arXiv: Astrophysics of Galaxies最新文献

{"title":"A warm molecular ring in AG Car: composing the mass-loss puzzle","authors":"C. Bordiu, F. Bufano, L. Cerrigone, G. Umana, J. Rizzo, C. Buemi, P. Leto, F. Cavallaro, A. Ingallinera, S. Loru, C. Trigilio, S. Riggi","doi":"10.1093/mnras/staa3606","DOIUrl":"https://doi.org/10.1093/mnras/staa3606","url":null,"abstract":"We present APEX observations of CO J=3-2 and ALMA observations of CO J=2-1, 13CO J=2-1 and continuum toward the galactic luminous blue variable AG Car. These new observations reveal the presence of a ring-like molecular structure surrounding the star. Morphology and kinematics of the gas are consistent with a slowly expanding torus located near the equatorial plane of AG Car. Using non-LTE line modelling, we derived the physical parameters of the gas, which is warm (50 K) and moderately dense (10$^3$ cm$^{-3}$. The total mass of molecular gas in the ring is 2.7$pm$0.9 solar masses. We analysed the radio continuum map, which depicts a point-like source surrounded by a shallow nebula. From the flux of the point-like source, we derived a current mass-loss date of $1.55pm0.21times10^{-5}$ solar masses / yr. Finally, to better understand the complex circumstellar environment of AG Car, we put the newly detected ring in relation to the main nebula of dust and ionised gas. We discuss possible formation scenarios for the ring, namely, the accumulation of interstellar material due to the action of the stellar wind, the remnant of a close binary interaction or merger, and an equatorially enhanced mass-loss episode. If molecular gas formed in situ as a result of a mass eruption, it would account for at least a 30$%$ of the total mass ejected by AG Car. This detection adds a new piece to the puzzle of the complex mass-loss history of AG Car, providing new clues about the interplay between LBV stars and their surroundings.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85824538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Further evidence to support a tidal disruption event in the changing-look AGN SDSS J0159","authors":"XueGuang Zhang","doi":"10.1093/mnrasl/slaa184","DOIUrl":"https://doi.org/10.1093/mnrasl/slaa184","url":null,"abstract":"In this Letter, we report further evidence to support a tidal disruption event (TDE) in the known changing-look AGN SDSS J0159, through the unique variabilities of asymmetric broad H$alpha$: broader but redder in 2010 than in 2000. Accepted the broad H$alpha$ emission regions tightly related to accreting debris in a central TDE, the well-known relativistic accretion disk origination can be applied to well explain the asymmetric broad H$alpha$ variabilities in SDSS J0159. Moreover, the model determined broad H$alpha$ emission regions have the sizes not follow the empirical R-L relation valid in normal broad line AGN, but have locations basically similar to the regions of accreting debris from a central TDE in SDSS J0159, indicating tight connections between the broad H$alpha$ emission materials and central TDE debris. Therefore, explanations of the asymmetric broad H$alpha$ variabilities through the relativistic accretion disk origination provide further clues to support a central TDE in SDSS J0159.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90049288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simulated X‐ray emission in galaxy clusters with feedback from active galactic nuclei","authors":"R. K. Chowdhury, Soumya S. Roy, S. Chatterjee, N. Khandai, C. Sarazin, T. Matteo","doi":"10.1002/ASNA.202113898","DOIUrl":"https://doi.org/10.1002/ASNA.202113898","url":null,"abstract":"To investigate the effect of feedback from active galactic nuclei (AGN) on their surrounding medium, we study the diffuse X-ray emission from galaxy groups and clusters by coupling the Astrophysical Plasma Emission Code (APEC) with the cosmological hydrodynamic simulation involving AGN feedback. We construct a statistical sample of synthetic Chandra X-ray photon maps to observationally characterize the effect of AGN on the ambient medium. We show that AGN are effective in displacing the hot X-ray emitting gas from the centers of groups and clusters, and that these signatures remain evident in observations of the X-ray surface brightness profiles.