arXiv subjects

Jonelle L. Walsh

Publications and source records attributed to Jonelle L. Walsh.

At least 19 recordsLinked to original sources

arXiv2026

ReveaLLAGN 3: Revealing the Infrared Spectral Energy Distributions of Low Luminosity AGN

The spectral energy distributions of active galactic nuclei (AGN) provide valuable information on the emission mechanisms taking place in their inner regions. Here we use the James Webb Space Telescope to study the near and mid-infrared spectral energy distributions of seven nearby low-luminosity active galaxy nuclei from 1.7 to 24 $μm$. We cleanly separate the AGN spectrum by performing spatial fits of the two-dimensional images across all wavelengths. We then compare these clean unresolved spectra to aperture-based spectra and show that they effectively remove galaxy contamination. Comparing our infrared measurements to X-ray emission, we find that low-luminosity AGN have enhanced near-infrared emission relative to more luminous AGN, a trend that correlates with radio-loudness, while their mid-infrared-to-X-ray ratios are comparable. A majority of our targets show strong compact silicate emission suggesting the presence of warm dust on parsec scales in these systems. We also quantify the near- and mid-infrared power-law slopes and colors of low-luminosity AGN. In the near-infrared we find AGN of all luminosities have similar spectral slopes and colors, however in the mid-infrared, we find low-luminosity AGN typically have steeper slopes and redder colors than more luminous AGN. Both the strong silicate emission and steep mid-infrared slopes disagree with existing models for low-luminosity AGN spectral energy distributions.

astro-ph.GA↗

arXiv2026

The M87 Black Hole Mass from JWST and Keck Stellar Kinematics Spanning 10 pc to 10 kpc

We combine JWST NIRSpec and Keck KCWI observations to construct a contiguous 2D map of M87's stellar kinematics spanning three decades in projected radius, from ${\sim}10$ pc to ${\sim}10$ kpc, and measure the mass of its central supermassive black hole. The innermost stellar kinematic measurements probe projected radii as small as ${\sim}3$% of the black hole's sphere of influence radius, or approximately 30,000 Schwarzschild radii. The NIRSpec spectra within $R < 0.45''$ are contaminated by quasiperiodic "wiggle" artifacts. We develop hyphen, which uses detector spectral traces to predict how the wiggle frequency varies with wavelength, then fits and subtracts the wiggle pattern from each spectrum in each exposure before combining the data. The cleaned spectra reveal a pronounced central rise in stellar velocity dispersion and $h_4$. Triaxial Schwarzschild stellar orbit modeling with the TriOS code, fitting ${\sim}$5,000 kinematic constraints across 618 spatial bins from JWST and Keck, yields a black hole mass of $M_{\mathrm{BH}}=(5.38 \pm 0.13\pm 0.22)\times10^9\,M_\odot$. This result is consistent with our prior KCWI-only determination but with the statistical uncertainty reduced by a factor of 2-3, now subdominant to the systematic uncertainty in the distance ($D$) to M87. Our inferred mass-to-distance ratio is $θ_g=GM_{\mathrm{BH}}/(c^2 D) = 3.16 \pm 0.08\, μ$as, whose 90% credible interval overlaps with that obtained from the multi-epoch Event Horizon Telescope (EHT) analysis, providing a robust and independent prior for future EHT studies.

astro-ph.GA↗

arXiv2026

ReveaLLAGN 2: Exploring the Nuclear Gas and Stellar Kinematics of Nearby LLAGNs with JWST/NIRSpec IFU

