Using a sample of 228 optically selected active galactic nuclei (AGNs) in the 0.01-6.3 redshift range with a high fraction of X-ray detections (81%-86%), we study the relation between rest-frame UV and soft X-ray emission and its evolution with cosmic time. The majority of the AGNs in our sample (155 objects) have been selected from the Sloan Digital Sky Survey (SDSS) in an unbiased way, rendering the sample results representative of all SDSS AGNs.
A sample of 576 X-ray-selected LINERs was constructed by combining data from the 3XMM-DR4 and SDSS-DR7 catalogues. The sample was used to investigate the fraction of galaxies hosting a LINER, finding that the fraction is a strong function of both stellar mass and black hole mass (increasing as f_LINER_{prop.to}M*^1.6+/-0.2^ and f_LINER_{propto}M_BH_^0.6+/-0.1^, respectively) and that it rises close to unity at the highest black hole masses and lowest X-ray luminosities. After obtaining radio flux densities from the FIRST survey, the sample was also used to investigate the Fundamental Plane of black hole activity - a scale-invariant relationship between black hole mass, X-ray luminosity and radio luminosity that is believed to hold across at least nine orders of magnitude of mass. There are key advantages in using only LINERs for the derivation as these are the counterparts of the 'low-hard' X-ray binaries for which the relationship is tightest. The Fundamental Plane was found to be log(L_R_/(erg/s)) = 0.65(+/-0.07)log(L_X_/(10^42^erg/s)) + 0.69(+/-0.10)log(M_BH_/10^8^M_{sun}_) + 38.35(+/-0.10). The scatter around the plane was 0.73+/-0.03dex, too large to suggest that the Fundamental Plane can be used as a tool to estimate black hole mass from the observables of X-ray and radio luminosity. The black hole mass scaling is sensitive to the slope of the mass - velocity dispersion relation and, in order to achieve consistency with X-ray binaries, the analysis favours a steep gradient for this relationship, as found in recent research.
We report results from a high-resolution optical spectroscopic survey aimed to search for nearby young associations and young stars among optical counterparts of ROSAT All-Sky Survey (<IX/10> and <IX/29>, X-ray sources in the Southern Hemisphere. We selected 1953 late-type (B-V>=0.6), potentially young, optical counterparts out of a total of 9574 1RXS sources for follow-up observations. At least one high-resolution spectrum was obtained for each of 1511 targets. This paper is the first in a series presenting the results of the SACY survey. Here we describe our sample and our observations. We describe a convergence method in the (UVW) velocity space to find associations. As an example, we discuss the validity of this method in the framework of the Beta Pic Association.
This catalog contains 107 sources in the energy range 2-18 keV, galactic latitude |b|>10{deg}. It results from the sky survey conducted by the Leiscester Sky Survey Instrument on Ariel V. The file "2a.dat" is the electronic version of the table 1 of the original paper, prepared by G. Share (Naval Research Laboratory). It contains 2 sources more than the original paper.
The catalog is a compilation of X-ray sources containing 677 objects known as of 1979 September. X-ray data for 677 sources are the result of X-ray sky surveys by rockets, balloons, and satellites during 1964-1979. The sky survey is practically complete to X-ray intensities of nearly 4 micro-Jy in the 2-6 keV range. The current version does not include the investigation by HEAO 2. The catalog includes source names, positions of the maximum probability densities, date of the measurements, the type of measuring systems, the ranges at which the measurement was performed, maximum intensities for constant sources, and ratio of the maximum observed value of intensity to the minimum one for variable sources. The catalog is an update of the publication, by the same authors, in 1979ApJS...41..327A
We present the latest results of the Clusters in the Zone of Avoidance (CIZA) survey, which is mapping large-scale structures behind the Milky Way by performing the first systematic search for galaxy clusters at low Galactic latitudes. The survey's approach, which uses X-ray emission to locate cluster candidates, minimizes the problems faced by optically selected cluster surveys, which have traditionally avoided this region of the sky due to the severe extinction present along the Galactic plane. We here present the second flux-limited CIZA cluster catalog, containing 57 X-ray-selected galaxy clusters, of which 88% are new discoveries. We use this sample to examine the degree to which known large-scale structures extend into the zone of avoidance and highlight newly discovered structures that have previously gone unnoticed.
The Extreme Ultraviolet Explorer satellite was launched on June 7, 1992 from Cape Canaveral, Florida on a Delta II rocket. The payload contains three EUV scanning telescopes equipped with imaging detectors as well as a Deep Survey Spectrometer instrument which divides the light from a fourth telescope between an imaging detector and three EUV spectrometers. The wavelength range is 10-60nm, corresponding to an energy range of 20-120eV, in the 4 bands: 10nm : Lexan/Boron, 58-174{AA}, 89{AA}peak DS: Lexan/Boron, 67-178{AA}, 91{AA}peak (Deep Survey) 20nm : Al/Ti/C, 156-234{AA}, 171{AA}peak DS: Al/C, 157-364{AA}, 171{AA}peak (Deep Survey) 40nm : Ti/Sb/Ti/Al, 368-590{AA}, 405{AA}peak 60nm : Sn/SiO, 519-742{AA}, 555{AA}peak More details about the EUVE performances may be found in the paper by Sirk et al. (1997ApJS..110..347S) The EUVE Source Catalog published in 1996 paper is made of three source tables, plus a list of associations for each table: - survey.dat lists the 514 objects detected during the all-sky survey. - deepsurv.dat lists the 35 sources detected by the deep survey of half the ecliptic plane; three deep survey objects are also detected in the all-sky survey. - detect.dat lists 188 sources that have been detected in other ways, principally by deep exposures with the scanner telescopes as part of the Right Angle Program through 24 December 1994 (later RAP detections are reported in the 1999 paper) The corresponding association tables are idsurvey, iddeepsu.dat and iddetect.dat respectively, in which one EUVE source may by associated to 0, one or more counterparts. In nearly all cases the associated objects lie within 1arcmin of the actual source position. The all-sky catalog of faint EUV sources published in 1997 lists the faint sources detected jointly by EUVE and ROSAT WFC. The 1999 paper lists the detections made from the observations since the first EUVE RAP catalog (1994 January) and covers 17% of the sky.
