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331. CO in HCG galaxies with enhanced warm H_2_
ID:
ivo://CDS.VizieR/J/A+A/570/A24
Title:
CO in HCG galaxies with enhanced warm H_2_
Short Name:
J/A+A/570/A24
Date:
21 Oct 2021
Publisher:
CDS
Description:
Galaxies in Hickson Compact Groups (HCGs) are believed to experience morphological transformations from blue, star-forming galaxies to red, early-type galaxies. Galaxies with a high ratio between the luminosities of the warm H_2_ to the 7.7micron PAH emission (so-called Molecular Hydrogen Emission Galaxies, MOHEGs) are predominantly in an intermediate phase, the green valley. Their enhanced H_2_ emission suggests that the molecular gas is affected in the transition. We study the properties of the molecular gas traced by CO in galaxies in HCGs with measured warm H_2_ emission in order to look for evidence of the perturbations affecting the warm H_2_ in the kinematics, morphology and mass of the molecular gas. We observed the CO(1-0) emission of 20 galaxies in HCGs and complemented our sample with 11 CO(1-0) spectra from the literature. Most of the galaxies have measured} warm H_2_ emission, and 14 of them are classified as MOHEGs. We mapped some of these galaxies in order to search for extra-galactic CO emission. We analyzed the molecular gas mass derived from CO(1-0), MH_2_, and its kinematics, and then compared it to the mass of the warm molecular gas, the stellar mass and star formation rate (SFR). Our results are the following. (i) The mass ratio between the CO-derived and the warm H_2_ molecular gas is in the same range as found for field galaxies. (ii) Some of the galaxies, mostly MOHEGs, have very broad CO linewidths of up to 1000km/s in the central pointing. The line shapes are irregular and show various components. (iii) In the mapped objects we found asymmetric distributions of the cold molecular gas. (iv) The star formation efficiency (=SFR/MH_2_) of galaxies in HCGs is very similar to isolated galaxies. No significant difference between MOHEGs and non-MOHEGs or between early-type and spiral galaxies has been found. In a few objects the SFE is significantly lower, indicating the presence of molecular gas that is not actively forming stars. (v) The molecular gas masses, MH_2_, and ratios MH_2_/Lk are lower in MOHEGs (predominantly early-types) than in non-MOHEGs (predominantly spirals). This trend remains when comparing MOHEGs and non-MOHEGs of the same morphological type. We found differences in the molecular gas properties of MOHEGs that support the view that they have suffered (or are presently suffering) perturbations of the molecular gas, as well as a decrease in the molecular gas content and associated SFR. Higher resolution observations of the molecular gas are needed to shed light on the nature of these perturbations and their cause.
332. 6 cold-gas-bearing debris-disc stars spectra
ID:
ivo://CDS.VizieR/J/A+A/614/A3
Title:
6 cold-gas-bearing debris-disc stars spectra
Short Name:
J/A+A/614/A3
Date:
21 Oct 2021
Publisher:
CDS
Description:
Debris discs have often been described as gas-poor discs as the gas-to-dust ratio is expected to be considerably lower than in primordial, protoplanetary discs. However, recent observations have confirmed the presence of a non-negligible amount of cold gas in the circumstellar (CS) debris discs around young main-sequence stars. This cold gas has been suggested to be related to the outgassing of planetesimals and cometary-like objects. The goal of this paper is to investigate the presence of hot gas in the immediate surroundings of the cold-gas-bearing debris-disc central stars. High-resolution optical spectra of all currently known cold-gas-bearing debris-disc systems, with the exception of beta Pic and Fomalhaut, have been obtained from La Palma (Spain), La Silla (Chile), and La Luz (Mexico) observatories. To verify the presence of hot gas around the sample of stars, we have analysed the CaII H&K and the NaI D lines searching for non-photospheric absorptions of CS origin, usually attributed to cometary-like activity.
333. CO line survey in 0.2<z<1 of galaxies
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.
334. Colour and spectral index from the SLUGGS survey
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.
335. Column densities from HST/COS SiIV AGN sight lines
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.
336. Column densities of CGM absorption lines
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.
337. Coma cluster early-type galaxies
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).
338. Coma cluster early-type galaxies. III.
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).
339. Coma cluster galaxies absorption-line indices
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.
340. Comet C/2016 R2 (PanSTARRS) IRAM spectra
ID:
ivo://CDS.VizieR/J/A+A/619/A127
Title:
Comet C/2016 R2 (PanSTARRS) IRAM spectra
Short Name:
J/A+A/619/A127
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a multi-wavelength study of comet C/2016 R2 (PanSTARRS). This comet was observed on 23-24 January 2018 with the IRAM 30m telescope, and in January to March 2018 with the Nancay radio telescope. Visible spectroscopy was performed in December 2017 and February 2018 with small amateur telescopes. We report on measurements of CO, CH_3_OH, H_2_CO and HCN production rates, and on the determination of the N2/CO abundance ratio. Several other species, especially OH, were searched for but not detected. The inferred relative abundances, including upper limits for sulfur species, are compared to those measured in other comets at about the same heliocentric distance of ~2.8AU. The coma composition of comet C/2016 R2 is very different from all other comets observed so far, being rich in N2 and CO and dust poor. This suggests that this comet might belong to a very rare group of comets formed beyond the N_2_ ice line. Alternatively, comet C/2016 R2 (PanSTARRS) could be the fragment of a large and differentiated transneptunian object, with properties characteristic of volatile-enriched layers.