282 research outputs found
Theory of continuum percolation III. Low density expansion
We use a previously introduced mapping between the continuum percolation
model and the Potts fluid (a system of interacting s-states spins which are
free to move in the continuum) to derive the low density expansion of the pair
connectedness and the mean cluster size. We prove that given an adequate
identification of functions, the result is equivalent to the density expansion
derived from a completely different point of view by Coniglio et al. [J. Phys A
10, 1123 (1977)] to describe physical clustering in a gas. We then apply our
expansion to a system of hypercubes with a hard core interaction. The
calculated critical density is within approximately 5% of the results of
simulations, and is thus much more precise than previous theoretical results
which were based on integral equations. We suggest that this is because
integral equations smooth out overly the partition function (i.e., they
describe predominantly its analytical part), while our method targets instead
the part which describes the phase transition (i.e., the singular part).Comment: 42 pages, Revtex, includes 5 EncapsulatedPostscript figures,
submitted to Phys Rev
Extremely compact massive galaxies at z~1.4
The optical rest-frame sizes of 10 of the most massive
(~5x10^{11}h_{70}^{-2}M_sun) galaxies found in the near-infrared MUNICS survey
at 1.2<z<1.7 are analysed. Sizes were estimated both in the J and K' filters.
These massive galaxies are at least a factor of 4_{-1.0}^{+1.9} (+-1 sigma)
smaller in the rest-frame V-band than local counterparts of the same stellar
mass. Consequently, the stellar mass density of these objects is (at least) 60
times larger than massive ellipticals today. Although the stellar populations
of these objects are passively fading, their structural properties are rapidly
changing since that redshift. This observational fact disagrees with a scenario
where the more massive and passive galaxies are fully assembled at z~1.4 (i.e.
a monolithic scenario) and points towards a dry merger scenario as the
responsible mechanism for the subsequent evolution of these galaxies.Comment: 5 pages, 2 figures, 1 table, accepted for publication in MNRAS
letter
MOIRCS Deep Survey IV: Evolution of Galaxy Stellar Mass Function Back to z ~ 3
We use very deep near-infrared (NIR) imaging data obtained in MOIRCS Deep
Survey (MODS) to investigate the evolution of the galaxy stellar mass function
back to z~3. The MODS data reach J=24.2, H=23.1, K=23.1 (5sigma, Vega
magnitude) over 103 arcmin^2 (wide) and J=25.1, H=23.7, K=24.1 over 28 arcmin^2
(deep) in the GOODS-North region. The wide and very deep NIR data allow us to
measure the number density of galaxies down to low stellar mass (10^9-10^10
Msun) even at high redshift with high statistical accuracy. The normalization
of the mass function decreases with redshift and the integrated stellar mass
density becomes ~ 8-18% of the local value at z~2 and ~ 4-9% at z~3, which are
consistent with results of previous studies in general fields. Furthermore, we
found that the low-mass slope becomes steeper with redshift from alpha ~- 1.3
at z~1 to alpha ~- 1.6 at z~3, and that the evolution of the number density of
low-mass (10^9-10^10 Msun) galaxies is weaker than that of M* (~10^11 Msun)
galaxies. This indicates that the contribution of low-mass galaxies to the
total stellar mass density has been significant at high redshift. The
steepening of the low-mass slope with redshift is opposite trend expected from
the stellar mass dependence of the specific star formation rate reported in
previous studies. The present result suggests that the hierarchical merging
process overwhelmed the effect of the stellar mass growth by star formation and
was very important for the stellar mass assembly of these galaxies at 1<~z<~3.Comment: 21 pages, 18 figures, accepted for publication in Ap
Mildly suppressed star formation in central regions of MaNGA Seyfert galaxies
Negative feedback from accretion onto super-massive black holes (SMBHs), that
is to remove gas and suppress star formation in galaxies, has been widely
suggested. However, for Seyfert galaxies which harbor less active, moderately
accreting SMBHs in the local universe, the feedback capability of their black
hole activity is elusive. We present spatially-resolved H measurements
to trace ongoing star formation in Seyfert galaxies and compare their specific
star formation rate with a sample of star-forming galaxies whose global galaxy
properties are controlled to be the same as the Seyferts. From the comparison
we find that the star formation rates within central kpc of Seyfert galaxies
are mildly suppressed as compared to the matched normal star forming galaxies.
