459 research outputs found
Constraining halo occupation properties of X-ray AGNs using clustering of Chandra sources in the Bootes survey region
We present one of the most precise measurement to date of the spatial
clustering of X-ray selected AGNs using a sample derived from the Chandra X-ray
Observatory survey in the Bootes field. The real-space two-point correlation
function over a redshift interval from z=0.17 to z~3 is well described by the
power law, xi(r)=(r/r0)^-gamma, for comoving separations r<~20h^-1 Mpc. We find
gamma=1.84+-0.12 and r0 consistent with no redshift trend within the sample
(varying between r0=5.5+-0.6 h^-1 Mpc for =0.37 and r0=6.9+-1.0 h^-1 Mpc for
=1.28). Further, we are able to measure the projections of the two-point
correlation function both on the sky plane and in the line of sight. We use
these measurements to show that the Chandra/Bootes AGNs are predominantly
located at the centers of dark matter halos with the circular velocity Vmax>320
km/s or M_200 > 4.1e12 h^-1 Msun, and tend to avoid satellite galaxies in halos
of this or higher mass. The halo occupation properties inferred from the
clustering properties of Chandra/Bootes AGNs --- the mass scale of the parent
dark matter halos, the lack of significant redshift evolution of the clustering
length, and the low satellite fraction --- are broadly consistent with the
Hopkins et al. scenario of quasar activity triggered by mergers of
similarly-sized galaxies.Comment: Accepted to ApJ. The revision matches the accepted version. The most
significant changes include the recalculation of uncertainties using mock
catalogs and explicit comparison with the AGN HOD studies based on projected
correlation function, w(rp
The Mid-Infrared Properties of X-ray Sources
We combine the results of the Spitzer IRAC Shallow Survey and the Chandra
XBootes Survey of the 8.5 square degrees Bootes field of the NOAO Deep Wide-
Field Survey to produce the largest comparison of mid-IR and X-ray sources to
date. The comparison is limited to sources with X-ray fluxes >8x10-15 erg
cm-2s-1 in the 0.5-7.0 keV range and mid-IR sources with 3.6 um fluxes brighter
than 18.4 mag (12.3 uJy). In this most sensitive IRAC band, 85% of the 3086
X-ray sources have mid-IR counterparts at an 80% confidence level based on a
Bayesian matching technique. Only 2.5% of the sample have no IRAC counterpart
at all based on visual inspection. Even for a smaller but a significantly
deeper Chandra survey in the same field, the IRAC Shallow Survey recovers most
of the X-ray sources. A majority (65%) of the Chandra sources detected in all
four IRAC bands occupy a well-defined region of IRAC [3.6] - [4.5] vs [5.8] -
[8.0] color-color space. These X-ray sources are likely infrared luminous,
unobscured type I AGN with little mid-infrared flux contributed by the AGN host
galaxy. Of the remaining Chandra sources, most are lower luminosity type I and
type II AGN whose mid-IR emission is dominated by the host galaxy, while
approximately 5% are either Galactic stars or very local galaxies.Comment: Accepted for publication in Ap
The Chandra XBootes Survey - III: Optical and Near-IR Counterparts
The XBootes Survey is a 5-ks Chandra survey of the Bootes Field of the NOAO
Deep Wide-Field Survey (NDWFS). This survey is unique in that it is the largest
(9.3 deg^2), contiguous region imaged in X-ray with complementary deep optical
and near-IR observations. We present a catalog of the optical counterparts to
the 3,213 X-ray point sources detected in the XBootes survey. Using a Bayesian
identification scheme, we successfully identified optical counterparts for 98%
of the X-ray point sources. The optical colors suggest that the optically
detected galaxies are a combination of z<1 massive early-type galaxies and
bluer star-forming galaxies whose optical AGN emission is faint or obscured,
whereas the majority of the optically detected point sources are likely quasars
over a large redshift range. Our large area, X-ray bright, optically deep
survey enables us to select a large sub-sample of sources (773) with high X-ray
