We use a sample of 559 disc galaxies extracted from the eXtended GALEX Arecibo SDSS Survey (xGASS) to study the connection between baryonic angular momentum, mass and atomic gas fraction in the local Universe. Baryonic angular momenta are determined by combining HI and H$_{2}$ integrated profiles with two-dimensional stellar mass surface density profiles. In line with previous work, we confirm that specific angular momentum and atomic gas fraction are tightly correlated, but we find a larger scatter than previously observed. This is most likely due to the wider range of galaxy properties covered by our sample. We compare our findings with the predictions of the analytical stability model developed by Obreschkow et al. and find that, while the model provides a very good first-order approximation for the connection between baryonic angular momentum, mass and gas fraction, it does not fully match our data. Specifically, we find that at fixed baryonic mass, the dependence of specific angular momentum on gas fraction is significantly weaker, and at fixed gas fraction, the slope of the angular momentum vs. mass relation is shallower than what was predicted by the model. The reasons behind this tension remain unclear, but we speculate that multiple factors may simultaneously play a role, all related to the fact that the model is not able to encapsulate the full diversity of galaxy properties in our sample.
We present a detailed study of the stellar mass vs. specific angular momentum (AM) relation (Fall relation) for a representative sample of 564 nearby galaxies in the eXtended GALEX Arecibo SDSS Survey (xGASS). We focus on the dependence of the Fall relation's slope on galaxy type and the galaxy properties regulating its scatter. Stellar specific AM is determined by combining single-dish H{\sc i} velocity widths and stellar mass profiles for all H{\sc i} detections in the xGASS sample. At fixed morphology (or bulge-to-total ratio), we find that the power law slope of the Fall relation is consis…
We use the extended GALEX Arecibo SDSS Survey (xGASS) to quantify the relationship between atomic hydrogen (HI) reservoir and current star formation rate (SFR) for central disk galaxies. This is primarily motivated by recent claims for the existence, in this sample, of a large population of passive disks harbouring HI reservoirs as large as those observed in main sequence galaxies. Across the stellar mass range 10$^{9}<$M$_{*}$/M$_{\odot}<$10$^{11}$, we practically find no passive ($\gtrsim$2$σ$ below the star-forming main sequence) disk galaxies with HI reservoirs comparable to those typical …
We present the extended GALEX Arecibo SDSS Survey (xGASS), a gas fraction-limited census of the atomic (HI) gas content of 1179 galaxies selected only by stellar mass ($M_\star =10^{9}-10^{11.5} M_\odot$) and redshift ($0.01<z<0.05$). This includes new Arecibo observations of 208 galaxies, for which we release catalogs and HI spectra. In addition to extending the GASS HI scaling relations by one decade in stellar mass, we quantify total (atomic+molecular) cold gas fractions and molecular-to-atomic gas mass ratios, $R_{mol}$, for the subset of 477 galaxies observed with the IRAM 30 m telescope.…
We present a structural decomposition analysis of the galaxies in the extended GALEX Arecibo SDSS Survey (xGASS) using (gri) images from the Sloan Digital Sky Survey. Utilising the 2D Bayesian light profile fitting code ProFit, we fit single- and double-component models taking advantage of a robust Markov chain Monte Carlo optimisation algorithm in which we assume a Sersic profile for single-component models and a combination of a Sersic bulge and near-exponential disc (0.5 < n < 1.5) for double-component models. We investigate the effect of bulges on the atomic hydrogen (HI) content in galaxi…
We use deep HI observations obtained as part of the extended GALEX Arecibo SDSS survey (xGASS) to study the cold gas properties of central galaxies across environments. We find that, below stellar masses of 10^10.2 Msun, central galaxies in groups have an average atomic hydrogen gas fraction ~0.3dex higher than those in isolation at the same stellar mass. At these stellar masses, group central galaxies are usually found in small groups of N=2 members. The higher HI content in these low mass group central galaxies is mirrored by their higher average star formation activity and molecular hydroge…
