138 research outputs found
The VIRMOS deep imaging survey: III. ESO/WFI deep U-band imaging of the 0226-04 deep field
In this paper we describe the U-band imaging of the F02 deep field, one of
the fields in the VIRMOS Deep Imaging Survey. The observations were done at the
ESO/MPG 2.2m telescope at La Silla (Chile) using the 8k x 8k Wide-Field Imager
(WFI). The field is centered at alpha(J2000)=02h 26m 00s and
delta(J2000)=-04deg 30' 00", the total covered area is 0.9 deg**2 and the
limiting magnitude (50% completeness) is U(AB) ~ 25.4 mag. Reduction steps,
including astrometry, photometry and catalogue extraction, are first discussed.
The achieved astrometric accuracy (RMS) is ~ 0.2" with reference to the I-band
catalog and ~ 0.07" internally (estimated from overlapping sources in different
exposures). The photometric accuracy including uncertainties from photometric
calibration, is < 0.1 mag. Various tests are then performed as a quality
assessment of the data. They include: (i) the color distribution of stars and
galaxies in the field, done together with the BVRI data available from the
VIMOS survey; (ii) the comparison with previous published results of U-band
magnitude-number counts of galaxies.Comment: 10 pages, 13 figures, accepted for publication on Astronomy and
Astrophysic
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
The Evolution of Field Early-Type Galaxies in the FDF and WHDF
We explore the properties of 24 field early-type galaxies at 0.20<z<0.75 down
to M_B<=-19.30 in a sample extracted from the FORS Deep Field and the William
Herschel Deep Field. High S/N intermediate-resolution VLT spectroscopy was
complemented by deep high-resolution HST/ACS imaging and additional
ground-based multi-band photometry. To clarify the low level of star formation
(SF) detected in some galaxies, we identify the amount of AGN activity in our
sample using archive data of Chandra and XMM-Newton X-ray surveys. The B and
K-band Faber-Jackson relations and the Fundamental Plane display a moderate
evolution for the field early-type galaxies. Lenticular (S0) galaxies feature
on average a stronger luminosity evolution and bluer rest-frame colours which
can be explained that they comprise more diverse stellar populations compared
to elliptical galaxies. The evolution of the FP can be interpreted as an
average change in the dynamical mass-to-light ratio of our galaxies as <\Delta
\log{(M/L_B)}/z>=-0.74\pm0.08. The M/L evolution of these field galaxies
suggests a continuous mass assembly of field early-type galaxies during the
last 5 Gyr, that gets support by recent studies of field galaxies up to z~1.
Independent evidence for recent SF activity is provided by spectroscopic (OII
em., Hdelta) and photometric (rest-frame colors) diagnostics. Based on the
Hdelta absorption feature we detect a weak residual SF for galaxies that
accounts for 5%-10% in the total stellar mass of these galaxies. The
co-evolution in the luminosity and mass of our galaxies favours a downsizing
formation process. We find some evidence that our galaxies experienced a period
of SF quenching, possible triggered by AGN activity that is in good agreement
with recent results on both observational and theoretical side. (abridged)Comment: 26 pages, 23 figures, accepted for publication in MNRA
Lyman alpha emission in high-redshift galaxies
A significant fraction of the high-redshift galaxies show strong Lyman
emission lines. For redshifts z>5, most known galaxies belong to this class.
However, so far not much is known about the physical structure and nature of
these objects. Our aim is to analyse the Lyman alpha emission in a sample of
high-redshift UV-continuum selected galaxies and to derive the physical
conditions that determine the Lyman alpha profile and the line strength.
VLT/FORS spectra with a resolution of R ~ 2000 of 16 galaxies in the redshift
range of z = 2.7 to 5 are presented. The observed Lyman alpha profiles are
compared with theoretical models. The Lyman alpha lines range from pure
absorption (EW = -17 Angstroem) to strong emission (EW = 153 Angstroem). Most
Lyman alpha emission lines show an asymmetric profile, and three galaxies have
a double-peaked profile. Both types of profiles can be explained by a uniform
model consisting of an expanding shell of neutral and ionised hydrogen around a
compact starburst region. The broad, blueshifted, low-ionisation interstellar
absorption lines indicate a galaxy-scale outflow of the ISM. The strengths of
these lines are found to be determined in part by the velocity dispersion of
the outflowing medium. We find star-formation rates of these galaxies ranging
from SFR(UV) = 1.2 to 63.2 Msun uncorrected for dust absorption. The Lyman
alpha emission strength of our target galaxies is found to be determined by the
amount of dust and the kinematics of the outflowing material.Comment: 11 pages, 6 figures. A&A accepte
WEBT multiwavelength monitoring and XMM-Newton observations of BL Lacertae in 2007-2008. Unveiling different emission components
In 2007-2008 we carried out a new multiwavelength campaign of the Whole Earth
Blazar Telescope (WEBT) on BL Lacertae, involving three pointings by the
XMM-Newton satellite, to study its emission properties. The source was
monitored in the optical-to-radio bands by 37 telescopes. The brightness level
was relatively low. Some episodes of very fast variability were detected in the
optical bands. The X-ray spectra are well fitted by a power law with photon
index of about 2 and photoelectric absorption exceeding the Galactic value.