Low-luminosity active galactic nuclei (LLAGN) represent the most common mode of black hole accretion in the local Universe, yet their nuclear structure, stellar and gas kinematics remain poorly constrained at parsec scales. We investigate the nuclear regions of eight nearby representative LLAGN, the ReveaLLAGN sample: M87, M104, M94, M81, NGC1052, NGC4258, NGC5128 and NGC4395. Using JWST/NIRSpec data, we probe the stellar, molecular hydrogen, hydrogen recombination, and high ionisation coronal lines kinematics and their spatial distribution, exploring how detectability and spatial distributions of these lines vary across different Eddington ratios. The stellar LOSV maps reveal a slowly rotating disk in the nuclei of all our targets, characterised by an anti-correlation with the h3 Gauss-Hermite moment. Across the sample, the stellar velocity dispersion rises toward the central black hole. Only in M104 and M94 does the velocity dispersion display a more intricate pattern that departs from a simple disk configuration, indicating the presence of multiple kinematic components in these galaxies. Across the sample, the gas distribution and kinematics exhibit rotation that is frequently decoupled from the stellar rotation, suggesting that the stellar gravitational potential is decoupled from the current accretion state. The gas kinematics are often visually aligned with the radio jet, presenting broader velocity dispersions along the jet direction. Line-ratio maps indicate that the dominant excitation mechanism is photoionisation by the central AGN, with mechanical heating from shocks becoming important only at higher Eddington ratios. Across the sample, we detect coronal lines in all LLAGN when using nuclear-aperture spectra, and we can obtain spatially resolved kinematics only in NGC5128 and NGC4395, the highest Eddington ratio sources.

astro-ph.GA↗

arXiv2026

A stellar dynamical mass measurement of an inactive black hole at redshift 2

Supermassive black holes and their host galaxies grow together over time, producing correlations between the black hole mass and various galaxy properties. Determining the evolution of these correlations requires precise measurements of the masses of distant black holes. We observe the gravitationally lensed quiescent galaxy MRG-M0138, at redshift 1.95, using JWST integral field spectroscopy to spatially resolve the kinematics of stars within the black hole's sphere of influence. By using a foreground lens model and fitting stellar dynamical models, we determine the mass of its inactive black hole, $M_{\bullet}=6.0^{+2.1}_{-1.7}\times10^9$ solar masses. Comparing this measurement to local galaxies, we find that $M_{\bullet}$ is higher than expected given the galaxy's bulge mass, but consistent with the correlation with stellar velocity dispersion.

astro-ph.GA↗

arXiv2026

JWST and Keck observations of the off-nuclear tidal disruption event TDE 2025abcr: An evolving reprocessing layer

Off-nuclear tidal disruption events (TDEs) provide a rare probe of massive black holes (MBHs) outside galactic nuclei. Only a handful are known, including five X-ray-selected candidates and two optically selected events. We present observations of TDE 2025abcr, the second optically selected off-nuclear TDE, discovered at a projected offset of $9.08 \pm 0.02$ kpc from the nucleus of its host galaxy. We analyze X-ray, UV, optical, and infrared (IR) data from Swift, Keck, ZTF, and JWST. Broad H and He emission lines in the optical and IR confirm a TDE-H-He classification. From luminosity scaling relations and MOSFiT modeling, we infer a BH mass of $10^{6}$-$10^{7}\,M_{\odot}$, substantially smaller than the $10^{8.35 \pm 0.41}\,M_{\odot}$ BH inferred for the host-galaxy nucleus. We observe velocity evolution in the N III + He II emission complex, shifting from $-500$ km s$^{-1}$ at day $-7$ to $+1000$ km s$^{-1}$ by day $+29$, which we interpret as radiative transfer effects in an evolving reprocessing layer. The IR SED deviates from a thermal blackbody, with $νL_ν \propto λ^{-2.13 \pm 0.04}$, significantly shallower than the Rayleigh-Jeans slope of $λ^{-3}$. We rule out dust as the source of this IR excess. Two possibilities remain: free-free emission from reprocessing gas, or an unresolved stellar cluster at the TDE location. Reprocessed emission provides a natural explanation for the IR excess but an underlying stellar cluster of mass $\log(M_{*}/M_{\odot}) = 7.57 \pm 0.02$ and age $<$2 Gyr is also consistent with the data. If interpreted as a stellar cluster, the inferred mass suggests a stripped remnant of a satellite galaxy. The wandering MBH most likely originated in a minor merger with a smaller galaxy, although dynamical ejection from the host nucleus cannot yet be ruled out.

