A Comprehensive Study of 2000 Narrow Line Seyfert 1 Galaxies from the Sloan Digital Sky Survey. I. The Sample

Abstract

This is the first paper in a series dedicated to the study of the emission-line and continuum properties of narrow line Seyfert 1 galaxies (NLS1s). We carried out a systematic search for NLS1s from objects assigned as "QSOs" or "galaxies" in the spectroscopic sample of the Sloan Digital Sky Survey Data Release 3 (SDSS DR3) by a careful modeling of their emission lines and continua. The result is a uniform sample comprising ∼ 2 000 NLS1. This sample dramatically increases the number of known NLS1 by a factor of ∼ 10 over previous compilations. This paper presents the parameters of the prominent emission lines and continua, which were measured accurately with typical uncertainties < 10%. Taking advantage of such an unprecedented large and uniform sample with accurately measured spectral parameters, we carried out various statistical analysis, some of which were only possible for the first time. The main results found are as follows.(1) Within the overall Seyfert 1 population, the incidence of NLS1s is strongly dependent on the optical, X-ray, and radio luminosities as well as the radioloudness. The fraction of NLS1 peaks around SDSS g-band absolute magnitude M g ∼ −22 m in the optical and ∼ 10 43.2 erg s −1 in the soft X-ray band, and decreases quickly as the radio-loudness increases. (2) On average the relative FeII emission, R 4570 = F eII(4434 − 4684)/Hβ, in NLS1s is about twice that in normal AGNs, and is anti-correlated with the broad component width of the Balmer emission lines. (3) The well-known anti-correlation between the width of broad low-ionization lines and the soft X-ray spectral slope for broad line AGNs extends down to F W HM ∼ 1 000 km s −1 in NLS1s, but the trend appears to

GTC spectra ofz≈ 2.3 quasars: comparison with local luminosity analogs

“…Figure 1 illustrates the observational situation by plotting the distribution of a representative SDSS quasar subsample (Schneider et al 2010) in the z − B absolute magnitude plane. Note that only sources listed as quasars in the Schneider et al (2010) catalogs are shown, so that a large population of local active galactic nuclei (AGN; Koehler et al 1997) and AGN with the narrowest broad lines (FWHM < 1000 km s −1 ; Zhou et al 2006) are not shown in the lower part of the plot. The low-z yellow box identifies a range of absolute magnitudes where quasars are rare in the local Universe (they would be easily detected, but they do not exist in large numbers) and belong to the high-luminosity tail of the optical luminosity function (Cheng et al 1985;Grazian et al 2000;Richards et al 2005).…”

Past and present secular evolution in the host galaxies of NLS1s

“…Trends and correlations have been identified using, first, small samples and, later, corroborated by larger surveys (e.g. [32,33]). Many scenarios have been considered to explain these properties.…”

“…[2,11] and reference therein) and low black hole masses (typically of order 10 6 M , e.g. [1,33,28]). While these scenarios can elucidate the nuclear properties of NLS1s, they hardly explain the origin of the fundamental differences between NLS1s and BLS1s and, in particular, that NLS1s appear to be more than just Seyfert 1s with narrow lines.…”

Narrow-Line Seyfert 1s: a luminosity dependent definition

“…A sample of very narrow NLSy1s (blue triangles; Zhou et al [24]) is also shown. The dot-dashed lines indicate the limits for NLSy1s (magenta) and for Pop.…”