1,021 research outputs found
Simulations of the OzDES AGN Reverberation Mapping Project
As part of the OzDES spectroscopic survey we are carrying out a large scale
reverberation mapping study of 500 quasars over five years in the 30
deg area of the Dark Energy Survey (DES) supernova fields. These quasars
have redshifts ranging up to 4 and have apparent AB magnitudes between
mag. The aim of the survey is to measure time lags between
fluctuations in the quasar continuum and broad emission line fluxes of
individual objects in order to measure black hole masses for a broad range of
AGN and constrain the radius-luminosity () relationship. Here we
investigate the expected efficiency of the OzDES reverberation mapping campaign
and its possible extensions. We expect to recover lags for 35-45\% of the
quasars. AGN with shorter lags and greater variability are more likely to yield
a lag, and objects with lags 6 months or 1 year are expected be
recovered the most accurately. The baseline OzDES reverberation mapping
campaign is predicted to produce an unbiased measurement of the
relationship parameters for H, Mg II 2798, and C IV
1549. However, extending the baseline survey by either increasing the
spectroscopic cadence, extending the survey season, or improving the emission
line flux measurement accuracy will significantly improve the parameter
constraints for all broad emission lines.Comment: Published online in MNRAS. 28 page
Quantitative Analysis of the DNA Methylation Sensitivity of Transcription Factor Complexes
Although DNA modifications play an important role in gene regulation, the underlying mechanisms remain elusive. We developed EpiSELEX-seq to probe the sensitivity of transcription factor binding to DNA modification in vitro using massively parallel sequencing. Feature-based modeling quantifies the effect of cytosine methylation (5mC) on binding free energy in a position-specific manner. Application to the human bZIP proteins ATF4 and C/EBPβ and three different Pbx-Hox complexes shows that 5mCpG can both increase and decrease affinity, depending on where the modification occurs within the protein-DNA interface. The TF paralogs tested vary in their methylation sensitivity, for which we provide a structural rationale. We show that 5mCpG can also enhance in vitro p53 binding and provide evidence for increased in vivo p53 occupancy at methylated binding sites, correlating with primed enhancer histone marks. Our results establish a powerful strategy for dissecting the epigenomic modulation of protein-DNA interactions and their role in gene regulation
Galaxies in Southern Bright Star Fields I. Near-infrared imaging
As a prerequisite for cosmological studies using adaptive optics techniques,
we have begun to identify and characterize faint sources in the vicinity of
bright stars at high Galactic latitudes. The initial phase of this work has
been a program of K_s imaging conducted with SOFI at the ESO NTT. From
observations of 42 southern fields evenly divided between the spring and autumn
skies, we have identified 391 additional stars and 1589 galaxies lying at
separations 60" from candidate guide stars in the magnitude range 9.0 R 12.4.
When analyzed as a "discrete deep field" with 131 arcmin^2 area, our dataset
gives galaxy number counts that agree with those derived previously over the
range 16 K_s 20.5. This consistency indicates that in the aggregate, our fields
should be suitable for future statistical studies. We provide our source
catalogue as a resource for users of large telescopes in the southern
hemisphere.Comment: 10 pages, 7 figures, accepted by A&A; Table 3 is available at
http://www.rzg.mpg.de/~ajb/data.html pending upload to CD
Hubble Space Telescope Imaging of the Circumnuclear Environments of the CfA Seyfert Galaxies: Nuclear Spirals and Fueling
We present archival Hubble Space Telescope images of the nuclear regions of
43 of the 46 Seyfert galaxies found in the volume-limited,
spectroscopically-complete CfA Redshift Survey sample. Using an improved method
of image contrast enhancement, we create detailed high-quality structure maps
that allow us to study the distributions of dust, star clusters, and
emission-line gas in the circumnuclear regions (100-1000 pc scales) and in the
associated host galaxy. Essentially all of these Seyfert galaxies have
circumnuclear dust structures with morphologies ranging from grand-design
two-armed spirals to chaotic dusty disks. In most Seyferts there is a clear
physical connection between the nuclear dust spirals on hundreds of parsec
scales and large-scale bars and spiral arms in the host galaxies proper. These
connections are particularly striking in the interacting and barred galaxies.
Such structures are predicted by numerical simulations of gas flows in barred
and interacting galaxies, and may be related to the fueling of AGN by matter
inflow from the host galaxy disks. We see no significant differences in the
circumnuclear dust morphologies of Seyfert 1s and 2s, and very few Seyfert 2
nuclei are obscured by large-scale dust structures in the host galaxies. If
Seyfert 2s are obscured Seyfert 1s, then the obscuration must occur on smaller
scales than those probed by HST.Comment: 29 pages, 11 figures. Accepted for publication in the ApJ. For
high-resolution figures see http://www.astronomy.ohio-state.edu/~pogge/CfA
Associations among osteocalcin, leptin and metabolic health in children ages 9-13 years in the United States
BACKGROUND:
This study aimed to investigate the relationships among osteocalcin, leptin and metabolic health outcomes in children ages 9-13 years.
