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Direct-collapse black holes (DCBHs) are currently one of the leading contenders for the origins of the first quasars in the universe, over 300 of which have now been found at $z >$ 6. But the birth of a DCBH in an atomically-cooling halo does not by itself guarantee it will become a quasar by $z sim$ 7, the halo must also be located in cold accretion flows or later merge with a series of other gas-rich halos capable of fueling the BHs rapid growth. Here, we present near infrared luminosities for DCBHs born in cold accretion flows in which they are destined to grow to 10$^9$ M$_{odot}$ by $z sim$ 7. Our observables, which are derived from cosmological simulations with radiation hydrodynamics with Enzo, reveal that DCBHs could be found by the James Webb Space Telescope at $z lesssim$ 20 and strongly-lensed DCBHs might be found in future wide-field surveys by Euclid and the Wide-Field Infrared Space Telescope at $z lesssim$ 15.
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We explore the possibility to detect the continuum radio signal from direct collapse black holes (DCBHs) by upcoming radio telescopes such as the SKA and ngVLA, assuming that after formation they can launch and sustain powerful jets at the accretion stage. We assume that the high-$z$ DCBHs have similar jet properties as the observed radio-loud AGNs, then use a jet model to predict their radio flux detectability. If the jet power $P_{rm jet}gtrsim10^{42-43}$ erg s$^{-1}$, it can be detectable by SKA/ngVLA, depending on the jet inclination angle. Considering the relation between jet power and black hole mass and spin, generally, jetted DCBHs with mass $gtrsim10^5~M_odot$ can be detected. For a total jetted DCBH number density of $sim2.5times10^{-3}$ Mpc$^{-3}$ at $z=10$, about 100 deg$^{-2}z^{-1}$ DCBHs are expected to be above the detection threshold of SKA1-mid (100 hours integration). If the jet blob emitting most of the radio signal is dense and highly relativistic, then the DCBH would only feebly emit in the SKA-low band, because of self-synchrotron absorption (SSA) and blueshift. Moreover, the free-free absorption in the DCBH envelope may further reduce the signal in the SKA-low band. Thus, combining SKA-low and SKA-mid observations might provide a potential tool to distinguish a DCBH from a normal star-forming galaxy.
We analyze the early growth stage of direct-collapse black holes (DCBHs) with $sim 10^{5} rm M_odot$, which are formed by collapse of supermassive stars in atomic-cooling halos at $z gtrsim 10$. A nuclear accretion disk around a newborn DCBH is gravitationally unstable and fragments into clumps with a few $10 rm M_odot$ at $sim 0.01-0.1 rm pc$ from the center. Such clumps evolve into massive population III stars with a few $10-100 rm M_odot$ via successive gas accretion and a nuclear star cluster is formed. Radiative and mechanical feedback from an inner slim disk and the star cluster will significantly reduce the gas accretion rate onto the DCBH within $sim 10^6 rm yr$. Some of the nuclear stars can be scattered onto the loss cone orbits also within $lesssim 10^6 rm yr$ and tidally disrupted by the central DCBH. The jet luminosity powered by such tidal disruption events can be $L_{rm j} gtrsim 10^{50} rm erg s^{-1}$. The prompt emission will be observed in X-ray bands with a peak duration of $delta t_{rm obs} sim 10^{5-6} (1+z) rm s$ followed by a tail $propto t_{rm obs}^{-5/3}$, which can be detectable by Swift BAT and eROSITA even from $z sim 20$. Follow-up observations of the radio afterglows with, e.g., eVLA and the host halos with JWST could probe the earliest AGN feedback from DCBHs.
In this white paper we explore the capabilities required to identify and study supermassive black holes formed from heavy seeds ($mathrm{M_{bullet}} sim 10^4 - 10^6 , mathrm{M_{odot}}$) in the early Universe. To obtain an unequivocal detection of heavy seeds we need to probe mass scales of $sim 10^{5-6} , mathrm{M_{odot}}$ at redshift $z gtrsim 10$. From this theoretical perspective, we review the observational requirements and how they compare with planned/proposed instruments, in the infrared, X-ray and gravitational waves realms. In conclusion, detecting heavy black hole seeds at $z gtrsim 10$ in the next decade will be challenging but, according to current theoretical models, feasible with upcoming/proposed facilities. Their detection will be fundamental to understand the early history of the Universe, as well as its evolution until now. Shedding light on the dawn of black holes will certainly be one of the key tasks that the astronomical community will focus on in the next decade.
The leading contenders for the seeds of the first quasars are direct collapse black holes (DCBHs) formed during catastrophic baryon collapse in atomically-cooled halos at $z sim$ 20. The discovery of the Ly$alpha$ emitter CR7 at $z =$ 6.6 was initially held to be the first detection of a DCBH, although this interpretation has since been challenged on the grounds of Spitzer IRAC and Very Large Telescope X-Shooter data. Here we determine if radio flux from a DCBH in CR7 could be detected and discriminated from competing sources of radio emission in the halo such as young supernovae and H II regions. We find that a DCBH would emit a flux of 10 - 200 nJy at 1.0 GHz, far greater than the sub-nJy signal expected for young supernovae but on par with continuum emission from star-forming regions. However, radio emission from a DCBH in CR7 could be distinguished from free-free emission from H II regions by its spectral evolution with frequency and could be detected by the Square Kilometer Array in the coming decade.
Observations of quasars at $ z > 6$ suggest the presence of black holes with a few times $rm 10^9 ~M_{odot}$. Numerous models have been proposed to explain their existence including the direct collapse which provides massive seeds of $rm 10^5~M_{odot}$. The isothermal direct collapse requires a strong Lyman-Werner flux to quench $rm H_2$ formation in massive primordial halos. In this study, we explore the impact of trace amounts of metals and dust enrichment. We perform three dimensional cosmological simulations for two halos of $rm > 10^7~M_{odot}$ with $rm Z/Z_{odot}= 10^{-4}-10^{-6}$ illuminated by an intense Lyman Werner flux of $rm J_{21}=10^5$. Our results show that initially the collapse proceeds isothermally with $rm T sim 8000$ K but dust cooling becomes effective at densities of $rm 10^{8}-10^{12} ~cm^{-3}$ and brings the gas temperature down to a few 100-1000 K for $rm Z/Z_{odot} geq 10^{-6}$. No gravitationally bound clumps are found in $rm Z/Z_{odot} leq 10^{-5}$ cases by the end of our simulations in contrast to the case with $rm Z/Z_{odot} = 10^{-4}$. Large inflow rates of $rm geq 0.1~M_{odot}/yr$ are observed for $rm Z/Z_{odot} leq 10^{-5}$ similar to a zero-metallicity case while for $rm Z/Z_{odot} = 10^{-4}$ the inflow rate starts to decline earlier due to the dust cooling and fragmentation. For given large inflow rates a central star of $rm sim 10^4~M_{odot}$ may form for $rm Z/Z_{odot} leq 10^{-5}$.
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