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by R. Buta; K. Sheth; E. Athanassoula; A. Bosma; J. Knapen; E. Laurikainen; H. Salo; D. Elmegreen; L. Ho; D. Zaritsky; H. Courtois; J. Hinz; J-C. Muñoz-Mateos; T. Kim; M. Regan; D. Gadotti; A. Gil de Paz; J. Laine; K. Menendez-Delmestre; Sebastien Comeron; S. Erroz Ferrer; M. Seibert; T. Mizusawa; B. Holwerda; B. Madore
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The Spitzer Survey of Stellar Structure in Galaxies (S4G) is the largest available database of deep, homogeneous middle-infrared (mid-IR) images of galaxies of all types. The survey, which includes 2352 nearby galaxies, reveals galaxy morphology only minimally affected by interstellar extinction. This paper presents an atlas and classifications of S4G galaxies in the Comprehensive de Vaucouleurs revised Hubble-Sandage (CVRHS) system. The CVRHS system follows the precepts of classical de...
Topics: Astrophysics of Galaxies, Astrophysics, Cosmology and Nongalactic Astrophysics, Astrophysics
Source: http://arxiv.org/abs/1501.00454
Arxiv.org
by F. de Gasperin; G. A. Ogrean; R. J. van Weeren; W. A. Dawson; M. Brüggen; A. Bonafede; A. Simionescu
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Extended steep-spectrum radio emission in a galaxy cluster is usually associated with a recent merger. However, given the complex scenario of galaxy cluster mergers, many of the discovered sources hardly fit into the strict boundaries of a precise taxonomy. This is especially true for radio phoenixes that do not have very well defined observational criteria. Radio phoenixes are aged radio galaxy lobes whose emission is reactivated by compression or other mechanisms. Here, we present the...
Topics: Astrophysics of Galaxies, Astrophysics, Cosmology and Nongalactic Astrophysics, Astrophysics
Source: http://arxiv.org/abs/1501.00043
Arxiv.org
by A. Popping; M. Meyer; L. Staveley-Smith; D. Obreschkow; G. I. Jozsa; D. J. Pisano
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The interaction of galaxies with their environment, the Intergalactic Medium (IGM), is an important aspect of galaxy formation. One of the most fundamental, but unanswered questions in the evolution of galaxies is how gas circulates in and around galaxies and how it enters the galaxies to support star formation. We have several lines of evidence that the observed evolution of star formation requires gas accretion from the IGM at all times and on all cosmic scales. This gas remains largely...
Topics: Astrophysics of Galaxies, Astrophysics, Cosmology and Nongalactic Astrophysics, Astrophysics
Source: http://arxiv.org/abs/1501.01077
Arxiv.org
by Shadab Alam; Franco D. Albareti; Carlos Allende Prieto; F. Anders; Scott F. Anderson; Brett H. Andrews; Eric Armengaud; Éric Aubourg; Stephen Bailey; Julian E. Bautista; Rachael L. Beaton; Joseph Huehnerhoff; Linhua Jiang; Jennifer A. Johnson; Karen Kinemuchi; David Kirkby; Francisco Kitaura; Mark A. Klaene; Jean-Paul Kneib; Xavier P. Koenig; Charles R. Lam; Timothy C. Beers; Ting-Wen Lan; Dustin Lang; Pierre Laurent; Jean-Marc Le Goff; Alexie Leauthaud; Khee-Gan Lee; Young Sun Lee; Timothy C....
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The third generation of the Sloan Digital Sky Survey (SDSS-III) took data from 2008 to 2014 using the original SDSS wide-field imager, the original and an upgraded multi-object fiber-fed optical spectrograph, a new near-infrared high-resolution spectrograph, and a novel optical interferometer. All the data from SDSS-III are now made public. In particular, this paper describes Data Release 11 (DR11) including all data acquired through 2013 July, and Data Release 12 (DR12) adding data acquired...
Topics: Instrumentation and Methods for Astrophysics, Astrophysics, Astrophysics of Galaxies, Astrophysics,...
Source: http://arxiv.org/abs/1501.00963
Arxiv.org
by B. M. Gaensler; Iván Agudo; Takuya Akahori; Julie Banfield; Rainer Beck; Ettore Carretti; Jamie Farnes; Marijke Haverkorn; George Heald; David Jones; Thomas Landecker; Sui Ann Mao; Ray Norris; Shane O'Sullivan; Lawrence Rudnick; Dominic Schnitzeler; Nicholas Seymour; Xiaohui Sun
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Faraday rotation of polarised background sources is a unique probe of astrophysical magnetic fields in a diverse range of foreground objects. However, to understand the properties of the polarised sources themselves and of depolarising phenomena along the line of sight, we need to complement Faraday rotation data with polarisation observations over very broad bandwidths. Just as it is impossible to properly image a complex source with limited u-v coverage, we can only meaningfully understand...
Topics: Cosmology and Nongalactic Astrophysics, Astrophysics, Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1501.00626
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Full polarization measurements of 1665 and 1667-MHz OH masers at sites of massive star formation have been made with the Parkes 64-m radio telescope. Here we present the resulting spectra for 104 northerly sources. For more than 20 masers we made new measurements with the ATCA (which also revealed several hitherto unreported masers), in most cases yielding arcsecond precision to match the majority of sites. Position improvements assist in distinguishing OH masers with accompanying methanol...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1402.2360
Arxiv.org
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A population of intermediate-mass black holes (BHs) is predicted to be freely floating in the Milky Way (MW) halo, due to gravitational wave recoil, ejection from triple BH systems, or tidal stripping in the dwarf galaxies that merged to make the MW. As these BHs traverse the gaseous MW disk, a bow shock forms, producing detectable radio and mm/sub-mm synchrotron emission from accelerated electrons. We calculate the synchrotron flux to be $\sim \rm 0.01-10\, mJy$ at GHz frequency, detectable by...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1402.5975
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Here we discuss the evolution of binaries around MBH in nuclear stellar clusters. We focus on their secular evolution due to the perturbation by the MBH, while simplistically accounting for their collisional evolution. Binaries with highly inclined orbits in respect to their orbit around the MBH are strongly affected by secular processes, which periodically change their eccentricities and inclinations (e.g. Kozai--Lidov cycles). During periapsis approach, dissipative processes such as tidal...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1405.6029
Arxiv.org
by G. Leloudas; S. Schulze; T. Kruehler; J. Gorosabel; L. Christensen; A. Mehner; A. de Ugarte Postigo; R. Amorin; C. C. Thoene; J. P. Anderson; F. E. Bauer; A. Gallazzi; K. G. Helminiak; J. Hjorth; E. Ibar; D. Malesani; N. Morrell; J. Vinko; J. C. Wheeler
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Superluminous supernovae (SLSNe) are very bright explosions that were only discovered recently and that show a preference for occurring in faint dwarf galaxies. Understanding why stellar evolution yields different types of stellar explosions in these environments is fundamental in order to both uncover the elusive progenitors of SLSNe and to study star formation in dwarf galaxies. In this paper, we present the first results of our project to study SUperluminous Supernova Host galaxIES, focusing...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1409.8331
Context. Hydrogenated amorphous carbons, a-C:H, can incorporate a variety of heteroatoms, which can lead to interesting effects. Aims. To investigate the doping of interstellar a-C:H grains with, principally, Si, O, N and S atoms within the astrophysical context. Methods. A search of the literature on doped a-C:H reveals a number of interesting phenomena of relevance to astrophysics. Results. X dopants in a-C:H:X materials can affect the sp3/sp2 ratio (X = Si, O and N), lead to blue...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1411.5858
Arxiv.org
by J. Wagg; E. Da Cunha; C. L. Carilli; F. Walter; M. Aravena; I. Heywood; J. Hodge; E. Murphy; D. Riechers; M. Sargent; R. Wang
