concentration and electrospinning parameters on qualitative (absence of defects and gel drops) and quantitative (length and diameter) characteristics of vanadium oxide fibers is studied. RESULTS:It should be admitted that the required thermal treatment temperature, of up to 600C, is apparently rather high which would seem to eliminate such a major merit of the LPD technique as a low temperature processing temperature. Note however that even a relatively low content of the VO2 phase would be enough to fabricate switching devices, since VO2 channels are always formed during the process of
a. EFC b. EF c. EFD d. FE.
Q48.arXiv:2001.11238 [physics.app-ph]: Inverse design of higher-order photonic topological insulators. Yafeng Chen, Fei Meng, Yuri Kivshar, Baohua Jia, Xiaodong Huang. (Submitted on 30 Jan 2020):ABSTRACT: Topological photonics revolutionizes some of the traditional approaches to light propagation and manipulation, and it provides unprecedented means for developing novel photonic devices. Recently discovered higher-order topological phases go beyond the conventional bulk-edge correspondence for photonic crystals and introduce novel opportunities for topological protection. Here, we introduce an intelligent numerical approach for inverse design of higher-order photonic topological insulators with great flexibility for controlling both topological edge and topological corner states. In particular, we consider the second-order photonic topological insulator and design several structures supporting both edge and corner states at different frequencies. By carefully programming these structures, we suggest a novel approach for topological routing of the edge and corner states by changing the operational frequency. Our finding paves the way to integrated topological photonic devices with novel functionalities. RESULT:We have proposed an intelligent numerical method for inverse design of higher-order photonic topological insulators. For the second-order topological insulators, the optimized structures support a nearly flat edge state and highly localized corner states, which may have the potential application in enhancing light-matter interaction. Rather than traditional states, which only support bonding corner states, the optimized topological states support both bonding and anti-bonding corner states. In particular, by inversely designing several types of topological structures with different frequencies for both edge and corner states and purposely programming their properties, we have realized routing topological edge and corner states with different frequencies. Our findings provide great flexibilities for utilizing topological edge and corner states, which is important for developing photonic devices with novel
a.functionalities b. frequencies c interactions d. corner states.
Q49.arXiv:2001.11345 [physics.gen-ph]: Negative Energy States in Quantum Theory. Anastasios Y. Papaioannou. (Submitted on 21 Jan 2020): ABSTRACT: We analyze the Lagrangian density and canonical stress-energy tensor for the Dirac equation, where the Dirac bispinor has been recast as a multivector set of fields. For the massless Dirac field, the sign of the energy density is determined by the relative phase of uncoupled even- and odd-grade field components. These components become coupled in the massive Dirac equation, and the sign of the energy is determined by their spatial parity. The corresponding stress-energy tensors for the second-order equations also admit negative energy states, with the sign of the energy density again dependent on field parity. We apply the same multivector approach to electromagnetism, constructing new Lagrangian and energy densities in which the vector potential and the electromagnetic field are treated as independent field degrees of
a. lagrangian b. EM field c. freedom d. energy density.
Q50. arXiv:2001.11448 [physics.ins-det]: Imaging by muons and their induced secondary particles -- a novel technique. G. Galgóczi, D. Mrdja, I. Bikit, K. Bikit, J. Slivka, J. Hansman, L. Oláh, G. Hamar, D. Varga. (Submitted on 30 Jan 2020): ABSTRACT: Muography is a well estabilished method to obtain 3D images of large objects (e.g. volcanoes and large buildings) without any additional particle source, taking advantage of the presence of cosmic muons. The underlying principle of muography is the measurement of individual muon tracks and the determination of their absorption or scattering. These processes depend on the material that they have travelled through. The novel method discussed is based on the measurement of the muon tracks and of the corresponding particles those were produced by the muons themselves in the investigated target. As muons pass through matter they interact with matter by ionization, bremsstrahlung, pair production and nuclear interactions. Our experimental setup is designed in a way to measure both the primary muons and the created secondaries (mostly electrons and gammas). The tracks of the muons are determined by a special kind of Multi-Wire Proportional Chambers (MWPC) called CCC (Close Cathode Chamber). The secondary particles produced in the target are measured by four plastic scintillators placed around the target. The CCC chambers and the scintillators are used in coincidence in order to gather data about muons those passed through the target. As cross sections of the described processes vary by the density and the atomic number of materials this technique could be used to investigate the material content of the target. RESULT: In the case of lead every fifth muon produces a gamma with more energy than 100 keV and for polystyrene only one from one thousand muon produce a gamma with at least 100 keV. It is interesting to mention that the number of gammas produced in low Z material are similar but the number of electrons is different. For water there is 25% more electrons produced than for
a. gammas b. Z material c. polystyrene d. muons.
