Modeling the SED of the AGN inside NGC 4395

We study the broad-band spectral energy distribution (SED) of the prototypical low-mass active galactic nucleus (AGN) in NGC 4395. We jointly model the optical through mid-infrared SED with a combination of galaxy and AGN light, and find that on arcsecond scales, the AGN dominates at most wavelengths. However, there is still some ambiguity about emission from the galaxy, owing partially to the strong short-term variability of the black hole. We investigate the use of smooth and clumpy-torus models in order to disentangle the nuclear infrared emission, as well as exploring the use of poloidal wind emission to account for the blue spectral slope observed in the near-IR. Even when simultaneously fitting the full optical-IR spectral range, we find that degeneracies still remain in the best-fit models. We conclude that high spatial resolution and wider wavelength coverage with the James Webb Space Telescope is needed to understand the mid-infrared emission in this complex highly-variable object, which is the best nearby example to provide a blueprint to finding other low-mass AGN via their mid-infrared emission in the future.Comment: 17 pages, 8 figure

Spectropolarimetric measurements of hidden broad lines in nearby megamaser galaxies: a lack of clear evidence for a correlation between black hole masses and virial products

High-accuracy black hole (BH) masses require excellent spatial resolution that is only achievable for galaxies within ~100 Mpc using present-day technology. At larger distances, BH masses are often estimated with single-epoch scaling relations for active galactic nuclei. This method requires only luminosity and the velocity dispersion of the broad line region (BLR) to calculate a virial product, and an additional virial factor, $f$, to determine BH mass. The accuracy of these single-epoch masses, however, is unknown, and there are few empirical constraints on the variance of $f$ between objects. We attempt to calibrate single-epoch BH masses using spectropolarimetric measurements of nine megamaser galaxies from which we measure the velocity distribution of the BLR. We do not find strong evidence for a correlation between the virial products used for single-epoch masses and dynamical mass, both for the megamaser sample alone and when combined with dynamical masses from reverberation mapping modeling. Furthermore, we find evidence that the virial parameter $f$ varies between objects, but we do not find strong evidence for a correlation with other observable parameters such as luminosity or broad line width. Although we cannot definitively rule out the existence of any correlation between dynamical mass and virial product, we find tension between allowed $f$ values for masers and those widely used in the literature. We conclude that the single-epoch method requires further investigation if it is to be used successfully to infer BH masses.Comment: 27 pages, 16 figures, resubmitted to ApJ after incorporating reviewer's comments. Corrected Figure 8, main results do not chang

First Detection of an Over-Massive Black Hole Galaxy UHZ1: Evidence for Heavy Black Hole Seed Formation from Direct Collapse

The recent Chandra-JWST discovery of a quasar in the z = 10.1 galaxy UHZ1 reveals that accreting supermassive black holes (SMBHs) were already in place 470 million years after the Big Bang. The Chandra X-ray source detected in UHZ1 is a Compton-thick quasar with a bolometric luminosity of $L_{\rm bol}\sim5\times10^{45}\ \rm{erg\ s^{-1}},$ which corresponds to an estimated BH mass of $\sim4\times10^7 \ \rm{M_{\odot}}$ assuming accretion at the Eddington rate. JWST NIRCAM and NIRSpec data yield a stellar mass estimate for UHZ1 comparable to its BH mass. These characteristics are in excellent agreement with prior theoretical predictions for a unique class of transient, high-redshift objects, Over-massive Black Hole Galaxies [OBGs] by Natarajan et al. that harbor a heavy initial black hole seed that likely formed from the direct collapse of the gas. Based on the excellent agreement between the observed multi-wavelength properties of UHZ1 with theoretical model template predictions, suggests that UHZ1 is the first detected OBG candidate. Our assertion rests on multiple lines of concordant evidence between model predictions and the following observed properties of UHZ1: its X-ray detection and the estimated ratio of the X-ray flux to the IR flux that is consistent with theoretical expectations for a heavy initial BH seed; its high measured redshift of z = 10.1, as predicted for the transient OBG stage (9 < z< 12); the amplitude and shape of the detected JWST Spectral Energy Distribution (SED) between 1 - 5 microns, which is in very good agreement with simulated template SEDs for OBGs; and the extended JWST morphology of UHZ1 that is suggestive of a recent merger, also expected for the formation of transient OBGs. As the first OBG candidate, UHZ1 provides compelling evidence for the formation of heavy initial seeds from direct collapse in the early Universe.Comment: 9 pages, 4 figures, accepted ApJ Letter

Variable Hard X-ray Emission from the Candidate Accreting Black Hole in Dwarf Galaxy Henize 2-10

We present an analysis of the X-ray spectrum and long-term variability of the nearby dwarf starburst galaxy Henize 2-10. Recent observations suggest that this galaxy hosts an actively accreting black hole with mass ~10^6 M_sun. The presence of an AGN in a low-mass starburst galaxy marks a new environment for active galactic nuclei (AGNs), with implications for the processes by which "seed" black holes may form in the early Universe. In this paper, we analyze four epochs of X-ray observations of Henize 2-10, to characterize the long-term behavior of its hard nuclear emission. We analyze observations with Chandra from 2001 and XMM-Newton from 2004 and 2011, as well as an earlier, less sensitive observation with ASCA from 1997. Based on detailed analysis of the source and background, we find that the hard (2-10 keV) flux of the putative AGN has decreased by approximately an order of magnitude between the 2001 Chandra observation and exposures with XMM-Newton in 2004 and 2011. The observed variability confirms that the emission is due to a single source. It is unlikely that the variable flux is due to a supernova or ultraluminous X-ray source, based on the observed long-term behavior of the X-ray and radio emission, while the observed X-ray variability is consistent with the behavior of well-studied AGNs.Comment: 7 pages, 4 figures, 2 tables; accepted for publication in Ap