The Extreme Ultraviolet Explorer satellite was launched on June 7, 1992 from Cape Canaveral, Florida on a Delta II rocket. The payload contains three EUV scanning telescopes equipped with imaging detectors as well as a Deep Survey Spectrometer instrument which divides the light from a fourth telescope between an imaging detector and three EUV spectrometers. There are three source tables in this catalogue: - table1 lists count rates and positions of 514 objects detected during the all-sky survey. - table2 lists 35 sources detected by the deep survey of half the ecliptic plane; three deep survey objects are also detected in the all sky survey. - table3 lists 188 sources that have been detected in other ways, principally by deep exposures with the scanner telescopes as part of the Right Angle Program or by long exposures with the deep survey instrument; table3 includes right angle detections through December 24, 1994. Because the objects listed in table3 have been derived with a variety of instruments and exposure strategies, the flux limits and detection thresholds vary over a wide range; interested readers should consult the reference listed. Each table has an associated list of identified sources, id1, id2 and id3 (one EUVE source may by associated to 0, one or more counterparts); in nearly all cases they lie within 1 arcmin of the actual source position. The 534 objects in the "faint" part were detected jointly in the EUVE and in the ROSAT X-Ray Telescope 0.25keV band (50{AA}). This joint selection criterion permits use of a low count rate threshold in each survey, roughly 60% of the threshold used in the EUVE all-sky surveys, and 166 of the objects listed in the "faint" part are new EUV sources, appearing in neither the Second EUVE Source Catalog (tables 1 to 3) nor the ROSAT Wide Field Camera Second Catalog (J/MNRAS/274/1165)
The INTEGRAL mission provides a large data set for studying the hard X-ray properties of AGN and allows testing the unified scheme for AGN. We present analysis of INTEGRAL IBIS/ISGRI, JEM-X, and OMC data for 199 AGN that have been reported to be detected by INTEGRAL above 20keV. The data analysed here allow a significant spectral extraction on 148 objects and optical variability study of 57 AGN. The slopes of the hard X-ray spectra of Seyfert 1 and Seyfert 2 galaxies are found to be consistent within the uncertainties, whereas lower luminosities are measured for the more absorbed/type 2 AGN. The intermediate Seyfert 1.5 objects exhibit hard X-ray spectra consistent with those of Seyfert 1. When applying a Compton reflection model, the underlying continua appear still the same in Seyfert 1 and 2 with photon index 2, and the reflection strength is about R=1, when assuming different inclination angles. A significant correlation is found between the hard X-ray and optical luminosity and the mass of the central black hole in the sense that the more luminous objects appear to be more massive. There is also a general trend for the absorbed sources and type 2 AGN to have lower Eddington ratios. The black hole mass appears to form a fundamental plane together with the optical and X-ray luminosity of the form LV being proportional to LX^0.6^.M^0.2^, similar to that found between radio luminosity LR, LX, and M. The unified model for Seyfert galaxies seems to hold, showing in hard X-rays that the central engine is the same in Seyfert 1 and 2 but seen under different inclination angles and absorption.
We present the second ROSAT all-sky survey source catalogue, hereafter referred to as the 2RXS catalogue. This is the second publicly released ROSAT catalogue of point-like sources obtained from the ROSAT all-sky survey (RASS) observations performed with the position-sensitive proportional counter (PSPC) between June 1990 and August 1991, and is an extended and revised version of the bright and faint source catalogues. We used the latest version of the RASS processing to produce overlapping X-ray images of 6.4 by 6.4 degrees sky regions. To create a source catalogue, a likelihood-based detection algorithm was applied to these, which accounts for the variable point-spread function (PSF) across the PSPC field of view. Improvements in the background determination compared to 1RXS were also implemented. X-ray control images showing the source and background extraction regions were generated, which were visually inspected. Simulations were performed to assess the spurious source content of the 2RXS catalogue. X-ray spectra and light curves were extracted for the 2RXS sources, with spectral and variability parameters derived from these products. We obtained about 135,000 X-ray detections in the 0.1-2.4keV energy band down to a likelihood threshold of 6.5, as adopted in the 1RXS faint source catalogue. Our simulations show that the expected spurious content of the catalogue is a strong function of detection likelihood, and the full catalogue is expected to contain about 30 per cent spurious detections. A more conservative likelihood threshold of 9, on the other hand, yields about 71,000 detections with a 5 per cent spurious fraction. We recommend thresholds appropriate to the scientific application. X-ray images and overlaid X-ray contour lines provide an additional user product to evaluate the detections visually, and we performed our own visual inspections to flag uncertain detections. Intra-day variability in the X-ray light curves was quantified based on the normalised excess variance and a maximum amplitude variability analysis. X-ray spectral fits were performed using three basic models, a power law, a thermal plasma emission model, and black-body emission. Thirty-two large extended regions with diffuse emission and embedded point sources were identified and excluded from the present analysis. The 2RXS catalogue provides the deepest and cleanest X-ray all-sky survey catalogue in advance of eROSITA.
