Tinggui Wang

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.

Polar outflows in six broad absorption line quasars

Using radio observations by FIRST and NVSS, we build a sample of 151 radio-variable quasars selected from the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Six (and probably another two) of these objects are classified as broad absorption line (BAL) quasars and show radio flux variations of a few tens of percent within 1.5-5 yr. Such large amplitudes of variations imply brightness temperatures much higher than the inverse Compton limits (10(12) K) in all these BAL quasars, suggesting the presence of relativistic jets beaming toward the observer. The angles between the outflow and the jet are constrained to be less than similar to 20 degrees. Such BAL quasars with polar outflows are beyond the simple unification models of BAL and non-BAL quasars, which hypothesize BAL quasars as otherwise normal quasars seen nearly edge-on.

Broad‐line Balmer decrements in blue active galactic nuclei

We have investigated the broad-line Balmer decrements (H alpha/H beta) for a large, homogeneous sample of Seyfert 1 galaxies and quasi-stellar objects (QSOs) using spectroscopic data obtained in the Sloan Digital Sky Survey. The sample, drawn from the Fourth Data Release, comprises 446 low-redshift (z less than or similar to 0.35) active galactic nuclei (AGN) that have blue optical continua as indicated by the spectral slopes in order to minimize the effect of dust extinction. We find that (i) the distribution of the intrinsic broad-line H alpha/H beta ratio can be well described by log-Gaussian, with a peak at H alpha/H beta = 3.06 and a standard deviation of about 0.03 dex only; (ii) the Balmer decrement does not correlate with AGN properties such as luminosity, accretion rate and continuum slope, etc.; (iii) on average, the Balmer decrements are found to be only slightly larger in radio-loud sources (3.37) and sources having double-peaked emission-line profiles (3.27) compared to the rest of the sample. We therefore suggest that the broad-line H alpha/H beta ratio can be used as a good indicator for dust extinction in the AGN broad-line region; this is especially true for radio-quiet AGN with regular emission-line profiles, which constitute the vast majority of the AGN population.

SDSS J094857.3+002225: A Very Radio Loud, Narrow-Line Quasar with Relativistic Jets?

We report the identification of a very radio loud, narrow-line quasar, SDSS J094857.3+002225, discovered in the Sloan Digital Sky Survey (SDSS) early data release (EDR). With FWHM (Hβ) ≈ 1500 km s-1 and undetected [O III] λλ 4959, 5007 SDSS J094857.3+002225 is consistent with the conventional definition of narrow-line Seyfert 1 galaxies (NLS1s). Its strong optical Fe II emission [R4570 ≡ f(Fe II λ4570)/f(Hβ) ≈ 1.59] is also typical of NLS1s. With a radio loudness RL ≡ (fν,4.85 GHz/fν,B) 1000 and radio power of P4.85 GHz ~ (3.6-5.2) × 1026 W Hz-1, it is the first bona fide, very radio loud NLS1. The inverted radio spectrum and very high brightness temperature (1013 K) derived from variation of the radio flux suggest the presence of a relativistic jet beaming toward the observer in this NLS1.

A Narrow-Line Seyfert 1-Blazar Composite Nucleus in 2MASX J0324+3410

We report the identification of 2MASX J032441.19 + 341045.9 (hereafter 2MASX J0324 + 3410) with an appealing object that shows the dual properties of both a narrow-line Seyfert 1 galaxy (NLS1) and a blazar. Its optical spectrum, which has a H beta line width of about 1600 km s(-1) (FWHM), an [O III]-to-H beta line ratio of similar or equal to 0.12, and strong Fe II emission, clearly fulfills the conventional definition of NLS1s. On the other hand, 2MASX J0324 + 3410 also exhibits some behavior that is characteristic of blazars, including a flat radio spectrum above 1 GHz, a compact core plus a one-sided jet structure on milliarcsecond scale at 8.4 GHz, highly variable fluxes in the radio, optical, and X-ray bands, and a possible detection of TeV gamma-ray emission. On its optical image, obtained with the HST WFPC2, the active nucleus is displaced from the center of the host galaxy, which exhibits an apparent one-armed spiral structure extended to 16 kpc. The remarkable hybrid behavior of this object presents a challenge to current models of NLS1s and gamma-ray blazars.

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

PARTIALLY OBSCURED QUASARS IN THE SLOAN DIGITAL SKY SURVEY EARLY DATA RELEASE

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Ensemble Learning for Independent Component Analysis of Normal Galaxy Spectra

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WHAT CONTROLS THE Fe II STRENGTH IN ACTIVE GALACTIC NUCLEI

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

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