arXiv subjects

Misty C. Bentz

Publications and source records attributed to Misty C. Bentz.

At least 37 records · Page 2Linked to original sources

arXiv2023

AGN STORM 2. III. A NICER view of the variable X-ray obscurer in Mrk 817

The AGN STORM 2 collaboration targeted the Seyfert 1 galaxy Mrk 817 for a year-long multiwavelength, coordinated reverberation mapping campaign including HST, Swift, XMM-Newton, NICER, and ground-based observatories. Early observations with NICER and XMM revealed an X-ray state ten times fainter than historical observations, consistent with the presence of a new dust-free, ionized obscurer. The following analysis of NICER spectra attributes variability in the observed X-ray flux to changes in both the column density of the obscurer by at least one order of magnitude ($N_\mathrm{H}$ ranges from $2.85\substack{+0.48\\ -0.33} \times 10^{22}\text{ cm}^{-2}$ to $25.6\substack{+3.0\\ -3.5} \times 10^{22} \text{ cm}^{-2}$) and the intrinsic continuum brightness (the unobscured flux ranges from $10^{-11.8}$ to $10^{-10.5}$ erg s$^{-1}$ cm$^{-2}$ ). While the X-ray flux generally remains in a faint state, there is one large flare during which Mrk 817 returns to its historical mean flux. The obscuring gas is still present at lower column density during the flare but it also becomes highly ionized, increasing its transparency. Correlation between the column density of the X-ray obscurer and the strength of UV broad absorption lines suggests that the X-ray and UV continua are both affected by the same obscuration, consistent with a clumpy disk wind launched from the inner broad line region.

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arXiv2023

AGN STORM 2: II. Ultraviolet Observations of Mrk817 with the Cosmic Origins Spectrograph on the Hubble Space Telescope

We present reverberation mapping measurements for the prominent ultraviolet broad emission lines of the active galactic nucleus Mrk817 using 165 spectra obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. Our ultraviolet observations are accompanied by X-ray, optical, and near-infrared observations as part of the AGN Space Telescope and Optical Reverberation Mapping Program 2 (AGN STORM 2). Using the cross-correlation lag analysis method, we find significant correlated variations in the continuum and emission-line light curves. We measure rest-frame delayed responses between the far-ultraviolet continuum at 1180 A and Ly$α$ $\lambda1215$ A ($10.4_{-1.4}^{+1.6}$ days), N V $\lambda1240$ A ($15.5_{-4.8}^{+1.0}$days), SiIV + OIV] $\lambda1397$ A ($8.2_{-1.4}^{+1.4}$ days), CIV $\lambda1549$ A ($11.8_{-2.8}^{+3.0}$ days), and HeII $\lambda1640$ A ($9.0_{-1.9}^{+4.5}$ days) using segments of the emission-line profile that are unaffected by absorption and blending, which results in sampling different velocity ranges for each line. However, we find that the emission-line responses to continuum variations are more complex than a simple smoothed, shifted, and scaled version of the continuum light curve. We also measure velocity-resolved lags for the Ly$α$, and CIV emission lines. The lag profile in the blue wing of Ly$α$ is consistent with virial motion, with longer lags dominating at lower velocities, and shorter lags at higher velocities. The CIV lag profile shows the signature of a thick rotating disk, with the shortest lags in the wings, local peaks at $\pm$ 1500 $\rm km\,s^{-1}$, and a local minimum at line center. The other emission lines are dominated by broad absorption lines and blending with adjacent emission lines. These require detailed models, and will be presented in future work.

