Extended Medium Sensitivity Survey Research Articles

The extended medium sensitivity survey distant cluster sample - X-ray data and interpretation of the luminosity evolution

view Abstract Citations (357) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Extended Medium Sensitivity Survey Distant Cluster Sample: X-Ray Data and Interpretation of the Luminosity Evolution Henry, J. P. ; Gioia, I. M. ; Maccacaro, T. ; Morris, S. L. ; Stocke, J. T. ; Wolter, A. Abstract We describe the X-ray properties of a cluster of galaxies subsample of the Einstein Extended Medium Sensitivity Survey. A summary of this sample and its implications has been presented previously; this paper gives the full details. The cluster subsample is 98.4% identified and contains 93 X-ray-selected clusters to a redshift of 0.58. We derive the cluster X- ray luminosity function at three cosmic epochs. While our luminosity function agrees with previous determinations at the lowest redshifts, we find that the volume density of high-luminosity clusters is greater now than it was in the past. The normalization, shape, and time dependence of the luminosity function can be described by a simple hierarchical formation model with parameters which also describe the temperature function of an independent sample of low-redshift clusters. In this model the comoving hot gas density remains constant with time at least to redshifts of order 0.35. Publication: The Astrophysical Journal Pub Date: February 1992 DOI: 10.1086/171027 Bibcode: 1992ApJ...386..408H Keywords: Galactic Clusters; Galactic Evolution; Galactic Radiation; X Ray Astronomy; X Ray Sources; Astronomical Models; Brightness Distribution; Galactic Mass; Red Shift; Astrophysics; GALAXIES: CLUSTERING; GALAXIES: EVOLUTION; GALAXIES: LUMINOSITY FUNCTION; MASS FUNCTION; SURVEYS; X-RAYS: GALAXIES full text sources ADS | data products SIMBAD (108) NED (106)

Distant cooling flows

Luminous, extended Hα emission has been detected in 14 distant X-ray-selected clusters or galaxies (0.07 < z < 0.37). Eleven of these detections are from a complete flux-limited sample (f x ≥ 8 × 10 -13 ergs cm -2 s -1 , δ ≥ -20°) of 23 clusters extracted from the Einstein Extended Medium-Sensitivity Survey (EMSS). The Hα detections indicate the presence of cool gas embedded within hotter, X-ray-emitting cluster gas, a signature of a massive cooling flow

The Einstein Observatory Extended Medium-Sensitivity Survey. II - The optical identifications

The optical identifications are presented of the Einstein Extended Medium-Sensitivity Survey (EMSS), including the methodology used to optically identify the EMSS sources and the uncertainties involved with that process. The optical properties of the classes of X-ray, optical, and radio data for each of the identified and, as yet, unidentified sources of the survey are described. A new class of X-ray emitters, cooling flow galaxies, is proposed. The criteria used to determine whether the proposed optical counterpart to the X-ray source is a plausible identification are described. Plausibility is based on the optical classification of the counterpart, e.g., AGN, cluster, G star, and the X-ray-to-optical flux ratios previously observed for these classes of X-ray emitters. Two independent schemes of optical classification of the counterparts are used to check the plausibility of these identifications; one is based on moderate-resolution optical spectroscopy, and the other, on inferred X-ray luminosity and the overall energy distribution. 110 refs.

The number count distribution for X-ray-selected BL Lacertae objects and constraints on the luminosity function

A sample of 34 BL Lac objects extracted from the Einstein Extended Medium Sensitivity Survey is described. The number-count relationship is computed and compared with the results of other X-ray surveys. Then, different models of the intrinsic X-ray luminosity function are assumed and the effect of beamed X-ray emission is studied on the resulting observed luminosity function, comparing the predicted number-count distribution with the observed one.

MS 1603.6 + 2600, an unusual X-ray selected binary system at high Galactic latitude

The discovery of an eclipsing binary system at Galactic latitude 47 deg, found as a serendipitous X-ray source in the Einstein Extended Medium Sensitivity Survey, is described. The object has X-ray flux 1.1 x 10 to the -12th ergs/sq cm s (0.3-3.5 keV) and mean magnitude R = 19.4. An orbital period of 111 minutes is found. The problem discussed is whether the system has a white dwarf or neutron star primary, in the end preferring the neutron star primary model. If the system has either optical or X-ray luminosities typical of low mass X-ray binaries (LMXB), it must be at a very large distance (30-80 kpc). Blueshifted He I absorption is seen, indicating cool outflowing material, similar to that seen in the LMXB AC 211 in the globular cluster M15.

