S. S. Murray

Erratum: "Chandra Sample of Nearby Relaxed Galaxy Clusters: Mass, Gas Fraction, and Mass-Temperature Relation"

We present gas and total mass profiles for 13 low-redshift, relaxed clusters spanning a temperature range 0.7-9 keV, derived from all available Chandra data of sufficient quality. In all clusters, gas-temperature profiles are measured to large radii (Vikhlinin et al.) so that direct hydrostatic mass estimates are possible to nearly r500 or beyond. The gas density was accurately traced to larger radii; its profile is not described well by a beta model, showing continuous steepening with radius. The derived ρtot profiles and their scaling with mass generally follow the Navarro-Frenk-White model with concentration expected for dark matter halos in ΛCDM cosmology. However, in three cool clusters, we detect a central mass component in excess of the Navarro-Frenk-White profile, apparently associated with their cD galaxies. In the inner region (r < 0.1r500), the gas density and temperature profiles exhibit significant scatter and trends with mass, but they become nearly self-similar at larger radii. Correspondingly, we find that the slope of the mass-temperature relation for these relaxed clusters is in good agreement with the simple self-similar behavior, M500 Tα, where α = (1.5-1.6) ± 0.1, if the gas temperatures are measured excluding the central cool cores. The normalization of this M-T relation is significantly, by ≈30%, higher than most previous X-ray determinations. We derive accurate gas mass fraction profiles, which show an increase with both radius and cluster mass. The enclosed fgas profiles within r2500 0.4r500 have not yet reached any asymptotic value and are still far (by a factor of 1.5-2) from the universal baryon fraction according to the cosmic microwave background (CMB) observations. The fgas trends become weaker and its values closer to universal at larger radii, in particular, in spherical shells r2500 < r < r500.

CHANDRA CLUSTER COSMOLOGY PROJECT III: COSMOLOGICAL PARAMETER CONSTRAINTS

Chandra observations of large samples of galaxy clusters detected in X-rays by ROSAT provide a new, robust determination of the cluster mass functions at low and high redshifts. Statistical and systematic errors are now sufficiently small, and the redshift leverage sufficiently large for the mass function evolution to be used as a useful growth of a structure-based dark energy probe. In this paper, we present cosmological parameter constraints obtained from Chandra observations of 37 clusters withz �= 0.55 derived from 400 deg 2 ROSAT serendipitous survey and 49 brightest z ≈ 0.05 clusters detected in the All-Sky Survey. Evolution of the mass function between these redshifts requires ΩΛ > 0 with a ∼ 5σ significance, and constrains the dark energy equation- of-state parameter to w0 =− 1.14 ± 0.21, assuming a constant w and a flat universe. Cluster information also significantly improves constraints when combined with other methods. Fitting our cluster data jointly with the latest supernovae, Wilkinson Microwave Anisotropy Probe, and baryonic acoustic oscillation measurements, we obtain w0 =− 0.991 ± 0.045 (stat) ±0.039 (sys), a factor of 1.5 reduction in statistical uncertainties, and nearly a factor of 2 improvement in systematics compared with constraints that can be obtained without clusters. The joint analysis of these four data sets puts a conservative upper limit on the masses of light neutrinos mν < 0.33 eV at 95% CL. We also present updated measurements of ΩMh and σ8 from the low-redshift cluster mass function.

Chandra Cluster Cosmology Project. II. Samples and X-Ray Data Reduction

We discuss the measurements of the galaxy cluster mass functions at z 0.05 and z 0.5 using high-quality Chandra observations of samples derived from the ROSAT PSPC All-Sky and 400 deg2 surveys. We provide a full reference for the data analysis procedures, present updated calibration of relations between the total cluster mass and its X-ray indicators (TX , M gas, and YX ) based on a subsample of low-z relaxed clusters, and present a first measurement of the evolving LX -M tot relation (with M tot estimated from YX ) obtained from a well defined statistically complete cluster sample and with appropriate corrections for the Malmquist bias applied. Finally, we present the derived cluster mass functions, estimate the systematic uncertainties in this measurement, and discuss the calculation of the likelihood function. We confidently measure the evolution in the cluster comoving number density at a fixed mass threshold, e.g., by a factor of 5.0 ? 1.2 at M 500 = 2.5 ? 1014 h ?1 M ? between z = 0 and 0.5. This evolution reflects the growth of density perturbations, and can be used for the cosmological constraints complementing those from the distance-redshift relation.