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The Square Kilometre Array will be a revolutionary instrument for the study of gas in the distant Universe. SKA1 will have sufficient sensitivity to detect and image atomic 21 cm HI in individual galaxies at significant cosmological distances, complementing ongoing ALMA imaging of redshifted high-J CO line emission and far-infrared interstellar medium lines such as [CII] 157.7 um. At frequencies below ~50 GHz, observations of redshifted emission from low-J transitions of CO, HCN, HCO+, HNC, H2O...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1412.5793
Arxiv.org
by O. Ivy Wong; K. Schawinski; G. I. G. Józsa; C. M. Urry; C. J. Lintott; B. D. Simmons; S. Kaviraj; K. L. Masters
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Recent work suggests blue ellipticals form in mergers and migrate quickly from the blue cloud of star-forming galaxies to the red sequence of passively evolving galaxies, perhaps as a result of black hole feedback. Such rapid reddening of stellar populations implies that large gas reservoirs in the pre-merger star-forming pair must be depleted on short time scales. Here we present pilot observations of atomic hydrogen gas in four blue early-type galaxies that reveal increasing spatial offsets...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1501.07653
Arxiv.org
by M. S. Miranda; B. A. Macfarlane; B. K. Gibson
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The spatial and temporal relationships between stellar age, kinematics, and chemistry are a fundamental tool for uncovering the physics driving galaxy formation and evolution. Observationally, these trends are derived using carefully selected samples isolated via the application of appropriate magnitude, colour, and gravity selection functions of individual stars; conversely, the analysis of chemodynamical simulations of galaxies has traditionally been restricted to the age, metallicity, and...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1502.00444
Arxiv.org
by F. La Barbera; I. Ferreras; A. Vazdekis
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The Initial Mass Function (IMF) of early-type galaxies (ETGs) has been found to feature systematic variations by both dynamical and spectroscopic studies. In particular, spectral line strengths, based on gravity-sensitive features, suggest an excess of low-mass stars in massive ETGs, i.e. a bottom-heavy IMF. The physical drivers of IMF variations are currently unknown. The abundance ratio of alpha elements, such as [Mg/Fe], has been suggested as a possible driver of the IMF changes, although...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1502.03449
Arxiv.org
by O. Berne; J. Montillaud; C. Joblin
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[Abridged] Fullerenes have been recently detected in various circumstellar and interstellar environments, raising the question of their formation pathway. It has been proposed that they can form by the photo-chemical processing of large polycyclic aromatic hydrocarbons (PAHs). Following our previous work on the evolution of PAHs in the NGC 7023 reflection nebula, we evaluate, using photochemical modeling, the possibility that the PAH C$_{66}$H$_{20}$ (i.e. circumovalene) can lead to the...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1503.03698
Arxiv.org
by Chen Hu; Pu Du; Kai-Xing Lu; Yan-Rong Li; Fang Wang; Jie Qiu; Jin-Ming Bai; Shai Kaspi; Luis C. Ho; Hagai Netzer; Jian-Min Wang
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This is the third in a series of papers reporting on a large reverberation-mapping campaign aimed to study the properties of active galactic nuclei (AGNs) with high accretion rates. We present new results on the variability of the optical Fe II emission lines in 10 AGNs observed by the Yunnan Observatory 2.4m telescope during 2012--2013. We detect statistically significant time lags, relative to the AGN continuum, in nine of the sources. This accurate measurement is achieved by using a...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1503.03611
Arxiv.org
by Jennifer Donovan Meyer; J. E. G. Peek; Mary Putman; Jana Grcevich
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We present ultraviolet (UV) follow-up of a sample of potential dwarf galaxy candidates selected for their neutral hydrogen (HI) properties, taking advantage of the low UV background seen by the GALEX satellite and its large and publicly available imaging footprint. The HI clouds, which are drawn from published GALFA-HI and ALFALFA HI survey compact cloud catalogs, are selected to be galaxy candidates based on their spatial compactness and non-association with known high-velocity cloud complexes...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1506.00044
Arxiv.org
by V. V. Bobylev
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This review is devoted to studies of the Gould belt and the Local system. Since the Gould belt is the giant stellar-gas complex closest to the sun, its stellar component is characterized, along with the stellar associations and diffuse clusters, cold atomic and molecular gas, high-temperature coronal gas, and dust contained in it. Questions relating to the kinematic features of the Gould belt are discussed and the most interesting scenarios for its origin and evolution are examined.
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1507.06516
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We study the star formation history for a sample of 154 galaxies with stellar mass $10^{10}\lesssim M_{\ast}\lesssim 10^{12} M_{\odot}$ in the redshift range $0.7 < z < 0.9$. We do this using stellar population models combined with full-spectrum fitting of good quality spectra and high resolution photometry. For a subset of 68 galaxies ($M_{\ast}\gtrsim 10^{11} M_{\odot}$) we additionally construct dynamical models. These use an axisymmetric solution to the Jeans equations, which allows...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1508.05009
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Observations show the presence, in the halo of our Galaxy, of stars moving at velocities so high to require an acceleration mechanism involving the presence of a massive central black hole. Thus, in the frame of a galaxy hosting a supermassive black hole ($10^8$ $M_{\odot}$) we investigated a mechanism for the production of high velocity stars, which was suggested by the results of N-body simulations of the close interaction between a massive, orbitally decayed, globular cluster and the super...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1509.03170
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Molecular clouds, the birthplaces of stars in galaxies, form dynamically from the diffuse atomic gas of the interstellar medium (ISM). The ISM is also threaded by magnetic fields which have a large impact on its dynamics. In particular, star forming regions must be magnetically supercrit- ical in order to accomodate gas clumps which can collapse under their own weight. Based on a parameter study of three dimensional magneto-hydrodyamical (MHD) simulations, we show that the long-standing problem...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1509.03436
The dependence of the turnover frequency on the linear size is presented for a sample of GPS and CSS radio sources derived from complete samples. The dependence of the luminosity of the emission at the peak frequency with the linear size and the peak frequency is also presented for the galaxies in the sample. The luminosity of the smaller sources evolve strongly with the linear size. Optical depth effects have been included to the 3D model for the radio source of Kaiser (2000) to study the...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1601.05406
Arxiv.org
by A. A. Hakobyan; A. G. Karapetyan; L. V. Barkhudaryan; G. A. Mamon; D. Kunth; A. R. Petrosian; V. Adibekyan; L. S. Aramyan; M. Turatto
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We present an analysis of the impact of bars on the radial distributions of the different types of supernovae (SNe) in the stellar discs of host galaxies with various morphologies. We find that in Sa-Sbc galaxies, the radial distribution of core-collapse (CC) SNe in barred hosts is inconsistent with that in unbarred ones, while the distributions of SNe Ia are not significantly different. At the same time, the radial distributions of both types of SNe in Sc-Sm galaxies are not affected by bars....
