Volume 420, Number 3, June IV 2004
|Page(s)||905 - 910|
|Published online||04 June 2004|
XMM-Newton observations of the dwarf elliptical galaxy NGC 3226
Research and Scientific Support Department, European Space Agency - Postbus 299, 2200 AG Noordwijk, The Netherlands
Accepted: 22 March 2004
We report on an XMM-Newton observation of the dwarf elliptical galaxy NGC 3226 performed in November 2000. The analysis of the 0.4–10 keV spectrum of its nucleus is consistent with a power law continuum ( 1.96) absorbed at low energies by neutral gas (with a hydrogen column density – cm-2 and a covering fraction greater than 85%) and by weakly ionized gas (– cm-2 with –7 erg s-1 cm). However, the study indicates that a bremstrahlung model absorbed by neutral material is a better description reminiscent of the X-ray emission from advection-dominated accretion flows (ADAFs). The temperature of the best fit bremstrahlung model ( K) and the absence of short and mid time-scale variability suggests that the X-ray emission originates from regions relatively far from the nucleus as in convection-dominated accretion flows (CDAFs) or in the so-called “wind” models. By comparing the 2–10 keV luminosity of the central object ( erg s-1 after correction from Galactic and intrinsic absorption) with radio flux measurements, we find a mass in the range (1.7– for the accreting black hole, a value comparable with an independent estimate from the dispersion of radial velocities. We argue that the dwarf elliptical galaxy NGC 3226 may harbor a sub-Eddington, super-massive black hole in a radiative inefficient state which is distinct from the near-Eddington, thermally dominated black holes presumably found in quasars and luminous Seyfert galaxies.
Key words: X-rays: individual: NGC 3226 / galaxies: nuclei / galaxies: elliptical and lenticular, cD / X-rays: galaxies
© ESO, 2004
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.