ELVES IV: The Satellite Stellar-to-Halo Mass Relation Beyond the Milky-Way

Quantifying the connection between galaxies and their host dark matter halos has been key for testing cosmological models on various scales. Below $M_\star \sim 10^9\,M_\odot$, such studies have primarily relied on the satellite galaxy population orbiting the Milky Way. Here we present new constraints on the connection between satellite galaxies and their host dark matter subhalos using the largest sample of satellite galaxies in the Local Volume ($D \lesssim 12\,\mathrm{Mpc}$) to date. We use $250$ confirmed and $71$ candidate dwarf satellites around 27 Milky Way (MW)-like hosts from the Exploration of Local VolumE Satellites (ELVES) Survey and use the semi-analytical SatGen model for predicting the population of dark matter subhalos expected in the same volume. Through a Bayesian model comparison of the observed and the forward-modeled satellite stellar mass functions (SSMF), we infer the satellite stellar-to-halo mass relation. We find that the observed SSMF is best reproduced when subhalos at the low mass end are populated by a relation of the form $M_\star \propto M^\alpha_\mathrm{peak}$, with a moderate slope of $\alpha_\mathrm{const}=2.10 \pm 0.01$ and a low scatter, constant as a function of the peak halo mass, of $\sigma_\mathrm{const}=0.06^{+0.07}_{-0.05}$. A model with a steeper slope ($\alpha_\mathrm{grow}=2.39 \pm 0.06$) and a scatter that grows with decreasing $M_\mathrm{peak}$ is also consistent with the observed SSMF but is not required. Our new model for the satellite-subhalo connection, based on hundreds of Local Volume satellite galaxies, is in line with what was previously derived using only the Milky Way satellites.Comment: Accepted for publication in ApJ. Figure 8 shows the key result -- the Satellite Stellar to Halo Mass relation obtained in this work, in comparison to previous studie

The MASSIVE Survey - X. Misalignment between Kinematic and Photometric Axes and Intrinsic Shapes of Massive Early-Type Galaxies

We use spatially resolved two-dimensional stellar velocity maps over a $107"\times 107"$ field of view to investigate the kinematic features of 90 early-type galaxies above stellar mass $10^{11.5}M_\odot$ in the MASSIVE survey. We measure the misalignment angle $\Psi$ between the kinematic and photometric axes and identify local features such as velocity twists and kinematically distinct components. We find 46% of the sample to be well aligned ($\Psi < 15^{\circ}$), 33% misaligned, and 21% without detectable rotation (non-rotators). Only 24% of the sample are fast rotators, the majority of which (91%) are aligned, whereas 57% of the slow rotators are misaligned with a nearly flat distribution of $\Psi$ from $15^{\circ}$ to $90^{\circ}$. 11 galaxies have $\Psi \gtrsim 60^{\circ}$ and thus exhibit minor-axis ("prolate") rotation in which the rotation is preferentially around the photometric major axis. Kinematic misalignments occur more frequently for lower galaxy spin or denser galaxy environments. Using the observed misalignment and ellipticity distributions, we infer the intrinsic shape distribution of our sample and find that MASSIVE slow rotators are consistent with being mildly triaxial, with mean axis ratios of $b/a=0.88$ and $c/a=0.65$. In terms of local kinematic features, 51% of the sample exhibit kinematic twists of larger than $20^{\circ}$, and 2 galaxies have kinematically distinct components. The frequency of misalignment and the broad distribution of $\Psi$ reported here suggest that the most massive early-type galaxies are mildly triaxial, and that formation processes resulting in kinematically misaligned slow rotators such as gas-poor mergers occur frequently in this mass range.Comment: Accepted to MNRA

Megamaser Disks Reveal a Broad Distribution of Black Hole Mass in Spiral Galaxies

We use new precision measurements of black hole masses from water megamaser disks to investigate scaling relations between macroscopic galaxy properties and supermassive black hole (BH) mass. The megamaser-derived BH masses span 10^6-10^8 M_sun, while all the galaxy properties that we examine (including stellar mass, central mass density, central velocity dispersion) lie within a narrow range. Thus, no galaxy property correlates tightly with M_BH in ~L* spiral galaxies. Of them all, stellar velocity dispersion provides the tightest relation, but at fixed sigma* the mean megamaser M_BH are offset by -0.6+/-0.1 dex relative to early-type galaxies. Spiral galaxies with non-maser dynamical BH masses do not show this offset. At low mass, we do not yet know the full distribution of BH mass at fixed galaxy property; the non-maser dynamical measurements may miss the low-mass end of the BH distribution due to inability to resolve the spheres of influence and/or megamasers may preferentially occur in lower-mass BHs.Comment: 6 pages, 4 figures, replaced to fix error: NGC 4594 is not a maser galax