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1607.02582
Arxiv.org
by Ling Zhu; Aaron J. Romanowsky; Glenn van de Ven; R. J. Long; Laura L. Watkins; Vincenzo Pota; Nicola R. Napolitano; Duncan A. Forbes; Jean Brodie; Caroline Foster
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We construct a suite of discrete chemo-dynamical models of the giant elliptical galaxy NGC 5846. These models are a powerful tool to constrain both the mass distribution and internal dynamics of multiple tracer populations. We use Jeans models to simultaneously fit stellar kinematics within the effective radius $R_{\rm e}$, planetary nebula (PN) radial velocities out to $3\, R_{\rm e}$, and globular cluster (GC) radial velocities and colours out to $6\,R_{\rm e}$. The best-fitting model is a...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1608.08238
Arxiv.org
by Bo Hu; Karl M. Menten; Yuanwei Wu; Anna Bartkiewicz; Kazi Rygl; Mark J. Reid; James S. Urquhart; Xingwu Zheng
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We conducted VLA C-configuration observations to measure positions and luminosities of Galactic Class II 6.7 GHz methanol masers and their associated ultra-compact H II regions. The spectral resolution was 3.90625 kHz and the continuum sensitivity reached 45 \uJypb. We mapped 372 methanol masers with peak flux densities of more than 2 Jy selected from the literature, 367 of them were detected. Absolute positions have nominal uncertainties of 0.3 arcsec. In this first paper on the data analysis,...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1609.03280
Arxiv.org
by C. Moni Bidin; D. I. Casetti-Dinescu; T. M. Girard; L. Zhang; R. A. Mendez; K. Vieira; V. I. Korchagin; W. F. van Altena
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Despite their close proximity, the complex interplay between the two Magellanic Clouds, the Milky Way, and the resulting tidal features, is still poorly understood. Recent studies have shown that the Large Magellanic Cloud (LMC) has a very extended disk strikingly perturbed in its outskirts. We search for recent star formation in the far outskirts of the LMC, out to ~30 degrees from its center. We have collected intermediate-resolution spectra of thirty-one young star candidates in the...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1612.03072
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by ChangHoon Hahn; Michael R. Blanton; John Moustakas; Alison L. Coil; Richard J. Cool; Daniel J. Eisenstein; Ramin A. Skibba; Kenneth C. Wong; Guangtun Zhu
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We investigate the effects of galaxy environment on the evolution of the quiescent fraction ($f_\mathrm{Q}$) from z =0.8 to 0.0 using spectroscopic redshifts and multi-wavelength imaging data from the PRIsm MUlti-object Survey (PRIMUS) and the Sloan Digitial Sky Survey (SDSS). Our stellar mass limited galaxy sample consists of ~14,000 PRIMUS galaxies within z = 0.2-0.8 and ~64,000 SDSS galaxies within z = 0.05-0.12. We classify the galaxies as quiescent or star-forming based on an evolving...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1412.7162
Arxiv.org
by C. Gonzalo Díaz; Emma V. Ryan-Weber; Jeff Cooke; Yusei Koyama; Masami Ouchi
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The flow of baryons to and from a galaxy, which is fundamental for galaxy formation and evolution, can be studied with galaxy-metal absorption system pairs. Our search for galaxies around CIV absorption systems at $z\sim5.7$ showed an excess of photometric Lyman-$\alpha$ emitter (LAE) candidates in the fields J1030+0524 and J1137+3549. Here we present spectroscopic follow-up of 33 LAEs in both fields. In the first field, three out of the five LAEs within 10$h^{{-}1}$ projected comoving Mpc from...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1412.6694
Arxiv.org
by J. Malinen; L. Montier; J. Montillaud; M. Juvela; I. Ristorcelli; S. E. Clark; O. Berné; J. -Ph. Bernard; V. -M. Pelkonen; D. C. Collins
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The nearby cloud L1642 is one of only two known very high latitude (|b| > 30 deg) clouds actively forming stars. It is a rare example of star formation in isolated conditions, and can reveal important details of star formation in general, e.g., of the effect of magnetic fields. We compare Herschel dust emission structures and magnetic field orientation revealed by Planck polarization maps in L1642. The high-resolution ($\sim20"$) Herschel data reveal a complex structure including a...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1512.03775
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We address the presently exciting issue of the presence of stellar clusters in the periphery of the Magellanic Clouds (MCs) and beyond by making use of a wealth of wide-field high-quality images released in advance from the Magellanic Stellar Hystory (SMASH) survey. We conducted a sound search for new stellar cluster candidates from suitable kernel density estimators running for appropriate ranges of radii and stellar densities. In addition, we used a functional relationship to account for the...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1612.09221
Arxiv.org
by Jinyi Yang; Xiaohui Fan; Xue-Bing Wu; Feige Wang; Fuyan Bian; Qian Yang; Ian D. McGreer; Weimin Yi; Linhua Jiang; Richard Green; Minghao Yue; Shu Wang; Zefeng Li; Jiani Ding; Simon Dye; Andy Lawrence
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We present initial results from the first systematic survey of luminous $z\sim 5.5$ quasars. Quasars at $z \sim$ 5.5, the post-reionization epoch, are crucial tools to explore the evolution of intergalactic medium, quasar evolution and the early super-massive black hole growth. However, it has been very challenging to select quasars at redshifts 5.3 $\le z \le$ 5.7 using conventional color selections, due to their similar optical colors to late-type stars, especially M dwarfs, resulting in a...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1703.03526
Arxiv.org
by Stacy McGaugh; Jim Schombert
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We combine Spitzer $3.6\mu$ observations of a sample of disk galaxies spanning over 10 magnitudes in luminosity with optical luminosities and colors to test population synthesis prescriptions for computing stellar mass. Many commonly employed models fail to provide self-consistent results: the stellar mass estimated from the luminosity in one band can differ grossly from that of another band for the same galaxy. Independent models agree closely in the optical ($V$-band), but diverge at longer...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1407.1839
We report on the discovery of 28 $z\approx0.8$ metal-poor galaxies in DEEP2. These galaxies were selected for their detection of the weak [OIII]$\lambda$4363 emission line, which provides a "direct" measure of the gas-phase metallicity. A primary goal for identifying these rare galaxies is to examine whether the fundamental metallicity relation (FMR) between stellar mass, gas metallicity, and star formation rate (SFR) holds for low stellar mass and high SFR galaxies. The FMR suggests...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1412.1834
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by S. N. Zhang; L. Ji; T. R. Kallman; Y. S. Yao; C. S. Froning; Q. S. Gu; G. A. Kriss
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We present a new method to model a HST/COS spectrum, aimed to analyze intrinsic UV absorption from the outflow of Mrk 290, a Seyfert I galaxy. We use newly updated XSTAR to generate photoionization models for the intrinsic absorption from the AGN outflow, the line emission from the AGN broad and narrow line regions, and the local absorption from high velocity clouds and Galactic interstellar medium. The combination of these physical models accurately fit the COS spectrum. Three intrinsic...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1412.2935
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by M. Orienti; F. D'Ammando; M. Giroletti; G. Giovannini; F. Panessa
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Despite targets of many multiwavelength campaigns, the main physical processes at work in AGN are still under debate. In particular the origin of the radio emission and the mechanisms involved are among the open questions in astrophysics. In the radio-loud AGN population the radio emission is linked to the presence of bipolar outflows of relativistic jets. However, the large majority of the AGN population do not form powerful highly-relativistic jets on kpc scales and are characterized by radio...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1412.5846
Arxiv.org
by Abbas Askar; Mirek Giersz; Wojciech Pych; Arkadiusz Olech; Arkadiusz Hypki
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We introduce and present preliminary results from COCOA (Cluster simulatiOn Comparison with ObservAtions) code for a star cluster after 12 Gyrs of evolution simulated using the MOCCA code. The COCOA code is being developed to quickly compare results of numerical simulations of star clusters with observational data. We use COCOA to obtain parameters of the projected cluster model. For comparison, a FITS file of the projected cluster was provided to observers so that they could use their...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1501.00417
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Based on a simple geometrical approach, we analyze the evolution of the Kozai-Lidov mechanism for stars around shrinking massive black hole binaries on circular orbits. We find that, due to a peculiar bifurcation pattern induced by the Newtonian potential of stellar clusters, the orbit of stars could become highly eccentric. This transition occurs abruptly for stars with small initial eccentricities. Our approach would be also useful for studying the Kozai-Lidov mechanism in various...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1508.05762
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by Giuseppe Murante; Pierluigi Monaco; Stefano Borgani; Luca Tornatore; Klaus Dolag; David Goz
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We present results of cosmological simulations of disk galaxies carried out with the GADGET-3 TreePM+SPH code, where star formation and stellar feedback are described using our MUlti Phase Particle Integrator (MUPPI) model. This description is based on simple multi-phase model of the interstellar medium at unresolved scales, where mass and energy flows among the components are explicitly followed by solving a system of ordinary differential equations. Thermal energy from SNe is injected into...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1411.3671
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A survey of Michel Henon contributions to the study of globular cluster systems.
