Publications (45)
Major mergers are not the dominant trigger for high-accretion AGNs at z = 2
V. Marian, K. Jahnke, M. Mechtley +8
Research over the past decade has shown diminishing empirical evidence for major galaxy mergers being a dominating or even important mechanism for the growth of supermassive black…
A post-merger enhancement only in star-forming Type 2 Seyfert galaxies: the deep learning view
M. S. Avirett-Mackenzie, C. Villforth, M. Huertas-Company +7
Supermassive black holes require a reservoir of cold gas at the centre of their host galaxy in order to accrete and shine as active galactic nuclei (AGN). Major mergers have the ab…
Evidence for Merger-Driven Growth in Luminous, High-z, Obscured AGN in the CANDELS/COSMOS Field
J. L. Donley, J. Kartaltepe, D. Kocevski +27
While major mergers have long been proposed as a driver of both AGN activity and the M-sigma relation, studies of moderate to high redshift Seyfert-luminosity AGN hosts have found…
Do the Most Massive Black Holes at Grow via Major Mergers?
M. Mechtley, K. Jahnke, R. A. Windhorst +11
The most frequently proposed model for the origin of quasars holds that the high accretion rates seen in luminous active galactic nuclei are primarily triggered during major merger…
The first spectroscopic IR reverberation programme on Mrk 509
J. A. J. Mitchell, M. J. Ward, D. Kynoch +12
Near IR spectroscopic reverberation of Active Galactic Nuclei (AGN) potentially allows the infrared (IR) broad line region (BLR) to be reverberated alongside the disc and dust cont…
Continuum Reverberation Mapping of the Accretion Disks in Two Seyfert 1 Galaxies
M. M. Fausnaugh, D. A. Starkey, Keith Horne +69
We present optical continuum lags for two Seyfert 1 galaxies, MCG+08-11-011 and NGC 2617, using monitoring data from a reverberation mapping campaign carried out in 2014. Our light…
The 72-Hour WEBT Microvariability Observation of Blazar S5 0716+714 in 2009
G. Bhatta, J. R. Webb, H. Hollingsworth +42
Context. The international whole earth blazar telescope (WEBT) consortium planned and carried out three days of intensive micro-variability observations of S5 0716+714 from Februar…
A complete catalogue of merger fractions in AGN hosts: No evidence for an increase in detected merger fraction with AGN luminosity
C. Villforth
Despite the importance of Active Galactic Nuclei (AGN) in galaxy evolution, the mechanisms that fuel AGN activity remain poorly understood. Theoretical models suggest that major me…
Space Telescope and Optical Reverberation Mapping Project. I. Ultraviolet Observations of the Seyfert 1 Galaxy NGC 5548 with the Cosmic Origins Spectrograph on Hubble Space Telescope
G. De Rosa, B. M. Peterson, J. Ely +47
We describe the first results from a six-month long reverberation-mapping experiment in the ultraviolet based on 170 observations of the Seyfert 1 galaxy NGC 5548 with the Cosmic O…
A significant excess in major merger rate for AGNs with the highest Eddington ratios at z<0.2
V. Marian, K. Jahnke, I. Andika +16
Observational studies are increasingly finding evidence against major mergers being the dominant mechanism responsible for triggering AGN. After studying the connection between maj…
Variability and stability in blazar jets on time scales of years: Optical polarization monitoring of OJ287 in 2005-2009
C. Villforth, K. Nilsson, J. Heidt +45
(Abridged) OJ287 is a BL Lac object that has shown double-peaked bursts at regular intervals of ~12 yr during the last ~40 yr. We analyse optical photopolarimetric monitoring data…
TeV and Multi-wavelength Observations of Mrk 421 in 2006-2008
V. A. Acciari, E. Aliu, T. Arlen +103
We report on TeV gamma-ray observations of the blazar Mrk 421 (redshift of 0.031) with the VERITAS observatory and the Whipple 10m Cherenkov telescope. The excellent sensitivity of…
Long-term optical monitoring of TeV emitting Blazars
K. Nilsson, E. Lindfors, L. O. Takalo +17
We present 10 years of R-band monitoring data of 31 northern blazars which were either detected at very high energy (VHE) gamma rays or listed as potential VHE gamma-ray emitters.…
Space Telescope and Optical Reverberation Mapping Project. III. Optical Continuum Emission and Broad-Band Time Delays in NGC 5548
M. M. Fausnaugh, K. D. Denney, A. J. Barth +94
We present ground-based optical photometric monitoring data for NGC 5548, part of an extended multi-wavelength reverberation mapping campaign. The light curves have nearly daily ca…
Space Telescope and Optical Reverberation Mapping Project. IX. Velocity-Delay Maps for Broad Emission Lines in NGC 5548
Keith Horne, G. De Rosa, B. M. Peterson +155
