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.

AMUSE-VIRGO. III. MID-INFRARED PHOTOMETRY OF EARLY-TYPE GALAXIES AND LIMITS ON OBSCURED NUCLEAR EMISSION

Leipski, Christian,Gallo, Elena,Treu, Tommaso,Woo, Jong-Hak,Miller, Brendan P.,Antonucci, Robert IOP Publishing 2012 The Astrophysical journal Vol.744 No.2

<P>We complete our census of low-level nuclear activity in Virgo Cluster early-type galaxies by searching for obscured emission using Spitzer Space Telescope mid-infrared (MIR) imaging at 24 mu m. Of a total sample of 95 early-type galaxies, 53 objects are detected, including 16 showing kiloparsec-scale dust in optical images. One-dimensional and two-dimensional surface photometry of the 37 detections without extended dust features reveals that the MIR light is more centrally concentrated than the optical light as traced by Hubble Space Telescope F850LP-band images. No such modeling was performed for the sources with dust detected in the optical images. We explore several possible sources of the MIR excess emission, including obscured nuclear emission. We find that radial metallicity gradients in the stellar population appear to be a natural and most likely explanation for the observed behavior in a majority of the sources. Alternatively, if the concentrated MIR emission were due to nuclear activity, it would imply a MIR-to-X luminosity ratio similar to 5-10 for the low-luminosity active galactic nucleus (AGN) detected in X-rays by our survey. This ratio is an order of magnitude larger than that of typical low-luminosity AGNs and would imply an unusual spectral energy distribution. We conclude that the black holes found by our survey in quiescent early-type galaxies in Virgo have low bolometric Eddington ratios arising from low accretion rates and/or highly radiatively inefficient accretion.</P>

AMUSE-Field I: NUCLEAR X-RAY PROPERTIES OF LOCAL FIELD AND GROUP SPHEROIDS ACROSS THE STELLAR MASS SCALE

Miller, Brendan,Gallo, Elena,Treu, Tommaso,Woo, Jong-Hak IOP Publishing 2012 The Astrophysical journal Vol.747 No.1

<P>We present the first results from AMUSE-Field, a Chandra survey designed to characterize the occurrence and intensity of low-level accretion onto supermassive black holes (SMBHs) at the center of local early-type field galaxies. This is accomplished by means of a Large Program targeting a distance-limited (<30 Mpc) sample of 103 early types spanning a wide range in stellar masses. We acquired new ACIS-S observations for 61 objects down to a limiting (0.3-10 keV) luminosity of 2.5 x 10(38) erg s(-1), and we include an additional 42 objects with archival (typically deeper) coverage. A nuclear X-ray source is detected in 52 out of the 103 galaxies. After accounting for potential contamination from low-mass X-ray binaries, we estimate that the fraction of accreting SMBHs within the sample is 45% +/- 7%, which sets a firm lower limit on the occupation fraction within the field. The measured nuclear X-ray luminosities are invariably highly sub-Eddington, with L-X/L-Edd ratios between similar to 10(-4) and 10(-8). As also found in a companion survey targeting Virgo early types, the active fraction increases with increasing host galaxy stellar mass, reflective of 'Eddington incompleteness' within the lower-mass objects. For the Field sample, the average nuclear X-ray luminosity scales with the host stellar mass as M-star(0.71 +/- 0.10), with an intrinsic scatter of 0.73 +/- 0.09 dex. Qualitatively similar results hold for morphologically homogeneous (type E) or uniform sensitivity (new observations only) subsets. A majority of the AMUSE-Field galaxies (78%) inhabit groups, enabling us to investigate the influence of group richness on nuclear activity. We see no evidence for a positive correlation between nuclear X-ray luminosity, normalized to host properties, and galaxy density. Rather, while the scatter is substantial, it appears that the Eddington-scaled X-ray luminosity of group members may be slightly lower than for isolated galaxies, and that this trend continues to cluster early types.</P>

