ALBERT

Description: We analyse the environment of the supermassive black hole (SMBH) in the centre of a massive elliptical galaxy NGC 1275 in the Perseus cluster, hosting the radio source 3C 84. We focus on the young radio lobe observed inside the estimated Bondi accretion radius, and discusss the momentum balance between the jet associated with the lobe and the surrounding gas. The results are compared with the proper motion of the radio lobe obtained with the very long baseline interferometry. We find that under assumption of a high-density environment ( 100 cm – 3 ), the jet power must be comparable to the Eddington luminosity – this is clearly inconsistent with the current moderate activity of 3C 84, which indicates instead that the jet is expanding in a very low-density region ( 1 cm – 3 ), along the rotation axis of the accretion flow. The power required for the jet to expand in the low-density environment is comparable to the past average jet power estimated from the X-ray observations. We estimate the classical Bondi accretion rate, assuming that (1) gas accretion is spherically symmetric, (2) accretion is associated with the jet environment, and (3) the medium surrounding the jet is representative of the properties of the dominant accreting gas. We find that Bondi accretion is inconsistent with the estimated jet power. This means that either accretion of the cold gas in the NGC 1275 is more efficient than that of the hot gas, or the jets are powered by the SMBH spin.

Description: We use high-resolution zoom-in cosmological simulations of galaxies of Romano-Díaz et al., post-processing them with a panchromatic three-dimensional radiation transfer code to obtain the galaxy UV luminosity function (LF) at z ~= 6–12. The galaxies are followed in a rare, heavily overdense region within a ~5 density peak, which can host high- z quasars, and in an average density region, down to the stellar mass of M star  ~ 4 10 7 M . We find that the overdense regions evolve at a substantially accelerated pace – the most massive galaxy has grown to M star  ~ 8.4 10 10 M by z  = 6.3, contains dust of M dust  ~ 4.1 10 8 M , and is associated with a very high star formation rate, SFR ~ 745 M yr – 1 . The attained SFR– M star correlation results in the specific SFR slowly increasing with M star . Most of the UV radiation in massive galaxies is absorbed by the dust, its escape fraction f esc is low, increasing slowly with time. Galaxies in the average region have less dust, and agree with the observed UV LF. The LF of the overdense region is substantially higher, and contains much brighter galaxies. The massive galaxies are bright in the infrared (IR) due to the dust thermal emission, with L IR  ~ 3.7 10 12 L at z  = 6.3, while L IR  〈 10 11 L for the low-mass galaxies. Therefore, ALMA can probe massive galaxies in the overdense region up to z  ~ 10 with a reasonable integration time. The UV spectral properties of discy galaxies depend significantly upon the viewing angle. The stellar and dust masses of the most massive galaxy in the overdense region are comparable to those of the sub-millimetre galaxy found by Riechers et al. at z  = 6.3, while the modelled SFR and the sub-millimetre flux fall slightly below the observed one. Statistical significance of these similarities and differences will only become clear with the upcoming ALMA observations.

Description: We provide detailed comparison between the adaptive mesh refinement (AMR) code enzo -2.4 and the smoothed particle hydrodynamics (SPH)/ N -body code gadget -3 in the context of isolated or cosmological direct baryonic collapse within dark matter (DM) haloes to form supermassive black holes. Gas flow is examined by following evolution of basic parameters of accretion flows. Both codes show an overall agreement in the general features of the collapse; however, many subtle differences exist. For isolated models, the codes increase their spatial and mass resolutions at different pace, which leads to substantially earlier collapse in SPH than in AMR cases due to higher gravitational resolution in gadget -3. In cosmological runs, the AMR develops a slightly higher baryonic resolution than SPH during halo growth via cold accretion permeated by mergers. Still, both codes agree in the build-up of DM and baryonic structures. However, with the onset of collapse, this difference in mass and spatial resolution is amplified, so evolution of SPH models begins to lag behind. Such a delay can have effect on formation/destruction rate of H 2 due to UV background, and on basic properties of host haloes. Finally, isolated non-cosmological models in spinning haloes, with spin parameter ~ 0.01–0.07, show delayed collapse for greater , but pace of this increase is faster for AMR. Within our simulation set-up, gadget -3 requires significantly larger computational resources than enzo -2.4 during collapse, and needs similar resources, during the pre-collapse, cosmological structure formation phase. Yet it benefits from substantially higher gravitational force and hydrodynamic resolutions, except at the end of collapse.

