- 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_.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/504/543
- Title:
- ^12^C^16^O lines in Arcturus IR spectrum
- Short Name:
- J/A+A/504/543
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the infrared spectrum of Arcturus to clarify the nature of the cool component of its atmosphere, referred to as the CO-mosphere, and its relationship to the warm molecular envelope or the MOLsphere in cooler M (super)giant stars.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A41
- Title:
- CO line survey in 0.2<z<1 of galaxies
- Short Name:
- J/A+A/550/A41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- After new observations of 39 galaxies at z=0.6-1.0 obtained at the IRAM 30m telescope, we present our full CO line survey covering the redshift range 0.2<z<1. Our aim is to determine the driving factors accounting for the steep decline in the star formation rate during this epoch. We study both the gas fraction, defined as Mgas/(Mgas+Mstar), and the star formation efficiency (SFE) defined by the ratio between far-infrared luminosity and molecular gas mass (L_FIR_/M(H_2_), i.e. a measure for the inverse of the gas depletion time. The sources are selected to be ultra-luminous infrared galaxies (ULIRGs), with L_FIR_ greater than 10^12^L_{sun}_, and experiencing starbursts. When we adopt a standard ULIRG CO-to-H_2_ conversion factor, their molecular gas depletion time is less than 100Myr. Our full survey has now filled the gap of CO observations in the 0.2<z<1 range covering almost half of cosmic history. The detection rate in the 0.6<z<1 interval is 38% (15 galaxies out of 39), compared to 60% for the 0.2<z<0.6 interval. The average CO luminosity is L'_CO_=1.8x10^10^K.km/s.pc^2^, corresponding to an average H_2_ mass of 1.45x10^10^M_{sun}_. From observation of 7 galaxies in both CO(2-1) and CO(4-3), a high gas excitation has been derived; together with the dust mass estimation, this supports the choice of our low ULIRG conversion factor between CO luminosity and H_2_ for our sample sources. We find that both the gas fraction and the SFE significantly increase with redshift, by factors of 3+/-1 from z=0 to 1, and therefore both quantities play an important role and complement each other in cosmic star formation evolution.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/369
- Title:
- Colour and spectral index from the SLUGGS survey
- Short Name:
- J/MNRAS/446/369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, we stack 1137 Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) spectra of globular clusters from 10 galaxies to study their stellar populations in detail. The stacked spectra have median signal-to-noise ratios of ~90 {AA}^-1^. Besides the calcium triplet, we study weaker sodium, magnesium, titanium and iron lines as well as the H{alpha} and higher order Paschen hydrogen lines. In general, the stacked spectra are consistent with old ages and a Milky Way-like initial mass function. However, we see different metal line index strengths at fixed colour and magnitude, and differences in the calcium triplet-colour relation from galaxy to galaxy. We interpret this as strong evidence for variations in the globular cluster colour-metallicity relation between galaxies. Two possible explanations for the colour-metallicity relation variations are that the average ages of globular clusters vary from galaxy to galaxy or that the average abundances of light elements (i.e. He, C, N and O) differ between galaxies. Stacking spectra by magnitude, we see that the colours become redder and metal line indices stronger with brighter magnitudes. These trends are consistent with the previously reported `blue tilts' being mass-metallicity relations.
- ID:
- ivo://CDS.VizieR/J/ApJ/894/142
- Title:
- Column densities from HST/COS SiIV AGN sight lines
- Short Name:
- J/ApJ/894/142
- Date:
- 19 Jan 2022 13:10:08
- Publisher:
- CDS
- Description:
- We develop a kinematical model for the Milky Way SiIV-bearing gas to determine its density distribution and kinematics. This model is constrained by a column density line-shape sample extracted from the Hubble Space Telescope/Cosmic Origins Spectrograph archival data, which contains 186 active galactic nucleus sight lines. We find that the SiIV ion density distribution is dominated by an extended disk along the z-direction (above or below the midplane), i.e., n(z)=n_0_exp(-(z/z_0_)^0.82^), where z_0_ is the scale height of 6.3_-1.5_^+1.6^kpc (northern hemisphere) and 3.6_-0.9_^+1.0^kpc (southern hemisphere). The density distribution of the disk in the radial direction shows a sharp edge at 15-20kpc given by, n(r_XY_)=n_0_exp(-(r_XY_/r_0_)^3.36^), where r_0_~12.5+/-0.6kpc. The difference of density distributions over r_XY_ and z directions indicates that the warm gas traced by SiIV is mainly associated with disk processes (e.g., feedback or cycling gas) rather than accretion. We estimate the mass of the warm gas (within 50kpc) is log(M(50kpc)/M_{sun}_)~8.1 (assuming Z~0.5Z_{sun}_), and a 3{sigma} upper limit of log(M(250kpc)/M_{sun}_)~9.1 (excluding the Magellanic system). Kinematically, the warm gas disk is nearly co-rotating with the stellar disk at v_rot_=215+/-3km/s, which lags the midplane rotation by about 8km/s/kpc (within 5kpc). Meanwhile, we note that the warm gas in the northern hemisphere has significant accretion with vacc of 69+/-7km/s at 10kpc (an accretion rate of -0.60_-0.13_^+0.11^M_{sun}_/yr), while in the southern hemisphere, there is no measurable accretion, with an upper limit of 0.4M_{sun}_/yr.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/78
- Title:
- Column densities of CGM absorption lines
- Short Name:
- J/ApJ/883/78
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the geometric distribution of gas metallicities in the circumgalactic medium (CGM) around 47, z<0.7 galaxies from the "Multiphase Galaxy Halos" Survey. Using a combination of quasar spectra from Hubble Space Telescope (HST)/COS and from Keck/HIRES or Very Large Telescope/UVES, we measure column densities of, or determine limits on, CGM absorption lines. We then use a Markov Chain Monte Carlo approach with Cloudy to estimate the metallicity of cool (T~10^4^K) CGM gas. We also use HST images to determine host-galaxy inclination and quasar-galaxy azimuthal angles. Our sample spans a HI column density range of 13.8cm^-2^<logN_HI_<19.9cm^-2^. We find (1) while the metallicity distribution appears bimodal, a Hartigan dip test cannot rule out a unimodal distribution (0.4{sigma}). (2) CGM metallicities are independent of halo mass, spanning three orders of magnitude at a fixed halo mass. (3) The CGM metallicity does not depend on the galaxy azimuthal and inclination angles regardless of HI column density, impact parameter, and galaxy color. (4) The ionization parameter does not depend on azimuthal angle. We suggest that the partial Lyman limit metallicity bimodality is not driven by a spatial azimuthal bimodality. Our results are consistent with simulations where the CGM is complex and outflowing, accreting, and recycled gas are well-homogenized at z<0.7. The presence of low-metallicity gas at all orientations suggests that cold streams of accreting filaments are not necessarily aligned with the galaxy plane at low redshifts or intergalactic transfer may dominate. Finally, our results support simulations showing that strong metal absorption can mask the presence of low-metallicity gas in integrated line-of-sight CGM metallicities.
