http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
STRONG LENS TIME DELAY CHALLENGE. II. RESULTS OF TDC1
Liao, Kai,Treu, Tommaso,Marshall, Phil,Fassnacht, Christopher D.,Rumbaugh, Nick,Dobler, Gregory,Aghamousa, Amir,Bonvin, Vivien,Courbin, Frederic,Hojjati, Alireza,Jackson, Neal,Kashyap, Vinay,Rathna Ku IOP Publishing 2015 The Astrophysical journal Vol.800 No.1
<P>We present the results of the first strong lens time delay challenge. The motivation, experimental design, and entry level challenge are described in a companion paper. This paper presents the main challenge, TDC1, which consisted of analyzing thousands of simulated light curves blindly. The observational properties of the light curves cover the range in quality obtained for current targeted efforts (e.g., COSMOGRAIL) and expected from future synoptic surveys (e.g., LSST), and include simulated systematic errors. Seven teams participated in TDC1, submitting results from 78 different method variants. After describing each method, we compute and analyze basic statisticsmeasuring accuracy (or bias) A, goodness of fit chi(2), precision P, and success rate f. For some methods we identify outliers as an important issue. Other methods show that outliers can be controlled via visual inspection or conservative quality control. Several methods are competitive, i.e., give vertical bar A vertical bar < 0.03, P < 0.03, and chi(2) < 1.5, with some of the methods already reaching sub-percent accuracy. The fraction of light curves yielding a time delay measurement is typically in the range f = 20%-40%. It depends strongly on the quality of the data: COSMOGRAIL-quality cadence and light curve lengths yield significantly higher f than does sparser sampling. Taking the results of TDC1 at face value, we estimate that LSST should provide around 400 robust time-delay measurements, each with P < 0.03 and vertical bar A vertical bar < 0.01, comparable to current lens modeling uncertainties. In terms of observing strategies, we find that A and f depend mostly on season length, while P depends mostly on cadence and campaign duration.</P>
H0LiCOW VII: cosmic evolution of the correlation between black hole mass and host galaxy luminosity
Ding, Xuheng,Treu, Tommaso,Suyu, Sherry H.,Wong, Kenneth C.,Morishita, Takahiro,Park, Daeseong,Sluse, Dominique,Auger, Matthew W.,Agnello, Adriano,Bennert, Vardha N.,Collett, Thomas E. Oxford University Press 2017 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.472 No.1
ACTIVE GALACTIC NUCLEUS BLACK HOLE MASS ESTIMATES IN THE ERA OF TIME DOMAIN ASTRONOMY
Kelly, Brandon C.,Treu, Tommaso,Malkan, Matthew,Pancoast, Anna,Woo, Jong-Hak IOP Publishing 2013 The Astrophysical journal Vol.779 No.2
<P>We investigate the dependence of the normalization of the high-frequency part of the X-ray and optical power spectral densities (PSDs) on black hole mass for a sample of 39 active galactic nuclei (AGNs) with black hole masses estimated from reverberation mapping or dynamical modeling. We obtained new Swift observations of PG 1426+015, which has the largest estimated black hole mass of the AGNs in our sample. We develop a novel statistical method to estimate the PSD from a light curve of photon counts with arbitrary sampling, eliminating the need to bin a light curve to achieve Gaussian statistics, and we use this technique to estimate the X-ray variability parameters for the faint AGNs in our sample. We find that the normalization of the high-frequency X-ray PSD is inversely proportional to black hole mass. We discuss how to use this scaling relationship to obtain black hole mass estimates from the short timescale X-ray variability amplitude with precision similar to 0.38 dex. The amplitude of optical variability on timescales of days is also anticorrelated with black hole mass, but with larger scatter. Instead, the optical variability amplitude exhibits the strongest anticorrelation with luminosity. We conclude with a discussion of the implications of our results for estimating black hole mass from the amplitude of AGN variability.</P>
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>
Bennert, Vardha N.,Treu, Tommaso,Auger, Matthew W.,Cosens, Maren,Park, Daeseong,Rosen, Rebecca,Harris, Chelsea E.,Malkan, Matthew A.,Woo, Jong-Hak IOP Publishing 2015 The Astrophysical journal Vol.809 No.1
<P>We create a baseline of the black hole (BH) mass (M-BH)-stellar-velocity dispersion (sigma) relation for active galaxies, using a sample of 66 local (0.02 < z < 0.09) Seyfert-1 galaxies, selected from the Sloan Digital Sky Survey (SDSS). Analysis of SDSS images yields AGN luminosities free of host-galaxy contamination, and morphological classification. 51/66 galaxies have spiral morphology. Out of these, 28 bulges have Sersic index n < 2 and are considered candidate pseudo-bulges, with eight being definite pseudo-bulges based on multiple classification criteria met. Only 4/66 galaxies show signs of interaction/merging. High signal-to-noise ratio Keck spectra provide the width of the broad H beta emission line free of Fe II emission and stellar absorption. AGN luminosity and H beta line widths are used to estimate M-BH. The Keck-based spatially resolved kinematics is used to determine stellar-velocity dispersion within the spheroid effective radius (sigma(spat,reff)). We find that sigma can vary on average by up to 40% across definitions commonly used in the literature, emphasizing the importance of using self-consistent definitions in comparisons and evolutionary studies. The M-BH-sigma relation for our Seyfert-1 galaxy sample has the same intercept and scatter as that of reverberation-mapped AGNs as well as that of quiescent galaxies, consistent with the hypothesis that our single epoch M-BH estimator and sample selection function do not introduce significant biases. Barred galaxies, merging galaxies, and those hosting pseudo-bulges do not represent outliers in the M-BH-sigma relation. This is in contrast with previous work, although no firm conclusion can be drawn on this matter due to the small sample size and limited resolution of the SDSS images.</P>
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>
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 MASS OF THE BLACK HOLE IN Arp 151 FROM BAYESIAN MODELING OF REVERBERATION MAPPING DATA
Brewer, Brendon J.,Treu, Tommaso,Pancoast, Anna,Barth, Aaron J.,Bennert, Vardha N.,Bentz, Misty C.,Filippenko, Alexei V.,Greene, Jenny E.,Malkan, Matthew A.,Woo, Jong-Hak IOP Publishing 2011 ASTROPHYSICAL JOURNAL LETTERS - Vol.733 No.2
<P>Supermassive black holes are believed to be ubiquitous at the centers of galaxies. Measuring their masses is extremely challenging yet essential for understanding their role in the formation and evolution of cosmic structure. We present a direct measurement of the mass of a black hole in an active galactic nucleus (Arp 151) based on the motion of the gas responsible for the broad emission lines. By analyzing and modeling spectroscopic and photometric time series, we find that the gas is well described by a disk or torus with an average radius of 3.99 +/- 1.25 light days and an opening angle of 68.9(-17.2)(+21.4) deg, viewed at an inclination angle of 67.8 +/- 7.8 deg (that is, closer to face-on than edge-on). The black hole mass is inferred to be 10(6.51 +/- 0.28) M-circle dot. The method is fully general and can be used to determine the masses of black holes at arbitrary distances, enabling studies of their evolution over cosmic time.</P>
The Lick AGN Monitoring Project 2011: Dynamical Modeling of the Broad-line Region
Williams, Peter R.,Pancoast, Anna,Treu, Tommaso,Brewer, Brendon J.,Barth, Aaron J.,Bennert, Vardha N.,Buehler, Tabitha,Canalizo, Gabriela,Cenko, S. Bradley,Clubb, Kelsey I.,Cooper, Michael C.,Filippen American Astronomical Society 2018 The Astrophysical journal Vol.866 No.2