arXiv subjects

Misty C. Bentz

Publications and source records attributed to Misty C. Bentz.

At least 55 records · Page 3Linked to original sources

arXiv2019

A Cepheid-Based Distance to the Seyfert Galaxy NGC 6814

We present a Cepheid-based distance to the nearby Seyfert galaxy NGC\,6814 from {\it Hubble Space Telescope} observations. We obtained F555W and F814W imaging over the course of 12 visits with logarithmic time spacing in 2013 August$-$October. We detected and made photometric measurements for 16,469 unique sources across all images in both filters, from which we identify 90 excellent Cepheid candidates spanning a range of periods of $13-84$ days. We find evidence for incompleteness in the detection of candidates at periods <21 days. Based on the analysis of Cepheid candidates above the incompleteness limit, we determine a distance modulus for NGC\,6814 relative to the LMC of $μ_{\rm rel\,LMC}=13.200^{+0.031}_{-0.031}$ mag. Adopting the recent constraint of the distance modulus to the LMC determined by Pietrzynski et al., we find $m-M=31.677^{+0.041}_{-0.041}$ which gives a distance of $21.65 \pm 0.41$ Mpc to NGC 6814.

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arXiv2019

HI Spectroscopy of Reverberation-Mapped Active Galactic Nuclei

We present HI 21 cm spectroscopy from the GBT for the host galaxies of 31 nearby AGNs with direct M$_{\textrm{BH}}$ measurements from reverberation mapping. These are the first published HI detections for 12 galaxies, and the spectral quality is generally an improvement over archival data for the remainder of the sample. We present measurements of emission-line fluxes, velocity widths, and recessional velocities from which we derive HI mass, total gas mass, and redshifts. Combining M$_{\textrm{GAS}}$ with constraints on M$_{\textrm{STARS}}$ allows exploration of the baryonic content of these galaxies. We find a typical M$_{\textrm{GAS}}$/M$_{\textrm{STARS}}$ fraction of 10%, with a few reaching $\sim$30-50%. We also examined several relationships between M$_{\textrm{STARS}}$, M$_{\textrm{GAS}}$, M$_{\textrm{BH}}$, baryonic mass, and morphological type. We find a weak preference for galaxies with larger M$_{\textrm{GAS}}$ to host more massive black holes. We also find gas-to-stellar fractions to weakly correlate with later types in unbarred spirals, with an approximately constant fraction for barred spirals. Consistent with previous studies, we find declining M$_{\textrm{GAS}}$/M$_{\textrm{STARS}}$ with increasing M$_{\textrm{STARS}}$, with a slope suggesting the gas reservoirs have been replenished. Finally, we find a clear relationship for M$_{\textrm{BH}}$-M$_{\textrm{BARY}}$ with a similar slope as M$_{\textrm{BH}}$-M$_{\textrm{STARS}}$ reported by Bentz & Manne-Nicholas (2018). The dwarf Seyfert NGC 4395 appears to follow this relationship as well, even though it has a significantly higher gas fraction and smaller M$_{\textrm{BH}}$ than the remainder of our sample.

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arXiv2018

Black Hole - Galaxy Scaling Relationships for Active Galactic Nuclei with Reverberation Masses

We have utilized high-resolution optical Hubble Space Telescope images and deep, ground-based near-infrared images to examine the host-galaxies of 37 active galactic nuclei with reverberation-based black hole masses. Using two-dimensional image decompositions, we have separated the host galaxy from the bright central AGN, allowing a re-examination of the MBH-Lbulge and MBH-Lgalaxy relationships and the MBH-Mbulge and MBH-Mstars relationships using V-H color to constrain the stellar mass-to-light ratio. We find clear correlations for all of these scaling relationships, and the best-fit correlations are generally in good agreement with the sample of early-type galaxies with MBH from dynamical modeling and the sample of megamasers. We also find good agreement with the expectations from the Illustris simulations, although the agreement with other simulations is less clear because of the different black hole mass ranges that are probed. MBH-Lbulge is found to have the least scatter, and is therefore the best predictor of MBH among the relationships examined here. Large photometric surveys that rely on automated analysis and forego bulge-to-disk decompositions will achieve more accurate MBH predictions if they rely on MBH-Mstars rather than MBH-Lgalaxy. Finally, we have examined MBH/Mstars and find a clear trend with black hole mass but not galaxy mass. This same trend is also exhibited by galaxies with MBH from dynamical modeling and megamaser galaxies, as well as simulated galaxies from Illustris, rising from ~0.01% at 10^6 Msun to ~1.0% at 10^10 Msun. This scaling should be taken into account when comparing galaxy samples that are not matched in MBH.

