Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userRadio signals from early direct collapse black holes
182
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
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.
rate research
Read More
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.
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.
Binary black holes as the recently detected sources of gravitational waves can be formed from massive stellar binaries in the field or by dynamical interactions in clusters of high stellar density, if the black holes are the remnants of massive stars that collapsed without natal kicks that would disrupt the binary system or eject the black holes from the cluster before binary black hole formation. Here are summarized and discussed the kinematics in three dimensions of space of five Galactic black hole X-ray binaries. For Cygnus X-1 and GRS 1915+105 it is found that the black holes of ~15 and ~10 solar masses in these sources were formed in situ, without energetic kicks. These observations suggest that binary black holes with components of ~10 solar masses may have been prolifically produced in the universe.
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.
We consider radio emission from a newborn black hole (BH), which is accompanied by a mini-disk with a mass of $lesssim M_odot$. Such a disk can be formed from an outer edge of the progenitors envelope, especially for metal-poor massive stars and/or massive stars in close binaries. The disk accretion rate is typically super-Eddington and an ultrafast outflow with a velocity of $sim 0.1mbox{-}0.3,c$ will be launched into the circumstellar medium. The outflow forms a collisionless shock, and electrons are accelerated and emit synchrotron emission in radio bands with a flux of $sim 10^{26-30} rm erg s^{-1} Hz^{-1}$ days to decades after the BH formation. The model predicts not only a fast UV/optical transient but also quasi-simultaneous inverse-Compton X-ray emission $sim$ a few days after the BH formation, and the discovery of the radio counterpart with coordinated searches will enable us to identify this type of transients. The occurrence rate can be $0.1-10 %$ of the core-collapse supernova rate, which makes them a promising target of dedicated radio observations such as the Jansky VLA Sky Survey.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
