230 research outputs found
The Evolution of Spheroidal Galaxies in Different Environments
We analyse the kinematic and chemical evolution of 203 distant spheroidal
(elliptical and S0) galaxies at 0.2<z<0.8 which are located in different
environments (rich clusters, low-mass clusters and in the field). VLT/FORS and
CAHA/MOSCA spectra with intermediate-resolution have been acquired to measure
the internal kinematics and stellar populations of the galaxies. From HST/ACS
and WFPC2 imaging, surface brightness profiles and structural parameters were
derived for half of the galaxy sample. The scaling relations of the
Faber-Jackson relation and Kormendy relation as well as the Fundamental Plane
indicate a moderate evolution for the whole galaxy population in each density
regime. In all environments, S0 galaxies show a faster evolution than
elliptical galaxies. For the cluster galaxies a slight radial dependence of the
evolution out to one virial radius is found. Dividing the samples with respect
to their mass, a mass dependent evolution with a stronger evolution of
lower-mass galaxies (M<2x10^{11} M_{\sun}) is detected. Evidence for recent
star formation is provided by blue colours and weak OII emission or strong
H\delta absorption features in the spectra. The results are consistent with a
down-sizing formation scenario which is independent from the environment of the
galaxies.Comment: 4 pages, 2 figures, to be published in Astronomische Nachrichten
(proceedings of Symposium 6 of the JENAM 2008, Vienna
Substructure in lensing clusters and simulations
We present high-resolution mass reconstructions for five massive
cluster-lenses spanning a redshift range from --0.57 utilising
archival {\it Hubble Space Telescope} ({\it HST}) data and applying
galaxy-galaxy lensing techniques. These detailed mass models were obtained from
the observations by combining constraints from the strong and weak lensing
regimes. We ascribe local weak distortions in the shear maps to perturbations
induced by the presence of galaxy haloes around individual bright early-type
cluster member galaxies. This technique constrains the mass enclosed within an
aperture for these subhaloes. We are sensitive to a specific mass range for
these subhaloes, -- 10^{12.5} \msun, which we associate with
galaxy-scale subhaloes. Adopting a parametric model for the subhaloes, we also
derive their velocity dispersion function and the aperture radius function. The
mass spectrum of substructure in the inner regions of the observed clusters is
directly compared with that in simulated clusters extracted from the {\it
Millennium Simulation}. The massfunction, aperture radii and velocity
dispersion function are compared in detail. Overall, we find good agreement
between the distribution of substructure properties retrieved using the lensing
analysis and those obtained from the simulation (truncated abstract).Comment: 15 pages, 5 figures, 2 tables, in press MNRA
The Evolution of Field Early-Type Galaxies in the FDF and WHDF
We explore the properties of 24 field early-type galaxies at 0.20<z<0.75 down
to M_B<=-19.30 in a sample extracted from the FORS Deep Field and the William
Herschel Deep Field. High S/N intermediate-resolution VLT spectroscopy was
complemented by deep high-resolution HST/ACS imaging and additional
ground-based multi-band photometry. To clarify the low level of star formation
(SF) detected in some galaxies, we identify the amount of AGN activity in our
sample using archive data of Chandra and XMM-Newton X-ray surveys. The B and
K-band Faber-Jackson relations and the Fundamental Plane display a moderate
evolution for the field early-type galaxies. Lenticular (S0) galaxies feature
on average a stronger luminosity evolution and bluer rest-frame colours which
can be explained that they comprise more diverse stellar populations compared
to elliptical galaxies. The evolution of the FP can be interpreted as an
average change in the dynamical mass-to-light ratio of our galaxies as <\Delta
\log{(M/L_B)}/z>=-0.74\pm0.08. The M/L evolution of these field galaxies
suggests a continuous mass assembly of field early-type galaxies during the
last 5 Gyr, that gets support by recent studies of field galaxies up to z~1.
