422 research outputs found
2D velocity fields of simulated interacting disc galaxies
We investigate distortions in the velocity fields of disc galaxies and their
use to reveal the dynamical state of interacting galaxies at different
redshift. For that purpose, we model disc galaxies in combined
N-body/hydrodynamic simulations. 2D velocity fields of the gas are extracted
from these simulations which we place at different redshifts from z=0 to z=1 to
investigate resolution effects on the properties of the velocity field. To
quantify the structure of the velocity field we also perform a kinemetry
analysis. If the galaxy is undisturbed we find that the rotation curve
extracted from the 2D field agrees well with long-slit rotation curves. This is
not true for interacting systems, as the kinematic axis is not well defined and
does in general not coincide with the photometric axis of the system. For large
(Milky way type) galaxies we find that distortions are still visible at
intermediate redshifts but partly smeared out. Thus a careful analysis of the
velocity field is necessary before using it for a Tully-Fisher study. For small
galaxies (disc scale length ~2 kpc) even strong distortions are not visible in
the velocity field at z~0.5 with currently available angular resolution.
Therefore we conclude that current distant Tully-Fisher studies cannot give
reliable results for low-mass systems. Additionally to these studies we confirm
the power of near-infrared integral field spectrometers in combination with
adaptive optics (such as SINFONI) to study velocity fields of galaxies at high
redshift (z~2).Comment: 12 pages, 18 figures, accepted for publication in A&A, high
resolution version can be found at
http://astro.uibk.ac.at/~thomas/kronberger.pd
The effects of ram-pressure stripping on the internal kinematics of simulated spiral galaxies
We investigate the influence of ram-pressure stripping on the internal gas
kinematics of simulated spiral galaxies. Additional emphasis is put on the
question of how the resulting distortions of the gaseous disc are visible in
the rotation curve and/or the full 2D velocity field of galaxies at different
redshifts. A Milky-Way type disc galaxy is modelled in combined
N-body/hydrodynamic simulations with prescriptions for cooling, star formation,
stellar feedback, and galactic winds. This model galaxy moves through a
constant density and temperature gas, which has parameters similar to the
intra-cluster medium (ICM). Rotation curves (RCs) and 2D velocity fields of the
gas are extracted from these simulations in a way that follows the procedure
applied to observations of distant, small, and faint galaxies as closely as
possible. We find that the appearance of distortions of the gaseous disc due to
ram-pressure stripping depends on the direction of the acting ram pressure. In
the case of face-on ram pressure, the distortions mainly appear in the outer
parts of the galaxy in a very symmetric way. In contrast, in the case of
edge-on ram pressure we find stronger distortions. The 2D velocity field also
shows signatures of the interaction in the inner part of the disc. At angles
smaller than 45 degrees between the ICM wind direction and the disc, the
velocity field asymmetry increases significantly compared to larger angles.
Compared to distortions caused by tidal interactions, the effects of
ram-pressure stripping on the velocity field are relatively low in all cases
and difficult to observe at intermediate redshift in seeing-limited
observations. (abridged)Comment: 9 pages, 11 figures, accepted for publication in A&
Suizidprävention: Vorgehensweisen und Wirksamkeit
According to official statistics every year 11,000 persons in Germany die from suicide. 20 years ago nearly 19,000 suicides were registered. What are the causes for this decrease? Do suicide preventive measures contribute to the reduction of suicide rates? Different universal prevention strategies ( e. g. restriction of access to means) and selective approaches ( programs for special high-risk groups; e. g. patients after attempted suicide) are presented and discussed regarding their preventive value. In most cases it is hardly possible to scientifically prove the efficacy of suicide prevention strategies. Neither the role of psychosocial interventions nor the impact of psychotropic agents can be sufficiently quantified. Due to various methodological reasons ( e. g. small sample sizes and the lack of randomization), interpretation of the data is difficult. In terms of a comprehensive approach of suicide prevention a combination of different activities should be most adequate in the long run
Data and 2D scaling relations for galaxies in Abell 1689: a hint of size evolution at z~0.2
