arXiv subjects

Wei-Hao Bian

Publications and source records attributed to Wei-Hao Bian.

43 records · Page 3Linked to original sources

arXiv2009

The host galaxy of a narrow-line Seyfert 1 galaxy RE J1034+396 with X-ray quasi-periodic oscillations

Using simple stellar population synthesis, we model the bulge stellar contribution in the optical spectrum of a narrow-line Seyfert 1 galaxy RE J1034+396. We find that its bulge stellar velocity dispersion is $67.7\pm 8$ \kms. The supermassive black hole (SMBH) mass is about $(1-4)\times 10^6 \msun$ if it follows the well-known $\mbh-σ_*$ relation found in quiescent galaxies. We also derive the SMBH mass from the H$β$ second moment, which is consistent with that from its bulge stellar velocity dispersion. The SMBH mass of $(1-4)\times 10^6 \msun$ implies that the X-ray quasi-periodic oscillation (QPO) of RE J1034+396 can be scaled to a high-frequency QPO at 27-108 Hz found in Galactic black hole binaries with a 10 $\msun$ black hole. With the mass distribution in different age stellar populations, we find that the mean specific star formation rate (SSFR) over past 0.1 Gyr is $0.0163\pm 0.0011$ $\rm Gyr^{-1}$, the stellar mass in the logarithm is $10.155\pm 0.06$ in units of solar mass, and the current star formation rate is $0.23\pm 0.016 \msun \rm yr^{-1}$. RE J1034+396 does not follow the relation between the Eddington ratio and the SSFR suggested by Chen et al., although a larger scatter in their relation. We also suggest that about 7.0% of the total \ha luminosity and 50% of the total \oii luminosity come from the star formation process.

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arXiv2008

Hbeta Profiles in Quasars: Evidence for an Intermediate-line Region

We report on a systematic investigation of the Hbeta and Fe II emission lines in a sample of 568 quasars within z < 0.8 selected from the Sloan Digital Sky Survey. The conventional broad Hbeta emission line can be decomposed into two components--one with intermediate velocity width and another with very broad width. The velocity shift and equivalent width of the intermediate-width component do not correlate with those of the very broad component of Hbeta, but its velocity shift and width do resemble Fe II. Moreover, the width of the very broad component is roughly 2.5 times that of the intermediate-width component. These characteristics strongly suggest the existence of an intermediate-line region, whose kinematics seem to be dominated by infall, located at the outer portion of the broad-line region.

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arXiv2008

A note on black hole masses estimated by the second moment in Narrow Line Seyfert 1 Galaxies

The second moment of the H$β$ emission line is calculated for 329 narrow line Seyfert 1 galaxies (NLS1s) selected from the Sloan Digital Sky Survey (SDSS), which is used to calculate the central supermassive black hole (SMBHs) mass of each. We find that the second moment depends strongly on the broader component of the H$β$ line profile. We find that for the NLS1s requiring two Gaussians to fit the H$β$ line the mean value of the SMBH mass from the H$β$ second moment is larger by about 0.50 dex than that from the full width at half maximum (FWHM). Using the gas velocity dispersion of the core/narrow component of \oiii $λ$ 5007 to estimate the stellar velocity dispersion, $σ_{*}$, the new mass makes NLS1s fall very close to the $\mbh - σ_{*}$ relation for normal AGNs. By using $σ_{*}$ measured directly from SDSS spectra with a simple stellar population synthesis method, we find that for NLS1s with mass lower than $10^7 \msun$, they fall only marginally below the $\mbh - σ_{*}$ relation considering the large scatter in the mass calculation.

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arXiv2008

A Systematic Analysis of Fe II Emission in Quasars: Evidence for Inflow to the Central Black Hole