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arXiv2022

Reverberation Mapping of IC4329A

We present the results of a new reverberation mapping campaign for the broad-lined active galactic nucleus (AGN) in the edge-on spiral IC4329A. Monitoring of the optical continuum with $V-$band photometry and broad emission-line flux variability with moderate-resolution spectroscopy allowed emission-line light curves to be measured for H$β$, H$γ$, and HeII $λ4686$. We find a time delay of $16.3^{+2.6}_{-2.3}$ days for H$β$, a similar time delay of $16.0^{+4.8}_{-2.6}$ days for H$γ$, and an unresolved time delay of $-0.6^{+3.9}_{-3.9}$ days for HeII. The time delay for H$β$ is consistent with the predicted value from the relationship between AGN luminosity and broad line region radius, after correction for the $\sim2.4$mag of intrinsic extinction at 5100A. Combining the measured time delay for H$β$ with the broad emission line width and an adopted value of $\langle f \rangle = 4.8$, we find a central supermassive black hole mass of $M_{\rm BH}=6.8^{+1.2}_{-1.1}\times10^7 M_{\rm \odot}$. Velocity-resolved time delays were measured across the broad H$β$ emission-line profile and may be consistent with an ''M''-like shape. Modeling of the full reverberation response of H$β$ was able to provide only modest constraints on some parameters, but does exhibit agreement with the black hole mass and average time delay. The models also suggest that the AGN structure is misaligned by a large amount from the edge-on galaxy disk. This is consistent with expectations from the unified model of AGNs, in which broad emission lines are expected to be visible only for AGNs that are viewed at relatively face-on inclinations.

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arXiv2022

The Mass of the Black Hole in NGC 5273 from Stellar Dynamical Modeling

We present a new constraint on the mass of the black hole in the active S0 galaxy NGC 5273. Due to the proximity of the galaxy at $16.6 \pm 2.1$ Mpc, we were able to resolve and extract the bulk motions of stars near the central black hole using AO-assisted observations with Gemini NIFS, as well as constrain the large-scale kinematics using re-reduced archival SAURON spectroscopy. High resolution HST imaging allowed us to generate a surface brightness decomposition, determine approximate mass-to-light ratios for the bulge and disk, and obtain an estimate for the disk inclination. We constructed an extensive library of dynamical models using the Schwarzschild orbit-superposition code FORSTAND, exploring a range of disk and bulge shapes, halo masses, etc. We determined a black hole mass of $M_{\bullet} = [0.5 - 2] \times 10^{7}$ $M_{\odot}$, where the low side of the range is in agreement with the reverberation mapping measurement of $M_{\bullet} = [4.7 \pm 1.6] \times 10^{6}$ $M_{\odot}$. NGC 5273 is one of only a small number of nearby galaxies hosting broad-lined AGN, allowing crucial comparison of the black hole masses derived from different mass measurement techniques.

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arXiv2022

The Broad Line Region and Black Hole Mass of NGC 4151

We present a reanalysis of reverberation-mapping data from 2005 for the Seyfert galaxy NGC 4151, supplemented with additional data from the literature to constrain the continuum variations over a significantly longer baseline than the original monitoring program. Modeling of the continuum light curve and the velocity-resolved variations across the H$β$ emission line constrains the geometry and kinematics of the broad line region (BLR). The BLR is well described by a very thick disk with similar opening angle ($θ_o \approx 57^{\circ}$) and inclination angle ($θ_i \approx 58^{\circ}$), suggesting that our sight line towards the innermost central engine skims just above the surface of the BLR. The inclination is consistent with constraints from geometric modeling of the narrow line region, and the similarity between the inclination and opening angles is intriguing given previous studies of NGC 4151 that suggest BLR gas has been observed temporarily eclipsing the X-ray source. The BLR kinematics are dominated by eccentric bound orbits, with $\sim10$% of the orbits preferring near-circular motions. With the BLR geometry and kinematics constrained, the models provide an independent and direct black hole mass measurement of $\log M_{\rm BH}/M_{\odot} = 7.22^{+0.11}_{-0.10}$ or $M_{\rm BH}=1.66^{+0.48}_{-0.34}\times10^7 M_{\odot}$, which is in good agreement with mass measurements from stellar dynamical modeling and gas dynamical modeling. NGC 4151 is one of the few nearby broad-lined Seyferts where the black hole mass may be measured via multiple independent techniques, and it provides an important test case for investigating potential systematics that could affect the black hole mass scales used in the local Universe and for high-redshift quasars.

