978 research outputs found
Supermassive Black Hole Mass Functions at Intermediate Redshifts from Spheroid and AGN Luminosity Functions
Redshift evolution of supermassive black hole mass functions (BHMFs) is
investigated up to z ~ 1. BHMFs at intermediate redshifts are calculated in two
ways. One way is from early-type galaxy luminosity functions (LFs); we assume
an M_BH - L_sph correlation at a redshift by considering a passive evolution of
L_sph in the local relationship. The resultant BHMFs (spheroid-BHMFs) from LFs
of red sequence galaxies indicates a slight decrease of number density with
increasing redshift at M_BH > 10^{7.5-8} M_solar. Since a redshift evolution in
slope and zeropoint of the M_BH - L_sph relation is unlikely to be capable of
making such an evolution in BHMF, the evolution of the spheroid-BHMFs is
perhaps due mainly to the decreasing normalization in the galaxy LFs. We also
investigate how spheroid-BHMFs are affected by uncertainties existing in the
derivation in detail. The other way of deriving a BHMF is based on the
continuity equation for number density of SMBHs and LFs of active galactic
nucleus (AGN). The resultant BHMFs (AGN-BHMFs) show no clear evolution out to z
= 1 at M_BH > 10^8 M_solar, but exhibit a significant decrease with redshift in
the lower mass range. Comparison of the spheroid-BHMFs with the AGN-BHMFs
suggests that at M_BH > 10^{8} M_solar, the spheroid-BHMFs are broadly
consistent with the AGN-BHMFs out to z ~ 1. The agreement between the
spheroid-BHMFs and the AGN-BHMFs appears to support that most of the SMBHs are
already hosted by massive spheroids at z ~ 1 and they evolve without
significant mass growth since then.Comment: 13 pages, accepted for publication in MNRA
Lack of Association of Type 2 Diabetes Susceptibility Genotypes and Body Weight on the Development of Islet Autoimmunity and Type 1 Diabetes
AIM: To investigate whether type 2 diabetes susceptibility genes and body weight influence the development of islet autoantibodies and the rate of progression to type 1 diabetes. METHODS: Genotyping for single nucleotide polymorphisms (SNP) of the type 2 diabetes susceptibility genes CDKAL1, CDKN2A/2B, FTO, HHEX-IDE, HMGA2, IGF2BP2, KCNJ11, KCNQ1, MTNR1B, PPARG, SLC30A8 and TCF7L2 was obtained in 1350 children from parents with type 1 diabetes participating in the BABYDIAB study. Children were prospectively followed from birth for islet autoantibodies and type 1 diabetes. Data on weight and height were obtained at 9 months, 2, 5, 8, 11, and 14 years of age. RESULTS: None of type 2 diabetes risk alleles at the CDKAL1, CDKN2A/2B, FTO, HHEX-IDE, HMGA2, IGF2BP2, KCNJ11, KCNQ1, MTNR1B, PPARG and SLC30A8 loci were associated with the development of islet autoantibodies or diabetes. The type 2 diabetes susceptible genotype of TCF7L2 was associated with a lower risk of islet autoantibodies (7% vs. 12% by age of 10 years, P = 0.015, P(corrected) = 0.18). Overweight children at seroconversion did not progress to diabetes faster than non-overweight children (HR: 1.08; 95% CI: 0.48-2.45, P>0.05). CONCLUSIONS: These findings do not support an association of type 2 diabetes risk factors with islet autoimmunity or acceleration of diabetes in children with a family history of type 1 diabetes
Compulsivity and impulsivity traits linked to attenuated developmental frontstriatal myelination trajectories
A transition from adolescence into adulthood corresponds to a period where rapid brain development coincides with an enhanced incidence of psychiatric disorder. The precise developmental brain changes that account for this emergent psychiatric symptomatology remain obscure. Capitalising on a unique longitudinal dataset, that includes in-vivo myelin-sensitive magnetization transfer (MT) MRI, we show that coming of age is characterised by brain-wide growth in MT, within both gray matter and adjacent juxta-cortical white matter. In this healthy population the expression of common developmental traits, namely compulsivity and impulsivity, are tied to a reduced unfolding of these MT trajectories in fronto-striatal regions. This reduction is most marked in dorsomedial and dorsolateral frontal structures for compulsivity, and in lateral and medial frontal areas for impulsivity. The findings highlight a brain developmental linkage for compulsivity and impulsivity is evident in regionally specific reduced unfolding of MT-related myelination.Wellcome Trus
The evolution of the luminosity functions in the FORS Deep Field from low to high redshift: I. The blue bands
