92 research outputs found
Optical coherence tomography and C-reactive protein in risk stratification of acute coronary syndromes
Is gluten the only culprit for non-celiac gluten/wheat sensitivity?
The gluten-free diet (GFD) has gained increasing popularity in recent years, supported by marketing campaigns, media messages and social networks. Nevertheless, real knowledge of gluten and GF-related implications for health is still poor among the general population. The GFD has also been suggested for non-celiac gluten/wheat sensitivity (NCG/WS), a clinical entity characterized by intestinal and extraintestinal symptoms induced by gluten ingestion in the absence of celiac disease (CD) or wheat allergy (WA). NCG/WS should be regarded as an “umbrella term” including a variety of different conditions where gluten is likely not the only factor responsible for triggering symptoms. Other compounds aside from gluten may be involved in the pathogenesis of NCG/WS. These include fructans, which are part of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs), amylase trypsin inhibitors (ATIs), wheat germ agglutinin (WGA) and glyphosate. The GFD might be an appropriate dietary approach for patients with self-reported gluten/wheat-dependent symptoms. A low-FODMAP diet (LFD) should be the first dietary option for patients referring symptoms more related to FODMAPs than gluten/wheat and the second-line treatment for those with self-reported gluten/wheat-related symptoms not responding to the GFD. A personalized approach, regular follow-up and the help of a skilled dietician are mandatory
The Origin of Color Gradients in Early-Type Systems and Their Compactness at High-z
In this Letter, we present mean optical+NIR color gradient estimates for 5080
early-type galaxies (ETGs) in the grizYJHK wavebands of the Sloan Digital Sky
Survey (SDSS) plus UKIRT Infrared Deep Sky Survey (UKIDSS). The color gradient
is estimated as the logarithmic slope of the radial color profile in ETGs. With
such a large sample size, we study the variation of the mean color gradient as
a function of waveband with unprecedented accuracy. We find that (i) color
gradients are mainly due, on average, to a metallicity variation of about
-0.4dex per decade in galaxy radius; and (ii) a small, but significant,
positive age gradient is present, on average, in ETGs, with the inner stellar
population being slightly younger, by ~0.1dex per radial decade, than the outer
one. Also, we show that the presence of a positive mean age gradient in ETGs,
as found in the present study, implies their effective radius to be smaller at
high z, consistent with observations.Comment: 4 pages, 2 color figures, accepted for publication in the
Astrophysical Journal Letter
Early-type Galaxies at z ~ 1.3. II. Masses and Ages of Early-type Galaxies in Different Environments and Their Dependence on Stellar Population Model Assumptions
We have derived masses and ages for 79 early-type galaxies (ETGs) in different environments at z ~ 1.3 in the Lynx supercluster and in the GOODS/CDF-S field using multi-wavelength (0.6-4.5 μm; KPNO, Palomar, Keck, Hubble Space Telescope, Spitzer) data sets. At this redshift the contribution of the thermally pulsing asymptotic giant branch (TP-AGB) phase is important for ETGs, and the mass and age estimates depend on the choice of the stellar population model used in the spectral energy distribution fits. We describe in detail the differences among model predictions for a large range of galaxy ages, showing the dependence of these differences on age. Current models still yield large uncertainties. While recent models from Maraston and Charlot & Bruzual offer better modeling of the TP-AGB phase with respect to less recent Bruzual & Charlot models, their predictions do not often match. The modeling of this TP-AGB phase has a significant impact on the derived parameters for galaxies observed at high redshift. Some of our results do not depend on the choice of the model: for all models, the most massive galaxies are the oldest ones, independent of the environment. When using the Maraston and Charlot & Bruzual models, the mass distribution is similar in the clusters and in the groups, whereas in our field sample there is a deficit of massive (M ≳ 10^(11) M_☉) ETGs. According to those last models, ETGs belonging to the cluster environment host on average older stars with respect to group and field populations. This difference is less significant than the age difference in galaxies of different masses
Evidence for the Universality of Properties of Red-sequence Galaxies in X-Ray- and Red-Sequence-Selected Clusters at z ~ 1
