- ID:
- ivo://CDS.VizieR/J/A+A/553/A91
- Title:
- Halpha3 survey of Virgo and Coma galaxies
- Short Name:
- J/A+A/553/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the galaxy structural parameters from H{alpha}3, an H{alpha} narrow-band imaging follow-up survey of ~800 galaxies selected from the HI Arecibo Legacy Fast ALFA Survey (ALFALFA) in the Local Supercluster, including the Virgo cluster, and in the Coma Supercluster. Taking advantage of H{alpha}3 which provides the complete census of the recent star-forming, HI-rich galaxies in the local universe, we aim to investigate the structural parameters of both the young (<10Myr) and the old (>1Gyr) stellar populations. By comparing the sizes of these stellar components we investigated the spatial scale on which galaxies are growing at the present cosmological epoch and the role of the environment in quenching the star-formation activity. We computed the concentration, asymmetry, and clumpiness (CAS) structural parameters both for recently born and old stars. To quantify the sizes we computed half-light radii and a new parameter dubbed EW/r based on the half-light radius of the H{alpha} Equivalent Width map. To highlight the environmental perturbation, we adopt an updated calibration of the HI-deficiency parameter that we use to divide the sample in unperturbed and perturbed galaxies. The concentration index computed in the r band depends on the stellar mass and on the Hubble type, these variables being related since most massive galaxies are bulge dominated thus most concentrated. Going toward later spirals and irregulars both the concentration index and the mass decrease along with the bulge-to-disk ratio. Blue Compact dwarfs represent an exception since they have similar mass but they are more concentrated than dwarf irregulars. The asymmetry and the clumpiness increase along the spiral sequence up to Sc-Sd but they decrease going toward dwarfs whose light distribution is smooth and more symmetric. When measured on H{alpha} images, the CAS parameters do not exhibit obvious correlations with Hubble type. Irrespective of whether we used the ratio between effective radii or the EW/r parameter, we found that the concentration index is the main parameter that describes the current growth of isolated galaxies but, for a fixed concentration, the stellar mass plays a second order role. At the present epoch, massive galaxies are growing inside-out, conversely the dwarfs are growing on the scale of their already assembled mass.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/397
- Title:
- HAPLESS galaxies sample
- Short Name:
- J/MNRAS/452/397
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the properties of the first 250 {mu}m blind sample of nearby galaxies (15<D<46Mpc) containing 42 objects from the Herschel Astrophysical Terahertz Large Area Survey. Herschel's sensitivity probes the faint end of the dust luminosity function for the first time, spanning a range of stellar mass (7.4<M*<11.3log10M_{sun}_), star formation activity (-11.8<SSFR<-8.9log10yr^-1^), gas fraction (3-96 per cent), and colour (0.6<FUV-K_S_<7.0mag). The median cold dust temperature is 14.6K, colder than in the Herschel Reference Survey (18.5K) and Planck Early Release Compact Source Catalogue (17.7K). The mean dust-to-stellar mass ratio in our sample is higher than these surveys by factors of 3.7 and 1.8, with a dust mass volume density of (3.7+/-0.7)x10^5^M_{sun}_/Mpc^3^. Counter-intuitively, we find that the more dust rich a galaxy, the lower its UV attenuation. Over half of our dust-selected sample are very blue in FUV-K_S_ colour, with irregular and/or highly flocculent morphology; these galaxies account for only 6 per cent of the sample's stellar mass but contain over 35 per cent of the dust mass. They are the most actively star-forming galaxies in the sample, with the highest gas fractions and lowest UV attenuation. They also appear to be in an early stage of converting their gas into stars, providing valuable insights into the chemical evolution of young galaxies.
- ID:
- ivo://CDS.VizieR/VIII/7A
- Title:
- Hat Creek High-Latitude H I Survey
- Short Name:
- VIII/7A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This survey consists of H I 21-cm spectra covering the entire northern sky with absolute Galactic latitude |b|>10 degrees and declination dec>-30degrees. The observations were made with the Hat Creek 85-foot telescope between 1968 and 1970. The individual spectra were obtained with a bank of 100 filters covering the velocity range from -92km/s to +75km/s. The velocity resolution was 2 km/sec (except at the ends of the spectra) and the beamwidth was 36arcmin. The spacing between points observed on the sky is (0.3deg/cosb) in Galactic longitude and (0.6deg) in Galactic latitude. A FITS version of the survey was derived at the Astrophysics Data Facility (NASA/GSFC) from the original catalog of spectra. The approximately 130,000 good spectra in the catalog (i.e., those with status code 1 and which have flat baselines) were interpolated to a uniform channel width in frequency, shifted as appropriate to take into account the proper central velocities, then interpolated onto a regular grid in Galactic coordinates. For the latter interpolation, the cos(b) corrections for longitude offsets were taken into account; no interpolation was done across gaps in coverage greater than 2 deg. Latitude-velocity slices were written in FITS format for each 30 arcmin of longitude. Separate files were written for the negative latitude (b < -10 deg ) and positive latitude (b > 10 deg) ranges. Slices containing no spectra, primarily negative latitude spectra in the fourth Galactic quadrant, were not written. A longitude-latitude map, integrated over all velocities, was also written in FITS format to illustrate the coverage of the individual latitude-velocity slices.