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arXiv2022

The Lick AGN Monitoring Project 2016: Dynamical Modeling of Velocity-Resolved H\b{eta} Lags in Luminous Seyfert Galaxies

We have modeled the velocity-resolved reverberation response of the H\b{eta} broad emission line in nine Seyfert 1 galaxies from the Lick Active Galactic Nucleus (AGN) Monitioring Project 2016 sample, drawing inferences on the geometry and structure of the low-ionization broad-line region (BLR) and the mass of the central supermassive black hole. Overall, we find that the H\b{eta} BLR is generally a thick disk viewed at low to moderate inclination angles. We combine our sample with prior studies and investigate line-profile shape dependence, such as log10(FWHM/σ), on BLR structure and kinematics and search for any BLR luminosity-dependent trends. We find marginal evidence for an anticorrelation between the profile shape of the broad H\b{eta} emission line and the Eddington ratio, when using the root-mean-square spectrum. However, we do not find any luminosity-dependent trends, and conclude that AGNs have diverse BLR structure and kinematics, consistent with the hypothesis of transient AGN/BLR conditions rather than systematic trends.

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arXiv2022

The Paschen Jump as a Diagnostic of the Diffuse Nebular Continuum Emission in Active Galactic Nuclei

Photoionization modeling of active galactic nuclei (AGN) predicts that diffuse continuum (DC) emission from the broad-line region makes a substantial contribution to the total continuum emission from ultraviolet through near-infrared wavelengths. Evidence for this DC component is present in the strong Balmer jump feature in AGN spectra, and possibly from reverberation measurements that find longer lags than expected from disk emission alone. However, the Balmer jump region contains numerous blended emission features, making it difficult to isolate the DC emission strength. In contrast, the Paschen jump region near 8200 Å is relatively uncontaminated by other strong emission features. Here, we examine whether the Paschen jump can aid in constraining the DC contribution, using Hubble Space Telescope STIS spectra of six nearby Seyfert 1 nuclei. The spectra appear smooth across the Paschen edge, and we find no evidence of a Paschen spectral break or jump in total flux. We fit multi-component spectral models over the range $6800-9700$ Å and find that the spectra can still be compatible with a significant DC contribution if the DC Paschen jump is offset by an opposite spectral break resulting from blended high-order Paschen emission lines. The fits imply DC contributions ranging from $\sim$10% to 50% at 8000 Å, but the fitting results are highly dependent on assumptions made about other model components. These degeneracies can potentially be alleviated by carrying out fits over a broader wavelength range, provided that models can accurately represent the disk continuum shape, Fe II emission, high-order Balmer line emission, and other components.

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arXiv2021

A Detailed View of the Broad Line Region in NGC 3783 from Velocity-Resolved Reverberation Mapping

We have modeled the full velocity-resolved reverberation response of the H$β$ and He II optical broad emission lines in NGC 3783 to constrain the geometry and kinematics of the low-ionization and high-ionization broad line region. The geometry is found to be a thick disk that is nearly face on, inclined at $\sim 18^{\circ}$ to our line of sight, and exhibiting clear ionization stratification, with an extended H$β$-emitting region ($r_{\rm median}=10.07^{+1.10}_{-1.12}$ light days) and a more compact and centrally-located He II-emitting region ($r_{\rm median}=1.33^{+0.34}_{-0.42}$ light days). In the H$β$-emitting region, the kinematics are dominated by near-circular Keplerian orbits, but with $\sim 40$% of the orbits inflowing. The more compact He II-emitting region, on the other hand, appears to be dominated by outflowing orbits. The black hole mass is constrained to be $M_{\rm BH}=2.82^{+1.55}_{-0.63}\times10^7$ $M_{\odot}$, which is consistent with the simple reverberation constraint on the mass based on a mean time delay, line width, and scale factor of $\langle f \rangle=4.82$. The difference in kinematics between the H$β$- and He II-emitting regions of the BLR is intriguing given the recent history of large changes in the ionizing luminosity of NGC 3783 and evidence for possible changes in the BLR structure as a result.

