232 research outputs found
: A flexible chemical evolution model for abundance fitting - Do the Sun's abundances alone constrain chemical evolution models?
Elemental abundances of stars are the result of the complex enrichment
history of their galaxy. Interpretation of observed abundances requires
flexible modeling tools to explore and quantify the information about Galactic
chemical evolution (GCE) stored in such data. Here we present Chempy, a newly
developed code for GCE modeling, representing a parametrized open one-zone
model within a Bayesian framework. A Chempy model is specified by a set of 5-10
parameters that describe the effective galaxy evolution along with the stellar
and star-formation physics: e.g. the star-formation history, the feedback
efficiency, the stellar initial mass function (IMF) and the incidence of
supernova type Ia (SN Ia). Unlike established approaches, Chempy can sample the
posterior probability distribution in the full model parameter space and test
data-model matches for different nucleosynthetic yield sets. We extend Chempy
to a multi-zone scheme. As an illustrative application, we show that
interesting parameter constraints result from only the ages and elemental
abundances of Sun, Arcturus and the present-day interstellar medium (ISM). For
the first time, we use such information to infer IMF parameter via GCE
modeling, where we properly marginalize over nuisance parameters and account
for different yield sets. We find that of the IMF %
explodes as core-collapse SN, compatible with Salpeter 1955. We also constrain
the incidence of SN Ia per 10^3 Msun to 0.5-1.4. At the same time, this Chempy
application shows persistent discrepancies between predicted and observed
abundances for some elements, irrespective of the chosen yield set. These
cannot be remedied by any variations of Chempy's parameters and could be an
indication for missing nucleosynthetic channels. Chempy should be a powerful
tool to confront predictions from stellar nucleosynthesis with far more complex
abundance data sets.Comment: 19 pages, 17 figures, accepted for publication in A&A, python code:
https://github.com/jan-rybizki/Chemp
AGN's UV and X-ray luminosities in clumpy accretion flows
We consider the fuelling of the central massive black hole in Active Galactic
Nuclei, through an inhomogeneous accretion flow. Performing simple analytical
treatments, we show that shocks between elements (clumps) forming the accretion
flow may account for the UV and X-ray emission in AGNs. In this picture, a
cascade of shocks is expected, where optically thick shocks give rise to
optical/UV emission, while optically thin shocks give rise to X-ray emission.
The resulting blue bump temperature is found to be quite similar in different
AGNs. We obtain that the ratio of X-ray luminosity to UV luminosity is smaller
than unity, and that this ratio is smaller in massive objects compared to less
massive sources. This is in agreement with the observed ratio
and suggests a possible interpretation of the
anticorrelation.Comment: 8 pages, 1 figure, accepted for publication in A&
LBT/LUCIFER Observations of the z~2 Lensed Galaxy J0900+2234
We present rest-frame optical images and spectra of the gravitationally
lensed, star-forming galaxy J0900+2234 (z=2.03). The observations were
performed with the newly commissioned LUCIFER1 near-infrared instrument mounted
on the Large Binocular Telescope (LBT). We fit lens models to the rest-frame
optical images and find the galaxy has an intrinsic effective radius of 7.4 kpc
with a lens magnification factor of about 5 for the A and B components. We also
discovered a new arc belonging to another lensed high-z source galaxy, which
makes this lens system a potential double Einstein ring system. Using the high
S/N rest-frame optical spectra covering H+K band, we detected Hbeta, OIII,
Halpha, NII and SII emission lines. Detailed physical properties of this high-z
galaxy were derived. The extinction towards the ionized HII regions (E_g(B-V))
