arXiv subjects

Benjamin D. Boizelle

Publications and source records attributed to Benjamin D. Boizelle.

23 records · Page 2Linked to original sources

arXiv2020

Black Hole Mass Measurements of Radio Galaxies NGC 315 and NGC 4261 Using ALMA CO Observations

We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 5 and Cycle 6 observations of CO(2$-$1) and CO(3$-$2) emission at 0.2''$-$0.3'' resolution in two radio-bright, brightest group/cluster early-type galaxies, NGC 315 and NGC 4261. The data resolve CO emission that extends within their black hole (BH) spheres of influence ($r_\mathrm{g}$), tracing regular Keplerian rotation down to just tens of parsecs from the BHs. The projected molecular gas speeds in the highly inclined ($i>60^\circ$) disks rises at least 500 km s$^{-1}$ near their galaxy centers. We fit dynamical models of thin-disk rotation directly to the ALMA data cubes, and account for the extended stellar mass distributions by constructing galaxy surface brightness profiles corrected for a range of plausible dust extinction values. The best-fit models yield $(M_\mathrm{BH}/10^9\,M_\odot)=2.08\pm0.01(\mathrm{stat})^{+0.32}_{-0.14}(\mathrm{sys})$ for NGC 315 and $(M_\mathrm{BH}/10^9\,M_\odot)=1.67\pm0.10(\mathrm{stat})^{+0.39}_{-0.24}(\mathrm{sys})$ for NGC 4261, the latter of which is larger than previous estimates by a factor of $\sim$3. The BH masses are broadly consistent with the relations between BH masses and host galaxy properties. These are among the first ALMA observations to map dynamically cold gas kinematics well within the BH-dominated regions of radio galaxies, resolving the respective $r_\mathrm{g}$ by factors of $\sim$5$-$10. The observations demonstrate ALMA's ability to precisely measure BH masses in active galaxies, which will enable more confident probes of accretion physics for the most massive galaxies.

astro-ph.GA↗

arXiv2019

A Precision Measurement of the Mass of the Black Hole in NGC 3258 from High-Resolution ALMA Observations of its Circumnuclear Disk

We present $\sim0.10^{\prime\prime}-$resolution Atacama Large Millimeter/submillimeter Array (ALMA) CO(2$-$1) imaging of the arcsecond-scale ($r \approx 150$ pc) dusty molecular disk in the giant elliptical galaxy NGC 3258. The data provide unprecedented resolution of cold gas disk kinematics within the dynamical sphere of influence of a supermassive black hole, revealing a quasi-Keplerian central increase in projected rotation speed rising from 280 km s$^{-1}$ at the disk's outer edge to $>400$ km s$^{-1}$ near the disk center. We construct dynamical models for the rotating disk and fit beam-smeared model CO line profiles directly to the ALMA data cube. Our models incorporate both flat disks and tilted-ring disks that provide a better fit of the mildly warped structure in NGC 3258. We show that the exceptional angular resolution of the ALMA data makes it possible to infer the host galaxy's mass profile within $r=150$ pc solely from the ALMA CO kinematics, without relying on optical or near-infrared imaging data to determine the stellar mass profile. Our model therefore circumvents any uncertainty in the black hole mass that would result from the substantial dust extinction in the galaxy's central region. The best model fit yields $M_\mathrm{BH} = 2.249\times10^9$ $M_\odot$ with a statistical model-fitting uncertainty of just 0.18\%, and systematic uncertainties of 0.62\% from various aspects of the model construction and 12\% from uncertainty in the distance to NGC 3258. This observation demonstrates the full potential of ALMA for carrying out highly precise measurements of $M_\mathrm{BH}$ in early-type galaxies containing circumnuclear gas disks

astro-ph.GA↗

arXiv2018

Science with an ngVLA: Precision Gas-dynamical Mass Measurement of Supermassive Black Holes with the ngVLA

Emission line observations of circumnuclear gas disks in the ALMA era have begun to resolve molecular gas tracer kinematics near supermassive black holes (BHs), enabling highly precise mass determination in the best cases. The ngVLA is capable of extremely high spatial resolution imaging of the CO(1-0) transition at 115 GHz for nearby galaxies. Furthermore, its high (anticipated) emission line sensitivity suggests this array can produce benchmark BH mass measurements. We discuss lessons learned from gas-dynamical modeling of recent ALMA data sets and also compare ALMA and ngVLA CO simulations of a dynamically cold disk. While only a fraction of all local galaxies likely possess sufficiently bright, regularly-rotating nuclear molecular gas, in such cases the ngVLA is expected to more efficiently resolve such emission arising at a projected 50-100 mas from the central BH.

astro-ph.GA↗

arXiv2017

ALMA Observations of Circumnuclear Disks in Early Type Galaxies: 12CO(2-1) and Continuum Properties

We present results from an Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 2 program to map CO(2-1) emission in nearby early-type galaxies (ETGs) that host circumnuclear gas disks. We obtained $\sim0.3''-$resolution Band 6 observations of seven ETGs selected on the basis of dust disks in Hubble Space Telescope images. We detect CO emission in five at high signal-to-noise ratio with the remaining two only faintly detected. All CO emission is coincident with the dust and is in dynamically cold rotation. Four ETGs show evidence of rapid central rotation; these are prime candidates for higher-resolution ALMA observations to measure the black hole masses. In this paper we focus on the molecular gas and continuum properties. Total gas masses and H$_2$ column densities for our five CO-bright galaxies are on average $\sim10^8$ $M_\odot$ and $\sim10^{22.5}$ cm$^{-2}$ over the $\sim$kpc-scale disks, and analysis suggests that these disks are stabilized against gravitational fragmentation. The continuum emission of all seven galaxies is dominated by a central, unresolved source, and in five we also detect a spatially extended component. The $\sim$230 GHz nuclear continua are modeled as power laws ranging from $S_ν\sim ν^{-0.4}$ to $ν^{1.6}$ within the observed frequency band. The extended continuum profiles of the two radio-bright (and CO-faint) galaxies are roughly aligned with their radio jet and suggests resolved synchrotron jets. The extended continua of the CO-bright disks are coincident with optically thick dust absorption and have spectral slopes that are consistent with thermal dust emission.

astro-ph.GA↗

arXiv2016

Measurement of the Black Hole Mass in NGC 1332 from ALMA Observations at 0.044 Arcsecond Resolution

We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 3 observations of CO(2-1) emission from the circumnuclear disk in the E/S0 galaxy NGC 1332 at 0.044" resolution. The disk exhibits regular rotational kinematics and central high-velocity emission (+/-500 km/s) consistent with the presence of a compact central mass. We construct models for a thin, dynamically cold disk in the gravitational potential of the host galaxy and black hole, and fit the beam-smeared model line profiles directly to the ALMA data cube. Model fits successfully reproduce the disk kinematics out to r=200 pc. Fitting models just to spatial pixels within projected r=50 pc of the nucleus (two times larger than the black hole's gravitational radius of influence), we find M_BH=6.64(-0.63,+0.65)*10^8 solar masses. This observation demonstrates ALMA's powerful capability to determine the masses of supermassive black holes by resolving gas kinematics on small angular scales in galaxy nuclei.

astro-ph.GA↗