We use the very deep and homogeneous I-band selected dataset of the FORS Deep
Field (FDF) to trace the evolution of the luminosity function over the redshift
range 0.5 < z < 5.0. We show that the FDF I-band selection down to I(AB)=26.8
misses of the order of 10 % of the galaxies that would be detected in a K-band
selected survey with magnitude limit K(AB)=26.3 (like FIRES). Photometric
redshifts for 5558 galaxies are estimated based on the photometry in 9 filters
(U, B, Gunn g, R, I, SDSS z, J, K and a special filter centered at 834 nm). A
comparison with 362 spectroscopic redshifts shows that the achieved accuracy of
the photometric redshifts is (Delta z / (z_spec+1)) < 0.03 with only ~ 1 %
outliers. This allows us to derive luminosity functions with a reliability
similar to spectroscopic surveys. In addition, the luminosity functions can be
traced to objects of lower luminosity which generally are not accessible to
spectroscopy. We investigate the evolution of the luminosity functions
evaluated in the restframe UV (1500 Angstroem and 2800 Angstroem), u', B, and
g' bands. Comparison with results from the literature shows the reliability of
the derived luminosity functions. Out to redshifts of z ~ 2.5 the data are
consistent with a slope of the luminosity function approximately constant with
redshift, at a value of -1.07 +- 0.04 in the UV (1500 Angstroem, 2800
Angstroem) as well as u', and -1.25 +- 0.03 in the blue (g', B). We do not see
evidence for a very steep slope (alpha < -1.6) in the UV at z ~ 3.0 and z ~ 4.0
favoured by other authors. There may be a tendency for the faint-end slope to
become shallower with increasing redshift but the effect is marginal. We find a
brightening of M_star and a decrease of Phi_star with redshift for all analyzed
wavelengths. [abridged]Comment: 30 pages, re-submitted to A&A after referee comments have been taken
into account, full-resolution version available at
http://www.usm.uni-muenchen.de/people/gabasch/publications/gabasch_lfblue.p
Formation and Evolution of Early-Type Galaxies: Spectro-Photometry from Cosmo-Chemo-Dynamical Simulations
One of the major challenges in modern astrophysics is to understand the
origin and the evolution of galaxies, the bright, massive early type galaxies
(ETGs) in particular. Therefore, these galaxies are likely to be good probes of
galaxy evolution, star formation and, metal enrichment in the early Universe.
In this context it is very important to set up a diagnostic tool able to
combine results from chemo-dynamical N-Body-TSPH (NB-TSPH) simulations of ETGs
with those of spectro-photometric population synthesis and evolution so that
all key properties of galaxies can be investigated. The main goal of this paper
is to provide a preliminary validation of the software package before applying
it to the analysis of observational data. The galaxy models in use where
calculated by the Padova group in two different cosmological scenarios: the
SCDM, and the Lambda CDM. For these models, we recover their
spectro-photometric evolution through the entire history of the Universe. We
computed magnitudes and colors and their evolution with the redshift along with
the evolutionary and cosmological corrections for the model galaxies at our
disposal, and compared them with data for ETGs taken from the COSMOS and the
GOODS databases. Starting from the dynamical simulations and photometric models
at our disposal, we created synthetic images from which we derived the
structural and morphological parameters. The theoretical results are compared
with observational data of ETGs selected form the SDSS database. The simulated
colors for the different cosmological scenarios follow the general trend shown
by galaxies of the COSMOS and GOODS. Within the redshift range considered, all
the simulated colors reproduce the observational data quite well.Comment: 28 pages, 28 figures, accepted for pubblication by A&
The DEEP Groth Strip Survey IX: Evolution of the Fundamental Plane of Field Galaxies
Fundamental Plane studies provide an excellent means of understanding the
evolutionary history of early-type galaxies. Using the Low Resolution Imaging
Spectrograph on the Keck telescope, we obtained internal stellar kinematic
information for 36 field galaxies in the Groth Strip--21 early-type and 15 disk
galaxies. Their redshifts range from 0.3--1.0, with a median redshift 0.8. The
slope of the relation shows no difference compared with the local slope.
