- ID:
- ivo://CDS.VizieR/J/ApJS/237/36
- Title:
- Merging dwarf galaxies in the local universe
- Short Name:
- J/ApJS/237/36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the largest publicly available catalog of interacting dwarf galaxies. It includes 177 nearby merging dwarf galaxies of stellar mass M*<10^10^M_{sun}_ and redshifts z<0.02. These galaxies are selected by visual inspection of publicly available archival imaging from two wide-field optical surveys (SDSS-III and the Legacy Survey), and they possess low-surface-brightness features that are likely the result of an interaction between dwarf galaxies. We list UV and optical photometric data that we use to estimate stellar masses and star formation rates. So far, the study of interacting dwarf galaxies has largely been done on an individual basis, and lacks a sufficiently large catalog to give statistics on the properties of interacting dwarf galaxies, and their role in the evolution of low-mass galaxies. We expect that this public catalog can be used as a reference sample to investigate the effects of the tidal interaction on the evolution of star formation, and the morphology/structure of dwarf galaxies. Our sample is overwhelmingly dominated by star-forming galaxies, and they are generally found significantly below the red sequence in the color-magnitude relation. The number of early-type galaxies is only 3 out of 177. We classify them, according to observed low-surface-brightness features, into various categories including shells, stellar streams, loops, antennae, or simply interacting. We find that dwarf-dwarf interactions tend to prefer the low-density environment. Only 41 out of the 177 candidate dwarf-dwarf interaction systems have giant neighbors within a sky-projected distance of 700kpc and a line-of-sight radial velocity range +/-700km/s, and compared to the LMC-SMC, they are generally located at much larger sky-projected distances from their nearest giant neighbors.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/148/137
- Title:
- Merging galaxies in COSMOS to z~1
- Short Name:
- J/AJ/148/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The role of major mergers in galaxy and black hole formation is not well-constrained. To help address this, we develop an automated method to identify late-stage galaxy mergers before coalescence of the galactic cores. The resulting sample of mergers is distinct from those obtained using pair-finding and morphological indicators. Our method relies on median-filtering of high-resolution images to distinguish two concentrated galaxy nuclei at small separations. This method does not rely on low surface brightness features to identify mergers, and is therefore reliable to high redshift. Using mock images, we derive statistical contamination and incompleteness corrections for the fraction of late-stage mergers. The mock images show that our method returns an uncontaminated (<10%) sample of mergers with projected separations between 2.2 and 8kpc out to z~1. We apply our new method to a magnitude-limited (m_FW814_<23) sample of 44164 galaxies from the COSMOS HST/ACS catalog. Using a mass-complete sample with log M_{star}_/M_{sun}_>10.6 and 0.25<z<=1.00, we find ~5% of systems are late-stage mergers. Correcting for incompleteness and contamination, the fractional merger rate increases strongly with redshift as {\bf R}_merge_\propto(1+z)^3.8+/-0.9^, in agreement both with earlier studies and with dark matter halo merger rates. Separating the sample into star-forming and quiescent galaxies shows that the merger rate for star-forming galaxies increases strongly with redshift, (1+z)^4.5+/-1.3^, while the merger rate for quiescent galaxies is consistent with no evolution, (1+z)^1.1+/-1.2^. The merger rate also becomes steeper with decreasing stellar mass. Limiting our sample to galaxies with spectroscopic redshifts from zCOSMOS, we find that the star formation rates and X-ray selected active galactic nucleus (AGN) activity in likely late-stage mergers are higher by factors of ~2 relative to those of a control sample. Combining our sample with more widely separated pairs, we find that 8+/-5% of star formation and 20+/-8% of AGN activity are triggered by close encounters (<143kpc) or mergers, providing additional evidence that major mergers are not the only channels for star formation and black hole growth.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/90
- Title:
- Merging galaxies with tidal tails in COSMOS to z=1
- Short Name:
- J/ApJ/832/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Tidal tails are created in major mergers involving disk galaxies. It remains to be explored how the tidal tails trace the assembly history of massive galaxies. We identify a sample of 461 merging galaxies with long tidal tails, from 35076 galaxies mass-complete at M*>=10^9.5^M_{sun}_ and 0.2<=z<=1, based on Hubble Space Telescope/ACS F814W imaging data and public catalogs of the COSMOS field. The long tails refer to those with length equal to or greater than the diameter of their host galaxies. The mergers with tidal tails are selected using our novel A_O_-D_O_ technique for strong asymmetric features, along with visual examination. Our results show that the fraction of tidal-tailed mergers evolves mildly with redshift, as ~(1+z)^2.0+/-0.4^, and becomes relatively higher in less-massive galaxies, out to z=1. With a timescale of 0.5Gyr for the tidal-tailed mergers, we obtain that the occurrence rate of such mergers follows 0.01+/-0.007(1+z)^2.3+/-1.4^Gyr^-1^, and corresponds to ~0.3 events since z=1, as well as roughly one-third of the total budget of major mergers from the literature. For disk-involved major mergers, nearly half of them have undergone a phase with long tidal tails.