An Overview of the Performance and Scientific Results From the Chandra X-Ray Observatory (CXO)

ABSTRACT The Chandra X‐Ray Observatory (CXO), the X‐ray component of NASA’s Great Observatories, was launched on 1999 July 23 by the space shuttle Columbia. After satellite systems activation, the first X‐rays focused by the telescope were observed on 1999 August 12. Beginning with the initial observation it was clear that the telescope had survived the launch environment and was operating as expected. Despite an initial surprise due to the discovery that the telescope was far more efficient for concentrating CCD‐damaging low‐energy protons than had been anticipated, the observatory is performing well and is returning superb scientific data. Together with other space observatories, most notably XMM‐Newton, it is clear that we have entered a new era of discovery in high‐energy astrophysics.

Chandra temperature profiles for a sample of nearby relaxed galaxy clusters

We present Chandra gas temperature profiles at large radii for a sample of 13 nearby, relaxed galaxy clusters and groups, which includes A133, A262, A383, A478, A907, A1413, A1795, A1991, A2029, A2390, MKW 4, RX J1159+5531, and USGC S152. The sample covers a range of average temperatures from 1 to 10 keV. The clusters are selected from the archive or observed by us to have sufficient exposures and off-center area coverage to enable accurate background subtraction and reach the temperature accuracy of better than 20%-30% at least to r = (0.4-0.5)r180 and for the three best clusters to (0.6-0.7)r180. For all clusters, we find cool gas in the cores, outside of which the temperature reaches a peak at r ~ 0.15r180 and then declines to ~0.5 of its peak value at r 0.5r180. When the profiles are scaled by the cluster average temperature (excluding cool cores) and the estimated virial radius, they show large scatter at small radii but remarkable similarity at r > (0.1-0.2)r180 for all but one cluster (A2390). Our results are in good agreement with previous measurements from ASCA by Markevitch et al. and from BeppoSAX by De Grandi & Molendi. Four clusters have recent XMM-Newton temperature profiles, two of which agree with our results, and we discuss reasons for disagreement for the other two. The overall shape of the temperature profiles at large radii is reproduced in recent cosmological simulations.

Direct Constraints on the Dark Matter Self-Interaction Cross Section from the Merging Galaxy Cluster 1E 0657–56

We compare new maps of the hot gas, dark matter, and galaxies for 1E 0657-56, a cluster with a rare, high-velocity merger occurring nearly in the plane of the sky. The X-ray observations reveal a prominent bow shock and a bullet-like gas subcluster just exiting the collision site. The optical image shows that the gas bullet lags behind the subcluster galaxies; the weak-lensing mass map reveals a dark matter clump lying ahead of the collisional gas bullet, but coincident with the effectively collisionless galaxies. From these observations, one can directly constrain the cross-section of the dark matter self-interaction. That the dark matter is not fluid-like can be seen directly from the maps; more quantitative limits can be derived from four simple independent arguments. Our most sensitive constraint, σ/m<1 cm2 g−1, comes from the consistency of the subcluster mass-to-light ratio with the main cluster (and universal) value, which rules out a large mass loss due to dark matter particle collisions.