We report velocity-delay maps for prominent broad emission lines, Ly_alpha, CIV, HeII and H_beta, in the spectrum of NGC5548. The emission-line responses inhabit the interior of a…
Shape asymmetry: a morphological indicator for automatic detection of galaxies in the post-coalescence merger stages
M. M. Pawlik, V. Wild, C. J. Walcher +5
We present a new morphological indicator designed for automated recognition of galaxies with faint asymmetric tidal features suggestive of an ongoing or past merger. We use this ne…
Host galaxies of luminous z0.6 quasars: Major mergers are not prevalent at the highest AGN luminosities
C. Villforth, T. Hamilton, M. M. Pawlik +10
Galaxy interactions are thought to be one of the main triggers of Active Galactic Nuclei (AGN), especially at high luminosities, where the accreted gas mass during the AGN lifetime…
The host galaxies of FeLoBAL quasars at z0.9 are not dominated by recent major mergers
C. Villforth, H. Herbst, F. Hamann +4
Theoretical models have suggested an evolutionary model for quasars, in which most of luminous quasars are triggered by major mergers. It is also postulated that reddening as well…
Linking the X-ray and infrared properties of star-forming galaxies at z<1.5
M. Symeonidis, A. Georgakakis, M. J. Page +16
We present the most complete study to date of the X-ray emission from star-formation in high redshift (median z=0.7; z<1.5), IR-luminous (L_IR=10^10-10^13 L_sun) galaxies detected…
The Host Galaxy of 3C 279
K. Nilsson, T. Pursimo, C. Villforth +2
We have obtained a deep i-band image of the blazar 3C 279 while the target was in a low optical state. Due to the faintness of the optical nucleus we have made the first detection…
Intranight polarization variability in radio-loud and radio-quiet AGN
C. Villforth, K. Nilsson, R. Ostensen +3
(Abriged) Intranight polarization variability in AGN has not been studied extensively so far. Studying the variability in polarization makes it possibly to distinguish between diff…
Variability and stability in optical blazar jets: the case of OJ287
C. Villforth, K. Nilsson, J. Heidt +1
OJ287 is a BL Lac object at redshift z=0.306 that has shown double-peaked bursts at regular intervals of ~12 yr during the last ~ 40 yr. Due to this behavior, it has been suggested…
Space Telescope and Optical Reverberation Mapping Project. XII. Broad-Line Region Modeling of NGC 5548
P. R. Williams, A. Pancoast, T. Treu +155
We present geometric and dynamical modeling of the broad line region for the multi-wavelength reverberation mapping campaign focused on NGC 5548 in 2014. The dataset includes photo…
Warm molecular and ionized gas kinematics in the Type-2 quasar J0945+1737
G. Speranza, C. Ramos Almeida, J. A. Acosta-Pulido +11
We analyze Near-Infrared Integral Field Spectrograph (NIFS) observations of the type-2 quasar (QSO2) SDSS J094521.33+173753.2 to investigate its warm molecular and ionized gas kine…
Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the UV anomaly in NGC 5548 with X-Ray Spectroscopy
S. Mathur, A. Gupta, K. Page +147
During the Space Telescope and Optical Reverberation Mapping Project (STORM) observations of NGC 5548, the continuum and emission-line variability became de-correlated during the s…
The host galaxies of X-ray selected Active Galactic Nuclei to z=2.5: Structure, star-formation and their relationships from CANDELS and Herschel/PACS
D. J. Rosario, D. H. McIntosh, A. van der Wel +60
We study the relationship between the structure and star-formation rate (SFR) of X-ray selected low and moderate luminosity active galactic nuclei (AGNs) in the two Chandra Deep Fi…
A systematic search for changing-look quasars in SDSS-II using difference spectra
B. Potts, C. Villforth
"Changing-look quasars" (CLQs) are active galactic nuclei (AGN) showing extreme variability that results in a transition from Type 1 to Type 2. The short timescales of these transi…
Echo mapping of the black hole accretion flow in NGC 7469
Raj Prince, Juan V. Hernández Santisteban, Keith Horne +20
Reverberation mapping (RM) can measure black hole accretion disc sizes and radial structure through observed time lags that should increase with wavelength as .…
Space Telescope and Optical Reverberation Mapping Project. VIII. Time Variability of Emission and Absorption in NGC 5548 Based on Modeling the Ultraviolet Spectrum
G. A. Kriss, G. De Rosa, J. Ely +164
We model the ultraviolet spectra of the Seyfert 1 galaxy NGC~5548 obtained with the Hubble Space Telescope during the 6-month reverberation-mapping campaign in 2014. Our model of t…
Delayed Appearance and Evolution of Coronal Lines in the TDE AT2019qiz
P. Short, A. Lawrence, M. Nicholl +17