Q51.arXiv:2001.11034 [cond-mat.mes-hall]: Observing Movement of Dirac Cones from Single-Photon Dynamics. Yong-Heng Lu, et al., Submitted on 29 Jan 2020): Graphene with honeycomb structure, being critically important in understanding physics of matter, exhibits exceptionally unusual half-integer quantum Hall effect and unconventional electronic spectrum with quantum relativistic phenomena. Particularly, graphene-like structure can be used for realizing topological insulator which inspires an intrinsic topological protection mechanism with strong immunity for maintaining coherence of quantum information. These various peculiar physics arise from the unique properties of Dirac cones which show high hole degeneracy, massless charge carriers and linear intersection of bands. Experimental observation of Dirac cones conventionally focuses on the energy-momentum space with bulk measurement. Recently, the wave function and band structure have been mapped into the real-space in photonic system, and made flexible control possible. Here, we demonstrate a direct observation of the movement of Dirac cones from single-photon dynamics in photonic graphene under different biaxial strains. Sharing the same spirit of wave-particle nature in quantum mechanics, we identify the movement of Dirac cones by dynamically detecting the edge modes and extracting the diffusing distance of the packets with accumulation and statistics on individual single-particle registrations. Our results of observing movement of Dirac cones from single-photon dynamics, together with the method of direct observation in real space by mapping the band structure defined in momentum space, pave the way to understand a variety of artificial structures in quantum regime. DETAILS: Applying the ‘tight binding approximation’ to the ‘photonic graphene’, the Hamiltonian can be described by HTB =(Sum over i,j to N)C i,j (a† i aj) + H.c. (1) where N is the total number of the waveguides and ci,j denotes the coupling constant between the nearest neighbor waveguides i and j. Furthermore, we note that the coupling constant ci,j concludes two parts: vertical coupling cv and diagonal coupling cd. RESULTS: With the successful experimental observation and validation here, it is of great interest to generalize our approach of dynamical observation to the other attractive models, including Lieb-lattices with localized states in the continuum, Kagome-breathing-lattices, fractal topological photonic quasicrystals, high dimensional system with disorder and defects. Along with manipulation of Dirac cones, edge modes coupling or decoupling from bulk modes, band gap enlarging and evolution of photons, our experimental approaches may provide new sight on using photonic systems to engineer the analogous effects for solving complex and hard problems in condensed matter. The elements of single-photon dynamics and their protection in the honeycomb lattices may inspire developing entirely new capacities of engineering quantum states in the different artificial structures, especially topological-protected
a. quanta b. mechanics c. continuum d. systems.
Q52.arXiv:2001.11418 [astro-ph.GA]: he Nature of the Double Nuclei in the Barred S0 Galaxy IC 676. Zhimin Zhou, Jun Ma, Xu Zhou, Hong Wu. (Submitted on 30 Jan 2020 (v1), last revised 31 Jan 2020 (this version, v2)):ABSTRACT: The lenticular galaxy IC 676 is a barred galaxy with double nuclei and active star formation in the central region. In this work we present the long-slit spectroscopy and archival multi-wavelength images to investigate the nature and origin of the double nuclei in IC 676. Through photometric 1D brightness profiles and 2D image decomposition, we show that this galaxy consists of a stellar bar with the length of ∼2.5 kpc and two Sérsic disks both of which with Sérsic index n∼1.3. There is probably little or no bulge component assembled in IC 676. The luminosities of the double nuclei are primarily dominated by young stellar populations within the ages of 1-10 Myr. The northern nucleus has stronger star formation activity than the southern one. The surface densities of the star formation rate in the double nuclei are similar to those in starburst galaxies or the circumnuclear star forming regions in spiral galaxies. Each of the double nuclei in IC 676 likely consists of young massive star clusters, which can be resolved as bright knots in the HST high resolution image. Our results suggest that IC 676 likely has a complex formation and evolutionary history. The secular processes driven by the stellar bar and external accretion may dominate the formation and evolution of its double nuclei. This indicates that the secular evolution involving the internal and external drivers may have an important contribution for the evolution of lenticular
a. Galaxies b. stellats c. knots d. history.
