Some of the first stars could be cooler and more massive than standard stellar models would suggest, due to the effects of dark matter annihilation in their cores. It has recently been argued that such objects may attain masses in the 10^4--10^7 solar mass range, and that such supermassive dark stars should be within reach of the upcoming James Webb Space Telescope. Notwithstanding theoretical difficulties with this proposal, we argue here that some of these objects should also be readily detectable with both the Hubble Space Telescope and ground-based 8--10 m class telescopes. Existing survey data already place strong constraints on 10^7 solar mass dark stars at z~10. We show that such objects must be exceedingly rare or short-lived to have avoided detection.
The existence of supermassive black holes at high redshifts ($z\sim7$) is difficult to accommodate in standard astrophysical scenarios. It has been shown that dark matter models with a subdominant self-interacting component are able to produce early seeds for supermassive black holes through the gravothermal catastrophe. Previous studies used a fluid equation approach, requiring some limiting assumptions. Here we reconsider the problem using $N$-body gravitational simulations starting from the formation of the initial dark matter halo. We consider both elastic and dissipative scattering, and e…
In scalar-field dark matter scenarios, a scalar-field soliton could form at the center of galactic halos, around the supermassive black holes that sit at the center of galaxies. Focusing on the large scalar-mass limit, where the soliton is formed by the balance between self-gravity and a repulsive self-interaction, we study the infall of the scalar field onto the central Schwarzschild black hole. We derive the scalar-field profile, from the Schwarzschild radius to the large radii dominated by the scalar cloud. We show that the steady state solution selects the maximum allowed flux, with a crit…
Dark matter mounds from the collapse of supermassive stars: a general-relativistic analysis
Scuola Internazionale Superiore di Studi Avanzati (SISSA)（高等高级研究国际学院）；Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Trieste（意大利国家核物理研究所的里雅斯特分部）；University of Amsterdam（阿姆斯特丹大学）；Institute for Fundamental Physics of the Universe (IFPU)（宇宙基础物理研究所）；Instituto de Fisica de Cantabria (CSIC-UC)（坎塔布里亚物理研究所）；INFN Sezione di Pisa（意大利国家核物理研究所比萨分部）
Supermassive black holes are found at the centre of massive galaxies. During the growth of these black holes they light up to become visible as active galactic nuclei (AGN) and release extraordinary amounts of energy across the electromagnetic spectrum. This energy is widely believed to regulate the rate of star formation in the black holes' host galaxies via so-called "AGN feedback". However, the details of how and when this occurs remains uncertain from both an observational and theoretical perspective. I review some of the observational results and discuss possible observational signatures …
The discovery of quasars at increasingly large cosmological redshifts may favor "direct collapse" as the most promising evolutionary route to the formation of supermassive black holes. In this scenario, supermassive black holes form when their progenitors - supermassive stars - become unstable to gravitational collapse. For uniformly rotating stars supported by pure radiation pressure and spinning at the mass-shedding limit, the critical configuration at the onset of collapse is characterized by universal values of the dimensionless spin and radius parameters $J/M^2$ and $R/M$, independent of …
Constraints on Dark Matter Models from Supermassive Black Hole Evolution
King’s College London（伦敦国王学院）；Theoretical Physics Department, CERN（欧洲核子研究中心理论物理部）；Keemilise ja Bioloogilise Füüsika Instituut（塔尔图大学化学与生物物理研究所）；Department of Cybernetics, Tallinn University of Technology（塔林科技大学网络学系）；Dipartimento di Fisica e Astronomia, Università degli Studi di Padova（帕多瓦大学物理与天文系）；Istituto Nazionale di Fisica Nucleare, Sezione di Padova（意大利国家核物理研究所帕多瓦分部）
The very careful Event Horizon Telescope estimate of the mass of the supermassive black hole at the center of the Giant CD galaxy M87, allied with recent high quality photometric and spectroscopic measurements, yields a proper dark/luminous mass decomposition from the galaxy center to its virial radius. That provides us with decisive information on crucial cosmological and astrophysical issues. The dark and the standard matter distributions in a wide first time detected galaxy region under the supermassive black hole gravitational control. The well known supermassive black hole mass vs stellar…