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arXiv2017

Recalibration of the $M_{BH}-σ_{\star}$ Relation for AGN

We present a re-calibration of the $M_{BH}-σ_{\star}$ relation, based on a sample of 16 reverberation-mapped galaxies with newly determined bulge stellar velocity dispersions ($σ_{\star}$) from integral-field spectroscopy (IFS), and a sample of 32 quiescent galaxies with publicly available IFS. For both samples, $σ_{\star}$ is determined via two different methods that are popular in the literature, and we provide fits for each sample based on both sets of $σ_{\star}$. We find the fit to the AGN sample is shallower than the fit to the quiescent galaxy sample, and that the slopes for each sample are in agreement with previous investigations. However, the intercepts to the quiescent galaxy relations are notably higher than those found in previous studies, due to the systematically lower $σ_{\star}$ measurements that we obtain from IFS. We find that this may be driven, in part, by poorly constrained measurements of bulge effective radius ($r_{e}$) for the quiescent galaxy sample, which may bias the $σ_{\star}$ measurements low. We use these quiescent galaxy parameterizations, as well as one from the literature, to recalculate the virial scaling factor $f$. We assess the potential biases in each measurement, and suggest $f=4.82\pm1.67$ as the best currently available estimate. However, we caution that the details of how $σ_{\star}$ is measured can significantly affect $f$, and there is still much room for improvement.

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arXiv2016

The BRAVE Program - I: Improved Bulge Stellar Velocity Dispersion Estimates for a Sample of Active Galaxies

We present new bulge stellar velocity dispersion measurements for 10 active galaxies with secure $M_{BH}$ determinations from reverberation-mapping. These new velocity dispersion measurements are based on spatially resolved kinematics from integral-field (IFU) spectroscopy. In all but one case, the field of view of the IFU extends beyond the effective radius of the galaxy, and in the case of Mrk 79 the field of view extends to almost one half the effective radius. This combination of spatial resolution and field of view allows for secure determinations of stellar velocity dispersion within the effective radius for all 10 target galaxies. Spatially resolved maps of the first (V) and second ($σ_{\star}$) moments of the line-of-sight velocity distribution (LOSVD) indicate the presence of kinematic substructure in most cases. In future projects we plan to explore methods of correcting for the effects of kinematic substructure in the derived bulge stellar velocity dispersion measurements.

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arXiv2016

A Low-Mass Black Hole in the Nearby Seyfert Galaxy UGC 06728

We present the results of a recent reverberation mapping campaign for UGC 06728, a nearby low-luminosity Seyfert 1 in a late-type galaxy. Nightly monitoring in the spring of 2015 allowed us to determine an H$β$ time delay of $τ= 1.4 \pm 0.8$ days. Combined with the width of the variable H$β$ line profile, we determine a black hole mass of $M_{\rm BH} = (7.1 \pm 4.0) \times 10^5$ M$_{\odot}$. We also constrain the bulge stellar velocity dispersion from higher-resolution long slit spectroscopy along the galaxy minor axis and find $σ_{\star} = 51.6 \pm 4.9$ km s$^{-1}$. The measurements presented here are in good agreement with both the $R_{\rm BLR} - L$ relationship and the $M_{\rm BH}-σ_{\star}$ relationship for AGNs. Combined with a previously published spin measurement, our mass determination for UGC 06728 makes it the lowest-mass black hole that has been fully characterized, and thus an important object to help anchor the low-mass end of black hole evolutionary models.