Tidal disruption events (TDEs) occur when a star gets torn apart by a supermassive black hole as it crosses its tidal radius. We present late-time optical and X-ray observations of…
Morphologies of z~0.7 AGN Host Galaxies in CANDELS: No trend of merger incidence with AGN luminosity
C. Villforth, F. Hamann, D. J. Rosario +24
The processes that trigger Active Galactic Nuclei (AGN) remain poorly understood. While lower luminosity AGN may be triggered by minor disturbances to the host galaxy, stronger dis…
A massive binary black-hole system in OJ287 and a test of general relativity
M. J. Valtonen, H. J. Lehto, K. Nilsson +23
Tests of Einstein's general theory of relativity have mostly been carried out in weak gravitational fields where the space-time curvature effects are first-order deviations from Ne…
Space Telescope and Optical Reverberation Mapping Project VI: reverberating Disk Models for NGC 5548
D. Starkey, Keith Horne, M. M. Fausnaugh +90
We conduct a multiwavelength continuum variability study of the Seyfert 1 galaxy NGC 5548 to investigate the temperature structure of its accretion disk. The 19 overlapping continu…
Quasar Host Galaxies in the FORS Deep Field
C. Villforth, J. Heidt, K. Nilsson
(abriged)In this paper we study different properties of quasars and their host galaxies at high redshifts up to z~3.4. We compare our results to those of other authors and discuss…
The Black Hole Mass Function Across Cosmic Times II. Heavy Seeds and (Super)Massive Black Holes
A. Sicilia, A. Lapi, L. Boco +8
This is the second paper in a series aimed at modeling the black hole (BH) mass function, from the stellar to the (super)massive regime. In the present work we focus on (super)mass…
Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-Line Analysis for NGC 5548
L. Pei, M. M. Fausnaugh, A. J. Barth +153
We present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multi-wavelength reverberation mapping campaign. The campaign spanned s…
The Host Galaxies and Narrow Line Regions of Four Double-Peaked [OIII] AGN
C. Villforth, F. Hamann
Major gas-rich mergers of galaxies are expected to play an important role in triggering and fuelling luminous AGN. We present deep multi-band (u/r/z) imaging and long slit spectros…
The First Swift Intensive AGN Accretion Disk Reverberation Mapping Survey
R. Edelson, J. Gelbord, E. Cackett +32
Swift intensive accretion disk reverberation mapping of four AGN yielded light curves sampled 200-350 times in 0.3-10 keV X-ray and six UV/optical bands. Uniform reduction an…
Velocity-resolved reverberation mapping of five bright Seyfert 1 galaxies
G. De Rosa, M. M. Fausnaugh, C. J. Grier +99
We present the first results from a reverberation-mapping campaign undertaken during the first half of 2012, with additional data on one AGN (NGC 3227) from a 2014 campaign. Our ma…
Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation Mapping of the Accretion Disk of NGC 5548
R. Edelson, J. M. Gelbord, K. Horne +47
Recent intensive Swift monitoring of the Seyfert 1 galaxy NGC 5548 yielded 282 usable epochs over 125 days across six UV/optical bands and the X-rays. This is the densest extended…
The first spectroscopic dust reverberation programme on active galactic nuclei: the torus in NGC 5548
H. Landt, M. J. Ward, D. Kynoch +16
We have recently initiated the first spectroscopic dust reverberation programme on active galactic nuclei (AGN) in the near-infrared. Spectroscopy enables measurement of dust prope…
Reverberation Mapping of Optical Emission Lines in Five Active Galaxies
M. M. Fausnaugh, C. J. Grier, M. C. Bentz +68
We present the first results from an optical reverberation mapping campaign executed in 2014, targeting the active galactic nuclei (AGN) MCG+08-11-011, NGC 2617, NGC 4051, 3C 382,…
Space Telescope and Optical Reverberation Mapping Project. IV. Anomalous behavior of the broad ultraviolet emission lines in NGC 5548
M. R. Goad, K. T. Korista, G. De Rosa +99
During an intensive Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) UV monitoring campaign of the Seyfert~1 galaxy NGC 5548 performed from 2014 February to July, the…
Robotic Reverberation Mapping of Arp 151
S. Valenti, D. J. Sand, A. J. Barth +10
We present the first results from the Las Cumbres Observatory Global Telescope (LCOGT) Network's Active Galactic Nuclei Key Project, a large program devoted to using the robotic re…
Redshift constraints for RGB 0136+391 and PKS 0735+178 from deep optical imaging
K. Nilsson, T. Pursimo, C. Villforth +3
We present the results of deep I-band imaging of two BL Lacerate objects, RGB 0136+391 and PKS 0735+178, during an epoch when the optical nucleus was in a faint state in both targe…