Context. The xGASS and xCOLD GASS surveys have measured the atomic (HI) and molecular gas (H2) content of a large and representative sample of nearby galaxies (redshift range of 0.01 $\lt$ z $\lt$ 0.05). Aims. We present optical longslit spectra for a subset of the xGASS and xCOLD GASS galaxies to investigate the correlation between radial metallicity profiles and cold gas content. In addition to data from Moran et al. (2012), this paper presents new optical spectra for 27 galaxies in the stellar mass range of 9.0 $\leq$ log Mstar/Msun $\leq$ 10.0. Methods. The longslit spectra were taken alon…
We present a detailed assessment of the global atomic hydrogen gas fraction in a sample of post-merger galaxies identified in the Sloan Digital Sky Survey (SDSS). Archival HI measurements of 47 targets are combined with new Arecibo observations of a further 51 galaxies. The stellar mass range of the post-merger sample, our observing strategy, detection thresholds and data analysis procedures replicate those of the extended GALEX Arecibo SDSS Survey (xGASS) which can therefore be used as a control sample. Our principal results are: 1) The post-merger sample shows a ~50 per cent higher HI detect…
Observations have revealed that disturbances in the cold neutral atomic hydrogen (HI) in galaxies are ubiquitous, but the reasons for these disturbances remain unclear. While some studies suggest that asymmetries in integrated HI spectra (global HI asymmetry) are higher in HI-rich systems, others claim that they are preferentially found in HI-poor galaxies. In this work, we utilise the ALFALFA and xGASS surveys, plus a sample of post-merger galaxies, to clarify the link between global HI asymmetry and the gas properties of galaxies. Focusing on star-forming galaxies in ALFALFA, we find that el…
Tracing Quenching in Nearby Galaxies Through Inner Surface Mass Density and Cold Gas Content
Orange Coast College（橙海岸学院）；California Institute of Technology（加州理工学院）；California State University, Long Beach（加州州立大学长滩分校）；University of California, Irvine（加州大学尔湾分校）
The feedback from an active galactic nucleus (AGN) is frequently invoked as a mechanism through which gas can be heated or removed from a galaxy. However, gas fraction measurements in AGN hosts have yielded mixed support for this scenario. Here, we re-visit the assessment of fgas (=MHI/M*) in z<0.05 AGN hosts in the Sloan Digital Sky Survey (SDSS) using two complementary techniques. First, we investigate fgas for 75 AGN host galaxies in the extended GALEX Arecibo SDSS Survey (xGASS), whose atomic gas fractions are complete to a few percent. Second, we construct HI spectral stacks of 1562 AGN f…
We investigate the influence of environment on the cold-gas properties of galaxies at z=0 within the TNG100 cosmological, magnetohydrodynamic simulation, part of the IllustrisTNG suite. We extend previous post-processing methods for breaking gas cells into their atomic and molecular phases, and build detailed mocks to comprehensively compare to the latest surveys of atomic hydrogen (HI) in nearby galaxies, namely ALFALFA and xGASS. We use TNG100 to explore the HI content, star formation activity, and angular momentum of satellite galaxies, each as a function of environment, and find that satel…
We present an analysis of the radial profiles of a sample of 43 HI-flux selected spiral galaxies from the Nearby Galaxies Legacy Survey (NGLS) with resolved James Clerk Maxwell Telescope (JCMT) CO $J=3-2$ and/or Very Large Array (VLA) HI maps. Comparing the Virgo and non-Virgo populations, we confirm that the HI disks are truncated in the Virgo sample, even for these relatively HI-rich galaxies. On the other hand, the H$_{2}$ distribution is enhanced for Virgo galaxies near their centres, resulting in higher H$_{2}$ to HI ratios and steeper H$_{2}$ and total gas radial profiles. This is likely…