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arXiv2016

A Reverberation-Based Black Hole Mass for MCG-06-30-15

We present the results of a reverberation campaign targeting MGC-06-30-15. Spectrophotometric monitoring and broad-band photometric monitoring over the course of 4 months in the spring of 2012 allowed a determination of a time delay in the broad H$β$ emission line of $τ=5.3\pm1.8$ days in the rest frame of the AGN. Combined with the width of the variable portion of the emission line, we determine a black hole mass of $M_{\rm BH} = (1.6 \pm 0.4) \times 10^6$ M$_{\odot}$. Both the H$β$ time delay and the black hole mass are in good agreement with expectations from the $R_{\rm BLR}$-$L$ and $M_{\rm BH}-σ_{\star}$ relationships for other reverberation-mapped AGNs. The H$β$ time delay is also in good agreement with the relationship between H$β$ and broad-band near-IR delays, in which the effective BLR size is $\sim 4-5$ times smaller than the inner edge of the dust torus. Additionally, the reverberation-based mass is in good agreement with estimates from the X-ray power spectral density break scaling relationship, and with constraints based on stellar kinematics derived from integral field spectroscopy of the inner $\sim 0.5$ kpc of the galaxy.

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arXiv2015

Constraints on the broad line region from regularized linear inversion: Velocity-delay maps for five nearby active galactic nuclei

Reverberation mapping probes the structure of the broad emission-line region (BLR) in active galactic nuclei (AGN). The kinematics of the BLR gas can be used to measure the mass of the central supermassive black hole. The main uncertainty affecting black hole mass determinations is the structure of the BLR. We present a new method for reverberation mapping based on regularized linear inversion (RLI) that includes modelling of the AGN continuum light curves. This enables fast calculation of velocity-resolved response maps to constrain BLR structure. RLI allows for negative response, such as when some areas of the BLR respond in inverse proportion to a change in ionizing continuum luminosity. We present time delays, integrated response functions, and velocity-delay maps for the $\rm{H}\,β$ broad emission line in five nearby AGN, as well as for $\rm{H}\,α$ and $\rm{H}\,γ$ in Arp 151, using data from the Lick AGN Monitoring Project 2008. We find indications of prompt response in three of the objects (Arp 151, NGC 5548 and SBS 1116+583A) with additional prompt response in the red wing of $\rm{H}\,β$. In SBS 1116+583A we find evidence for a multimodal broad prompt response followed by a second narrow response at 10 days. We find no clear indications of negative response. The results are complementary to, and consistent with, other methods such as cross correlation, maximum entropy and dynamical modelling. Regularized linear inversion with continuum light curve modelling provides a fast, complementary method for velocity-resolved reverberation mapping and is suitable for use on large datasets.

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arXiv2015

AGN Reverberation Mapping

Reverberation mapping is now a well-established technique for investigating spatially-unresolved structures in the nuclei of distant galaxies with actively-accreting supermassive black holes. Structural parameters for the broad emission-line region, with angular sizes of microarcseconds, can be constrained through the substitution of time resolution for spatial resolution. Many reverberation experiments over the last 30 years have led to a practical understanding of the requirements necessary for a successful program. With reverberation measurements now in hand for 60 active galaxies, and more on the horizon, we are able to directly constrain black hole masses, derive scaling relationships that allow large numbers of black hole mass estimates throughout the observable Universe, and begin investigating the detailed geometry and kinematics of the broad line region. Reverberation mapping is therefore one of the few techniques available that will allow a deeper understanding of the physical mechanisms involved in AGN feeding and feedback at very small scales, as well as constraints on the growth and evolution of black holes across cosmic time. In this contribution, I will briefly review the background, implementation, and major results derived from this high angular resolution technique.

