Broad - Broad-Line Region. The lines arising here include...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Broad-Line Region . The lines arising here include hydrogen and helium recombination lines, permitted and semi-forbidden lines such as C IV and [C III (most of these in the emitted UV), and complex multiplets of Fe II. The lack of other lines suggests densities in excess of 10 7 cm -3 , and some considerations suggest values as high as 10 11 . At these densities, recombination is a very efficient radiator; a typical BLR requires only 10 6 solar masses. The size scale is taken from variability (see below), at as little as a light-week. Line ratios require that the emitting regions be optically thick and heavily stratified - the best bet is again one of fairly discrete individual clouds. One face will be directly illuminated by the ionizing continuum source, with hard radiation penetrating farther into the cloud. A warm, partially ionized zone deep inside the clouds is indicated for heavy-element emission. There will be a skin all around the cloud ionized by reflected UV from other clouds. The number of BLR clouds has been estimated ( > 10
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/10/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.

Ask a homework question - tutors are online