A Textbook Example of a Bow Shock in the Merging Galaxy Cluster 1E 0657–56

In the representative embodiments of the new and improved methods and apparatus disclosed herein for controlling multicharge perforating guns or core-sampling guns, the gun-control system of the present invention includes a selectively-operable multi-contact switch assembly operative from the surface to sequentially connect a group of electrically-detonatable charges into a firing circuit for consecutively firing the charges on the gun. An array of serially-connected Zener diodes cooperatively associated with the switch assembly provides indications at the surface showing which of the several charges is then connected into the gun-firing circuit. The new and improved gun-control system also includes a shot-monitoring system which provides additional surface indications from which it can be determined whether the charges on the gun are being successfully fired and, at least approximately, that they are being consecutively fired.

The Fourth Uhuru Catalog of X-Ray Sources

Positions and intensities are presented for 339 X-ray sources observed by the Uhuru (SAS A) X-ray satellite observatory. We find good agreement between the sources in this catalog and those in the 3U and 2A catalogs. Optical and radio counterparts are suggested based on positional coincidence. The major classes of identified objects include binary stellar systems, supernova remnants, Seyfert galaxies, clusters of galaxies, and posibly the new class of superclusters of galaxies.

Chandra Observations of “The Antennae” Galaxies (NGC 4038/9)

We report the results of a deep Chandra ACIS pointing at the merging system NGC 4038/9. We detect an extraordinarily luminous population of X-ray sources, with luminosity well above that of XRBs in M31 and the Milky Way. If these sources are unbeamed XRBs, our observations may point to them being 10-(a few)100 M☉ black hole counterparts. We detect an X-ray bright hot ISM, with features including bright superbubbles associated with the actively star-forming knots, regions where hot and warm (Hα) ISM intermingle, and a large-scale outflow.

Low-Resolution Spectral Templates for Active Galactic Nuclei and Galaxies from 0.03 to 30 μm

We present a set of low-resolution empirical spectral energy distribution (SED) templates for active galactic nuclei (AGNs) and galaxies in the wavelength range from 0.03 ?m to 30 ?m based on the multi-wavelength photometric observations of the NOAO Deep-Wide Field Survey Bo?tes field and the spectroscopic observations of the AGN and Galaxy Evolution Survey. Our training sample is comprised of 14,448 galaxies in the redshift range 0 z 1 and 5347 likely AGNs in the range 0 z 5.58. The galaxy templates correspond to the SED templates presented in 2008 by Assef et al. extended into the UV and mid-IR by the addition of FUV and NUV GALEX and MIPS 24 ?m data for the field. We use our templates to determine photometric redshifts for galaxies and AGNs. While they are relatively accurate for galaxies (? z /(1 + z) = 0.04, with 5% outlier rejection), their accuracies for AGNs are a strong function of the luminosity ratio between the AGN and galaxy components. Somewhat surprisingly, the relative luminosities of the AGN and its host are well determined even when the photometric redshift is significantly in error. We also use our templates to study the mid-IR AGN selection criteria developed by Stern et al. in 2005 and Lacy et al. in 2004. We find that the Stern et al. criterion suffers from significant incompleteness when there is a strong host galaxy component and at z 4.5, when the broad H? emission line is redshifted into the [3.6] band, but that it is little contaminated by low- and intermediate-redshift galaxies. The Lacy et al. criterion is not affected by incompleteness at z 4.5 and is somewhat less affected by strong galaxy host components, but is heavily contaminated by low-redshift star-forming galaxies. Finally, we use our templates to predict the color-color distribution of sources in the upcoming Wide-Field Infrared Survey Explorer (WISE) mission and define a color criterion to select AGNs analogous to those developed for IRAC photometry. We estimate that in between 640,000 and 1,700,000 AGNs will be identified by these criteria, but without additional information, WISE-selected quasars will have serious completeness problems for z 3.4.We present a set of low resolution empirical SED templates for AGNs and galaxies in the wavelength range from 0.03 to 30 microns. These templates form a non-negative basis of the color space of such objects and have been derived from a combination 14448 galaxies and 5347 likely AGNs in the NDWFS Bootes field. We briefly describe how the templates are derived and discuss some applications of them. In particular, we discuss biases in commonly used AGN mid-IR color selection criteria and the expected distribution of sources in the current WISE satellite mission.