Grants & Awards

Below is a list of my funding, totalling $1,424,053. You may also want to check out my Orcid page.

The accretion mechanism and SED of black holes at low luminosities are critical questions regarding BHs, but they are still poorly understood. We propose for Chandra data of 22 LLAGN, that combined with existing archival data on 9, will yield a complete data set of all 31 galaxies in the Gemini/NIFS AO LLP black-hole mass campaign. These data will enable massive science: 1. Create the best LLAGN SEDs by virtue of the amount and quality of the data available for a sample with a broad range of black hole masses and Eddington ratios. 2. Specifically study the L_X-L_NIR relation, which is critical for understanding LLAGN and for making the most use of upcoming JWST data. 3. Add value to the Gemini LLP black-hole mass campaign by measuring BH accretion when Gemini find BH mass upper limits.

We propose to carry out a large, uniform, survey for dual AGNs in distant galaxies using archival Chandra surveys. Currently, there is no systematic study of the evolution of dual AGN at high-z; and observational constraints on the dual AGN fraction in the nearby universe are higher than predicted from simulations, resulting in an inconsistent expected dual AGN rate at z>1. We will be able to accurately determine the dual AGN rate (<0.5%), as well as a measure the dual AGN fraction as a function of redshift (<2%). Our tight constraint on the dual AGN fraction as a function of z will allow us to statistically differentiate between the low- and high-end predictions for the fraction of dual AGN across cosmic time.

We propose to observe a sample of 50 nearby (z<0.037) AGN in order to measure the dual AGN fraction in the small-separation regime, where current angular resolution limits have prevented systematic analyses. We will analyze the sample with BAYMAX, a tool we’ve developed that uses a Bayesian framework to quantitatively evaluate whether a given source in a Chandra observation is a single or dual point source for separations <0.5”. We plan to combine this sample with archival observations of 36 AGN to constrain, for the first time, the nearby dual AGN fraction. The outcome of this study will be a measurement of the local dual AGN fraction, to within 2.8%, at smaller limiting separations (14-260 pc) than has ever been done before.

We propose to analyze a sample of 26 nearby (z<0.035) AGN in order to measure the dual AGN fraction in the small-separation regime, where current angular resolution limits have prevented systematic analyses. We will analyze the sample with BAYMAX, a tool we’ve developed that uses a Bayesian framework to quantitatively evaluate whether a given source in a Chandra observation is a single or dual point source for separations <0.5”. We plan to combine this sample with new observations of 55 AGN to constrain, for the first time, the nearby dual AGN fraction. The outcome of this study will be a measurement of the local dual AGN fraction, to within 2.8%, at smaller limiting separations (14-250 pc) than has ever been done before.

We propose a 100 ksec observation of the core of BCG 2261 to test for the presence of a recoiling SMBH. Binary SMBHs are thought to scour out cores in the host galaxy before coalescence of the black holes, which can lead to large recoils. Despite the importance of the connection between binary BHs, strong gravity, and galaxy evolution, it has never been conclusively observed. Without confirmation, we don’t know if binary SMBHs can create stellar cores achieve high recoil velocities. We can produce the first direct observational proof of a recoiling SMBH in BCG 2261, the strongest candidate to date to host a recoiling SMBH and an extreme stellar core. With a detection, we will finally have definitive observational evidence connecting core formation, gravitational waves, and binary BHs.

The frequency of dual AGNs at low galaxy/black hole mass is poorly constrained. Thus we lack a full physical understanding of the connection between galaxy mergers and AGN activity and therefore merger-driven feedback. In particular, it is unknown whether or not LLAGN can be triggered by mergers instead of only by stochastic processes. We will address this with a 50 ksec observation to test for a dual AGN in SDSS J0914+0853, a low-mass (MBH 10^6.3), dual LLAGN candidate based on serendipitous, shallow Chandra imaging. The 15-ksec data showed two X-ray sources, but the nature of the secondary source is ambiguous because of 10% pile-up and potential PSF artifacts. With deeper, short-frame-rate Chandra observations at a new roll angle, we can unambiguously determine if the secondary is real.

Despite the importance of dual AGN to fields such as galaxy formation and gravitational waves, there is no quantitative method for determining whether a given X-ray observation originates from one or two AGN for sources with small (< 0.5″) angular separations. Thus, there exists the possibility that we have over- or under-estimated the rate of dual AGNs. Dual AGNs with small separations can only be distinguished from point sources with advanced analysis. We will develop a Bayesian framework to quantitatively evaluate the odds ratio that a given source is single or dual. This program will allow true surveys and a significant advancement of understanding. The Bayesian framework will also be useful to a number of other fields and will be released to the community.

