EDP Sciences
Free access
Volume 432, Number 2, March III 2005
Page(s) 463 - 466
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20041717

A&A 432, 463-466 (2005)
DOI: 10.1051/0004-6361:20041717

Black hole growth by accretion

S. Mathur and D. Grupe

Astronomy Department, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA
    e-mail: smita@astronomy.ohio-state.edu

(Received 22 July 2004 / Accepted 9 November 2004)

We show that black holes grow substantially by accretion at close to Eddington rates. Using a complete sample of soft X-ray selected AGNs, Grupe & Mathur (2004, ApJ, 606, L41) have shown that narrow line Seyfert 1 galaxies, as a class, lie below the $M_{\rm BH}$-$\sigma$ relation of normal galaxies. Some NLS1s, however, lie on or close to the $M_{\rm BH}$-$\sigma$ relation. Here we show that not all NLS1s accrete at close to Eddington rates: those with low ${L/L_{\rm Eddington}}$ are close to the $M_{\rm BH}$-$\sigma$ relation, and those with high ${L/L_{\rm Eddington}}$ are far from it. With various tests in this paper, we argue that black holes grow in mass substantially in their high-accretion phase and approach the $M_{\rm BH}$-$\sigma$ relation over time. The mass growth in a low accretion phase, as in BLS1s and also in some NLS1s, appears to be insignificant. Any theoretical model attempting to explain the $M_{\rm BH}$-$\sigma$ relation needs to explain the above observations.

Key words: black hole physics -- galaxies: active -- galaxies: evolution -- X-rays: galaxies

© ESO 2005

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