We study the slope, intercept, and scatter of the color–magnitude and color–mass relations for a sample of 10 infrared red-sequence-selected clusters at z ~ 1. The quiescent galaxies in these clusters formed the bulk of their stars above z ≳ 3 with an age spread Δt ≳ 1 Gyr. We compare UVJ color–color and spectroscopic-based galaxy selection techniques, and find a 15% difference in the galaxy populations classified as quiescent by these methods. We compare the color–magnitude relations from our red-sequence selected sample with X-ray- and photometric-redshift-selected cluster samples of similar mass and redshift. Within uncertainties, we are unable to detect any difference in the ages and star formation histories of quiescent cluster members in clusters selected by different methods, suggesting that the dominant quenching mechanism is insensitive to cluster baryon partitioning at z ~ 1
Early-type Galaxies at z ~ 1.3. III. On the Dependence of Formation Epochs and Star Formation Histories on Stellar Mass and Environment
We study the environmental dependence of stellar population properties at z ~ 1.3. We derive galaxy properties (stellar masses, ages, and star formation histories) for samples of massive, red, passive early-type galaxies (ETGs) in two high-redshift clusters, RXJ0849+4452 and RXJ0848+4453 (with redshifts of z = 1.26 and 1.27, respectively), and compare them with those measured for the RDCS1252.9–2927 cluster at z = 1.24 and with those measured for a similarly mass-selected sample of field contemporaries drawn from the GOODS-South field. Robust estimates of the aforementioned parameters have been obtained by comparing a large grid of composite stellar population models with extensive 8- to 10-band photometric coverage, from the rest-frame far-ultraviolet to the infrared. We find no variations of the overall stellar population properties among the different samples of cluster ETGs. However, when comparing cluster versus field stellar population properties we find that, even if the ages are similar and depend only on galaxy mass, the ones in the field do employ longer timescales to assemble their final mass. We find that, approximately 1 Gyr after the onset of star formation, the majority (75%) of cluster galaxies have already assembled most (>80%) of their final mass, while, by the same time, fewer (35%) field ETGs have. Thus, we conclude that while galaxy mass regulates the timing of galaxy formation, the environment regulates the timescale of their star formation histories
The importance of major mergers in the build up of stellar mass in brightest cluster galaxies at z=1
Recent independent results from numerical simulations and observations have
shown that brightest cluster galaxies (BCGs) have increased their stellar mass
by a factor of almost two between z~0.9 and z~0.2. The numerical simulations
further suggest that more than half this mass is accreted through major
mergers. Using a sample of 18 distant galaxy clusters with over 600
spectroscopically confirmed cluster members between them, we search for
observational evidence that major mergers do play a significant role. We find a
major merger rate of 0.38 +/- 0.14 mergers per Gyr at z~1. While the
uncertainties, which stem from the small size of our sample, are relatively
large, our rate is consistent with the results that are derived from numerical
simulations. If we assume that this rate continues to the present day and that
half of the mass of the companion is accreted onto the BCG during these
mergers, then we find that this rate can explain the growth in the stellar mass
of the BCGs that is observed and predicted by simulations. Major mergers
therefore appear to be playing an important role, perhaps even the dominant
one, in the build up of stellar mass in these extraordinary galaxies.Comment: 15 pages, 6 figures, accepted for publication in MNRAS. Reduced data
will be made available through the ESO archiv
VLT and ACS observations of RDCS J1252.9-2927: dynamical structure and galaxy populations in a massive cluster at z=1.237
We present results from an extensive spectroscopic survey, carried out with
VLT FORS, and from an extensive multiwavelength imaging data set from the HST
Advanced Camera for Surveys and ground based facilities, of the cluster of
galaxies RDCS J1252.9-2927. We have spectroscopically confirmed 38 cluster
members in the redshift range 1.22 < z < 1.25. A cluster median redshift of
z=1.237 and a rest-frame velocity dispersion of 747^{+74}_{-84} km/s are
obtained. Using the 38 confirmed redshifts, we were able to resolve, for the
first time at z > 1, kinematic structure. The velocity distribution, which is
not Gaussian at the 95% confidence level, is consistent with two groups that
are also responsible for the projected east-west elongation of the cluster. The
groups are composed of 26 and 12 galaxies with velocity dispersions of
486^{+47}_{-85} km/s and 426^{+57}_{-105} km/s, respectively. The elongation is
also seen in the intracluster gas and the dark matter distribution. This leads
us to conclude that RDCS J1252.9-2927 has not yet reached a final virial state.