However, when taking into account the presence of a molecular cloud on the line
of sight, the data are best fitted by a double power law, implying a concave
X-ray spectrum. The spectral energy distributions (SEDs) built with
simultaneous radio-to-X-ray data at the epochs of the XMM-Newton observations
suggest that the peak of the synchrotron emission lies in the near-IR band, and
show a prominent UV excess, besides a slight soft-X-ray excess. A comparison
with the SEDs corresponding to previous observations with X-ray satellites
shows that the X-ray spectrum is extremely variable. We ascribe the UV excess
to thermal emission from the accretion disc, and the other broad-band spectral
features to the presence of two synchrotron components, with their related SSC
emission. We fit the thermal emission with a black body law and the non-thermal
components by means of a helical jet model. The fit indicates a disc
temperature greater than 20000 K and a luminosity greater than 6 x 10^44 erg/s.Comment: 11 pages, 7 figures, accepted for publication in A&
Evaluating the role of paternal factors in aetiology and prognosis of recurrent pregnancy loss: Study protocol for a hospital-based multicentre case-control study and cohort study (REMI III project)
Introduction Recurrent pregnancy loss (RPL) is defined as the spontaneous demise of two or more pregnancies before the fetus reaches viability. Despite investigation of multiple known maternal risk factors, in more than 50% of couples, this condition remains unexplained. Studies focusing on paternal factors in RPL are scarce, and therefore, paternal evaluation in RPL is currently very limited. However, regarding single miscarriage, there are multiple publications suggesting a contributive role of paternal factors. In this project, we aim to identify paternal factors associated with RPL and to improve couple-specific prediction of future pregnancy outcomes by developing a prediction model containing both maternal and paternal factors. Methods and analysis In a case-control design, the relation between unexplained RPL and paternal age, lifestyle factors, sperm DNA damage and immunomodulatory factors in peripheral blood and semen will be studied. Prospectively, 135 couples with naturally conceived unexplained RPL (cases) and 135 fertile couples without a history of pregnancy loss (controls) will be included, with collection of paternal blood and semen samples and documentation of clinical and lifestyle characteristics. In addition, 600 couples from both groups will be included retrospectively. To adjust for confounders, multivariate logistic regression will be used. The predictive value of paternal and maternal factors will be studied in the total RPL cohort consisting of approximately 735 couples. The primary outcome of the cohort study is live birth within 5 years after initial visit of the clinic. Secondary outcomes are ongoing pregnancy, time interval until next pregnancy and pregnancy complications. Ethics and dissemination This project is approved by the Medical Research Ethics Committee
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Generation of an ultrabroadband supercontinuum in the mid-infrared region using dispersion-engineered GeAsSe photonic crystal fiber
An ultrabroadband mid-infrared (MIR) region supercontinuum (SC) is demonstrated numerically through dispersion-engineered traditional chalcogenide (ChG) photonic crystal fiber (PCF). By varying structural parameters pitch (hole to hole spacing) and air-hole diameter to pitch ratio, a number of 10-mm-long hexagonal PCFs made employing GeAsSe ChG glass as a core and air-holes of hexagonal lattice running through their lengths as a cladding are optimized to predict an efficient mid-infrared region SC spectral emission by pumping them using a tunable pump source between 2.9 and 3.3 µm. Simulations are carried out using an ultrashort pump pulse of 100-fs duration with a low pulse peak powers of between 3 and 4 kW into the optimized designs. It is found through numerical analysis that efficient SC spectral broadening with flattened output can be obtained by increasing the PCF pitch rather than increasing the PCF cladding containing air-hole diameter although a larger nonlinear coefficient could be obtained through increasing air-hole diameter of an optimized design. Simulation results show that the SC spectra can be broadened up to 12.2 µm for a certain design with a peak power of 3 kW. Using a peak power of 4 kW, it is possible to obtain SC spectral broadening beyond 14 µm with an optimized design spanning the wavelength range from 1.8 to 14 µm which covers the electromagnetic spectrum required for MIR molecular fingerprint region applications such as sensing and biological imaging
A photometric study of faint galaxies in the field of GRB000926
We present our B, V, Rc, and Ic observations of a 3.6' x 3' field centered on
the host galaxy of GRB000926 (RA(2000.0)=17h04m11s, DEC(2000.0)=+51d47'9.8'').