This suggests that the feedback of moderate SMBH accretion could, to some
extent, regulate the ongoing star formation in these intermediate to late type
galaxies under secular evolution.STFC
ER
Sense of coherence predicts post-myocardial infarction trajectory of leisure time physical activity: a prospective cohort study
<p>Abstract</p> <p>Background</p> <p>Physical activity confers a survival advantage after myocardial infarction (MI), yet the majority of post-MI patients are not regularly active. Since sense of coherence (SOC) has been associated with health outcomes and some health behaviours, we investigated whether it plays a role in post-MI physical activity.</p> <p>We examined the predictive role of SOC in the long-term trajectory of leisure time physical activity (LTPA) after MI using a prospective cohort design.</p> <p>Methods</p> <p>A cohort of 643 patients aged ≤ 65 years admitted to hospital in central Israel with incident MI between February 1992 and February 1993 were followed up for 13 years. Socioeconomic, clinical and psychological factors, including SOC, were assessed at baseline, and LTPA was self-reported on 5 separate occasions during follow-up. The predictive role of SOC in long-term trajectory of LTPA was assessed using generalized estimating equations.</p> <p>Results</p> <p>SOC was consistently associated with engagement in LTPA throughout follow-up. Patients in the lowest SOC tertile had almost twice the odds (odds ratio,1.99; 95% confidence interval,1.52-2.60) of decreasing their engagement in LTPA as those in the highest tertile. A strong association remained after controlling for disease severity, depression, sociodemographic and clinical factors.</p> <p>Conclusion</p> <p>Our evidence suggests that SOC predicts LTPA trajectory post-MI. Assessment of SOC can help identify high-risk MI survivors, who may require additional help in following secondary prevention recommendations which can dramatically improve prognosis.</p
SDSS IV MaNGA: Dependence of Global and Spatially Resolved SFR-M ∗ Relations on Galaxy Properties
Indexación: Scopus.The galaxy integrated Hα star formation rate-stellar mass relation, or SFR(global)-M ∗(global) relation, is crucial for understanding star formation history and evolution of galaxies. However, many studies have dealt with SFR using unresolved measurements, which makes it difficult to separate out the contamination from other ionizing sources, such as active galactic nuclei and evolved stars. Using the integral field spectroscopic observations from SDSS-IV MaNGA, we spatially disentangle the contribution from different Hα powering sources for ∼1000 galaxies. We find that, when including regions dominated by all ionizing sources in galaxies, the spatially resolved relation between Hα surface density (ΣHα(all)) and stellar mass surface density (Σ∗(all)) progressively turns over at the high Σ∗(all) end for increasing M ∗(global) and/or bulge dominance (bulge-to-total light ratio, B/T). This in turn leads to the flattening of the integrated Hα(global)-M ∗(global) relation in the literature. By contrast, there is no noticeable flattening in both integrated Hα(H ii)-M ∗(H ii) and spatially resolved ΣHα(H ii)-Σ∗(H ii) relations when only regions where star formation dominates the ionization are considered. In other words, the flattening can be attributed to the increasing regions powered by non-star-formation sources, which generally have lower ionizing ability than star formation. An analysis of the fractional contribution of non-star-formation sources to total Hα luminosity of a galaxy suggests a decreasing role of star formation as an ionizing source toward high-mass, high-B/T galaxies and bulge regions. This result indicates that the appearance of the galaxy integrated SFR-M ∗ relation critically depends on their global properties (M ∗(global) and B/T) and relative abundances of various ionizing sources within the galaxies.http://iopscience.iop.org/article/10.3847/1538-4357/aaa9bc/met
IMAGES-III: The evolution of the Near-Infrared Tully-Fisher relation over the last 6 Gyr
Using the multi-integral field spectrograph GIRAFFE at VLT, we have derived
the K-band Tully-Fisher relation (TFR) at z~0.6 for a representative sample of
65 galaxies with emission lines. We confirm that the scatter in the z~0.6 TFR
is caused by galaxies with anomalous kinematics, and find a positive and strong
correlation between the complexity of the kinematics and the scatter that they
contribute to the TFR. Considering only relaxed-rotating disks, the scatter,
and possibly also the slope of the TFR, do not appear to evolve with z. We
detect an evolution of the K-band TFR zero point between z~0.6 and z=0, which,
if interpreted as an evolution of the K-band luminosity of rotating disks,
would imply that a brightening of 0.66+/-0.14 mag occurs between z~0.6 and z=0.
