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Register a new userConnecting Dark Matter Halos with the Galaxy Center and the Supermassive Black Hole
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Observational studies of nearby galaxies have demonstrated correlations between the mass of the central supermassive black holes (BHs) and properties of the host galaxies, notably the stellar bulge mass or central stellar velocity dispersion. Motivated by these correlations, the theoretical paradigm has emerged, in which BHs and bulges co-evolve. However, this picture was challenged by observational and theoretical studies, which hinted that the fundamental connection may be between BHs and dark matter halos, and not necessarily with their host galaxies. Based on a study of 3130 elliptical galaxies $-$ selected from the Sloan Digital and ROSAT All Sky Surveys $-$ we demonstrate that the central stellar velocity dispersion exhibits a significantly tighter correlation with the total gravitating mass, traced by the X-ray luminosity of the hot gas, than with the stellar mass. This hints that the central stellar velocity dispersion, and hence the central gravitational potential, may be the fundamental property of elliptical galaxies that is most tightly connected to the larger-scale dark matter halo. Furthermore, using the central stellar velocity dispersion as a surrogate for the BH mass, we find that in elliptical galaxies the inferred BH mass and inferred total gravitating mass within the virial radius (or within five effective radii) can be expressed as $M_{rm{BH}} propto M_{rm tot}^{1.6^{+0.6}_{-0.4}} $ (or $M_{rm{BH}} propto M_{rm{5r_{eff}}}^{1.8^{+0.7}_{-0.6}}$). These results are consistent with a picture in which the BH mass is directly set by the central stellar velocity dispersion, which, in turn, is determined by the total gravitating mass of the system.
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We study the relations between the mass of the central black hole (BH) $M_{rm BH}$, the dark matter halo mass $M_{rm h}$, and the stellar-to-halo mass fraction $f_starpropto M_star/M_{rm h}$ in a sample of $55$ nearby galaxies with dynamically measured $M_{rm BH}>10^6,{rm M}_odot$ and $M_{rm h}>5times10^{11},{rm M}_odot$. The main improvement with respect to previous studies is that we consider both early- and late-type systems for which $M_{rm h}$ is determined either from globular cluster dynamics or from spatially resolved rotation curves. Independently of their structural properties, galaxies in our sample build a well defined sequence in the $M_{rm BH}$-$M_{rm h}$-$f_star$ space. We find that: (i) $M_{rm h}$ and $M_{rm BH}$ strongly correlate with each other and anti-correlate with $f_star$; (ii) there is a break in the slope of the $M_{rm BH}$-$M_{rm h}$ relation at $M_{rm h}$ of $10^{12},{rm M}_odot$, and in the $f_star$-$M_{rm BH}$ relation at $M_{rm BH}$ of $sim10^7!-!10^8,{rm M}_odot$; (iii) at a fixed $M_{rm BH}$, galaxies with a larger $f_star$ tend to occupy lighter halos and to have later morphological types. We show that the observed trends can be reproduced by a simple equilibrium model in the $Lambda$CDM framework where galaxies smoothly accrete dark and baryonic matter at a cosmological rate, having their stellar and black hole build-up regulated both by the cooling of the available gas reservoir and by the negative feedback from star formation and active galactic nuclei (AGN). Feature (ii) arises as the BH population transits from a rapidly accreting phase to a more gentle and self-regulated growth, while scatter in the AGN feedback efficiency can account for feature (iii).
The formation of ultra rare supermassive black holes (SMBHs), with masses of $mathcal O(10^9,M_odot)$, in the first billion years of the Universe remains an open question in astrophysics. At the same time, ultralight dark matter (DM) with mass in the vicinity of $mathcal O(10^{-20}~text{eV})$ has been motivated by small scale DM distributions. Though this type of DM is constrained by various astrophysical considerations, certain observations could be pointing to modest evidence for it. We present a model with a confining first order phase transition at $sim 10$ keV temperatures, facilitating production of $mathcal O(10^9,M_odot)$ primordial SMBHs. Such a phase transition can also naturally lead to the implied mass for a motivated ultralight axion DM candidate, suggesting that SMBHs and ultralight DM may be two sides of the same cosmic coin. We consider constraints and avenues to discovery from superradiance and a modification to $N_{rm eff}$. On general grounds, we also expect primordial gravitational waves -- from the assumed first order phase transition -- characterized by frequencies of $mathcal O(10^{-12}-10^{-9}~text{Hz})$. This frequency regime is largely uncharted, but could be accessible to pulsar timing arrays if the primordial gravitational waves are at the higher end of this frequency range, as could be the case in our assumed confining phase transition.
