451 research outputs found
The Star Formation Rate-Density Relation at 0.6<z<0.9 and the Role of Star Forming Galaxies
We study the star formation rates (SFRs) of galaxies as a function of local
galaxy density at 0.6<z<0.9. We used a low-dispersion prism in IMACS on the
6.5-m Baade (Magellan I) telescope to obtain spectra and measured redshifts to
a precision of sigma_z/(1+z)=1% for galaxies with z<23.3 AB mag. We utilized a
stellar mass-limited sample of 977 galaxies above M>1.8x10^{10} Msun to conduct
our main analysis. With three different SFR indicators, (1) Spitzer MIPS
24-micron imaging, (2) SED fitting, and (3) [OII]3727 emission, we find the
median specific SFR (SSFR) and SFR to decline from the low-density field to the
cores of groups and a rich cluster. For the SED and [OII] based SFRs, the
decline in SSFR is roughly an order of magnitude while for the MIPS based SFRs,
the decline is a factor of ~4. We find approximately the same magnitude of
decline in SSFR even after removing the sample of galaxies near the cluster.
Galaxies in groups and a cluster at these redshifts therefore have lower star
formation (SF) activity than galaxies in the field, as is the case at z~0. We
investigated whether the decline in SFR with increasing density is caused by a
change in the proportion of quiescent and star forming galaxies (SFGs) or by a
decline in the SFRs of SFGs. Using the rest-frame U-V and V-J colors to
distinguish quiescent galaxies from SFGs we find the fraction of quiescent
galaxies increases from ~32% to 79% from low to high density. In addition, we
find the SSFRs of SFGs, selected based on U-V and V-J colors, to decline with
increasing density by factors of ~5-6 for the SED and [OII] based SFRs. The
MIPS based SSFRs for SFGs decline with a shallower slope. The order of
magnitude decline in the SSFR-density relation at 0.6<z<0.9 is therefore driven
by both a combination of declining SFRs of SFGs as well as a changing mix of
SFGs and quiescent galaxies [ABRIDGED].Comment: 21 pages, 15 figures, 2 tables, resubmitted to ApJ after addressing
referee comment
The OCareCloudS project: toward organizing care through trusted cloud services
The increasing elderly population and the shift from acute to chronic illness makes it difficult to care for people in hospitals and rest homes. Moreover, elderly people, if given a choice, want to stay at home as long as possible. In this article, the methodologies to develop a cloud-based semantic system, offering valuable information and knowledge-based services, are presented. The information and services are related to the different personal living hemispheres of the patient, namely the daily care-related needs, the social needs and the daily life assistance. Ontologies are used to facilitate the integration, analysis, aggregation and efficient use of all the available data in the cloud. By using an interdisciplinary research approach, where user researchers, (ontology) engineers, researchers and domain stakeholders are at the forefront, a platform can be developed of great added value for the patients that want to grow old in their own home and for their caregivers
A Multiwavelength Study of a Sample of 70 micron Selected Galaxies in the COSMOS Field II: The Role of Mergers in Galaxy Evolution
We analyze the morphological properties of a large sample of 1503 70 micron
selected galaxies in the COSMOS field spanning the redshift range 0.01<z< 3.5
with a median redshift of 0.5 and an infrared luminosity range of
10^8<L_IR<10^14L_sun with a median luminosity of 10^11.4 L_sun. In general
these galaxies are massive, with a stellar mass range of 10^10-10^12 M_sun, and
luminous, with -25<M_K<-20. We find a strong correlation between the fraction
of major mergers and L_IR, with the fraction at the highest luminosity being up
to 50%. We also find that the fraction of spirals drops dramatically with L_IR.
Minor mergers likely play a role in boosting the infrared luminosity for
sources with low luminosities. The precise fraction of mergers in any given
L_IR bin varies by redshift due to sources at z>1 being difficult to classify
and subject to the effects of band pass shifting, therefore, these numbers can
only be considered lower limits. At z<1, where the morphological
classifications are most robust, major mergers clearly dominate the ULIRG
population (50-80%) and are important for the LIRG population (25-40%). At z>1
the fraction of major mergers is at least 30-40% for ULIRGs. Although the
general morphological trends agree with what has been observed for local
(U)LIRGs, the fraction of major mergers is slightly lower than seen locally.
This is in part due to the difficulty of identifying merger signatures at high
redshift. We argue that given the number of major gas-rich mergers observed and
the relatively short timescale that they would be observable in the (U)LIRG
phase that it is plausible for the observed red sequence of massive ellipticals
(<10^12 M_sun) to have been formed entirely by gas-rich major mergers.Comment: 30 pages, 27 figures, and 6 tables. Accepted for publication in ApJ.