{abridged} We present imaging and spectroscopy of Abell 1689 (z=0.183) from
GEMINI/GMOS-N and HST/ACS. We measure integrated photometry from the GMOS g'
and r' images (for 531 galaxies) and surface photometry from the HST F625W
image (for 43 galaxies) as well as velocities and velocity dispersions from the
GMOS spectra (for 71 galaxies). We construct the Kormendy relation (KR),
Faber-Jackson relation (FJR) and colour-magnitude relation (CMR) for early-type
galaxies in Abell 1689 using this data and compare them to those of the Coma
cluster. We measure the intrinsic scatter of the CMR in Abell 1689 to be 0.054
\pm 0.004 mag which places degenerate constraints on the ratio of the assembly
timescale to the time available (beta) and the age of the population. Making
the assumption that galaxies in Abell 1689 will evolve into those of Coma over
an interval of 2.26 Gyr breaks this degeneracy and limits beta to be > 0.6 and
the age of the red sequence to be > 5.5 Gyr (formed at z > 0.55). Without
corrections for size evolution but accounting for magnitude cuts and selection
effects, the KR & FJR are inconsistent and disagree at the 2 sigma level
regarding the amount of luminosity evolution in the last 2.26 Gyr. However,
after correcting for size evolution the KR & FJR show similar changes in
luminosity (0.22 \pm 0.11 mag) that are consistent with the passive evolution
of the stellar populations from a single burst of star formation 10.2 \pm 3.3
Gyr ago (z = 1.8+inf-0.9). Thus the changes in the KR, FJR & CMR of Abell 1689
relative to Coma all agree and suggest old galaxy populations with little or no
synchronisation in the star formation histories. Furthermore, the weak evidence
for size evolution in the cluster environment in the last 2.26 Gyr places
interesting constraints on the possible mechanisms at work, favouring
harassment or secular processes over merger scenarios.Comment: Accepted for publication in MNRA
The hierarchical build-up of the Tully-Fisher relation
We use the semi-analytic model GalICS to predict the Tully-Fisher relation in
the B, I and for the first time, in the K band, and its evolution with
redshift, up to z~1. We refined the determination of the disk galaxies rotation
velocity, with a dynamical recipe for the rotation curve, rather than a simple
conversion from the total mass to maximum velocity. The new recipe takes into
account the disk shape factor, and the angular momentum transfer occurring
during secular evolution leading to the formation of bulges. This produces
model rotation velocities that are lower by ~20-25% for the majority of the
spirals. We implemented stellar population models with a complete treatment of
the TP-AGB, which leads to a revision of the mass-to-light ratio in the
near-IR. I/K band luminosities increase by ~0.3/0.5 mags at redshift z=0 and by
~0.5/1 mags at z=3. With these two new recipes in place, the comparison between
the predicted Tully-Fisher relation with a series of datasets in the optical
and near-IR, at redshifts between 0 and 1, is used as a diagnostics of the
assembly and evolution of spiral galaxies in the model. At 0.4<z<1.2 the match
between the new model and data is remarkably good, especially for later-type
spirals (Sb/Sc). At z=0 the new model shows a net improvement in comparison
with its original version of 2003, and in accord with recent observations in
the K band, the model Tully-Fisher also shows a morphological differentiation.
However, in all bands the z=0 model Tully-Fisher is too bright. We argue that
this behaviour is caused by inadequate star formation histories in the model
galaxies at low redshifts. The star-formation rate declines too slowly, due to
continuous gas infall that is not efficiently suppressed. An analysis of the
model disk scale lengths, at odds with observations, hints to some missing
physics in the modeling of disk formation inside dark matter halos.Comment: Accepted for publication on MNRAS. 2 new plots, 1 new section, and
extended discussion. 21 pages, 11 figures in tota
Tectonic significance of changes in post-subduction Pliocene-Quaternary magmatism in the south east part of the Carpathian-Pannonian Region