astro-ph.HE↗

arXiv2026

ReveaLLAGN 1: JWST Emission-Line Spectra Reveal Low-Luminosity AGN with UV-Deficient SEDs and Warm Molecular Gas

We present near- and mid-infrared spectra of eight Low-Luminosity Active Galactic Nuclei (LLAGN), spanning nearly four orders of magnitude in black hole mass and Eddington ratio, obtained with JWST/NIRSpec and MIRI as part of the ReveaLLAGN program along with identical archival data of Cen A. The high spatial resolution of JWST cleanly separates AGN emission from host-galaxy contamination, enabling detections of high-ionization potential lines more than an order of magnitude fainter than previously measured. Emission-line diagnostics reveal a transition at log($L_{bol}/L_{Edd}$) ~ -3.5, where the spectral energy distribution becomes increasingly deficient in ultraviolet photons. We find that rotational H$_2$ excitation temperatures are elevated (~500 K higher) compared to both higher-luminosity AGN and star-forming galaxies, while the H$_2$(0-0)S(3)/PAH$_{11.3 μm}$ ratios are consistent with those observed in the AGN population. We discuss the possible roles of outflows, jets, and X-ray dominated regions in shaping the interstellar medium surrounding LLAGN. Silicate emission at ~10 $μ$m, localized to the nuclear region, is detected in most ReveaLLAGN targets. This dataset offers the first comprehensive JWST-based characterization of infrared emission lines in the nuclear regions of LLAGN.

astro-ph.GA↗

arXiv2025

Mapping the Stellar Kinematics in the Central 240 Parsecs of M87 with the James Webb Space Telescope

The supermassive black hole (SMBH) in the giant elliptical galaxy M87 is one of the most well-studied in the local universe, but the stellar- and gas-dynamical SMBH mass measurements disagree. As this galaxy is a key anchor for the upper end of the SMBH mass$-$host galaxy relations, we revisit the central $3''\times 3''$ ($\sim 240\times240$ pc) region of M87 with the Near Infrared Spectrograph (NIRSpec) integral field unit (IFU) on the James Webb Space Telescope (JWST). We implement several improvements to the reduction pipeline and obtain high signal-to-noise spectra ($S/N \sim 150$) in single $0.''05 $ spaxels across much of the NIRSpec field of view. We measure the detailed shape of the stellar line-of-sight velocity distribution, parameterized by Gauss-Hermite moments up to $h_8$, in $\sim 2800$ spatial bins, substantially improving upon the prior high angular resolution studies of the M87 stellar kinematics. The NIRSpec data reveal velocities with $V \sim \pm 45$ km s$^{-1}$, velocity dispersions that rise sharply to $\sim$$420$ km s$^{-1}$ at a projected radius of 0.$''$45 (36 pc), and a slight elevation in $h_4$ toward the nucleus. We comprehensively test the robustness of the kinematics, including using multiple velocity template libraries and adopting different polynomials to adjust the template spectra. We find that the NIRSpec stellar kinematics seamlessly transition to recently measured large-scale stellar kinematics from optical Keck Cosmic Web Imager (KCWI) IFU data. These combined NIRSpec and KCWI kinematics provide continuous coverage from parsec to kiloparsec scales and will critically constrain future stellar-dynamical models of M87.

astro-ph.GA↗

arXiv2025

The MASSIVE Survey. XX. A Triaxial Stellar Dynamical Measurement of the Supermassive Black Hole Mass and Intrinsic Galaxy Shape of Giant Radio Galaxy NGC 315

