317 research outputs found
Mid-infrared sources in the ELAIS Deep X-ray Survey
We present a crossâcorrelation of the European Large Area Infrared Space Observatory (ISO) survey (ELAIS) with the ELAIS Deep Xâray Survey of the N1 and N2 fields. There are seven Chandra point sources with matches in the ELAIS Final Analysis 15âÎźm catalogue, out of a total of 28 extragalactic ISO sources present in the Chandra fields. Five of these are consistent with active galactic nuclei (AGN) giving an AGN fraction of âź19 per cent in the 15âÎźm flux range 0.8â6âmJy. We have coâadded the hard Xâray fluxes of the individually undetected ISO sources and find a low significance detection consistent with star formation in the remaining population. We combine our point source crossâcorrelation fraction with the XMMâNewton observations of the Lockman Hole and Chandra observations of the Hubble Deep Field North to constrain source count models of the midâinfrared galaxy population. The low dustâenshrouded AGN fraction in ELAIS implied by the number of crossâidentifications between the ELAIS midâinfrared sample and the Chandra point sources is encouraging for the use of midâinfrared surveys to constrain the cosmic star formation history, provided there are not further large undetected populations of Comptonâthick AGN
The ELAIS deep X-ray survey - I. Chandra source catalogue and first results
We present an analysis of two deep (75 ks) Chandra observations of the European Large Area Infrared Space Observatory (ISO) Survey (ELAIS) fields N1 and N2 as the first results from the ELAIS deep X-ray survey. This survey is being conducted in well-studied regions with extensive multiwavelength coverage. Here we present the Chandra source catalogues along with an analysis of source counts, hardness ratios and optical classifications. A total of 233 X-ray point sources are detected in addition to two soft extended sources, which are found to be associated with galaxy clusters. An overdensity of sources is found in N1 with 30 per cent more sources than N2, which we attribute to large-scale structure. A similar variance is seen between other deep Chandra surveys. The source count statistics reveal an increasing fraction of hard sources at fainter fluxes. The number of galaxy-like counterparts also increases dramatically towards fainter fluxes, consistent with the emergence of a large population of obscured sources
Technical tips to perform safe and effective Ultrasound Guided steroid joint injections in children
The XMM Large Scale Structure Survey: Properties and Two-Point Angular Correlations of Point-like Sources
We analyze X-ray sources detected over 4.2 pseudo-contiguous sq. deg. in the
0.5-2 keV and 2-10 keV bands down to fluxes of 2x10^{-15} and 8x10^{-15}
erg/s/cm^2 respectively, as part of the XMM Large Scale Structure Survey. The
logN-logS in both bands shows a steep slope at bright fluxes, but agrees well
with other determinations below ~2x10^{-14} erg/s/cm^2. The detected sources
resolve close to 30 per cent of the X-ray background in the 2-10 keV band. We
study the two-point angular clustering of point sources using nearest
neighbours and correlation function statistics and find a weak, positive signal
for ~1130 sources in the 0.5-2 keV band, but no correlation for ~400 sources in
the 2-10 keV band below scales of 100 arcsec. A sub-sample of ~200 faint
sources with hard X-ray count ratios, that is likely to be dominated by
obscured AGN, does show a positive signal with the data allowing for a large
scaling of the angular correlation length, but only at the ~2 (3) sigma level,
based on re-sampling (Poisson) statistics. We discuss possible implications and
emphasize the importance of wider, complete surveys in order to fully
understand the large scale structure of the X-ray sky.Comment: A&A in press; High resolution version at
http://www-xray.ast.cam.ac.uk/~pg/publications.htm
Two GCC boxes and AP2/ERF-domain transcription factor ORA59 in jasmonate/ethylene-mediated activation of the PDF1.2 promoter in Arabidopsis
Plant defense against microbial pathogens depends on the action of several endogenously produced hormones, including jasmonic acid (JA) and ethylene (ET). In defense against necrotrophic pathogens, the JA and ET signaling pathways synergize to activate a specific set of defense genes including PLANT DEFENSIN1.2 (PDF1.2). The APETALA2/Ethylene Response Factor (AP2/ERF)-domain transcription factor ORA59 acts as the integrator of the JA and ET signaling pathways and is the key regulator of JA- and ET-responsive PDF1.2 expression. The present study was aimed at the identification of elements in the PDF1.2 promoter conferring the synergistic response to JA/ET and interacting with ORA59. We show that the PDF1.2 promoter was activated synergistically by JA and the ET-releasing agent ethephon due to the activity of two GCC boxes. ORA59 bound in vitro to these GCC boxes and trans-activated the PDF1.2 promoter in transient assays via these two boxes. Using the chromatin immunoprecipitation technique we were able to show that ORA59 bound the PDF1.2 promoter in vivo. Finally, we show that a tetramer of a single GCC box conferred JA/ethephon-responsive expression, demonstrating that the JA and ET signaling pathways converge to a single type of GCC box. Therefore ORA59 and two functionally equivalent GCC box binding sites form the module that enables the PDF1.2 gene to respond synergistically to simultaneous activation of the JA and ET signaling pathways
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