- ID:
- ivo://CDS.VizieR/J/A+AS/141/449
- Title:
- Coma cluster early-type galaxies
- Short Name:
- J/A+AS/141/449
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 1 describes the photometric properties (R-band magnitude, effective radius, surface brightness, a_4_, ellipticity) of all 35 Coma cluster galaxies, which are investigated spectroscopically in this work. Besides the galaxy numbers given by Godwin et al. (1983, Cat. <VII/42>, GMP83), we also list the NGC/IC numbers as well as Dressler's numbers given in Dressler et al. (1987ApJ...313...42D, D87). Additionally the galaxy type as well as there distance to the clusters center are given. Table 5 to Table 12 (photom.dat) give the results from surface brightness and isophotal shape analysis (local surface brightness, ellipticity, position angle and Fourier coefficients along the major axis) for 8 galaxies of the sample derived from Kron Cousins R band photometry. Table 13 to Table 47 (kinema.dat) give spatially resolved kinematic parameter (v, sigma, H_3_, H_4_) for all 35 galaxies while in Table 48 to Table 82 (indice1.dat and indice2.dat) we list the radial profiles of the measured line indices (H_beta_, Mg, Fe, NaD) of these galaxies. Table 4 contains the results from the comparison of our mean data within the circular standard aperture (see paper) with the mean values given by Joergensen (1999MNRAS.306..607J, J99).
- ID:
- ivo://CDS.VizieR/J/A+A/407/423
- Title:
- Coma cluster early-type galaxies. III.
- Short Name:
- J/A+A/407/423
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on Paper I of this series (Mehlert et al., 2000, Cat. <J/A+AS/141/449>), we derive central values and logarithmic gradients for the Hbeta, Mg and Fe indices of 35 early-type galaxies in the Coma cluster. We find that pure elliptical galaxies have on average slightly higher velocity dispersions, lower Hbeta, and higher metallic line-strengths than galaxies with disks (S0).
- ID:
- ivo://CDS.VizieR/J/MNRAS/411/2558
- Title:
- Coma cluster galaxies absorption-line indices
- Short Name:
- J/MNRAS/411/2558
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we study the stellar populations of 356 bright, Mr<=-19, Coma cluster members located in a 2{deg} field centred on the cluster core using Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) spectroscopy. We find ~31 per cent of the sample have significant emission in H{beta}, [OIII]5007, H{alpha} or [NII]6585, due to star formation or active galactic nuclei (AGN)/LINER activity. The remaining portion of the sample we describe as passive or quiescent.
- ID:
- ivo://CDS.VizieR/J/AJ/156/68
- Title:
- Comet C/2017 E4 composition with iSHELL at NASA/IRTF
- Short Name:
- J/AJ/156/68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In 2017 April, we acquired comprehensive high-resolution spectra of newly discovered comet C/2017 E4 (Lovejoy) as it approached perihelion, and before its disintegration. We detected many cometary emission lines in the range (2.8-5.3) {mu}m, in four customized instrument settings (L1-c, L3, Lp1-c, and M1) of iSHELL - the new near-IR high-resolution immersion echelle spectrograph at NASA/IRTF (Maunakea, Hawaii). We identified 12 molecular species: nine primary volatiles (H_2_O, HCN, NH_3_, CO, C_2_H_2_, C_2_H_6_, CH_4_, CH_3_OH, H_2_CO) and three product species (CN, NH_2_, OH). We detected 85 H_2_O emission lines from 12 water vibrational bands across L1-c and M1 settings. The many detected water emission lines enabled retrieval of accurate measures for ortho- and para-H_2_O independently, thereby reducing systematic uncertainty in the derived ortho-para ratio and nuclear spin temperature. Excitation analyses and emission profile analyses were performed for all species, and molecular abundance ratios relative to water are compared with values found for other Oort Cloud comets in our infrared database. Abundance ratios are consistent for most species, with the exception of underabundant methanol and overabundant ammonia in E4.