We present a new dynamical measurement of the supermassive black hole mass and intrinsic shape of the stellar halo of the massive radio galaxy NGC 315 as part of the MASSIVE survey. High signal-to-noise ratio spectra from integral-field spectrographs at the Gemini and McDonald Observatories provide stellar kinematic measurements in $304$ spatial bins from the central ${\sim}0.3''$ out to $30''$. Using ${\sim} 2300$ kinematic constraints, we perform triaxial stellar orbit modeling with the TriOS code and search over ${\sim}$15,000 galaxy models with a Bayesian scheme to simultaneously measure six mass and intrinsic shape parameters. NGC 315 is triaxial and highly prolate, with middle-to-long and short-to-long axis ratios of $p=0.854$ and $q=0.833$ and a triaxiality parameter of $T=0.89$. The black hole mass inferred from our stellar kinematics is $M_\mathrm{BH} = \left(3.0 {\pm} 0.3\right) {\times} 10^{9}\ M_\odot$, which is higher than $M_\mathrm{BH}=(1.96^{+0.30}_{-0.13}) {\times} 10^{9} M_\odot$ inferred from CO kinematics (scaled to our distance). When the seven galaxies with $M_\mathrm{BH}$ measurements from both stellar and CO kinematics are compared, we find an intrinsic scatter of 0.28 dex in $M_\mathrm{BH}$ from the two tracers and do not detect statistically significant biases between the two methods in the current data. The implied black hole shadow size (${\approx} 4.7\, μ{\rm as}$) and the relatively high millimeter flux of NGC 315 makes this galaxy a prime candidate for future horizon-size imaging studies.

astro-ph.GA↗

arXiv2025

CO Emission and Absorption-line Survey of the M87 Nucleus Using Archival ALMA Imaging

We present an M87 molecular line search from archival Atacama Large Millimeter/sub-millimeter Array (ALMA) imaging, covering the circumnuclear disk (CND) as well as ionized gas filaments and dusty cloud regions. We find no evidence for CO emission in the central $\sim$kpc and place an upper limit of $M_\mathrm{H_2} < 2.3\times 10^5$ $M_\odot$ in the atomic gas CND region, a factor of 20$\times$ lower than previous surveys. During this search, we discovered extragalactic CO absorption lines in the $J$ = 1$-$0, 2$-$1, and 3$-$2 transitions against the bright (Jy-scale) active nucleus. These CO lines are narrow ($\sim$5 km s$^{-1}$) and blueshifted with respect to the galaxy's systemic velocity by $-$75 to $-$84 \kms. This CO absorber appears to be kinematically distinct from outflowing atomic gas seen in absorption. Low integrated opacities ranging from $τ_\mathrm{CO} \sim 0.02-0.06$ \kms\ and a column density $N_\mathrm{CO} \approx (1.2\pm0.2)\times 10^{15}$ cm$^{-2}$ translate to $N_\mathrm{H_2} \sim (1-2) \times 10^{20}$ cm$^{-2}$. CO excitation temperatures spanning $T_\mathrm{ex} \sim 8$ K to $\sim$30 K do not follow local thermodynamic equilibrium (LTE) expectations, and non-LTE radex radiative transfer modeling of the CO absorber is consistent with a number density $n_\mathrm{H_2} \sim 5000$ cm$^{-3}$ embedded in a $\sim$60 K environment. Taken together, the observed CO absorption lines are most consistent with a thin, pressure-confined filament seen slightly off-center from the M87 nucleus. We also explore the impact of residual telluric lines and atmospheric variability on narrow extragalactic line identification and demonstrate how bandpass calibration limitations may introduce broad but very low S/N and spurious absorption and emission signatures.

