116 research outputs found
Searching for rotating galaxy clusters in SDSS and 2dFGRS
We present a result of searching for galaxy clusters that show an indication
of global rotation using a spectroscopic sample of galaxies in SDSS and 2dFGRS.
We have determined the member galaxies of 899 Abell clusters covered in SDSS
and 2dFGRS using the redshift and the positional data of galaxies, and have
estimated the ratio of the cluster rotation amplitude to the cluster velocity
dispersion and the velocity gradient across the cluster. We have found 12
tentative rotating clusters that have large ratios of rotation amplitude to
dispersion and large velocity gradients. We have determined the morphological
parameters for 12 tentative rotating clusters using the positional information
of the member galaxies: the ellipticity of the dispersion ellipse is in the
range of 0.080.57, and the position angle of major or minor axis does not
appear to be related to the position angle of rotation axis. We have
investigated the substructures in the sample of tentative rotating clusters,
finding from the Dressler-Shectman plots that the majority (9 out of 12) of
clusters show an evidence of substructure due to the spatially correlated
velocities of galaxies. We have selected six probable rotating clusters (A0954,
A1139, A1399, A2162, A2169, and A2366) that show a single number density peak
around the cluster center with a spatial segregation of the high and low
velocity galaxies. We have found no strong evidences of a recent merging for
the probable rotating clusters: the probable rotating clusters do not deviate
significantly from the relation of the X-ray luminosity and the velocity
dispersion or the virial mass of the clusters, and two probable rotating
clusters (A0954 and A1399) have small values of the peculiar velocities and the
clustercentric distances of the brightest cluster galaxies.Comment: 33 pages, 9 figures. To appear in Ap
Unsupervised classification reveals new evolutionary pathways
While we already seem to have a general scenario of the evolution of
different types of galaxies, a complete and satisfactory understanding of the
processes that led to the formation of all the variety of today's galaxy types
is still beyond our reach. To solve this problem, we need both large datasets
reaching high redshifts and novel methodologies for dealing with them. The
VIPERS survey statistical power, which observed galaxies at , and the application of an unsupervised clustering algorithm allowed us to
distinguish 12 galaxy classes. Studies of their environmental dependence
indicate that this classification may actually reflect different galaxy
evolutionary paths. For instance, a class of the most passive red galaxies
gathers galaxies smaller than other red galaxies of a similar
stellar mass, revealing the first sample of red nuggets at intermediate
redshift. On the other end, a class of blue dwarf galaxies is composed mainly
of AGN, challenging commonly used mid-infrared AGN selections.Comment: Accepted for publication in the ML4ASTRO (ICML 2022) proceeding boo
The VIMOS Public Extragalactic Redshift Survey (VIPERS). Never mind the gaps: comparing techniques to restore homogeneous sky coverage
[Abridged] Non-uniform sampling and gaps in sky coverage are common in galaxy
redshift surveys, but these effects can degrade galaxy counts-in-cells and
density estimates. We carry out a comparison of methods that aim to fill the
gaps to correct for the systematic effects. Our study is motivated by the
analysis of the VIMOS Extragalactic Redshift Survey (VIPERS), a flux-limited
survey (i<22.5) based on one-pass observations with VIMOS, with gaps covering
25% of the surveyed area and a mean sampling rate of 35%. Our findings are
applicable to other surveys with similar observing strategies. We compare 1)
two algorithms based on photometric redshift, that assign redshifts to galaxies
based on the spectroscopic redshifts of the nearest neighbours, 2) two Bayesian
methods, the Wiener filter and the Poisson-Lognormal filter. Using galaxy mock
catalogues we quantify the accuracy of the counts-in-cells measurements on
scales of R=5 and 8 Mpc/h after applying each of these methods. We also study
how they perform to account for spectroscopic redshift error and inhomogeneous
and sparse sampling rate. We find that in VIPERS the errors in counts-in-cells
measurements on R<10 Mpc/h scales are dominated by the sparseness of the
sample. All methods underpredict by 20-35% the counts at high densities. This
systematic bias is of the same order as random errors. No method outperforms
the others. Random and systematic errors decrease for larger cells. We show
that it is possible to separate the lowest and highest densities on scales of 5
Mpc/h at redshifts 0.5<z<1.1, over a large volume such as in VIPERS survey.