Measurements of the dynamical environment of supermassive black holes (SMBHs) are becoming abundant and precise. We use such measurements to look for ultralight dark matter (ULDM), which is predicted to form dense cores ("solitons") in the centre of galactic halos. We search for the gravitational imprint of an ULDM soliton on stellar orbits near Sgr A* and by combining stellar velocity measurements with Event Horizon Telescope imaging of M87*. Finding no positive evidence, we set limits on the soliton mass for different values of the ULDM particle mass $m$. The constraints we derive exclude th…
Effects of dark dipole radiation on eccentric supermassive black hole binary inspirals
School of Astronomy and Space Science, University of Chinese Academy of Sciences (UCAS)（中国科学院大学天文与空间科学学院）；School of Physics, Nanjing University（南京大学物理学院）
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, facilita…
Novel method to trace the dark matter density profile around supermassive black holes with AGN reverberation mapping
Virginia Tech（弗吉尼亚理工大学）；Massachusetts Institute of Technology（麻省理工学院）；Harvard University（哈佛大学）；Institute of Science Tokyo（东京科学大学）；The University of Tokyo（东京大学）
We consider scalar dark matter models where the theory has a shift symmetry only broken by the scalar mass term. We restrict ourselves to K-essence kinetic terms where the shift symmetric part of the Lagrangian is a function of the first derivatives of the scalar field only. In the low-amplitude and nonrelativistic regime, which applies on large galactic scales, scalar clouds form solitons with a finite core. Close to the center of galaxies, where a supermassive Black Hole (BH) resides, we analyze the scalar field distribution and the fate of the dark matter soliton when subject to the BH grav…
New observational Constraints on the Growth of the First Supermassive Black Holes
我们限制总吸积质量密度在z>6的超大质量黑洞，推断通过从光度选择的星系候选者的样本的集成X射线发射的上限。研究从最深的哈勃太空望远镜图像中获得的星系，结合钱德拉深场南的钱德拉4兆秒观测，我们获得了早期宇宙中总黑洞生长的最严格限制。我们估计在z~6处的吸积质量密度<1000 Mo Mpc^-3，明显低于先前根据早期黑洞增长的一些现有模型和早期观测所作的预测。这些结果对早期黑洞的增长和通过吸积的质量聚集提出了有趣的限制，并暗示了以下一个或多个问题：（1）在这个时期，只有一小部分明亮的星系含有活跃的黑洞;（2）早期大多数黑洞的增长发生在尘埃和/或质量较小的--尚未被探测到的--宿主星系中;（3）在星系样本中有相当大比例的低z闯入者;（4）早期黑洞的增长是辐射效率低的，严重模糊和/或由于黑洞合并而不是吸积;或（5）大部分黑洞增长发生在晚期。所有这些可能性对我们理解高红移种子形成模型具有重要意义。
We explore the effect of a supermassive black hole (SMBH) on the density profile of a fuzzy dark matter (FDM) soliton core at the centre of a dark matter halo. We numerically solve the Schrödinger-Poisson equations, treating the black hole as a gravitational point mass, and demonstrate that this additional perturbing term has a `squeezing' effect on the soliton density profile, decreasing the core radius and increasing the central density. In the limit of large black hole mass, the solution approaches one akin to the hydrogen atom, with radius inversely proportional to the black hole mass. By …
We simulate recoiling black hole trajectories from $z=20$ to $z=0$ in dark matter halos, quantifying how parameter choices affect escape velocities. These choices include the strength of dynamical friction, the presence of stars and gas, the accelerating expansion of the universe (Hubble acceleration), host halo accretion and motion, and seed black hole mass. $Λ$CDM halo accretion increases escape velocities by up to 0.6 dex and significantly shortens return timescales compared to non-accreting cases. Other parameters change orbit damping rates but have subdominant effects on escape velocities…
Supermassive Black Holes in the Hierarchical Universe: A General Framework and Observational Tests
我们提出了一个简单的框架，超大质量黑洞（SMBHs）的生长和演化的分级结构形成范式。在我们的模型中，黑洞吸积是在宿主暗物质晕之间的主要合并（质量比>~0.3）过程中触发的。类星体光度的连续演化遵循一个普遍的光变曲线形式：初始的指数增长，以恒定的爱丁顿比为单位，直到它达到峰值光度，其次是幂律衰减。假设峰值光度与合并后的晕质量相关，我们将光变曲线与类星体活动的触发率卷积，预测类星体的光度函数（LF）。我们的模型再现了在0.5 <z <4.5处观察到的LF，用于当前光学和X射线调查探测的全部光度范围。我们的模型再现了观测到的红移演化和光度依赖的线性偏置类星体/活动星系核集群。由于瞬时光度和晕质量之间的散射，类星体/活动星系核成团在低到中等光度时对光度的依赖很弱，但在高光度端和高红移时，线性偏差随光度迅速上升。在我们的模型中，爱丁顿比分布大致呈对数正态分布，从高光度类星体（L_bol>~10^46 erg s ^-1）到低光度活动星系核（L_bol <~10^45 erg s ^-1），这种分布会变宽并向较低的平均值移动，与观测结果吻合得很好。
Following up on our earlier work predicting fractionally charged supermassive gravitinos, we explain their potential relevance as novel candidates for Dark Matter and discuss possible signatures and ways to detect them.