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arXiv2021

The Black Hole Mass of NGC 4151 from Stellar Dynamical Modeling

The mass of a supermassive black hole ($M_\mathrm{BH}$) is a fundamental property that can be obtained through observational methods. Constraining $M_\mathrm{BH}$ through multiple methods for an individual galaxy is important for verifying the accuracy of different techniques, and for investigating the assumptions inherent in each method. NGC 4151 is one of those rare galaxies for which multiple methods can be used: stellar and gas dynamical modeling because of its proximity ($D=15.8\pm0.4$ Mpc from Cepheids), and reverberation mapping because of its active accretion. In this work, we re-analyzed $H-$band integral field spectroscopy of the nucleus of NGC 4151 from Gemini NIFS, improving the analysis at several key steps. We then constructed a wide range of axisymmetric dynamical models with the new orbit-superposition code Forstand. One of our primary goals is to quantify the systematic uncertainties in $M_\mathrm{BH}$ arising from different combinations of the deprojected density profile, inclination, intrinsic flattening, and mass-to-light ratio. As a consequence of uncertainties on the stellar luminosity profile arising from the presence of the AGN, our constraints on \mbh are rather weak. Models with a steep central cusp are consistent with no black hole; however, in models with more moderate cusps, the black hole mass lies within the range of $0.25\times10^7\,M_\odot \lesssim M_\mathrm{BH} \lesssim 3\times10^7\,M_\odot$. This measurement is somewhat smaller than the earlier analysis presented by Onken et al., but agrees with previous $M_\mathrm{BH}$ values from gas dynamical modeling and reverberation mapping. Future dynamical modeling of reverberation data, as well as IFU observations with JWST, will aid in further constraining $M_\mathrm{BH}$ in NGC 4151.

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arXiv2021

Reverberation mapping of Active Galactic Nuclei: from X-ray corona to dusty torus

The central engines of Active Galactic Nuclei (AGNs) are powered by accreting supermassive black holes, and while AGNs are known to play an important role in galaxy evolution, the key physical processes occur on scales that are too small to be resolved spatially (aside from a few exceptional cases). Reverberation mapping is a powerful technique that overcomes this limitation by using echoes of light to determine the geometry and kinematics of the central regions. Variable ionizing radiation from close to the black hole drives correlated variability in surrounding gas/dust, but with a time delay due to the light travel time between the regions, allowing reverberation mapping to effectively replace spatial resolution with time resolution. Reverberation mapping is used to measure black hole masses and to probe the innermost X-ray emitting region, the UV/optical accretion disk, the broad emission line region and the dusty torus. In this article we provide an overview of the technique and its varied applications.

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arXiv2021

AGN STORM 2: I. First results: A Change in the Weather of Mrk 817

We present the first results from the ongoing, intensive, multi-wavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this AGN was, in part, selected for its historically unobscured nature, we discovered that the X-ray spectrum is highly absorbed, and there are new blueshifted, broad and narrow UV absorption lines, which suggest that a dust-free, ionized obscurer located at the inner broad line region partially covers the central source. Despite the obscuration, we measure UV and optical continuum reverberation lags consistent with a centrally illuminated Shakura-Sunyaev thin accretion disk, and measure reverberation lags associated with the optical broad line region, as expected. However, in the first 55 days of the campaign, when the obscuration was becoming most extreme, we observe a de-coupling of the UV continuum and the UV broad emission line variability. The correlation recovers in the next 42 days of the campaign, as Mrk 817 enters a less obscured state. The short CIV and Ly alpha lags suggest that the accretion disk extends beyond the UV broad line region.