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1411.4932
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by Heidi Jo Newberg; Matthew Newby; Travis Desell; Malik Magdon-Ismail; Boleslaw Szymanski; Carlos Varela
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MilkyWay@home is a volunteer computing project that allows people from every country in the world to volunteer their otherwise idle processors to Milky Way research. Currently, more than 25,000 people (150,000 since November 9, 2007) contribute about half a PetaFLOPS of computing power to our project. We currently run two types of applications: one application fits the spatial density profile of tidal streams using statistical photometric parallax, and the other application finds the N-body...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1411.6003
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by Billy Vazquez; Pasquale Galianni; Michael Richmond; Andrew Robinson; David J. Axon; Keith Horne; Triana Almeyda; Michael Fausnaugh; Bradley M. Peterson; Mark Bottorff; Jack Gallimore; Moshe Eltizur; Hagai Netzer; Thaisa Storchi-Bergmann; Alessandro Marconi; Alessandro Capetti; Dan Batcheldor; Catherine Buchanan; Giovanna Stirpe; Makoto Kishimoto; Christopher Packham; Enrique Perez; Clive Tadhunter; John Upton; Vicente Estrada-Carpenter
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We present results from a fifteen-month campaign of high-cadence (~ 3 days) mid-infrared Spitzer and optical (B and V ) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). We find that the 3.6 $\mu$m and 4.5 $\mu$m flux variations lag behind those of the optical continuum by $37.2^{+2.4}_{-2.2}$ days and $47.1^{+3.1}_{-3.1}$ days, respectively. We report a cross-correlation time lag...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1502.01977
Arxiv.org
by Nor Pirzkal; Dan Coe; Brenda L. Frye; Gabriel Brammer; John Moustakas; Barry Rothberg; Thomas J. Broadhurst; Rychard Bouwens; Larry Bradley; Arjen van der Wel; Daniel D. Kelson; Megan Donahue; Adi Zitrin; Leonidas Moustakas; Elizabeth Barker
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We report on our first set of spectroscopic Hubble Space Telescope observations of the z~11 candidate galaxy strongly lensed by the MACSJ0647.7+7015 galaxy cluster. The three lensed images are faint and we show that these early slitless grism observations are of sufficient depth to investigate whether this high-redshift candidate, identified by its strong photometric break at ~1.5 micron, could possibly be an emission line galaxy at a much lower redshift. While such an interloper would imply...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1502.05681
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by Lijie Liu; Yu Gao; Thomas R. Greve
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We study the global SF law - the relation between gas and SFRs in a sample of 181 local galaxies with L_IR spanning almost five orders of magnitude, which includes 115 normal galaxies and 66 (U)LIRGs. We derive their atomic, molecular gas and dense molecular gas masses using newly available HI, CO and HCN data from the literature, and SFRs are determined both from total IR and 1.4 GHz radio continuum (RC) luminosities. In order to derive the disk-averaged surface densities of gas and SFRs, we...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1502.08001
Arxiv.org
by Xiaoyu Kang; Ruixiang Chang; Fenghui Zhang; Liantao Cheng; Lang Wang
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NGC 5194 (M51a) is a grand-design spiral galaxy and undergoing interactions with its companion. Here we focus on investigating main properties of its star-formation history (SFH) by constructing a simple evolution model, which assumes that the disc builds up gradually by cold gas infall and the gas infall rate can be parameterizedly described by a Gaussian form. By comparing model predictions with the observed data, we discuss the probable range for free parameter in the model and then know...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1503.00398
Cappellari (2008) presented a flexible and efficient method to model the stellar kinematics of anisotropic axisymmetric and spherical stellar systems. The spherical formalism could be used to model the line-of-sight velocity second moments allowing for essentially arbitrary radial variation in the anisotropy and general luminous and total density profiles. Here we generalize the spherical formalism by providing the expressions for all three components of the projected second moments, including...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1504.05533
Arxiv.org
by S. A. Hakopian; S. K. Balayan; T. A. Movsessian
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Observations of Mrk 171, aimed at conduction of panoramic spectroscopy, were undertaken with the Byurakan 2.6-m telescope using spectrograph VAGR. Within the two components of the galaxy, there were differentiated eight condensations of starforming activity, i.e. HII regions, and no sign of AGN activity was revealed inspite of existing suggestions.
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1401.3765
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by Keith W. Bannister; Greg. J. Madsen
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The recent detection of Fast Radio Bursts (FRBs) has generated strong interest in identifying the origin of these bright, non-repeating, highly dispersed pulses. The principal limitation in understanding the origin of these bursts is the lack of reliable distance estimates; their high dispersion measures imply that they may be at cosmological distances ($0.1 < z < 1.0$). Here we discuss new distance constraints to the FRB010621 (a.k.a J1852$-$08) first reported by Keane. We use velocity...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1402.0268
Arxiv.org
by T. Albertsson; N. Indriolo; H. Kreckel; D. Semenov; K. N. Crabtree; Th. Henning
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The chemistry in the diffuse interstellar medium initiates the gradual increase of molecular complexity during the life cycle of matter. A key molecule that enables build-up of new molecular bonds and new molecules via proton-donation is H3+. Its evolution is tightly related to molecular hydrogen and thought to be well understood. However, recent observations of ortho and para lines of H2 and H3+ in the diffuse ISM showed a puzzling discrepancy in nuclear spin excitation temperatures and...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1403.6533
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Most massive galaxies show emission lines that can be characterized as LINERs. To what extent this emission is related to AGNs or to stellar processes is still an open question. In this paper, we analysed a sample of such galaxies to study the central region in terms of nuclear and circumnuclear emission lines, as well as the stellar component properties. For this reason, we selected 10 massive ($\sigma$ > 200 km/s) nearby (d < 31 Mpc) galaxies and observed them with the IFU/GMOS...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1403.6840
Arxiv.org
by A. V. Mosenkov; N. Ya. Sotnikova; V. P. Reshetnikov
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We analyzed several basic correlations between structural parameters of galaxies. The data were taken from various samples in different passbands which are available in the literature. We discuss disc scaling relations as well as some debatable issues concerning the so-called Photometric Plane for bulges and elliptical galaxies in different forms and various versions of the famous Kormendy relation. We show that some of the correlations under discussion are artificial (self-correlations), while...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1403.7555
Arxiv.org
by G. Natale; K. Foyle; C. D. Wilson; N. Kuno
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We present a multiwavelength study of a sample of far-infrared (FIR) sources detected on the Herschel broad--band maps of the nearby galaxy M33. We perform source photometry on the FIR maps as well as mid-infrared (MIR), H$\alpha$, far-ultraviolet and integrated HI and CO line emission maps. By fitting MIR/FIR dust emission spectra, the source dust masses, temperatures and luminosities are inferred. The sources are classified based on their H$\alpha$ morphology (substructured versus...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1404.2310