However, there is significant evolution in the zero-point offset; an offset due
to evolution in magnitude requires a 2.4 magnitude luminosity brightening at
z=1. We see little differences of the offset with bulge fraction, which is a
good surrogate for galaxy type. Correcting for the luminosity evolution reduces
the orthogonal scatter in the Fundamental Plane to 8%, consistent with the
local scatter. This scatter is measured for our sample, and does not include
results from other studies which may have different selection effects. The
difference in the degree of evolution between our field sample and published
cluster galaxies suggests a more recent formation epoch--around z=1.5 for field
galaxies compared to z>2.0 for cluster galaxies. The magnitude difference
implies that the field early-type galaxies are about 2 Gyr younger than the
cluster ellipticals using standard single-burst models. However, the same
models imply a significant change in the rest-frame U-B color from then to
present, which is not seen in our sample. Continuous low-level star formation,
however, would serve to explain the constant colors over this large magnitude
change. A consistent model has 7% of the stellar mass created after the initial
burst, using an exponentially decaying star formation rate with an e-folding
time of 5 Gyr.Comment: 25 pages, accepted for publication in the Astrophysical Journal, high
resolution version at http://hoku.as.utexas.edu/~gebhardt/FPpaper.p
Structure of visible and dark matter components in spiral galaxies at redshifts z = 0.5-0.9
We have constructed self-consistent light and mass distribution models for
four disk galaxies at redshifts z = 0.48, 0.58, 0.81 and 0.88, using the HST
archive WFPC2 observations and rotation curves measured by Vogt et al. (1996)
and Rigopoulou et al. (2002). The models consist of three components: a bulge,
a disk and a dark matter halo. Similarly to the sample studied in Paper I (Tamm
& Tenjes, 2003), light distribution of the galaxies in the outer parts is
clearly steeper than a simple exponential disk. After applying k-corrections,
calculated mass-to-light ratios for galactic disks within the maximum disk
assumption are M/L_B = 0.9, 7.4, 4.3 and 1.4, respectively. Together with the
galaxies from Paper I, the mean = 2.5 at ~0.9, indicating no
significant evolution of M/L_B with redshift. Central densities of dark matter
halos for an isothermal model are 0.008, 0.035, 0.013, and 0.022 in units
M_sun/pc^3, respectively. Together with the galaxies from Paper I, the DM
central density of the four galaxies at mean readshift ~0.9 is rho(0) =
(0.012-0.028) M_sun/pc^3, also showing no significant evolution with redshift.Comment: 11 pages, 10 figures, Astron. Astrophys. accepte
Evidence for an excess of B -> D(*) Tau Nu decays
Based on the full BaBar data sample, we report improved measurements of the
ratios R(D(*)) = B(B -> D(*) Tau Nu)/B(B -> D(*) l Nu), where l is either e or
mu. These ratios are sensitive to new physics contributions in the form of a
charged Higgs boson. We measure R(D) = 0.440 +- 0.058 +- 0.042 and R(D*) =
0.332 +- 0.024 +- 0.018, which exceed the Standard Model expectations by 2.0
sigma and 2.7 sigma, respectively. Taken together, our results disagree with
these expectations at the 3.4 sigma level. This excess cannot be explained by a
charged Higgs boson in the type II two-Higgs-doublet model. We also report the
observation of the decay B -> D Tau Nu, with a significance of 6.8 sigma.Comment: Expanded section on systematics, text corrections, improved the
format of Figure 2 and included the effect of the change of the Tau
polarization due to the charged Higg
A search for the decay modes B+/- to h+/- tau l
We present a search for the lepton flavor violating decay modes B+/- to h+/-
tau l (h= K,pi; l= e,mu) using the BaBar data sample, which corresponds to 472
million BBbar pairs. The search uses events where one B meson is fully
reconstructed in one of several hadronic final states. Using the momenta of the
reconstructed B, h, and l candidates, we are able to fully determine the tau
four-momentum. The resulting tau candidate mass is our main discriminant
against combinatorial background. We see no evidence for B+/- to h+/- tau l
decays and set a 90% confidence level upper limit on each branching fraction at
the level of a few times 10^-5.Comment: 15 pages, 7 figures, submitted to Phys. Rev.
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