- ID:
- ivo://CDS.VizieR/J/A+AS/126/3
- Title:
- CO and HI in interacting galaxies
- Short Name:
- J/A+AS/126/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using SEST, the Parkes antenna and the Australia Telescope Compact Array, we have made a survey of the ^12^CO(1-0) and HI emission of an optically-selected sample of =~60 southern interacting and merging galaxies. In this paper we present the data and determine global masses of neutral gas (in molecular and atomic form) for the observed galaxies. We have detected HI in 26 systems and found that these galaxies have less than 15% of their gas in molecular form.
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- ID:
- ivo://CDS.VizieR/J/A+A/639/A26
- Title:
- Cold HI, H2 and total H column density FITS maps
- Short Name:
- J/A+A/639/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There are significant amounts of H_2_ in the Milky Way. Due to its symmetry H_2_ does not radiate at radio frequencies. CO is thought to be a tracer for H_2_, however CO is formed at significantly higher opacities than H_2_. Thus, toward high Galactic latitudes significant amounts of H_2_ are hidden and called CO-dark. We demonstrate that the dust-to-gas ratio is a tool to identify locations and column densities of CO-dark H_2_. We adopt the hypothesis of a constant E(B-V)/NH ratio, independent of phase transitions from HI to H_2_. We investigate the Doppler temperatures T_D_, from a Gaussian decomposition of HI4PI data, to study temperature dependencies of E(B-V)/NHI. The E(B-V)/NHI ratio in the cold HI gas phase is high in comparison to the warmer one. We consider this as evidence that cold HI gas toward high Galactic latitudes is associated with H_2_. Beyond CO-bright regions we find for T_D_<1165K a correlation (NHI+2NH_2_)/NHI{prop.to}-log T_D_. In combination with a factor XCO=4.0x10^20^cm^-2^(K.km/s)^-1^ this yields for the full-sky NH/E(B-V)~5.1 to 6.7 10^21^cm^-2^mag^-1^, compatible with X-ray scattering and UV absorption line observations. Cold HI with T_D_<1165K contains on average 46% CO-dark H_2_. Prominent filaments have T_D_<220K and typical excitation temperatures Tex~50K. With a molecular gas fraction of >61% they are dominated dynamically by H_2_.
- ID:
- ivo://CDS.VizieR/J/MNRAS/357/819
- Title:
- Colours and HI line observations in Virgo
- Short Name:
- J/MNRAS/357/819
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to investigate the nature of dwarf low surface brightness (LSB) galaxies we have undertaken a deep B- and I-band CCD survey of a 14-deg^2^ strip in the Virgo Cluster and applied a Fourier convolution technique to explore its dwarf galaxy population down to a central surface brightness of ~26Bmag/arcsec^2^ and a total absolute B magnitude of ~-10. In this paper we carry out an analysis of their morphology, (B-I) colours and atomic hydrogen content.
- ID:
- ivo://CDS.VizieR/J/ApJ/855/33
- Title:
- Compact clouds in a sensitive GBT HI survey
- Short Name:
- J/ApJ/855/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a new sensitive survey of neutral hydrogen above and below the Galactic Center with the Green Bank Telescope. The observations extend up to Galactic latitude |b|<10{deg} with an effective angular resolution of 9.5' and an average rms brightness temperature noise of 40mK in a 1km/s channel. The survey reveals the existence of a population of anomalous high-velocity clouds extending up to heights of about 1.5kpc from the Galactic plane and showing no signature of Galactic rotation. These clouds have local standard of rest velocities |V_LSR_|<~360km/s, and assuming a Galactic Center origin, they have sizes of a few tens of parsec and neutral hydrogen masses spanning 10-10^5^M_{sun}_. Accounting for selection effects, the cloud population is symmetric in longitude, latitude, and VLSR. We model the cloud kinematics in terms of an outflow expanding from the Galactic Center and find the population consistent with being material moving with radial velocity V_w_~330km/s distributed throughout a bicone with opening angle {alpha}>140{deg}. This simple model implies an outflow luminosity L_w_>3x10^40^erg/s over the past 10Myr, consistent with star formation feedback in the inner region of the Milky Way, with a cold gas mass-loss rate <~0.1M_{sun}_/yr. These clouds may represent the cold gas component accelerated in the nuclear wind driven by our Galaxy, although some of the derived properties challenge current theoretical models of the entrainment process.
- ID:
- ivo://CDS.VizieR/J/ApJ/722/395
- Title:
- Compact H I clouds from the GALFA-H I survey
- Short Name:
- J/ApJ/722/395
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galactic Arecibo L-band Feed Array H I (GALFA-H I) survey is mapping the entire Arecibo sky at 21 cm, over a velocity range of -700 to +700 km/s (LSR), at a velocity resolution of 0.18 km/s, and a spatial resolution of 3.5 arcmin. The unprecedented resolution and sensitivity of the GALFA-H I survey have resulted in the detection of numerous isolated, very compact H I clouds at low Galactic velocities, which are distinctly separated from the H I disk emission. In the limited area of ~4600 deg^2^ surveyed so far, we have detected 96 such compact clouds. The detected clouds are cold with a median T_k,max_ (the kinetic temperature in the case in which there is no non-thermal broadening) of 300 K. Moreover, these clouds are quite compact and faint, with median values of 5 arcmin in angular size, 0.75 K in peak brightness temperature, and 5x10^18^/cm2 in H I column density. Most of the clouds deviate from Galactic rotation at the 20-30 km/s level, and a significant fraction show evidence for a multiphase medium and velocity gradients. No counterparts for these clouds were found in other wave bands. From the modeling of spatial and velocity distributions of the whole compact cloud population, we find that the bulk of the compact clouds are related to the Galactic disk, and their distances are likely to be in the range of 0.1 to a few kpc. We discuss various possible scenarios for the formation and maintenance of this cloud population and its significance for Galactic interstellar medium studies.
