Abstract
Recent studies have revealed a strong relation between the sample-averaged black hole (BH) accretion rate (BHAR) and star formation rate (SFR) among bulge-dominated galaxies—i.e., “lockstep” ...BH–bulge growth—in the distant universe. This relation might be closely connected to the BH–bulge mass correlation observed in the local universe. To further understand BH–bulge coevolution, we present Atacama Large Millimeter/submillimeter Array (ALMA) CO(2–1) or CO(3–2) observations of seven star-forming bulge-dominated galaxies at
z
= 0.5–2.5. Using the ALMA data, we detect significant (>3
σ
) CO emission from four objects. For our sample of seven galaxies, we measure (or constrain with upper limits) their CO line fluxes and estimate their molecular gas masses (
M
gas
). We also estimate their stellar masses (
M
star
) and SFRs, by modeling their spectral energy distributions. Using these physical properties, we derive the gas depletion timescales (
τ
dep
≡
M
gas
/SFR) and compare them with the bulge/BH growth timescales (
τ
grow
≡
M
star
/SFR ∼
M
BH
/BHAR). Our sample generally has
τ
dep
shorter than
τ
grow
by a median factor of ≳4, indicating that the cold gas will be depleted before significant bulge/BH growth takes place. This result suggests that BH–bulge lockstep growth is mainly responsible for maintaining the mass relation, not creating it. We note that our sample is small and limited to
z
< 2.5; JWST and ALMA will be able to probe to higher redshifts in the near future.
We present velocity-delay maps for optical H I, He I, and He II recombination lines in Arp 151, recovered by fitting a reverberation model to spectrophotometric monitoring data using the ...maximum-entropy method. H I response is detected over the range 0-15 days, with the response confined within the virial envelope. The Balmer-line maps have similar morphologies but exhibit radial stratification, with progressively longer delays for H{gamma} to H{beta} to H{alpha}. The He I and He II response is confined within 1-2 days. There is a deficit of prompt response in the Balmer-line cores but strong prompt response in the red wings. Comparison with simple models identifies two classes that reproduce these features: free-falling gas and a half-illuminated disk with a hot spot at small radius on the receding lune. Symmetrically illuminated models with gas orbiting in an inclined disk or an isotropic distribution of randomly inclined circular orbits can reproduce the virial structure but not the observed asymmetry. Radial outflows are also largely ruled out by the observed asymmetry. A warped-disk geometry provides a physically plausible mechanism for the asymmetric illumination and hot spot features. Simple estimates show that a disk in the broad-line region of Arp 151 could be unstable to warping induced by radiation pressure. Our results demonstrate the potential power of detailed modeling combined with monitoring campaigns at higher cadence to characterize the gas kinematics and physical processes that give rise to the broad emission lines in active galactic nuclei.
ABSTRACT
We have used Hubble Space Telescope (HST) images, SAURON Integral Field Spectroscopy (IFS), and adaptative optics assisted Gemini NIFS near-infrared K-band IFS to map the stellar and gas ...distribution, excitation and kinematics of the inner few kpc of the nearby edge-on S0 galaxy NGC 4111. The HST images map its ≈450 pc diameter dusty polar ring, with an estimated gas mass ≥107 M⊙. The NIFS data cube maps the inner 110 pc radius at ≈7 pc spatial resolution, revealing a ≈220 pc diameter polar ring in hot (2267 ± 166 K) molecular H2 1–0 S(1) gas embedded in the polar ring. The stellar velocity field shows disc-dominated kinematics along the galaxy plane both in the SAURON large scale and in the NIFS nuclear-scale data. The large-scale O iii λ5007 Å velocity field shows a superposition of two disc kinematics: one similar to that of the stars and another along the polar ring, showing non-circular motions that seem to connect with the velocity field of the nuclear H2 ring, whose kinematics indicate accelerated inflow to the nucleus. The estimated mass inflow rate is enough not only to feed an active galactic nucleus (AGN) but also to trigger circumnuclear star formation in the near future. We propose a scenario in which gas from the polar ring, which probably originated from the capture of a dwarf galaxy, is moving inwards and triggering an AGN, as supported by the local X-ray emission, which seems to be the source of the H2 1–0 S(1) excitation. The fact that we see neither near-UV nor Br γ emission suggests that the nascent AGN is still deeply buried under the optically thick dust of the polar ring.
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 ∼0 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 H2 column densities for our five CO-bright galaxies are on average ∼108 M☉ and cm−2 over the ∼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 ∼230 GHz nuclear continua are modeled as power laws ranging from to 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 suggest 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.
The Seyfert 1 galaxy Zw 229-015 is among the brightest active galaxies being monitored by the Kepler mission. In order to determine the black hole mass in Zw 229-015 from H Delta *b reverberation ...mapping, we have carried out nightly observations with the Kast Spectrograph at the Lick 3 m telescope during the dark runs from 2010 June through December, obtaining 54 spectroscopic observations in total. We have also obtained nightly V-band imaging with the Katzman Automatic Imaging Telescope at Lick Observatory and with the 0.9 m telescope at the Brigham Young University West Mountain Observatory over the same period. We detect strong variability in the source, which exhibited more than a factor of two change in broad H Delta *b flux. From cross-correlation measurements, we find that the H Delta *b light curve has a rest-frame lag of 3.86+0.69 --0.90 days with respect to the V-band continuum variations. We also measure reverberation lags for H Delta *a and H Delta *g and find an upper limit to the H Delta *d lag. Combining the H Delta *b lag measurement with a broad H Delta *b width of Delta *sline = 1590 ? 47 km s--1 measured from the rms variability spectrum, we obtain a virial estimate of M BH = 1.00+0.19 --0.24 X 107 M for the black hole in Zw 229-015. As a Kepler target, Zw 229-015 will eventually have one of the highest-quality optical light curves ever measured for any active galaxy, and the black hole mass determined from reverberation mapping will serve as a benchmark for testing relationships between black hole mass and continuum variability characteristics in active galactic nuclei.
