Signs of gas flows in the variable Balmer line profiles of the Seyfert galaxy nuclei NGC 3227 and NGC 7469

Crimean Astrophysical Observatory and Isaac Newton Institute of Chile, Crimean Branch, 98409 Nauchny, Crimea, Ukraine e-mail: ipronik@crao.crimea.ua

Received: 2 December 2007
Accepted: 10 October 2008

Abstract

The data on the variable Balmer line profiles obtained by us for the Seyfert galaxy NGC 3227 and NGC 7469 nuclei and published separately during 1975–2006, were combined with the data compiled from literature, and reviewed in this paper. We hypothesize that the profile variations are connected with three independent regions of different physical conditions: 1) Classical broad line region (BLR) of size ~4.5 10¹⁶ cm is ionized and excited by the central source radiation. The central source brightness variations in 1971–1972 produced gas parameter variations of 10⁹ cm^-3 10⁸ cm^-3 and 2 10⁴ K  4 10⁴ K. 2) The profiles of the Balmer lines contain narrow components that have retained their positions (radial velocities) over 25 and 17 years in NGC 3227 and NGC 7469, respectively. These components are supposed to be caused by long-lived gas flows in the nuclei of the galaxies. Observational data acquired by Rubin and Ford allow us to assume that gas in the flows can be explained by models of collision ionization and excitation of gas with self-absorption. It is dense and hot plasma with n_e = 10⁸–10¹² cm^-3 and T_e = (1-2.5) 10⁴ K. 3) Broad blue bumps of radial velocities between –4000 km s^-1 and –5000 km s^-1 were detected in the Hγ profile during a several day flare twice in NGC 3227 nucleus and once in NGC 7469. One can speculate that the flares are connected with short-lived ejections. The gas in the ejections was ionized and excited by collision processes with n_e ~ 10¹⁴ cm^-3 and T_e ~ 25 000 K.