arXiv subjects

Jenny Greene

Publications and source records attributed to Jenny Greene.

At least 37 records · Page 2Linked to original sources

arXiv2022

Gas inflows in the polar ring of NGC 4111: the birth of an AGN

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 $\approx$ 450 pc diameter dusty polar ring, with an estimated gas mass $\ge10^7$ M$_\odot$. The NIFS datacube maps the inner 110 pc radius at $\approx$ 7 pc spatial resolution revealing a $\approx$ 220 pc diameter polar ring in hot ($2267\pm166$ K) molecular H$_2$ 1-0 S(1) gas embedded in the polar ring. The stellar velocity field shows disk-dominated kinematics along the galaxy plane both in the SAURON large-scale and in the NIFS nuclear-scale data. The large-scale [O III] $\lambda5007$ Åvelocity field shows a superposition of two disk 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 H$_2$ 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 H$_2$ 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.

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arXiv2022

The Prime Focus Spectrograph Galaxy Evolution Survey

We present the Prime Focus Spectrograph (PFS) Galaxy Evolution pillar of the 360-night PFS Subaru Strategic Program. This 130-night program will capitalize on the wide wavelength coverage and massive multiplexing capabilities of PFS to study the evolution of typical galaxies from cosmic dawn to the present. From Lyman alpha emitters at z~7 to probe reionization, drop-outs at z~3 to map the inter-galactic medium in absorption, and a continuum-selected sample at z~1.5, we will chart the physics of galaxy evolution within the evolving cosmic web. This article is dedicated to the memory of Olivier Le Fevre, who was an early advocate for the construction of PFS, and a key early member of the Galaxy Evolution Working Group.

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arXiv2022

The black hole population in low-mass galaxies in large-scale cosmological simulations

Recent systematic searches for massive black holes (BHs) in local dwarf galaxies led to the discovery of a population of faint Active Galactic Nuclei (AGN). We investigate the agreement of the BH and AGN populations in the Illustris, TNG, Horizon-AGN, EAGLE, and SIMBA simulations with current observational constraints in low-mass galaxies. We find that some of these simulations produce BHs that are too massive, and that the BH occupation fraction at z=0 is not inherited from the simulation seeding modeling. The ability of BHs and their host galaxies to power an AGN depends on BH and galaxy subgrid modeling. The fraction of AGN in low-mass galaxies is not used to calibrate the simulations, and thus can be used to differentiate galaxy formation models. AGN fractions at z=0 span two orders of magnitude at fixed galaxy stellar mass in simulations, similarly to observational constraints, but uncertainties and degeneracies affect both observations and simulations. The agreement is difficult to interpret due to differences in the masses of simulated and observed BHs, BH occupation fraction affected by numerical choices, and an unknown fraction of obscured AGN. Our work advocates for more thorough comparisons with observations to improve the modeling of cosmological simulations, and our understanding of BH and galaxy physics in the low-mass regime. The mass of BHs, their ability to efficiently accrete gas, and the AGN fraction in low-mass galaxies have important implications for the build-up of the entire BH and galaxy populations with time.

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arXiv2022

SDSS-IV MaNGA: Cannibalism Caught in the Act -- on the Frequency of Occurrence of Multiple Cores in Brightest Cluster Galaxies

Although it is generally accepted that massive galaxies form in a two-phased fashion, beginning with a rapid mass buildup through intense starburst activities, followed by primarily dry mergers that mainly deposit stellar mass at outskirts, the late time stellar mass growth of brightest cluster galaxies (BCGs), the most massive galaxies in the universe, is still not well understood. Several independent measurements have indicated a slower mass growth rate than predictions from theoretical models. We attempt to resolve the discrepancy by measuring the frequency of BCGs with multiple-cores, which serve as a proxy of the merger rates in the central region and facilitate a more direct comparison with theoretical predictions. Using 79 BCGs at $z=0.06-0.15$ with integral field spectroscopic (IFS) data from the Mapping Nearby Galaxies at APO (MaNGA) project, we obtain a multiple-core fraction of $0.11 \pm 0.04$ at $z\approx 0.1$ within a 18 kpc radius from the center, which is comparable to the value of $0.08 \pm 0.04$ derived from mock observations of 218 simulated BCGs from the cosmological hydrodynamical simulation IllustrisTNG. We find that most of cores that appear close to the BCGs from imaging data turn out to be physically associated systems. Anchoring on the similarity in the multiple-core frequency between the MaNGA and IllustrisTNG, we discuss the mass growth rate of BCGs over the past 4.5 Gyr.

