arXiv subjects

Tinggui Wang

Publications and source records attributed to Tinggui Wang.

155 records · Page 9Linked to original sources

arXiv2007

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 which shows the dual properties of both a narrow line Seyfert 1 galaxy (NLS1) and a blazar. Its optical spectrum, which has a Hβline width about 1600 km s^-1 (FWHM), an [OIII] to Hβline ratio ~0.12, and strong FeII emission, clearly fulfills the conventional definition of NLS1s. On the other hand, 2MASX J0324+3410 also exhibits some behavior which is characteristic of blazars, including a flat radio spectrum above 1 GHz, a compact core plus a one-sided jet structure on mas-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 NLS1 galaxies and $γ$-ray blazars.

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arXiv2006

Systematic study of a large sample of NLS1 galaxies from SDSS: first results

This proceedings contribution summarizes first results obtained from a systematic study of 2011 NLS1 galaxies, as presented in Zhou et al. (2006, ApJS 166, 128). The sample was compiled by examining the spectral parameters of galaxies and QSOs derived from SDSS DR3 data. We discuss some preliminary results on the statistic properties of the sample, such as the fraction of NLS1, the properties of broad and narrow emission lines, and emission in other wavebands. The black hole mass--velocity dispersion relation for NLS1s was re-examined using the velocity dispersion values estimated from the stellar absorption spectra of the host galaxies. Preliminary result from an X-ray study for a small subset using data obtained by XMM-Newton is briefly discussed.

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arXiv2006

Broad-line AGNs with Candidate Intermediate-mass Black holes in the Sloan Digital Sky Survey

We have conducted a systematic search of AGNs with IMBHs from the SDSS DR4. As results we found 245 candidates of broad-line AGN with M_{BH}<10^6 \Msun estimated from the luminosity and width of the broad Halpha component. Compared to the pioneer Greene & Ho (2004) sample of 19 IMBH AGNs, our sample has improved in covering a larger range of the Eddington ratio, as well as black hole mass and redshift, taking the advantage of our AGN-galaxy spectral decomposition algorithm. Among these, thirty-six have L_{bol}/L_{Edd} < 0.1, hinting that a significant fraction of IMBHs might exist with weak or no nuclear activity.

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arXiv2006

SDSS J160531.84+174826.1: A Dwarf Disk Galaxy With An Intermediate-Mass Black Hole

We report the discovery of a dwarf Seyfert 1 active galactic nucleus (AGN) with a candidate intermediate-mass black hole hosted by the dwarf galaxy SDSS J160531.84+174826.1 at z=0.032. A broad component of the H-alpha line with FWHM=781 km/s is detected in its optical spectrum, and a bright, point-like nucleus is evident from a HST imaging observation. Non-thermal X-ray emission is also detected from the nucleus. The black hole mass, as estimated from the luminosity and width of the broad H-alpha component, is about 7x10^4 \msun. The host galaxy appears to be a disk galaxy with a boxy bulge or nuclear bar; with an absolute magnitude of M_R = -17.8 (M_B = -16.4), it is among the least luminous host galaxies ever identified for a Seyfert 1.

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arXiv2006

A Comprehensive Study of 2 000 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 $\sim 2~000$ NLS1. This sample dramatically increases the number of known NLS1 by a factor of $\sim 10$ 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 (abbreviated).

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arXiv2006

Evidence for a population of beamed radio intermediate quasars

Whether radio intermediate quasars possess relativistic jets as radio-loud quasars is an important issue in the understanding of the origin of radio emission in quasars. In this letter, using the two-epoch radio data obtained during Faint Image of Radio Sky at Twenty centimeter sky (FIRST) and NOAO VLA Sky Survey (NVSS), we identify 89 radio variable sources in the Sloan Digital Sky Survey. Among them, more than half are radio intermediate quasars (RL=f2cm/f2500A<250). For all objects with available multiple band radio observations, the radio spectra are either flat or inverted. The brightness temperature inferred from the variability is larger than the synchrotron-self Compton limit for a stationary source in 87 objects, indicating of relativistic beaming. Considering the sample selection and viewing angle effect, we conclude that relativistic jets probably exist in a substantianl fraction of radio intermediate quasars.