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87915742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Star formation history of the solar neighbourhood as told by Gaia","authors":"J. A. Alzate, G. Bruzual, D. J. Díaz-González","doi":"10.1093/mnras/staa3576","DOIUrl":"https://doi.org/10.1093/mnras/staa3576","url":null,"abstract":"The Gaia DR2 catalog is the best source of stellar astrometric and photometric data available today. The history of the Milky Way galaxy is written in stone in this data set. Parallaxes and photometry tell us where the stars are today, when were they formed, and with what chemical content, i.e. their star formation history (SFH). We develop a Bayesian hierarchical model suited to reconstruct the SFH of a resolved stellar population. We study the stars brighter than $G,=,15$ within 100 pc of the Sun in Gaia DR2 and derive a SFH of the solar neighbourhood in agreement with previous determinations and improving upon them because we detect chemical enrichment. Our results show a maximum of star formation activity about 10 Gyr ago, producing large numbers of stars with slightly below solar metallicity (Z=0.014), followed by a decrease in star formation up to a minimum level occurring around 8 Gyr ago. After a quiet period, star formation rises to a maximum at about 5 Gyr ago, forming stars of solar metallicity (Z=0.017). Finally, star formation has been decreasing until the present, forming stars of Z=0.03 at a residual level. We test the effects introduced in the inferred SFH by ignoring the presence of unresolved binary stars in the sample, reducing the apparent limiting magnitude, and modifying the stellar initial mass function.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75268446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fast rotating and low-turbulence discs at z ≃ 4.5: Dynamical evidence of their evolution into local early-type galaxies","authors":"F. Fraternali, A. Karim, B. Magnelli, C. Gómez-Guijarro, E. F. Jim'enez-Andrade, A. Posses","doi":"10.1051/0004-6361/202039807","DOIUrl":"https://doi.org/10.1051/0004-6361/202039807","url":null,"abstract":"Massive starburst galaxies in the early Universe are estimated to have depletion times of $sim 100$ Myr and thus be able to convert their gas very quickly into stars, possibly leading to a rapid quenching of their star formation. For these reasons they are considered progenitors of massive early-type galaxies (ETGs). In this paper, we study two high-$z$ starbursts, AzTEC/C159 ($zsimeq 4.57$) and J1000+0234 ($zsimeq 4.54$), observed with ALMA in the ${rm [C},{rm II}{rm ]}$ emission line. These observations reveal two massive and regularly rotating gaseous discs. A 3D modelling of these discs returns rotation velocities of about $500, {rm km}, {rm s}^{-1} $ and gas velocity dispersions as low as $approx 20, {rm km}, {rm s}^{-1}$, at least in AzTEC/C159, leading to very high ratios between regular and random motion ($V/sigma lower.7exhbox{$;stackrel{textstyle>}{sim};$} 20$). The mass decompositions of the rotation curves show that both galaxies are highly baryon-dominated with gas masses of $approx 10^{11},{M}_{odot}$, which, for J1000+0234, is significantly higher than previous estimates. We show that these high-$z$ galaxies overlap with $z=0$ massive ETGs in the ETG-analogue of the Tully-Fisher relation once their gas is converted into stars. This provides a dynamical evidence of the connection between massive high-$z$ starbursts and ETGs, although the transformation mechanism from fast-rotating to nearly pressure-supported systems remains unclear.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79397889","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Origin of LAMOST J1109+7459","authors":"Nour Aldein Almusleh, Yazan Khrais, Ali Taani","doi":"10.52526/25792776-2020.67.2-267","DOIUrl":"https://doi.org/10.52526/25792776-2020.67.2-267","url":null,"abstract":"We report a comprehensive Chemo-dynamical analysis of LAMOST J1109+0754, a relatively bright (V = 12.8), extremely metal-poor ([Fe/H] = $-3.17$), and prograde ($J_phi$ and $V_phi$ $> 0$) star, with a strong textit{r}-process enhancement ([Eu/Fe] = $+$0.94 $pm$ 0.12, [Ba/Fe] = $-$0.52 $pm$ 0.15). 31 chemical abundances (from Lithium to Thorium) were derived. We suggest a possible progenitor with stellar mass of 13.4-29.5 M$_odot$. We argue that J1109+0754 is representative of the main textit{r}-process component due to the well agreement with the scaled-solar textit{r}-process component. We analyze the orbital history of this star in a {it time-varying Galactic potential}, based on a Milky-Way analogue model extracted from texttt{Illustris-TNG} simulations. Using this model, we carry out a statistical estimation of the phase-space coordinates of J1109+0754 at a young cosmic age. Collectively, the calculated motions, the derived chemistry, and the results from the cosmological simulations suggest that LAMOST J1109+0754 most likely formed in a low-mass dwarf galaxy, and belongs to the Galactic outer-halo population.