We investigate the correlation between CO and HI emission in 18 nearby galaxies from the CARMA Survey Toward IR-Bright Nearby Galaxies (STING) at sub-kpc and kpc scales. Our sample, spanning a wide range in stellar mass and metallicity, reveals evidence for a metallicity dependence of the HI column density measured in regions exhibiting CO emission. Such a dependence is predicted by the equilibrium model of McKee & Krumholz, which balances H_2 formation and dissociation. The observed HI column density is often smaller than predicted by the model, an effect we attribute to unresolved clumping, …
We combine dust, atomic (HI) and molecular (H$_{2}$) hydrogen mass measurements for 176 galaxies in the Herschel Reference Survey to investigate the effect of environment on the gas-to-dust mass ($M_{\rm gas}/M_{\rm dust}$) ratio of nearby galaxies. We find that, at fixed stellar mass, the average $M_{\rm gas}/M_{\rm dust}$ ratio varies by no more than a factor of $\sim$2 when moving from field to cluster galaxies, with Virgo galaxies being slightly more dust rich (per unit of gas) than isolated systems. Remarkably, once the molecular and atomic hydrogen phases are investigated separately, we …
We derive total (atomic + molecular) hydrogen densities in giant molecular clouds (GMCs) in the nearby spiral galaxy M33 using a method that views the atomic hydrogen near regions of recent star formation as the product of photodissociation. Far-UV photons emanating from a nearby OB association produce a layer of atomic hydrogen on the surfaces of nearby GMCs. Our approach provides an estimate of the total hydrogen density in these GMCs from observations of the excess far-UV emission that reaches the GMC from the OB association, and the excess 21-cm radio HI emission produced after these far-U…
Active galactic nucleus (AGN) feedback is postulated as a key mechanism for regulating star formation within galaxies. Studying the physical properties of the outflowing gas from AGN is thus crucial for understanding the co-evolution of galaxies and supermassive black holes. Here we report 55 pc resolution ALMA neutral atomic carbon [CI] $^3P_1\text{-}^3P_0$ observations toward the central 1 kpc of the nearby type-2 Seyfert galaxy NGC 1068, supplemented by 55 pc resolution CO($J=1\text{-}0$) observations. We find that [CI] emission within the central kpc is strongly enhanced by a factor of $>$…
We analyzed near-infrared data of the nearby galaxy IC5063 taken with the Very Large Telescope SINFONI instrument. IC5063 is an elliptical galaxy that has a radio jet nearly aligned with the major axis of a gas disk in its center. The data reveal multiple signatures of molecular and atomic gas that has been kinematically distorted by the passage of the jet plasma or cocoon within an area of ~1 kpc^2. Concrete evidence that the interaction of the jet with the gas causes the gas to accelerate comes from the detection of outflows in four different regions along the jet trail: near the two radio l…
Mass outflow rates and loading factors are typically used to infer the quenching potential of galactic-scale outflows. However, these generally rely on observations of a single gas phase which can severely underestimate the total ejected gas mass. To address this, we use observations of high mass ($\geqslant$10$^{10}$ M$_{\odot}$), normal star-forming galaxies at $z\sim$0 from the MaNGA, xCOLD GASS, xGASS and ALFALFA surveys and a stacking of NaD, H$α$, CO(1-0) and HI 21cm tracers with the aim of placing constraints on an average, total mass outflow rate and loading factor. We find detections …
Atomic carbon (CI) has been proposed to be a global tracer of the molecular gas as a substitute for CO, however, its utility remains unproven. To evaluate the suitability of CI as the tracer, we performed [CI]$(^3P_1-^3P_0)$ (hereinafter [CI](1-0)) mapping observations of the northern part of the nearby spiral galaxy M83 with the ASTE telescope and compared the distributions of [CI](1-0) with CO lines (CO(1-0), CO(3-2), and $^{13}$CO(1-0)), HI, and infrared (IR) emission (70, 160, and 250$ μ$m). The [CI](1-0) distribution in the central region is similar to that of the CO lines, whereas [CI](1…
University of Alberta（阿尔伯塔大学）；Ludwig Maximilian University of Munich (LMU)（慕尼黑大学）；The University of Western Australia（西澳大学）；University of the Witwatersrand（威特沃特斯兰德大学）；NASA Ames Research Center（美国国家航空航天局艾姆斯研究中心）；Cardiff University（卡迪夫大学）；University Catholic of Lyon（里昂天主教大学）