The Extended Medium Sensitivity Survey distant cluster sample - X-ray cosmological evolution

view Abstract Citations (259) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Extended Medium-Sensitivity Survey Distant Cluster Sample: X-Ray Cosmological Evolution Gioia, I. M. ; Henry, J. P. ; Maccacaro, T. ; Morris, S. L. ; Stocke, J. T. ; Wolter, A. Abstract The X-ray luminosity function of clusters of galaxies is determined at different cosmic epochs using data from the Einstein Observatory Extended Medium Sensitivity Survey. The sample consists of 67 X-ray-selected clusters that have been grouped in thrEe redshift shells. Evolution is detected in the X-ray properties of clusters. The present volume density of high-luminosity clusters is found to be greater than it was in the past. Given the still limited data set, this result should be regarded as preliminary. It can be interpreted as the consequence of either luminosity evolution or modest density evolution. Publication: The Astrophysical Journal Pub Date: June 1990 DOI: 10.1086/185744 Bibcode: 1990ApJ...356L..35G Keywords: Cosmology; Galactic Clusters; Sky Surveys (Astronomy); X Rays; Computational Astrophysics; Evolution (Development); Heao 2; Luminosity; Red Shift; Astrophysics; GALAXIES: CLUSTERING; GALAXIES: EVOLUTION; LUMINOSITY FUNCTION; X-RAYS: GENERAL full text sources ADS | data products SIMBAD (1)

The Einstein Observatory Extended Medium-Sensitivity Survey. I - X-ray data and analysis

This paper presents the results of the analysis of the X-ray data and the optical identification for the Einstein Observatory Extended Medium-Sensitivity Survey (EMSS). The survey consists of 835 serendipitous sources detected at or above 4 times the rms level in 1435 imaging proportional counter fields with centers located away from the Galactic plane. Their limiting sensitivities are about (5-300) x 10 to the -14th ergs/sq cm sec in the 0.3-3.5-keV energy band. A total area of 778 square deg of the high-Galactic-latitude sky has been covered. The data have been analyzed using the REV1 processing system, which takes into account the nonuniformities of the detector. The resulting EMSS catalog of X-ray sources is a flux-limited and homogeneous sample of astronomical objects that can be used for statistical studies.

X-ray-selected candidates for the RS CVn and W UMa classes of binary stars

view Abstract Citations (62) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-Ray-Selected Candidates for the RS CVn and W UMa Classes of Binary Stars Fleming, Thomas A. ; Gioia, Isabella M. ; Maccacaro, Tommaso Abstract X-ray luminosity, spectral type, radial-velocity variation, rotationally broadened line profile, and Ca II H and K line emission data are used to identify 12 new candidates for the RS CVn class and seven new candidates for the W UMa class from spectroscopic binaries which are contained in the Einstein Extended Medium Sensitivity Survey. Under the assumption that the candidates are genuine members of each class, local space density estimates of 4.47 + or - 1.19 x 10 to the -4th/cu pc for RS CVn binaries and 8.47 + or - 3.00 x 10 to the -5th/cu pc for W UMa binaries are found. Although the density estimate for the W UMa binaries is shown to be consistent with previous estimates obtained from optically selected samples, the estimate for the RS CVn binaries is more than an order of magnitude greater than previously determined space densities. Publication: The Astronomical Journal Pub Date: August 1989 DOI: 10.1086/115170 Bibcode: 1989AJ.....98..692F Keywords: Binary Stars; X Ray Stars; Calcium; H Lines; Heao 2; K Lines; Light Curve; Radial Velocity; Astrophysics; STARS: W URSAE MAJORIS; STARS: RS CVN full text sources ADS | data products SIMBAD (22)

The relation between X-ray emission and rotation in late-type stars from the perspective of X-ray selection

An X-ray-selected sample of 128 late-type (F-M) stars analyzed. These stars were identified as optical counterparts to serendipitous X-ray detections made by the Einstein Observatory Extended Medium Sensitivity Survey. Once identified as X-ray sources, the sample was followed up by an extensive program of optical observations, including high-resolution and low-resolution spectroscopy and photometry. Spectral types, luminosity classes, distances, X-ray luminosities, projected rotation rates (v sin i), radial velocities, and binary status have been determined for the sample.