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85401150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MOSAIC on the ELT: High-multiplex Spectroscopy to Unravel the Physics of Stars and Galaxies from the Dark Ages to the Present Day","authors":"F. Hammer, S. Morris, J. Cuby, L. Kaper, M. Steinmetz, J. Afonso, B. Barbuy, E. Bergin, A. Finogenov, J. Gallego, S. Kassin, C. Miller, G. Ostlin, L. Penterricci, D. Schaerer, B. Ziegler, F. Chemla, G. Dalton, F. D. Frondat, C. Evans, D. L. Mignant, M. Puech, M. Rodrigues, R. Sánchez-Janssen, S. Taburet, L. Tasca, Y. Yang, S. Zanchetta, K. Dohlen, M. Dubbeldam, K. E. Hadi, A. Janssen, A. Kelz, M. Larrieu, I. Lewis, M. Macintosh, T. Morris, R. Navarro, W. Seifert","doi":"10.18727/0722-6691/5220","DOIUrl":"https://doi.org/10.18727/0722-6691/5220","url":null,"abstract":"The powerful combination of the cutting-edge multi-object spectrograph MOSAIC with the world largest telescope, the ELT, will allow us to probe deeper into the Universe than was possible. MOSAIC is an extremely efficient instrument in providing spectra for the numerous faint sources in the Universe, including the very first galaxies and sources of cosmic reionization. MOSAIC has a high multiplex in the NIR and in the VIS, in addition to multi-Integral Field Units (Multi-IFUs) in NIR. As such it is perfectly suited to carry out an inventory of dark matter (from rotation curves) and baryons in the cool-warm gas phases in galactic haloes at z=3-4. MOSAIC will enable detailed maps of the intergalactic medium at z=3, the evolutionary history of dwarf galaxies during a Hubble time, the chemistry directly measured from stars up to several Mpc. Finally, it will measure all faint features seen in cluster gravitational lenses or in streams surrounding nearby galactic halos, providing MOSAIC to be a powerful instrument with an extremely large space of discoveries. The preliminary design of MOSAIC is expected to begin next year, and its level of readiness is already high, given the instrumental studies made by the team.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87034506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The GALAH+ survey: Third data release","authors":"S. Buder, Sanjib Sharma, J. Kos, A. Amarsi, T. Nordlander, K. Lind, S. Martell, M. Asplund, J. Bland-Hawthorn, A. Casey, G. D. De Silva, V. D’Orazi, K. Freeman, M. Hayden, G. Lewis, Jane Lin, K. Schlesinger, J. Simpson, D. Stello, D. Zucker, T. Zwitter, K. Beeson, T. Buck, L. Casagrande, Jake T. Clark, K. Čotar, G. D. Da Costa, R. de Grijs, D. Feuillet, J. Horner, P. Kafle, S. Khanna, C. Kobayashi, Fan Liu, B. Montet, G. Nandakumar, D. Nataf, M. Ness, L. Spina, T. Tepper-García, Yuan-Sen Ting(丁源森), G. Traven, R. Vogrinčič, R. Wittenmyer, R. Wyse, M. Žerjal","doi":"10.1093/mnras/stab1242","DOIUrl":"https://doi.org/10.1093/mnras/stab1242","url":null,"abstract":"The recent exponential increase in spectroscopic, astrometric & photometric data has highlighted the scientific opportunities afforded by obtaining an ensemble of chemical element abundances for stars with precision distance & orbit measurements. With this third data release of the Galactic Archaeology with HERMES (GALAH) survey, we publish 678 423 spectra for 588 571 mostly nearby stars (81.2% of stars lie within 2 kpc), observed with the HERMES spectrograph at the Anglo-Australian Telescope. This release (referred to as GALAH+ DR3) includes all observations from GALAH Phase 1 (bright, main, & faint survey, 70%), the K2-HERMES (17%) & TESS-HERMES (5%) surveys, as well as additional GALAH-related projects (8%) including the bulge & observations of more than 75 stellar clusters. We derive stellar parameters $T_text{eff}$, $log g$, [Fe/H], $v_text{mic}$, $v_text{broad}$ & $v_text{rad}$ using Spectroscopy Made Easy (SME) & 1D MARCS model atmospheres. We also derive abundance ratios [X/Fe] for 30 elements (11 of which based on non-LTE computations), that cover 5 nucleosynthetic pathways: Li, C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Mo, Ru, Ba, La, Ce, Nd, Sm, Eu. We describe our validations for accuracy & precision, flagging of peculiar stars or measurements & stress that all users should take these flags into account. Our catalogue comprises 65% dwarfs, 34% giants & 1% other/unclassified stars. Based on unflagged abundances & age, we find 62.5% young low-alpha stars, 8.8% young high-alpha stars, 26.9% old stars & 1.8% stars with [Fe/H] < -1. Based on kinematics, we find 4% halo stars. Value-Added-Catalogs for stellar ages, dynamics, $v_text{rad}$ & binary systems accompany this data release. Together they provide a high-dimensional data set to study the chemodynamic evolution of the local Milky Way, as we showcase with a few chemodynamic analyses.