- ID:
- ivo://CDS.VizieR/J/AJ/132/197
- Title:
- Close pairs of galaxies
- Short Name:
- J/AJ/132/197
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study star formation in a sample of 345 galaxies in 167 pairs and compact groups drawn from the original CfA2 Redshift Survey and from a follow-up search for companions. We construct our sample with attention to including pairs with luminosity contrast |{Delta}m_R_|>=2. These 57 galaxies with |{Delta}m_R_|>=2 provide a set of nearby representative cases of minor interactions, a central feature of the hierarchical galaxy formation model. Here we report the redshifts and positions of the 345 galaxies in our sample and of 136 galaxies in apparent pairs that are superpositions.
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- ID:
- ivo://CDS.VizieR/J/A+A/631/A87
- Title:
- Close pairs of galaxies in MUSE Deep Fields
- Short Name:
- J/A+A/631/A87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the ILLUSTRIS cosmological simulation project, we investigate the relation between the separation of galaxies in a pair, both in velocity and projected spatial separation space, and the probability that these interacting galaxies will merge in the future. From this analysis, we propose a new set of criteria to select close pairs of galaxies along with a new corrective term to be applied to the computation of the galaxy merger fraction. We then probe the evolution of the major and minor merger fraction using the latest MUSE deep observations over the Hubble Ultra Deep Field, Hubble Deep Field South, COSMOS-Gr30 and Abell 2744 regions. From a parent sample of 2483 galaxies with spectroscopic redshifts, we identify 366 close pairs spread over a large range of redshifts (0.2<z<6) and stellar masses (10^7^-10^11^M_{sun}_). Using the stellar mass ratio between the secondary and primary galaxy as a proxy to split the sample into major, minor and very minor mergers, we found a total of 183 major, 142 minor and 47 very minor close pairs corresponding to a mass ratio range of 1:1-1:6, 1:6-1:100 and lower than 1:100, respectively. Due to completeness issues, we do not consider the very minor pairs in the analysis. Overall, the major merger fraction increases up to z~2-3 reaching 25% for pairs with the most massive galaxy with a stellar mass M*>10^9.5^M_{sun}_. Beyond this redshift, the fraction decreases down to ~5% at z~6. The major merger fraction for lower mass primary galaxies M*<10^9.5^M_{sun}_, seems to follow a more constant evolutionary trend with redshift. Thanks to the addition of new MUSE fields and new selection criteria, the increased statistics of the pair samples allow to narrow significantly the error bars compared to our previous analysis (Ventou et al., 2017A&A...608A...9V). The evolution of the minor merger fraction is roughly constant with cosmic time, with a fraction of 20% at z<3 and a slow decrease between 3<z<6 to 8-13%.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/172
- Title:
- Cloud-scale molecular gas properties in 15 galaxies
- Short Name:
- J/ApJ/860/172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the velocity dispersion, {sigma}, and surface density, {Sigma}, of the molecular gas in nearby galaxies from CO spectral line cubes with spatial resolution 45-120pc, matched to the size of individual giant molecular clouds. Combining 11 galaxies from the PHANGS-ALMA survey with four targets from the literature, we characterize ~30000 independent sightlines where CO is detected at good significance. {Sigma} and {sigma} show a strong positive correlation, with the best-fit power-law slope close to the expected value for resolved, self-gravitating clouds. This indicates only a weak variation in the virial parameter {alpha}_vir_{propto}{sigma}^2^/{Sigma}, which is ~1.5-3.0 for most galaxies. We do, however, observe enormous variation in the internal turbulent pressure P_turb_{propto}{Sigma}{sigma}^2^, which spans ~5dex across our sample. We find {Sigma}, {sigma}, and P_turb_ to be systematically larger in more massive galaxies. The same quantities appear enhanced in the central kiloparsec of strongly barred galaxies relative to their disks. Based on sensitive maps of M31 and M33, the slope of the {sigma}-{Sigma} relation flattens at {Sigma}<~10M_{sun}_/pc^2^, leading to high {sigma} for a given {Sigma} and high apparent {alpha}_vir_. This echoes results found in the Milky Way and likely originates from a combination of lower beam-filling factors and a stronger influence of local environment on the dynamical state of molecular gas in the low-density regime.