We determine the cosmic abundance of molecular hydrogen (H2) in the local universe from the xCOLD GASS survey. To constrain the H2 mass function at low masses and correct for the effect of the lower stellar mass limit of 10^9 Msun in the xCOLD GASS survey, we use an empirical approach based on an observed scaling relation between star formation rate and gas mass. We also constrain the HI and HI+H2 mass functions using the xGASS survey, and compare it to the HI mass function from the ALFALFA survey. We find the cosmic abundance of molecular gas in the local Universe to be Omega_H2=(5.34+/-0.47)…
The GMRT archive atomic gas survey -- III. Comparative Study of Dark Matter Halos in Nearby Galaxies
Indian Institute of Science（印度科学研究所）；Indian Institute of Astrophysics（印度天体物理研究所）；Max-Planck-Institut für Radioastronomie (MPIfR)（马克斯·普朗克射电天文研究所）；Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences（保加利亚科学院天文学与国家天文台）；New Mexico Institute of Mining and Technology（新墨西哥矿业理工学院）；Indian Institute of Technology Indore（印度印多尔理工学院）；ASTRON – Netherlands Institute for Radio Astronomy（荷兰射电天文研究所）；National Centre for Radio Astrophysics (NCRA–TIFR)（国家射电天体物理学中心）
Stellar feedback is fundamental to the modeling of galaxy evolution as it drives turbulence and outflows in galaxies. Understanding the timescales involved are critical for constraining the impact of stellar feedback on the interstellar medium (ISM). We analyzed the resolved star formation histories along with the spatial distribution and kinematics of the atomic and ionized gas of four nearby star-forming dwarf galaxies (NGC 4068, NGC 4163, NGC 6789, UGC 9128) to determine the timescales over which stellar feedback drives turbulence. The four galaxies are within 5 Mpc and have a range of prop…
It is well known that gas in galaxy discs is highly turbulent, but there is much debate on which mechanism can energetically maintain this turbulence. Among the possible candidates, supernova (SN) explosions are likely the primary drivers but doubts remain on whether they can be sufficient in regions of moderate star formation activity, in particular in the outer parts of discs. In this paper, we measure the SN efficiency $η$, namely the fraction of the total SN energy needed to sustain turbulence in galaxies, and verify that SNe can indeed be the sole driving mechanism. The key novelty of our…
We present the results of a multiwavelength study of the nearby dwarf galaxy DDO 53 - a relatively isolated member of the M 81 group. We analyse the atomic and ionised gas kinematics (based on the observations with Fabry-Perot interferometer in H$α$ line and archival data in HI 21 cm line), distribution, excitation and oxygen abundance of the ionised gas (based on the long-slit and integral-field spectroscopy and on imaging with narrow-band filters), and their relation with the young massive stars (based on archival HST data). We detect a faint 2-kpc sized supershell of ionised gas surrounding…
In order to quantify the relationship between gas accretion and star formation, we analyse a sample of 29 nearby galaxies from the WHISP survey which contains galaxies with and without evidence for recent gas accretion. We compare combined radial profiles of FUV (GALEX) and IR 24 μm (Spitzer) characterizing distributions of recent star formation with radial profiles of CO (IRAM, BIMA, or CARMA) and HI (WSRT) tracing molecular and atomic gas contents to examine star formation efficiencies in symmetric (quiescent), asymmetric (accreting), and interacting (tidally disturbed) galaxies. In addition…
The global Schmidt law of star formation provides a power-law relation between the surface densities of star-formation rate (SFR) and gas, and successfully explains plausible scenarios of galaxy formation and evolution. However, star formation being a multi-scale process, requires spatially-resolved analysis for a better understanding of the physics of star formation. It has been shown that the removal of a diffuse background from SFR tracers, such as H$α$, far-ultraviolet (FUV), infrared, leads to an increase in the slope of the sub-galactic Schmidt relation. We reinvestigate the local Schmid…