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91019431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"VLA ammonia observations of L1287","authors":"I. Sep'ulveda, R. Estalella, G. Anglada, R. López, A. Riera, G. Busquet, A. Palau, J. Torrelles, Luis F. Rodriguez","doi":"10.1051/0004-6361/202037895","DOIUrl":"https://doi.org/10.1051/0004-6361/202037895","url":null,"abstract":"The present work aims at studying the dense gas of the molecular cloud LDN 1287 (L1287), which harbors a double FU Ori system, an energetic molecular outflow and a still-forming cluster of deeply embedded low-mass, young stellar objects, showing a high level of fragmentation. We present optical Halpha and [SII], and VLA NH$_3$ (1,1) and (2,2) observations with an angular resolution of ~3.5''. The observed NH$_3$ spectra have been analyzed with the HfS tool, fitting simultaneously three different velocity components. The NH$_3$ emission from L1287 comes from four different structures: a core associated with RNO 1, a guitar-shaped core (the \"Guitar\") and two interlaced filaments (the Blue and Red Filaments) roughly centered towards the binary FU Ori system RNO 1B/C and its associated cluster. Regarding the Guitar Core, there are clear signatures of gas infall onto a central mass that has been estimated to be ~2.1 $M_odot$. Regarding the two filaments, they have radii ~0.03 pc, masses per unit length ~50 $M_odot$ pc$^{-1}$, and are near isothermal equilibrium. A central cavity, probably related with the outflow, and also traced by the Halpha and [SII] emission, is identified, with several young stellar objects near its inner walls. Both filaments show clear signs of perturbation by the high-velocity gas of the outflows driven by one or several young stellar objects of the cluster. The Blue and Red filaments are coherent in velocity and have nearly subsonic gas motions, except at the position of the embedded sources. Velocity gradients across the Blue Filament can be interpreted either as infalling material onto the filament or rotation. Velocity gradients along the filaments are interpreted as infall motions towards a gravitational well at the intersection of both filaments.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80209950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-accuracy estimation of magnetic field strength in the interstellar medium from dust polarization","authors":"R. Skalidis, K. Tassis","doi":"10.1051/0004-6361/202039779","DOIUrl":"https://doi.org/10.1051/0004-6361/202039779","url":null,"abstract":"Dust polarization is a powerful tool for studying the magnetic field properties in the interstellar medium (ISM). However, it does not provide a direct measurement of its strength. Different methods havebeen developed which employ both polarization and spectroscopic data in order to infer the field strength. The most widely applied methods have been developed by Davis (1951), Chandrasekhar & Fermi (1953) (DCF), Hildebrand et al. (2009) and Houde et al.(2009) (HH09). They rely on the assumption that isotropic turbulent motions initiate the propagation of Alvfen waves. Observations,however, indicate that turbulence in the ISM is anisotropic and non-Alfvenic (compressible) modes may be important. Our goal is to develop a new method for estimating the field strength in the ISM, which includes the compressible modes and does not contradict the anisotropic properties of turbulence. We use simple energetics arguments that take into account the compressible modes to estimate the strength of the magnetic field. We derive the following equation: $B_{0}=sqrt{2 pirho} delta v /sqrt{delta theta}$, where $rho$ is the gas density, $delta v$ is the rms velocity as derived from the spread of emission lines, and $delta theta$ is the dispersion of polarization angles. We produce synthetic observations from 3D MHD simulationsand we assess the accuracy of our method by comparing the true field strength with the estimates derived from our equation. We find a mean relative deviation of $17 %$. The accuracy of our method does not depend on the turbulence properties of the simulated model. In contrast DCF and HH09 systematically overestimate the field strength. HH09 produces accurate results only for simulations with high sonic Mach numbers.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83541420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}