Q53.arXiv:2002.01476 [astro-ph.EP]: Observational Signatures of Sub-Relativistic Meteors. Amir Siraj, Abraham Loeb. (Submitted on 4 Feb 2020): ABSTRACT: It is currently unknown whether solid particles larger than dust from supernova ejecta rain down on Earth at high speeds. We develop a hydrodynamic and radiative model to explore the detectability of ≳1mm sub-relativistic meteors. We find that a large fraction of the meteor energy during its passage through the Earth's upper atmosphere powers the adiabatic expansion of a hot plasma cylinder, giving rise to acoustic shocks detectable by infrasound microphones. Additionally, a global network of several hundred all-sky optical cameras with a time resolution of ≲ 10^-4 s would be capable of detecting 1mm sub-relativistic meteors. DETAILS: Empirical evidence indicates that at least one nearby supernovae resulted in the 60Fe and other radionuclides detected in deep-ocean samples. Hayakawa in 1972 proposed that dust grains may be a source of the phenomenology attributed to particle showers of ultrahigh energy cosmic rays (UHECRs). Processes affecting the origin and survival of relativistic dust have been extensively studied. RESULTS: We apply our approach to meteors with radii r = 1 mm, 1 cm, and 10 mm, traveling at β = 0.1, as a fiducial example. Since sub-relativistic ~1 cm meteors should radiate ~ 2% (10^18 erg) of their kinetic energy, such a flash would be approximately an order of magnitude more energetic than the least energetic fireballs reported in the US Government’s CNEOS database. If the time resolution of sensors the CNEOS network is . 10^−4 s, then CNEOS could provide an optimal dataset in which to search for sub-relativistic r ~ 1 cm meteors. Finally, we note that if gram-scale relativistic spacecraft such as the proposed Breakthrough Starshot project arrive to Earth from other civilizations and come into contact with the Earth’s atmosphere, they would appear as sub-relativistic ~ 1 cm
a. meteor b. starshots c. meteors d. fireballs.
Q54.arXiv:2002.01487 [astro-ph.CO]: Probing alternative cosmologies through the inverse distance ladder. nfred Lindner, Kevin Max, Moritz Platscher, Jonas Rezacek. (Submitted on 4 Feb 2020): ABSTRACT: We study the implications of a combined analysis of cosmic standard candles and standard rulers on the viability of cosmological models beyond the cosmological concordance model. To this end, we employ data in the form of the joint light-curve analysis supernova compilation, baryon acoustic oscillations, cosmic microwave background data, and a recently proposed set of Quasars as objects of known brightness. The advantage of including the latter is that they extend the local distance measures to redshifts which have previously been out of reach and we investigate how this allows one to test cosmologies beyond ΛCDM. We focus on two particular modifications: One is the theory of a massive tensor field interacting with the standard metric of gravity, so-called bigravity, and the other conformal gravity, a theory of gravity that has no knowledge of fundamental length scales. The former of the two constitutes a veritable extension of General Relativity, given that it adds to the metric tensor of gravity a second dynamical tensor field. The resulting dynamics have been proposed as a self-accelerating cosmology. Conformal gravity on the other hand is a much more drastic change of the underlying gravitational theory. Its ignorance towards fundamental length scales offers a completely different approach to late time acceleration and the so-called cosmological constant problem. In this sense, both models offer - in one way or another - an explanation for the cosmological constant problem. We perform a combined cosmological fit which provides strong constraints on some of these extensions, while some alternative cosmologies are in fact favoured by the data. We also briefly comment on the implications of the long-standing H0-tension.
a. tension b. H0-tension c. cosmology d. constant.
Q55. arXiv:2002.01796 [astro-ph.HE]: Axion and dark photon limits from Crab Nebula high energy gamma-rays. Xiao-Jun Bi, Yu Gao, Junguang Guo, Nick Houston, Tianjun Li, Fangzhou Xu, Xin Zhang. (Submitted on 5 Feb 2020): ABSTRACT: The observation of cosmic sub-PeV gamma-rays from the Crab Nebula opens up the possibility of testing cosmic ray photon transparency at the multi-hundred TeV scale. Assuming no deviation from a source gamma-ray emission due to accelerated electron inverse-Compton scattering, higher event energies can extend constraints on the effects of new physics; We consider oscillation between gamma-rays and axions/dark photons, plus attenuation effects from gamma-ray absorption in the case of dark photon dark matter. Combining the recent AS γ and HAWC sub-PeV data with earlier MAGIC and HEGRA data, axion-like particles are most constrained in the 10^−7−10^−6 eV mass range, where the coupling g aγ is constrained to be below 1.8×10 ^−10 GeV^ −1. In comparison, gamma ray flux attenuation due to oscillation with a dark photon leads to a very weak constraint on the mixing parameter; ϵ≲0.2 for dark photon mass between 10^−7 and 10^−6 eV. Direct scattering from dark photon dark matter limits ϵ≲ 0.01 for masses between 6 and 400
a. PeV b. DeV c. MeV d. eV.