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arXiv2015

Modeling reverberation mapping data II: dynamical modeling of the Lick AGN Monitoring Project 2008 dataset

We present dynamical modeling of the broad line region (BLR) for a sample of five Seyfert 1 galaxies using reverberation mapping data taken by the Lick AGN Monitoring Project in 2008. By modeling the AGN continuum light curve and H$β$ line profiles directly we are able to constrain the geometry and kinematics of the BLR and make a measurement of the black hole mass that does not depend upon the virial factor, $f$, needed in traditional reverberation mapping analysis. We find that the geometry of the BLR is generally a thick disk viewed close to face-on. While the H$β$ emission is found to come preferentially from the far side of the BLR, the mean size of the BLR is consistent with the lags measured with cross-correlation analysis. The BLR kinematics are found to be consistent with either inflowing motions or elliptical orbits, often with some combination of the two. We measure black hole masses of $\log_{10}(M_{\rm\,BH}/M_\odot)=6.62^{+0.10}_{-0.13}$ for Arp 151, $7.42^{+0.26}_{-0.27}$ for Mrk 1310, $7.51^{+0.23}_{-0.14}$ for NGC 5548, $6.42^{+0.24}_{-0.18}$ for NGC 6814, and $6.99^{+0.32}_{-0.25}$ for SBS 1116+583A. The $f$ factors measured individually for each AGN are found to correlate with inclination angle, although not with $M_{\rm\,BH}$, $L_{5100}$, or FWHM/$σ$ of the emission line profile.

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arXiv2014

The AGN Black Hole Mass Database

The AGN Black Hole Mass Database is a compilation of all published spectroscopic reverberation-mapping studies of active galaxies. We have created a public web interface, where users may get the most up-to-date black hole masses from reverberation mapping for any particular active galactic nucleus (AGN), as well as obtain the individual measurements upon which the masses are based and the appropriate references. While the database currently focuses on the measurements necessary for black hole mass determinations, we also plan to expand it in the future to include additional useful information, such as host-galaxy characteristics. New reverberation mapping results will also be incorporated into the database as they are published in peer-refereed journals.

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arXiv2014

The Mass of the Central Black Hole in the Nearby Seyfert Galaxy NGC5273

We present the results of a reverberation-mapping program targeting NGC5273, a nearby early-type galaxy with a broad-lined active galactic nucleus. Over the course of the monitoring program, NGC5273 showed strong variability that allowed us to measure time delays in the responses of the broad optical recombination lines to changes in the continuum flux. A weighted average of these measurements results in a black hole mass determination of $M_{\rm BH} = (4.7 \pm 1.6) \times 10^6$ M$_{\odot}$. An estimate of the size of the black hole sphere of influence in NGC5273 puts it just at the limit of the resolution achievable with current ground-based large aperture telescopes. NGC5273 is therefore an important future target for a black hole mass determination from stellar dynamical modeling, especially because it is the only nearby early-type galaxy hosting an AGN with a reverberation-based mass, allowing the best comparison for the masses determined from these two techniques.

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arXiv2014

The Black Hole Mass of NGC 4151. II. Stellar Dynamical Measurement from Near-Infrared Integral Field Spectroscopy

We present a revised measurement of the mass of the central black hole (Mbh) in the Seyfert 1 galaxy NGC 4151. The new stellar dynamical mass measurement is derived by applying an axisymmetric orbit-superposition code to near-infrared integral field data obtained using adaptive optics with the Gemini NIFS spectrograph. When our models attempt to fit both the NIFS kinematics and additional low spatial resolution kinematics, our results depend sensitively on how chi-squared is computed--probably a consequence of complex bar kinematics that manifest immediately outside the nuclear region. The most robust results are obtained when only the high spatial resolution kinematic constraints in the nuclear region are included in the fit. Our best estimates for the BH mass and H-band mass-to-light ratio are Mbh~(3.76+/-1.15)E7 Msun (1-sigma error) and M/L(H-band)~0.34+/-0.03 Msun/Lsun (3-sigma error), respectively (the quoted errors reflect the model uncertainties). Our BH mass measurement is consistent with estimates from both reverberation mapping (3.57[+0.45/-0.37]E7 Msun) and gas kinematics (3.0[+0.75/-2.2]E7 Msun; 1-sigma errors), and our best-fit mass-to-light ratio is consistent with the photometric estimate of M/L(H-band)=0.4+/-0.2 Msun/Lsun. The NIFS kinematics give a central bulge velocity dispersion sigma_c=116+/-3 km/s, bringing this object slightly closer to the M-sigma relation for quiescent galaxies. Although NGC 4151 is one of only a few Seyfert 1 galaxies in which it is possible to obtain a direct dynamical BH mass measurement--and thus, an independent calibration of the reverberation mapping mass scale--the complex bar kinematics makes it less than ideally suited for this purpose.