Arxiv.org
by K. G. Johnston; H. Beuther; H. Linz; A. Schmiedeke; S. E. Ragan; Th. Henning
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The massive infrared dark cloud G0.253+0.016 projected 45pc from the Galactic centre contains ~10^5Msun of dense gas whilst being mostly devoid of observed star-formation tracers. To scrutinise the physical properties, dynamics and structure of this cloud with reference to its star-forming potential, we have carried out a concerted SMA and IRAM 30m study of this cloud in dust continuum, CO isotopologues, shock tracing molecules, as well as H$_2$CO to trace the gas temperature. We detect and...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1404.1372
Arxiv.org
by Brett A. McGuire; P. Brandon Carroll; James L. Sanders; Susanna L. Widicus Weaver; Geoffrey A. Blake; Anthony J. Remijan
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The results of a Caltech Submillimeter Observatory (CSO) search for $l$-C$_3$H$^+$, first detected by Pety et al. (2012) in observations toward the Horsehead photodissociation region (PDR), are presented. A total of 39 sources were observed in the 1 mm window. Evidence of emission from $l$-C$_3$H$^+$ is found in only a single source - the Orion Bar PDR region, which shows a rotational temperature of 178(13) K and a column density of 7(2) x $10^{11}$ cm$^{-2}$. In the remaining sources, upper...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1405.7057
Arxiv.org
by S. E. Sale; J. E. Drew; G. Barentsen; H. J. Farnhill; R. Raddi; M. J. Barlow; J. Eislöffel; J. S. Vink; P. Rodríguez-Gil; N. J. Wright
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We present a three dimensional map of extinction in the Northern Galactic Plane derived using photometry from the IPHAS survey. The map has fine angular ($\sim 10$ arcmin) and distance (100 pc) sampling allied to a significant depth ($\gtrsim 5$ kpc). We construct the map using a method based on a hierarchical Bayesian model as previously described by Sale (2012). In addition to mean extinction, we also measure differential extinction, which arises from the fractal nature of the ISM, and show...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1406.0009
Arxiv.org
by Georgina Coldwell; Sol Alonso; Fernanda Duplancic; Maren Hempel; Valentin D. Ivanov; Dante Minniti
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Suzaku and Chandra X-ray observations detected a new cluster of galaxies, Suzaku J1759-3450, at a redshift z=0.13. It is located behind the Milky Way, and the high Galactic dust extinction renders it nearly invisible at optical wavelengths. We attempt here to confirm the galaxy cluster with near-infrared imaging observations, and to characterize its central member galaxies. Images from the VVV survey were used to detect candidate member galaxies of Suzaku J1759-3450 within the central region of...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1407.0262
Arxiv.org
by Nimish P. Hathi; O. Le Fèvre; O. Ilbert; P. Cassata; L. A. M. Tasca; B. C. Lemaux; B. Garilli; V. Le Brun; D. Maccagni; L. Pentericci; R. Thomas; E. Vanzella; G. Zamorani; E. Zucca; R. Amorín; S. Bardelli; L. P. Cassarà; M. Castellano; A. Cimatti; O. Cucciati; A. Durkalec; A. Fontana; M. Giavalisco; A. Grazian; L. Guaita; A. Koekemoer; S. Paltani; J. Pforr; B. Ribeiro; D. Schaerer; M. Scodeggio; V. Sommariva; M. Talia; L. Tresse; D. Vergani; P. Capak; S. Charlot; T. Contini; J. G. Cuby; S....
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The aim of this paper is to investigate spectral and photometric properties of 854 faint ($i_{AB}$
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1503.01753
Arxiv.org
by H. S. Liszt; V. V. Guzman; J. Pety; M. Gerin; D. A. Neufeld; P. Gratier
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To study the usefulness of \CFP\ as a tracer of the regions where C\p\ and \HH\ coexist in the interstellar medium. We used the Plateau de Bure Interferometer to synthesize \CFP\ J=1-0 absorption at 102.6 GHz toward the core of the distant HII region W49N at l = 43.2\degr, b=0.0\degr, and we modeled the fluorine chemistry in diffuse/translucent molecular gas. We detected \CFP\ absorption over a broad range of velocity showing that \CFP\ is widespread in the \HH-bearing Galactic disk gas....
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1505.07927
Arxiv.org
by D. I. Casetti-Dinescu; D. A. Nusdeo; T. M. Girard; V. I. Korchagin; W. F. van Altena
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We combine the Siding Spring Survey of RR Lyrae stars with the Southern Proper Motion Catalog 4, in order to detect and kinematically characterize overdensities in the inner halo of the Milky Way. We identify one such overdensity above the Galactic plane, in quadrant 4 of the Galaxy. The overdensity extends at least 20 degrees in longitude, has an average heliocentric distance of 8 kpc with a depth of 4 kpc, and is confined within 4 kpc of the Galactic plane. Its metallicity distribution is...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1507.01459
Arxiv.org
by Jiayin Gu; Cuihua Du; Yunpeng Jia; Xiyan Peng; Zhenyu Wu; Yingjie Jing; Jun Ma; Xu Zhou; Xiaohui Fan; Zhou Fan; Yipeng Jing; Zhaoji Jiang; Michael Lesser; Jundan Nie; Shiyin Shen; Jiali Wang; Hu Zou; Tianmeng Zhang; Zhimin Zhou
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Based on SDSS g, r and SCUSS (South Galactic Cap of u-band Sky Survey) $u$ photometry, we develop a photometric calibration for estimating the stellar metallicity from $u-g$ and $g-r$ colors by using the SDSS spectra of 32,542 F- and G-type main sequence stars, which cover almost $3700$ deg$^{2}$ in the south Galactic cap. The rms scatter of the photometric metallicity residuals relative to spectrum-based metallicity is $0.14$ dex when $g-r 0.4$. Due to the deeper and more accurate magnitude of...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1507.02054
Arxiv.org
by J. Scharwächter; M. A. Dopita; P. Shastri; R. Davies; L. Kewley; E. Hampton; R. Sutherland; P. Kharb; J. Jose; H. Bhatt; S. Ramya; C. Jin; J. Banfield; I. Zaw; S. Juneau; B. James; S. Srivastava
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The Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7) is a targeted survey probing the narrow-line regions (NLRs) of a representative sample of ~140 nearby (z
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1507.01952
Arxiv.org
by Munier Salem; Gurtina Besla; Greg Bryan; Mary Putman; Roeland P. van der Marel; Stephanie Tonnesen
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Recent observations have constrained the orbit and structure of the Large Magellanic Cloud (LMC), implying a well-constrained pericentric passage about the Milky Way (MW) ~ 50 Myr ago. In this scenario, the LMC's gaseous disk has recently experienced maximal ram pressure stripping, suggesting the current extent of its HI disk directly probes the medium in which it is moving. From the observed stellar and HI distributions of the system we find evidence of a truncated gas profile along the...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1507.07935
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by Ben Bar-Or; Tal Alexander
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A massive black hole (MBH) consumes stars whose orbits evolve into the small phase-space volume of unstable orbits, the "loss-cone", which take them directly into the MBH, or close enough to interact strongly with it. The resulting phenomena: tidal heating and tidal disruption, binary capture and hyper-velocity star ejection, gravitational wave (GW) emission by inspiraling compact remnants, or hydrodynamical interactions with an accretion disk, are of interest as they can produce...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1508.01390
Arxiv.org
by D. Calzetti; K. E. Johnson; A. Adamo; J. S. Gallagher; J. E. Andrews; L. J. Smith; G. C. Clayton; J. C. Lee; E. Sabbi; L. Ubeda; H. Kim; J. E. Ryon; D. Thilker; S. N. Bright; E. Zackrisson; R. C. Kennicutt; S. E. de Mink; B. C. Whitmore; A. Aloisi; R. Chandar; M. Cignoni; D. Cook; D. A. Dale; B. G. Elmegreen; D. M. Elmegreen; A. S. Evans; M. Fumagalli; D. A. Gouliermis; K. Grasha; E. K. Grebel; M. R. Krumholz; R. Walterbos; A. Wofford; T. M. Brown; C. Christian; C. Dobbs; A. Herrero; L. Kahre;...
