Based on recent work on spectral decomposition of the emission of star-forming galaxies, we assess whether the inte- grated 2−10 keV emission from high-mass X-ray binaries (HMXBs), L HMXB−10 , can be used as a reliable estimator of ongoing star formation rate (SFR). Using a sample of 46 local (z < 0.1) star-forming galaxies, and spectral modeling of ASCA, BeppoSAX, and XMM-Newton data, we demonstrate the existence of a linear SFR -L HMXB−10 relation which holds over ∼5 decades in X-ray luminosity and SFR. The total 2−10 keV luminosity is not a precise SFR indicator because at low SFR (i.e., in normal and moderately-starbursting galaxies) it is substantially affected by the emission of low-mass X-ray binaries, which do not trace the current SFR due to their long evolution lifetimes, while at very high SFR (i.e., for very luminous FIR-selected galaxies) it is frequently affected by the presence of strongly obscured AGNs. The availability of purely SB-powered galaxies - whose 2−10 keV emission is mainly due to HMXBs - allows us to properly calibrate the SFR -L HMXB−10 relation. The SFR -L HMXB−10 relation holds also for distant (z ∼ 1) galaxies in the Hubble Deep Field North sample, for which we lack spectral information, but whose SFR can be estimated from deep radio data. If confirmed by more detailed observations, it may be possible to use the deduced relation to identify distant galaxies that are X-ray overluminous for their (independently estimated) SFR ,a nd are therefore likely to hide strongly absorbed AGNs.

/pdf/2-10-kev-luminosity-of-high-mass-binaries-as-a-gauge-of-zq06rbj0ax.pdf

2-10 KeV luminosity of high - mass binaries as a gauge of ongoing star - formation rate

We present the results of a Suzaku monitoring campaign of the Seyfert 2 galaxy, NGC 7582. The source is characterized by very rapid (on timescales even lower than a day) changes of the column density of an inner absorber, together with the presence of constant components arising as reprocessing from a Compton-thick material. The best-fitting scenario implies important modifications to the zeroth-order view of Unified Models. While the existence of a pc-scale torus is needed in order to produce a constant Compton reflection component and an iron Kα-emission line, in this Seyfert 2 galaxy this is not viewed along the line of sight. On the other hand, the absorption of the primary continuum is due to another material, much closer to the black hole, roughly at the distance of the broad-line region, which can produce the observed rapid spectral variability. On top of that, the constant presence of a 1022 cm–2 column density can be ascribed to the presence of a dust lane, extended on a galactic scale, as previously confirmed by Chandra. There is now mounting evidence that complexity in the obscuration of active galactic nuclei (AGNs) may be the rule rather than the exception. We therefore propose to modify the Unification Model, adding to the torus the presence of two further absorbers/emitters. Their combination along the line of sight can reproduce all the observed phenomenology.

How Complex is the Obscuration in Active Galactic Nuclei? New Clues from the Suzaku Monitoring of the X-Ray Absorbers in NGC 7582

We present a catalog of 792 Fifth Data Release Sloan Digital Sky Survey quasars with optical spectra that have been observed serendipitously in the X-rays with the XMM-Newton. These quasars cover a redshift range of z = 0.11-5.41 and a magnitude range of i = 15.3-20.7. Substantial numbers of radio-loud (70) and broad absorption line (51) quasars exist within this sample. Significant X-ray detections at ≥2σ account for 87% of the sample (685 quasars), and 473 quasars are detected at ≥6σ, sufficient to allow X-ray spectral fits. For detected sources, ~60% have X-ray fluxes between F 2–10 keV = (1-10) ×10–14 erg cm–2 s–1. We fit a single power law, a fixed power law with intrinsic absorption left free to vary, and an absorbed power-law model to all quasars with X-ray signal-to-noise ratio ≥ 6, resulting in a weighted mean photon index Γ = 1.91 ± 0.08, with an intrinsic dispersion σΓ = 0.38. For the 55 sources (11.6%) that prefer intrinsic absorption, we find a weighted mean NH = 1.5 ± 0.3 × 1021 cm–2. We find that Γ correlates significantly with optical color, Δ(g – i), the optical-to-X-ray spectral index (αox), and the X-ray luminosity. While the first two correlations can be explained as artifacts of undetected intrinsic absorption, the correlation between Γ and X-ray luminosity appears to be a real physical correlation, indicating a pivot in the X-ray slope.