Q56. arXiv:2002.02464 [astro-ph.CO]: Cosmology with quasars: predictions for eROSITA from a quasar Hubble diagram. Elisabeta Lusso (UniFI/INAF-Arcetri). (Submitted on 6 Feb 2020): ABSTRACT: Our group has developed a technique that makes use of the observed non-linear relation between the ultraviolet and the X-ray luminosity in quasars to provide an independent measurement of their distances, thus turning quasars into standardizable candles. This technique, at present, it is mostly based upon quasar samples with data from public catalogues both in the X-rays and in the optical/ultraviolet and extends the Hubble diagram of supernovae to a redshift range still poorly explored (z>2). From the X-ray perspective, we are now on the eve of a major change, as the upcoming mission eROSITA is going to provide us with up to ~3 millions of active galactic nuclei across the entire sky. Here we present predictions for constraining cosmological parameters such as the amount of dark matter (Ωm), dark energy (ΩΛ) and the evolution of the equation of state of dark energy (w) through the Hubble diagram of quasars, based on the 4-year eROSITA all-sky survey. Our simulations show that the eROSITA quasars, complemented by redshift and broad-band photometric information, will supply the largest quasar sample at z<2, but with very few objects available for cosmology at higher redshifts that survives the cut for the Malmquist bias, as eROSITA will sample the brighter end of the X-ray luminosity function. The power of the quasar Hubble diagram for precision cosmology lies in the high-redshift regime, where quasars can be observed up to redshift ~7.5, essential to discriminate amongst different model extrapolations. Therefore, to be competitive for cosmology, the eROSITA quasar Hubble diagram must be complemented with the already available quasar samples and dedicated (deep) large programmes at redshift
a. z>4 b. z>3 c. z>2 d. z>1.
Q57. arXiv:2002.02469 [astro-ph.GA]: Prevalence of Complex Organic Molecules in Starless and Prestellar Cores within the Taurus Molecular Cloud. Samantha Scibelli, Yancy Shirley. (Submitted on 6 Feb 2020): ABSTRACT: The detection of complex organic molecules (COMs) toward dense, collapsing prestellar cores has sparked interest in the fields of astrochemistry and astrobiology, yet the mechanisms for COM formation are still debated. It was originally believed that COMs initially form in ices which are then irradiated by UV radiation from the surrounding interstellar radiation field as well as forming protostars and subsequently photodesorbed into the gas-phase. However, starless and prestellar cores do not have internal protostars to heat-up and sublimate the ices. Alternative models using chemical energy have been developed to explain the desorption of COMs, yet in order to test these models robust measurements of COM abundances are needed toward representative samples of cores. We've conducted a large-sample survey of 31 starless and prestellar cores in the Taurus Molecular Cloud, detecting methanol (CH3OH) in 100% of the cores targeted and acetaldehyde (CH3CHO) in 70%. At least two transition lines of each molecule were measured, allowing us to place tight constraints on excitation temperature, column density and abundance. Additional mapping of methanol revealed extended emission, detected down to AV as low as ∼3 mag. We find complex organic molecules are detectable in the gas-phase and are being formed early, at least hundreds of thousands of years prior to star and planet formation. The precursor molecule, CH3OH, may be chemically linked to the more complex CH3CHO, however higher spatial resolution maps are needed to further test chemical
a. models b. temperature c. gas-phase d. excitation.
