Wayne A. Barkhouse

The Luminosity Function of X-Ray-selected Active Galactic Nuclei: Evolution of Supermassive Black Holes at High Redshift

We present a measure of the hard (2Y8 keV) X-ray luminosity function (XLF) of AGNs up to z � 5. At high redshifts, the wide area coverage of the Chandra Multiwavength Project is crucial to detect rare and luminous (LX > 10 44 ergs s � 1 ) AGNs. The inclusion of samples from deeper published surveys, such as the Chandra Deep Fields, allows us to span the lower LX range of the XLF. Our sample is selected from both the hard (z 6:3 ; 10 � 16 ergs cm � 2 s � 1 ) and soft (z > 3, f0:5Y2:0 keV > 1:0 ; 10 � 16 ergs cm � 2 s � 1 ) energy band detections. Within our optical magnitude limits (r 0 ; i 0 50%) regarding X-ray source identification (i.e., redshift). Wefind that the luminosity function is similar to that found in previous X-ray surveys up to z � 3 with an evolution dependent on both luminosity and redshift. At z > 3, there is a significant decline in the numbers of AGNs with an evolution rate similar to that found by studies of optically selected QSOs. Based on our XLF, we assess the resolved fraction of the cosmic X-ray background, the cumulative mass density of SMBHs, and the comparison of the mean accretion rate onto SMBHs and the star formation history of galaxies as a function of redshift. A coevolution scenario up to z � 2 is plausible, although at higher redshifts the accretion rate onto SMBHs drops more rapidly. Finally, we highlight the need for better statistics of high-redshift AGNs at zk3, which is achievable with the upcoming Chandra surveys. Subject headingg galaxies: active — quasars: general — surveys — X-rays: galaxies

THE COLOR-MAGNITUDE EFFECT IN EARLY-TYPE CLUSTER GALAXIES

We present the analysis of the color-magnitude relation (CMR) for a sample of 57 X-ray-detected Abell clusters within the redshift interval 0.02 ? z ? 0.18. We use the B - R versus R color-magnitude plane to establish that the CMR is present in all our low-redshift clusters and can be parameterized by a single straight line. We find that the CMRs for this large cluster sample of different richness and cluster types are consistent with having universal properties. The k-corrected colors of the individual CMRs in the sample at a fixed absolute magnitude have a small intrinsic dispersion of ~0.05 mag. The slope of the CMR is consistent with being the same for all clusters, with the variations entirely accountable by filter band shifting effects. We determine the mean of the dispersion of the 57 CMRs to be 0.074 mag, with a small rms scatter of 0.026 mag. However, a modest amount of the dispersion arises from photometric measurement errors and possible background cluster superpositions, and the derived mean dispersion is an upper limit. Models that explain the CMR in terms of metallicity and passive evolution can naturally reproduce the observed behavior of the CMR in this paper. The observed properties of the CMR are consistent with models in which the last episode of strong star formation in cluster early-type galaxies occurred significantly more than ~3 Gyr ago and the core set of early-type galaxies in clusters were formed more than 7 Gyr ago. The universality of the CMR provides us with an important tool for cluster detection and redshift estimation. A very accurate photometric cluster redshift estimator can be devised based on the apparent color shift of the CMR due to redshift. This calibrator has the additional advantage of being very efficient since only two bands are needed. An empirically calibrated redshift estimator based on the B - R color of the CMR for clusters with z < 0.20 produces an accuracy of ?z ~ 0.010. Background clusters, typically at z ~ 0.25 and previously unknown, are found in this survey in the color-magnitude diagrams as secondary CMRs to the red of the target cluster CMRs. We also find clear cases of apparent X-ray substructure that are due to these cluster superpositions. This suggests that X-ray observations of clusters are also subject to a significant amount of projection contaminations.

