• Publications of The Korean Astronomical Society
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• v.4 no.1
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• pp.1-15
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• 1989

A jet plasmoid model for 3C.449 has been constructed by introducing a plasma.ejecting black hole orbiting around the center of its parent cD galaxy. We examined the characteristics of the jet trajectory by varying the values of (1) orbiting radius and velocity of the black hole, (2) plasma ejection velocity, (3) size, mass and space velocity of the parent galaxy, (4) size of the galactic core and (5) the density of the intergalactic medium. In our model calculation the effect of the gravity by the parent galaxy and the ram pressure by the intergalactic medium have been taken in account. It is found that our dynamical model accounts reasonably well for the observed structure of 3C449. Our proposed model suggests that the buoyancy force near the galactic center plays an important role in the formation of the curved structure of the radio jet.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.48.2-48.2
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• 2014

We present long-term optical to NIR data of the tidal disruption object, Swift J1644+57. The data were obtained with CQUEAN, UKIRT WFCAM observations. We analyze the morphology of the host galaxy of this object and decompose the bulge component using high resolution HST WFC3 images. We conclude that the host galaxy is bulge dominant. We also estimate the multi-band fluxes of the host galaxy through the light curves based on the long-term observational data. We fit the SED models to the multi-band fluxes of the host galaxy and determine its stellar mass. Finally, we estimate the mass of the central super massive black hole which is responsible for the tidal disruption event. The estimated stellar mass and black hole mass are ${\sim}10^{9.1}M_{\odot}$, ${\sim}10^{6.8}M_{\odot}$, respectively. We compare our results to other previous estimates.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.475-476
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• 2015

We analyze the host galaxy of the tidal disruption object, Swift J1644+57, based on long-term optical to NIR data obtained with CQUEAN and UKIRT WFCAM observations. We decompose the bulge component using high resolution HST WFC3 images. We conclude that the host galaxy is bulge dominant. We investigate optical to NIR light curves and estimate the multi-band fluxes of the host galaxy. We fit spectral energy distribution (SED) models in order to determine the stellar mass. Finally, we estimate the mass of the black hole in the center of the host galaxy based on several scale relations.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.80.1-80.1
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• 2012

The $2.5-5.0{\mu}m$ spectrum of AGN was poorly understood due to the atmosphere effect beyond $2{\mu}m$. Nevertheless, the $2.5-5.0{\mu}m$ range includes several important lines, such as $Br{\beta}$ ($2.63{\mu}m$), $Br{\alpha}$ ($4.05{\mu}m$), PAH (3.3${\mu}m$) and many molecular or atomic lines. We compile $2.5-5.0{\mu}m$ spectra of 79 AGNs and QSOs from infrared camera (IRC) on AKARI infrared astronomy satellite. Our $2.5-5.0{\mu}m$ spectra will provide an access to full wavelength spectra of AGNs for the first time. Moreover, we present the Brackett line properties, FWHMs and luminosities, of AGNs. Using these Brackett line properties, we derive new black hole (BH) mass estimators. The new BH mass estimators using NIR hydrogen lines will be very useful to estimate BH mass of dusty red AGNs in the future.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.51.1-51.1
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• 2011

Red dusty Active Galactic Nuclei (AGNs) are suspected to mid-stage between ULIRG and AGN phase. As well as, red AGNs are suspected that they have more than 50% of whole AGN population. In order to understand the character of red AGNs, Black Hole (BH) mass of red AGN is a key property and can not measured by existing method such as reverberation mapping and single epoch method. Thus we still don't know their character and properties in clearly. To estimate properties of red AGNs without the effect of dust-obscuration, we have obtained Near InfraRed (NIR) spectra of 31 reverberation mapped AGNs and 49 Palomar-Green(PG) Quasi-Stellar Object (QSO) by using the infrared camera (IRC) for AKARI with unique wavelength range $2.5-5.0{\mu}m$. From this spectra, we measured the FWHM and luminosity of brackett ${\alpha}$ and ${\beta}$ at 4.0, 2.6 micron meter for deriving new BH mass estimators based on the properties of Brackett line emission.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.49.1-49.1
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• 2011