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The nearby dwarf starburst galaxy NGC5253 hosts a number of young, massive star clusters, the two youngest of which are centrally concentrated and surrounded by thermal radio emission (the `radio nebula'). To investigate the role of these clusters in the starburst energetics, we combine new and archival Hubble Space Telescope images of NGC5253 with wavelength coverage from 1500 Ang to 1.9 micron in 13 filters. These include H-alpha, P-beta, and P-alpha, and the imaging from the Hubble Treasury...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1508.04476
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by Juan Pablo Caso; Lilia P. Bassino; Matías Gómez
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NGC 4753 is a bright (M_V approx -22.3) lenticular galaxy. It is a very interesting target to test different theories of formation of lenticular galaxies, due to its low-density environment and complex structure. We perform the first comprehensive study of NGC 4753 globular cluster system (GCS), using Gemini/GMOS and CTIO/MosaicII images. Our results indicate a rather poor GCS of approx 1000 members. Its azimuthal distribution follows the shape of the galaxy bulge. The GC colour distribution is...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1508.07653
Arxiv.org
by Laura L. Watkins; Roeland P. van der Marel; Andrea Bellini; Jay Anderson
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We present dynamical distance estimates for 15 Galactic globular clusters and use these to check the consistency of dynamical and photometric distance estimates. For most of the clusters, this is the first dynamical distance estimate ever determined. We extract proper-motion dispersion profiles using cleaned samples of bright stars from the Hubble Space Telescope proper-motion catalogs recently presented in Bellini et al. (2014) and compile a set of line-of-sight velocity-dispersion profiles...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1509.00513
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We study ten galaxy groups and clusters suggested in the literature to be "fossil system (FS)" based on \chandra\ observations. According to the $M_{500}-T$ and $L_{\rm X}-T$ relations, the gas properties of FSs are not physically distinct from ordinary galaxy groups or clusters. We also first study the $f_{\rm gas,~2500}-T$ relation and find that the FS exhibits same as ordinary systems. The gas densities of FSs within $0.1r_{200}$, are $\sim 10^{-3}$ cm$^{-3}$, which is the same...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1509.03793
Arxiv.org
by A. Feldmeier-Krause; N. Neumayer; R. Schödel; A. Seth; M. Hilker; P. T. de Zeeuw; H. Kuntschner; C. J. Walcher; N. Lützgendorf; M. Kissler-Patig
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The Galactic centre hosts a crowded, dense nuclear star cluster with a half-light radius of 4 pc. Most of the stars in the Galactic centre are cool late-type stars, but there are also >100 hot early-type stars in the central parsec of the Milky Way. These stars are only 3-8 Myr old. Our knowledge of the number and distribution of early-type stars in the Galactic centre is incomplete. Only a few spectroscopic observations have been made beyond a projected distance of 0.5 pc of the Galactic...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1509.04707
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We report a photometric study of globular clusters (GCs), ultracompact dwarfs (UCDs), and dwarf galaxies in the giant merging galaxy cluster Abell 2744 at z = 0.308. Color-magnitude diagrams of the point sources derived from deep F814W (restframe r') and F105W (restframe I) images of Abell 2744 in the Hubble Space Telescope Frontier Field show a rich population of point sources whose colors are similar to those of typical GCs. These sources are as bright as -14.9 < M_r' < -11.4 (26.0 <...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1608.05750
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There is a supermassive black hole, a gaseous accretion disk and compact star cluster in the center of active galactic nuclei, as known today. So the activity of AGN can be represented as the result of interaction of these three subsystems. In this work we investigate the dynamical interaction of a central star cluster surrounding a supermassive black hole and a central accretion disk. The dissipative force acting on stars in the disk leads to an asymmetry in the phase space distribution of the...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1610.02838
Arxiv.org
by Yuan Li; Mateusz Ruszkowski; Greg L. Bryan
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We analyze heating and cooling processes in an idealized simulation of a cool-core cluster, where momentum-driven AGN feedback balances radiative cooling in a time-averaged sense. We find that, on average, energy dissipation via shock waves is almost an order of magnitude higher than via turbulence. Most of the shock waves in the simulation are very weak shocks with Mach numbers smaller than 1.5, but the stronger shocks, although rare, dissipate energy more effectively. We find that shock...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1611.05455
Arxiv.org
by Thomas P. K. Martinsson; Marc A. W. Verheijen; Matthew A. Bershady; Kyle B. Westfall; David R. Andersen; Rob A. Swaters
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We present results from 21 cm radio synthesis imaging of 28 spiral galaxies from the DiskMass Survey obtained with the VLA, WSRT, and GMRT facilities. We detail the observations and data reduction procedures and present a brief analysis of the radio data. We construct 21 cm continuum images, global HI emission-line profiles, column-density maps, velocity fields, and position-velocity diagrams. From these we determine star formation rates (SFRs), HI line widths, total HI masses, rotation curves,...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1510.07666
Context. The properties of hydrogenated amorphous carbon (a-C:H) dust are known to evolve in response to the local conditions. Aims. We present an adaptable model for the determination of the optical properties of low-temperature, interstellar a-C:H grains that is based on the fundamental physics of their composition. Methods. The imaginary part of the refractive index, k, for a-C:H materials, from 50 eV to cm wavelengths, is derived and the real part, n, of the refractive index is then...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1511.01682
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by Carl J. Grillmair; Jeffrey L. Carlin
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Recent years have seen the discovery of an ever growing number of stellar debris streams and clouds. These structures are typically detected as extended and often curvilinear overdensities of metal-poor stars that stand out from the foreground disk population. The streams typically stretch tens of degrees or more across the sky, even encircling the Galaxy, and range in heliocentric distance from 3 to 100 kpc. This chapter summarizes the techniques used for finding such streams and provides...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1603.08936
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by Michael A. Dopita; David C. Nicholls; Ralph S. Sutherland; Lisa J. Kewley; Brent A. Groves
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We report here on the discovery of faint extended wings of H\alpha\ observed out to an apparent velocity of ~ 7600 km/s in the Orion Nebula (M42) and in five HII regions in the Large and the Small Magellanic Clouds. We show that, these wings are caused by Raman scattering of both the O I and Si II resonance lines and stellar continuum UV photons with H I followed by radiative decay to the H I n=2 level. The broad wings also seen in H\beta\ and in H\gamma\ result from Raman scattering of the UV...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1605.08828
Arxiv.org
by P. B. Kuzma; G. S. Da Costa; A. D. Mackey; T. A. Roderick
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We present the results of a wide-field imaging survey of the periphery of the Milky Way globular cluster NGC 7089 (M2). Data were obtained with MegaCam on the Magellan Clay Telescope, and the Dark Energy Camera on the Blanco Telescope. We find that M2 is embedded in a diffuse stellar envelope extending to a radial distance of at least $\sim 60^{\prime}$ ($\sim 210$ pc) -- five times the nominal tidal radius of the cluster. The envelope appears nearly circular in shape, has a radial density...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1606.05949