- ID:
- ivo://CDS.VizieR/J/ApJ/853/108
- Title:
- Clumpy galaxies in CANDELS. II. 0.5<=z<3.0
- Short Name:
- J/ApJ/853/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studying giant star-forming clumps in distant galaxies is important to understand galaxy formation and evolution. At present, however, observers and theorists have not reached a consensus on whether the observed "clumps" in distant galaxies are the same phenomenon that is seen in simulations. In this paper, as a step to establish a benchmark of direct comparisons between observations and theories, we publish a sample of clumps constructed to represent the commonly observed "clumps" in the literature. This sample contains 3193 clumps detected from 1270 galaxies at 0.5<=z<3.0. The clumps are detected from rest-frame UV images, as described in our previous paper. Their physical properties (e.g., rest-frame color, stellar mass (M*), star formation rate (SFR), age, and dust extinction) are measured by fitting the spectral energy distribution (SED) to synthetic stellar population models. We carefully test the procedures of measuring clump properties, especially the method of subtracting background fluxes from the diffuse component of galaxies. With our fiducial background subtraction, we find a radial clump U-V color variation, where clumps close to galactic centers are redder than those in outskirts. The slope of the color gradient (clump color as a function of their galactocentric distance scaled by the semimajor axis of galaxies) changes with redshift and M* of the host galaxies: at a fixed M*, the slope becomes steeper toward low redshift, and at a fixed redshift, it becomes slightly steeper with M*. Based on our SED fitting, this observed color gradient can be explained by a combination of a negative age gradient, a negative E(B-V) gradient, and a positive specific SFR gradient of the clumps. We also find that the color gradients of clumps are steeper than those of intra-clump regions. Correspondingly, the radial gradients of the derived physical properties of clumps are different from those of the diffuse component or intra-clump regions.
- ID:
- ivo://CDS.VizieR/J/A+A/597/A122
- Title:
- Cluster and field elliptical galaxies at z~1.3
- Short Name:
- J/A+A/597/A122
- Date:
- 04 Feb 2022 00:04:27
- Publisher:
- CDS
- Description:
- The aim of this work is twofold: first, to assess whether the population of elliptical galaxies in cluster at z~1.3 differs from the population in the field and whether their intrinsic structure depends on the environment where they belong; second, to constrain their properties 9Gyr back in time through the study of their scaling relations. We compared a sample of 56 cluster elliptical galaxies selected from three clusters at 1.2<z<1.4 with elliptical galaxies selected at comparable redshift in the GOODS-South field (~30), in the COSMOS area (~180), and in the CANDELS fields (~220). To single out the environmental effects, we selected cluster and field elliptical galaxies according to their morphology. We compared physical and structural parameters of galaxies in the two environments and we derived the relationships between effective radius, surface brightness, stellar mass, and stellar mass density {Sigma}_R_e__ within the effective radius and central mass density {Sigma}_1kpc_, within 1kpc radius. We find that the structure and the properties of cluster elliptical galaxies do not differ from those in the field: they are characterized by the same structural parameters at fixed mass and they follow the same scaling relations. On the other hand, the population of field elliptical galaxies at z~1.3 shows a significant lack of massive (M_*_>2x10^11^M_{sun}_) and large (R_e_>4-5kpc) elliptical galaxies with respect to the cluster. Nonetheless, at M_*_<2x10^11^M_{sun}_, the two populations are similar. The size-mass relation of cluster and field ellipticals at z~1.3 clearly defines two different regimes, above and below a transition mass m_t_~=2-3x10^10^M_{sun}_ at lower masses the relation is nearly flat (R_e_{prop}M*^-0.1+/-0.2^), the mean radius is nearly constant at ~1kpc and, consequently, {Sigma}_Re_~={Sigma}_1kpc_ while, at larger masses, the relation is R_e_{prop}M*^0.64+/-0.09^. The transition mass marks the mass at which galaxies reach the maximum stellar mass density. Also the {Sigma}_1kpc_-mass relation follows two different regimes, above and below the transition mass ({Sigma}_1kpc_{prop}M*_1.07<mt_^0.64>mt^) defining a transition mass density {Sigma}_1kpc_~=2-3x10^3^M_{sun}_/pc^2^. The effective stellar mass density {Sigma}_Re_ does not correlate with mass; dense/compact galaxies can be assembled over a wide mass regime, independently of the environment. The central stellar mass density, {Sigma}_1kpc_, besides being correlated with the mass, is correlated to the age of the stellar population: the higher the central stellar mass density, the higher the mass, the older the age of the stellar population. While we found some evidence of environmental effects on the elliptical galaxies as a population, we did not find differences between the intrinsic properties of cluster and field elliptical galaxies at comparable redshift. The structure and the shaping of elliptical galaxies at z~1.3 do not depend on the environment. However, a dense environment seems to be more efficient in assembling high-mass large ellipticals, much rarer in the field at this redshift. The correlation found between the central stellar mass density and the age of the galaxies beside the mass shows the close connection of the central regions to the main phases of mass growth.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/835
- Title:
- Clustering of the SDSS DR7 main galaxy sample. I.