THE ROLE OF ENVIRONMENT IN LOW-LEVEL ACTIVE GALACTIC NUCLEUS ACTIVITY: NO EVIDENCE FOR CLUSTER ENHANCEMENT

Miller, Brendan,Gallo, Elena,Treu, Tommaso,Woo, Jong-Hak IOP Publishing 2012 ASTROPHYSICAL JOURNAL LETTERS - Vol.745 No.1

<P>We use the AMUSE-Virgo and AMUSE-Field surveys for nuclear X-ray emission in early-type galaxies to conduct a controlled comparison of low-level supermassive black hole activity within cluster and field spheroids. While both the Virgo and the Field samples feature highly sub-Eddington X-ray luminosities (L-X/L-Edd between similar to 10(-8) and 10(-4)), we find that after accounting for the influence of host galaxy stellar mass, the field early-type galaxies tend toward marginally greater (0.38 +/- 0.14 dex) nuclear X-ray luminosities, at a given black hole mass, than their cluster counterparts. This trend is qualitatively consistent with the field black holes having access to a greater reservoir of fuel, plausibly in the form of cold gas located near the nucleus. We are able to rule out at high confidence the alternative of enhanced X-ray activity within clusters. Presuming nuclear X-ray emission correlates with the total energy and momentum output of these weakly accreting black holes, this indicates that low-level active galactic nucleus feedback is not generally stronger within typical cluster galaxies than in the field. These results confirm that for most cluster early-type galaxies (i.e., excluding brightest cluster galaxies) direct environmental effects, such as gas stripping, are more relevant in quenching star formation.</P>

X-RAY CONSTRAINTS ON THE LOCAL SUPERMASSIVE BLACK HOLE OCCUPATION FRACTION

Miller, Brendan P.,Gallo, Elena,Greene, Jenny E.,Kelly, Brandon C.,Treu, Tommaso,Woo, Jong-Hak,Baldassare, Vivienne IOP Publishing 2015 The Astrophysical journal Vol.799 No.1

<P>Distinct seed formation mechanisms are imprinted upon the fraction of dwarf galaxies currently containing a central supermassive black hole. Seeding by Population III remnants is expected to produce a higher occupation fraction than is generated with direct gas collapse precursors. Chandra observations of nearby early-type galaxies can directly detect even low-level supermassive black hole activity, and the active fraction immediately provides a firm lower limit to the occupation fraction. Here, we use the volume-limited AMUSE surveys of similar to 200 optically selected early-type galaxies to characterize simultaneously, for the first time, the occupation fraction and the scaling of L-X with M-star, accounting for intrinsic scatter, measurement uncertainties, and X-ray limits. For early-type galaxies with M-star < 10(10)M(circle dot), we obtain a lower limit to the occupation fraction of >20% (at 95% confidence), but full occupation cannot be excluded. The preferred dependence of log L-X upon log M-star has a slope of similar to 0.7-0.8, consistent with the 'downsizing' trend previously identified from the AMUSE data set, and a uniform Eddington efficiency is disfavored at similar to 2 sigma. We provide guidelines for the future precision with which these parameters may be refined with larger or more sensitive samples.</P>

AMUSE-FIELD. II. NUCLEATION OF EARLY-TYPE GALAXIES IN THE FIELD VERSUS CLUSTER ENVIRONMENT

Baldassare, Vivienne F.,Gallo, Elena,Miller, Brendan P.,Plotkin, Richard M.,Treu, Tommaso,Valluri, Monica,Woo, Jong-Hak IOP Publishing 2014 The Astrophysical journal Vol.791 No.2