It is now well-established that the stellar initial mass function (IMF) can be determined from the absorption line spectra of old stellar systems, and this has been used to measure the IMF and its variation across the early-type galaxy population. Previous work focused on measuring the slope of the IMF over one or more stellar mass intervals, implicitly assuming that this is a good description of the IMF and that the IMF has a universal low-mass cutoff. In this work we consider more flexible...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1612.00013
Arxiv.org
by R. Herrera-Camus; A. Bolatto; M. Wolfire; E. Ostriker; B. Draine; A. Leroy; K. Sandstrom; L. Hunt; R. Kennicutt; D. Calzetti; J. D. Smith; K. Croxall; M. Galametz; I. de Looze; D. Dale; A. Crocker; B. Groves
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Dynamic and thermal processes regulate the structure of the multi-phase interstellar medium (ISM), and ultimately establish how galaxies evolve through star formation. Thus, to constrain ISM models and better understand the interplay of these processes, it is of great interest to measure the thermal pressure ($P_{\rm th}$) of the diffuse, neutral gas. By combining [C II] 158 $\mu$m, HI, and CO data from 31 galaxies selected from the Herschel KINGFISH sample, we have measured thermal pressures...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1701.01438
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A set of Smoothed Particle Hydrodynamics simulations of the influence of photoionising radiation and stellar winds on a series of 10$^{4}$M$_{\odot}$ turbulent molecular clouds with initial virial ratios of 0.7, 1.1, 1.5, 1.9 and 2.3 and initial mean densities of 136, 1135 and 9096\,cm$^{-3}$ are presented. Reductions in star formation efficiency rates are found to be modest, in the range $30\%-50\%$ and to not vary greatly across the parameter space. In no case was star formation entirely...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1701.03653
Arxiv.org
by Luming Sun; Hongyan Zhou; Tuo Ji; Peng Jiang; Bo Liu; Wenjuan Liu; Xiang Pan; Xiheng Shi; Jianguo Wang; Tinggui Wang; Chenwei Yang; Shaohua Zhang; Lauren P. Miller
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In this paper we present an analysis of absorption line variability in mini-BAL quasar LBQS 1206+1052. The SDSS spectrum demonstrates that the absorption troughs can be divided into two components of blueshift velocities of $\sim$700 km s$^{-1}$ and $\sim$1400 km s$^{-1}$ relative to the quasar rest-frame. The former component shows rare Balmer absorption, which is an indicator of high density absorbing gas, thus the quasar is worth follow-up spectroscopic observations. Our follow-up optical...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1703.02686
Arxiv.org
by Charlie Conroy; Pieter van Dokkum; Jieun Choi
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Long period variable stars arise in the final stages of the asymptotic giant branch phase of stellar evolution. They have periods of up to ~1000d and amplitudes that can exceed a factor of three in the I-band flux. These stars pulsate predominantly in their fundamental mode, which is a function of mass and radius, and so the pulsation periods are sensitive to the age of the underlying stellar population. The overall number of long period variables in a population is directly related to their...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1511.04086
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Recent interferometer observations have found that the D2O/HDO abundance ratio is higher than that of HDO/H2O by about one order of magnitude in the vicinity of low-mass protostar NGC 1333-IRAS 2A, where water ice has sublimated. Previous laboratory and theoretical studies show that the D2O/HDO ice ratio should be lower than the HDO/H2O ice ratio, if HDO and D2O ices are formed simultaneously with H2O ice. In this work, we propose that the observed feature, D2O/HDO > HDO/H2O, is a natural...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1512.04291
Arxiv.org
by Julia Roman-Duval; Mark Heyer; Christopher Brunt; Paul Clark; Ralf Klessen; Rahul Shetty
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Emission from carbon monoxide (CO) is ubiquitously used as a tracer of dense star forming molecular clouds. There is, however, growing evidence that a significant fraction of CO emission originates from diffuse molecular gas. Quantifying the contribution of diffuse CO-emitting gas is vital for understanding the relation between molecular gas and star formation. We examine the Galactic distribution of two CO-emitting gas components, a high column density component detected in 13CO and 12CO, and...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1601.00937
Arxiv.org
by Meng Gu; Charlie Conroy; Peter Behroozi
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The relation between galaxies and dark matter halos reflects the combined effects of many distinct physical processes. Observations indicate that the $z=0$ stellar mass-halo mass (SMHM) relation has remarkably small scatter in stellar mass at fixed halo mass ($\lesssim$ 0.2 dex) with little dependence on halo mass. We investigate the origins of this scatter by combining N-body simulations with observational constraints on the SMHM relation. We find that at the group and cluster scale ($M_{\rm...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1602.01099
Arxiv.org
by T. Moutard; S. Arnouts; O. Ilbert; J. Coupon; P. Hudelot; D. Vibert; V. Comte; S. Conseil; I. Davidzon; L. Guzzo; A. Llebaria; C. Martin; H. J. McCracken; B. Milliard; G. E. Morrison; D. Schiminovich; M. Treyer; L. Van Werbaeke
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We present observations collected in the CFHTLS-VIPERS region in the ultraviolet (UV) with the GALEX satellite (far and near UV channels) and the near infrared with the CFHT/WIRCam camera ($K_s$-band) over an area of 22 and 27 deg$^2$, respectively. The depth of the photometry was optimized to measure the physical properties (e.g., SFR, stellar masses) of all the galaxies in the VIPERS spectroscopic survey. The large volume explored by VIPERS will enable a unique investigation of the...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1602.05915
Arxiv.org
by S. Duffau; L. Sbordone; A. K. Vivas; C. J. Hansen; M. Zoccali; M. Catelan; D. Minniti; E. K. Grebel
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We present the first detailed chemical abundances for distant RR Lyrae stars members of the Virgo Stellar Stream (VSS), derived from X-Shooter medium-resolution spectra. Sixteen elements from carbon to barium have been measured in six VSS RR Lyrae stars, sampling all main nucleosynthetic channels. For the first time we will be able to compare in detail the chemical evolution of the VSS progenitor with those of Local Group dwarf spheroidal galaxies (LG dSph) as well as the one of the smooth halo.
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1603.07191
Arxiv.org
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We present velocity-resolved maps taken with the Wisconsin H-Alpha Mapper (WHAM) in H{\alpha}, [S II] {\lambda}6716, and [N II] {\lambda}6583 around the well-known O8 III star {\lambda} Ori A (HD 36861) (l = 185{\deg} to 205{\deg}, b = -24{\deg} to -1{\deg}). The integrated intensity (v(LSR) = -80 to +80 km/s), I(H{\alpha}), within WHAM's one-degree beams varies from ~ 190 R near the center to ~ 10 R on the periphery of the nebula where it becomes comparable to foreground and/or background...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1604.03975
Arxiv.org
by Brian Punsly; Cormac Reynolds; Paola Marziani; Christopher P. O'Dea
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This paper reports on the extreme ultraviolet (EUV) spectrum of three low redshift ($z \sim 0.6$) radio loud quasars, 3C 95, 3C 57 and PKS 0405-123. The spectra were obtained with the Cosmic Origins Spectrograph (COS) of the Hubble Space Telescope. The bolometric thermal emission, $L_{bol}$, associated with the accretion flow is a large fraction of the Eddington limit for all of these sources. We estimate the long term time averaged jet power, $\overline{Q}$, for the three sources....
