STUDY OF MILLI-JANSKY SEYFERT GALAXIES WITH STRONG FORBIDDEN HIGH-IONIZATION LINES USING THE VERY LARGE ARRAY SURVEY IMAGES

Dharam V. Lal 한국천문학회 2015 Journal of The Korean Astronomical Society Vol.48 No.6

We study the radio properties at 1.4 GHz of Seyfert galaxies with strong forbidden highionization lines (FHILs), selected from the Sloan Digital Sky Survey – a large-sized sample containing nearly equal proportion of diverse range of Seyfert galaxies showing similar redshift distributions compiled by Gelbord et al. (2009) using the Very Large Array survey images. The radio detection rate is low, 49%, which is lower than the detection rate of several other known Seyfert galaxy samples. These galaxies show low star formation rates and the radio emission is dominated by the active nucleus with ≤10% contribution from thermal emission, and possibly, none show evidence for relativistic beaming. The radio detection rate, distributions of radio power, and correlations between radio power and line luminosities or X-ray luminosity for narrow-line Seyfert 1 (NLS1), Seyfert 1 and Seyfert 2 galaxies are consistent with the predictions of the unified scheme hypothesis. Using correlation between radio and [O III] 5007°A luminosities, we show that ∼8% sample sources are radio-intermediate and the remaining are radio-quiet. There is possibly an ionization stratification associated with clouds on scales of 0.1–1.0 kpc, which have large optical depths at 1.4GHz, and it seems these clouds are responsible for free–free absorption of radio emission from the core; hence, leading to low radio detection rate for these FHIL-emitting Seyfert galaxies.

Does the Jet Production Efficiency of Radio Galaxies Control Their Optical AGN Types?

Sascha Trippe 한국천문학회 2014 Journal of The Korean Astronomical Society Vol.47 No.4

The jet production efficiency of radio galaxies can be quantified by comparison of their kinetic jet powers Pjet and Bondi accretion powers PB. These two parameters are known to be related linearly, with the jet power resulting from the Bondi power by multiplication with an efficiency factor of order 1%. Using a recently published (Nemmen & Tchekhovskoy 2014 high-quality sample of 27 radio galaxies, I construct a PB-Pjet diagram that includes information on optical AGN types as far as available. This diagram indicates that the jet production efficiency is a function of AGN type: Seyfert 2 galaxies seem to be systematically (with a false alarm probability of 4.3×10-4 less efficient, by about one order of magnitude, in powering jets than Seyfert 1 galaxies, LINERs, or the remaining radio galaxies. This suggests an evolutionary sequence from Sy2s to Sy,1s and LINERs, controlled by an interplay of jets on the one hand and dust and gas in galactic nuclei on the other hand. When taking this effect into account, the PB-Pjet relation is probably much tighter intrinsically than currently assumed.

AKARI IRC INFRARED 2.5-5 ㎛ SPECTROSCOPY OF NEARBY LUMINOUS INFRARED GALAXIES

Imanishi, Masatoshi,Nakagawa, Takao,Shirahata, Mai,Ohyama, Yoichi,Onaka, Takashi The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4

We present the result of systematic AKARI IRC infrared $2.5-5{\mu}m$ spectroscopy of >100 nearby luminous infrared galaxies, to investigate the energetic roles of starbursts and optically-elusive buried AGNs. Based on (1) the equivalent widths of the $3.3{\mu}m$ PAH emission features, (2) the optical depths of absorption features, and (3) continuum slopes, we can disentangle emission from starbursts and AGNs. We find that the energetic importance of buried AGNs increases with increasing galaxy infrared luminosities, suggesting that the AGN-starburst connections (and thereby possible AGN feedback to host galaxies) are luminosity dependent.

A SPECTROSCOPIC STUDY OF THE SEYFERT GALAXY MCG-2-58-22

Choi, Chul-Sung,Dotani, Tadayasu,Chang, Heon-Young The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.3

We present analysis results of the energy spectra of MCG-2-58-22 associated with occasional flares which appear in a long-term X-ray light curve. We measure an intrinsic power-law slope of this object to be ${\Gamma}=1.74{\pm}0.02$ in the energy range of ${\sim}1-5keV$ and find that this slope is little affected by flares. We confirm that there exists a broad excess emission above 5 keV to the power-law continuum. The excess emission is less variable compared with a flux variation of flare and tends to be relatively weak during flares. A soft X-ray spectrum is also found to change, implying the presence of a variable soft component. We discuss the implications of these spectral variations.