<P>The optical light profiles of nearby early-type galaxies are known to exhibit a smooth transition from nuclear light deficits to nuclear light excesses with decreasing galaxy mass, with as much as 80% of the galaxies with stellar masses below 10(10) M-circle dot hosting a massive nuclear star cluster (NSC). At the same time, while all massive galaxies are thought to harbor nuclear supermassive black holes (SMBHs), observational evidence for SMBHs is slim at the low end of the mass function. Here, we explore the environmental dependence of the nucleation fraction by comparing two homogeneous samples of nearby field versus cluster early-type galaxies with uniform Hubble Space Telescope (HST) coverage. Existing Chandra X-ray Telescope data for both samples yield complementary information on low-level accretion onto nuclear SMBHs. Specifically, we report on dual-band (F475W and F850LP) Advanced Camera for Surveys (ACS) imaging data for 28 out of the 103 field early-type galaxies that compose the AMUSE-Field Chandra survey, and compare our results against the companion HST and Chandra surveys for a sample of 100 Virgo Cluster early-types (ACS Virgo Cluster and AMUSE-Virgo surveys, respectively). We model the two-dimensional light profiles of the field targets to identify and characterize NSCs, and find a field nucleation fraction of 26%(+ 17%)(-11%) (at the 1 sigma level), consistent with the measured Virgo nucleation fraction across a comparable mass distribution (30%(+ 17%)(-12%)). Coupled with the Chandra result that SMBH activity is higher for the field, our findings indicate that, since the last epoch of star formation, the funneling of gas to the nuclear regions has been inhibited more effectively for Virgo galaxies, arguably via ram pressure stripping.</P>

X-ray AGNs in Abell 133

Jaejin Shin,Jong-Hak Woo,Elena Gallo,Richard M. Plotkin,John S. Mulchaey 한국천문학회 2015 天文學會報 Vol.40 No.1

The Limited Impact of Outflows: Integral-field Spectroscopy of 20 Local AGNs

Bae, Hyun-Jin,Woo, Jong-Hak,Karouzos, Marios,Gallo, Elena,Flohic, Helene,Shen, Yue,Yoon, Suk-Jin American Astronomical Society 2017 The Astrophysical journal Vol.837 No.1

<P>To investigate active galactic nucleus (AGN) outflows as a tracer of AGN feedback on star formation, we perform integral-field spectroscopy of 20 type 2 AGNs at z < 0.1, which are luminous AGNs with [O III] luminosity > 10(41.5) erg s(-1) that exhibit strong outflow signatures in the [O III] kinematics. By decomposing the emission-line profile, we obtain the maps of the narrow and broad components of the [O III] and Ha lines, respectively. The broad components in both [O III] and Ha represent the nongravitational kinematics, that is, gas outflows, while the narrow components, especially in Ha, represent the gravitational kinematics, that is, the rotational disk. By using the integrated spectra within the flux-weighted size of the narrow-line region, we estimate the energetics of the gas outflows. The ionized gas mass is 1.0-38.5 x 10(5)M(circle dot), and the mean mass outflow rate is 4.6 +/- 4.3 M-circle dot yr(-1), which is a factor of similar to 260 higher than the mean mass accretion rate of 0.02 +/- 0.01 M-circle dot yr(-1). The mean energy injection rate of the sample is 0.8% +/- 0.6% of the AGN bolometric luminosity L-bol, while the momentum flux is (5.4 +/- 3.6) x L-bol/c on average, except for the two most kinematically energetic AGNs with low L-bol, which are possibly due to the dynamical timescale of the outflows. The estimated outflow energetics are consistent with the theoretical expectations for energy-conserving outflows from AGNs, yet we find no supporting evidence of instantaneous quenching of star formation due to the outflows.</P>

Optical 3D Spectroscopic Survey on Gas Outflows in Type 2 AGNs

Hyun-Jin Bae,Jong-Hak Woo,Marios Karouzos,Elena Gallo,Yue Shen,Helene Flohic 한국천문학회 2015 天文學會報 Vol.40 No.1

The Limited Impact of AGN Outflows: IFU study of 20 local AGNs

Hyun-Jin Bae,Jong-Hak Woo,Marios Karouzos,Elena Gallo,Helene Flohic,Yue Shen,Suk-Jin Yoon 한국천문학회 2017 天文學會報 Vol.42 No.1