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1604.03631
Arxiv.org
by N. Schneider; S. Bontemps; F. Motte; A. Blazere; Ph. Andre; L. D. Anderson; D. Arzoumanian; F. Comeron; P. Didelon; J. Di Francesco; A. Duarte-Cabral; M. G. Guarcello; M. Hennemann; T. Hill; V. Konyves; A. Marston; V. Minier; K. L. J. Rygl; M. Roellig; A. Roy; L. Spinoglio; P. Tremblin; G. J. White; N. J. Wright
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The radiative feedback of massive stars on molecular clouds creates pillars, globules and other features at the interface between the HII region and molecular cloud. We present here Herschel observations between 70 and 500 micron of the immediate environment of the Cygnus OB2 association, performed within the HOBYS program. All structures were detected based on their appearance at 70 micron, and have been classified as pillars, globules, evaporating gasous globules (EGGs), proplyd-like objects,...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1604.03967
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Observations show that the global deuterium-to-hydrogen ratio (D/H) in the local interstellar medium (ISM) is about 90% of the primordial ratio predicted by big bang nucleosynthesis. The high (D/H)$_{ISM}$ implies that only a small fraction of interstellar gas has been processed through stars, which destroy any deuterium they are born with. Using analytic arguments for one-zone chemical evolution models that include accretion and outflow, I show that the deuterium abundance is tightly coupled...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1604.07434
Arxiv.org
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Self-gravity and stellar feedback are capable of driving turbulence and transporting mass and angular momentum in disk galaxies, but the balance between them is not well understood. In the previous paper in this series, we showed that gravity alone can drive turbulence in galactic disks, regulate their Toomre $Q$ parameters to $\sim$ 1, and transport mass inwards at a rate sufficient to fuel star formation in the centers of present-day galaxies. In this paper we extend our models to include the...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1605.00646
Arxiv.org
by N. Vale Asari; G. Stasińska; C. Morisset; R. Cid Fernandes
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We present BOND, a Bayesian code to simultaneously derive oxygen and nitrogen abundances in giant H II regions. It compares observed emission lines to a grid of photoionization models without assuming any relation between O/H and N/O. Our grid spans a wide range in O/H, N/O and ionization parameter U, and covers different starburst ages and nebular geometries. Varying starburst ages accounts for variations in the ionizing radiation field hardness, which arise due to the ageing of H II regions...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1605.01057
Arxiv.org
by Leah K. Morabito; Adam T. Deller; Huub Röttgering; George Miley; Eskil Varenius; Timothy W. Shimwell; Javier Moldón; Neal Jackson; Raffaella Morganti; Reinout J. van Weeren; J. B. R. Oonk
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The correlation between radio spectral index and redshift has been exploited to discover high redshift radio galaxies, but its underlying cause is unclear. It is crucial to characterise the particle acceleration and loss mechanisms in high redshift radio galaxies to understand why their radio spectral indices are steeper than their local counterparts. Low frequency information on scales of $\sim$1 arcsec are necessary to determine the internal spectral index variation. In this paper we present...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1606.06741
Arxiv.org
by J. R. Allison; M. A. Zwaan; S. W. Duchesne; S. J. Curran
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We present a statistical method for measuring the average HI spin temperature in distant galaxies using the expected detection yields from future wide-field 21cm absorption surveys. As a demonstrative case study we consider a simulated all-southern-sky survey of 2-h per pointing with the Australian Square Kilometre Array Pathfinder for intervening HI absorbers at intermediate cosmological redshifts between $z = 0.4$ and $1$. For example, if such a survey yielded $1000$ absorbers we would infer...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1607.04828
Arxiv.org
by S. P. Trevino-Morales; A. Fuente; A. Sanchez-Monge; P. Pilleri; J. R. Goicoechea; V. Ossenkopf-Okada; E. Roueff; J. R. Rizzo; M. Gerin; O. Berne; J. Cernicharo; M. Gonzalez-Garcia; C. Kramer; S. Garcia-Burillo; J. Pety
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The CO+ reactive ion is thought to be a tracer of the boundary between a HII region and the hot molecular gas. In this study, we present the spatial distribution of the CO+ rotational emission toward the Mon R2 star-forming region. The CO+ emission presents a clumpy ring-like morphology, arising from a narrow dense layer around the HII region. We compare the CO+ distribution with other species present in photon-dominated regions (PDR), such as [CII] 158 mm, H2 S(3) rotational line at 9.3 mm,...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1607.06265
Arxiv.org
by Kai-Xing Lu; Pu Du; Chen Hu; Yan-Rong Li; Zhi-Xiang Zhang; Kai Wang; Ying-Ke Huang; Shao-Lan Bi; Jin-Ming Bai; Luis C. Ho; Jian-Min Wang
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NGC 5548 is the best-observed reverberation-mapped active galactic nucleus with long-term, intensive monitoring. Here we report results from a new observational campaign between January and July, 2015. We measure the centroid time lag of the broad H$\beta$ emission line with respect to the 5100 \AA continuum and obtain $\tau_{\rm cent} = 7.20^{+1.33}_{-0.35}$ days in the rest frame. This yields a black hole mass of $M_{\bullet}=8.71^{+3.21}_{-2.61} $x$ 10^{7}M_{\odot}$ using a broad H$\beta$...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1607.08060
Arxiv.org
by Jack F. Gallimore; Moshe Elitzur; Roberto Maiolino; Alessandro Marconi; Christopher P. O'Dea; Dieter Lutz; Stefi A. Baum; Robert Nikutta; C. M. V. Impellizzeri; Richard Davies; Amy E. Kimball; Eleonora Sani
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We have detected in ALMA observations CO J = 6 - 5 emission from the nucleus of the Seyfert galaxy NGC 1068. The low-velocity (up to +/- 70 km/s relative to systemic) CO emission resolves into a 12x7 pc structure, roughly aligned with the nuclear radio source. Higher-velocity emission (up to +/- 400 km/s) is consistent with a bipolar outflow in a direction nearly perpendicular (roughly 80 degrees) to the nuclear disk. The position-velocity diagram shows that in addition to the outflow, the...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1608.02210
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Radiation feedback from stellar clusters is expected to play a key role in setting the rate and efficiency of star formation in giant molecular clouds (GMCs). To investigate how radiation forces influence realistic turbulent systems, we have conducted a series of numerical simulations employing the {\it Hyperion} radiation hydrodynamics solver, considering the regime that is optically thick to ultraviolet (UV) and optically thin to infrared (IR) radiation. Our model clouds cover initial surface...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1608.04469
Arxiv.org
by Satoshi Hamano; Naoto Kobayashi; Sohei Kondo; Yuji Ikeda; Kenshi Nakanishi; Chikako Yasui; Misaki Mizumoto; Noriyuki Matsunaga; Kei Fukue; Hiroyuki Mito; Ryo Yamamoto; Natsuko Izumi; Tetsuya Nakaoka; Takafumi Kawanishi; Ayaka Kitano; Shogo Otsubo; Masaomi Kinoshita; Hitomi Kobayashi; Hideyo Kawakita
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We present a comprehensive survey of diffuse interstellar bands (DIBs) in $0.91-1.32\mu$m with a newly-developed near-infrared (NIR) spectrograph, WINERED, mounted on the Araki 1.3 m Telescope in Japan. We obtained high-resolution ($R=28,300$) spectra of 25 early-type stars with color excesses of $0.07
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1412.3578
Arxiv.org
by Joanna E. Barnes; Kenneth Wood; Alex S. Hill; L. Matthew Haffner
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Using three dimensional Monte Carlo radiation transfer models of photoionisation and dust scattering, we explore different components of the widespread diffuse H$\alpha$ emission observed in the interstellar medium of the Milky Way and other galaxies. We investigate the relative contributions of H$\alpha$ from recombination emission in ionised gas and H$\alpha$ that originates in H{\sc ii} regions near the Galactic midplane and scatters off high altitude dust in the diffuse interstellar medium....
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1411.5895
Arxiv.org
by Z. Zheng; D. Thilker; T. Heckman; G. Meurer; W. Burgett; K. Chambers; M. Huber; N. Kaiser; E. Magnier; N. Metcalfe; P. Price; J. Tonry; R. Wainscoat; C. Waters
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We present the results of an analysis of Pan-STARRS1 Medium Deep Survey multi-band (g,r,i,z,y) images of a sample of 698 low-redshift disk galaxies that span broad ranges in stellar mass, star-formation rate, and bulge/disk ratio. We use population synthesis SED fitting techniques to explore the radial distribution of the light, color, surface mass density, mass/light ratio, and age of the stellar populations. We characterize the structure and stellar content of the galaxy disks out to radii of...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1412.3209