Independent evidence for recent SF activity is provided by spectroscopic (OII
em., Hdelta) and photometric (rest-frame colors) diagnostics. Based on the
Hdelta absorption feature we detect a weak residual SF for galaxies that
accounts for 5%-10% in the total stellar mass of these galaxies. The
co-evolution in the luminosity and mass of our galaxies favours a downsizing
formation process. We find some evidence that our galaxies experienced a period
of SF quenching, possible triggered by AGN activity that is in good agreement
with recent results on both observational and theoretical side. (abridged)Comment: 26 pages, 23 figures, accepted for publication in MNRA
CLASH-VLT: Environment-driven evolution of galaxies in the z=0.209 cluster Abell 209
The analysis of galaxy properties and the relations among them and the
environment, can be used to investigate the physical processes driving galaxy
evolution. We study the cluster A209 by using the CLASH-VLT spectroscopic data
combined with Subaru photometry, yielding to 1916 cluster members down to a
stellar mass of 10^{8.6} Msun. We determine: i) the stellar mass function of
star-forming and passive galaxies; ii) the intra-cluster light and its
properties; iii) the orbits of low- and high-mass passive galaxies; and iv) the
mass-size relation of ETGs. The stellar mass function of the star-forming
galaxies does not depend on the environment, while the slope found for passive
galaxies becomes flatter in the densest region. The color distribution of the
intra-cluster light is consistent with the color of passive members. The
analysis of the dynamical orbits shows that low-mass passive galaxies have
tangential orbits, avoiding small pericenters around the BCG. The mass-size
relation of low-mass passive ETGs is flatter than that of high mass galaxies,
and its slope is consistent with that of field star-forming galaxies. Low-mass
galaxies are also more compact within the scale radius of 0.65 Mpc. The ratio
between stellar and number density profiles shows a mass segregation in the
center. The comparative analysis of the stellar and total density profiles
indicates that this effect is due to dynamical friction. Our results are
consistent with a scenario in which the "environmental quenching" of low-mass
galaxies is due to mechanisms such as harassment out to R200, starvation and
ram-pressure stripping at smaller radii, as supported by the analysis of the
mass function, of the dynamical orbits and of the mass-size relation of passive
early-types in different regions. Our analyses support the idea that the
intra-cluster light is formed through the tidal disruption of subgiant
galaxies.Comment: 17 pages, 20 figures, A&A in pres
Measurement of ion emission from plasmas obtained with a 600Â fs KrF laser
Ion emission from plasmas obtained by the use of a 600Â fs, 36Â mJ KrF laser operating at 248Â nm was measured and analysed for a variety of targets at different laser intensities. The intensity was set by changing the distance between the focusing lens and the target. It was found that the ions emitted originate from impurities and ions from the bulk of the target can be produced only in the subsequent shots. Proton emission was identified from some targets, but the energy of the protons was low (less than 12Â keV). A new silicon carbide semiconductor detector proved to be applicable for the collection of the ions
CLASH-VLT: Substructure in the galaxy cluster MACS J1206.2-0847 from kinematics of galaxy populations
In the effort to understand the link between the structure of galaxy clusters
and their galaxy populations, we focus on MACSJ1206.2-0847 at z~0.44 and probe
its substructure in the projected phase space through the spectrophotometric
properties of a large number of galaxies from the CLASH-VLT survey. Our
analysis is mainly based on an extensive spectroscopic dataset of 445 member
galaxies, mostly acquired with VIMOS@VLT as part of our ESO Large Programme,
sampling the cluster out to a radius ~2R200 (4 Mpc). We classify 412 galaxies
as passive, with strong Hdelta absorption (red and blue galaxies, and with
emission lines from weak to very strong. A number of tests for substructure
detection are applied to analyze the galaxy distribution in the velocity space,
in 2D space, and in 3D projected phase-space. Studied in its entirety, the
cluster appears as a large-scale relaxed system with a few secondary, minor
overdensities in 2D distribution. We detect no velocity gradients or evidence
of deviations in local mean velocities. The main feature is the WNW-ESE
elongation. The analysis of galaxy populations per spectral class highlights a
more complex scenario. The passive galaxies and red strong Hdelta galaxies
trace the cluster center and the WNW-ESE elongated structure. The red strong
Hdelta galaxies also mark a secondary, dense peak ~2 Mpc at ESE. The emission
line galaxies cluster in several loose structures, mostly outside R200. The
observational scenario agrees with MACS J1206.2-0847 having WNW-ESE as the
direction of the main cluster accretion, traced by passive galaxies and red
strong Hdelta galaxies. The red strong Hdelta galaxies, interpreted as
poststarburst galaxies, date a likely important event 1-2 Gyr before the epoch
of observation. The emission line galaxies trace a secondary, ongoing infall
where groups are accreted along several directions.Comment: A&A accepted, 19 pages, 30 figures, minor language change
Evolution of the infrared Tully-Fisher relation up to z=1.4
The Tully-Fisher relation (TFR) represents a connection between fundamental
galaxy parameters, such as its total mass and the mass locked in stars.