Chandra Multiwavelength Project X‐Ray Point Source Number Counts and the Cosmic X‐Ray Background

We present the Chandra Multiwavelength Project (ChaMP) X-ray point source number counts and cosmic X-ray background (CXRB) flux densities in multiple energy bands. From the ChaMP X-ray point source catalog, � 5500 sourcesare selected, covering 9.6deg 2 in sky area. To quantitativelycharacterize the sensitivity and completeness of the ChaMP sample, we perform extensive simulations. We also include the ChaMP+CDFs (Chandra Deep Fields) number counts to cover large flux ranges from 2 ;10 � 17 to 2:4 ; 10 � 12 (0.5Y2 keV) and from 2 ; 10 � 16 to 7:1 ; 10 � 12 (2Y8 keV) ergs cm � 2 s � 1 . The ChaMP and the ChaMP+CDFs differential number counts are well fitted with a broken power law. The best-fit faint and bright power indices are 1:49 � 0:02 and 2:36 � 0:05 (0.5Y2 keV), and 1:58 � 0:01 and 2:59 þ0:06 � 0:05 (2Y8 keV), respectively. We detect breaks in the differential number counts that appear at differentfluxes in different energybands. Assuming a single power-law model for asource spectrum,wefind that the same population(s) of soft X-ray sources causes the break in the differential number counts for all energy bands. We measure the resolved CXRB flux densities from the ChaMP and the ChaMP+CDFs number counts with and without bright target sources. ByaddingtheknownunresolvedCXRBtotheChaMP+CDFresolvedCXRB,wealsoestimate totalCXRBfluxdensities.Thefractionsof theresolvedCXRBwithouttargetsourcesare78% � 1%and81% � 2% in the 0.5Y2 and 2Y8 keV bands, respectively, somewhat lower than but generally consistent with earlier numbers because of their large errors. These fractions increase by � 1% when target sources are included. Subject headingg cosmology: observations — methods: data analysis — surveys — X-rays: diffuse background — X-rays: general

Probing the Balance of AGN and Star-Forming Activity in the Local Universe with ChaMP

The combination of the Sloan Digital Sky Survey (SDSS) and the Chandra Multiwavelength Project (ChaMP) currently offers the largest and most homogeneously selected sample of nearby galaxies for investigating the relation between X-ray nuclear emission, nebular line emission, black hole masses, and properties of the associated stellar populations. We provide X-ray spectral fits and valid uncertainties for all the galaxies with counts ranging from 2 to 1325 (mean 76, median 19). We present here novel constraints that both X-ray luminosity LX and X-ray spectral energy distribution bring to the galaxy evolutionary sequence H II → Seyfert/Transition Object → LINER → Passive suggested by optical data. In particular, we show that both LX and Γ, the slope of the power law that best fits the 0.5-8 keV spectra, are consistent with a clear decline in the accretion power along the sequence, corresponding to a softening of their spectra. This implies that, at z 0, or at low-luminosity active galactic nucleus (AGN) levels, there is an anticorrelation between Γ and L/L edd, opposite to the trend exhibited by high z AGN (quasars). The turning point in the Γ-L/L edd LLAGN + quasars relation occurs near Γ 1.5 and L/L edd 0.01. Interestingly, this is identical to what stellar mass X-ray binaries exhibit, indicating that we have probably found the first empirical evidence for an intrinsic switch in the accretion mode, from advection-dominated flows to standard (disk/corona) accretion modes in supermassive black hole accretors, similar to what has been seen and proposed to happen in stellar mass black hole systems. The anticorrelation we find between Γ and L/L edd may instead indicate that stronger accretion correlates with greater absorption. Therefore, the trend for softer spectra toward more luminous, high redshift, and strongly accreting (L/L edd 0.01) AGNs/quasars could simply be the result of strong selection biases reflected in the dearth of type 2 quasar detections.

A FULL YEAR'S CHANDRA EXPOSURE ON SLOAN DIGITAL SKY SURVEY QUASARS FROM THE CHANDRA MULTIWAVELENGTH PROJECT

We study the spectral energy distributions and evolution of a large sample of optically selected quasars from the Sloan Digital Sky Survey that were observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project. Our highest-confidence matched sample includes 1135 X-ray detected quasars in the redshift range 0.2 3, substantially expanding the known sample. We find no evidence for evolution out to z ~ 5 for either the X-ray photon index Γ or for the ratio of optical/UV to X-ray flux αox. About 10% of detected QSOs show best-fit intrinsic absorbing columns greater than 1022 cm–2, but the fraction might reach ~1/3 if most nondetections are absorbed. We confirm a significant correlation between αox and optical luminosity, but it flattens or disappears for fainter (MB –23) active galactic nucleus (AGN) alone. We report significant hardening of Γ both toward higher X-ray luminosity, and for relatively X-ray loud quasars. These trends may represent a relative increase in nonthermal X-ray emission, and our findings thereby strengthen analogies between Galactic black hole binaries and AGN. For uniformly selected subsamples of narrow-line Seyfert 1s and narrow absorption line QSOs, we find no evidence for unusual distributions of either αox or Γ.