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arXiv2022

Next Generation Observatories -- Report from the Dawn VI Workshop; October 5-7 2021

The workshop Dawn VI: Next Generation Observatories took place online over three days, 5-7 October, 2021. More than 200 physicists and astronomers attended to contribute to, and learn from, a discussion of next-generation ground-based gravitational-wave detectors. The program was centered on the next generation of ground-based gravitational-wave observatories and their synergy with the greater landscape of scientific observatories of the 2030s. Cosmic Explorer (CE), a concept developed with US National Science Foundation support, was a particular focus; Einstein Telescope (ET), the European next generation concept, is an important complement and partner in forming a network. The concluding summary of the meeting expressed the sentiment that the observational science accessible to CE and ET, also in combination with data from other non-GW observatories, will stimulate a very broad community of analysts and yield insights which are exciting given the access to GWs from the entire universe. The need, and desire, for closer collaboration between ET and CE was expressed; a three-detector network is optimal for delivering much of the science. The science opportunities afforded by CE and ET are broad and compelling, impacting a wide range of disciplines in physics and high energy astrophysics. There was a consensus that CE is a concept that can deliver the promised science. A strong endorsement of Cosmic Explorer, as described in the CE Horizon Study, is a primary outcome of DAWN VI.

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arXiv2021

The MASSIVE SURVEY XVI. The Stellar Initial Mass Function in the Center of MASSIVE Early-Type Galaxies

The stellar initial mass function (IMF) is a fundamental property in the measurement of stellar masses and galaxy star formation histories. In this work we focus on the most massive galaxies in the nearby universe $\log(M_{\star}/M_{\odot})>11.2$. We obtain high quality Magellan/LDSS-3 long slit spectroscopy with a wide wavelength coverage of $0.4μ{\rm m}-1.01μ{\rm m}$ for 41 early-type galaxies (ETGs) in the MASSIVE survey, and derive high S/N spectra within an aperture of $R_{\rm e}/8$. Using detailed stellar synthesis models, we constrain the elemental abundances and stellar IMF of each galaxy through full spectral modeling. All the ETGs in our sample have an IMF that is steeper than a Milky Way (Kroupa) IMF. The best-fit IMF mismatch parameter, $α_{\rm IMF}=(M/L)/(M/L)_{\rm MW}$, ranges from 1.12 to 3.05, with an average of $\langle α_{\rm IMF} \rangle=1.84$, suggesting that on average, the IMF is more bottom-heavy than Salpeter. Comparing the estimated stellar mass with the dynamical mass, we find that most galaxies have stellar masses smaller than their dynamical masses within the $1σ$ uncertainty. We complement our sample with lower-mass galaxies from the literature, and confirm that $\log(α_{\rm IMF})$ is positively correlated with $\log(σ)$, $\log(M_{\star})$, and $\log(M_{\rm dyn})$. The IMF in the centers of more massive ETGs is more bottom-heavy. In addition, we find that $\log(α_{\rm IMF})$ is positively correlated with both [Mg/Fe] and the estimated total metallicity [Z/H]. We find suggestive evidence that the effective stellar surface density $Σ_{\rm Kroupa}$ might be responsible for the variation of $α_{\rm IMF}$. We conclude that $σ$, [Mg/Fe] and [Z/H] are the primary drivers of the global stellar IMF variation.