- ID:
- ivo://CDS.VizieR/J/ApJ/727/14
- Title:
- Merging galaxy cluster A2255 in mid-IR
- Short Name:
- J/ApJ/727/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the mid-infrared (MIR) observation of a nearby galaxy cluster, A2255, by the AKARI space telescope. Using AKARI's continuous wavelength coverage between 3 and 24um and the wide field of view, we investigate the properties of cluster member galaxies to see how the infall of the galaxies, the cluster substructures, and the cluster-cluster merger influence their evolution. We show that the excess of MIR (~11um) flux is a good indicator for discriminating galaxies at different evolutionary stages and for dividing galaxies into three classes accordingly: strong MIR-excess (N3-S11>0.2) galaxies that include both unobscured and obscured star-forming galaxies; weak MIR-excess (-2.0<N3-S11<-1.2) galaxies that are quiescent, old (>5Gyr) galaxies where the MIR emission arises mainly from the circumstellar dust around AGB stars; and intermediate MIR-excess (-1.2<N3-S11<0.2) galaxies in between the two classes that are less than a few Gyr old past the prime star formation activity. With the MIR-excess diagnostics, we investigate how local and cluster-scale environments affect the individual galaxies. We derive the total star formation rate (SFR) and the specific SFR of A2255 using the strong MIR-excess galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/240/39
- Title:
- Merging galaxy cluster deep observations
- Short Name:
- J/ApJS/240/39
- Date:
- 18 Jan 2022 14:59:05
- Publisher:
- CDS
- Description:
- Multi-band photometric and multi-object spectroscopic surveys of merging galaxy clusters allow for the characterization of the distributions of constituent DM and galaxy populations, constraints on the dynamics of the merging subclusters, and an understanding of galaxy evolution of member galaxies. We present deep photometric observations from Subaru/SuprimeCam and a catalog of 4431 spectroscopic galaxies from Keck/DEIMOS observations of 29 merging galaxy clusters ranging in redshift from z=0.07 to 0.55. The ensemble is compiled based on the presence of radio relics, which highlight cluster-scale collisionless shocks in the intracluster medium. Together with the spectroscopic and photometric information, the velocities, timescales, and geometries of the respective merging events may be tightly constrained. In this preliminary analysis, the velocity distributions of 28 of the 29 clusters are shown to be well fit by single Gaussians. This indicates that radio-relic mergers largely occur transverse to the line of sight and/or near-apocenter. In this paper, we present our optical and spectroscopic surveys, preliminary results, and a discussion of the value of radio-relic mergers for developing accurate dynamical models of each system.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A6
- Title:
- Metal abundances of galaxy clusters
- Short Name:
- J/A+A/546/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work measures the evolution of the iron content in galaxy clusters by a rigorous analysis of the data of 130 clusters at 0.1<z<1.3. This task is made difficult by a) the low signal-to-noise ratio of abundance measurements and the upper limits, b) possible selection effects, c) boundaries in the parameter space, d) non-Gaussian errors, e) the intrinsic variety of the objects studied, and f) abundance systematics. We introduce a Bayesian model to address all these issues at the same time, thus allowing cross-talk (covariance).
- ID:
- ivo://CDS.VizieR/J/AJ/150/71
- Title:
- Metal abundances of KISS galaxies. V.