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arXiv2013

Further Evidence for a Supermassive Black Hole Mass - Pitch Angle Relation

We present new and stronger evidence for a previously reported relationship between galactic spiral arm pitch angle P (a measure of the tightness of spiral structure) and the mass M_BH of a disk galaxy's nuclear supermassive black hole (SMBH). We use an improved method to accurately measure the spiral arm pitch angle in disk galaxies to generate quantitative data on this morphological feature for 34 galaxies with directly measured black hole masses. We find a relation of log(M/M_sun) = (8.21 +/- 0.16) - (0.062 +/- 0.009)P. This method is compared with other means of estimating black hole mass to determine its effectiveness and usefulness relative to other existing relations. We argue that such a relationship is predicted by leading theories of spiral structure in disk galaxies, including the density wave theory. We propose this relationship as a tool for estimating SMBH masses in disk galaxies. This tool is potentially superior when compared to other methods for this class of galaxy and has the advantage of being unambiguously measurable from imaging data alone.

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arXiv2013

A near-infrared relationship for estimating black hole masses in active galactic nuclei

Black hole masses for samples of active galactic nuclei (AGN) are currently estimated from single-epoch optical spectra using scaling relations anchored in reverberation mapping results. In particular, the two quantities needed for calculating black hole masses, namely, the velocity and the radial distance of the orbiting gas are derived from the widths of the Balmer hydrogen broad emission lines and the optical continuum luminosity, respectively. We have recently presented a near-infrared (near-IR) relationship for estimating AGN black hole masses based on the widths of the Paschen hydrogen broad emission lines and the total 1 micron continuum luminosity. The near-IR offers several advantages over the optical: it suffers less from dust extinction, the AGN continuum is observed only weakly contaminated by the host galaxy and the strongest Paschen broad emission lines Pa alpha and Pa beta are unblended. Here we improve the calibration of the near-IR black hole mass relationship by increasing the sample from 14 to 23 reverberation-mapped AGN using additional spectroscopy obtained with the Gemini Near-Infrared Spectrograph (GNIRS). The additional sample improves the number statistics in particular at the high luminosity end.

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arXiv2013

The Low-Luminosity End of the Radius-Luminosity Relationship for Active Galactic Nuclei

We present an updated and revised analysis of the relationship between the Hbeta broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of 9 new AGNs imaged with the Hubble Space Telescope Wide Field Camera 3. The surface brightness decompositions allow us to create "AGN-free" images of the galaxies, from which we measure the starlight contribution to the optical luminosity measured through the ground-based spectroscopic aperture. We also incorporate 20 new reverberation-mapping measurements of the Hbeta time lag, which is assumed to yield the average Hbeta BLR radius. The final sample includes 41 AGNs covering four orders of magnitude in luminosity. The additions and updates incorporated here primarily affect the low-luminosity end of the R-L relationship. The best fit to the relationship using a Bayesian analysis finds a slope of alpha = 0.533 (+0.035/-0.033), consistent with previous work and with simple photoionization arguments. Only two AGNs appear to be outliers from the relationship, but both of them have monitoring light curves that raise doubt regarding the accuracy of their reported time lags. The scatter around the relationship is found to be 0.19(+/-0.02) dex, but would be decreased to 0.13 dex by the removal of these two suspect measurements. A large fraction of the remaining scatter in the relationship is likely due to the inaccurate distances to the AGN host galaxies. Our results help support the possibility that the R-L relationship could potentially be used to turn the BLRs of AGNs into standardizable candles. This would allow the cosmological expansion of the Universe to be probed by a separate population of objects, and over a larger range of redshifts.