astro-ph.GA↗

arXiv2025

WIggle Corrector Kit for NIRSpEc Data: WICKED

The point-spread function of the integral-field unit (IFU) mode of the JWST's NIRSpec is heavily under-sampled, creating resampling noise seen as low-frequency sinusoidal-like artifacts, or "wiggles". These artifacts in the data are not corrected in the JWST data pipeline, and significantly impact the science that can be achieved at a single-pixel level. We present WICKED (WIggle Corrector Kit for NIRSpEc Data), a tool designed to empirically remove wiggles. WICKED uses the Fast Fourier Transform to identify wiggle-affected spaxels across the data cube. Spectra are modeled with a mix of integrated aperture and annular templates, a power-law, and a second-degree polynomial. The method works across all medium- and high-resolution NIRSpec gratings: F070LP, F100LP, F170LP, and F290LP. WICKED can recover the true overall spectral shape up to a factor of 3.5x better compared to uncorrected spectra. It recovers the equivalent width of absorption lines within 5% of the true value-~3x better than uncorrected spectra and ~2x better than other methods. WICKED significantly improves kinematic measurements, recovering the line-of-sight velocity (LOSV) within 1% of the true value -- more than 100x better than uncorrected spectra at S/N ~40. As a case study, we applied WICKED to G235H/F170LP IFU data of the elliptical galaxy NGC5128, finding good agreement with previous studies. In wiggle-affected regions, the uncorrected spectrum showed stellar LOSV and velocity dispersion differences compared to the WICKED-cleaned spectrum, of ~17x and ~36x larger than the estimated uncertainties, respectively. Wiggles in NIRSpec IFU data can introduce severe biases in spectral shape, line measurements, and kinematics to values larger than the typical uncertainties. WICKED provides a robust, user-friendly solution, enabling precise single-pixel studies and maximizing JWST's potential.

astro-ph.IM↗

arXiv2025

HST Observations within the Sphere of Influence of the Powerful Supermassive Black Hole in PKS0745-191

We present Space Telescope Imaging Spectrograph observations from the Hubble Space Telescope of the supermassive black hole (SMBH) at the center of PKS0745-191, a brightest cluster galaxy (BCG) undergoing powerful radio-mode AGN feedback ($P_{\rm cav}\sim5\times10^{45}$ erg s$^{-1}$). These high-resolution data offer the first spatially resolved map of gas dynamics within a SMBHs sphere of influence under such powerful feedback. Our results reveal the presence of highly chaotic, non-rotational ionized gas flows on sub-kpc scales, in contrast to the more coherent flows observed on larger scales. While radio-mode feedback effectively thermalizes hot gas in galaxy clusters on kiloparsec scales, within the core, the hot gas flow may decouple, leading to a reduction in angular momentum and supplying ionized gas through cooling, which could enhance accretion onto the SMBH. This process could, in turn, lead to a self-regulating feedback loop. Compared to other BCGs with weaker radio-mode feedback, where rotation is more stable, intense feedback may lead to more chaotic flows, indicating a stronger coupling between jet activity and gas dynamics. Additionally, we observe a sharp increase in velocity dispersion near the nucleus, consistent with a very massive $M_{\rm BH}\sim1.5\times10^{10} M_\odot$ SMBH. The density profile of the ionized gas is also notably flat, paralleling the profiles observed in X-ray gas around galaxies where the Bondi radius is resolved. These results provide valuable insights into the complex mechanisms driving galaxy evolution, highlighting the intricate relationship between SMBH fueling and AGN feedback within the host galaxy.

astro-ph.GA↗

arXiv2025

A 22-Billion Solar Mass Black Hole in Holmberg 15A with Keck KCWI Spectroscopy and Triaxial Orbit Modeling