Therefore, the study of the evolution of this relation in the optical and
infrared bands can provide valuable information about the evolution of the
individual galaxies through the changes found in each band. This work aims to
study the TFR at high redshift in the B, V, R, I, and K-bands by comparison
with the local relations derived from a large sample of galaxies in the
redshift range 0.1<z<0.3, processed in the same way, and with the same
instrumental constraints that the high-redshift sample. Using the large
photometric information available in the AEGIS database, we have studied the
best procedure to obtain reliable k-corrections. Instrumental magnitudes are
then k and extinction corrected and the absolute magnitudes derived, using the
concordance cosmological model. The rotational velocities have been obtained
from the widths of optical lines using DEEP2 spectra. Finally, morphology has
been determined via visual classification of the HST images. We detect
evolution in the B, V and R-band TFRs in the sense that galaxies were brighter
in the past for the same rotation velocity. The change in luminosity is more
noticeable in the bluer bands. This colour evolution, unnoticed in our previous
work (Fern\'andez Lorenzo et al. 2009) has been detected thanks to the more
reliable k-corrections carried out in this paper, which included photometry
from B to IRAC bands. The change in the (V-K) and (R-I) colours (for a fixed
velocity) could be interpreted as an ageing of the stellar populations as
consequence of the star formation decrease since z=1.25. In addition, we
conclude that spiral galaxies could have doubled their stellar masses in the
last 8.6 Gyr.Comment: 14 pages, 10 figures; accepted in A&
The Tully-Fisher relation of distant cluster galaxies
We have measured maximum rotation velocities (Vrot) for a sample of 111
emission-line galaxies with 0.1 < z < 1, observed in the fields of 6 clusters.
From these data we construct 'matched' samples of 58 field and 22 cluster
galaxies, covering similar ranges in redshift (0.25 < z < 1.0) and luminosity
(M_B < -19.5 mag), and selected in a homogeneous manner. We find the
distributions of M_B, Vrot, and scalelength, to be very similar for the two
samples. However, using the Tully-Fisher relation (TFR) we find that cluster
galaxies are systematically offset with respect to the field sample by
-0.7+-0.2 mag. This offset is significant at 3 sigma and persists when we
account for an evolution of the field TFR with redshift. Extensive tests are
performed to investigate potential differences between the measured emission
lines and derived rotation curves of the cluster and field samples. However, no
such differences which could affect the derived Vrot values and account for the
offset are found. The most likely explanation for the TFR offset is that giant
spiral galaxies in distant clusters are on average brighter, for a given
rotation velocity, than those in the field. We discuss the potential mechanisms
responsible for this, and consider alternative explanations.Comment: 19 pages, 13 figures, accepted by MNRA
On positivity of Ehrhart polynomials
Ehrhart discovered that the function that counts the number of lattice points
in dilations of an integral polytope is a polynomial. We call the coefficients
of this polynomial Ehrhart coefficients, and say a polytope is Ehrhart positive
if all Ehrhart coefficients are positive (which is not true for all integral
polytopes). The main purpose of this article is to survey interesting families
of polytopes that are known to be Ehrhart positive and discuss the reasons from
which their Ehrhart positivity follows. We also include examples of polytopes
that have negative Ehrhart coefficients and polytopes that are conjectured to
be Ehrhart positive, as well as pose a few relevant questions.Comment: 40 pages, 7 figures. To appear in in Recent Trends in Algebraic
Combinatorics, a volume of the Association for Women in Mathematics Series,
Springer International Publishin
Archival biogenic micro- and nanostructure data analysis: Signatures of diagenetic systems
The present data in brief article provides additional data and information to our research article "Micro- and nanostructures reflect the degree of diagenetic alteration in modern and fossil brachiopod shell calcite: a multi-analytical screening approach (CL, FE-SEM, AFM, EBSD)" [1] (Casella et al.). We present fibre morphology, nano- and microstructure, as well as calcite crystal orientations and textures found in pristine, experimentally altered (hydrothermal and thermal), and diagenetically overprinted brachiopod shells. Combination of the screening tools AFM, FE-SEM, and EBSD allows to observe a significant change in microstructural and textural features with an increasing degree of laboratory based and naturally occurring diagenetic alteration. Amalgamation of neighbouring fibres was observed on the micrometre scale level, whereas progressive decomposition of biopolymers in the shells and fusion of nanoparticulate calcite crystals was detected on the nanometre scale. The presented data in this article and the study described in [1] allows for qualitative information on the degree of diagenetic alteration of fossil archives used for palaeoclimate reconstruction
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