4,010 research outputs found
Surface Photometry of Early-type Galaxies in the Hubble Deep Field
The detailed surface photometry of a sample of early-type galaxies in the
Hubble Deep Field is presented as part of a long-term project aimed to settle
strong observational constraints to the theories modelling the evolution of
elliptical galaxies from the early stages. The sample has been extracted, in
the V_606 band, from the catalog by Couch (1996). The analysis of the
luminosity and geometrical profiles, carried out on 162 candidates obeying our
provisional selection criteria, resulted in a list of 99 'bona fide' early-type
galaxies, for which accurate total magnitudes and effective radii were
computed. The comparison with the magnitudes given by Williams et al.(1996)
indicates that the automated photometry tends to underestimate the total
luminosity of the ellipticals. The luminosity profiles of most of galaxies in
our sample follow fairly well the deVaucouleurs law (`Normal' profiles).
However, a relevant fraction of galaxies, even following the deVaucouleurs law
in the main body light distribution, exhibit in the inner region a flattening
of the luminosity profile not attributable to the PSF (`Flat' profiles) or, in
some cases, a complex (multi-nucleus) structure (`Merger' profiles). The
average ellipticity of galaxies belonging to the `Flat' and `Merger' classes is
found to be significantly higher than that of the `Normal' galaxies. Moreover,
even taken into account the relevant uncertainty of the outer position angle
profiles, the amount of isophotal twisting of HDF ellipticals turns out to be
significantly larger with respect to that of the local samples.Comment: 22 pages, LaTeX with laa.sty and psfig.sty macros + 28 embedded
postscript figures. To appear in Astronomy and Astrophysics Supp
The scaling relations of early--type galaxies in clusters I. Surface photometry in seven nearby clusters
This is the first paper of a series investigating the scaling relations of
early-type galaxies in clusters. Here we illustrate the multi-band imagery and
the image reduction and calibration procedures relative to the whole sample of
22 clusters at 0.05 < z < 0.25. We also present the detailed surface photometry
of 312 early-type galaxies in 7 clusters in the first redshift bin,
z~0.025-0.075. We give for each galaxy the complete set of luminosity and
geometrical profiles, and and a number of global, photometric and morphological
parameters. They have been evaluated taking into account the effects of seeing.
Internal consistency checks and comparisons with data in the literature confirm
the quality of our analysis. These data, together with the spectroscopic ones
presented in the second paper of the series, will provide the local calibration
of the scaling relations.Comment: 36 pages, 13 figures, 7 tables, accepted for publication in A&
Critical current and topology of the supercooled vortex state in NbSe2
We study the behavior of the critical current, Ic(H,T), of pure and Fe doped
NbSe2 crystals in the denominated disordered vortex region, limited by the
critical field Hc2(T) and the field Hp(T) at which the peak effect in Ic(H,T)
is detected. The critical current follows an individual pinning response as
demonstrated by its field independent universal function of the superfluid
density. Transport measurements combined with Bitter decorations show no
evidence of the existence of an amorphous phase in the high temperature region.Comment: 7 pages, figures included. Submitted to Phys. Rev.
IL-1 regulates the IL-23 response to wheat gliadin, the etiologic agent of Celiac Disease
Celiac disease (CD) is an autoimmune disease prevalent in ~1% of the general population. CD is unique because both the major genetic (Human Leukocyte Antigen-DQ2/DQ8 alleles) and etiologic factors (dietary glutens) for susceptibility are known. While these alleles are responsible for the inappropriate T cell response that characterizes CD, they are not sufficient since most HLA-DQ2+/DQ8+ individuals exposed to glutens never develop disease. The reasons for this have not been explained; however our novel findings strongly advocate a role for interleukin-23 (IL-23) in the immunopathogenesis of CD. We demonstrate that wheat gliadin stimulates monocytes to produce significantly higher amounts of inflammatory cytokines IL-1b, IL-23, and tumor necrosis factor-a (TNFa) in CD patients compared to HLA-DQ2+ healthy individuals. Furthermore, we determine that IL-1 signalling is obligatory for production of IL-23, since IL-1b triggers IL-23 secretion in a dose-dependent manner and IL-1 receptor antagonist (IL-1ra) blocks IL-23 responses to gliadin. Our results suggest that gliadin activation of monocytes and the subsequent robust secretion of IL-1b and IL-23 initiate the immune response cascade that is manifest as CD, and reveal for the first time that the IL-1 system regulates production of IL-23. The discovery of IL-23 has highlighted the critical role of the innate immune response in autoimmunity and other inflammatory conditions. We anticipate that our novel findings will lead to the discovery of therapeutic targets for this disease and other inflammatory diseases mediated by IL-23