Holmberg 15A (H15A), the brightest cluster galaxy of Abell 85, has an exceptionally low central surface brightness even among local massive elliptical galaxies with distinct stellar cores, making it exceedingly challenging to obtain high-quality spectroscopy to detect a supermassive black hole (SMBH) at its center. Aided by the superb sensitivity and efficiency of KCWI at the Keck II Telescope, we have obtained spatially resolved stellar kinematics over a ${\sim}100''\times 100''$ contiguous field of H15A for this purpose. The velocity field exhibits a low amplitude (${\sim}20\mathrm{~km~s}^{-1}$) rotation along a kinematic axis that is prominently misaligned from the photometric major axis, a strong indicator that H15A is triaxially shaped with unequal lengths for the three principal axes. Using 2500 observed kinematic constraints, we perform extensive calculations of stellar orbits with the triaxial Schwarzschild code, TriOS, and search over ${\sim}$40,000 galaxy models to simultaneously determine the mass and intrinsic 3D shape parameters of H15A. We determine a ratio of $p=0.89$ for the middle-to-long principal axes and $q=0.65$ for the short-to-long principal axes. Our best estimate of the SMBH mass, $M_\mathrm{BH}=(2.16^{+0.23}_{-0.18})\times 10^{10}M_{\odot}$, makes H15A -- along with NGC 4889 -- the galaxies hosting the most massive SMBHs known in the local universe. Both SMBHs lie significantly above the mean $M_\mathrm{BH}-σ$ scaling relation. Repeating the orbit modeling with the axisymmetrized version of TriOS produces worse fits to the KCWI kinematics and increases $M_\mathrm{BH}$ to $(2.55\pm 0.20) \times 10^{10}M_{\odot}$, which is still significantly below $M_\mathrm{BH}=(4.0\pm 0.8) \times 10^{10}M_{\odot}$ reported in a prior axisymmetric study of H15A.

astro-ph.GA↗

arXiv2024

Rare Occasions: Tidal Disruption Events Rarely Power the AGNs Observed in Dwarf Galaxies

Tidal disruption events (TDEs) could be an important growth channel for massive black holes in dwarf galaxies. Theoretical work suggests that the observed active galactic nuclei (AGNs) in dwarf galaxies are predominantly TDE-powered. To assess this claim, we perform variability analyses on the dwarf-hosted AGNs detected in the $7$ Ms Chandra Deep Field-South (CDF-S) survey, with observations spanning $\approx 16$ years. Based on the spectral energy distribution (SED) modeling with X-CIGALE, we select AGNs hosted by dwarf galaxies (stellar mass below $10^{10}\ M_\odot$). We focus on X-ray sources with full-band detections, leading to a sample of $78$ AGNs (0.122 $\leq$ $z$ $\leq$ 3.515). We fit the X-ray light curves with a canonical TDE model of $t^{-5/3}$ and a constant model. If the former outperforms the latter in fitting quality for a source, we consider the source as a potential TDE. We identify five potential TDEs, constituting a small fraction of our sample. Using true- and false-positive rates obtained from fitting models to simulated light curves, we perform Bayesian analysis to obtain the posterior of the TDE fraction for our sample. The posterior peaks close to zero ($2.56\%$), and we obtain a $2$-$σ$ upper limit of $9.80\%$. Therefore, our result indicates that the observed AGNs in dwarf galaxies are not predominantly powered by TDEs.

astro-ph.GA↗

arXiv2024

Modeling ALMA Observations of the Warped Molecular Gas Disk in the Red Nugget Relic Galaxy NGC 384