- ID:
- ivo://CDS.VizieR/J/MNRAS/394/1857
- Title:
- H_2_/HI ratio in galaxies
- Short Name:
- J/MNRAS/394/1857
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We revisit the mass ratio {eta}_galaxy_ between molecular hydrogen (H2) and atomic hydrogen (HI) in different galaxies from a phenomenological and theoretical viewpoint.
- ID:
- ivo://CDS.VizieR/J/A+A/575/A44
- Title:
- HI absorption in flux-selected radio AGNs
- Short Name:
- J/A+A/575/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the HI 21cm absorption in a sample of 101 flux-selected radio AGN (S_1.4GHz_>50mJy) observed with the Westerbork Synthesis Radio Telescope (WSRT). We detect HI absorption in 32 objects (30% of the sample). In a previous paper, we performed a spectral stacking analysis on the radio sources, while here we characterize the absorption spectra of the individual detections using the recently presented busy function. The HI absorption spectra show a broad variety of widths, shapes, and kinematical properties. The full width half maximum (FWHM) of the busy function fits of the detected HI lines lies in the range 32km/s<FWHM<570km/s, whereas the full width at 20% of the peak absorption (FW20) lies in the range 63km/s<FW20<825km/s. The width and asymmetry of the profiles allows us to identify three groups: narrow lines (FWHM<100km/s), intermediate widths (100km/s<FWHM<200km/s), and broad profiles (FWHM>200km/s). We study the kinematical and radio source properties of each group, with the goal of identifying different morphological structures of HI. Narrow lines mostly lie at the systemic velocity and are likely produced by regularly rotating HI disks or gas clouds. More HI disks can be present among galaxies with lines of intermediate widths; however, the HI in these sources is more unsettled. We study the asymmetry parameter and blueshift/redshift distribution of the lines as a function of their width. We find a trend for which narrow profiles are also symmetric, while broad lines are the most asymmetric. Among the broadest lines, more lines appear blueshifted than redshifted, similarly to what was found by previous studies. Interestingly, symmetric broad lines are absent from the sample. We argue that if a profile is broad, it is also asymmetric and shifted relative to the systemic velocity because it is tracing unsettled HI gas. In particular, besides three of the broadest (up to FW20=825km/s) detections, which are associated with gas-rich mergers, we find three new cases of profiles with blueshifted broad wings (with FW20>500km/s) in high radio power AGN. These detections are good candidates for being HI outflows. Together with the known cases of outflows already included in the sample (3C 293 and 3C 305), the detection rate of HI outflows is 5% in the total radio AGN sample. Because of the effects of spin temperature and covering factor of the outflowing gas, this fraction could represent a lower limit. However, if the relatively low detection rate is confirmed by more detailed observations, it would suggest that, if outflows are a characteristic phenomenon of all radio AGN, they would have a short depletion timescale compared to the lifetime of the radio source. This would be consistent with results found for some of the outflows traced by molecular gas. Using stacking techniques, in our previous paper we showed that compact radio sources have higher {tau}, FWHM, and column density than extended sources. In addition, here we find that blueshifted and broad/asymmetric lines are more often present among compact sources. In good agreement with the results of stacking, this suggests that unsettled gas is responsible for the larger stacked FWHM detected in compact sources. Therefore in such sources the HI is more likely to be unsettled. This may arise as a result of jet-cloud interactions, as young radio sources clear their way through the rich ambient gaseous medium.
- ID:
- ivo://CDS.VizieR/J/MNRAS/440/696
- Title:
- HI absorption in nearby radio galaxies
- Short Name:
- J/MNRAS/440/696
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using archival data from the Hi Parkes All-Sky Survey (HIPASS), we have searched for 21cm line absorption in 204 nearby radio and star-forming galaxies with continuum flux densities greater than S_1.4_~250mJy within the redshift range 0<cz<12000km/s. By applying a detection method based on Bayesian model comparison, we successfully detect and model absorption against the radio-loud nuclei of four galaxies, of which the Seyfert 2 galaxy 2MASX J130804201-2422581 was previously unknown. All four detections were achieved against compact radio sources, which include three active galactic nuclei (AGNs) and a nuclear starburst, exhibiting high dust and molecular gas content. Our results are consistent with the detection rate achieved by the recent ALFALFA (Arecibo Legacy Fast Arecibo L-band Feed Array) Hi absorption pilot survey by Darling et al. and we predict that the full ALFALFA survey should yield more than three to four times as many detections as we have achieved here. Furthermore, we predict that future all-sky surveys on the Square Kilometre Array precursor telescopes will be able to detect such strong absorption systems associated with type 2 AGNs at much higher redshifts, providing potential targets for detection of H_2_O megamaser emission at cosmological redshifts.