Q58.arXiv:2002.02499 [astro-ph.SR]: Optical/near-infrared observations of the Fried Egg Nebula: Multiple shell ejections on a 100 yr timescale from a massive yellow hypergiant. E. Koumpia, et al., (Submitted on 6 Feb 2020): ABSTRACT: Context. The fate of a massive star during the latest stages of its evolution is highly dependent on its mass-loss rate/geometry and therefore knowing the geometry of the circumstellar material close to the star and its surroundings is crucial. Aims. We aim to study the nature (i.e. geometry, rates) of mass-loss episodes. In this context, yellow hypergiants are great targets. Methods. We analyse a large set of optical/near-infrared data, in spectroscopic and photometric (X-shooter/VLT), spectropolarimetric (ISIS/WHT), and interferometric GRAVITY-AMBER/VLTI) modes, toward the yellow hypergiant IRAS 17163-3907. We present the first model-independent reconstructed images of IRAS 17163-3907 at these wavelengths at milli-arcsecond scales. Lastly, we apply a 2D radiative transfer model to fit the dereddened photometry and the radial profiles of published VISIR images at 8.59 {\mu}m, 11.85 {\mu}m and 12.81 {\mu}m simultaneously, adopting the revised Gaia distance (DR2). Results. The interferometric observables around 2 {\mu}m show that the Br{\gamma} emission is more extended and asymmetric than the Na i and the continuum emission. In addition to the two known shells surrounding IRAS 17163-3907 we report on the existence of a third hot inner shell with a maximum dynamical age of only 30 yr. Conclusions. The interpretation of the presence of Na i emission at closer distances to the star compared to Br{\gamma} has been a challenge in various studies. We argue that the presence of a pseudo photosphere is not needed, but it is rather an optical depth effect. The three observed distinct mass-loss episodes are characterised by different mass-loss rates and can inform the theories on mass-loss mechanisms, which is a topic still under debate. We discuss these in the context of photospheric pulsations and wind bi-stability
a. criteria b. conclusions c. mechanisms d. processes.
Q59.arXiv:2002.02505 [physics.chem-ph]: Relativistic coupled-cluster study of BaF in search of CP violation. Kaushik Talukdar, Malaya K. Nayak, Nayana Vaval, Sourav Pal. (Submitted on 6 Feb 2020): ABSTRACT: BaF is one of the potential candidates for the experimental search of the electric dipole moment of the electron (eEDM). The NL-eEDM collaboration is building a new experimental set up to measure the eEDM using the BaF molecule [The NL-eEDM collaboration, Eur. Phys. J. D (2018) 72: 197]. To analyze the results of such an experiment, one would require the accurate value of the molecular P,T-odd interaction parameters that cannot be measured from any experiment. In this work, we report the precise value of the P,T-odd interaction parameters of the BaF molecule obtained from the four-component relativistic coupled-cluster calculations. We also calculate the hyperfine structure (HFS) constants of the same molecule to assess the reliability of the reported molecular parameters. The calculated HFS constants show good agreement with the available experimental values. Further, the systematic effects of electron-correlation along with the roles of inner-core electrons and the virtual energy functions in the calculation of the studied properties of BaF are
a. simulated b. gauged c. calculated d. investigated.
Q60. arXiv:2002.02774 [physics.app-ph]: Assessment of GaPSb/Si tandem material association properties for photoelectrochemical cells. Lipin Chen,et al., (Submitted on 7 Feb 2020): ABSTRACT: Here, the structural, electronic and optical properties of the GaP1-xSbx/Si tandem materials association are determined in view of its use for solar water splitting applications. The GaPSb crystalline layer is grown on Si by Molecular Beam Epitaxy with different Sb contents. The bandgap value and bandgap type of GaPSb alloy are determined on the whole Sb range, by combining experimental absorption measurements with tight binding (TB) theoretical calculations. The indirect (X-band) to direct ({\Gamma}-band) cross-over is found to occur at 30% Sb content. Especially, at a Sb content of 32%, the GaP1-xSbx alloy reaches the desired 1.7eV direct bandgap, enabling efficient sunlight absorption, that can be ideally combined with the Si 1.1 eV bandgap. Moreover, the band alignment of GaP1-xSbx alloys and Si with respect to water redox potential levels has been analyzed, which shows the GaPSb/Si association is an interesting combination both for the hydrogen evolution and oxygen evolution reactions. These results open new routes for the development of III-V/Si low-cost high-efficiency photoelectrochemical
a. data b. cells c. units d. bandgaps.
Answers: Q1a. Q2b. Q3d. Q4b. Q5c. Q6b. Q7a. Q8c. Q9d. Q10b. Q11c. Q12b. Q13b. Q14c. Q15a. Q16c. Q17b. Q18d. Q19a. Q20d. Q21c. Q22a. Q23d. Q24b. Q25c. Q26a. Q27d. Q28c. Q29b. Q30a. Q31c. Q32a. Q33b. Q34d. Q35b. Q36a. Q37c. Q38b. Q39a. Q40d. Q41a. Q42c. Q43b. Q44c. Q45a. Q46d. Q47b. Q48a. Q49c. Q50c. Q51b. Q52a. Q53c. Q54b. Q55d. Q56b. Q57a. Q58c. Q59d. Q60b.
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