- ID:
- ivo://CDS.VizieR/J/MNRAS/464/183
- Title:
- Segregation effects in DEEP2 galaxy groups
- Short Name:
- J/MNRAS/464/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate segregation phenomena in galaxy groups in the range of 0.2<z<1. We study a sample of groups selected from the 4th Data Release of the DEEP2 galaxy redshift survey. We used only groups with at least eight members within a radius of 4 Mpc. Outliers were removed with the shifting gapper technique and, then, the virial properties were estimated for each group. The sample was divided into two stacked systems: low(z<=0.6) and high (z>0.6) redshift groups. Assuming that the colour index (U-B)_0_ can be used as a proxy for the galaxy type, we found that the fraction of blue (star-forming) objects is higher in the high-z sample, with blue objects being dominant at M_B_>-19.5 for both samples, and red objects being dominant at M_B_<-19.5 only for the low-z sample. Also, the radial variation of the red fraction indicates that there are more red objects with R<R_200_ in the low-z sample than in the high-z sample. Our analysis indicates statistical evidence of kinematic segregation, at the 99 per cent c.l., for the low-z sample: redder and brighter galaxies present lower velocity dispersions than bluer and fainter ones. We also find a weaker evidence for spatial segregation between red and blue objects, at the 70 per cent c.l. The analysis of the high-z sample reveals a different result: red and blue galaxies have velocity dispersion distributions not statistically distinct, although redder objects are more concentrated than the bluer ones at the 95 per cent c.l. From the comparison of blue/red and bright/faint fractions, and considering the approximate lookback time-scale between the two samples (~3Gyr), our results are consistent with a scenario where bright red galaxies had time to reach energy equipartition, while faint blue/red galaxies in the outskirts infall to the inner parts of the groups, thus reducing spatial segregation from z~0.8 to z~0.4.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/3729
- Title:
- Sersic + exponential disc morphologies in Coma
- Short Name:
- J/MNRAS/453/3729
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxies are not limited to simple spheroid or bulge + disc morphologies. We explore the diversity of internal galaxy structures in the Coma Cluster across a wide range of luminosities (-17>Mg>-22) and cluster-centric radii (0<r_cluster_<1.3r_200_) through analysis of deep Canada-France-Hawaii Telescope i-band imaging. We present 2D multicomponent decomposition via galfit, encompassing a wide range of candidate model morphologies with up to three photometric components. Particular focus is placed on early-type galaxies with outer discs (i.e. S0s), and deviations from simple ('unbroken') exponential discs. Rigorous filtering ensures that each model component provides a statistically significant improvement to the goodness-of-fit. The majority of Coma Cluster members in our sample (478 of 631) are reliably fitted by symmetric structural models. Of these, 134 (28 percent) are single Sersic objects, 143 (30 percent) are well-described by 2-component structures, while 201 (42 percent) require more complex models. Multicomponent Sersic galaxies resemble compact pseudo-bulges (n~2, R_e_~4kpc) surrounded by extended Gaussian-like outer structures (R_e_>10kpc). 11 percent of galaxies (N=52) feature a break in their outer profiles, indicating 'truncated' or 'antitruncated' discs. Beyond the break radius, truncated galaxies are structurally consistent with exponential discs, disfavouring physical truncation as their formation mechanism. Bulge luminosity in antitruncated galaxies correlates strongly with galaxy luminosity, indicating a bulge-enhancing origin for these systems. Both types of broken disc are found overwhelmingly (>70 percent) in 'barred' galaxies, despite a low measured bar fraction for Coma (20+/-2 percent). Thus, galaxy bars play an important role in formation of broken disc structures. No strong variation in galaxy structure is detected with projected cluster-centric radius.
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/L63
- Title:
- SFRs of Brightest Cluster Galaxies
- Short Name:
- J/MNRAS/444/L63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the mid-infrared star formation rates of 245 X-ray selected, nearby (z<0.1) brightest cluster galaxies (BCGs). A homogeneous and volume limited sample of BCGs was created by X-ray selecting clusters with Lx>1x10^44^erg/s. The Wide-Field Infrared Survey Explorer (WISE) All WISE Data Release provides the first measurement of the 12{mu}m star formation indicator for all BCGs in the nearby Universe. Perseus A and Cygnus A are the only galaxies in our sample to have star formation rates of >40M_{sun}_/yr, indicating that these two galaxies are highly unusual at current times. Stellar populations of 99+/-0.6 per cent of local BCGs are (approximately) passively evolving, with star formation rates of <10M_{sun}_/yr. We find that in general, star formation produces only modest BCG growth at the current epoch.
