- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/181/572
- Title:
- Collisional ring galaxies atlas
- Short Name:
- J/ApJS/181/572
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog and imaging atlas of classical (collisional) RING galaxies distilled from the Arp-Madore Atlas of Southern Peculiar Galaxies and Associations and supplemented with other known RING galaxies from the published literature. The catalog lists the original host object, compiles available redshifts, and presents newly determined positions for the central (target) galaxy and its nearest companion(s). 127 collisional RING systems are illustrated and their components identified. All of the RINGS have plausible colliders identified; many are radial-velocity confirmed companions. Finally, we make note of the existence of a rare subclass of RING galaxies exemplified by AM 2136-492, double/concentric RING galaxies. These objects are predicted by numerical simulations, but they appear to be quite rare and/or short lived in nature.
- ID:
- ivo://CDS.VizieR/J/ApJ/766/109
- Title:
- Color/age/metallicity gradients of E galaxies
- Short Name:
- J/ApJ/766/109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to understand the past merging history of elliptical galaxies, we studied the optical-near-infrared (NIR) color gradients of 204 elliptical galaxies. These galaxies are selected from the overlap region of the Sloan Digital Sky Survey (SDSS) Stripe 82 and the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). The use of optical and NIR data (g, r, and K) provides large wavelength baselines, and breaks the age-metallicity degeneracy, allowing us to derive age and metallicity gradients. The use of the deep SDSS Stripe 82 images makes it possible for us to examine how the color/age/metallicity gradients are related to merging features. We find that the optical-NIR color and the age/metallicity gradients of elliptical galaxies with tidal features are consistent with those of relaxed ellipticals, suggesting that the two populations underwent a similar merging history on average and that mixing of stars was more or less completed before the tidal features disappeared. Elliptical galaxies with dust features have steeper color gradients than the other two types, even after masking out dust features during the analysis, which can be due to a process involving wet merging. More importantly, we find that the scatter in the color/age/metallicity gradients of the relaxed and merging feature types decreases as their luminosities (or masses) increase at M>10^11.4^M_{sun}_ but stays large at lower luminosities. Mean metallicity gradients appear nearly constant over the explored mass range, but a possible flattening is observed at the massive end.
- ID:
- ivo://CDS.VizieR/J/A+A/397/361
- Title:
- 15-color BATC photometry of Landolt SA95 field
- Short Name:
- J/A+A/397/361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present a set of photometric observations in 15 colors of stars in the Landolt SA95 field with the BATC (Beijing-Arizona-Taipei-Connecticut) system. The wavelengths covered by the system range from 300nm to 1000nm. Visual magnitudes of the stars studied in the field are from the 10th to 20th mag. The observational methodology and the data reduction procedures are described. The relationships between the BATC intermediate-band system and the Landolt UBVRI broad band system are obtained. A catalogue of the photometry has been produced which contains the spectral energy distributions (SEDs) of 3613 stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/368
- Title:
- Color-magnitude relations of galaxies in CDFs
- Short Name:
- J/ApJ/720/368
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extend color-magnitude relations for moderate-luminosity X-ray active galactic nucleus (AGN) hosts and non-AGN galaxies through the galaxy formation epoch (z~1-4) in the Chandra Deep Field-North and Chandra Deep Field-South (CDF-N and CDF-S, respectively; jointly CDFs) surveys. This study was enabled by the deepest available X-ray data from the 2Ms CDF surveys as well as complementary ultradeep multiwavelength data in these regions. We utilized analyses of color-magnitude diagrams (CMDs) to assess the role of moderate-luminosity AGNs in galaxy evolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/149
- Title:
- Color-metallicity relations. II. M87 GCs
- Short Name:
- J/ApJ/743/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We here propose a new photometric technique to probe the possible nonlinear nature of globular clusters (GCs) color-metallicity relations (CMRs). In essence, a color distribution of GCs is a "projected" distribution of their metallicities. Since the form of CMRs hinges on which color is used, the shape of color distributions varies depending significantly on the colors. Among other optical colors, the u-band related colors (e.g., u-g and u-z) are theoretically predicted to exhibit significantly less inflected CMRs than other preferred CMRs (e.g., for g-z). As a case study, we performed the Hubble Space Telescope (HST)/WFPC2 archival u-band photometry for the M87 (NGC 4486) GC system with confirmed color bimodality. We show that the u-band color distributions are significantly different from that of g-z and consistent with our model predictions. With more u-band measurements, this method will support or rule out the nonlinear CMR scenario for the origin of GC color bimodality with high confidence.
- ID:
- ivo://CDS.VizieR/J/AJ/109/543
- Title:
- Color of Bright Galaxies
- Short Name:
- J/AJ/109/543
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Total color indices (V-R)tot, (V-I)tot and effective color indices (V-R)eff, (V-I)eff in the Cousins VRI photometric system are presented for 501 mostly normal galaxies. The colors are computed using a procedure outlined in the Third Reference Catalogue of Bright Galaxies (RC3) whereby standard color curves approximated by Laplace-Gauss integrals are fitted to observed photoelectric multiaperture photometry. 11 sources of such photometry were used for our analysis, each source being assigned an appropriate weight according to a rigorous analysis of residuals of the data from the best-fitting standard color curves. Together with the integrated B-V and U-B colors provided in RC3, our analysis widens the range of wavelength of homogeneously defined colors of normal galaxies of all Hubble types. We present color-color and color-type relations that can be modeled to understand the star formation history of galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/507/283
- Title:
- Colors and extinction across the disk of M31
- Short Name:
- J/A+A/507/283
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a study of the dust properties in M31. We analyzed Spitzer Space Telescope, GALEX, and SDSS images constraining some basic properties of the dust in M31: (i) the mass of the dust; (ii) the mean intensity of the radiation field heating the dust; (iii) the abundance of Polycyclic Aromatic Hydrocarbon (PAH) particles. We also studied which stellar populations are most likely responsible for the dust heating in M31 analyzing optical and infrared colors and comparing our observations with models which account for the age-dependent dust heating. We found that in most of the regions analyzed stars at least a few Gyr old are the major dust heaters. We then derived the extinction map across the disk of M31.
- 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/582/668
- Title:
- Colours and H{alpha} in galaxy pairs
- Short Name:
- J/ApJ/582/668
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxy-galaxy interactions rearrange the baryons in galaxies and trigger substantial star formation; the aggregate effects of these interactions on the evolutionary histories of galaxies in the universe are poorly understood. We combine B- and R-band photometry and optical spectroscopy to estimate the strengths and timescales of bursts of triggered star formation in the centers of 190 galaxies in pairs and compact groups. Based on an analysis of the measured colors and EW(H{alpha}), we characterize the preexisting and triggered populations separately. The best-fitting burst scenarios assume stronger reddening corrections for line emission than for the continuum and continuous star formation lasting for >~100Myr. The most realistic scenarios require an initial mass function that is deficient in the highest mass stars. The color of the preexisting stellar population is the most significant source of uncertainty. Triggered star formation contributes substantially (probably >~50%) to the R-band flux in the central regions of several galaxies; tidal tails do not necessarily accompany this star formation. Many of the galaxies in our sample have bluer centers than outskirts, suggesting that pre- or nonmerger interactions may lead to evolution along the Hubble sequence. These objects would appear blue and compact at higher redshifts; the older, redder outskirts of the disks would be difficult to detect. Our data indicate that galaxies with larger separations on the sky contain weaker, and probably older, bursts of star formation on average. However, confirmation of these trends requires further constraints on the colors of the older stellar populations and on the reddening for individual galaxies.
