Spectroscopy monitoring of active galactic nuclei from CTIO. I. NGC 3227

Abstract

The results of a five-month monitoring campaign on the Seyfert 1.5 galaxy NGC 3227 are presented. Variability was detected in the continuum and in the broad emission lines. Cross correlations of the 4200 Å continuum light curve with the Hβ and He II λ4686 emission-line light curves indicate delays of 18 ± 5 and 16 ± 2 days, respectively, between the continuum variations and the response of the lines. We apply a maximum entropy method to solve for the transfer function that relates the Hβ and He II λ4686 lines and 4200 Å continuum variability and the result of this analysis suggests that there is a deficit of emission-line response due to gas along the line of sight to the continuum source for both lines. Using a composite off-nuclear spectrum, we synthesize the bulge stellar population, which is found to be mainly old (77% with age > 10 Gyr) with a metallicity twice the solar value. The synthesis also yields an internal color excess E(B−V) ≈0.04. The mean contribution of the stellar population to the inner 5" x 10" spectra during the campaign was ~40% .