Any disagreement with the results of Flores et al. (2006) are attributed to
both an improvement of the local TFR and the more detailed accurate measurement
of the rotation velocities in the distant sample. Most of the uncertainty can
be explained by the relatively coarse spatial-resolution of the kinematical
data. Because most rotating disks at z~0.6 are unlikely to experience further
merging events, one may assume that their rotational velocity does not evolve
dramatically. If true, our result implies that rotating disks observed at z~0.6
are rapidly transforming their gas into stars, to be able to double their
stellar masses and be observed on the TFR at z=0. The rotating disks observed
are indeed emission-line galaxies that are either starbursts or LIRGs, which
implies that they are forming stars at a high rate. Thus, a significant
fraction of the rotating disks are forming the bulk of their stars within 6 to
8 Gyr, in good agreement with former studies of the evolution of the M-Z
relation.Comment: 17 pages, 11 figures, accepted for publication in A&A. v2 taking into
account comments from language edito
Cumulative exposure to air pollution and long term outcomes after first acute myocardial infarction: A population-based cohort study. Objectives and methodology
<p>Abstract</p> <p>Background</p> <p>Cardiovascular disease is a leading cause of morbidity and mortality worldwide and epidemiological studies have consistently shown an increased risk for cardiovascular events in relation to exposure to air pollution. The Israel Study of First Acute Myocardial Infarction was designed to longitudinally assess clinical outcomes, psychosocial adjustment and quality of life in patients hospitalized with myocardial infarction. The current study, by introducing retrospective air pollution data, will examine the association between exposure to air pollution and outcome in myocardial infarction survivors. This report will describe the methods implemented and measures employed. The study specifically aims to examine the relationship between residential exposure to air pollution and long-term risk of recurrent coronary event, heart failure, stroke, cardiac and all-cause death in a geographically defined cohort of patients with myocardial infarction.</p> <p>Methods/Design</p> <p>All 1521 patients aged ≤65 years, admitted with first myocardial infarction between February 1992 and February 1993 to the 8 hospitals serving the population of central Israel, were followed for a median of 13 years. Data were collected on sociodemographic, clinical and environmental factors. Data from air quality monitoring stations will be incorporated retrospectively. Daily measures of air pollution will be summarised, allowing detailed maps to be developed in order to reflect chronic exposure for each participant.</p> <p>Discussion</p> <p>This study addresses some of the gaps in understanding of the prognostic importance of air pollution exposure after myocardial infarction, by allowing a sufficient follow-up period, using a well-defined community cohort, adequately controlling for multiple and multilevel confounding factors and providing extensive data on various outcomes.</p
Galaxy Pairs in COSMOS -- Merger Rate Evolution Since z=1
We present results of a statistical study of the cosmic evolution of the mass
dependent major-merger rate since z=1. A stellar mass limited sample of close
major-merger pairs (the CPAIR sample) was selected from the archive of the
COSMOS survey. Pair fractions at different redshifts derived using the CPAIR
sample and a local K-band selected pair sample show no significant variations
with stellar mass. The pair fraction exhibits moderately strong cosmic
evolution, with the best-fitting evolutionary index m=2.2+-0.2. The
best-fitting function for the merger rate implies that galaxies with stellar
mass between 1E+10 -- 3E+11 M_sun have undergone 0.5 -- 1.5 major-mergers since
z=1. Our results show that, for massive galaxies at z<1, major mergers
involving star forming galaxies (i.e. wet and mixed mergers) can account for
the formation of both ellipticals and red quiescent galaxies (RQGs). On the
other hand, major mergers cannot be responsible for the formation of most low
mass ellipticals and RQGs. Our quantitative estimates indicate that major
mergers have significant impact on the stellar mass assembly of the most
massive galaxies, but for less massive galaxies the stellar mass assembly is
dominated by the star formation. Comparison with the mass dependent (U)LIRG
rates suggests that the frequency of major-merger events is comparable to or
higher than that of (U)LIRGs.Comment: 18 pages, accepted by Ap
The COSMOS-WIRCam near-infrared imaging survey: I: BzK selected passive and star forming galaxy candidates at z>1.4
(abridged) We present a new near-infrared survey covering the 2 deg sq COSMOS
field. Combining our survey with Subaru B and z images we construct a deep,
wide-field optical-infrared catalogue. At Ks<23 (AB magnitudes) our survey
completeness is greater than 90% and 70% for stars and galaxies respectively
and contains 143,466 galaxies and 13,254 stars. At z~2 our catalogues contain
3931 quiescent and 25,757 star-forming BzK-selected galaxies representing the
largest and most secure sample of these objects to date. Our counts of
quiescent galaxies turns over at Ks~22 an effect which we demonstrate cannot be
due to sample incompleteness. In our survey both the number of faint and bright
quiescent objects exceeds the predictions of a semi-analytic galaxy formation
model, indicating potentially the need for further refinements in the amount of
merging and AGN feedback at z~2 in these models. We measure the angular
correlation function for each sample and find that at small scales the
correlation function for passive BzK galaxies exceeds the clustering of dark
matter. We use 30-band photometric redshifts to derive the spatial correlation
length and the redshift distributions for each object class. At Ks<22 we find
r_0^{\gamma/1.8}=7.0 +/-0.5h^{-1} Mpc for the passive BzK candidates and
4.7+/-0.8h^{-1} Mpc for the star-forming BzK galaxies. Our pBzK galaxies have
an average photometric redshift of z_p~1.4, in approximate agreement with the
limited spectroscopic information currently available. The stacked Ks image
will be made publicly available from IRSA.Comment: Accepted for publication in Astrophysical Journal. 17 pages, 17
figures, minor revisions to match published version available at
http://adsabs.harvard.edu/abs/2010ApJ...708..202
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