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arXiv2021

The Outer Stellar Mass of Massive Galaxies: A Simple Tracer of Halo Mass with Scatter Comparable to Richness and Reduced Projection Effects

Using the weak gravitational lensing data from the Hyper Suprime-Cam Subaru Strategic Program (HSC survey), we study the potential of different stellar mass estimates in tracing halo mass. We consider galaxies with $\log {M_{\star}/M_{\odot}}>11.5$ at 0.2 < z < 0.5 with carefully measured light profiles and clusters from the redMaPPer and CAMIRA richness-based algorithms. We devise a method (the "TopN" test) to evaluate the scatter in the halo mass-observable relation for different tracers and inter-compare halo mass proxies in four number density bins using stacked galaxy-galaxy lensing profiles. This test reveals three key findings. The stellar mass based on cModel photometry or aperture luminosity within R<30 kpc is a poor proxy of halo mass. In contrast, the stellar mass of the outer envelope is an excellent halo mass proxy. The stellar mass within R=[50,100] kpc, M*[50,100], has performance comparable to the state-of-the-art richness-based cluster finders at $\log{M_{\rm vir}/M_{\odot}}>14.0$ and could be a better halo mass tracer at lower halo masses. Finally, using N-body simulations, we find that the lensing profiles of massive halos selected by M*[50,100] are consistent with the expectation for a sample without projection or mis-centering effects. On the other hand, Richness-selected clusters display an excess at R~1 Mpc in their lensing profiles, which may suggest a more significant impact from selection biases. These results suggest that Mstar-based tracers have distinct advantages in identifying massive halos, which could open up new avenues for cluster cosmology.

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arXiv2020

Stellar and Weak Lensing Profiles of Massive Galaxies in the Hyper-Suprime Cam Survey and in Hydrodynamic Simulations

We perform a consistent comparison of the mass and mass profiles of massive ($M_\star > 10^{11.4}M_{\odot}$) central galaxies at z~0.4 from deep Hyper Suprime-Cam (HSC) observations and from the Illustris, TNG100, and Ponos simulations. Weak lensing measurements from HSC enable measurements at fixed halo mass and provide constraints on the strength and impact of feedback at different halo mass scales. We compare the stellar mass function (SMF) and the Stellar-to-Halo Mass Relation (SHMR) at various radii and show that the radius at which the comparison is performed is important. In general, Illustris and TNG100 display steeper values of $α$ where $M_{\star}\propto M_{\rm vir}^α$. These differences are more pronounced for Illustris than for TNG100 and in the inner rather than outer regions of galaxies. Differences in the inner regions may suggest that TNG100 is too efficient at quenching in-situ star formation at $M_{\rm vir}\simeq10^{13} M_{\odot}$ but not efficient enough at $M_{\rm vir}\simeq10^{14} M_{\odot}$. The outer stellar masses are in excellent agreement with our observations at $M_{\rm vir}\simeq10^{13} M_{\odot}$, but both Illustris and TNG100 display excess outer mass as $M_{\rm vir}\simeq10^{14} M_{\odot}$ (by ~0.25 and ~0.12 dex, respectively). We argue that reducing stellar growth at early times in $M_\star \sim 10^{9-10} M_{\odot}$ galaxies would help to prevent excess ex-situ growth at this mass scale. The Ponos simulations do not implement AGN feedback and display an excess mass of ~0.5 dex at $r<30$ kpc compared to HSC which is indicative of over-cooling and excess star formation in the central regions. Joint comparisons between weak lensing and galaxy stellar profiles are a direct test of whether simulations build and deposit galaxy mass in the correct dark matter halos and thereby provide powerful constraints on the physics of feedback and galaxy growth.

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arXiv2020

Nuclear X-ray Activity in Low-Surface-Brightness Galaxies: Prospects for Constraining the Local Black Hole Occupation Fraction with a Chandra Successor Mission

About half of nearby galaxies have a central surface brightness >1 magnitude below that of the sky. The overall properties of these low-surface-brightness galaxies (LSBGs) remain understudied, and in particular we know very little about their massive black hole population. This gap must be closed to determine the frequency of massive black holes at z=0 as well as to understand their role in regulating galaxy evolution. Here we investigate the incidence and intensity of nuclear, accretion-powered X-ray emission in a sample of 32 nearby LSBGs with the Chandra X-ray Observatory. A nuclear X-ray source is detected in 4 galaxies (12.5%). Based on an X-ray binary contamination assessment technique developed for normal galaxies, we conclude that the detected X-ray nuclei indicate low-level accretion from massive black holes. The active fraction is consistent with that expected from the stellar mass distribution of the LSBGs, but not their total baryonic mass, when using a scaling relation from an unbiased X-ray survey of normal galaxies. This suggests that their black holes co-evolved with their stellar population. In addition, the apparent agreement nearly doubles the number of galaxies available within ~100 Mpc for which a measurement of nuclear activity can efficiently constrain the frequency of black holes as a function of stellar mass. We conclude by discussing the feasibility of measuring this occupation fraction to a few percent precision below 1e10 solar masses with high-resolution, wide-field X-ray missions currently under consideration.

