Showing papers by "Daniel R. Wik published in 2012"

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

Abstract: 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.

The Chandra Multi-Wavelength Project: Optical Spectroscopy and the Broadband Spectral Energy Distributions of X-ray Selected AGN

Abstract: From optical spectroscopy of X-ray sources observed as part of ChaMP, we present redshifts and classifications for a total of 1569 Chandra sources from our targeted spectroscopic follow up using the FLWO, SAAO, WIYN, CTIO, KPNO, Magellan, MMT and Gemini telescopes, and from archival SDSS spectroscopy. We classify the optical counterparts as 50% BLAGN, 16% NELG, 14% ALG, and 20% stars. We detect QSOs out to z~5.5 and galaxies out to z~3. We have compiled extensive photometry from X-ray to radio bands. Together with our spectroscopic information, this enables us to derive detailed SEDs for our extragalactic sources. We fit a variety of templates to determine bolometric luminosities, and to constrain AGN and starburst components where both are present. While ~58% of X-ray Seyferts require a starburst event to fit observed photometry only 26% of the X-ray QSO 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 XBONG, 78 z>3 X-ray sources and 8 Type-2 QSO candidates. Also we have identified the highest redshift (z=5.4135) X-ray selected QSO with optical spectroscopy.

THE CHANDRA MULTI-WAVELENGTH PROJECT: OPTICAL SPECTROSCOPY AND THE BROADBAND SPECTRAL ENERGY DISTRIBUTIONS OF X-RAY-SELECTED AGNs

Abstract: 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 (10^(42) erg s^(–1) 5% starburst contribution to bolometric luminosity) to fit observed photometry only 26% of the X-ray QSO (L_(2 – 10 keV) >10^(44) 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.

The swift burst alert telescope perspective on non-thermal emission in hiflugcs galaxy clusters

Abstract: The search for diffuse non-thermal, inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been underway for many years, with most detections being either of low significance or controversial. In this work, we investigate 14-195 keV spectra from the Swift Burst Alert Telescope (BAT) all-sky survey for evidence of non-thermal excess emission above the exponentially decreasing tail of thermal emission in the flux-limited HIFLUGCS sample. To account for the thermal contribution at BAT energies, XMM-Newton EPIC spectra are extracted from coincident spatial regions so that both thermal and non-thermal spectral components can be determined simultaneously. We find marginally significant IC components in six clusters, though after closer inspection and consideration of systematic errors we are unable to claim a clear detection in any of them. The spectra of all clusters are also summed to enhance a cumulative non-thermal signal not quite detectable in individual clusters. After constructing a model based on single-temperature fits to the XMM-Newton data alone, we see no significant excess emission above that predicted by the thermal model determined at soft energies. This result also holds for the summed spectra of various subgroups, except for the subsample of clusters with diffuse radio emission. Formore » clusters hosting a diffuse radio halo, a relic, or a mini-halo, non-thermal emission is initially detected at the {approx}5{sigma} confidence level-driven by clusters with mini-halos-but modeling and systematic uncertainties ultimately degrade this significance. In individual clusters, the non-thermal pressure of relativistic electrons is limited to {approx}< 10% of the thermal electron pressure, with stricter limits for the more massive clusters, indicating that these electrons are likely not dynamically important in the central regions of clusters.« less

Merger Shocks in Abell 3667 and the Cygnus~A Cluster

Abstract: We present new XMM-Newton observations of the northwest (NW) radio relic region in the cluster Abell 3667. We detect a jump in the X-ray surface brightness and X-ray temperature at the sharp outer edge of the radio relic which indicate that this is the location of a merger shock with a Mach number of about 2. Comparing the radio emission to the shock properties implies that approximately 0.2% of the dissipated shock kinetic energy goes into accelerating relativistic electrons. This is an order of magnitude smaller than the efficiency of shock acceleration in many Galactic supernova remnants, which may be due to the lower Mach numbers of cluster merger shocks. The X-ray and radio properties indicate that the magnetic field strength in the radio relic is >= 3 muG, which is a very large field at a projected distance of ~2.2 Mpc from the center of a cluster. The radio spectrum is relatively flat at the shock, and steepens dramatically with distance behind the shock. This is consistent with radiative losses by the electrons and the post-shock speed determined from the X-ray properties. The Cygnus A radio source is located in a merging cluster of galaxies. This appears to be an early-stage merger. Our recent Suzaku observation confirm the presence of a hot region between the two subclusters which agrees with the predicted shocked region. The high spectral resolution of the CCDs on Suzaku allowed us to measure the radial component of the merger velocity, Delta v_r \approx 2650 km/s.