75 research outputs found
SDSS superclusters: morphology and galaxy content
We compare the galaxy populations in superclusters of different morphology in
the nearby Universe (180 < d < 270 Mpc) to see whether the inner structure and
overall morphology of superclusters are important in shaping galaxy properties
in superclusters. Supercluster morphology has been found with Minkowski
functionals. We analyse the probability density distributions of colours,
morphological types, stellar masses, star formation rates (SFR) of galaxies,
and the peculiar velocities of the main galaxies in groups in superclusters of
filament and spider types, and in the field. We show that the fraction of red,
early-type, low SFR galaxies in filament-type superclusters is higher than in
spider-type superclusters; in low-density global environments their fraction is
lower than in superclusters. In all environments the fraction of red, high
stellar mass, and low SFR galaxies in rich groups is higher than in poor
groups. In superclusters of spider morphology red, high SFR galaxies have
higher stellar masses than in filament-type superclusters. Groups of equal
richness host galaxies with larger stellar masses, a larger fraction of
early-type and red galaxies, and a higher fraction of low SFR galaxies, if they
are located in superclusters of filament morphology. The peculiar velocities of
the main galaxies in groups from superclusters of filament morphology are
higher than in those of spider morphology. Groups with higher peculiar
velocities of their main galaxies in filament-type superclusters are located in
higher density environment than those with low peculiar velocities. There are
significant differences between galaxy populations of the individual richest
superclusters. Therefore both local (group) and global (supercluster)
environments and even supercluster morphology play an important role in the
formation and evolution of galaxies.Comment: Comments: 14 pages, 11 figures, accepted for publication in Astronomy
and Astrophysic
Discovery of a massive supercluster system at
Superclusters are the largest relatively isolated systems in the cosmic web.
Using the SDSS BOSS survey we search for the largest superclusters in the
redshift range .
We generate a luminosity-density field smoothed over
to detect the large-scale over-density regions. Each individual over-density
region is defined as single supercluster in the survey. We define the
superclusters in the way that they are comparable with the superclusters found
in the SDSS main survey.
We found a system we call the BOSS Great Wall (BGW), which consists of two
walls with diameters 186 and 173 Mpc, and two other major superclusters
with diameters of 64 and 91 Mpc. As a whole, this system consists of
830 galaxies with the mean redshift 0.47. We estimate the total mass to be
approximately . The morphology of the
superclusters in the BGW system is similar to the morphology of the
superclusters in the Sloan Great Wall region.
The BGW is one of the most extended and massive system of superclusters yet
found in the Universe.Comment: 4 pages, accepted as a letter in A&
Environments of galaxies in groups within the supercluster-void network
Conclusions. Our results suggest that the evolution of galaxies is affected by both, the group in which the galaxy resides and its large-scale environment. Galaxies in lower-density regions develop later than galaxies in similar mass groups in high-density environmen
Large-scale environments of narrow-line Seyfert 1 galaxies
Studying large-scale environments of narrow-line Seyfert 1 (NLS1) galaxies gives a new perspective on their properties, particularly their radio loudness. The large-scale environment is believed to have an impact on the evolution and intrinsic properties of galaxies, however, NLS1 sources have not been studied in this context before. We have a large and diverse sample of 1341 NLS1 galaxies and three separate environment data sets constructed using Sloan Digital Sky Survey. We use various statistical methods to investigate how the properties of NLS1 galaxies are connected to the large-scale environment, and compare the large-scale environments of NLS1 galaxies with other active galactic nuclei (AGN) classes, for example, other jetted AGN and broad-line Seyfert 1 (BLS1) galaxies, to study how they are related. NLS1 galaxies reside in less dense environments than any of the comparison samples, thus confirming their young age. The average large-scale environment density and environmental distribution of NLS1 sources is clearly different compared to BLS1 galaxies, thus it is improbable that they could be the parent population of NLS1 galaxies and unified by orientation. Within the NLS1 class there is a trend of increasing radio loudness with increasing large-scale environment density, indicating that the large-scale environment affects their intrinsic properties. Our results suggest that the NLS1 class of sources is not homogeneous, and furthermore, that a considerable fraction of them are misclassified. We further support a published proposal to replace the traditional classification to radio-loud, and radio-quiet or radio-silent sources with a division into jetted and non-jetted sources
Clustering environment of BL Lac object RGB 1745+398
The BL Lac object RGB 1745+398 lies in an environment that makes it possible
to study the cluster around it more deeply than the environments of other BL
Lac objects. The cluster centered on the BL Lac works as a strong gravitational
lens, forming a large arc around itself. The aim of this paper is to study the
environment and characteristics of this object more accurately than the
environments of other BL Lac objects have been before.We measured the redshifts
of galaxies in the cluster from the absorption lines in their spectra. The
velocity dispersion was then obtained from the redshifts. The gravitational
lensing was used for measuring the mass at the center of the cluster. The mass
of the whole cluster could then be estimated using the softened isothermal
sphere mass distribution. Finally, the richness of the cluster was determined
by counting the number of galaxies near the BL Lac object and obtaining the
galaxy-BL Lac spatial covariance function, . The redshifts of nine
galaxies in the field were measured to be near the redshift of the BL Lac
object, confirming the presence of a cluster. The average redshift of the
cluster is 0.268, and the velocity dispersion km
s. The mass of the cluster is M_{500}=(4^{+3}_{-2})\times10^{14}
M_{\sun} which implies a rather massive cluster. The richness measurement also
suggests that this is a rich cluster: the result for covariance function is