- Short Name:
- J/AJ/150/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high signal-to-noise ratio spectroscopy of 15 emission-line galaxies cataloged in the KPNO International Spectroscopic Survey, selected for their possession of high equivalent width [OIII] lines. The primary goal of this study was to attempt to derive direct-method (T_e_) abundances for use in constraining the upper-metallicity branch of the R_23_ relation. The spectra cover the full optical region from [OII]{lambda}{lambda}3726,3729 to [SIII]{lambda}{lambda}9069,9531 and include the measurement of [OIII]{lambda}4363 in 13 objects. From these spectra, we determine abundance ratios of helium, nitrogen, oxygen, neon, sulfur, and argon. We find these galaxies to predominantly possess oxygen abundances in the range of 8.0<~12+log(O/H)<~8.3. We present a comparison of direct-method abundances with empirical strong-emission-line techniques, revealing several discrepancies. We also present a comparison of direct-method oxygen abundance calculations using electron temperatures determined from emission lines of O^++^ and S^++^, finding a small systematic shift to lower T_e_(~1184K) and higher metallicity (~0.14dex) for sulfur-derived T_e_ compared to oxygen-derived T_e_. Finally, we explore in some detail the different spectral activity types of targets in our sample, including regular star-forming galaxies, those with suspected AGN contamination, and a local pair of low-metallicity, high-luminosity compact objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/755/89
- Title:
- Metallicities of damped Ly{alpha} systems
- Short Name:
- J/ApJ/755/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present chemical abundance measurements for 47 damped Ly{alpha} (DLA) systems, 30 at z>4, observed with the Echellette Spectrograph and Imager and the High Resolution Echelle Spectrometer on the Keck telescopes. H I column densities of the DLAs are measured with Voigt profile fits to the Ly{alpha} profiles, and we find an increased number of false DLA identifications with Sloan Digital Sky Survey at z>4 due to the increased density of the Ly{alpha} forest. Ionic column densities are determined using the apparent optical depth method, and we combine our new metallicity measurements with 195 from previous surveys to determine the evolution of the cosmic metallicity of neutral gas. We find the metallicity of DLAs decreases with increasing redshift, improving the significance of the trend and extending it to higher redshifts, with a linear fit of -0.22+/-0.03 dex per unit redshift from z=0.09-5.06. The metallicity "floor" of {approx}1/600 solar continues out to z~5, despite our sensitivity for finding DLAs with much lower metallicities. However, this floor is not statistically different from a steep tail to the distribution. We also find that the intrinsic scatter of metallicity among DLAs of ~0.5dex continues out to z~5. In addition, the metallicity distribution and the {alpha}/Fe ratios of z>2 DLAs are consistent with being drawn from the same parent population with those of halo stars. It is therefore possible that the halo stars in the Milky Way formed out of gas that commonly exhibits DLA absorption at z>2.
- ID:
- ivo://CDS.VizieR/J/ApJ/770/138
- Title:
- Metallicities of Lyman limit systems and DLA
- Short Name:
- J/ApJ/770/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We assess the metal content of the cool (~10^4^K) circumgalactic medium (CGM) about galaxies at z<~1 using an H I-selected sample of 28 Lyman limit systems (LLS; defined here as absorbers with 16.2<~logN_HI_<~18.5) observed in absorption against background QSOs by the Cosmic Origins Spectrograph on board the Hubble Space Telescope. The N_HI_ selection avoids metallicity biases inherent in many previous studies of the low-redshift CGM. We compare the column densities of weakly ionized metal species (e.g., O II, Si II, Mg II) to N_HI_ in the strongest H I component of each absorber. We find that the metallicity distribution of the LLS (and hence the cool CGM) is bimodal with metal-poor and metal-rich branches peaking at [X/H]=~-1.6 and -0.3 (or about 2.5% and 50% solar metallicities). The cool CGM probed by these LLS is predominantly ionized. The metal-rich branch of the population likely traces winds, recycled outflows, and tidally stripped gas; the metal-poor branch has properties consistent with cold accretion streams thought to be a major source of fresh gas for star forming galaxies. Both branches have a nearly equal number of absorbers. Our results thus demonstrate there is a significant mass of previously undiscovered cold metal-poor gas and confirm the presence of metal enriched gas in the CGM of z<~1 galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/819/73
- Title:
- Metallicity evolution of COSMOS BCD sample
- Short Name:
- J/ApJ/819/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present oxygen abundance measurements for 74 blue compact dwarf (BCD) galaxies in the redshift range of [0.2, 0.5] using the strong-line method. The spectra of these objects are taken using Hectospec on the Multiple Mirror Telescope. More than half of these BCDs had dust attenuation corrected using the Balmer decrement method. For comparison, we also selected a sample of 2023 local BCDs from the Sloan Digital Sky Survey (SDSS) database. Based on the local and intermediate-z BCD samples, we investigated the cosmic evolution of the metallicity, star formation rate (SFR), and D_n_(4000) index. Compared with local BCDs, the intermediate-z BCDs had a systematically higher R23 ratio but a similar O32 ratio. Interestingly, no significant deviation in the mass-metallicity (MZ) relation was found between the intermediate-z and local BCDs. Besides the metallicity, the intermediate-z BCDs also exhibited an SFR distribution that was consistent with local BCDs, suggesting a weak dependence on redshift. The intermediate-z BCDs seemed to be younger than the local BCDs with lower D_n_(4000) index values. The insignificant deviation in the mass-metallicity and mass-SFR relations between intermediate-z and local BCDs indicates that the relations between the global parameters of low-mass compact galaxies may be universal. These results from low-mass compact galaxies could be used to place important observational constraints on galaxy formation and evolution models.