The south-eastern part of the Carpathian–Pannonian region records the cessation of convergence between the European platform/Moesia and the Tisza–Dacia microplate. Plio-Quaternary magmatic activity in this area, in close proximity to the ‘Vrancea zone’, shows a shift from normal calc-alkaline to much more diverse compositions (adakite-like calc-alkaline, K-alkalic, mafic Na-alkalic and ultrapotassic), suggesting a significant change in geodynamic processes at approximately 3 Ma. We review the tectonic setting, timing, petrology and geochemistry of the post-collisional volcanism to constrain the role of orogenic building processes such as subduction or collision on melt production and migration. The calc-alkaline volcanism (5.3–3.9 Ma) marks the end of normal subduction-related magmatism along the post-collisional Călimani–Gurghiu–Harghita volcanic chain in front of the European convergent plate margin. At ca. 3 Ma in South Harghita magma compositions changed to adakite-like calc-alkaline and continued until recent times (< 0.03 Ma) interrupted at 1.6–1.2 Ma by generation of Na and K-alkalic magmas, signifying changes in the source and melting mechanism. We attribute the changes in magma composition in front of the Moesian platform to two main geodynamic events: (1) slab-pull and steepening with opening of a tear window (adakite-like calc-alkaline magmas) and (2) renewed contraction associated with deep mantle processes such as slab steepening during post-collisional times (Na and K-alkalic magmas). Contemporaneous post-collisional volcanism at the eastern edge of the Pannonian Basin at 2.6–1.3 Ma was dominated by Na-alkalic and ultrapotassic magmas, suggesting a close relationship with thermal asthenospheric doming and strain partitioning related to the Adriatic indentation. Similar timing, magma chamber processes and volume for K-alkalic (shoshonitic) magmas in the South Apuseni Mountains (1.6 Ma) and South Harghita area at a distance of ca. 200 km imply a regional connection with the inversion tectonics
Novel multiple sclerosis susceptibility loci implicated in epigenetic regulation
We conducted a genome-wide association study (GWAS) on multiple sclerosis (MS) susceptibility in German cohorts with 4888 cases and 10,395 controls. In addition to associations within the major histocompatibility complex (MHC) region, 15 non-MHC loci reached genome-wide significance. Four of these loci are novel MS susceptibility loci. They map to the genes L3MBTL3, MAZ, ERG, and SHMT1. The lead variant at SHMT1 was replicated in an independent Sardinian cohort. Products of the genes L3MBTL3, MAZ, and ERG play important roles in immune cell regulation. SHMT1 encodes a serine hydroxymethyltransferase catalyzing the transfer of a carbon unit to the folate cycle. This reaction is required for regulation of methylation homeostasis, which is important for establishment and maintenance of epigenetic signatures. Our GWAS approach in a defined population with limited genetic substructure detected associations not found in larger, more heterogeneous cohorts, thus providing new clues regarding MS pathogenesis
Body wall structure in the starfish Asterias rubens
Queen Mary University of London; Engineering & Physical Sciences Research Council. Grant Number: EP/J501360/1; Biotechnology and Biological Sciences Research Council. Grant Number: BBSRC;BB/M001644/1; Royal Society through the Equipment Grant scheme. Grant Number: SEMF1A6
A −436C>A Polymorphism in the Human FAS Gene Promoter Associated with Severe Childhood Malaria
Human genetics and immune responses are considered to critically influence the outcome of malaria infections including life-threatening syndromes caused by Plasmodium falciparum. An important role in immune regulation is assigned to the apoptosis-signaling cell surface receptor CD95 (Fas, APO-1), encoded by the gene FAS. Here, a candidate-gene association study including variant discovery at the FAS gene locus was carried out in a case-control group comprising 1,195 pediatric cases of severe falciparum malaria and 769 unaffected controls from a region highly endemic for malaria in Ghana, West Africa. We found the A allele of c.−436C>A (rs9658676) located in the promoter region of FAS to be significantly associated with protection from severe childhood malaria (odds ratio 0.71, 95% confidence interval 0.58–0.88, pempirical = 0.02) and confirmed this finding in a replication group of 1,412 additional severe malaria cases and 2,659 community controls from the same geographic area. The combined analysis resulted in an odds ratio of 0.71 (95% confidence interval 0.62–0.80, p = 1.8×10−7, n = 6035). The association applied to c.−436AA homozygotes (odds ratio 0.47, 95% confidence interval 0.36–0.60) and to a lesser extent to c.−436AC heterozygotes (odds ratio 0.73, 95% confidence interval 0.63–0.84), and also to all phenotypic subgroups studied, including severe malaria anemia, cerebral malaria, and other malaria complications. Quantitative FACS analyses assessing CD95 surface expression of peripheral blood mononuclear cells of naïve donors showed a significantly higher proportion of CD69+CD95+ cells among persons homozygous for the protective A allele compared to AC heterozygotes and CC homozygotes, indicating a functional role of the associated CD95 variant, possibly in supporting lymphocyte apoptosis
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