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Flux Limit (flux + limit)
Selected Abstracts3D Edge Transport Studies with EMC3-EIRENE for the Dynamic Ergodic Divertor (DED) at TEXTORCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-3 2008D. Harting Abstract In this paper we introduce some model extensions to the energy balances of the 3D fluid Monte-Carlo code EMC3 and study their influence on the simulation results for TEXTOR-DED. We implemented local kinetic corrections to the classical parallel heat conductivity of electrons (heat flux limit). Depending on the DED configuration, a cooling effect in the outermost SOL region, resulting from the heat flux limit, can be observed. In addition, also the adiabatic cooling term mnV2, which was neglected before, was implemented into the energy iterations. This term causes a localized cooling of the ions in front of the wall, where the plasma is accelerated towards the first wall. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The XMM,Newton Needles in the Haystack Survey: the local X-ray luminosity function of ,normal' galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005I. Georgantopoulos ABSTRACT In this paper we estimate the local (z < 0.22) X-ray luminosity function of ,normal' galaxies derived from the XMM,Newton Needles in the Haystack Survey. This is an on-going project that aims to identify X-ray-selected normal galaxies (i.e. non-AGN dominated) in the local Universe. We are using a total of 70 XMM,Newton fields covering an area of 11 deg2 which overlap with the Sloan Digital Sky Survey Data Release 2. Normal galaxies are selected on the basis of their resolved optical light profile, their low X-ray-to-optical flux ratio [log (fx/fo) < , 2] and soft X-ray colours. We find a total of 28 candidate normal galaxies to the 0.5,8 keV band flux limit of ,2 × 10,15 erg cm,2 s,1. Optical spectra are available for most sources in our sample (82 per cent). These provide additional evidence that our sources are bona fide normal galaxies with X-ray emission coming from diffuse hot gas emission and/or X-ray binaries rather than a supermassive black hole. 16 of our galaxies have narrow emission lines or a late-type spectral energy distribution (SED) while the remaining 12 present only absorption lines or an early-type SED. Combining our XMM,Newton sample with 18 local (z < 0.22) galaxies from the Chandra Deep Field North and South surveys, we construct the local X-ray luminosity function of normal galaxies. This can be represented with a Schechter form with a break at L,, 3+1.4,1.0× 1041 erg s,1 and a slope of ,, 1.78 ± 0.12. Using this luminosity function and assuming pure luminosity evolution of the form ,(1 +z)3.3 we estimate a contribution to the X-ray background from normal galaxies of ,10,20 per cent (0.5,8 keV). Finally, we derive, for the first time, the luminosity functions for early- and late-type systems separately. [source] A deep Chandra survey of the Groth Strip , I. The X-ray dataMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005K. Nandra ABSTRACT We present the results of a 200-ks Chandra observation of part of the Groth Strip region, using the ACIS-I instrument. We present a relatively simple method for the detection of point sources and calculation of limiting sensitivities, which we argue is at least as sensitive and more self-consistent than previous methods presented in the literature. A total of 158 distinct X-ray sources are included in our point-source catalogue in the ACIS-I area. The number counts show a relative dearth of X-ray sources in this region. For example, at a flux limit of 10,15 erg cm,2 s,1, around 20 per cent more soft-band sources are detected in the HDF-N and almost 50 per cent more in the ELAIS-N1 field, which we have analysed by the same method for comparison. We find, however, that these differences are consistent with Poisson variations at <2, significance, and therefore there is no evidence for cosmic variance based on these number counts alone. We determine the average spectra of the objects and find a marked difference between the soft-band-selected sources, which have ,= 1.9 typical of unobscured active galactic nuclei (AGN), and the hard-band-selected sources, which have ,= 1.0. Reassuringly, the sample as a whole has a mean spectrum of ,= 1.4 ± 0.1, the same as the X-ray background. None the less, our results imply that the fraction of sources with significant obscuration is only ,25 per cent, much less than predicted by standard AGN population synthesis models. This is confirmed by direct spectral fitting, with only a handful of objects showing evidence for absorption. After accounting for absorption, all objects are consistent with a mean intrinsic spectrum of ,= 1.76 ± 0.08, very similar to local Seyfert galaxies. The survey area is distinguished by having outstanding multiwaveband coverage. Comparison with these observations and detailed discussion of the X-ray source properties will be presented in future papers. [source] The ROSAT Brightest Cluster Sample , IV.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2000The extended sample We present a low-flux extension of the X-ray-selected ROSAT Brightest Cluster Sample (BCS) published in Paper I of this series. Like the original BCS and employing an identical selection procedure, the BCS extension is compiled from ROSAT All-Sky Survey (RASS) data in the northern hemisphere (,,0°) and at high Galactic latitudes (|b|,20°). It comprises 99 X-ray-selected clusters of galaxies with measured redshifts z,0.3 (as well as eight more at z>0.3) and total fluxes between 2.8×10,12 and 4.4×10,12 erg cm,2 s,1 in the 0.1,2.4 keV band (the latter value being the flux limit of the original BCS). The extension can be combined with the main sample published in 1998 to form the homogeneously selected extended BCS (eBCS), the largest and statistically best understood cluster sample to emerge from the RASS to date. The nominal completeness of the combined sample (defined with respect to a power-law fit to the bright end of the BCS log N,log S distribution) is relatively low at 75 per cent (compared with 90 per cent for the high-flux sample of Paper I). However, just as for the original BCS, this incompleteness can be accurately quantified, and thus statistically corrected for, as a function of X-ray luminosity and redshift. In addition to its importance for improved statistical studies of the properties of clusters in the local Universe, the low-flux extension of the BCS is also intended to serve as a finding list for X-ray-bright clusters in the northern hemisphere which we hope will prove useful in the preparation of cluster observations with the next generation of X-ray telescopes such as Chandra and XMM-Newton. An electronic version of the eBCS can be obtained from the following URL: http://www.ifa.hawaii.edu/~ebeling/clusters/BCS.html. [source] Resolving the source populations that contribute to the X-ray background: The 2 Ms Chandra Deep Field-North SurveyASTRONOMISCHE NACHRICHTEN, Issue 1-2 2003D. M. Alexander Abstract With , 2 Ms of exposure, the Chandra Deep Field-North (CDF-N) survey provides the deepest view of the Universe in the 0.5,8.0 keV band. Five hundred and three (503) X-ray sources are detected down to on-axis 0.5,2.0 keV and 2,8 keV flux limits of , 1.5 × 10,17 erg cm,2 s,1 and , 1.0 × 10,16 erg cm,2 s,1, respectively. These flux limits correspond to L0.5,8.0 keV, 3 × 1041 erg s,1 at z = 1 and L0.5,8.0 keV, 2 × 1043 erg s,1 at z = 6; thus this survey is sensitive enough to detect starburst galaxies out to moderate redshift and Seyfert galaxies out to high redshift. We present the X-ray observations, describe the broad diversity of X-ray selected sources, and review the prospects for deeper exposures. [source] | ||||||||||