SEOUL NATIONAL UNIVERSITY AGN MONITORING PROJECT.I. STRATEGY AND SAMPLE

우종학,손동훈,Elena Gallo,Edmund Hodges-Kluck,전이슬,신재진,배현진,조호진,조완진,강다은,Marios Karouzos,김민진,김태우,Huynh Anh N. Le,박대성,박송연,Suvendu Rakshit,성현일 한국천문학회 2019 Journal of The Korean Astronomical Society Vol.52 No.4

While the reverberation mapping technique is the best available method for measuring black hole mass in active galactic nuclei (AGNs) beyond the local volume, this method has been mainly applied to relatively low-to-moderate luminosity AGNs at low redshift. We present the strategy of the Seoul National University AGN Monitoring Project, which aims at measuring the time delay of the Hβ line emission with respect to AGN continuum, using a sample of relatively high luminosity AGNs out to redshift z ∼ 0.5. We present simulated cross correlation results based on a number of mock light curves, in order to optimally determine monitoring duration and cadence. We describe our campaign strategy based on the simulation results and the availability of observing facilities. We present the sample selection, and the properties of the selected 100 AGNs, including the optical luminosity, expected time lag, black hole mass, and Eddington ratio.

X-RAY ARCHIVAL DATA ANALYSIS OF TIME VARIABILITIES IN SEYFERT GALAXY MCG-2-58-22

CHOI CHUL-SUNG,DOTANI TADAYASU,YI INSU,FLETCHER ANDRE,KIM CHULHEE The Korean Astronomical Society 2001 Journal of The Korean Astronomical Society Vol.34 No.3

We report results from an analysis of the X-ray archival data on MCG-2-58-22 obtained with Ginga, ROSAT and ASCA. By analyzing both short- and long-term light curves, we find clear time variations, ranging widely from, $\~10^3$ s to more than several years, in the X-ray energy range 0.1 - 10 keV. In addition, a flare is detected in 1991, overlaid on a gradual, secular flux decrease from 1979 to 1993; this flare has a time scale of about 1 year, and the X-ray flux increased by at least a factor of 3. The implications of these observational results are discussed in terms of accretion flow dynamics near a supermassive black hole.

IUE SPECTRA OF THE SEYFERT 1 GALAXIES Mrk 335 and NGC 4051

HYUNG SIEK,KIM HYOUK,LEE Woo BAlK,LEE SEONG-JAE,RYU DONGSU,LEE HEE-WON The Korean Astronomical Society 2000 Journal of The Korean Astronomical Society Vol.33 No.2

The international ultraviolet explorer (IUE) spectra of a low dispersion $\~6{\AA}$, have been investigated for two Seyfert 1 galaxies, Mrk 335 and NGC 4051, well known for the line variability. The electron densities of broad line region (BLR) of these variable Seyfert 1 galaxies have been derived, which showed a non-linear abrupt variation from $10^8$ to $10^{10} cm-3$ within a month. We also found the excitation (or temperature) changes in the Mrk 335 BLR from the IUE broad line profiles analysis, but no such evidence in the NGC 4051. The large amount of mass inflow activity through the bar or spiral structure of host galaxies, may trigger the density change in BLR and emission line variability for both objects. Mass of the giant black holes appear to be order of $10^7\;M_{\bigodot}$ for both variable Seyfert l's.

The kinematics of the Seyfert 2 galaxy NGC 5728 circumnuclear region

Son, D.-H.,Hyung, S.,Ferruit, P.,Pé,contal, E.,Lee, W.-B. Blackwell Publishing Ltd 2009 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.395 No.2