/pdf/the-fifth-data-release-sloan-digital-sky-survey-xmm-newton-3e5t4jn8h9.pdf

The fifth data release sloan digital sky survey/xmm-newton quasar survey

We present new mid-infrared (N-band) images of a sample of eight nearby Seyfert galaxies. In all of our targets, we detect a central unresolved source, which in some cases has been identified for the first time. In particular, we have detected the mid-infrared emission from the active nucleus of NGC 4945, which previously remained undetected at any wavelength but hard X-rays. We also detect circumnuclear extended emission in the Circinus galaxy along its major axis, and find marginal evidence for extended circumnuclear emission in NGC 3281. 
The high spatial resolution (1.7") of our data allows us to separate the flux of the nuclear point sources from the extended circumnuclear starburst (if present). We complement our sample with literature data for a number of non-active starburst galaxies, and relate the nuclear N-band flux to published hard (2-10 kev) X-ray fluxes. We find tight and well-separated correlations between nuclear N-band flux and X-ray flux for both Seyfert and starburst nuclei which span over 3 orders of magnitude in luminosity. We demonstrate that these correlations can be used as a powerful classification tool for galactic nuclei. 
For example, we find strong evidence against NGC 1808 currently harbouring an active Seyfert nucleus based on its position in the mid-infrared-X-ray diagram. On the other hand, we confirm that NGC 4945 is in fact a Seyfert 2 galaxy.

N-band Imaging of Seyfert Nuclei and the MIR-X-ray correlation

We present a catalog of 792 DR5 SDSS quasars with optical spectra that have been observed serendipitously in the X-rays with the \emph{XMM-Newton}. These quasars cover a redshift range of z = 0.11 - 5.41 and a magnitude range of i = 15.3-20.7. Substantial numbers of radio-loud (70) and broad absorption line (51) quasars exist within this sample. Significant X-ray detections at >2sigma account for 87% of the sample (685 quasars), and 473 quasars are detected at >6sigma, sufficient to allow X-ray spectral fits. For detected sources, ~ 60% have X-ray fluxes between F(2-10 keV) = 1 - 10 x 10^-14 ergs cm^-2 s^-1. We fit a single power-law, a fixed power-law with intrinsic absorption left free to vary, and an absorbed power-law model to all quasars with X-ray S/N > 6, resulting in a weighted mean photon index Gamma = 1.91 +/- 0.08, with an intrinsic dispersion sigma_Gamma = 0.38. For the 55 sources (11.6%) that prefer intrinsic absorption, we find a weighted mean N_H = 1.5 +/- 0.3 x 10^21 cm^-2. We find that Gamma correlates significantly with optical color, Delta(g-i), the optical-to-X-ray spectral index (alpha_ox) and the X-ray luminosity. While the first two correlations can be explained as artefacts of undetected intrinsic absorption, the correlation between Gamma and X-ray luminosity appears to be a real physical correlation, indicating a pivot in the X-ray slope.

/pdf/the-fifth-data-release-sloan-digital-sky-survey-xmm-newton-4pkpqgv7w0.pdf

The Fifth Data Release Sloan Digital Sky Survey/XMM-Newton Quasar Survey

Observations with the Imaging Proportional Counter reveal that three of the four galaxies in the Grus Quartet are X-ray emitters (NGC 7552, 7582, 7590). The strongest is the narrow emission line galaxy (NELG) NGC 7582, and we confirm, also using data from the Monitor Proportional Counter, that the variable 2A 2315--428 consists essentially of this galaxy only. In the spectrum of this galaxy evidence is found of a large photoelectric cutoff, with the corresponding N/sub H/ lying between 5 and 10 x 10/sup 22/ cm/sup -2/. It is shown that both the interstellar medium and the narrow emission line gas of this galaxy are unlikely to be the main causes of the cutoff. By analogy with NGC 4151, where the variable cutoff is attributed to the broad line emitting gas, N/sub H/ is found to be compatible with the upper limits that can be placed on the strength of broad line components in NGC 7582 and could therefore represent the first indirect evidence of very high velocity gas in the nuclei of NELGs. A crucial test to be pursued is time variability in the cutoff.

X-ray observations of NGC 7582 and the Grus Quartet with the Einstein Observatory

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X-ray observations of NGC 7582 and the Grus Quartet with the Einstein Observatory