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arXiv2020

A Mystery in Chamaeleon: Serendipitous Discovery of a Galactic Symbiotic Nova

We present the serendipitous discovery of a low luminosity nova occurring in a symbiotic binary star system in the Milky Way. We lay out the extensive archival data alongside new follow-up observations related to the stellar object V$^*$ CN Cha in the constellation of Chamaeleon. The object had long period ($\sim\! 250\,$day), high amplitude ($\sim\! 3\,$mag) optical variability in its recent past, preceding an increase in optical brightness by $\sim\! 8\,$magnitudes and a persistence at this luminosity for about 3 years, followed by a period of $\sim\! 1.4\,{\rm mag}\,{\rm yr}^{-1}$ dimming. The object's current optical luminosity seems to be dominated by H$α$ emission, which also exhibits blue-shifted absorption (a P-Cygni-like profile). After consideration of a number of theories to explain these myriad observations, we determine that V$^*$ CN Cha is most likely a symbiotic (an evolved star-white dwarf binary) system which has undergone a long-duration, low luminosity, nova. Interpreted in this way, the outburst in V$^*$ CN Cha is among the lowest luminosity novae ever observed.

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arXiv2019

A search for optical AGN variability in 35,000 low-mass galaxies with the Palomar Transient Factory

We present an analysis of the long-term optical variability for $\sim50,000$ nearby (z<0.055) galaxies from the NASA-Sloan Atlas, $35,000$ of which are low-mass ($M_{\ast}<10^{10}~M_{\odot}$). We use difference imaging of Palomar Transient Factory (PTF) R-band observations to construct light curves with typical baselines of several years. We then search for subtle variations in the nuclear light output. We determine whether detected variability is AGN-like by assessing the fit quality to a damped random walk model. We identify 424 variability-selected AGN, including 244 with stellar masses between $10^{7}$ and $10^{10}~M_{\odot}$. 75% of low-mass galaxies with AGN-like variability have narrow emission lines dominated by star formation. After controlling for nucleus magnitude, the fraction of variable AGN is constant down to $M_{\ast}=10^{9}~M_{\odot}$, suggesting no drastic decline in the BH occupation fraction down to this stellar mass regime. Combining our NASA-Sloan Atlas sample with samples of nearby galaxies with broad H$α$ emission, we find no dependence of variability properties with black hole mass. However, we caution that the variable AGN fraction is strongly dependent on baseline. For baselines less than two years, the variable fraction for the full sample is 0.25%, compared to 1.0% for baselines longer than two years. Finally, comparing Stripe 82 light curves (Baldassare et al. 2018) to PTF light curves, we find populations of changing-look AGN: 8 galaxies that are variable in Stripe 82, but quiescent in PTF, and 15 galaxies where the reverse is true. Our PTF work demonstrates the promise of long-term optical variability searches in low-mass galaxies for finding AGNs missed by other selection techniques.

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arXiv2019

HSC-XD 52: An X-ray detected AGN in a low-mass galaxy at $z\sim0.56$

The properties of low-mass galaxies hosting central black holes provide clues about the formation and evolution of the progenitors of supermassive black holes. In this letter, we present HSC-XD 52, a spectroscopically confirmed low-mass active galactic nucleus (AGN) at an intermediate redshift of $z\sim0.56$. We detect this object as a very luminous X-ray source coincident with a galaxy observed by the Hyper Suprime-Cam (HSC) as part of a broader search for low-mass AGN. We constrain its stellar mass through spectral energy distribution modeling to be LMC-like at $M_\star \approx 3 \times 10^9 M_\odot$, placing it in the dwarf regime. We estimate a central black hole mass of $M_\mathrm{BH} \sim 10^{6} M_\odot$. With an average X-ray luminosity of $L_X \approx 3.5 \times 10^{43}~\mathrm{erg}~\mathrm{s}^{-1}$, HSC-XD 52 is among the most luminous X-ray selected AGN in dwarf galaxies. The spectroscopic and photometric properties of HSC-XD 52 indicate that it is an intermediate redshift counterpart to local low-mass AGN.

