Publications (16)31.81 Total impact
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Article: The Structure of the Broad Line Region in AGN: I. Reconstructed Velocity-Delay Maps
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ABSTRACT: We present velocity-resolved reverberation results for five active galactic nuclei. We recovered velocity-delay maps using the maximum-entropy method for four objects: Mrk 335, Mrk 1501, 3C120, and PG2130+099. For the fifth, Mrk 6, we were only able to measure mean time delays in different velocity bins of the Hbeta emission line. The four velocity-delay maps show unique dynamical signatures for each object. For 3C120, the Balmer lines show kinematic signatures consistent with both an inclined disk and infalling gas, but the HeII 4686 emission line is suggestive only of inflow. The Balmer lines in Mrk 335, Mrk 1501, and PG 2130+099 show signs of infalling gas, but the HeII emission in Mrk 335 is consistent with an inclined disk. We also see tentative evidence of combined virial motion and infalling gas from the velocity-binned analysis of Mrk 6. The maps for 3C120 and Mrk 335 are two of the most clearly defined velocity-delay maps to date. These maps constitute a large increase in the number of objects for which we have resolved velocity-delay maps and provide evidence supporting the reliability of reverberation-based black hole mass measurements.10/2012; -
Article: Reverberation Mapping Results for Five Seyfert 1 Galaxies
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ABSTRACT: We present the results from a detailed analysis of photometric and spectrophotometric data on five Seyfert 1 galaxies observed as a part of a recent reverberation mapping program. The data were collected at several observatories over a 140-day span beginning in 2010 August and ending in 2011 January. We obtained high sampling-rate light curves for Mrk 335, Mrk 1501, 3C120, Mrk 6, and PG2130+099, from which we have measured the time lag between variations in the 5100 Angstrom continuum and the H-beta broad emission line. We then used these measurements to calculate the mass of the supermassive black hole at the center of each of these galaxies. Our new measurements substantially improve previous measurements of MBH and the size of the broad line-emitting region for four sources and add a measurement for one new object. Our new measurements are consistent with photoionization physics regulating the location of the broad line region in active galactic nuclei.06/2012; -
Article: The Infrared Light Curve of SN 2011fe in M101 and the Distance to M101
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ABSTRACT: We present near infra-red light curves of supernova (SN) 2011fe in M101, including 34 epochs in H band starting fourteen days before maximum brightness in the B-band. The light curve data were obtained with the WIYN High-Resolution Infrared Camera (WHIRC). When the data are calibrated using templates of other Type Ia SNe, we derive an apparent H-band magnitude at the epoch of B-band maximum of 10.85 \pm 0.04. This implies a distance modulus for M101 that ranges from 28.86 to 29.17 mag, depending on which absolute calibration for Type Ia SNe is used.05/2012; -
Article: A Reverberation Lag for the High-Ionization Component of the Broad Line Region in the Narrow-Line Seyfert 1 Mrk 335
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ABSTRACT: We present the first results from a detailed analysis of photometric and spectrophotometric data on the narrow-line Seyfert 1 galaxy Mrk 335, collected over a 120-day span in the fall of 2010. From these data we measure the lag in the He II 4686 broad emission line relative to the optical continuum to be 2.7 \pm 0.6 days and the lag in the H\beta 4861 broad emission line to be 13.9 \pm 0.9 days. Combined with the line width, the He II lag yields a black hole mass, MBH = (2.6 \pm 0.8)\times 10^7 Msun. This measurement is consistent with measurements made using the H\beta 4861 line, suggesting that the He II emission originates in the same region as H\beta, but at a much smaller radius. This constitutes the first robust lag measurement for a high-ionization line in a narrow-line Seyfert 1 galaxy.10/2011; -
Article: Reverberation Mapping Measurements of Black Hole Masses in Six Local Seyfert Galaxies
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ABSTRACT: We present the final results from a high sampling rate, multi-month, spectrophotometric reverberation mapping campaign undertaken to obtain either new or improved Hβ reverberation lag measurements for several relatively low-luminosity active galactic nuclei (AGNs). We have reliably measured the time delay between variations in the continuum and Hβ emission line in six local Seyfert 1 galaxies. These measurements are used to calculate the mass of the supermassive black hole at the center of each of these AGNs. We place our results in context to the most current calibration of the broad-line region (BLR) R BLR-L relationship, where our results remove outliers and reduce the scatter at the low-luminosity end of this relationship. We also present velocity-resolved Hβ time-delay measurements for our complete sample, though the clearest velocity-resolved kinematic signatures have already been published.The Astrophysical Journal 08/2010; 721(1):715. · 6.02 Impact Factor -