The Lick AGN Monitoring Project 2011 observing campaign was carried out over the course of 11 weeks in spring 2011. Here we present the first results from this program, a measurement of the ...broad-line reverberation lag in the Seyfert 1 galaxy Mrk 50. Combining our data with supplemental observations obtained prior to the start of the main observing campaign, our data set covers a total duration of 4.5 months. During this time, Mrk 50 was highly variable, exhibiting a maximum variability amplitude of a factor of ~4 in the U-band continuum and a factor of ~2 in the H Delta *b line. Using standard cross-correlation techniques, we find that H Delta *b and H Delta *g lag the V-band continuum by Delta *tcen = 10.64+0.82 -- 0.93 and 8.43+1.30 -- 1.28 days, respectively, while the lag of He II Delta *l4686 is unresolved. The H Delta *b line exhibits a symmetric velocity-resolved reverberation signature with shorter lags in the high-velocity wings than in the line core, consistent with an origin in a broad-line region (BLR) dominated by orbital motion rather than infall or outflow. Assuming a virial normalization factor of f = 5.25, the virial estimate of the black hole mass is (3.2 ? 0.5) X 107 M . These observations demonstrate that Mrk 50 is among the most promising nearby active galaxies for detailed investigations of BLR structure and dynamics.
We investigate the compact, early-type galaxy NGC 1281 with integral field unit observations to map the stellar line-of-sight velocity distribution (LOSVD) out to five effective radii and construct ...orbit-based dynamical models to constrain its dark and luminous matter content. Under the assumption of mass-follows-light, the H-band stellar mass-to-light ratio (M/L) is ϒ⋆ = 2.7 ± 0.1 ϒ⊙, and higher than expected from our stellar population synthesis fits with either a canonical Kroupa (ϒ⋆ = 1.3 ϒ⊙) or Salpeter (ϒ⋆ = 1.7 ϒ⊙) stellar initial mass function. Such models also cannot reproduce the details of the LOSVD. Models with a dark halo recover the kinematics well and indicate that NGC 1281 is dark matter dominated, making up ∼ 90 per cent of the total enclosed mass within the kinematic bounds. Parametrized as a spherical NFW profile, the dark halo mass is 11.5 ≤ log(M
DM/M⊙) ≤ 11.8 and the stellar M/L is 0.6 ≤ ϒ⋆/ϒ⊙ ≤ 1.1. However, this M/L is lower than predicted by its old stellar population. Moreover, the halo mass within the kinematic extent is 10 times larger than expected based on Λ-cold-dark-matter predictions, and an extrapolation yields cluster-sized dark halo masses. Adopting ϒ⋆ = 1.7 ϒ⊙ yields more moderate dark halo virial masses, but these models fit the kinematics worse. A non-NFW model might solve the discrepancy between the unphysical consequences of the best-fitting dynamical models and models based on more reasonable assumptions for the dark halo and stellar M/L, which are disfavoured according to our parameter estimation.
It is now possible to estimate black hole (BH) masses across cosmic time, using broad emission lines in active galaxies. This technique informs our views of how galaxies and their central BHs ...coevolve. Unfortunately, there are many outstanding uncertainties associated with these 'virial' mass estimates. One of these comes from using the accretion luminosity to infer a size for the broad-line region (BLR). Incorporating the new sample of low-luminosity active galaxies from our recent monitoring campaign at Lick Observatory, we recalibrate the radius-luminosity relation with tracers of the accretion luminosity other than the optical continuum. We find that the radius of the BLR scales as the square root of the X-ray and H Delta *b luminosities, in agreement with recent optical studies. On the other hand, the scaling appears to be marginally steeper with narrow-line luminosities. This is consistent with a previously observed decrease in the ratio of narrow-line to X-ray luminosity with increasing total luminosity. The radius of the BLR correlates most tightly with H Delta *b luminosity, while the X-ray and narrow-line relations both have comparable scatter of a factor of 2. These correlations provide useful alternative virial BH masses in objects with no detectable optical/UV continuum emission, such as high-redshift galaxies with broad emission lines, radio-loud objects, or local active galaxies with galaxy-dominated continua.
The Lick AGN Monitoring Project targeted 13 nearby Seyfert 1 galaxies with the intent of measuring the masses of their central black holes using reverberation mapping. The sample includes 12 galaxies ...selected to have black holes with masses roughly in the range 106-107 M, as well as the well-studied active galactic nucleus (AGN) NGC 5548. In conjunction with a spectroscopic monitoring campaign, we obtained broadband B and V images on most nights from 2008 February through 2008 May. The imaging observations were carried out by four telescopes: the 0.76 m Katzman Automatic Imaging Telescope, the 2 m Multicolor Active Galactic Nuclei Monitoring telescope, the Palomar 60 inch (1.5 m) telescope, and the 0.80 m Tenagra II telescope. Having well-sampled light curves over the course of a few months is useful for obtaining the broad-line reverberation lag and black hole mass, and also allows us to examine the characteristics of the continuum variability. In this paper, we discuss the observational methods and the photometric measurements, and present the AGN continuum light curves. We measure various variability characteristics of each of the light curves. We do not detect any evidence for a time lag between the B- and V-band variations, and we do not find significant color variations for the AGNs in our sample.
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