We propose the formation of massive pristine dark-matter (DM) halos with masses of $sim 10^8~M_odot$, due to the dynamical effects of frequent mergers in rare regions of the Universe with high baryonic streaming velocity relative to DM. Since the streaming motion prevents gas collapse into DM halos and delays prior star formation episodes, the gas remains metal-free until the halo virial temperatures $gtrsim 2times 10^4~{rm K}$. The minimum cooling mass of DM halos is boosted by a factor of $sim 10-30$ because frequent major mergers of halos further inhibit gas collapse. We use Monte Carlo merger trees to simulate the DM assembly history under a streaming velocity of twice the root-mean-square value, and estimate the number density of massive DM halos containing pristine gas as $simeq 10^{-4}~{rm cMpc}^{-3}$. When the gas infall begins, efficient Ly$alpha$ cooling drives cold streams penetrating inside the halo and feeding a central galactic disk. When one stream collides with the disk, strong shock forms a dense and hot gas cloud, where the gas never forms H$_2$ molecules due to effective collisional dissociation. As a result, a massive gas cloud forms by gravitational instability and collapses directly into a massive black hole (BH) with $M_bullet sim 10^5~M_odot$. Almost simultaneously, a galaxy with $M_{star, rm tot}sim 10^6~M_odot$ composed of Population III stars forms in the nuclear region. If the typical stellar mass is as high as $sim 100~M_odot$, the galaxy could be detected with the James Webb Space Telescope even at $zgtrsim 15$. These massive seed BHs would be fed by continuous gas accretion from the host galaxy, and grow to be bright quasars observed at $zgtrsim 6$.
We present Trinity, a flexible empirical model that self-consistently infers the statistical connection between dark matter haloes, galaxies, and supermassive black holes (SMBHs). Trinity is constrained by galaxy observables from $0 < z < 10$ (galaxies stellar mass functions, specific and cosmic SFRs, quenched fractions, and UV luminosity functions) and SMBH observables from $0 < z < 6.5$ (quasar luminosity functions, quasar probability distribution functions, active black hole mass functions, local SMBH mass-bulge mass relations, and the observed SMBH mass distributions of high redshift bright quasars). The model includes full treatment of observational systematics (e.g., AGN obscuration and errors in stellar masses). From these data, Trinity infers the average SMBH mass, SMBH accretion rate, merger rate, and Eddington ratio distribution as functions of halo mass, galaxy stellar mass, and redshift. Key findings include: 1) the normalization of the SMBH mass-bulge mass relation increases only mildly from $z=0$ to $z=3$, but decreases more strongly from $z=3$ to $z=10$; 2) The AGN radiative$+$kinetic efficiency is $sim$0.04-0.07, and does not show significant redshift dependence given the existing data constraints; 3) AGNs show downsizing, i.e., the Eddington ratios of more massive SMBHs start to decrease earlier than those of lower-mass objects; 4) The average ratio between average SMBH accretion rate and SFR is $sim10^{-3}$ for low-mass galaxies, which are primarily star-forming. This ratio increases to $sim10^{-1}$ for the most massive haloes below $zsim1$, where star formation is quenched but SMBHs continue to accrete.
We present 1-resolution ALMA observations of the circumnuclear disk (CND) and the environment around SgrA*. The images unveil the presence of small spatial scale CO (J=3-2) molecular cloudlets within the central pc of the Milky Way, moving at high speeds, up to 300 km/s along the line-of-sight. The CO-emitting structures show intricate morphologies: extended and filamentary at high negative-velocities (v_LSR < -150 km/s), more localized and clumpy at extreme positive-velocities (v_LSR > +200 km/s). Based on the pencil-beam CO absorption spectrum toward SgrA* synchrotron emission, we also present evidence for a diffuse gas component producing absorption features at more extreme negative-velocities (v_LSR < -200 km/s). The CND shows a clumpy spatial distribution. Its motion requires a bundle of non-uniformly rotating streams of slightly different inclinations. The inferred gas density peaks are lower than the local Roche limit. This supports that CND molecular cores are transient. We apply the two standard orbit models, spirals vs. ellipses, invoked to explain the kinematics of the ionized gas streamers around SgrA*. The location and velocities of the CO cloudlets are inconsistent with the spiral model, and only two of them are consistent with the Keplerian ellipse model. Most cloudlets, however, show similar velocities that are incompatible with the motions of the ionized streamers or with gas bounded to the central gravity. We speculate that they are leftovers of more massive, tidally disrupted, clouds that fall into the cavity, or that they originate from instabilities in the inner rim of the CND and infall from there. Molecular cloudlets, all together with a mass of several 10 M_Sun, exist around SgrA*. Most of them must be short-lived: photoevaporated by the intense stellar radiation field, blown away by winds from massive stars, or disrupted by strong gravitational shears.
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