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arXiv2021

The Cepheid Distance to the Narrow-Line Seyfert 1 Galaxy NGC 4051

We derive a distance of $D = 16.6 \pm 0.3$~Mpc ($μ=31.10\pm0.04$~mag) to the archetypal narrow-line Seyfert 1 galaxy NGC 4051 based on Cepheid Period--Luminosity relations and new Hubble Space Telescope multiband imaging. We identify 419 Cepheid candidates and estimate the distance at both optical and near-infrared wavelengths using subsamples of precisely-photometered variables (123 and 47 in the optical and near-infrared subsamples, respectively). We compare our independent photometric procedures and distance-estimation methods to those used by the SH0ES team and find agreement to 0.01~mag. The distance we obtain suggests an Eddington ratio $\dot{m} \approx 0.2$ for NGC 4051, typical of narrow-line Seyfert 1 galaxies, unlike the seemingly-odd value implied by previous distance estimates. We derive a peculiar velocity of $-490\pm34$~km~s$^{-1}$ for NGC 4051, consistent with the overall motion of the Ursa Major Cluster in which it resides. We also revisit the energetics of the NGC 4051 nucleus, including its outflow and mass accretion rates.

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arXiv2021

Tully-Fisher Distances and Dynamical Mass Constraints for 24 Host Galaxies of Reverberation-Mapped AGN

We present Tully-Fisher distances for 24 AGN host galaxies with black hole mass ($M_\textrm{BH}$) measurements from reverberation mapping, as well as the first calibration of the $V-$band Tully-Fisher relation. Combining our measurements of HI 21cm emission with $HST$ and ground-based optical and near-infrared images allows multiple distance measurements for 19 galaxies and single measurements for the remaining 5. Separation of the nucleus from its host galaxy via surface brightness decomposition yields galaxy-only luminosities, thus allowing measurements of the distance moduli free of contamination from the AGN. For 14 AGN hosts, these are the first reported distances independent of redshift, and hence independent of peculiar velocities. For the remaining galaxies, we show good agreement between our distances and those previously reported from surface brightness fluctuations (SBF) and Cepheids. We also determine the total galaxy mass enclosed within the estimated HI radius, which when compared to the baryonic content allows for constraints on the dark matter masses. We find a typical mass fraction of $M_{\textrm{DM}}$/$M_{\textrm{DYN}}$ = 62\%, and find significant correlations between $M_{\textrm{BH}}$ $-$ $M_{\textrm{DYN}}$ and $M_{\textrm{BH}}$ $-$ $M_{\textrm{DM}}$. Finally, we scale our galaxy radii based on estimated relationships between visible and halo radii and assume a flat rotation curve out to the halo radius to approximate $M_{\textrm{HALO}}$. Over the range of $M_{\textrm{BH}}$ and $M_{\textrm{HALO}}$ in this sample, we find good agreement with observationally-constrained relationships between $M_{\textrm{BH}}$ and $M_{\textrm{HALO}}$ and with hydrodynamical simulations.

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arXiv2020

The Host Galaxy of the Dwarf Seyfert UGC 06728

We present multi-color high-resolution imaging of the host galaxy of the dwarf Seyfert UGC 06728. As the lowest-mass black hole to be described with both a direct mass constraint and a spin constraint, UGC 06728 is an important source for comparison with black hole evolutionary models, yet little is known about the host galaxy. Using Hubble Space Telescope imaging in the optical and near-infrared, we find that UGC 06728 is a barred lenticular (SB0) galaxy with prominent ansae at the ends of the bar. We cleanly separated the AGN from the resolved galaxy with two-dimensional image decompositions, thus allowing accurate surface brightness profiles to be derived in all filters from the outer edge of the galaxy all the way into the nucleus. Based on a sample of 51 globular cluster candidates identified in the images, the globular cluster luminosity function predicts a distance to UCG 06728 of $32.5\pm3.5$ Mpc. Combining the galaxy photometry with the distance estimate, we derive a starlight-corrected AGN luminosity, the absolute magnitude of the galaxy, and a constraint on the galaxy stellar mass of $\log M_{\star}/M_{\odot}=9.9\pm0.2$.