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arXiv2019

A New Sample of (Wandering) Massive Black Holes in Dwarf Galaxies from High Resolution Radio Observations

We present a sample of nearby dwarf galaxies with radio-selected accreting massive black holes (BHs), the majority of which are non-nuclear. We observed 111 galaxies using sensitive, high-resolution observations from the Karl G. Jansky Very Large Array (VLA) in its most extended A-configuration at X-band (~8-12 GHz), yielding a typical angular resolution of ~0.25" and rms noise of ~15 uJy. Our targets were selected by cross matching galaxies with stellar masses M_stellar < 3 x 10^9 M_sun and redshifts z<0.055 in the NASA-Sloan Atlas with the VLA Faint Images of the Radio Sky at Twenty centimeters (FIRST) Survey. With our new high-resolution VLA observations, we detect compact radio sources towards 39 galaxies and carefully evaluate possible origins for the radio emission including thermal HII regions, supernova remnants, younger radio supernovae, background interlopers, and AGNs in the target galaxies. We find that 13 dwarf galaxies almost certainly host active massive BHs despite the fact that only one object was previously identified as having optical signatures of an AGN. We also identify a candidate dual radio AGN in a more massive galaxy system. The majority of the radio-detected BHs are offset from the center of the host galaxies with some systems showing signs of interactions/mergers. Our results indicate that massive BHs need not always live in the nuclei of dwarf galaxies, confirming predictions from simulations. Moreover, searches attempting to constrain BH seed formation using observations of dwarf galaxies need to account for such a population of "wandering" BHs.

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arXiv2019

The Black Hole -- Bulge Mass Relation including Dwarf Galaxies Hosting Active Galactic Nuclei

We present a new relationship between central black hole (BH) mass and host galaxy stellar bulge mass extending to the lowest BH masses known in dwarf galaxies ($M_{\rm BH} \lesssim 10^{5} M_{\odot}$; $M_{\star} \sim 10^{9} M_{\odot}$). We have obtained visible and near-infrared $Hubble \ Space \ Telescope \ (HST)$ imaging of seven dwarf galaxies with optically-selected broad-line active galactic nuclei (AGN) and BH mass estimates from single epoch spectroscopy. We perform 2D photometric modeling with GALFIT to decompose the structure of these galaxies and find that the majority have an inner bulge/pseudobulge component with an exponential disk that dominates the total stellar mass. Using the modeling results and color-dependent mass-to-light ratios, we determine the stellar mass of each photometric component in each galaxy. We determine the $M_{\rm BH} - M_{\rm bulge}$ relation using a total of 12 dwarf galaxies hosting broad-line AGNs, along with a comparison sample of 88 galaxies with dynamical BH masses and 37 reverberation-mapped AGNs. We find a strong correlation between BH mass and bulge mass with ${\rm log}(M_{\rm BH}/M_\odot) = (1.24\pm 0.08)~{\rm log}(M_{\rm bulge}/10^{11} M_\odot) + (8.80\pm 0.09)$. The near-linear slope and normalization are in good agreement with correlations found previously when only considering higher mass systems. This work has quadrupled the number of dwarf galaxies on the BH-bulge mass relation, with implications for BH seeding and predictions for gravitational wave detections of merging BHs at higher redshifts with $LISA$.

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arXiv2019

SpecTel: A 10-12 meter class Spectroscopic Survey Telescope

We recommend a conceptual design study for a spectroscopic facility in the southern hemisphere comprising a large diameter telescope, fiber system, and spectrographs collectively optimized for massively-multiplexed spectroscopy. As a baseline, we propose an 11.4-meter aperture, optical spectroscopic survey telescope with a five square degree field of view. Using current technologies, the facility could be equipped with 15,000 robotically-controlled fibers feeding spectrographs over 360<lambda<1330 nm with options for fiber-fed spectrographs at high resolution and a panoramic IFU at a separate focus. This would enable transformational progress via its ability to access a larger fraction of objects from Gaia, LSST, Euclid, and WFIRST than any currently funded or planned spectroscopic facility. An ESO-sponsored study (arXiv:1701.01976) discussed the scientific potential in ambitious new spectroscopic surveys in Galactic astronomy, extragalactic astronomy, and cosmology. The US community should establish links with European and other international communities to plan for such a powerful facility and maximize the potential of large aperture multi-object spectroscopy given the considerable investment in deep imaging surveys.