is computed from the flux ratio of Halpha and Hbeta and appears to be much
higher than that towards stellar continuum (E_s(B-V)), derived from the optical
and NIR broad band photometry fitting. The metallicity was estimated using N2
and O3N2 indices. It is in the range of 1/5-1/3 solar abundance, which is much
lower than the typical z~2 star-forming galaxies. From the flux ratio of SII
6717 and 6732, we found that the electron number density of the HII regions in
the high-z galaxy were >1000 cm^-3, consistent with other z~2 galaxies but much
higher than that in local HII regions. The star-formation rate was estimated
via the Halpha luminosity, after correction for the lens magnification, to be
about 365\pm69 Msun/yr. Combining the FWHM of Halpha emission lines and the
half-light radius, we found the dynamical mass of the lensed galaxy is
5.8\pm0.9x10^10 Msun. The gas mass is 5.1\pm1.1x10^10~Msun from the H\alpha
flux surface density by using global Kennicutt-Schmidt Law, indicating a very
high gas fraction of 0.79\pm0.19 in J0900+2234.Comment: 11 pages, 6 figures accepted by ApJ, revised based on referee repor
Genomes of Ellobius species provide insight into the evolutionary dynamics of mammalian sex chromosomes
The X and Y sex chromosomes of placental mammals show hallmarks of a tumultuous evolutionary past. The X Chromosome has a rich and conserved gene content, while the Y Chromosome has lost most of its genes. In the Transcaucasian mole vole Ellobius lutescens, the Y Chromosome including Sry has been lost, and both females and males have a 17,X diploid karyotype. Similarly, the closely related Ellobius talpinus, has a 54,XX karyotype in both females and males. Here, we report the sequencing and assembly of the E. lutescens and E. talpinus genomes. The results indicate that the loss of the Y Chromosome in E. lutescens and E. talpinus occurred in two independent events. Four functional homologs of mouse Y-Chromosomal genes were detected in both female and male E. lutescens, of which three were also detected in the E. talpinus genome. One of these is Eif2s3y, known as the only Y-derived gene that is crucial for successful male meiosis. Female and male E. lutescens can carry one and the same X Chromosome with a largely conserved gene content, including all genes known to function in X Chromosome inactivation. The availability of the genomes of these mole vole species provides unique models to study the dynamics of sex chromosome evolution
The environment of weak emission-line quasars
The nature of weak emission-line quasars (WLQs) is probed by comparing the
Baldwin effect (BEff) in WLQs and normal quasars (QSOs). We selected 81
high-redshift (z>2.2) and 2 intermediate-redshift (z=1.66 and 1.89) WLQs. Their
rest-frame equivalent widths (EWs) of the C IV emission-line and their
Eddington ratio were obtained from the Sloan Digital Sky Survey Data Release 7
(SDSS DR7) Quasar Catalogue or from Diamond-Stanic et al. We compare the
parameters of WLQs with these of 81 normal quasars from Bright Quasar Survey
(BQS) and 155 radio-quiet and radio-intermediate quasars detected by SDSS and
Chandra. The influence of the Eddington ratio, Lbol/Ledd, and the X-ray to
optical luminosity ratio,alpha_ox, on the BEff is analysed. We find that WLQs
follow a different relationship on the EW(CIV)-Lbol/Ledd plane than normal
quasars. This relationship disagrees with the super-Eddington hypothesis. The
weakness/absence of emission-lines in WLQs does not seem to be caused by their
extremely soft ionizing continuum but by low covering factor (Omega) of their
broad line region (BLR). Comparing emission-line intensities indicates that the
ratios of high-ionization line and low-ionization line regions (i.e.
Omega_(HIL)/Omega_(LIL)) are lower in WLQs than in normal QSOs. The covering
factor of the regions producing C IV and Lyalpha emission-lines are similar in
both WLQs and QSOs.Comment: 9 pages, 3 figures, 2 tables. Accepted for publication in MNRAS.