Interferometric observations of HI in galaxies played a pivotal role in studies of nearby galaxies. Compared to single-dish observation, it provides resolved distribution of gas in galaxies with unprecedented resolution. Several extensive HI surveys of nearby galaxies have been performed in the past; however, most of them consist of less than 100 galaxies due to individual efforts. On the other hand, present-day archives of the radio telescopes include data for at least several hundred galaxies. To utilize these data sets to their full potential, we construct a sample including all galaxies ob…
We present a mass-temperature profile of gas within the central 10 kpc of a small sample of cool core clusters. The mass of the hottest gas phases, at 1.5 and 0.7 keV, is determined from X-ray spectra from the XMM Reflection Grating Spectrometers. The masses of the partially ionised atomic and the molecular phases are obtained from published H$α$ and CO measurements. We find that the mass of gas at 0.7 keV in a cluster is remarkably similar to that of the molecular gas. Assuming pressure equilibrium between the phases, this means that they occupy volumes differing by $10^5$. The molecular gas …
New deep VLA D array HI observations of the highly inclined nearby spiral galaxy NGC 2683 are presented. Archival C array data were processed and added to the new observations. To investigate the 3D structure of the atomic gas disk, we made different 3D models for which we produced model HI data cubes. The main ingredients of our best-fit model are (i) a thin disk inclined by 80 degrees; (ii) a crude approximation of a spiral and/or bar structure by an elliptical surface density distribution of the gas disk; (iii) a slight warp in inclination; (iv) an exponential flare; and (v) a low surface-d…
We investigate the metallicity dependence of HI surface densities in star-forming regions along many lines of sight within 70 nearby galaxies, probing kpc to 50 pc scales. We employ HI, SFR, stellar mass, and metallicity (gradient) measurements from the literature, spanning a wide range (5 dex) in stellar and gas mass and (1.6 dex) in metallicity. We consider metallicities as observed, or rescaled to match the mass-metallicity relation determined for SDSS galaxies. At intermediate to high metallicities (0.3-2 times solar), we find that the HI surface densities saturate at sufficiently large to…
A galaxy's morphological features encode details about its gas content, star formation history, and feedback processes, which play important roles in regulating its growth and evolution. We use deep convolutional neural networks (CNNs) to learn a galaxy's optical morphological information in order to estimate its neutral atomic hydrogen (HI) content directly from SDSS $gri$ image cutouts. We are able to accurately predict a galaxy's logarithmic HI mass fraction, $\mathcal{M} \equiv \log(M_{\rm HI}/M_\star)$, by training a CNN on galaxies in the ALFALFA 40% sample. Using pattern recognition (PR…
We use the IRAM HERACLES survey to study CO emission from 33 nearby spiral galaxies down to very low intensities. Using atomic hydrogen (HI) data, mostly from THINGS, we predict the local mean CO velocity from the mean HI velocity. By renormalizing the CO velocity axis so that zero corresponds to the local mean HI velocity we are able to stack spectra coherently over large regions as function of radius. This enables us to measure CO intensities with high significance as low as Ico = 0.3 K km/s (H2_SD = 1 Msun/pc2), an improvement of about one order of magnitude over previous studies. We detect…
The study of gas-dust interactions occurring in the interstellar medium of a galaxy is essential for understanding various physical processes taking place within it. A comparison of such events at different locations corresponding to diverse astrophysical environments provides more insight into the star-formation as well as dust destruction conditions and time-scales. We present a case study for two galaxies: NGC 3184 and NGC 7793, which are typical examples of a `grand design spiral' and a `flocculent spiral', respectively. We investigate the gas-dust correlations at various spatially resolve…