X-ray Selected AGN from the Extended Medium Sensitivity Survey

The spectroscopic identification of the Extended Medium Sensitivity Survey (EMSS) sources now provides ∼350 X-ray selected QSOs and Seyfert galaxies (AGN in our working definition) and 30 BL Lac objects. Almost all of the AGN are spectroscopically similar to AGN found by other means but a few resemble normal galaxies so closely that they would not be identified as AGN easily by any other method.

OPTICAL ANALYSIS OF AN X-RAY-SELECTED SAMPLE OF STARS

I analyze an X-ray-selected sample of 128 late-type (F-M) stars. These stars were identified as optical counterparts to serendipitous X-ray detections made by the Einstein Observatory Extended Medium Sensitivity Survey. Once identified as X-ray sources, the stars were reobserved with an extensive program of optical observations consisting of highand low-resolution spectroscopy and photometry. Spectral types, luminosity classes, absolute magnitudes, distances, X-ray luminosities, projected rotation rates (v sin i), radial velocities, and binary status have been determined for the sample. I find that Lx is correlated with v sin i for single stars. However, Lx does not correlate with il sin i , which leads me to believe that the correlation seen with v sin i is actually a correlation with radius. Indeed, Lx correlates strongly with radius (color, mass) for main-sequence stars. This result provides a plausibility argument for rotational saturation in the coronae of late-type stars. Since this sample is flux limited, I use sky coverage and sensitivity information from the Einstein Observatory to calculate the end of the X-ray luminosity function for late-type stars. It appears that previously-calculated luminosity functions from optically selected samples have underestimated the number of X-ray F and G dwarfs. I have also discovered eight previously uncataloged M dwarfs within 25 pc of the Sun. My sample includes only M dwarfs of spectral type M5 and earlier, 93% of which are emission stars (i.e., type Me V), as well as two pre-main-sequence M stars. Arguments involving kinematics and stellar rotational velocities are used to estimate the age of these X-ray bright M dwarfs; they appear to be quite young (^ 1-3 X 109 yrs). Since the local space density of X-ray bright M dwarfs increases with mass, I infer a longer activity time scale for lower masses. M dwarfs later than M5 lie below the X-ray sensitivity limit of the sample. An upper limit of logLx = 27.45 is put on their coronal emission.

M dwarfs from the Einstein extended medium sensitivity survey

A complete sample of X-ray selected M dwarfs are presented which were serendipitously detected in the extended Einstein Observatory Medium Sensitivity Survey (MSS). The MSS detected only early M dwarfs (type MO through M5), 84 percent of which were emission stars (i.e., type Me V). It was calculated that the X-ray luminosity function for early M dwarfs with a log Lx greater than 27.6 and, by comparison to optical luminosity functions, find that about 25 percent of all early M dwarfs emit X-rays at a level greater than log Lx = 27.6. This result is compared to luminosity function estimates from optically selected samples and discussed in light of the sample's kinematic and mean age. Also presented is H alpha and Ca II K line fluxes for each member of the sample and it is shown that the surface H alpha and Ca II K luminosities do indeed correlate with Lx. The significance of this effect to theories of chromospheric and coronal heating is explained.

The X-ray spectra of the extragalactic sources in the Einstein extended medium sensitivity survey

The X-ray energy distribution of a large sample of faint extragalactic X-ray sources is studied. Two independent methods are used to determine that the average spectral index for the sources is about 0.95. The intrinsic dispersion of the spectral index distribution is about 0.36. The sources are characterized by a range of power law slopes in the soft X-ray band with a mean of 1.03 + 0.05 or - 0.06 and an intrinsic dispersion of about 0.36. The present analysis extends knowledge of the AGN spectral properties to sources which are about three times more distant and more than 10 times fainter than those previously studied. There is no evidence in the data for any change in the mean spectral index of either extragalactic sources as a whole or AGN in particular, as a function of the X-ray flux in the flux range 10 to the -11th to 10 to the -13th ergs/sq cm/s.