Mpc, which corresponds to Abell richness class 1
and which is consistent with the mass and velocity dispersion of the cluster.Comment: 5 pages, accepted to A&
Multifrequency studies of galaxies and groups I. Environmental effect on galaxy stellar mass and morphology
Context. To understand the role of the environment in galaxy formation, evolution, and present-day properties, it is essential to study the multifrequency behavior of different galaxy populations under various environmental conditions.Aims. We study the stellar mass functions of different galaxy populations in groups as a function of their large-scale environments using multifrequency observations.Methods. We cross-matched the SDSS DR10 group catalog with GAMA Data Release 2 and Wide-field Survey Explorer (WISE) data to construct a catalog of 1651 groups and 11 436 galaxies containing photometric information in 15 different wavebands ranging from ultraviolet (0.152 mu m) to mid-infrared (22 mu m). We performed the spectral energy distribution (SED) fitting of galaxies using the MAGPHYS code and estimate the rest-frame luminosities and stellar masses. We used the 1/V-max method to estimate the galaxy stellar mass and luminosity functions, and the luminosity density field of galaxies to define the large-scale environment of galaxies.Results. The stellar mass functions of both central and satellite galaxies in groups are different in low-and high-density, large-scale environments. Satellite galaxies in high-density environments have a steeper low-mass end slope compared to low-density environments, independent of the galaxy morphology. Central galaxies in low-density environments have a steeper low-mass end slope, but the difference disappears for fixed galaxy morphology. The characteristic stellar mass of satellite galaxies is higher in high-density environments and the difference exists only for galaxies with elliptical morphologies.Conclusions. Galaxy formation in groups is more efficient in high-density, large-scale environments. Groups in high-density environments have higher abundances of satellite galaxies, irrespective of the satellite galaxy morphology. The elliptical satellite galaxies are generally more massive in high-density environments. The stellar masses of spiral satellite galaxies show no dependence on the large-scale environment
Environments of galaxies in groups within the supercluster-void network
Majority of all galaxies reside in groups of less than 50 member galaxies.
These groups are distributed in various large-scale environments from voids to
superclusters. Evolution of galaxies is affected by the environment in which
they reside. Our aim is to study the effects that the local group scale and the
supercluster scale environment have on galaxies. We use a luminosity-density
field to determine density of the large-scale environment of galaxies in groups
of various richness. We calculate fractions of different types of galaxies in
groups with richnesses up to 50 member galaxies and in different large-scale
environments from voids to superclusters. The fraction of passive elliptical
galaxies rises and the fraction of star-forming spiral galaxies declines when
the richness of a group of galaxies rises from two to approximately ten
galaxies. On the large scale, the passive elliptical galaxies become more
numerous than star-forming spirals when the environmental density grows to the
density level typical for superclusters. The large-scale environment affects
the level of these fractions in groups: galaxies in equally rich groups are
more likely to be elliptical in supercluster environments than in lower
densities. The crossing point, where the number of passive and star-forming
galaxies is equal, happens in groups with lower richness in superclusters than
in voids. Galaxies in low-density areas require richer groups to evolve from
star-forming to passive. Groups in superclusters are on average more luminous
than groups in large-scale environments with lower density. Our results suggest
that the evolution of galaxies is affected by both, by the group in which the
galaxy resides, and by its large-scale environment. Galaxies in lower-density
regions develop later than galaxies in similar mass groups in high-density
environments.Comment: 10 pages, 9 figures. Published in A&A. Language corrected 9th Oct
201
Childhood adversities and adult-onset asthma: a cohort study
Conclusions: Adults who report having encountered adversities in childhood may have an increased risk of developing asthma
Sloan Great Wall as a complex of superclusters with collapsing cores
Context. The formation and evolution of the cosmic web is governed by the gravitational attraction of dark matter and antigravity of dark energy (cosmological constant). In the cosmic web, galaxy superclusters or their high-density cores are the largest objects that may collapse at present or during the future evolution.Aims. We study the dynamical state and possible future evolution of galaxy superclusters from the Sloan Great Wall (SGW), the richest galaxy system in the nearby Universe.Methods. We calculated supercluster masses using dynamical masses of galaxy groups and stellar masses of galaxies. We employed normal mixture modelling to study the structure of rich SGW superclusters and search for components (cores) in superclusters. We analysed the radial mass distribution in the high-density cores of superclusters centred approximately at rich clusters and used the spherical collapse model to study their dynamical state.Results. The lower limit of the total mass of the SGW is approximately M = 2.5 x 10(16) h(-1) M-circle dot. Different mass estimators of superclusters agree well, the main uncertainties in masses of superclusters come from missing groups and clusters. We detected three high-density cores in the richest SGW supercluster (SCl 027) and two in the second richest supercluster (SCl 019). They have masses of 1.2-5.9 x 10(15) h(-1) M-circle dot and sizes of up to approximate to 60 h(-1) Mpc. The high-density cores of superclusters are very elongated, flattened perpendicularly to the line of sight. The comparison of the radial mass distribution in the high-density cores with the predictions of spherical collapse model suggests that their central regions with radii smaller than 8 h(-1) Mpc and masses of up to M = 2 x 10(15) h(-1) M-circle dot may be collapsing.Conclusions. The rich SGW superclusters with their high-density cores represent dynamically evolving environments for studies of the properties of galaxies and galaxy systems
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