Description: We study the early stage of the formation of seed supermassive black holes via direct collapse in dark matter (DM) haloes, in the cosmological context. We perform high-resolution zoom-in simulations of such collapse at high z . Using the adaptive mesh refinement code enzo , we resolve the formation and growth of a DM halo, until its virial temperature reaches ~10 4  K, atomic cooling turns on, and collapse ensues. We demonstrate that direct collapse proceeds in two stages, although they are not well separated. The first stage is triggered by the onset of atomic cooling, and leads to rapidly increasing accretion rate with radius, from $\dot{M}\sim 0.1\,\mathrm{M}_{\odot }\,{\rm yr^{-1}}$ at the halo virial radius to few M yr –1 , around the scale radius R s ~ 30 pc of the NFW DM density profile. The second stage of the collapse commences when the gas density takes precedence over the DM density. This is associated with the gas decoupling from the DM gravitational potential. The ensuing collapse approximates that of an isothermal sphere with $\dot{M}{(r)}\sim$  const. We confirm that the gas loses its angular momentum through non-axisymmetric perturbations and gravitational torques, to overcome the centrifugal barrier. During the course of the collapse, this angular momentum transfer process happens on nearly all spatial scales, and the angular momentum vector of the gas varies with position and time. Collapsing gas also exhibits supersonic turbulent motions which suppress gas fragmentation, and are characterized by density PDF consisting of a lognormal part and a high-density power-law tail.

Description: We use cosmological adaptive mesh refinement code enzo zoom-in simulations to study the long-term evolution of the collapsing gas within dark matter haloes at z . This direct collapse process is a leading candidate for rapid formation of supermassive black hole (SMBH) seeds. To circumvent the Courant condition at small radii, we apply the sink particle method, focusing on evolution on scales ~0.01–10 pc. The collapse proceeds in two stages, with the secondary runaway happening within the central 10 pc. The sink particles form when the collapsing gas requires additional refinement of the grid size at the highest refinement level. Their growth is negligible with the sole exception of the central seed which grows dramatically to M seed  ~ 2  x  10 6 M in ~2 Myr, confirming the feasibility of this path to the SMBH. The variability of angular momentum in the accreted gas results in the formation of two misaligned discs. Both discs lie within the Roche limit of the central seed. While the inner disc is geometrically thin and weakly asymmetric, the outer disc flares due to turbulent motions as a result of the massive inflow along a pair of penetrating filaments. The filamentary inflow determines the dominant Fourier modes in this disc – these modes have a non-self-gravitational origin. We do not confirm that m  = 1 is a dominant mode that drives the inflow in the presence of a central massive object. The overall configuration appears to be generic, and is expected to form when the central seed becomes sufficiently massive.

Description: We use high-resolution zoom-in cosmological simulations of galaxies of Romano-Díaz et al., post-processing them with a panchromatic three-dimensional radiation transfer code to obtain the galaxy UV luminosity function (LF) at z ~= 6–12. The galaxies are followed in a rare, heavily overdense region within a ~5 density peak, which can host high- z quasars, and in an average density region, down to the stellar mass of M star  ~ 4 10 7 M . We find that the overdense regions evolve at a substantially accelerated pace – the most massive galaxy has grown to M star  ~ 8.4 10 10 M by z  = 6.3, contains dust of M dust  ~ 4.1 10 8 M , and is associated with a very high star formation rate, SFR ~ 745 M yr – 1 . The attained SFR– M star correlation results in the specific SFR slowly increasing with M star . Most of the UV radiation in massive galaxies is absorbed by the dust, its escape fraction f esc is low, increasing slowly with time. Galaxies in the average region have less dust, and agree with the observed UV LF. The LF of the overdense region is substantially higher, and contains much brighter galaxies. The massive galaxies are bright in the infrared (IR) due to the dust thermal emission, with L IR  ~ 3.7 10 12 L at z  = 6.3, while L IR  〈 10 11 L for the low-mass galaxies. Therefore, ALMA can probe massive galaxies in the overdense region up to z  ~ 10 with a reasonable integration time. The UV spectral properties of discy galaxies depend significantly upon the viewing angle. The stellar and dust masses of the most massive galaxy in the overdense region are comparable to those of the sub-millimetre galaxy found by Riechers et al. at z  = 6.3, while the modelled SFR and the sub-millimetre flux fall slightly below the observed one. Statistical significance of these similarities and differences will only become clear with the upcoming ALMA observations.