The full resolution version can be found at:
http://www.ifa.hawaii.edu/~jeyhan/paperII/Kartaltepe_70mic_PaperII.pd
A Deep Probe of the Galaxy Stellar Mass Functions at z~1-3 with the GOODS NICMOS Survey
We use a sample of 8298 galaxies observed in the HST GOODS NICMOS Survey
(GNS) to construct the galaxy stellar mass function as a function of both
redshift and stellar mass up to z=3.5 and down to masses of Mstar=10^8.5 Msun
at z~1. We discover that a significant fraction of all massive Mstar>10^11 Msun
galaxies are in place up to the highest redshifts we probe, with a decreasing
fraction of lower mass galaxies present at all redshifts. This is an example of
`galaxy mass downsizing', and is the result of massive galaxies forming before
lower mass ones, and not just simply ending their star formation earlier as in
traditional downsizing scenarios. We find that the faint end slope is
significantly steeper than what is found in previous investigations. We
demonstrate that this steeper mass function better matches the stellar mass
added due to star formation, thereby alleviating some of the mismatch between
these two measures of the evolution of galaxy mass. We furthermore examine the
stellar mass function divided into blue/red systems, as well as for star
forming and non-star forming galaxies. We find a similar mass downsizing
present for both blue/red and star-forming/non-star forming galaxies, and that
the low mass galaxies are mostly all blue, and are therefore creating the steep
mass functions. We furthermore show that, although there is a downsizing such
that high mass galaxies are nearer their z=0 values at high redshift, this
turns over at masses Mstar~10^10 Msun, such that the lowest mass galaxies are
more common than galaxies at slight higher masses, creating a `dip' in the
observed galaxy mass function. We argue that the galaxy assembly process may be
driven by different mechanisms at low and high masses, and that the efficiency
of the galaxy formation process is lowest at masses Mstar~10^10 Msun at 1<z<3.
(Abridged)Comment: 16 pages, 11 figures, MNRAS, accepte
Stellar Masses of Lyman Break Galaxies, Lyman Alpha Emitters and Radio Galaxies in Overdense Regions at z=4-6
We present new information on galaxies in the vicinity of luminous radio
galaxies and quasars at z=4,5,6. These fields were previously found to contain
overdensities of Lyman Break Galaxies (LBGs) or spectroscopic Lyman alpha
emitters. We use HST and Spitzer data to infer stellar masses, and contrast our
results with large samples of LBGs in more average environments as probed by
the Great Observatories Origins Deep Survey (GOODS). The following results were
obtained. First, LBGs in both overdense regions and in the field at z=4-5 lie
on a very similar sequence in a z'-[3.6] versus [3.6] color-magnitude diagram.
This is interpreted as a sequence in stellar mass (log[M*/Msun] = 9-11) in
which galaxies become increasingly red due to dust and age as their star
formation rate (SFR) increases. Second, the two radio galaxies are among the
most massive objects (log[M*/Msun]~11) known to exist at z~4-5, and are
extremely rare based on the low number density of such objects as estimated
from the ~25x larger area GOODS survey. We suggest that the presence of these
massive galaxies and supermassive black holes has been boosted through rapid
accretion of gas or merging inside overdense regions. Third, the total stellar
mass found in the z=4 ``proto-cluster'' TN1338 accounts for <30% of the stellar
mass on the cluster red sequence expected to have formed at z>4, based on a
comparison with the massive X-ray cluster Cl1252 at z=1.2. Although future
near-infrared observations should determine whether any massive galaxies are
currently being missed, one possible explanation for this mass difference is
that TN1338 evolves into a smaller cluster than Cl1252. This raises the
interesting question of whether the most massive protocluster regions at z>4
remain yet to be discovered.Comment: The Astrophysical Journal, In Press (17 pages, 7 figures
NOBAI: a web server for character coding of geometrical and statistical features in RNA structure
The Numeration of Objects in Biology: Alignment Inferences (NOBAI) web server provides a web interface to the applications in the NOBAI software package. This software codes topological and thermodynamic information related to the secondary structure of RNA molecules as multi-state phylogenetic characters, builds character matrices directly in NEXUS format and provides sequence randomization options. The web server is an effective tool that facilitates the search for evolutionary history embedded in the structure of functional RNA molecules. The NOBAI web server is accessible at ‘http://www.manet.uiuc.edu/nobai/nobai.php’. This web site is free and open to all users and there is no login requirement
Cosmological Implications of a Stellar Initial Mass Function that Varies with the Jeans Mass in Galaxies
Observations of star-forming galaxies at high-z have suggested discrepancies
in the inferred star formation rates (SFRs) either between data and models, or
between complementary measures of the SFR. These putative discrepancies could
all be alleviated if the stellar IMF is systematically weighted toward more
high-mass star formation in rapidly star-forming galaxies. Here, we explore how
the IMF might vary under the central assumption that the turnover mass in the
IMF, Mc, scales with the Jeans mass in giant molecular clouds (GMCs), M_J. We
employ hydrodynamic and radiative transfer simulations of galaxies to predict
how the typical GMC Jeans mass, and hence the IMF, varies with galaxy property.