Minor changes (corrected typos) to match published versio
CIV Emission and the Ultraviolet through X-ray Spectral Energy Distribution of Radio-Quiet Quasars
In the restframe UV, two of the parameters that best characterize the range
of emission-line properties in quasar broad emission-line regions are the
equivalent width and the blueshift of the CIV line relative to the quasar rest
frame. We explore the connection between these emission-line properties and the
UV through X-ray spectral energy distribution (SED) for radio-quiet (RQ)
quasars. Our sample consists of a heterogeneous compilation of 406 quasars from
the Sloan Digital Sky Survey and Palomar-Green survey that have well-measured
CIV emission-line and X-ray properties (including 164 objects with measured
Gamma). We find that RQ quasars with both strong CIV emission and small CIV
blueshifts can be classified as "hard-spectrum" sources that are (relatively)
strong in the X-ray as compared to the UV. On the other hand, RQ quasars with
both weak CIV emission and large CIV blueshifts are instead "soft-spectrum"
sources that are (relatively) weak in the X-ray as compared to the UV. This
work helps to further bridge optical/soft X-ray "Eigenvector 1" relationships
to the UV and hard X-ray. Based on these findings, we argue that future work
should consider systematic errors in bolometric corrections (and thus accretion
rates) that are derived from a single mean SED. Detailed analysis of the CIV
emission line may allow for SED-dependent corrections to these quantities.Comment: AJ, in press; 39 pages, 11 figures, 3 table
A Quasar Catalog with Simultaneous UV, Optical and X-ray Observations by Swift
We have compiled a catalog of optically-selected quasars with simultaneous
observations in UV/optical and X-ray bands by the Swift Gamma Ray Burst
Explorer. Objects in this catalog are identified by matching the Swift
pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The
final catalog contains 843 objects, among which 637 have both UVOT and XRT
observations and 354 of which are detected by both instruments. The overall
X-ray detection rate is ~60% which rises to ~85% among sources with at least 10
ks of XRT exposure time. We construct the time-averaged spectral energy
distribution for each of the 354 quasars using UVOT photometric measurements
and XRT spectra. From model fits to these SEDs, we find that the big blue bump
contributes about 0.3 dex to the quasar luminosity. We re-visit the
alpha_ox-L_uv relation by selecting a clean sample with only type 1 radio-quiet
quasars; the dispersion of this relation is reduced by at least 15% compared to
studies that use non-simultaneous UV/optical and X-ray data. We only found a
weak correlation between L/L_Edd and alpha_uv. We do not find significant
correlations between alpha_x and alpha_ox, alpha_ox and alpha_uv, and alpha_x
and Log L(0.3-10 keV). The correlations between alpha_uv and alpha_x, alpha_ox
and alpha_x, alpha_ox and alpha_uv, L/L_Edd and alpha_x, and L/L_Edd and
alpha_ox are stronger amongst low-redshift quasars, indicating that these
correlations are likely driven by the changes of SED shape with accretion
state.Comment: 63 pages, 22 figures, accepted by ApJ
Brain oscillations and connectivity in autism spectrum disorders (ASD):new approaches to methodology, measurement and modelling
Although atypical social behaviour remains a key characterisation of ASD, the presence ofsensory and perceptual abnormalities has been given a more central role in recentclassification changes. An understanding of the origins of such aberrations could thus prove afruitful focus for ASD research. Early neurocognitive models of ASD suggested that thestudy of high frequency activity in the brain as a measure of cortical connectivity mightprovide the key to understanding the neural correlates of sensory and perceptual deviations inASD. As our review shows, the findings from subsequent research have been inconsistent,with a lack of agreement about the nature of any high frequency disturbances in ASD brains.Based on the application of new techniques using more sophisticated measures of brainsynchronisation, direction of information flow, and invoking the coupling between high andlow frequency bands, we propose a framework which could reconcile apparently conflictingfindings in this area and would be consistent both with emerging neurocognitive models ofautism and with the heterogeneity of the condition
ARIA 2016 : Care pathways implementing emerging technologies for predictive medicine in rhinitis and asthma across the life cycle
The Allergic Rhinitis and its Impact on Asthma (ARIA) initiative commenced during a World Health Organization workshop in 1999. The initial goals were (1) to propose a new allergic rhinitis classification, (2) to promote the concept of multi-morbidity in asthma and rhinitis and (3) to develop guidelines with all stakeholders that could be used globally for all countries and populations. ARIA-disseminated and implemented in over 70 countries globally-is now focusing on the implementation of emerging technologies for individualized and predictive medicine. MASK [MACVIA (Contre les Maladies Chroniques pour un Vieillissement Actif)-ARIA Sentinel NetworK] uses mobile technology to develop care pathways for the management of rhinitis and asthma by a multi-disciplinary group and by patients themselves. An app (Android and iOS) is available in 20 countries and 15 languages. It uses a visual analogue scale to assess symptom control and work productivity as well as a clinical decision support system. It is associated with an inter-operable tablet for physicians and other health care professionals. The scaling up strategy uses the recommendations of the European Innovation Partnership on Active and Healthy Ageing. The aim of the novel ARIA approach is to provide an active and healthy life to rhinitis sufferers, whatever their age, sex or socio-economic status, in order to reduce health and social inequalities incurred by the disease.Peer reviewe
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