Article: Reverberation Mapping Results from MDM Observatory
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ABSTRACT: We present results from a multi-month reverberation mapping campaign undertaken primarily at MDM Observatory with supporting observations from around the world. We measure broad line region (BLR) radii and black hole masses for six objects. A velocity-resolved analysis of the H_beta response shows the presence of diverse kinematic signatures in the BLR. Comment: To appear in the Proceedings of the IAU Symposium No. 267: Co-Evolution of Central Black Holes and Galaxies, Rio de Janeiro, 200910/2009; -
Article: Diverse Kinematic Signatures from Reverberation Mapping of the Broad-Line Region in AGNs
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ABSTRACT: A detailed analysis of the data from a high sampling rate, multi-month reverberation mapping campaign, undertaken primarily at MDM Observatory with supporting observations from telescopes around the world, reveals that the Hβ emission region within the broad-line regions (BLRs) of several nearby active galactic nuclei (AGNs) exhibits a variety of kinematic behaviors. While the primary goal of this campaign was to obtain either new or improved Hβ reverberation lag measurements for several relatively low-luminosity AGNs, we were also able to unambiguously reconstruct velocity-resolved reverberation signals from a subset of our targets. Through high cadence spectroscopic monitoring of the optical continuum and broad Hβ emission-line variations observed in the nuclear regions of NGC 3227, NGC 3516, and NGC 5548, we clearly see evidence for outflowing, infalling, and virialized BLR gas motions, respectively.The Astrophysical Journal 09/2009; 704(2):L80. · 6.02 Impact Factor -
Article: A Revised Broad-line Region Radius and Black Hole Mass for the Narrow-line Seyfert 1 NGC 4051
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ABSTRACT: We present the first results from a high sampling rate, multimonth reverberation mapping campaign undertaken primarily at MDM Observatory with supporting observations from telescopes around the world. The primary goal of this campaign was to obtain either new or improved Hβ reverberation lag measurements for several relatively low luminosity active galactic nuclei (AGNs). We feature results for NGC 4051 here because, until now, this object has been a significant outlier from AGN scaling relationships, e.g., it was previously a ~2-3σ outlier on the relationship between the broad-line region (BLR) radius and the optical continuum luminosity—the R BLR-L relationship. Our new measurements of the lag time between variations in the continuum and Hβ emission line made from spectroscopic monitoring of NGC 4051 lead to a measured BLR radius of R BLR = 1.87+0.54 –0.50 light days and black hole mass of M BH = (1.73+0.55 –0.52) × 106 M ☉. This radius is consistent with that expected from the R BLR-L relationship, based on the present luminosity of NGC 4051 and the most current calibration of the relation by Bentz et al.. We also present a preliminary look at velocity-resolved Hβ light curves and time delay measurements, although we are unable to reconstruct an unambiguous velocity-resolved reverberation signal.The Astrophysical Journal 08/2009; 702(2):1353. · 6.02 Impact Factor -
Article: Diverse Broad Line Region Kinematic Signatures From Reverberation Mapping
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ABSTRACT: A detailed analysis of the data from a high sampling rate, multi-month reverberation mapping campaign, undertaken primarily at MDM Observatory with supporting observations from telescopes around the world, reveals that the Hbeta emission region within the broad line regions (BLRs) of several nearby AGNs exhibit a variety of kinematic behaviors. While the primary goal of this campaign was to obtain either new or improved Hbeta reverberation lag measurements for several relatively low luminosity AGNs (presented in a separate work), we were also able to unambiguously reconstruct velocity-resolved reverberation signals from a subset of our targets. Through high cadence spectroscopic monitoring of the optical continuum and broad Hbeta emission line variations observed in the nuclear regions of NGC 3227, NGC 3516, and NGC 5548, we clearly see evidence for outflowing, infalling, and virialized BLR gas motions, respectively.08/2009; -
Article: Strongly Variable z = 1.48 Fe II and Mg II Absorption in the Spectra of z = 4.05 GRB 060206