- Short Name:
- J/MNRAS/449/835
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We create a sample of spectroscopically identified galaxies with z<0.2 from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7, Cat. II/294), covering 6813 deg^2^. Galaxies are chosen to sample the highest mass haloes, with an effective bias of 1.5, allowing us to construct 1000 mock galaxy catalogues (described in Howlett et al. 2015MNRAS.449..848H), which we use to estimate statistical errors and test our methods. We use an estimate of the gravitational potential to "reconstruct" the linear density fluctuations, enhancing the baryon acoustic oscillation (BAO) signal in the measured correlation function and power spectrum. Fitting to these measurements, we determine D_V_(z_eff_=0.15)=(664+/-25)(r_d_/r_d_, _fid_) Mpc; this is a better than 4 per cent distance measurement. This "fills the gap" in BAO distance ladder between previously measured local and higher redshift measurements, and affords significant improvement in constraining the properties of dark energy. Combining our measurement with other BAO measurements from Baryon Oscillation Spectroscopic Survey and 6-degree Field Galaxy Redshift Survey galaxy samples provides a 15 per cent improvement in the determination of the equation of state of dark energy and the value of the Hubble parameter at z=0(H_0_). Our measurement is fully consistent with the Planck results and the {Lambda} cold dark matter concordance cosmology, but increases the tension between Planck+BAO H_0_ determinations and direct H_0_ measurements.
- ID:
- ivo://mast.stsci/clash
- Title:
- Cluster Lensing And Supernova survey with Hubble (CLASH)
- Short Name:
- HST.CLASH
- Date:
- 22 Jul 2020 22:29:29
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- By observing 25 massive galaxy clusters with HST's new panchromatic imaging capabilities (Wide-field Camera 3, WFC3, and the Advanced Camera for Surveys, ACS), CLASH will accomplish its four primary science goals: - Map, with unprecedented accuracy, the distribution of dark matter in galaxy clusters using strong and weak gravitational lensing; - Detect Type Ia supernovae out to redshift z ~ 2, allowing us to test the constancy of dark energy's repulsive force over time and look for any evolutionary effects in the supernovae themselves; - Detect and characterize some of the most distant galaxies yet discovered at z > 7 (when the Universe was younger than 800 million years old - or less than 6% of its current age); - Study the internal structure and evolution of the galaxies in and behind these clusters.
- ID:
- ivo://CDS.VizieR/J/AN/327/365
- Title:
- Clusters and groups of galaxies in 2dF
- Short Name:
- J/AN/327/365
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We create a new catalogue of groups and clusters, applying the friends-to-friends method to the 2dF GRS final release. We investigate various selection effects due to the use of a magnitude limited sample. For this purpose we follow the changes in group sizes and mean galaxy number densities within the groups when shifting nearby observed groups to larger distances. We study the distribution of sizes of dark matter haloes in N-body simulations and compare properties of these haloes and the 2dF groups.
- ID:
- ivo://CDS.VizieR/J/ApJ/767/51
- Title:
- Clusters of starburst galaxy NGC4214
- Short Name:
- J/ApJ/767/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The production rate of ionizing photons in young (<=8Myr), unresolved stellar clusters in the nearby irregular galaxy NGC 4214 is probed using multi-wavelength Hubble Space Telescope WFC3 data. We normalize the ionizing photon rate by the cluster mass to investigate the upper end of the stellar initial mass function (IMF). We have found that within the uncertainties the upper end of the stellar IMF appears to be universal in this galaxy, and that deviations from a universal IMF can be attributed to stochastic sampling of stars in clusters with masses {<~}10^3^M_{sun}_. Furthermore, we have found that there does not seem to be a dependence of the maximum stellar mass on the cluster mass. We have also found that for massive clusters, feedback may cause an underrepresentation in H{alpha} luminosities, which needs to be taken into account when conducting this type of analysis.
660. CMD for And III
- ID:
- ivo://CDS.VizieR/J/AJ/106/986
- Title:
- CMD for And III
- Short Name:
- J/AJ/106/986
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The prime focus CCD camera of the KPNO 4 m telescope has been used to image Andromeda III, a dwarf spheroidal galaxy companion to M31, in the V and I bands. The resulting color-magnitude diagram shows a well defined giant branch whose tip luminosity corresponds to that expected for an old metal-poor population at the distance of M31. By comparing these data with the giant branches of metal-poor population at the distance of M31. By comparing these data with the giant branches of Galactic globular clusters, we determine that the abundance of And III is [Fe/H]=-2.0+/-0.15; with this abundance And III lies on the luminosity-abundance relation defined by the Galactic dwarf spheroidal galaxies. There is some evidence for a small (0.16<{sigma}([Fe/H])<0.24) intrinsic abundance dispersion within And III, but we are unable to unambiguously establish its presence. A study of the And III I-band luminosity function yields a distance modulus (m-M)_0_ of 24.4+/-0.2 for this galaxy, and indicates that the fraction of intermediate-age (3 to 10Gyr) population in And III is approximately 10+/-10 percent. In all these aspects And III, like And I, is similar to the Galactic dwarf spheroidal systems, indicating that M31 and the Galaxy provided similar conditions for the evolution of such galaxies.