Broad Fe II emission is a prominent feature of the optical and ultraviolet spectra of quasars. We report on a systematical investigation of optical Fe II emission in a large sample of 4037 z < 0.8 quasars selected from the Sloan Digital Sky Survey. We have developed and tested a detailed line-fitting technique, taking into account the complex continuum and narrow and broad emission-line spectrum. Our primary goal is to quantify the velocity broadening and velocity shift of the Fe II spectrum in order to constrain the location of the Fe II-emitting region and its relation to the broad-line region. We find that the majority of quasars show Fe II emission that is redshifted, typically by ~ 400 km/s but up to 2000 km/s, with respect to the systemic velocity of the narrow-line region or of the conventional broad-line region as traced by the Hbeta line. Moreover, the line width of Fe II is significantly narrower than that of the broad component of Hbeta. We show that the magnitude of the Fe II redshift correlates inversely with the Eddington ratio, and that there is a tendency for sources with redshifted Fe II emission to show red asymmetry in the Hbeta line. These characteristics strongly suggest that Fe II originates from a location different from, and most likely exterior to, the region that produces most of Hbeta. The Fe II-emitting zone traces a portion of the broad-line region of intermediate velocities whose dynamics may be dominated by infall.

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arXiv2008

Supermassive Black Hole Masses in Type II Active Galactic Nuclei with Polarimetric Broad Emission Lines

Type II AGNs with polarimetric broad emission line provided strong evidence for the orientation-based unified model for AGNs. We want to investigate whether the polarimetric broad emission line in type II AGNs can be used to calculate their central supermassive black hole (SMBH) masses, like that for type I AGNs. We collected 12 type II AGNs with polarimetric broad emission line width from the literatures, and calculated their central black hole masses from the polarimetric broad line width and the isotropic \oiii luminosity. We also calculate the mass from stellar velocity dispersion, $σ_*$, with the $\mbh-σ_*$ relation.We find that: (1) the black hole masses derived from the polarimetric broad line width is averagely larger than that from the $\mbh- σ_*$ relation by about 0.6 dex, (2) If these type II AGNs follow $\mbh-σ_*$ relation, we find that the random velocity can't not be omitted and is comparable with the BLRs Keplerian velocity. It is consistent with the scenery of large outflow from the accretion disk suggested by Yong et al.

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arXiv2008

The Origin and Evolution of \civ Baldwin Effect in QSOs from the Sloan Digital Sky Survey

Using a large sample of 26623 quasars with redshifts in the range $1.5 \le z\le 5.1$ with \civ $λ$1549 Åemission line in Fifth Data Release of the Sloan Digital Sky Survey (SDSS), we investigate the cosmological evolution of the Baldwin Effect, i.e. the relation between the equivalent width (EW) of the \civ emission line and continuum luminosity. We confirm the earlier result that there exists a strong correlation between the \civ EW and the continuum luminosity, and we find that, up to $z\approx 5$, the slope of the Baldwin Effect seems to have no effect of cosmological evolution. A sub-sample of 13960 quasars with broad \civ $λ$1549 Åemission line from SDSS is used to explore the origin of the Baldwin Effect. We find that \civ EW have a strong correlation with the mass of supermassive black hole (SMBH), and a weak correlation with the Eddington ratio, $\lb/\ledd$. This suggests that the SMBH mass is probably the primary drive for the Baldwin Effect.

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arXiv2007

Active Galactic Nuclei with Double-Peaked Balmer Lines: I. Black Hole Masses and the Eddington ratios

Using the stellar population synthesis, we model the stellar contribution for a sample of 110 double-peaked broad-lines AGNs from the Sloan Digital Sky Survey (SDSS). The stellar velocity dispersions ($σ_*$) are obtained for 52 double-peaked AGNs with obvious stellar absorption features, ranging from 106 to 284 \kms. We also use multi-component profiles to fit \OIII $λ\lambda4959,5007$ and H$β$ emission lines. Using the well-established $M_{\rm bh}-σ_*$ relation, the black hole masses are calculated to range from $1.0\times 10^{7}$ to $5.5\times 10^{8}$ $\Msun$, and the Eddington ratio from about 0.01 to about 1. Comparing with the known $R_{\rm BLR}-L$ relation, we can get the factor $f$, which indicates BLRs' geometry, inclination and kinematics. We find that $f$ far deviates from 0.75, suggesting the non-virial dynamics of broad line regions. The peak separation is mildly correlated with the Eddington ratio and SMBH mass with almost the same correlation coefficients. It implies that it is difficult to detect obvious double-peak AGNs with higher Eddington ratios. Using the monochromatic luminosity at 5100Åto trace the bolometric luminosity, we find that the external illumination of the accretion disk is needed to produce the observed strength of H$α$ emission line.

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