The Ultra Luminous Infrared Galaxy Mrk 231: new clues from BeppoSAX and XMM-Newton

Abstract. Based on recent work on spectral decomposition of the emission of star-forming galaxies, we assess whether the integrated 2−10 keV emission from high-mass X-ray binaries (HMXBs), L HMXB 2−10 , 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 2−10 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 2−10 relation. The SFR -L HMXB 2−10 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, and are therefore likely to hide strongly absorbed AGNs.

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

Peršić

Rephaeli

Braito

et al. 2004

A&A

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113

183

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The Nuclear Gas Dynamics and Star Formation of Markarian 231

Davies¹,

Tacconi²,

Genzel³

2004

ApJ

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We report adaptive optics H- and K-band spectroscopy of the inner few arcsec of the luminous merger/ULIRG/QSO Mkn231, at spatial resolutions as small as 0.085". For the first time we have been able to resolve the active star forming region close to the AGN using stellar absorption features, finding that its luminosity profile is well represented by an exponential function with a disk scale length 0.18-0.24" (150-200pc), and implying that the stars exist in a disk rather than a spheroid. The stars in this region are also young (10-100Myr), and it therefore seems likely that they have formed in situ in the gas disk, which itself resulted from the merger. The value of the stellar velocity dispersion is a result of the large mass surface density of the disk. The stars in this region have a combined mass of at least 1.6x10^9M_sun, and account for 25-40% of the bolometric luminosity of the entire galaxy. We have detected the 2.12um 1-0S(1) H_2 and 1.64um [FeII] lines out to radii exceeding 0.5". The kinematics for the two lines are very similar to each other as well as to the stellar kinematics, and broadly consistent with the nearly face-on rotating disk reported in the literature and based on interferometric CO1-0 and CO2-1 measurements of the cold gas. However, they suggest a more complex situation in which the inner 0.2-0.3" (200pc) is warped out of its original disk plane. Such a scenario is supported by other observations.Comment: accepted for publication in ApJ; abstract given here is slightly shortene

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Active Galactic Nucleus and Starburst Classification fromSpitzerMid‐Infrared Spectra for High‐Redshift SWIRE Sources

Weedman

Polletta

Lonsdale

et al. 2006

ApJ

125

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Spectra have been obtained with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope for 20 sources in the Lockman Hole field of the SWIRE survey. The sample is divided between sources with indicators of an obscured AGN, based primarily on X-ray detections of optically-faint sources, and sources with indicators of a starburst, based on optical and near-infrared spectral energy distributions (SEDs) which show a luminosity peak from stellar photospheric emission. Ten of the 11 AGN sources have IRS spectra which show silicate absorption or are power laws; only one AGN source shows PAH emission features. All 9 of the sources showing starburst SEDs in the near-infrared show PAH emission features in the IRS spectra. Redshifts are determined from the IRS spectra for all 9 starbursts (1.0 < z < 1.9) and 8 of the 11 AGN (0.6 < z < 2.5). Classification as AGN because of an X-ray detection, the classification as AGN or starburst derived from the photometric SED, and the IRS spectroscopic classification as AGN (silicate absorption) or starburst (PAH emission) are all consistent in 18 of 20 sources. The surface density for starbursts which are most luminous in the mid-infrared is less than that for the most luminous AGN within the redshift interval 1.7 z 1.9. This result implies that mid-infrared source counts at high redshift are dominated by AGN for f ν (24µm) 1.0 mJy.

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The Ultra Luminous Infrared Galaxy Mrk 231: new clues from BeppoSAX and XMM-Newton

Cited by 3 publications

References 13 publications

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

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

The Nuclear Gas Dynamics and Star Formation of Markarian 231

Active Galactic Nucleus and Starburst Classification fromSpitzerMid‐Infrared Spectra for High‐Redshift SWIRE Sources

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