METHODS:
This was a cross-sectional analysis of baseline data from 161 boys and 157 girls (ages 9-13 years) who previously participated in a double-blinded randomized placebo controlled trial of vitamin D supplementation. Relationships among fasting serum total osteocalcin (tOC), undercarboxylated osteocalcin (ucOC), leptin, and metabolic health outcomes were analyzed.
RESULTS:
Approximately 52% of study participants were obese based on percent body fat cutoffs (>25% for boys and >32% for girls) and about 5% had fasting serum glucose within the prediabetic range (i.e. 100 to 125 mg/dL). Serum tOC was not correlated with leptin, glucose, insulin, HOMA-IR, or HOMA-β after adjusting for percent body fat. However, serum ucOC negatively correlated with leptin (partial r = -0.16; p = 0.04) and glucose (partial r = -0.16; p = 0.04) after adjustment for percent body fat. Leptin was a positive predictor of insulin, glucose, HOMA-IR, and HOMA-β after adjusting for age, sex and percent body fat (all p < 0.001).
CONCLUSIONS:
These data depict an inverse relationship between leptin and various metabolic health outcomes in children. However, the notion that tOC or ucOC link fat with energy metabolism in healthy children was not supported
Cold Gas Outflows, Feedback, and the Shaping of Galaxies
There is wide consensus that galaxy outflows are one of the most important processes determining the evolution of galaxies through cosmic time, for example playing a key role in shaping the galaxy mass function. Our understanding of outflows and their drivers, however, is in its infancy --- this is particularly true for the cold (neutral atomic and molecular) phases of outflows, which present observational and modeling challenges. Here we outline several key open questions, briefly discussing the requirements of the observations necessary to make progress, and the relevance of several existing and planned facilities. It is clear that galaxy outflows, and particularly cold outflows, will remain a topic of active research for the next decade and beyond
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Accurate and sensitive quantification of protein-DNA binding affinity
Transcription factors (TFs) control gene expression by binding to genomic DNA in a sequence-specific manner. Mutations in TF binding sites are increasingly found to be associated with human disease, yet we currently lack robust methods to predict these sites. Here, we developed a versatile maximum likelihood framework named No Read Left Behind (NRLB) that infers a biophysical model of protein-DNA recognition across the full affinity range from a library of in vitro selected DNA binding sites. NRLB predicts human Max homodimer binding in near-perfect agreement with existing low-throughput measurements. It can capture the specificity of the p53 tetramer and distinguish multiple binding modes within a single sample. Additionally, we confirm that newly identified low-affinity enhancer binding sites are functional in vivo, and that their contribution to gene expression matches their predicted affinity. Our results establish a powerful paradigm for identifying protein binding sites and interpreting gene regulatory sequences in eukaryotic genomes
PTF10fqs: A Luminous Red Nova in the Spiral Galaxy Messier 99
The Palomar Transient Factory (PTF) is systematically charting the optical
transient and variable sky. A primary science driver of PTF is building a
complete inventory of transients in the local Universe (distance less than 200
Mpc). Here, we report the discovery of PTF10fqs, a transient in the luminosity
"gap" between novae and supernovae. Located on a spiral arm of Messier 99, PTF
10fqs has a peak luminosity of Mr = -12.3, red color (g-r = 1.0) and is slowly
evolving (decayed by 1 mag in 68 days). It has a spectrum dominated by
intermediate-width H (930 km/s) and narrow calcium emission lines. The
explosion signature (the light curve and spectra) is overall similar to thatof
M85OT2006-1, SN2008S, and NGC300OT. The origin of these events is shrouded in
mystery and controversy (and in some cases, in dust). PTF10fqs shows some
evidence of a broad feature (around 8600A) that may suggest very large
velocities (10,000 km/s) in this explosion. Ongoing surveys can be expected to
find a few such events per year. Sensitive spectroscopy, infrared monitoring
and statistics (e.g. disk versus bulge) will eventually make it possible for
astronomers to unravel the nature of these mysterious explosions.Comment: 12 pages, 12 figures, Replaced with published versio
The USNO-B Catalog
USNO-B is an all-sky catalog that presents positions, proper motions,
magnitudes in various optical passbands, and star/galaxy estimators for
1,042,618,261 objects derived from 3,643,201,733 separate observations. The
data were obtained from scans of 7,435 Schmidt plates taken for the various sky
surveys during the last 50 years. USNO-B1.0 is believed to provide all-sky
coverage, completeness down to V = 21, 0.2 arcsecond astrometric accuracy at
J2000, 0.3 magnitude photometric accuracy in up to five colors, and 85%
accuracy for distinguishing stars from non-stellar objects. A brief discussion
of various issues is given here, but the actual data are available from
http://www.nofs.navy.mil and other sites.Comment: Accepted by Astronomical Journa
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