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ABSTRACT: We report on the discovery of strongly variable Fe II and Mg II absorption lines seen at z = 1.48 in the spectra of the z = 4.05 GRB 060206 obtained between 4.13 and 7.63 hr (observer frame) after the burst. In particular, the Fe II line equivalent width (EW) decayed rapidly from 1.72 ± 0.25 Å to 0.28 ± 0.21 Å, only to increase to 0.96 ± 0.21 Å in a later spectrum. The Mg II doublet shows even more complicated evolution: the weaker line of the doublet drops from 2.05 ± 0.25 Å to 0.92 ± 0.32 Å but then more than doubles to 2.47 ± 0.41 Å in later data. The ratio of the EWs for the Mg II doublet is also variable, being closer to 1 : 1 (saturated regime) when the lines are stronger and becoming closer to 2 : 1 (unsaturated regime) when the lines are weaker, consistent with expectations based on atomic physics. We have investigated and rejected the possibility of any instrumental or atmospheric effects causing the observed strong variations. Our discovery of clearly variable intervening Fe II and Mg II lines immediately indicates that the characteristic size of intervening patches of Mg II "clouds" is comparable to the GRB beam size, i.e., about 1016 cm. We discuss various implications of this discovery, including the nature of the Mg II absorbers, the physics of GRBs, and measurements of chemical abundances from GRB and quasar absorption lines.The Astrophysical Journal 12/2008; 659(2):L99. · 6.02 Impact Factor -
Article: The Mass of the Black Hole in the Quasar PG 2130+099
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ABSTRACT: We present the results of a recent reverberation-mapping campaign undertaken to improve measurements of the radius of the broad-line region and the central black hole mass of the quasar PG 2130+099. Cross-correlation of the 5100 Å continuum and Hβ emission-line light curves yields a time lag of 22.9−4.3+4.4 days, corresponding to a central black hole mass MBH = (3.8 ± 1.5) × 107 M☉. This value supports the notion that previous measurements yielded an incorrect lag. We reanalyze previous data sets to investigate the possible sources of the discrepancy and conclude that previous measurement errors were apparently caused by a combination of undersampling of the light curves and long-term secular changes in the Hβ emission-line equivalent width. With our new measurements, PG 2130+099 is no longer an outlier in either the RBLR-L or the MBH-σ* relationship.The Astrophysical Journal 12/2008; 688(2):837. · 6.02 Impact Factor -
Article: Dynamical Constraints on The Masses of the Nuclear Star Cluster and Black Hole in the Late-Type Spiral Galaxy NGC 3621
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ABSTRACT: NGC 3621 is a late-type (Sd) spiral galaxy with an active nucleus, previously detected through mid-infrared [Ne V] line emission. Archival Hubble Space Telescope (HST) images reveal that the galaxy contains a bright and compact nuclear star cluster. We present a new high-resolution optical spectrum of this nuclear cluster, obtained with the ESI Spectrograph at the Keck Observatory. The nucleus has a Seyfert 2 emission-line spectrum at optical wavelengths, supporting the hypothesis that a black hole is present. The line-of-sight stellar velocity dispersion of the cluster is sigma=43+/-3 km/s, one of the largest dispersions measured for any nuclear cluster in a late-type spiral galaxy. Combining this measurement with structural parameters measured from archival HST images, we carry out dynamical modeling based on the Jeans equation for a spherical star cluster containing a central point mass. The maximum black hole mass consistent with the measured stellar velocity dispersion is 3*10^6 solar masses. If the black hole mass is small compared with the cluster's stellar mass, then the dynamical models imply a total stellar mass of ~1*10^7 solar masses, which is consistent with rough estimates of the stellar mass based on photometric measurements from HST images. From structural decomposition of 2MASS images, we find no clear evidence for a bulge in NGC 3621; the galaxy contains at most a very faint and inconspicuous pseudobulge component (M_K>-17.6 mag). NGC 3621 provides one of the best demonstrations that very late-type spirals can host both active nuclei and nuclear star clusters, and that low-mass black holes can occur in disk galaxies even in the absence of a substantial bulge.10/2008; -
Article: An Offset Seyfert 2 Nucleus in the Minor Merger System NGC 3341
