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A Mid-IR Selected Changing-look Quasar and Physical Scenarios for Abrupt AGN Fading
Stern, Daniel,McKernan, Barry,Graham, Matthew J.,Ford, K. E. S.,Ross, Nicholas P.,Meisner, Aaron M.,Assef, Roberto J.,Baloković,, Mislav,Brightman, Murray,Dey, Arjun,Drake, Andrew,Djorgovski, S. American Astronomical Society 2018 The Astrophysical journal Vol.864 No.1
The Most Massive Active Galactic Nuclei at 1 ≲<i>z</i>≲ 2
Jun, Hyunsung D.,Im, Myungshin,Kim, Dohyeong,Stern, Daniel American Astronomical Society 2017 The Astrophysical journal Vol.838 No.1
<P>We obtained near-infrared spectra of 26 Sloan Digital Sky Survey quasars at 0.7 < z < 2.5 with reported rest-frame ultraviolet M-BH similar to 10(10) M-circle dot to critically examine the systematic effects involved with their mass estimations. We find that active galactic nuclei (AGNs) heavier than 10(10) M-circle dot often display double-peaked H alpha emission, extremely broad Fe II complex emission around Mg II, and highly blueshifted and broadened C IV emission. The weight of this evidence, combined with previous studies, cautions against the use of M-BH values based on any emission line with a width over 8000 km s(-1). Also, the M-BH estimations are not positively biased by the presence of ionized narrow line outflows, anisotropic radiation, or the use of line FWHM instead of sigma for our sample, and unbiased with variability, scatter in broad line equivalent width, or obscuration for general type-1 quasars. Removing the systematically uncertain M-BH values, similar to 10(10) M-circle dot black holes (BHs) in 1 less than or similar to z less than or similar to 2 Ns can still be explained by anisotropic motion of the broad line region from similar to 10(9.5) M-circle dot BHs, although current observations support that they are intrinsically most massive, and overmassive to the host's bulge mass.</P>
A new physical interpretation of optical and infrared variability in quasars
Ross, Nicholas P,Ford, K E Saavik,Graham, Matthew,McKernan, Barry,Stern, Daniel,Meisner, Aaron M,Assef, Roberto J,Dey, Arjun,Drake, Andrew J,Jun, Hyunsung D,Lang, Dustin Oxford University Press 2018 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.480 No.4
THE LICK AGN MONITORING PROJECT 2011: SPECTROSCOPIC CAMPAIGN AND EMISSION-LINE LIGHT CURVES
Barth, Aaron J.,Bennert, Vardha N.,Canalizo, Gabriela,Filippenko, Alexei V.,Gates, Elinor L.,Greene, Jenny E.,Li, Weidong,Malkan, Matthew A.,Pancoast, Anna,Sand, David J.,Stern, Daniel,Treu, Tommaso,W IOP Publishing 2015 The Astrophysical journal Supplement series Vol.217 No.2
<P>In the Spring of 2011 we carried out a 2.5 month reverberation mapping campaign using the 3 m Shane telescope at Lick Observatory, monitoring 15 low-redshift Seyfert 1 galaxies. This paper describes the observations, reductions and measurements, and data products from the spectroscopic campaign. The reduced spectra were fitted with a multicomponent model in order to isolate the contributions of various continuum and emission-line components. We present light curves of broad emission lines and the active galactic nucleus (AGN) continuum, and measurements of the broad H beta line widths in mean and rms spectra. For the most highly variable AGNs we also measured broad Ha line widths and velocity centroids from the nightly spectra. In four AGNs exhibiting the highest variability amplitudes, we detect anticorrelations between broad H beta width and luminosity, demonstrating that the broad-line region 'breathes' on short timescales of days to weeks in response to continuum variations. We also find that broad Ha velocity centroids can undergo substantial changes in response to continuum variations; in NGC 4593, the broad H beta velocity shifted by similar to 250 km s(-1) over a 1 month period. This reverberation-induced velocity shift effect is likely to contribute a significant source of confusion noise to binary black hole searches that use multi-epoch quasar spectroscopy to detect binary orbital motion. We also present results from simulations that examine biases that can occur in measurement of broad-line widths from rms spectra due to the contributions of continuum variations and photon-counting noise.</P>
Super-Eddington Accretion in the <i>WISE</i>-selected Extremely Luminous Infrared Galaxy W2246−0526
Tsai, Chao-Wei,Eisenhardt, Peter R. M.,Jun, Hyunsung D.,Wu, Jingwen,Assef, Roberto J.,Blain, Andrew W.,Dí,az-Santos, Tanio,Jones, Suzy F.,Stern, Daniel,Wright, Edward L.,Yeh, Sherry C. C. American Astronomical Society 2018 The Astrophysical journal Vol.868 No.1