The observations were carried out on the 6-m Special Astrophysical Observatory
telescope using the SCORPIO instrument. The catalog of galaxies detected in
this field includes 264 objects for which the signal-to-noise ratio is larger
than 5 in each photometric band. The following limiting magnitudes in the
catalog correspond to this limitation: 26.6(B), 25.7(V), 25.8(Rc), and
24.5(Ic). The differential galaxy counts are in good agreement with previously
published CCD observations of deep fields. We estimated the photometric
redshifts for all of the cataloged objects and studied the color variations of
the galaxies with Z. For luminous spiral galaxies with M(B) < -18, we found no
evidence for any noticeable evolution of their linear sizes to Z~1.Comment: 10 pages, 7 figure
3D Lyman-alpha radiation transfer. III. Constraints on gas and stellar properties of z~3 Lyman break galaxies (LBG) and implications for high-z LBGs and Lyman-alpha emitters(LAEs)
The Aim of our study is to understand the variety of observed Lyman-alpha
(Lya) line profiles and strengths in Lyman Break Galaxies (LBGs) and Lya
emitters (LAEs), the physical parameters governing them, and hence deriving
constraints on the gas and dust content and stellar populations of these
objects.
Using our 3D Lya radiation transfer code including gas and dust (Verhamme et
al. 2006), we fit 11 LBGs from the FORS Deep Field with redshifts between 2.8
and 5 observed by Tapken et al. (2007). A simple geometry of a spherically
expanding shell of HI is adopted.
RESULTS : The variety of observed Lya profiles is successfully reproduced.
Most objects show outflow velocities of 150-200 km/s; two objects are most
likely quasi-static. The radial HI column density ranges from NH=2.10^{19} to
7.10^{20} cm^{-2}. Our Lya profile fits yield values of E(B-V)~0.05-0.2 for the
gas extinction. We find indications for a dust-to-gas ratio higher than the
Galactic value, and for a substantial scatter. The escape fraction of Lya
photons is found to be determined primarily by the extinction, and a simple fit
formula is proposed. Intrinsic EW(Lya)~50-100 Angstroms are found for 8/11
objects, as expected for stellar populations forming constantly over long
periods (> 10-100 Myr). In three cases we found indications for younger
populations. Correlations between the observed EW(Lya) and other observables
such as FWHM(Lya), E(B-V),SFR(UV) etc, are reproduced. We also show that there
is a clear overlap between LBGs and LAEs. Radiation transfer and dust effects
explain the increase of the LAE/LBG ratio, and a higher percentage of LBGs with
strong Lya emission with increasing redshift. [shortened]Comment: 26 pages, accepted for publication in A&
Immune-monitoring disease activity in primary membranous nephropathy
Primary membranous nephropathy (MN) is a glomerular disease mediated by autoreactive antibodies, being the main cause of nephrotic syndrome among adult patients. While the pathogenesis of MN is still controversial, the detection of autoantibodies against two specific glomerular antigens, phospholipase A2 receptor (PLA2R) and thrombospondin type 1 domain containing 7A (THSD7A), together with the beneficial effect of therapies targeting B cells, have highlighted the main role of autoreactive B cells driving this renal disease. In fact, the detection of PLA2R-specific IgG4 antibodies has resulted in a paradigm shift regarding the diagnosis as well as a better prediction of the progression and recurrence of primary MN. Nevertheless, some patients do not show remission of the nephrotic syndrome or do rapidly recur after immunosuppression withdrawal, regardless the absence of detectable anti-PLA2R antibodies, thus highlighting the need of other immune biomarkers for MN risk-stratification. Notably, the exclusive evaluation of circulating antibodies may significantly underestimate the magnitude of the global humoral memory immune response since it may exclude the role of antigen-specific memory B cells. Therefore, the assessment of PLA2R-specific B-cell immune responses using novel technologies in a functional manner may provide novel insight on the pathogenic mechanisms of B cells triggering MN as well as refine current immune-risk stratification solely based on circulating autoantibodies
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