We aim to characterize the relationship between dust properties. We also aim to provide equations to estimate accurate dust properties from limited observational datasets. We assemble a sample of 1,630 nearby (z<0.1) galaxies-over a large range of Mstar, SFR - with multi-wavelength observations available from wise, iras, planck and/or SCUBA. The characterization of dust emission comes from SED fitting using Draine & Li dust models, which we parametrize using two components (warm and cold ). The subsample of these galaxies with global measurements of CO and/or HI are used to explore the molecul…
We have estimated the magnetic field strengths of a sample of seven galaxies using their non-thermal synchrotron radio emission at metre wavelengths, and assuming energy equipartition between magnetic fields and cosmic ray particles. Spatially resolved star formation rates (SFR) were estimated for the seven galaxies along with five galaxies studied previously. For the combined sample of twelve galaxies, the equipartition magnetic fields (B$_\textrm{eq}$) are correlated with the SFR surface densities ($Σ_\textrm{SFR}$) at sub-kpc scales with B$_\textrm{eq}$ $\propto$ $Σ_\textrm{SFR}^ {0.31\pm0.…
Neutral Hydrogen in the Shapley Supercluster Core I: Environmental Effects on Gas Content and Galaxy Evolution
Rhodes University（罗德斯大学）；INAF–Istituto di Radioastronomia（意大利国家天体物理研究所射电天文研究所）；INAF–Osservatorio Astronomico di Capodimonte（意大利国家天体物理研究所卡波迪蒙特天文台）；South African Radio Astronomy Observatory（南非射电天文观测台）
The study of 21cm line observations of atomic hydrogen allows detailed insight into the kinematics of spiral galaxies. We use sensitive high-resolution VLA data from The HI Nearby Galaxy Survey (THINGS) to search for radial gas flows primarily in the outer parts (up to $3\times r_{25}$) of ten nearby spiral galaxies. Inflows are expected to replenish the gas reservoir and fuel star formation under the assumption that galaxies evolve approximately in steady state. We carry out a detailed investigation of existing tilted ring fitting schemes and discover systematics that can hamper their ability…
We present EMPIRE, an IRAM 30-m large program that mapped $λ= 3{-}4$ mm dense gas tracers at $\sim 1{-}2\,$kpc resolution across the whole star-forming disk of nine nearby, massive, spiral galaxies. We describe the EMPIRE observing and reduction strategies and show new whole-galaxy maps of HCN(1-0), HCO$^+$(1-0), HNC(1-0) and CO(1-0). We explore how the HCN-to-CO and IR-to-HCN ratios, observational proxies for the dense gas fraction and dense gas star formation efficiency, depend on host galaxy and local environment. We find that the fraction of dense gas correlates with stellar surface densit…
We investigate the physical conditions of the gas, atomic and molecular, in the filaments in the context of Photo-Dissociation Regions (PDRs) using the KOSMA-PDR mode of clumpy clouds. We also compare the [CII] vs. [NII] integrated intensity predictions in Abel et al. 2005 for HII regions and adjacent PDRs in the Galactic disk, and check for their applicability under the extreme physical conditions present in the GC. Our preliminary results show that observed integrated intensities are well reproduced by the PDR model. The gas is exposed to a relatively low Far-UV field between 10^2 - 10^3 Dra…
JWST observations of polycyclic aromatic hydrocarbon (PAH) emission provide some of the deepest and highest resolution views of the cold interstellar medium (ISM) in nearby galaxies. If PAHs are well mixed with the atomic and molecular gas and illuminated by the average diffuse interstellar radiation field, PAH emission may provide an approximately linear, high resolution, high sensitivity tracer of diffuse gas surface density. We present a pilot study that explores using PAH emission in this way based on MIRI observations of IC 5332, NGC 628, NGC 1365, and NGC 7496 from the PHANGS-JWST Treasu…
We compare the observed turbulent pressure in molecular gas, $P_\mathrm{turb}$, to the required pressure for the interstellar gas to stay in equilibrium in the gravitational potential of a galaxy, $P_\mathrm{DE}$. To do this, we combine arcsecond resolution CO data from PHANGS-ALMA with multi-wavelength data that traces the atomic gas, stellar structure, and star formation rate (SFR) for 28 nearby star-forming galaxies. We find that $P_\mathrm{turb}$ correlates with, but almost always exceeds the estimated $P_\mathrm{DE}$ on kiloparsec scales. This indicates that the molecular gas is over-pres…