The Luminosity Function of Low-Redshift Abell Galaxy Clusters

We present the results from a survey of 57 low-redshift Abell galaxy clusters to study the radial dependence of the luminosity function (LF). The dynamical radius of each cluster, -->r200, was estimated from the photometric measurement of cluster richness, Bgc. The shape of the LFs is found to correlate with radius such that the faint-end slope, α, is generally steeper on the cluster outskirts. The sum of two Schechter functions provides a more adequate fit to the composite LFs than a single Schechter function. LFs based on the selection of red and blue galaxies are bimodal in appearance. The red LFs are generally flat for – -->22 ≤ MRC ≤ − 18, with a radius-dependent steepening of α for -->MRC > − 18. The blue LFs contain a larger contribution from faint galaxies than the red LFs. The blue LFs have a rising faint-end component ( -->α ~ − 1.7) for -->MRC > − 21, with a weaker dependence on radius than the red LFs. The dispersion of -->M* was determined to be 0.31 mag, which is comparable to the median measurement uncertainty of 0.38 mag. This suggests that the bright end of the LF is universal in shape at the 0.3 mag level. We find that -->M* is not correlated with cluster richness when using a common dynamical radius. Also, we find that -->M* is weakly correlated with BM type such that later BM-type clusters have a brighter -->M*. A correlation between -->M* and radius was found for the red and blue galaxies such that -->M* fades toward the cluster center.

ChaMP Serendipitous Galaxy Cluster Survey

We present a survey of serendipitous extended X-ray sources and optical cluster candidates from the Chandra Multiwavelength Project (ChaMP). Our main goal is to make an unbiased comparison of X-ray and optical cluster detection methods. In 130 archival Chandra pointings covering 13 deg 2 , we use a wavelet decomposition technique to detect 55 extended sources, of which 6 are nearby single galaxies. Our X-ray cluster catalog reaches a typical flux limit of about � 10 � 14 ergs cm � 2 s � 1 , with a median cluster core radius of 21 00 . For 56 of the 130 X-ray fields, we use the ChaMP’s deep NOAO 4 m MOSAIC g 0 , r 0 , and i 0 imaging to independently detect cluster candidates using a Voronoi tessellation and percolation (VTP) method. Red-sequence filtering decreases the galaxy fore- and background contamination and provides photometric redshifts to z � 0:7. From the overlapping 6.1 deg 2 X-ray/optical imaging, wefind115opticalclusters (ofwhich11%areintheX-raycatalog)and28X-rayclusters(ofwhich46%are in the optical VTP catalog). The median redshift of the 13 X-ray/optical clusters is 0.41, and their median X-ray luminosity (0.5‐2 keV) is LX ¼ 2:65 � 0:19 ðÞ ; 10 43 ergs s � 1 . The clusters in our sample that are only detected in our optical data are poorer on average (� 4 � ) than the X-ray/optically matched clusters, which may partially explain the difference in the detection fractions. Subject headingg galaxies: clusters: general — surveys — X-rays: galaxies: clusters