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arXiv2005

Ensemble Learning Independent Component Analysis of Normal Galaxy Spectra

In this paper, we employe a new statistical analysis technique, Ensemble Learning for Independent Component Analysis (EL-ICA), on the synthetic galaxy spectra from a newly released high resolution evolutionary model by Bruzual & Charlot. We find that EL-ICA can sufficiently compress the synthetic galaxy spectral library to 6 non-negative Independent Components (ICs), which are good templates to model huge amount of normal galaxy spectra, such as the galaxy spectra in the Sloan Digital Sky Survey (SDSS). Important spectral parameters, such as starlight reddening, stellar velocity dispersion, stellar mass and star formation histories, can be given simultaneously by the fit. Extensive tests show that the fit and the derived parameters are reliable for galaxy spectra with the typical quality of the SDSS.

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arXiv2005

Polar Outflows in Six Broad Absorption Line Quasars

Using the 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 (probably another two) among them are classified as broad absorption line (BAL) quasars, with radio flux variations of a few 10 percent within 1.5-5 years. Such large amplitudes of the variations imply brightness temperatures much higher than the inverse Compton limits (10$^{12}$ K) in all the BAL quasars, suggesting the presence of relativistic jets beaming toward the observer. The angle between the outflow and the jet is constrained to be less than $\sim 20^{\circ}$. Such BAL quasars with polar outflows are beyond the simple unification models of BAL quasars and non-BAL quasars, which hypothesize that BAL quasars are normal quasars seen nearly edge-on.

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arXiv2005

Strong CaII absorption lines in the reddened quasar SDSS J2339$-$0912: Evidence of the collision/merger in the host galaxy?

We report the detection of strong CaII/MgII absorption lines at the quasar redshift in the narrow line quasar SDSS J2339-0912 (z=0.6604). The quasar exhibits strong FeII, small Balmer emission line width and a very red B-Ks color. Both the optical continuum and broad emission lines are reddened by SMC-like dust of E(B-V)~1.0 mag, while its near-infrared color (J-Ks=1.60) shows little reddening. The CaII absorption lines are saturated and resolved with an FWHM of 362 km/s and an equivalent width of W_{CaII K}=4.2Å(in the source rest frame). MgII absorption lines are also saturated and have a similar line width. The line profile and the fact that there is no evidence for starlight from the host galaxy suggest that these absorption lines are not of a stellar origin. The ratio of column density of CaII to that of dust is consistent with that of the ISM in our Galaxy. We suggest that both the heavy reddening and the large absorption line width are due to the highly disturbed ISM on the line of sight toward the quasar, and that the disturbance is caused by a galaxy collision or even merger in the quasar host galaxy.

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arXiv2004

Obscured Binary Quasar Cores in SDSS J104807.74+005543.5?

We report the discovery of a possible close binary system of quasars in SDSS J1048+0055. The [OIII]4959,5007 emission lines are clearly double-peaked, and two discrete radio sources with a projected physical separation of ~20 pc are found in the VLBA milliarcsec resolution image at 8.4 GHz. Each of the [O III]4959,5007 doublets and Hbeta can be well modelled by two Gaussians and the line ratio, [O III]5007/Hbeta ~7, is typical of Seyfert 2 galaxies. No broad component of Hbeta was detected and its [O III]5007 luminosity, L_[OIII] ~ 9.2 times 10^42 erg s^-1, is comparable to luminous quasars and is a few ten times more luminous than typical Seyfert galaxies. One natural interpretation is that SDSS J1048+0055 contains two close quasar-like nuclei and the BLR around them are obscured. Other possible models are also discussed. We suggest that double-peaked narrow emission line profile may be an effective way of selecting candidates of binary black holes with intermediate separation.

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arXiv2000

Possible Evidence for a Truncated Thin Disk in Seyfert 1 Galaxy NGC4593

We compile the multi-band spectral energy distribution (SED) of Seyfert 1 galaxy NGC4593, and investigate its optical-to-ultraviolet (OUV) continuum and iron Kαline profile. No strong ``big blue bump'' is found in OUV band. The iron Kαline profile is not as broad as expected from a disk which extends down to the last stable orbit. Both of them can be modeled by a truncated thin disk, and support the existence of a truncated thin disk in the system. It is of much interest that NGC4593 may be a typical object with an accretion rate \dot{m}=\dot{M}/M_{Edd} \sim 0.01-0.1 and harbors a two component accretion flow: an outer thin disk and an inner hot flow--possibly ADAF, analogous to the low and intermediate state of low mass X-ray binaries (LMXB).

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