This is vital for the characterisation of cosmic variance and rare populations
(e.g, brightest galaxies) in environmental studies at these redshifts.Comment: 17 pages, 13 figures, accepted for publication in A&A (revised
version after minor revision and language editing
XMM-Newton Observations of A133: A Weak Shock Passing through the Cool Core
We use XMM-Newton observations of the cluster of galaxies A133 to study the
X-ray spectrum of the intracluster medium (ICM). We find a cold front to the
southeast of the cluster core. From the pressure profile near the cold front,
we derive an upper limit to the velocity of the core relative to the rest of
the cluster of <230 km s^-1. Our previous Chandra image of A133 showed a
complex, bird-like morphology in the cluster core. Based on the XMM-Newton
spectra and hardness ratio maps, we argue that the wings of this structure are
a weak shock front. The shock was probably formed outside the core of the
cluster, and may be heating the cluster core. Our Chandra image also showed a
``tongue'' of relatively cool gas extending from the center of the cD to the
center of the radio relic. The XMM-Newton results are consistent with the idea
that the tongue is the gas which has been uplifted by a buoyant radio bubble
including the radio relic to the northwest of the core. Alternatively, the
tongue might result from a cluster merger. The small velocity of the core
suggests that the bubble including the relic has moved by buoyancy, rather than
by motions of the core or the ICM. We do not find clear evidence for nonthermal
X-ray emission from the radio relic. Based on the upper limit on the inverse
Compton emission, we derive a lower limit on the magnetic field in the relic of
B>~1.5\mu G.Comment: 29 pages, ApJ in pres
Decoding the IRX-\beta\ dust attenuation relation in star-forming galaxies at intermediate redshift
We aim to understand what drives the IRX-\beta dust attenuation relation at
intermediate redshift (0.5 < z < 0.8) in star-forming galaxies. We investigate
the role of various galaxy properties in shaping this observed relation. We use
robust [O ii] {\lambda}3727, [O iii] {\lambda}{\lambda}4959, 5007, and H\beta
line detections of our statistical sample of 1049 galaxies to estimate the
gas-phase metallicities. We derive key physical properties that are necessary
to study galaxy evolution, such as the stellar masses and the star formation
rates, using the spectral energy distribution fitting tool CIGALE.
Equivalently, we study the effect of galaxy morphology (mainly the S\'ersic
index n and galaxy inclination) on the observed IRX-\beta scatter. We also
investigate the role of the environment in shaping dust attenuation in our
sample. We find a strong correlation of the IRX-\beta relation on gas-phase
metallicity in our sample, and also strong correlation with galaxy compactness
characterized by the S\'ersic indexes. Correlations are also seen with stellar
masses, specific star formation rates and the stellar ages of our sources.
Metallicity strongly correlates with the IRX-\beta scatter, this also results
from the older stars and higher masses at higher beta values. Galaxies with
higher metallicities show higher IRX and higher beta values. The correlation
with specific dust mass strongly shifts the galaxies away from the IRX-\beta
relation towards lower \b{eta} values. We find that more compact galaxies
witness a larger amount of attenuation than less compact galaxies. There is a
subtle variation in the dust attenuation scatter between edge-on and face-on
galaxies, but the difference is not statistically significant. Galaxy
environments do not significantly affect dust attenuation in our sample of
star-forming galaxies at intermediate redshift.Comment: 14 pages, 13 figures, accepted for publication in A&
The VIMOS Public Extragalactic Redshift Survey (VIPERS). Exploring the dependence of the three-point correlation function on stellar mass and luminosity at 0.5<z<1.1
The three-point correlation function (3PCF) is a powerful probe to
investigate the clustering of matter in the Universe in a complementary way
with respect to lower-order statistics, providing additional information with
respect to the two-point correlation function and allowing us to shed light on
biasing, nonlinear processes, and deviations from Gaussian statistics. In this
paper, we analyse the first data release of the VIMOS Public Extragalactic
Redshift Survey (VIPERS), determining the dependence of the three-point
correlation function on luminosity and stellar mass at . We
exploit the VIPERS Public Data Release 1, consisting of more than 50,000
galaxies with B-band magnitudes in the range and stellar masses in the range
. We measure both the
connected 3PCF and the reduced 3PCF in redshift space, probing different
configurations and scales, in the range [Mpc/h]. We find a
significant dependence of the reduced 3PCF on scales and triangle shapes, with
stronger anisotropy at larger scales ( Mpc/h) and an almost flat trend