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arXiv2019

Disentangling nature from nurture: tracing the origin of seed black holes

The origin and properties of black hole seeds that grow to produce the detected population of supermassive black holes are unconstrained at present. Despite the existence of several potentially feasible channels for the production of initial seeds in the high redshift universe, since even actively growing seeds are not directly observable at these epochs, discriminating between models remains challenging. Several new observables that encapsulate information about seeding have been proposed in recent years, and these offer exciting prospects for truly unraveling the nature of black hole seeds in the coming years. One of the key challenges for this task lies in the complexity of the problem, the required disentangling of the confounding effects of accretion physics and mergers, as mergers and accretion events over cosmic time stand to erase these initial conditions. Nevertheless, some unique signatures of seeding do survive and still exist in: local scaling relations between black holes and their galaxy hosts at low-masses; in high-redshift luminosity functions of accreting black holes; and in the total number and mass functions of gravitational wave coalescence events from merging binary black holes. One of the clearest discriminants for seed models are these high redshift gravitational wave detections of mergers from space detectable in the milliHertz range. These predicted event rates offer the most direct constraints on the properties of initial black hole seeds. Improving our theoretical understanding of black hole dynamics and accretion will also be pivotal in constraining seeding models in combination with the wide range of multi-messenger data.

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arXiv2019

Astro2020 Science White Paper: Black Holes Across Cosmic Time

Supermassive black holes are located at the center of most, if not all, massive galaxies. They follow close correlations with global properties of their host galaxies (scaling relations), and are thought to play a crucial role in galaxy evolution. Yet, we lack a complete understanding of fundamental aspects of their growth across cosmic time. In particular, we still do not understand: (1) whether black holes or their host galaxies grow faster and (2) what is the maximum mass that black holes can reach. The high angular resolution capability and sensitivity of 30-m class telescopes will revolutionize our understanding of the extreme end of the black hole and galaxy mass scale. With such facilities, we will be able to dynamically measure masses of the largest black holes and characterize galaxy properties out to redshift $z \sim 1.5$. Together with the evolution of black hole-galaxy scaling relations since $z \sim 1.5$, the maximum mass black hole will shed light on the main channels of black hole growth.

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arXiv2019

Electromagnetic Window into the Dawn of Black Holes

Massive 10^6-10^10 Msun black holes (BHs) are ubiquitous in local galactic nuclei. They were common by the time the Universe is several Gyr old, and many of them were in place within the first 1~Gyr after the Big Bang. Their quick assembly has been attributed to mechanisms such as the rapid collapse of gas into the nuclei of early protogalaxies, accretion and mergers of stellar-mass BHs accompanying structure formation at early times, and the runaway collapse of early, ultra-dense stellar clusters. The origin of the early massive BHs remains an intriguing and long-standing unsolved puzzle in astrophysics. Here we discuss strategies for discerning between BH seeding models using electromagnetic observations. We argue that the most direct answers will be obtained through detection of BHs with masses M<10^5 Msun at redshifts z>10, where we expect them to first form. Reaching out to these redshifts and down to these masses is crucial, because BHs are expected to lose the memory of their initial assembly by the time they grow well above 10^5 Msun and are incorporated into higher-mass galaxies. The best way to detect 10^4-10^5 Msun BHs at high redshifts is by a sensitive X-ray survey. Critical constraining power is augmented by establishing the properties and the environments of their host galaxies in deep optical/IR imaging surveys. Required OIR data can be obtained with the JWST and WFIRST missions. The required X-ray flux limits (down to 10^{-19} erg/s/cm^2) are accessible only with a next-generation X-ray observatory which has both high (sub-1") angular resolution and high throughput. A combination of deep X-ray and OIR surveys will be capable of probing several generic markers of the BH seed scenarios, and resolving the long-stanging puzzle of their origin. These electromagnetic observations are also highly synergistic with the information from LISA on high-z BH mergers.

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