We extend the analysis of the color-magnitude diagram of spectroscopic members
to more than 1 Mpc from the cluster center. The scatter and slope of
non-[OII]-emitting cluster members in the near-IR red sequence is similar to
that seen in clusters at lower redshift. Furthermore, most of the galaxies with
luminosities greater than ~ K_s*+1.5 do not show any [OII], indicating that
these more luminous, redder galaxies have stopped forming stars earlier than
the fainter, bluer galaxies. Our observations provide detailed dynamical and
spectrophotometric information on galaxies in this exceptional high-redshift
cluster, delivering an in-depth view of structure formation at this epoch only
5 Gyr after the Big Bang.Comment: 29 pages. 16 figures. ApJ accepted. Tables 2,3 and 5, figure 1 and
the full figure 5 will be available in the paper and electronic editions from
ApJ. v2: minor corrections to the abstract and text to match the Journal's
versio
Absence of Evidence Is Not Evidence of Absence: The Color-Density Relation at Fixed Stellar Mass Persists to z ~ 1
We use data drawn from the DEEP2 Galaxy Redshift Survey to investigate the
relationship between local galaxy density, stellar mass, and rest-frame galaxy
color. At z ~ 0.9, we find that the shape of the stellar mass function at the
high-mass (log (M*/Msun) > 10.1) end depends on the local environment, with
high-density regions favoring more massive systems. Accounting for this stellar
mass-environment relation (i.e., working at fixed stellar mass), we find a
significant color-density relation for galaxies with 10.6 < log(M*/Msun) < 11.1
and 0.75 < z < 0.95. This result is shown to be robust to variations in the
sample selection and to extend to even lower masses (down to log(M*/Msun) ~
10.4). We conclude by discussing our results in comparison to recent works in
the literature, which report no significant correlation between galaxy
properties and environment at fixed stellar mass for the same redshift and
stellar mass domain. The non-detection of environmental dependence found in
other data sets is largely attributable to their smaller samples size and lower
sampling density, as well as systematic effects such as inaccurate redshifts
and biased analysis techniques. Ultimately, our results based on DEEP2 data
illustrate that the evolutionary state of a galaxy at z ~ 1 is not exclusively
determined by the stellar mass of the galaxy. Instead, we show that local
environment appears to play a distinct role in the transformation of galaxy
properties at z > 1.Comment: 10 pages, 5 Figures; Accepted for publication in MNRA
High-redshift elliptical galaxies: are they (all) really compact?
We investigate the properties of 12 ultra-massive passively evolving early
type galaxies (ETGs) at z_phot>1.4 in the COSMOS 2 deg^2 field. These 12 ETGs
were selected as pBzKs, have accurate 1.4<= z_phot <=1.7,high Sersic index
profiles typical of ellipticals, no detection at 24 micron, resulting in a
complete ETG sample at M*>2.5x10^11 M_sun (Chabrier IMF). Contrary to previous
claims, the half light radii estimated in very high S/N imaging data from
HST+ACS are found to be large for most of the sample, consistent with local
ellipticals. If the high redshift ETGs with M*<2.5x10^11 M_sun are really small
in size and compact as reported in previous studies, our result may suggest a
"downsizing" scenario, whereby the most massive ETGs reach their final
structure earlier and faster than lower mass ones. However, simulating galaxies
with morphological properties fixed to those of local ETGs with the same
stellar mass show that the few compact galaxies that we still recover in our
sample can be understood in term of fluctuations due to noise preventing the
recovery of the extended low surface brightness halos in the light profile.
Such halos, typical of Sersic profiles, extending even up to 40 kpc, are indeed
seen in our sample.Comment: 9 pages, 7 figures, accepted by MNRA
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