- ID:
- ivo://CDS.VizieR/VII/196
- Title:
- Shakhbazian compact groups of galaxies
- Short Name:
- VII/196
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The largest survey of compact galaxy groups was published by Shakhbazian et al. (see cat. <VII/89>). This catalogue provides accurate positions of individual galaxies in the groups; photometrical properties of the Southern sky (delta not greater than +2{deg}30') are evaluated on the basis of the COSMOS/UKST catalog of the Southern sky. The catalogue contains 373 groups; this number differs from the number in Shakhbazian's list (377 groups) by the following: => No data for groups 001 (there were already published data by other authors), 206 (could not be re-identified) 241 (could not be re-identified) 252 (is identical with 214), 301 (could not be re-identified) 353 (could not be re-identified) => Group 328 was published twice (in North and South) => Group 340 was divided in two parts (340 and 340a), according to Bettoni and Fasano ([BF95]=1995AJ....109...32B)
- ID:
- ivo://CDS.VizieR/J/A+A/336/35
- Title:
- Shape and orientation of superclusters
- Short Name:
- J/A+A/336/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the shape, size, and spatial orientation of superclusters of galaxies. Approximating superclusters by triaxial ellipsoids we show that superclusters are flattened, triaxial objects. We find that there are no spherical superclusters. The sizes of superclusters grow with their richness: the median semi-major axis of rich and poor superclusters (having >=8 and <8 member clusters) is 42 and 31h^-1^Mpc, respectively. Similarly, the median semi-minor axis is 12 and 5h^-1^Mpc for rich and poor superclusters. The spatial orientation of superclusters, as determined from the axes of the ellipsoids, is nearly random. We do not detect any preferable orientation of superclusters, neither with respect to the line of sight, nor relative to some other outstanding feature in the large scale structure, nor with respect to the directions of principal axes of adjacent superclusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/345/1
- Title:
- Shape of CL 1358+62 galaxies
- Short Name:
- J/MNRAS/345/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of early-type galaxies, both in the local Universe and in clusters at medium redshifts, suggest that these galaxies often contain discs or disc-like structures. Using the results of Kelson et al. (2000ApJ...531..137K) for the incidence of disc-components among the galaxies in the redshift z=0.33 cluster CL 1358+62, we investigate the effect of disc structures on the lensing properties of early-type galaxies. Statistical properties, like magnification cross-sections and the expected number of quad (four-image) lens systems, are not affected greatly by the inclusion of discs that contain less than ~10 per cent of the total stellar mass.
- ID:
- ivo://CDS.VizieR/J/MNRAS/404/1490
- Title:
- Shapes of BCGs in nearby clusters shapes
- Short Name:
- J/MNRAS/404/1490
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare the apparent axial ratio distributions of the brightest cluster galaxies (BCGs) and normal ellipticals (Es) in our sample of 75 galaxy clusters from the WIde-field Nearby Galaxy-cluster Survey (WINGS). Most BCGs in our clusters (69 per cent) are classified as cD galaxies. The sample of cDs has been completed by 14 additional cDs (non-BCGs) we found in our clusters. We deproject the apparent axial ratio distributions of Es, BCGs and cDs using a bivariate version of the Lucy rectification algorithm, whose results are supported by an independent Monte Carlo technique. Finally, we compare the intrinsic shape distribution of BCGs to the corresponding shape distribution of the central part of cluster-sized dark matter haloes extracted from the GIF2 Lambda cold dark matter ({LAMBDA}CDM) N-body simulations (Gao et al., 2004MNRAS.355..819G).
- ID:
- ivo://CDS.VizieR/J/MNRAS/344/602
- Title:
- Shape statistics of SDSS superclusters
- Short Name:
- J/MNRAS/344/602
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the supercluster shape properties of the recently compiled Sloan Digital Sky Survey (SDSS) cluster catalogue using an approach based on differential geometry. We detect superclusters by applying the percolation algorithm to observed cluster populations, extended out to z_max_<=0.23 in order to avoid selection biases. We utilize a set of shapefinders in order to study the morphological features of superclusters with >=8 cluster members and find that filamentary morphology is the dominant supercluster shape feature, in agreement with previous studies.
- ID:
- ivo://CDS.VizieR/J/A+AS/125/247
- Title:
- Shapley Concentration galaxies velocities
- Short Name:
- J/A+AS/125/247
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report velocity measurements of galaxies in this, the densest mass concentration within z=0.1, obtained with the multifiber spectrograph MEFOS at ESO, La Silla. We derive redshifts of a number of Abell clusters and draw implications for the supercluster structure. The clusters A3554, A3566, A3577 and AS718 are confirmed as members, while the clusters A3524, A3531, A3542, A3545 and A3549 are shown to be background systems and A3581 a foreground one
- ID:
- ivo://CDS.VizieR/J/A+A/622/A83
- Title:
- Sizes of infinity regions
- Short Name:
- J/A+A/622/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Backreactions from large-scale inhomogeneities may provide an elegant explanation for the observed accelerated expansion of the universe without the need to introduce dark energy. We propose a cosmological test for a specific model of inhomogeneous cosmology, called timescape cosmology. Using large-scale galaxy surveys such as SDSS and 2MRS, we test the variation of expansion expected in the {Lambda}-CDM model versus a more generic differential expansion using our own calibrations of bounds suggested by timescape cosmology. Our test measures the systematic variations of the Hubble flow towards distant galaxies groups as a function of the matter distribution in the lines of sight to those galaxy groups. We compare the observed systematic variation of the Hubble flow to mock catalogues from the Millennium Simulation in the case of the {Lambda}-CDM model, and a deformed version of the same simulation that exhibits more pronounced differential expansion. We perform a series of statistical tests, ranging from linear regressions to Kolmogorov-Smirnov tests, on the obtained data. They consistently yield results preferring {Lambda}-CDM cosmology over our approximated model of timescape cosmology. Our analysis of observational data shows no evidence that the variation of expansion differs from that of the standard {Lambda}-CDM model.