The Birthplace of Low-Mass X-ray Binaries: Field Versus Globular Cluster Populations
Recent Chandra studies of low-mass X-ray binaries (LMXBs) within early-type
galaxies have found that LMXBs are commonly located within globular clusters of
the galaxies. However, whether all LMXBs are formed within globular clusters
has remained an open question. If all LMXBs formed within globular clusters,
the summed X-ray luminosity of the LMXBs in a galaxy should be directly
proportional to the number of globular clusters in the galaxy regardless of
where the LMXBs currently reside. We have compared these two quantities over
the same angular area for a sample of 12 elliptical and S0 galaxies observed
with Chandra and found that the correlation between the two quantities is
weaker than expected if all LMXBs formed within globular clusters. This
indicates that a significant number of the LMXBs were formed in the field, and
naturally accounts for the spread in field-to-cluster fractions of LMXBs from
galaxy to galaxy. We also find that the "pollution" of globular cluster LMXBs
into the field has been minimal within elliptical galaxies, but there is
evidence that roughly half of the LMXBs originally in the globular clusters of
S0 galaxies in our sample have escaped into the field. This is due to higher
globular cluster disruption rates in S0s resulting from stronger gravitational
shocks caused by the passage of globular clusters through the disks of S0
galaxies that are absent in elliptical galaxies.Comment: To appear in ApJ, 1 October 2005, v631 2 issue, 9 pages, 3 figures,
typos and a few minor issues correcte
Latent-heat and non-linear vortex liquid at the vicinity of the first-order phase transition in layered high-Tc superconductors
In this work we revisit the vortex matter phase diagram in layered
superconductors solving still open questions by means of AC and DC local
magnetic measurements in the paradigmatic BiSrCaCuO
compound. We show that measuring with AC magnetic techniques is mandatory in
order to probe the bulk response of vortex matter, particularly at
high-temperatures where surface barriers for vortex entrance dominate. From the
-evolution of the enthalpy and latent-heat at the transition we
find that, contrary to previous reports, the nature of the dominant interlayer
coupling is electromagnetic in the whole temperature range. By studying the
dynamic properties of the phase located at , we reveal
the spanning in a considerable fraction of the phase diagram of a non-linear
vortex phase suggesting bulk pinning might play a role even in the liquid
vortex phase.Comment: arXiv admin note: substantial text overlap with arXiv:1212.456
The evolution of the galactic morphological types in clusters
The morphological types of galaxies in nine clusters in the redshift range
0.1<z<0.25 are derived from very good seeing images taken at the NOT and the La
Silla Danish telescopes. With the purpose of investigating the evolution of the
fraction of different morphological types with redshift, we compare our results
with the morphological content of nine distant clusters studied by the MORPHS
group, five clusters observed with HST-WFPC2 at redshift z = 0.2-0.3, and
Dressler's (1980) large sample of nearby clusters. After having checked the
reliability of our morphological classification both in an absolute sense and
relative to the MORPHS scheme, we analyze the relative occurrence of
elliptical, S0 and spiral galaxies as a function of the cluster properties and
redshift. We find a large intrinsic scatter in the S0/E ratio, mostly related
to the cluster morphology. In particular, in our cluster sample, clusters with
a high concentration of ellipticals display a low S0/E ratio and, vice-versa,
low concentration clusters have a high S0/E. At the same time, the trend of the
morphological fractions and ratios with redshift clearly points to a
morphological evolution: as the redshift decreases, the S0 population tends to
grow at the expense of the spiral population, whereas the frequency of Es
remains almost constant. We also analyze the morphology-density (MD) relation
in our clusters and find that -similarly to higher redshift clusters- a good MD
relation exists in the high-concentration clusters, while it is absent in the
less concentrated clusters. Finally, the comparison of the MD relation in our
clusters with that of the D97 sample suggests that the transformation of
spirals into S0 galaxies becomes more efficient with decreasing local density.Comment: 24 pages including 11 figures and 4 tables, accepted for publication
in Ap
Order and Creep in Flux Lattices and CDWs Pinned by Planar Defects
The influence of randomly distributed point impurities \emph{and} planar
defects on the order and transport in type-II superconductors and related
systems is considered theoretically. For planar defects of identical
orientation the flux line lattice exhibits a new glassy phase dominated by the
planar defects with a finite compressibility, a transverse Meissner effect,
large sample to sample fuctuations of the susceptibility and an exponential
decay of translational long range order. The flux creep resistivity for
currents parallel to the defects is .
Strong disorder enforces an array of dislocations to relax shear strain
- …