<P>ABSTRACT</P><P>We secured spectral images of the circumnuclear, 12 × 10 arcsec<SUP>2</SUP> region of the Seyfert 2 galaxy NGC 5728 with the Optically Adaptive System for Imaging Spectroscopy at the Canada–France–Hawaii Telescope 3.6-m telescope. The radial velocity distribution of the two bright zones, main central (C) core and north-west (NW) core, and strategically important points along the position angles, PA 33°, 90°, 123° and 143°, are analysed. The large-scale reconstructed monochromatic images of the Hα, Hβ, [O <SMALL>III</SMALL>] and [N <SMALL>II</SMALL>] lines show a bipolar morphology along PA ∼ 123°. The prominent elliptical ring is seen in the Hα and Hβ monochromatic images. Our analysis implies that this ring is rotating in the same clockwise direction as that of the galactic disc; this elliptical ring is in fact a projected result of a circular ring of radius ∼5.4 arcsec, with <I>i</I>∼ 50° (nearly aligned with the host galactic plane).</P><P>We used the [O <SMALL>III</SMALL>]5007 line profiles for a detailed analysis of kinematics in the circumnuclear region of the NGC 5728. The [O <SMALL>III</SMALL>]5007 line profiles reveal distinct kinematical structures. (1) The strongest component of Doppler peaks: two core components, consisting of the receding main C-core and the approaching NW-core with the radial velocities, <I>V</I><SUB>r</SUB>≃+250 and −240 (or −250) km s<SUP>−1</SUP>, respectively. These two cores consist of a roughly spherically symmetric distribution of the gas with radii of <I>r</I>∼ 1.0 arcsec (at <I>V</I><SUB>r</SUB>≃+240 km s<SUP>−1</SUP>) and 0.9 arcsec (at <I>V</I><SUB>r</SUB>≃−240 km s<SUP>−1</SUP>), respectively. Hints of the presence of inflows around these cores are observed. (2) The next strong line profile component: this component corresponds to the bipolar cone aligned PA ∼ 123°. (3) The reverse S-shaped kinematical boundary which runs through the double-peaked zone of 6–7 arcsec long in the galactic major axis direction is likely to be caused by a combination of the disc rotation of the host galaxy and the revolution of the two central cores.</P>

STREAMING CIRCUMNUCLEAR GAS OF THE SEYFERT 2 GALAXY NGC 5728

Dong-Hoon Son,Siek Hyung,Seong-Jae Lee,Pierre Ferruit 한국천문학회 2009 Journal of The Korean Astronomical Society Vol.42 No.4

We investigated the circumnuclear region of the Seyfert 2 galaxy NGC 5728, using the CFHT 3.6 m OASIS [S ΙΙ], [O ΙΙΙ] & Hβ, spectral images complemented with the IUE spectra. The physical condition of the circumnuclear zone has been derived: the gas density (indicated by [S ΙΙ]6716/31 ratio) around the C core is generally similar to that around the NW core, i.e., ~ 500 cm-3. However, there appears to be evidence of a higher density shell in front of the NW core, ~ 104 cm -3 at -250 km s-1. The IUE Si ΙΙΙ]1892/C ΙΙΙ]1909 ratio implies a possible presence of a broad emission region of gas densities of ~1010 cm-3. The SE cone and surrounding area show several prominent features, while the NW cone does not show any particular structure: we identified three prominent blobs in the SE cone and one possible candidate in the NW cone. The outflow activities exist within the relatively large conic opening angle. We discussed the possibility of inflow or outflow activities of blobs found in the circumnuclear region of NGC 5728. The gas around two cores, two cones, and several blobs, is likely to be excited by the AGN hot source(s).

STREAMING CIRCUMNUCLEAR GAS OF THE SEYFERT 2 GALAXY NGC 5728

손동훈,형식,이성재,Pierre Ferruit 한국천문학회 2009 Journal of The Korean Astronomical Society Vol.42 No.5

We investigated the circumnuclear region of the Seyfert 2 galaxy NGC 5728, using the CFHT 3.6 m OASIS [SⅡ], [OⅢ], & Hβ, spectral images complemented with the IUE spectra. The physical condition of the circumnuclear zone has been derived: the gas density (indicated by [SⅡ], 6716/31 ratio) around the C core is generally similar to that around the NW core, i.e., ~ 500 cm-3. However, there appears to be evidence of a higher density shell in front of the NW core, ~10^4 cm -3 at -250kms. The IUE SiⅢ]1892/CⅢ] 1909 ratio implies a possible presence of a broad emission region of gas densities of ~1010 cm-3. The SE cone and surrounding area show several prominent features, while the NW cone does not show any particular structure: we identified three prominent blobs in the SE cone and one possible candidate in the NW cone. The outflow activities exist within the relatively large conic opening angle. We discussed the possibility of inflow or outflow activities of blobs found in the circumnuclear region of \astrobj. The gas around two cores, two cones, and several blobs, is likely to be excited by the AGN hot source(s).