We present 0$.\!\!^{\prime\prime}{22}$-resolution CO(2$-$1) observations of the circumnuclear gas disk in the local compact galaxy NGC 384 with the Atacama Large Millimeter/submillimeter Array (ALMA). While the majority of the disk displays regular rotation with projected velocities rising to $370$ km s$^{-1}$, the inner $\sim$0\farcs{5} exhibits a kinematic twist. We develop warped disk gas-dynamical models to account for this twist, fit those models to the ALMA data cube, and find a stellar mass-to-light ratio in the $H$-band of \mlabstract\ and a supermassive black hole (BH) mass ($M_{\mathrm{BH}}$) of $M_{\mathrm{BH}}$ $= (7.26^{+0.43}_{-0.48}$ [$1σ$ statistical] $^{+0.55}_{-1.00}$ [systematic])$\times 10^8$ $M_\odot$. In contrast to most previous dynamical $M_{\mathrm{BH}}$ measurements in local compact galaxies, which typically found over-massive BHs compared to the local BH mass$-$bulge luminosity and BH mass$-$bulge mass relations, NGC 384 lies within the scatter of those scaling relations. NGC 384 and other local compact galaxies are likely relics of $z\sim2$ red nuggets, and over-massive BHs in these relics indicate BH growth may conclude before the host galaxy stars have finished assembly. Our NGC 384 results may challenge this evolutionary picture, suggesting there may be increased scatter in the scaling relations than previously thought. However, this scatter could be inflated by systematic differences between stellar- and gas-dynamical measurement methods, motivating direct comparisons between the methods for NGC 384 and the other compact galaxies in the sample.

astro-ph.GA↗

arXiv2024

Circumnuclear Dust in Luminous Early-Type Galaxies -- I. Sample Properties and Stellar Luminosity Models

Dusty circumnuclear disks (CNDs) in luminous early-type galaxies (ETGs) show regular, dynamically cold molecular gas kinematics. For a growing number of ETGs, Atacama Large Millimeter/sub-millimeter Array (ALMA) CO imaging and detailed gas-dynamical modeling facilitate moderate-to-high precision black hole (BH) mass ($M_{BH}$) determinations. From the ALMA archive, we identified a subset of 26 ETGs with estimated $M_{BH}/M_{\odot} \gtrsim 10^8$ to a few $\times$10$^9$ and clean CO kinematics but that previously did not have sufficiently high angular resolution near-IR observations to mitigate dust obscuration when constructing stellar luminosity models. We present new optical and near-IR Hubble Space Telescope (HST) images of this sample to supplement the archival HST data, detailing the sample properties and data analysis techniques. After masking the most apparent dust features, we measure stellar surface brightness profiles and model the luminosities using the multi-Gaussian expansion (MGE) formalism. Some of these MGEs have already been used in CO dynamical modeling efforts to secure quality \mbh\ determinations, and the remaining ETG targets here are expected to significantly improve the high-mass end of the current BH census, facilitating new scrutiny of local BH mass-host galaxy scaling relationships. We also explore stellar isophotal behavior and general dust properties, finding these CNDs generally become optically thick in the near-IR ($A_H \gtrsim 1$ mag). These CNDs are typically well-aligned with the larger-scale stellar photometric axes with a few notable exceptions. Uncertain dust impact on the MGE often dominates the BH mass error budget, so extensions of this work will focus on constraining CND dust attenuation.

astro-ph.GA↗

arXiv2024

Gas-dynamical Mass Measurements of the Supermassive Black Holes in the Early-Type Galaxies NGC 4786 and NGC 5193 from ALMA and HST Observations

We present molecular gas-dynamical mass measurements of the central black holes in the giant elliptical galaxies NGC 4786 and NGC 5193, based on CO(2$-$1) observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and Hubble Space Telescope near-infrared imaging. The central region in each galaxy contains a circumnuclear disk that exhibits orderly rotation with projected line-of-sight velocities of ${\sim} 270\, \mathrm{km}\,\mathrm{s^{-1}}$. We build gas-dynamical models for the rotating disk in each galaxy and fit them directly to the ALMA data cubes. At $0.31^{\prime \prime}$resolution, the ALMA observations do not fully resolve the black hole sphere of influence (SOI), and neither galaxy exhibits a central rise in rotation speed, indicating that emission from deep within the SOI is not detected. As a result, our models do not tightly constrain the central black hole mass in either galaxy, but they prefer the presence of a central massive object in both galaxies. We measure the black hole mass to be $(M_{\mathrm{BH}}/10^8\, M_{\odot}) = 5.0 \pm 0.2 \,[\mathrm{1σ\,statistical}] \,^{+1.4}_{-1.3} \,[\mathrm{systematic}]$ in NGC 4786 and $(M_{\mathrm{BH}}/10^8\, M_{\odot}) = 1.4 \pm 0.03 \, [\mathrm{1σ\,statistical}] ^{+1.5}_{-0.1} \,[\mathrm{systematic}]$ in NGC 5193. The largest component of each measurement's error budget is from the systematic uncertainty associated with the extinction correction in the host galaxy models. This underscores the importance of assessing the impact of dust attenuation on the inferred $M_{\mathrm{BH}}$.