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arXiv2020

Robotic Reverberation Mapping of the Southern Seyfert NGC 3783

We present spectroscopic and photometric monitoring of NGC 3783 conducted throughout the first half of 2020. Time delays between the continuum variations and the response of the broad optical emission lines were clearly detected, and we report reverberation measurements for H$β$, HeII $λ4686$, H$γ$, and H$δ$. From the time delay in the broad H$β$ emission line and the line width in the variable portion of the spectrum, we derive a black hole mass of $M_{\rm BH} = 2.34^{+0.43}_{-0.43} \times 10^7$ M$_{\odot}$. This is slightly smaller than, but consistent with, previous determinations. However, our significantly improved time sampling ($T_{\rm med}=1.7$ days compared to $T_{\rm med}=4.0$ days) has reduced the uncertainties on both the time delay and the derived mass by $\sim 50$%. We also detect clear velocity-resolved time delays across the broad H$β$ profile, with shorter lags in the line wings and a longer lag in the line core. Future modeling of the full velocity-resolved time delay response will further improve the reverberation-based mass for NGC 3783, adding it to the small but growing sample of AGNs for which we have direct, primary black hole mass measurements. Upcoming MUSE observations at VLT will also allow NGC 3783 to join the smaller sample of black holes where reverberation masses and masses from stellar dynamical modeling may be directly compared.

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arXiv2020

The Sloan Digital Sky Survey Reverberation Mapping Project: Estimating Masses of Black Holes in Quasars with Single-Epoch Spectroscopy

It is well known that reverberation mapping of active galactic nuclei (AGN) reveals a relationship between AGN luminosity and the size of the broad-line region, and that use of this relationship, combined with the Doppler width of the broad emission line, enables an estimate of the mass of the black hole at the center of the active nucleus based on a single spectrum. An unresolved key issue is the choice of parameter used to characterize the line width, either FWHM or line dispersion (the square root of the second moment of the line profile). We argue here that use of FWHM introduces a bias, stretching the mass scale such that high masses are overestimated and low masses are underestimated. Here we investigate estimation of black hole masses in AGNs based on individual or "single epoch" observations, with a particular emphasis in comparing mass estimates based on line dispersion and FWHM. We confirm the recent findings that, in addition to luminosity and line width, a third parameter is required to obtain accurate masses and that parameter seems to be Eddington ratio. We present simplified empirical formulae for estimating black hole masses from the Hbeta 4861 A and C IV 1549 A emission lines. While the AGN continuum luminosity at 5100 A is usually used to predict the Hbeta reverberation lag, we show that the luminosity of the Hbeta broad component can be used instead without any loss of precision, thus eliminating the difficulty of accurately accounting for the host-galaxy contribution to the observed luminosity.

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arXiv2020

The Cepheid Distance to the Seyfert 1 Galaxy NGC 4151

We derive a distance of $15.8\pm0.4$ Mpc to the archetypical Seyfert 1 galaxy NGC 4151 based on the near-infrared Cepheid Period-Luminosity relation and new Hubble Space Telescope multiband imaging. This distance determination, based on measurements of 35 long-period ($P > 25$d) Cepheids, will support the absolute calibration of the supermassive black hole mass in this system, as well as studies of the dynamics of the feedback or feeding of its active galactic nucleus.

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arXiv2020

A Microlensing Accretion Disk Size Measurement in the Lensed Quasar WFI 2026-4536

We use thirteen seasons of R-band photometry from the 1.2m Leonard Euler Swiss Telescope at La Silla to examine microlensing variability in the quadruply-imaged lensed quasar WFI 2026-4536. The lightcurves exhibit ${\sim}\,0.2\,\text{mag}$ of uncorrelated variability across all epochs and a prominent single feature of ${\sim}\,0.1\,\text{mag}$ within a single season. We analyze this variability to constrain the size of the quasar's accretion disk. Adopting a nominal inclination of 60$^\text{o}$, we find an accretion disk scale radius of $\log(r_s/\text{cm}) = 15.74^{+0.34}_{-0.29}$ at a rest-frame wavelength of $2043\,\unicode{xC5}$, and we estimate a black hole mass of $\log(M_{\text{BH}}/M_{\odot}) = 9.18^{+0.39}_{-0.34}$, based on the CIV line in VLT spectra. This size measurement is fully consistent with the Quasar Accretion Disk Size - Black Hole Mass relation, providing another system in which the accretion disk is larger than predicted by thin disk theory.

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