- ID:
- ivo://CDS.VizieR/J/A+A/411/381
- Title:
- CO observation of isolated galaxies
- Short Name:
- J/A+A/411/381
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ^12^CO(J=1-0) line observations of 99 galaxies obtained with the SEST 15m, the Kitt Peak 12m and the IRAM 30m telescopes. The target galaxies were selected from the catalogue of isolated galaxies of Karachentseva (1973, Cat. <VII/82>). These data are thus representative of the CO properties of isolated late-type galaxies. All objects were observed in their central position, those with large angular sizes were mapped. These new measurements are used to estimate the molecular gas mass of the target galaxies. The molecular gas is on average ~18% of the atomic gas mass.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/5
- Title:
- COS CGM compendium (CCC). III. z<=1 Ly{alpha} syst.
- Short Name:
- J/ApJ/887/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We characterize the metallicities and physical properties of cool, photoionized gas in a sample of 152 z<=1 strong Ly{alpha} forest systems (SLFSs, absorbers with 15<logN_HI_<16.2). The sample is drawn from our Cosmic Origins Spectrograph (COS) circumgalactic medium compendium (CCC), an ultraviolet survey of HI-selected circumgalactic gas around z<=1 galaxies that targets 261 absorbers with 15<logN_HI_<19. We show that the metallicity probability distribution function of the SLFSs at z<=1 is unimodal, skewed to low metallicities with a mean and median of [X/H]=-1.47 and -1.18dex. Very metal-poor gas with [X/H]{<}-1.4 represents about half of the population of absorbers with 15<logN_HI_<=18, while it is rare at higher N_HI_. Thus, there are important reservoirs of primitive (though not pristine) diffuse ionized gas around z<=1 galaxies. The photoionized gas around z<=1 galaxies is highly inhomogeneous based on the wide range of metallicities observed (-3<=[X/H]<=+0.4) and the fact that there are large metallicity variations (factors of 2 to 25) for most of the closely spaced absorbers ({Delta}v<=300km/s) along the same sightlines. These absorbers show a complex evolution with redshift and HI column density, and we identify subtle cosmic evolution effects that affect the interpretation of metallicity distributions and comparison with other absorber samples. We discuss the physical conditions and cosmic baryon and metal budgets of the CCC absorbers. Finally, we compare the CCC results to recent cosmological zoom simulations and explore the origins of the 15<logN_HI_<19 absorbers within the Evolution and Assembly of GaLaxies and their Environments (EAGLE) high-resolution simulations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/414/2005
- Title:
- Cosmic flows observations
- Short Name:
- J/MNRAS/414/2005
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The neutral hydrogen properties of 1822 galaxies are being studied with the Green Bank 100-m and the Parkes 64-m telescopes as part of the 'Cosmic Flows' programme. Observed parameters include systemic velocities, profile linewidths and integrated fluxes. The linewidth information can be combined with the optical and infrared photometry to obtain distances. The 1822 HI observations complement an inventory of archives.
- ID:
- ivo://CDS.VizieR/J/ApJ/896/3
- Title:
- Cosmicflows-4: Tully-Fisher relation calibrations
- Short Name:
- J/ApJ/896/3
- Date:
- 07 Mar 2022 07:21:25
- Publisher:
- CDS
- Description:
- This study is a part of the Cosmicflows-4 project with the aim of measuring the distances of more than ~10000 spiral galaxies in the local universe up to ~15000km/s. New HI line width information has come primarily from the Arecibo Legacy Fast ALFA Survey. Photometry of our sample galaxies has been carried out in optical (SDSS u, g, r, i, and z) and infrared (WISE W1 and W2) bands. Inclinations have been determined using an online graphical interface accessible to a collaboration of citizen scientists. Galaxy distances are measured based on the correlation between the rotation rate of spirals and their absolute luminosity, known as the Tully-Fisher relation (TFR). In this study, we present the calibration of the TFR using a subsample of ~600 spirals located in 20 galaxy clusters. Correlations among such observables as color, surface brightness, and relative HI content are explored in an attempt to reduce the scatter about the TFR with the goal of obtaining more accurate distances. A preliminary determination of the Hubble constant from the distances and velocities of the calibrator clusters is H0=76.0+/-1.1(stat.)+/-2.3(sys.)km/s/Mpc.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A26
- Title:
- Deep HI observations of Leo T with WSRT
- Short Name:
- J/A+A/612/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Leo T is the lowest mass gas-rich galaxy currently known and studies of its gas content help us understand how such marginal galaxies survive and form stars. We present deep neutral hydrogen (HI) observations from the Westerbork Synthesis Radio Telescope in order to understand its HI distribution and potential for star formation. We find a larger HI line flux than the previously accepted value, resulting in a 50% larger HI mass of 4.1x10^5^M_{sun}_. The additional HI flux is from low surface brightness emission that was previously missed; with careful masking this emission can be recovered even in shallower data.We perform a Gaussian spectral decomposition to find a cool neutral medium component (CNM) with a mass of 3.7x10^4^M_{sun}_, or almost 10% of the total HI mass. Leo T has no HI emission extending from the main HI body, but there is evidence of interaction with the Milky Way circumgalactic medium in both a potential truncation of the HI body and the offset of the peak HI distribution from the optical center. The CNM component of Leo T is large when compared to other dwarf galaxies, even though Leo T is not currently forming stars and has a lower star formation efficiency than other gas-rich dwarf galaxies. However, the HI column density associated with the CNM component in Leo T is low. One possible explanation is the large CNM component is not related to star formation potential but rather a recent, transient phenomenon related to the interaction of Leo T with the Milky Way circumgalactic medium.