astro-ph.GA↗

arXiv2023

ALMA gas-dynamical mass measurement of the supermassive black hole in the red nugget relic galaxy PGC 11179

We present 0$.\!\!^{\prime\prime}22$-resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of CO(2$-$1) emission from the circumnuclear gas disk in the red nugget relic galaxy PGC 11179. The disk shows regular rotation, with projected velocities near the center of 400 km s$^{-1}$. We assume the CO emission originates from a dynamically cold, thin disk and fit gas-dynamical models directly to the ALMA data. In addition, we explore systematic uncertainties by testing the impacts of various model assumptions on our results. The supermassive black hole (BH) mass ($M_\mathrm{BH}$) is measured to be $M_\mathrm{BH} = (1.91\pm0.04$ [$1σ$ statistical] $^{+0.11}_{-0.51}$ [systematic])$\times 10^9$ $M_\odot$, and the $H$-band stellar mass-to-light ratio $M/L_H=1.620\pm0.004$ [$1σ$ statistical] $^{+0.211}_{-0.107}$ [systematic] $M_\odot/L_\odot$. This $M_\mathrm{BH}$ is consistent with the BH mass$-$stellar velocity dispersion relation but over-massive compared to the BH mass$-$bulge luminosity relation by a factor of 3.7. PGC 11179 is part of a sample of local compact early-type galaxies that are plausible relics of $z\sim2$ red nuggets, and its behavior relative to the scaling relations echoes that of three relic galaxy BHs previously measured with stellar dynamics. These over-massive BHs could suggest BHs gain most of their mass before their host galaxies do. However, our results could also be explained by greater intrinsic scatter at the high-mass end of the scaling relations, or by systematic differences in gas- and stellar-dynamical methods. Additional $M_\mathrm{BH}$ measurements in the sample, including independent cross-checks between molecular gas- and stellar-dynamical methods, will advance our understanding of the co-evolution of BHs and their host galaxies.

astro-ph.GA↗

arXiv2023

What Does the Virial Coefficient of the \Hb Broad-Line Region Depend On?

We combine our dynamical modeling black hole mass measurements from the Lick AGN Monitoring Project 2016 sample with measured cross-correlation time lags and line widths to recover individual scale factors, f, used in traditional reverberation mapping analyses. We extend our sample by including prior results from Code for AGN Reverberation and Modeling of Emission Lines (caramel) studies that have utilized our methods. Aiming to improve the precision of black hole mass estimates, as well as uncover any regularities in the behavior of the broad-line region (BLR), we search for correlations between f and other AGN/BLR parameters. We find (i) evidence for a correlation between the virial coefficient log10(fmean,σ) and black hole mass, (ii) marginal evidence for a similar correlation between log10(frms,σ) and black hole mass, (iii) marginal evidence for an anti-correlation of BLR disk thickness with log10(fmean,FWHM)and log10(frms,FWHM), and (iv) marginal evidence for an anti-correlation of inclination angle with log10(fmean,FWHM), log10(frms,σ), and log10(fmean,σ). Lastly, we find marginal evidence for a correlation between line-profile shape, when using the root-meansquare spectrum, log10(FWHM/σ)rms, and the virial coefficient, log10(frms,σ), and investigate how BLR properties might be related to line-profile shape using caramel models.

astro-ph.GA↗