Utilizing single-epoch spectra and the empirical relation between the size of the broad-line region and AGN continuum luminosity, the so-called single-epoch method has been widely used for estimating AGN black hole masses. However, the systematic uncertainties and the potential biases of this method are not well examined. Taking the full advantage of the high-quality homogeneous spectra from the Lick AGN Monitoring Project (LAMP), we investigate in detail the uncertainties of single-epoch mass estimates by comparing with the reverberation-mapping results. We find that the uncertainty due to AGN variability is less than 0.1 dex, while there is a systematic offset between single-epoch masses and reverberation masses. Particularly, narrow-line Seyfert 1 galaxies show that the Hbeta line widths measured from single-epoch (or mean) spectra are systematically larger than those from rms spectra, indicating a potential bias of single-epoch masses. We will present the detailed measurement method, the test of virial assumption, and the systematic uncertainties.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.48.2-48.2
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• 2011

Using the newly commissioned Fiber-Multi-Object-Spectrograph at the Subaru telescope, we obtained near-IR spectra of a sample of 19 AGNs at 0.6 < z < 2.6, selected from the NOAO Deep Wide-Field Survey (NDWFS) Bootes field, in order to calibrate high-z black hole mass (MBH) estimators. MBHs are generally determined through the kinematics of ionized gas clouds around the black hole assuming virial equilibrium. The velocity profiles of $H{\beta}/H{\alpha}$, MgII and CIV are used to infer the gas kinematics of low-z, mid-z, and high-z quasars, respectively. However, the MBH based on MgII and CIV is not very well calibrated. We compare the $H{\alpha}$ - based MBH estimates from the new FMOS near-IR spectra, with the MgII-based MBH estimates from our existing optical spectra, and investigate the systematic differences.

• Journal of The Korean Astronomical Society
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• v.35 no.3
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• pp.123-130
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• 2002

An elliptical accretion disk may be formed by tidally disrupted debris of a flying-by star in an active galactic nucleus (AGN) or by tidal perturbation due to a companion in a binary black hole system. We investigate the iron K$\alpha$ line profiles expecting from a geometrically thin, relativistic, elliptical disk in terms of model parameters, and find that a broad and skewed line profile can be reproduced well. Its shape is variable to the model parameters, such as, the emissivity power-law index, the ellipticity of the disk, and the major axis orientation of the elliptical accretion disk. We suggest that our results may be useful to search for such an elliptical disk and consequently the tidal disruption event.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.77.2-77.2
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• 2019

Measurements of supermassive black hole (SMBH) masses are crucial in studying the co-evolution of SMBHs and their host galaxies. Although reverberation mapping is the most accurate method known to date, this requires spectroscopic monitoring over long periods. Thus, the current sample barely reaches three digits. The virial method, on the other hand, uses emission-line and continuum properties from a single spectrum to estimate the SMBH mass; hence the name single-epoch method. The Sloan Digital Sky Survey (SDSS) has observed spectra of almost all quasi-stellar objects (QSOs) discovered so far. Building on previous studies, using the single-epoch method, we estimate the SMBH masses of more than 500,000 QSOs from the SDSS DR14 Quasar Catalog. This increases the mass-estimated SMBH sample almost by a factor of two, and especially more for the low-mass regime, which was the main target of SDSS-IV (eBOSS).

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.62.1-62.1
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• 2020

We present a scaling relation between black hole (BH) mass and bulge luminosity for 35 nearby (z<0.1) type 1 active galaxies, selected from the 70-month Swift-BAT X-ray source catalog. Thanks to the unbiased selection and proximity of the parent sample, our sample is suitable to study the physical connection between central black holes and host galaxies. We use the F814W images obtained with the Advanced Camera for Surveys on Hubble Space Telescope, to perform the imaging decomposition with GALFIT. With a careful treatment on the PSF model, we measure the I-band bulge brightness robustly. In combination with the BH mass estimated from a single-epoch spectroscopic data, we present the correlation between BH mass and bulge luminosity of the target AGNs. We demonstrate that our sample marginally lies off from the M(BH)-L(bulge) relation of inactive galaxies. We discuss possible physical origins of this discrepancy. Finally, we present how the relation depends on the photometric properties of AGNs and host galaxies, which may provide an useful insight on the co-evolution between BHs and host galaxies.