We then study the impact of such an IMF on the star formation law, the SFR-M*
relation, submillimetre galaxies (SMGs), and the cosmic SFR density. Our main
results are: The H2 mass-weighted Jeans mass in a galaxy scales with the SFR
when the SFR is greater a few M_sun/yr. SPS modeling shows that this results in
a nonlinear relation between SFR and Lbol, such that SFR Lbol^0.88. Using this
model relation, the inferred SFR of local ULIRGs decreases by ~2, and that of
high-z SMGs decreases by ~3-5. At z 2, this results in a lowered normalisation
of the SFR-M* relation in better agreement with models, a reduced discrepancy
between the observed cosmic SFR density and stellar mass density evolution, and
SMG SFRs that are easier to accommodate in current hierarchical structure
formation models. It further results in a Schmidt relation with slope of ~1.6
when utilising a physically motivated form for the CO-H2 conversion factor.
While each of the discrepancies considered here could be alleviated without
appealing to a varying IMF, the modest variation implied by assuming Mc M_J is
a plausible solution that simultaneously addresses numerous thorny issues
regarding the SFRs of high-z galaxies.Comment: MNRAS Accepted; 16 page
Magnetotransport in the Normal State of La1.85Sr0.15Cu(1-y)Zn(y)O4 Films
We have studied the magnetotransport properties in the normal state for a
series of La1.85Sr0.15Cu(1-y)Zn(y)O4 films with values of y, between 0 and
0.12. A variable degree of compressive or tensile strain results from the
lattice mismatch between the substrate and the film, and affects the transport
properties differently from the influence of the zinc impurities. In
particular, the orbital magnetoresistance (OMR) varies with y but is
strain-independent. The relations for the resistivity and the Hall angle and
the proportionality between the OMR and tan^2 theta are followed about 70 K. We
have been able to separate the strain and impurity effects by rewriting the
above relations, where each term is strain-independent and depends on y only.
We also find that changes in the lattice constants give rise to closely the
same fractional changes in other terms of the equation.The OMR is more strongly
supressed by the addition of impurities than tan^2 theta. We conclude that the
relaxation ratethat governs Hall effect is not the same as for the
magnetoresistance. We also suggest a correspondence between the transport
properties and the opening of the pseudogap at a temperature which changes when
the La-sr ratio changes, but does not change with the addition of the zinc
impurities
Systemic aminoglycosides-induced vestibulotoxicity in humans
Objectives: This systematic review aimed to investigate the prevalence and characteristics of vestibular adverse effects of aminoglycoside (AG) therapy in humans and to analyze objective vestibular tests for the detection of AG-induced vestibulotoxicity.
Design: PubMed, Cochrane Database, Web of Science, and reference lists of all included studies were screened by two independent researchers. The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines were followed. Studies were included according to preset inclusion criteria and reported outcomes of studies evaluating vestibular function using one or more objective vestibular function tests in adults and children after systemic AG administration. The methodological quality of each study was assessed using the quality assessment tool for quantitative studies. Interrater reliability was established using Cohen's Kappa.
Results: Twenty-seven studies were included, with the vast majority showing AG-induced vestibulotoxic side effects, ranging from 0 to 60%. Most studies reported AG-induced abnormalities by caloric and rotatory testing, whereas only a few studies reported using video Head Impulse test and vestibular evoked myogenic potential testing.
Conclusions: Because type I hair cells (particularly of the semicircular canals) are more susceptible to ototoxicity, video Head Impulse test and vestibular evoked myogenic potential testing seem more promising for the early detection of vestibulotoxicity than caloric and rotatory testing. Prospective studies using an extensive vestibular test battery are needed to further characterize the impact of AGs on the different vestibular end organs and to identify the most sensitive vestibular technique for the early detection of vestibulotoxicity
Singular Fermi Liquids
An introductory survey of the theoretical ideas and calculations and the
experimental results which depart from Landau Fermi-liquids is presented.
Common themes and possible routes to the singularities leading to the breakdown
of Landau Fermi liquids are categorized following an elementary discussion of
the theory. Soluble examples of Singular Fermi liquids (often called Non-Fermi
liquids) include models of impurities in metals with special symmetries and
one-dimensional interacting fermions. A review of these is followed by a
discussion of Singular Fermi liquids in a wide variety of experimental
situations and theoretical models. These include the effects of low-energy
collective fluctuations, gauge fields due either to symmetries in the
hamiltonian or possible dynamically generated symmetries, fluctuations around
quantum critical points, the normal state of high temperature superconductors
and the two-dimensional metallic state. For the last three systems, the
principal experimental results are summarized and the outstanding theoretical
issues highlighted.Comment: 170 pages; submitted to Physics Reports; a single pdf file with high
quality figures is available from http://www.lorentz.leidenuniv.nl/~saarloo
- …