Black hole growth by accretion
Astronomy Department, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA e-mail: email@example.com
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 MBH–σ relation of normal galaxies. Some NLS1s, however, lie on or close to the MBH–σ relation. Here we show that not all NLS1s accrete at close to Eddington rates: those with low are close to the MBH–σ relation, and those with high 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 MBH–σ 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 MBH–σ relation needs to explain the above observations.
Key words: black hole physics / galaxies: active / galaxies: evolution / X-rays: galaxies
© ESO, 2005