Changing-look quasars are quasars, deriving their luminosity from gas falling onto supermassive black holes in the centers of distant galaxies, which turn off in less than a decade. They are a new discovery, first observed early last year, and their behavior is astounding because it is a challenge to explain how such massive systems can simply fade in just a few years. There are two scenarios that can explain the dramatic changes between quasar and galaxy-like states. The first is that the quasar, which initially outshone all the stars in its host galaxy, has intrinsically dimmed. Alternatively, a dusty cloud may have moved into our line of sight and blocked our view. The observational tests that distinguish  between these scenarios are often inconclusive leaving the changing-look phenomenon largely unexplained. We have been awarded time on one of the 6.5-meter Magellan telescopes in order to make new observations of 9 changing-look quasars. With the new data, we will find out whether they have turned back on, constraining the duration of the on/off states and telling us whether these quasars are truly off or if they are “flickering.” Additionally, we will be able to distinguish between the intrinsic dimming and dust obscuration scenarios and get a new handle on what causes the changing look of changing-look quasars. This request is to allow the PI to travel to the telescope in Chile, in order to make the observations on the nights of Oct 30 and 31, 2016.

The basics of binary-supermassive-black hole accretion is observationally unconstrained. Without constraints, we are unable to make sound predictions about electromagnetic counterparts to gravitational wave events. We can finally test simulations of circum-binary accretion in PSO J334.2028+01.4075, a strong binary AGN candidate recently discovered by Liu et al. (2015). The two most basic set of predictions from simulations of circum-binary accretion models differ on whether the inner region of the accretion disk is mostly empty (a “cavity”) or if there is substantial accretion onto one or both of the members of the binary. The two predictions differ by orders of magnitude in X-ray flux and thus allow a clear test with a 40 ksec Chandra observation.

We request 8 orbits for STIS spectroscopic observations of three compact knots near the center of the brightest cluster galaxy in Abell 2261 (BCG2261) to directly test for the presence of a recoiling supermassive black hole (SMBH). BCG2261’s exceptionally large, flat core is thought to have been formed by scouring from a binary SMBH inspiral, with additional broadening effects caused by a recoiling SMBH after the binary’s coalescence. A radio jet in the system indicates recent or current active nucleus activity, and appears to point to an origin in one of the off-center stellar concentrations (knots). All of the knots are candidates for a “cloaked” SMBH. Theory predicts that an ejected SMBH should carry a cloak of tightly bound stars with it. The stellar cloak would resemble a globular cluster or dwarf galaxy, but would have a high velocity dispersion. The presence of the off-center knots, the galactic core morphology, and the radio jet tentatively imply that one knot is likely to be cloaking a recoiling SMBH. Our proposed HST/STIS observations will test of the presence of a SMBH in the knots by seeking high-dispersion absorption lines and evidence for active nucleus emission. If any such signature is found, BCG2261 will represent the first direct observational support for three preeminent theoretical speculations: that scouring forms cores, that SMBHs may recoil after coalescence, and that recoil can strongly influence core formation and morphology.

We will measure the X-ray flux and radio continuum of 7 ultramassive BHs (M>3e9) to test competing models of the fundamental plane (FP) of BH accretion. The FP relates the X-ray, radio, and mass of an accreting BH, and demonstrates there is a connection between BH inflow and outflow. The FP is derived mostly from BHs with masses under 2e9. It is not clear if the FP holds for the largest BHs. The 2 ways to create the FP, with only SMBHs OR jointly with SMBHs and stellar BHs, differ by 100 for the largest BHs. Only with Chandra we can separate corona and AGN to determine it. Coronae around huge BHs are critical in limiting feeding so that we can understand the gas supply around and accretion onto the largest BHs.

I request $3,000 to purchase a workstation to carry out data reduction, spectral fitting, and statistical analysis of joint Chandra X-ray and VLA radio data sets approved to be observed from June 2014 to September 2015 (accepted Chandra proposal 16700232). These observations will allow us to discriminate between competing models of the “fundamental plane” of black hole accretion. The fundamental plane relates the X-ray luminosity, radio luminosity, and mass of an accreting black hole, and it demonstrates that there is an intimate connection between inflow and outflow around black holes. Once analyzed, our new data will let us put the sorely missing largest supermassive black holes (SMBHs) on the fundamental plane. Then we can solve a critical question: Do SMBHs and stellar-mass black holes follow the same plane, or do they each follow their own, separate plane? Finally, once we have the full fundamental plane that includes the giant SMBHs (whether it is a single plane or two), we will be able to use the plane as a tool to estimate other SMBH masses with higher fidelity and for sources where other methods are useless. This is especially important for the largest black holes, which are critical players in a number of astrophysical sub-fields.

Massive galaxies represent the extreme of galaxy formation and contain the most massive black holes (BH), as reflected in the scaling relations of BH masses with galaxy velocity dispersions (M–σ) and luminosities (M–L). Our spectroscopic survey of 900 nearby galaxies has already yielded one of the most massive black holes in a remarkably compact galaxy NGC1277. Now we propose to obtain imaging of a nearby galaxy which may host the most massive black hole found to date. This galaxy, UGC2698, lies nearby at a distance of 89 Mpc and has an average size and luminosity, and a extremely high central velocity dispersion of 440 km/s, indicative of black hole mass in excess 10 billion solar masses. With one orbit, we can resolve its small bulge and put accurate constraints on its black hole mass {in combination with our spectroscopy}. If this system also contains a very high black hole mass, it would be in stark conflict with the popular co-evolution picture.