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ABSTRACT: We present the discovery of a triplet of emission-line nuclei in the disturbed disk galaxy NGC 3341, based on archival data from the Sloan Digital Sky Survey and new observations from the Keck Observatory. This galaxy contains two offset nuclei within or projected against its disk, at projected distances of 5.1 and 8.4 kpc from its primary nucleus and at radial velocity separation of less than 200 km/s from the primary. These appear to be either dwarf ellipticals or the bulges of low-mass spirals whose disks have already been stripped off while merging into the primary galaxy. The inner offset nucleus has a Seyfert 2 spectrum and a stellar velocity dispersion of 70+/-7 km/s. The outer offset nucleus has very weak emission lines consistent with a LINER classification, and the primary nucleus has an emission-line spectrum close to the boundary between LINER/HII composite systems and HII nuclei; both may contain accreting massive black holes, but the optical classifications alone are ambiguous. The detection of an offset active nucleus in NGC 3341 provides a strong suggestion that black hole accretion episodes during minor mergers can be triggered in the nuclei of dwarf secondary galaxies as well as in the primary. Comment: 4 pages, 3 figures. To appear in ApJ Letters07/2008; -
Article: Disparate MG II absorption statistics towards quasars and gamma-ray bursts: a possible explanation
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ABSTRACT: We examine the recent report by Prochter et al. that gamma-ray burst (GRB) sight lines have a much higher incidence of strong MgII absorption than quasar sight lines. We propose that the discrepancy is due to the different beam sizes of GRBs and quasars, and that the intervening MgII systems are clumpy with the dense part of each cloudlet of a similar size as the quasars, i.e. ≲1016cm, but bigger than GRBs. We also discuss observational predictions of our proposed model. Most notably, in some cases the intervening MgII absorbers in GRB spectra should be seen varying, and quasars with smaller sizes should show an increased rate of strong MgII absorbers. In fact, our prediction of variable MgII lines in the GRB spectra has been now confirmed by Hao et al., who observed intervening FeII and MgII lines at z=1.48 to be strongly variable in the multi-epoch spectra of z=4.05 GRB 060206.Astrophysics and Space Science 11/2007; 312(3):325-330. · 1.69 Impact Factor -
Article: Strongly Variable z=1.48 FeII and MgII Absorption in the Spectra of z=4.05 GRB 060206
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ABSTRACT: We report on the discovery of strongly variable FeII and MgII absorption lines seen at z=1.48 in the spectra of the z=4.05 GRB 060206 obtained between 4.13 to 7.63 hours (observer frame) after the burst. In particular, the FeII line equivalent width (EW) decayed rapidly from 1.72+-0.25 AA to 0.28+-0.21 AA, only to increase to 0.96+-0.21 AA in a later date spectrum. The MgII doublet shows even more complicated evolution: the weaker line of the doublet drops from 2.05+-0.25 AA to 0.92+-0.32 AA, but then more than doubles to 2.47+-0.41 AA in later data. The ratio of the EWs for the MgII doublet is also variable, being closer to 1:1 (saturated regime) when the lines are stronger and becoming closer to 2:1 (unsaturated regime) when the lines are weaker, consistent with expectations based on atomic physics. We have investigated and rejected the possibility of any instrumental or atmospheric effects causing the observed strong variations. Our discovery of clearly variable intervening FeII and MgII lines lends very strong support to their scenario, in which the characteristic size of intervening patches of MgII ``clouds'' is comparable to the GRB beam size, i.e, about 10^16 cm. We discuss various implications of this discovery, including the nature of the MgII absorbers, the physics of GRBs, and measurements of chemical abundances from GRB and quasar absorption lines. Comment: 14 pages, 3 figures, 1 table; ApJ Letters, accepted12/2006; -
Article: Are Quasars Bigger than Gamma-Ray Bursts? Explaining Disparate Absorption Statistics with Patchy MgII Absorbers<~ 10^ 16 cm in Size
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ABSTRACT: We examine the recent report by Prochter et al. that gamma-ray burst (GRB) sight lines have a much higher incidence of strong Mg II absorption than quasar sight lines. We give further evidence that this observed difference is not due to intervening dust extinction that would cause selection effects in the quasar sample. Instead, we propose that the difference is due to the different beam sizes of GRBs and quasars — that quasar beam sizes are, on average, about twice that of GRBs, and that the intervening Mg II systems are of a similar size, i.e. 10 16 cm. We also discuss some observational predictions of our proposed model. Most notably, in some cases the intervening Mg II absorbers in GRB spectra should be seen evolving, and quasars with smaller sizes should show an increased rate of Mg II absorbers.04/2006;
Top co-authors
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Institutions
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2006–2011
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The Ohio State University
- Department of Astronomy
Columbus, OH, USA
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2008
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University of California, Irvine
- Department of Physics and Astronomy
Irvine, CA, USA
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