at smaller scales, Mpc/h. Massive and luminous galaxies present a
larger connected 3PCF, while the reduced 3PCF is remarkably insensitive to
magnitude and stellar masses in the range we explored. These trends, already
observed at low redshifts, are confirmed for the first time to be still valid
up to , providing support to the hierarchical scenario for which massive
and bright systems are expected to be more clustered. The possibility of using
the measured 3PCF to provide independent constraints on the linear galaxy bias
has also been explored, showing promising results in agreement with other
probes.Comment: 12 pages, 11 figures, 2 tables, accepted for publication in A&
The VIMOS Public Extragalactic Redshift Survey (VIPERS): PCA-based automatic cleaning and reconstruction of survey spectra
Identifying spurious reduction artefacts in galaxy spectra is a challenge for
large surveys. We present an algorithm for identifying and repairing residual
spurious features in sky-subtracted galaxy spectra with application to the
VIPERS survey. The algorithm uses principal component analysis (PCA) applied to
the galaxy spectra in the observed frame to identify sky line residuals
imprinted at characteristic wavelengths. We further model the galaxy spectra in
the rest-frame using PCA to estimate the most probable continuum in the
corrupted spectral regions, which are then repaired. We apply the method to
90,000 spectra from the VIPERS survey and compare the results with a subset
where careful editing was performed by hand. We find that the automatic
technique does an extremely good job in reproducing the time-consuming manual
cleaning and does it in a uniform and objective manner across a large data
sample. The mask data products produced in this work are released together with
the VIPERS second public data release (PDR-2).Comment: Find the VIPERS data release at http://vipers.inaf.i
The VIMOS Public Extragalactic Survey (VIPERS): First Data Release of 57 204 spectroscopic measurements
We present the first Public Data Release (PDR-1) of the VIMOS Public
Extragalactic Survey (VIPERS). It comprises 57 204 spectroscopic measurements
together with all additional information necessary for optimal scientific
exploitation of the data, in particular the associated photometric measurements
and quantification of the photometric and survey completeness. VIPERS is an ESO
Large Programme designed to build a spectroscopic sample of ' 100 000 galaxies
with iAB < 22.5 and 0.5 < z < 1.5 with high sampling rate (~45%). The survey
spectroscopic targets are selected from the CFHTLS-Wide five-band catalogues in
the W1 and W4 fields. The final survey will cover a total area of nearly 24
deg2, for a total comoving volume between z = 0.5 and 1.2 of ~4x10^7
h^(-3)Mpc^3 and a median galaxy redshift of z~0.8. The release presented in
this paper includes data from virtually the entire W4 field and nearly half of
the W1 area, thus representing 64% of the final dataset. We provide a detailed
description of sample selection, observations and data reduction procedures; we
summarise the global properties of the spectroscopic catalogue and explain the
associated data products and their use, and provide all the details for
accessing the data through the survey database (http://vipers.inaf.it) where
all information can be queried interactively.Comment: Accepted for publication in A&A Added and/or replaced some figure,
added section on DataBase interface, expaned Introductio
Assessment of adipokines, adenine nucleotides and uric acid in the dynamics of coronary intervention
Introduction: The association of vaspin
and visfatin, with a myocardial infarction is still
not fully understood. Reduced levels of adenine
nucleotides are hallmarks of chronic heart failure.
There is little data concerning the relationship
between these markers and their changes over time.
Material/Methods: The concentration of adenine
nucleotides, vaspin and visfatinwere assessed in 41
consecutive patients with acute myocardial infarction one
before (day I) and four days after (day IV) percutaneous
coronary intervention (PCI) and a control group.
Results: Visfatin concentrations were higher before and
after PCI vs. control (visfatin I: median 25.55, 20.12 - 30.69
ng/ml; visfatin IV: median 20.79, 16.89 - 25.61 ng/ml vs.
control: median 14.94, 10.66 - 25.25 ng/ml; p < 0.0001).
Vaspin concentrations were lower before and after PCI vs.
control (vaspin I: median 0.18, 0.11 - 0.44 ng/ml; vaspin IV:
median 0.24, 0.15 - 0.58 ng/ml vs. control: median 1.303,
1.13 - 2.26 ng/ml, p < 0.00001). Concentrations of visfatin, day I, correlated well to vaspin concentrations (r2 = 0.201,
p = 0.011). ATP levels were significantly lower in patients
vs. controls (day I: p = 0.00012; day IV: p = 0.0001).
Conclusions: Changes in the analyzed visfatin and vaspin
concentrations can be used as potential MI markers.
Visfatin serum concentration may be considered a
potential marker to differentiate MI over time
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