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arXiv2012

Optical Monitoring of the Broad-Line Radio Galaxy 3C390.3

We have undertaken a new ground-based monitoring campaign on the BLRG 3C390.3 to improve the measurement of the size of the BLR and to estimate the black hole mass. Optical spectra and g-band images were observed in 2005 using the 2.4m telescope at MDM Observatory. Integrated emission-line flux variations were measured for Ha, Hb, Hg, and for HeII4686, as well as g-band fluxes and the optical AGN continuum at 5100A. The g-band fluxes and the AGN continuum vary simultaneously within the uncertainties, tau=(0.2+-1.1)days. We find that the emission-line variations are delayed with respect to the variable g-band continuum by tau(Ha)=56.3(+2.4-6.6)days, tau(Hb)=44.3(+3.0_-3.3)days, tau(Hg)=58.1(+4.3-6.1)days, and tau(HeII4686)=22.3(+6.5-3.8)days. The blue and red peak in the double peaked line profiles, as well as the blue and red outer profile wings, vary simultaneously within +-3 days. This provides strong support for gravitationally bound orbital motion of the dominant part of the line emitting gas. Combining the time delay of Ha and Hb and the separation of the blue and red peak in the broad double-peaked profiles in their rms spectra, we determine Mbh_vir=1.77(+0.29-0.31)x10^8Msol and using sigma_line of the rms spectra Mbh_vir=2.60(+0.23-0.31)x10^8Msol for the central black hole of 3C390.3, respectively. Using the inclination angle of the line emitting region the mass of the black hole amounts to Mbh=0.86(+0.19-0.18)x10^9 Msol (peak-separation) and Mbh=1.26(+0.21-0.16)x10^9 Msol (sigma_line), respectively. This result is consistent with the black hole masses indicated by simple accretion disk models to describe the observed double-peaked profiles, derived from the stellar dynamics of 3C390.3, and with the AGN radius-luminosity relation. Thus, 3C390.3 as a radio-loud AGN with a low Eddington ratio, Ledd/Lbol=0.02, follows the same AGN radius-luminosity relation as radio-quiet AGN.

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arXiv2011

The Lick AGN Monitoring Project: Recalibrating Single-Epoch Virial Black Hole Mass Estimates

We investigate the calibration and uncertainties of black hole mass estimates based on the single-epoch (SE) method, using homogeneous and high-quality multi-epoch spectra obtained by the Lick Active Galactic Nucleus (AGN) Monitoring Project for 9 local Seyfert 1 galaxies with black hole masses < 10^8 M_sun. By decomposing the spectra into their AGN and stellar components, we study the variability of the single-epoch Hbeta line width (full width at half-maximum intensity, FWHM_Hbeta; or dispersion, sigma_Hbeta) and of the AGN continuum luminosity at 5100A (L_5100). From the distribution of the "virial products" (~ FWHM_Hbeta^2 L_5100^0.5 or sigma_Hbeta^2 L_5100^0.5) measured from SE spectra, we estimate the uncertainty due to the combined variability as ~ 0.05 dex (12%). This is subdominant with respect to the total uncertainty in SE mass estimates, which is dominated by uncertainties in the size-luminosity relation and virial coefficient, and is estimated to be ~ 0.46 dex (factor of ~ 3). By comparing the Hbeta line profile of the SE, mean, and root-mean-square (rms) spectra, we find that the Hbeta line is broader in the mean (and SE) spectra than in the rms spectra by ~ 0.1 dex (25%) for our sample with FWHM_Hbeta < 3000 km/s. This result is at variance with larger mass black holes where the difference is typically found to be much less than 0.1 dex. To correct for this systematic difference of the Hbeta line profile, we introduce a line-width dependent virial factor, resulting in a recalibration of SE black hole mass estimators for low-mass AGNs.

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