Xiao-Bo Dong

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

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 similar to 2000 NLS1s. This sample dramatically increases the number of known NLS1s by a factor of similar to 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 analyses, 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 radio loudness. The fraction of NLS1s peaks around SDSS g-band absolute magnitude M-g similar to -22 mag in the optical and similar to 10(43.2) ergs s(-1) in the soft X-ray band, and decreases quickly as the radio loudness increases. (2) On average the relative Fe II emission, R-4570 = Fe II lambda lambda 4434-4684/H beta, in NLS1s is about twice that in normal active galactic nuclei (AGNs) and is anticorrelated with the broad component width of the Balmer emission lines. (3) The well-known anticorrelation between the width of broad low-ionization lines and the soft X-ray spectral slope for broad line AGNs extends down to FWHM similar to 1000 km s(-1) in NLS1s, but the trend appears to reverse at still smaller line widths. (4) The equivalent width of H beta and Fe II emission lines are strongly correlated with the H beta and continuum luminosities. (5) We do not find any difference between NLS1s and normal AGNs in regard to the narrow line region. (6) We have examined the black hole mass versus stellar velocity dispersion (M-BH-sigma(*)) relation for a subsample of 308 NLS1s for which sigma(*) could be measured directly from fitting the starlight in the SDSS spectra with our stellar spectral templates. A significant correlation between M-BH and sigma(*) is found, but with the bulk of black hole masses falling below the values expected from the M-BH-sigma(*) relation for normal galaxies and normal AGNs. This result indicates that NLS1s are underage AGNs, where the growth of the SMBH lags behind the formation of the galactic bulge. (7) We also find that the FWHM of [N II] line is well correlated with sigma(*) in 206 NLS1s, for which both parameters could be derived with reasonable accuracy. The [N II] width can predict the stellar velocity dispersion to an accuracy of similar to 30%. A similar M-BH-sigma(*) relation could be found for a larger sample of 613 NLS1s on making use of the more reliable measurements of FWHM[N II].

ESTIMATING BLACK HOLE MASSES IN ACTIVE GALACTIC NUCLEI USING THE Mg II λ2800 EMISSION LINE

We investigate the relationship between the linewidths of broad Mg II lambda 2800 and H beta in active galactic nuclei (AGNs) to refine them as tools to estimate black hole (BH) masses. We perform a detailed spectral analysis of a large sample of AGNs at intermediate redshifts selected from the Sloan Digital Sky Survey, along with a smaller sample of archival ultraviolet spectra for nearby sources monitored with reverberation mapping (RM). Careful attention is devoted to accurate spectral decomposition, especially in the treatment of narrow-line blending and Fe II contamination. We show that, contrary to popular belief, the velocity width of Mg II tends to be smaller than that of H beta, suggesting that the two species are not cospatial in the broad-line region. Using these findings and recently updated BH mass measurements from RM, we present a new calibration of the empirical prescriptions for estimating virial BH masses for AGNs using the broad Mg II and H beta lines. We show that the BH masses derived from our new formalisms show subtle but important differences compared to some of the mass estimators currently used in the literature.

A UNIFORMLY SELECTED SAMPLE OF LOW-MASS BLACK HOLES IN SEYFERT 1 GALAXIES

We have conducted a systematic search of low-mass black holes (BHs) in active galactic nuclei (AGNs) with broad Halpha emission lines, aiming at building a homogeneous sample that is more complete than previous ones for fainter, less highly accreting sources. For this purpose, we developed a set of elaborate, automated selection procedures and applied it uniformly to the Fourth Data Release of the Sloan Digital Sky Survey. Special attention is given to AGN--galaxy spectral decomposition and emission-line deblending. We define a sample of 309 type 1 AGNs with BH masses in the range

WHAT CONTROLS THE Fe II STRENGTH IN ACTIVE GALACTIC NUCLEI

8 times 10^4

THE BLUESHIFTING AND BALDWIN EFFECTS FOR THE [O III] λ5007 EMISSION LINE IN TYPE 1 ACTIVE GALACTIC NUCLEI

--

LOW-z Mg II BROAD ABSORPTION-LINE QUASARS FROM THE SLOAN DIGITAL SKY SURVEY

2 times 10^6

SIMULTANEOUS ULTRAVIOLET AND OPTICAL EMISSION-LINE PROFILES OF QUASARS: IMPLICATIONS FOR BLACK HOLE MASS DETERMINATION*

msun (with a median of

The Correlation Between X-ray and UV Properties of BAL QSOs

1.2 times 10^6

THE BALDWIN EFFECT IN THE NARROW EMISSION LINES OF ACTIVE GALACTIC NUCLEI

solar mass), using the virial mass estimator based on the broad Halpha line. About half of our sample of low-mass BHs differs from that of Greene & Ho, with 61 of them discovered here for the first time. Our new sample picks up more AGNs with low accretion rates: the Eddington ratios of the present sample range from

EDDINGTON RATIO GOVERNS THE EQUIVALENT WIDTH OF Mg II EMISSION LINE IN ACTIVE GALACTIC NUCLEI

<~0.01