Volume 393, Number 3, October III 2002
|Page(s)||793 - 807|
|Section||Cosmology (including clusters of galaxies)|
|Published online||01 October 2002|
Constraining the past X-ray luminosity of AGN in clusters of galaxies: The role of resonant scattering
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85740 Garching bei München, Germany
2 Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, 117997 Moscow, Russia
Corresponding author: S. Yu. Sazonov, firstname.lastname@example.org
Accepted: 28 June 2002
Only a small fraction of galactic nuclei in the nearby universe are luminous; most of them are currently dim. We investigate the feasibility of constraining the X-ray luminosity in the recent past (up to ∼106 years ago) of the nucleus of a cluster dominant galaxy by measuring the contribution of scattered radiation from the central source to the surface brightness of the intracluster gas dominated by thermal emission. We show that resonance X-ray lines present an advantage over the adjacent continuum, because the relative contribution of the scattered component is typically larger in the line case by a significant factor of 3–10. As an example, we estimate the level of constraint that could be derived from future fine spectroscopic observations on the past X-ray luminosity of the nearby M 87 and Cygnus A active galaxies. For instance, scattered line radiation should be detectable from the Virgo cluster if the X-ray luminosity of M 87 was a few times 1044 erg s-1, or 10-3 of its Eddington luminosity, until a few times 105 years ago. For comparison, upper limits inferred from the available XMM-Newton and Chandra X-ray continuum data are typically 1–2 orders of magnitude weaker. The same method can be applied to distant powerful quasars (at redshifts ) if they have cluster-like gaseous coronae, as suggested by Rosat and Chandra observations of active galaxies at . Their surface brightness profiles in the X-ray continuum above ∼10 keV (where T is the gas temperature) should be dominated by redshifted scattered radiation from the quasar. Therefore, measurements with forthcoming mirror-optics hard X-ray telescopes could give information on the lifetime of quasars and parameters of the hot gas around them.
Key words: galaxies: active / galaxies: quasars: general / scattering / X-rays: galaxies: clusters
© ESO, 2002
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.