Using a simple model of photodissociated atomic hydrogen on a galactic scale, it is possible to derive total hydrogen volume densities. These densities, obtained through a combination of atomic hydrogen, far-ultraviolet and metallicity data, provide an independent probe of the combined atomic and molecular hydrogen gas in galactic disks. We present a new, flexible and fully automated procedure using this simple model. This automated method will allow us to take full advantage of a host of available data on galaxies in order to calculate total hydrogen volume densities of giant molecular clouds…
The Antlia Cluster is a nearby, dynamically young structure, and its proximity provides a valuable opportunity for detailed study of galaxy and group accretion onto clusters. We present a deep HI mosaic completed as part of spectral line commissioning of the Karoo Array Telescope (KAT-7), and identify infrared counterparts from the WISE extended source catalog to study neutral atomic gas content and star formation within the cluster. We detect 37 cluster members out to a radius of ~0.9 Mpc with M_HI > 5x10^7 M_Sun. Of these, 35 are new HI detections, 27 do not have previous spectroscopic redsh…
The environment of S187, a nearby H II region (1.4$\pm$0.3 kpc), is analyzed. A surrounding shell has been studied in the H I line, molecular lines, and also in infrared and radio continua. We report the first evidence of a clumpy HI environment in its photodissociation region. A background radio galaxy enables the estimation of the properties of cold atomic gas. The estimated atomic mass fraction of the shell is $\sim$260~M$_{\odot}$, the median spin temperature is $\sim$50~K, the shell size is $\sim$4 pc with typical wall width around 0.2 pc. The atomic shell consists of $\sim$100 fragments.…
The relationships between atomic and molecular hydrogen and dust of various sizes in extragalactic star-forming regions are considered, based on observational data from the Spitzer and Herschel infrared space telescopes, the Very Large Array (atomic hydrogen emission) and IRAM (CO emission). The source sample consists of approximately 300 star-forming regions in 11 nearby galaxies. Aperture photometry has been applied to measure the fluxes in eight infrared bands (3.6, 4.5, 5.8, 8, 24, 70, 100, and 160$μ$m), the atomic hydrogen (21cm) line and CO (2--1) lines. The parameters of the dust in the…
The Multi-phase HI of the Milky Way and Nearby Galaxies
Laboratoire de Physique de l’Ecole normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris-Diderot, Sorbonne Paris Cité, Observatoire de Paris（巴黎高等师范学院物理实验室，ENS，PSL大学，CNRS，索邦大学，巴黎第七大学，索邦巴黎城，巴黎天文台）；Macquarie University（麦考瑞大学）；Indian Institute of Technology Indore（印度理工学院印多尔分校）；Indian Institute of Astrophysics（印度天体物理研究所）；Stanford University（斯坦福大学）；University of Tasmania（塔斯马尼亚大学）；Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM（巴黎萨克雷大学，巴黎西岱大学，CEA，CNRS，AIM）；University of British Columbia（不列颠哥伦比亚大学）；National Research Council Canada（加拿大国家研究委员会）；Korea Astronomy and Space Science Institute（韩国天文学与空间科学研究所）；University of Science and Technology（科学技术大学）；The Australian National University（澳大利亚国立大学）；Space Telescope Science Institute（太空望远镜科学研究所）；University of Wisconsin–Madison（威斯康星大学麦迪逊分校）；Indiana University（印第安纳大学）；Columbia University（哥伦比亚大学）；Indian Institute of Science（印度科学学院）；California State University, Chico（加州州立大学奇科分校）
We present CO velocity fields and rotation curves for a sample of nearby galaxies, based on data from the HERACLES survey. We combine our data with literature THINGS, SINGS and KINGFISH results to provide a comprehensive sample of mass models of disk galaxies inclusive of molecular gas. We compare the kinematics of the molecular (CO from HERACLES) and atomic (${\rm H{\scriptstyle I}}$ from THINGS) gas distributions to determine the extent to which CO may be used to probe the dynamics in the inner part of galaxies. In general, we find good agreement between the CO and ${\rm H{\scriptstyle I}}$ …