to optical flux ratios (f_x/f_o>10). These objects are likely high redshift
and/or dust obscured AGN. These sources have generally harder X-ray spectra
than sources with 0.1<f_x/f_o<10. Of the 73 X-ray sources with no optical
counterpart in the NDWFS catalog, 47 are truly optically blank down to R~25.5
(the average 50% completeness limit of the NDWFS R-band catalogs). These
sources are also likely to be high redshift and/or dust obscured AGN.Comment: 19 pages, 13 figures, ApJ accepted. Catalog can be found at:
http://www.noao.edu/noao/noaodeep or
ftp://archive.noao.edu/pub/catalogs/xbootes
AEGIS-X: The Chandra Deep Survey of the Extended Groth Strip
We present the AEGIS-X survey, a series of deep Chandra ACIS-I observations
of the Extended Groth Strip. The survey comprises pointings at 8 separate
positions, each with nominal exposure 200ks, covering a total area of
approximately 0.67 deg2 in a strip of length 2 degrees. We describe in detail
an updated version of our data reduction and point source detection algorithms
used to analyze these data. A total of 1325 band-merged sources have been found
to a Poisson probability limit of 4e-6, with limiting fluxes of 5.3e-17
erg/cm2/s in the soft (0.5-2 keV) band and 3.8e-16 erg/cm2/s in the hard (2-10
keV) band. We present simulations verifying the validity of our source
detection procedure and showing a very small, <1.5%, contamination rate from
spurious sources. Optical/NIR counterparts have been identified from the DEEP2,
CFHTLS, and Spitzer/IRAC surveys of the same region. Using a likelihood ratio
method, we find optical counterparts for 76% of our sources, complete to
R(AB)=24.1, and, of the 66% of the sources that have IRAC coverage, 94% have a
counterpart to a limit of 0.9 microJy at 3.6 microns (m(AB)=23.8). After
accounting for (small) positional offsets in the 8 Chandra fields, the
astrometric accuracy of the Chandra positions is found to be 0.8 arcsec RMS,
however this number depends both on the off-axis angle and the number of
detected counts for a given source. All the data products described in this
paper are made available via a public website.Comment: 17 pages, 9 figures. Accepted for publication in ApJS. Data products
are available at http://astro.imperial.ac.uk/research/aegis
Association between energy balance-related factors and clinical outcomes in patients with ovarian cancers:A systematic review and meta analysis
Background: This systematic review and meta-analysis synthesized evidence in patients with ovarian cancer at diagnosis and/or during first-line treatment on; (i) the association of body weight, body composition, diet, exercise, sedentary behavior, or physical fitness with clinical outcomes; and (ii) the effect of exercise and/or dietary interventions. Methods: Risk of bias assessments and best-evidence syntheses were completed. Meta-analyses were performed when ≥3 papers presented point estimates and variability measures of associations or effects. Results: Body mass index (BMI) at diagnosis was not significantly associated with survival. Although the following trends were not supported by the best-evidence syntheses, the meta-analyses revealed that a higher BMI was associated with a higher risk of post-surgical complications (n = 5, HR: 1.63, 95% CI: 1.06–2.51, p = 0.030), a higher muscle mass was associated with a better progression-free survival (n = 3, HR: 1.41, 95% CI: 1.04–1.91, p = 0.030) and a higher muscle density was associated with a better overall survival (n = 3, HR: 2.12, 95% CI: 1.62–2.79, p < 0.001). Muscle measures were not significantly associated with surgical or chemotherapy-related outcomes. Conclusions: The prognostic value of baseline BMI for clinical outcomes is limited, but muscle mass and density may have more prognostic potential. High-quality studies with comprehensive reporting of results are required to improve our understanding of the prognostic value of body composition measures for clinical outcomes. Systematic review registration number: PROSPERO identifier CRD42020163058
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