The Dark Energy Survey Data Management System

The Dark Energy Survey (DES) collaboration will study cosmic acceleration with a 5000 deg2 griZY survey in the southern sky over 525 nights from 2011-2016. The DES data management (DESDM) system will be used to process and archive these data and the resulting science ready data products. The DESDM system consists of an integrated archive, a processing framework, an ensemble of astronomy codes and a data access framework. We are developing the DESDM system for operation in the high performance computing (HPC) environments at the National Center for Supercomputing Applications (NCSA) and Fermilab. Operating the DESDM system in an HPC environment offers both speed and flexibility. We will employ it for our regular nightly processing needs, and for more compute-intensive tasks such as large scale image coaddition campaigns, extraction of weak lensing shear from the full survey dataset, and massive seasonal reprocessing of the DES data. Data products will be available to the Collaboration and later to the public through a virtual-observatory compatible web portal. Our approach leverages investments in publicly available HPC systems, greatly reducing hardware and maintenance costs to the project, which must deploy and maintain only the storage, database platforms and orchestration and web portal nodes that are specific to DESDM. In Fall 2007, we tested the current DESDM system on both simulated and real survey data. We used Teragrid to process 10 simulated DES nights (3TB of raw data), ingesting and calibrating approximately 250 million objects into the DES Archive database. We also used DESDM to process and calibrate over 50 nights of survey data acquired with the Mosaic2 camera. Comparison to truth tables in the case of the simulated data and internal crosschecks in the case of the real data indicate that astrometric and photometric data quality is excellent.

The Chandra Multi-wavelength Project: Optical Spectroscopy and the Broadband Spectral Energy Distributions of X-Ray-selected AGNs.

From optical spectroscopy of X-ray sources observed as part of the Chandra Multi-wavelength Project (ChaMP), we present redshifts and classifications for a total of 1569 Chandra sources from our targeted spectroscopic follow-up using the FLWO/1.5 m, SAAO/1.9 m, WIYN 3.5 m, CTIO/4 m, KPNO/4 m, Magellan/6.5 m, MMT/6.5 m, and Gemini/8 m telescopes, and from archival Sloan Digital Sky Survey (SDSS) spectroscopy. We classify the optical counterparts as 50% broad-line active galactic nuclei (AGNs), 16% emission line galaxies, 14% absorption line galaxies, and 20% stars. We detect QSOs out to z ~ 5.5 and galaxies out to z ~ 3. We have compiled extensive photometry, including X-ray (ChaMP), ultraviolet (GALEX), optical (SDSS and ChaMP-NOAO/MOSAIC follow-up), near-infrared (UKIDSS, Two Micron All Sky Survey, and ChaMP-CTIO/ISPI follow-up), mid-infrared (WISE), and radio (FIRST and NVSS) bands. Together with our spectroscopic information, this enables us to derive detailed spectral energy distributions (SEDs) for our extragalactic sources. We fit a variety of template SEDs to determine bolometric luminosities, and to constrain AGNs and starburst components where both are present. While ~58% of X-ray Seyferts (1042 erg s–1 5% starburst contribution to bolometric luminosity) to fit observed photometry only 26% of the X-ray QSO (L 2 – 10 keV >1044 erg s–1) population appear to have some kind of star formation contribution. This is significantly lower than for the Seyferts, especially if we take into account torus contamination at z > 1 where the majority of our X-ray QSOs lie. In addition, we observe a rapid drop of the percentage of starburst contribution as X-ray luminosity increases. This is consistent with the quenching of star formation by powerful QSOs, as predicted by the merger model, or with a time lag between the peak of star formation and QSO activity. We have tested the hypothesis that there should be a strong connection between X-ray obscuration and star formation but we do not find any association between X-ray column density and star formation rate both in the general population or the star-forming X-ray Seyferts. Our large compilation also allows us to report here the identification of 81 X-ray Bright Optically inactive Galaxies, 78 z > 3 X-ray sources, and eight Type-2 QSO candidates. Also, we have identified the highest redshift (z = 5.4135) X-ray-selected QSO with optical spectroscopy.

Chandra multiwavelength project: normal galaxies at intermediate redshift

We investigate Chandra extragalactic sources, including galaxies with narrow emission line (NELG) and absorption line galaxies (ALG), but excluding broad emission line AGNs and quasars. Based on f_{X}/f_{O}, L_{X}, X-ray spectral hardness and optical emission line diagnostics, we have conservatively classified normal galaxies. With our ChaMP galaxy sample (extended to include 6 years of Chandra data) and additional normal galaxies found in other X-ray surveys, we discuss their L_{X}/L_{B} evolution, log(N)-log(S) relationship, off-nucleus ULXs, XBONGs, and E+A galaxies.