- ID:
- ivo://CDS.VizieR/J/ApJ/871/17
- Title:
- HI and CO observations of M33 interstellar medium
- Short Name:
- J/ApJ/871/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We utilize the multi-wavelength data of M33 to study the origin of turbulence in its interstellar medium. We find that the HI turbulent energy surface density inside 8kpc is ~1-3x10^46^erg/pc^2^, and has no strong dependence on galactocentric radius because of the lack of variation in HI surface density and HI velocity dispersion. Then, we consider the energies injected by supernovae (SNe), the magneto-rotational instability (MRI), and the gravity-driven turbulence from accreted materials as the sources of turbulent energy. For a constant dissipation time of turbulence, the SNe energy can maintain turbulence inside ~4kpc radius (equivalent to ~0.5R_25_), while the MRI energy is always smaller than the turbulent energy within 8kpc radius. However, when we let the dissipation time to be equal to the crossing time of turbulence across the HI scale height, the SNe energy is enough to maintain turbulence out to 7kpc radius, and the sum of SNe and MRI energies is able to maintain turbulence out to 8kpc radius. Due to lack of constraint in the mass accretion rate through the disk of M33, we cannot rule out the accretion driven turbulence as a possible source of energy. Furthermore, by resolving individual giant molecular clouds in M33, we also show that the SNe energy can maintain turbulence within individual molecular clouds with ~1% of coupling efficiency. This result strengthens the proposition that stellar feedback is an important source of energy to maintain turbulence in nearby galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/842/133
- Title:
- HI-bearing ultra-diffuse ALFALFA galaxies
- Short Name:
- J/ApJ/842/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 115 very low optical surface brightness, highly extended, HI-rich galaxies carefully selected from the ALFALFA survey that have similar optical absolute magnitudes, surface brightnesses, and radii to recently discovered "ultra-diffuse" galaxies (UDGs). However, these systems are bluer and have more irregular morphologies than other UDGs, are isolated, and contain significant reservoirs of HI. We find that while these sources have normal star formation rates for HI-selected galaxies of similar stellar mass, they have very low star formation efficiencies. We further present deep optical and HI-synthesis follow-up imaging of three of these HI-bearing ultra-diffuse sources. We measure HI diameters extending to ~40kpc, but note that while all three sources have large HI diameters for their stellar mass, they are consistent with the HI mass-HI radius relation. We further analyze the HI velocity widths and rotation velocities for the unresolved and resolved sources, respectively, and find that the sources appear to inhabit halos of dwarf galaxies. We estimate spin parameters, and suggest that these sources may exist in high spin parameter halos, and as such may be potential HI-rich progenitors to the ultra-diffuse galaxies observed in cluster environments.
- ID:
- ivo://CDS.VizieR/J/ApJ/770/L4
- Title:
- HI clouds around the Galactic Center
- Short Name:
- J/ApJ/770/L4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe a population of small, high-velocity, atomic hydrogen clouds, loops, and filaments found above and below the disk near the Galactic center. The objects have a mean radius of 15pc, velocity widths of ~14km/s, and are observed at |z| heights up to 700pc. The velocity distribution of the clouds shows no signature of Galactic rotation. We propose a scenario where the clouds are associated with an outflow from a central star-forming region at the Galactic center. We discuss the clouds as entrained material traveling at ~200km/s in a Galactic wind.
- ID:
- ivo://CDS.VizieR/J/AJ/157/241
- Title:
- HI clouds in LITTLE THINGS dwarf irregular galaxies
- Short Name:
- J/AJ/157/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify 814 discrete H I clouds in 40 dwarf irregular galaxies from the LITTLE THINGS survey using an automated cloud-finding algorithm. The cloud masses range from ~10^3^ to 10^7^ M_{sun}_, have a surface density averaged over all of the clouds of ~9.65 M_{sun}_/pc^2^, and constitute 2%-53% of the total H I mass of the host galaxy. For individual clouds, the mass including He varies with cloud radius as logM_gas_=(2.11+/-0.04)xlogR_cl_+(0.78+/-0.08) and the internal velocity dispersion varies as logV_disp_=0.5xlogR_cl_-0.57+/-0.21. The H I clouds tend to be in the outer regions of the galaxies, with 72% of the galaxies having more than 70% of their clouds outside one disk scale length and 32% of the galaxies having more than 50% of their clouds outside the radius encircling the H II emission. Thirty-six percent of the clouds are essentially non-self-gravitating from H I alone, with a virial parameter that exceeds {alpha}_vir_~10, and 5% have {alpha}_vir_=<2. We estimate the missing molecular mass, based on the total star formation rate and a typical molecular consumption time of 2 Gyr, as observed in CO-rich galaxies. The resulting molecular fraction has a value averaged over the galaxies of 0.23 and correlates with both the surface density of star formation and the fraction of H I clouds in the outer regions. We conclude that a significant fraction of the inner parts of these dwarf galaxy disks is in the form of dark molecular gas, and that this fraction could be high enough to make the inner disks mildly gravitationally unstable as a precursor to star formation.
