Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe origin of most massive black holes at high-z: BLUETIDES and the next quasar frontier
55
0
0.0
(
0
)
Authors
Tiziana Di Matteo
Ask ChatGPT about the research
No Arabic abstract
The growth of the most massive black holes in the early universe, consistent with the detection of highly luminous quasars at $z> 6$ implies sustained, critical accretion of material to grow and power them. Given a black hole seed scenario, it is still uncertain which conditions in the early Universe allow the fastest black hole growth. Large scale hydrodynamical cosmological simulations of structure formation allow us to explore the conditions conducive to the growth of the earliest supermassive black holes. We use the cosmological hydrodynamic simulation BlueTides, which incorporates a variety of baryon physics in a (400 Mpc/h)^3 volume with 0.7 trillion particles to follow the earliest phases of black hole critical growth. At z=8 the most massive black holes (a handful) approach masses of 10^8 Msun with the most massive (with M_BH = 4 x 10^8 Msun ) being found in an extremely compact spheroid-dominated host galaxy. Examining the large-scale environment of hosts, we find that the initial tidal field is more important than overdensity in setting the conditions for early BH growth. In regions of low tidal fields gas accretes cold onto the black hole and falls along thin, radial filaments straight into the center forming the most compact galaxies and most massive black holes at earliest times. Regions of high tidal fields instead induce larger coherent angular momenta and influence the formation of the first population of massive compact disks. The extreme early growth depends on the early interplay of high gas densities and the tidal field that shapes the mode of accretion. Mergers play a minor role in the formation of the first generation, rare massive BHs.
rate research
Read More
The most distant known quasar recently discovered by Ba~nados et al. (2018) is at $z=7.5$ (690 Myr after the Big Bang), at the dawn of galaxy formation. We explore the host galaxy of the brightest quasar in the large volume cosmological hydrodynamic simulation BlueTides, which in Phase II has reached these redshifts. The brightest quasar in BlueTides has a luminosity of a $sim$ few $10^{13} L_{odot}$ and a black hole mass of $6.4 times 10^{8} M_{odot}$ at $z sim 7.5$, comparable to the observed quasar (the only one in this large volume). The quasar resides in a rare halo of mass $M_{H} sim 10^{12} M_{odot}$ and has a host galaxy of stellar mass of $4 times 10^{10}M_{odot}$ with an ongoing (intrinsic) star formation rate of $sim 80 M_{odot} yr^{-1}$. The corresponding intrinsic UV magnitude of the galaxy is $-23.1$, which is roughly $2.7$ magnitudes fainter than the quasars magnitude of $-25.9$. We find that the galaxy is highly metal enriched with a mean metallicity equal to the solar value. We derive quasar and galaxy spectral energy distribution (SED) in the mid and near infrared JWST bands. We predict a significant amount of dust attenuation in the rest-frame UV corresponding to $A_{1500} sim 1.7$ giving an UV based SFR of $sim 14 M_{odot} yr^{-1}$. We present mock JWST images of the galaxy with and without central point source, in different MIRI and NIRCam filters. The host galaxy is detectable in NIRCam filters, but it is extremely compact ($R_{E}=0.35$ kpc). It will require JWSTs exquisite sensitivity and resolution to separate the galaxy from the central point source. Finally within the FOV of the quasar in BlueTides there are two more sources that would be detectable by JWST.
We exploit the recent, wide samples of far-infrared (FIR) selected galaxies followed-up in X rays and of X-ray/optically selected active galactic nuclei (AGNs) followed-up in the FIR band, along with the classic data on AGN and stellar luminosity functions at high redshift z>1.5, to probe different stages in the coevolution of supermassive black holes (BHs) and host galaxies. The results of our analysis indicate the following scenario: (i) the star formation in the host galaxy proceeds within a heavily dust-enshrouded medium at an almost constant rate over a timescale ~0.5-1 Gyr, and then abruptly declines due to quasar feedback; over the same timescale, (ii) part of the interstellar medium loses angular momentum, reaches the circum-nuclear regions at a rate proportional to the star formation and is temporarily stored into a massive reservoir/proto-torus wherefrom it can be promptly accreted; (iii) the BH grows by accretion in a self-regulated regime with radiative power that can slightly exceed the Eddington limit L/L_Edd< 4, particularly at the highest redshifts; (iv) for massive BHs the ensuing energy feedback at its maximum exceeds the stellar one and removes the interstellar gas, thus stopping the star formation and the fueling of the reservoir; (v) afterwards, if the latter has retained enough gas, a phase of supply-limited accretion follows exponentially declining with a timescale of about 2 e-folding times. We show that the ratio of the FIR luminosity of the host galaxy to the bolometric luminosity of the AGN maps the various stages of the above sequence. Finally, we discuss how the detailed properties and the specific evolution of the reservoir can be investigated via coordinated, high-resolution observations of starforming, strongly-lensed galaxies in the (sub-)mm band with ALMA and in the X-ray band with Chandra and the next generation X-ray instruments.
Under the assumption that jets in active galactic nuclei are powered by accretion and the spin of the central supermassive black hole, we are able to reproduce the radio luminosity functions of high- and low-excitation galaxies. High-excitation galaxies are explained as high-accretion rate but very low spin objects, while low-excitation galaxies have low accretion rates and bimodal spin distributions, with approximately half of the population having maximal spins. At higher redshifts (z~1), the prevalence of high accretion rate objects means the typical spin was lower, while in the present day Universe is dominated by low accretion rate objects, with bimodal spin distributions.
The presence of massive black holes (BHs) with masses of order $10^9rm, M_odot$, powering bright quasars when the Universe was less than 1 Gyr old, poses strong constraints on their formation mechanism. Several scenarios have been proposed to date to explain massive BH formation, from the low-mass seed BH remnants of the first generation of stars to the massive seed BHs resulting from the rapid collapse of massive gas clouds. However, the plausibility of some of these scenarios to occur within the progenitors of high-z quasars has not yet been thoroughly explored. In this work, we investigate, by combining dark-matter only N-body simulations with a semi-analytic framework, whether the conditions for the formation of massive seed BHs from synchronised atomic-cooling halo pairs and/or dynamically-heated mini-haloes are fulfilled in the overdense regions where the progenitors of a typical high-redshift quasar host form and evolve. Our analysis shows that the peculiar conditions in such regions, i.e. strong halo clustering and high star formation rates, are crucial to produce a non-negligible number of massive seed BH host candidates: we find $approx1400$ dynamically heated metal-free mini-haloes, including one of these which evolves to a synchronised pair and ends up in the massive quasar-host halo by $z=6$. This demonstrates that the progenitors of high-redshift quasar host haloes can harbour early massive seed BHs. Our results further suggest that multiple massive seed BHs may form in or near the quasar hosts progenitors, potentially merging at lower redshifts and yielding gravitational wave events.
Massive black holes (MBHs) are nowadays recognized as integral parts of galaxy evolution. Both the approximate proportionality between MBH and galaxy mass, and the expected importance of feedback from active MBHs in regulating star formation in their host galaxies point to a strong interplay between MBHs and galaxies. MBHs must form in the first galaxies and be fed by gas in these galaxies, with continuous or intermittent inflows that, at times, can be larger than the Eddington rate. Feedback from supernovae and from the MBHs themselves modulates the growth of the first MBHs. While current observational data only probe the most massive and luminous MBHs, the tip of the iceberg, we will soon be able to test theoretical models of MBH evolution on more normal MBHs: the MBHs that are indeed relevant in building the population that we observe in local galaxies, including our own Milky Way.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