Massive galaxies represent the extreme of galaxy formation and contain the most massive black holes (BH), as reflected in the scaling relations of BH masses with galaxy velocity dispersions (M–σ) and luminosities (M–L). Our spectroscopic survey of 600 nearby galaxies revealed 17 galaxies with extremely high velocity dispersions (indicating BH masses of 10^10 solar masses) and at the same time shockingly small sizes (<2 kpc) and (bulge) luminosities. For one of these galaxies archival HST imaging allowed us to measure an extremely big BH mass of 23 billion solar masses, and confirm it is hosted by a small disk-dominated galaxy of only 90 billion solar masses in stars. This demonstrates that the BH in this system did not co-evolve with its host galaxy the way others are thought to have. It is imperative to go beyond a single anecdotal example to a real sample of galaxies with small bulges and suspected monster black holes. Here we propose to obtain HST imaging of the other 16 galaxies. The WFC3 imaging is required to resolve their small bulge and put accurate constraints (in combination with our spectroscopy) on their black hole mass. A significant sample of compact galaxies with very high black hole masses would be in stark conflict with the popular co-evolution picture and could form the missing link between local galaxies and the quiescent compact nugget galaxies found at z~2.

The fundamental plane relates the X-ray luminosity, radio luminosity, and mass of accreting BHs and demonstrates an intimate connection between BH inflow and outflow. Existing data are mostly from SMBHs with Mbh > 10^7. It is not clear whether the plane holds below this. Small SMBHs are critical to our understanding of BH formation and growth as well as feedback in the early Universe. We propose to survey all known BHs with mass estimates Mbh < 10^6.2 that have no CXO or XMM observations, but have VLA FIRST radio detections. With modest CXO exposures and new EVLA observations of these 7 sources plus 4 archival sources, we can test the robustness of the plan at low-mass and whether accretion properties scale from stellar BHs thus testing how BH feedback scales with mass and accretion rate.

The observed tight correlations between black hole mass and host galaxy properties evince a fundamental connection between their joint evolution. The key to understanding this co-evolution rests on the ability to measure the smallest black hole masses, which closely trace the formation of black holes. But, recent observational evidence suggests the smallest black holes and/or the smallest galaxies (especially pseudobulges) diverge from the scaling relations. There is therefore a pressing need: (1) to firmly establish multiple, independent measures of black hole mass in these smallest objects, and (2) to accurately determine properties of the host galaxy. Unfortunately, low AGN luminosity means that galaxy contamination is a prohibiting issue for normal ground-based measures of BH mass. But, in the UV this is not a problem allowing the use of CIV to measure BH masses through COS spectroscopy. Moreover, with WFC3 imaging we can unambiguously determine the bulge morphology and luminosity. Therefore, only with our proposed HST campaign to study 6 low-luminosity AGN will we be able to test whether or not the smallest black holes in the smallest galaxies are truly aberrations compared to their higher-mass counterparts.

[Original PI was Marta Volonteri.]

This project is a comprehensive theoretical study that will provide a picture of how massive black holes (MBHs) in galaxy centers evolved from early cosmic times to the present day. In the first two parts of the three-part study, coupled gravitational N-body and smooth-particle hydrodynamics simulations will be used by the Principal Investigator and a graduate student to study the growth of MBHs in mergers of galaxies. The first part is aimed at understanding when MBHs form bound pairs following galaxy mergers, and when they light up as single or double active galactic nuclei (AGN). Simulations will explore a range of mass ratios and galaxy morphologies. The second part addresses the dynamical, thermodynamic, and accretion evolution of a MBH pair in a merger remnant. The MBH evolution will be simulated at high resolution, self-consistently following the interplay between accretion and dynamics. The third part of the project will use the simulation results to calculate the evolution of MBH populations along cosmic time, predicting how many MBH mergers are expected in the Universe, and how often AGN occur in merging galaxies. The predicted observables will be: (i) frequency of MBHs in galaxies as a function of galaxy mass and cosmic time, (ii) statistics on double AGNs, and on the luminosity functions of AGN at different redshifts and wavelengths, and (iii) potentially detectable gravitational wave event rates from mergers. The proposed research will constrain the dynamics and mass growth of MBHs during mergers and their frequency in galaxies, key information for models of galaxy evolution. The project will contribute to training the next generation of scientists through support of a doctoral student. In an outreach component, undergraduate students will develop critical thinking by designing a museum exhibit dealing with common misconceptions on black holes.

Galaxies with dynamically-measured central BH masses allow us to understand BH accretion, jets, and interactions between BHs and host galaxies with a clarity not possible in random surveys. By measuring true Eddington fractions, we can calculate the energy in radiation vs mechanical jet energy and the efficacy of BHs in heating nuclear regions and affecting star formation. Remarkably, 1/3 of SMBHs making up the M-sigma relation have been poorly observed or totally unobserved with Chandra. We propose a survey of 15 M-sigma galaxies to complete the sample of reliable M-sigma SMBHs. For each galaxy we propose to obtain 30-60 ks exposures and an hour-long VLA observation. This survey will test and extend the fundamental plane of BH activity and facilitate studies of the origin of M-sigma.