Ivana Ebrova, Bruno Jungwiert, Gabriela Canalizo, Nicola Bennert, Lucie Jilkova
Using N-body simulations of shell galaxies created in nearly radial minor mergers, we investigate the error of collision dating, resulting from the neglect of dynamical friction and of gradual disruption of the cannibalized dwarf.
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With the goal to refine modelling of shell galaxies and the use of shells to probe the merger history, we develop a new method for implementing dynamical friction in test-particle simulations of radial minor mergers. The friction is combined with a gradual decay of the dwarf galaxy. The coupling of both effects can considerably redistribute positions and luminosities of shells; neglecting them can lead to significant errors in attempts to date the merger.
Dynamical expansion of H II regions around star clusters plays a key role in dispersing the surrounding dense gas and therefore in limiting the efficiency of star formation in molecular clouds. We use a semi-analytic method and numerical simulations to explore expansion of spherical dusty H II regions and surrounding neutral shells and the resulting cloud disruption. Our model for shell expansion adopts the static solutions of Draine (2011) for dusty H II regions and considers the contact outward forces on the shell due to radiation and thermal pressures as well as the inward gravity from the …
Stellar shells observed in many giant elliptical and lenticular as well as a few spiral and dwarf galaxies presumably result from radial minor mergers of galaxies. We show that the line-of-sight velocity distribution of the shells has a quadruple-peaked shape. We found simple analytical expressions that connect the positions of the four peaks of the line profile with the mass distribution of the galaxy, namely, the circular velocity at the given shell radius and the propagation velocity of the shell. The analytical expressions were applied to a test-particle simulation of a radial minor merger…
Coalescence of intermediate-mass black holes (IMBHs) as a result of the migration toward galactic centers via dynamical friction may contribute to the formation of supermassive BHs. Here we reinvestigate the gaseous dynamical friction, which was claimed to be inefficient with radiative feedback from BHs in literature, by performing 3D radiation-hydrodynamics simulations that solve the flow structure in the vicinity of BHs. We consider a $10^4~M_\odot$ BH moving at the velocity $V_{\rm flow}$ through the homogeneous medium with metallicity $Z$ in the range of $0-0.1~Z_\odot$ and density $n_{\in…
Living the stream: Properties and progenitors of tidal shells and streams around galaxies from Magneticum
本文利用 Magneticum Pathfinder 宇宙学流体模拟研究星系周围潮汐壳层与星流的运动学和恒星族群性质，重建其前身星系，并识别出由原位恒星形成形成的星流。
We present the adaptable MUESLI code for investigating dynamics and erosion processes of globular clusters (GCs) in galaxies. MUESLI follows the orbits of individual clusters and applies internal and external dissolution processes to them. Orbit integration is based on the self-consistent field method in combination with a time-transformed leapfrog scheme, allowing us to handle velocity-dependent forces like triaxial dynamical friction. In a first application, the erosion of globular cluster systems (GCSs) in elliptical galaxies is investigated. Observations show that massive ellipticals have …
A starburst induced by a galaxy merger may create a relatively thin central stellar disk at radius $\le 100$pc. We calculate the rate of tidal disruption events (TDEs) by the inspiraling secondary supermassive black (SMBH) through the disk. With a small enough stellar velocity dispersion ($σ/v_c \le 0.1$) in the disk, it is shown that $10^5-10^6$ TDEs of solar-type main sequence stars per post-starburst galaxy (PSB) can be produced to explain their dominance in producing observed TDEs. Although the time it takes to bring the secondary SMBH to the disk apparently varies in the range of $\sim 0.…
In hierarchical structure formation, dark matter halos that merge with larger halos can persist as subhalos. These subhalos are likely hosts of visible galaxies. While the dense halo environment rapidly strips subhalos of their dark mass, the compact luminous material can remain intact for some time, making the correspondence of galaxies with severely stripped subhalos unclear. Many galaxy evolution models assume that satellite galaxies eventually merge with their central galaxy, but this ignores the possibility of satellite tidal disruption. We use a high-resolution $N$-body simulation of cos…
Shell galaxies are understood to form through the collision of a dwarf galaxy with an elliptical galaxy. Shell structures and kinematics have been noted to be independent tools to measure the gravitational potential of the shell galaxies. We compare theoretically the formation of shells in Type I shell galaxies in different gravity theories in this work because this is so far missing in the literature. We include Newtonian plus dark halo gravity, and two non-Newtonian gravity models, MOG and MOND, in identical initial systems. We investigate the effect of dynamical friction, which by slowing d…
Tidal Disruption of Stars by Supermassive Black Holes and Naked Singularities with Scalar Hair
本文研究星系中心暗物质（标量场）对黑洞和裸奇点潮汐力的影响，发现标量场黑洞轨道半径可极小且潮汐力巨大，并解释裸奇点附近恒星碰撞壳层可产生潮汐瓦解事件。
Energy evolution in the progenitor of galaxy shells: a semi-analytical model
本文提出一个半解析模型，研究矮星系前身在并合瓦解过程中粒子能量和角动量的变化，揭示自引力对壳层形成的关键作用，并证明精确建模前身能量范围对预测可观测壳层数量至关重要。
The model of a radial minor merger proposed by Quinn (1984), which successfully reproduces the observed regular shell systems in shell galaxies, is ideal for a test-particle simulation. We compare such a simulation with a self-consistent one. They agree very well in positions of the first generation of shells but potentially important effects -- dynamical friction and gradual decay of the dwarf galaxy -- are not present in the test-particle model, therefore we look for a proper way to include them.
The accretion of massive star clusters via dynamical friction has previously been established to be a likely scenario for the build up of nuclear stellar clusters (NSCs). A remaining issue is whether strong external tidal perturbation may lead to the severe disruption of loosely-bound clusters well before they sink deeply into the center of their host galaxies. We carry out a series of $N$-body simulations and verify our early idealized analytic models. We show if the density profile of the host galaxies can be described by a power-law distribution with an index, $α<1$, the cluster would be co…
Insights into Jet-Induced Cloud Disruption in NGC 1316: ALMA Reveals a Spatially Extended Molecular Gas
利用 ALMA 100 pc 分辨率观测，发现射电星系 NGC 1316 中分子气体存在大量空间延展成分，喷流与分子云相互作用导致云团破坏，表现为宽 CO 谱线、高速度弥散和增高的线比，支持喷流驱动的膨胀气泡模型。
We present new deep observations of 'shell' structures in the halo of the nearby elliptical galaxy NGC 7600, alongside a movie of galaxy formation in a cold dark matter universe (available at http://www.virgo.dur.ac.uk/shell-galaxies). The movie, based on an ab initio cosmological simulation, shows how continuous accretion of clumps of dark matter and stars creates a swath of diffuse circumgalactic structures. The disruption of a massive clump on a near-radial orbit creates a complex system of transient concentric shells which bare a striking resemblance to those of NGC 7600. With the aid of t…
It is typically assumed that radiation pressure driven winds are accelerated to an asymptotic velocity of V ~ v_esc, where v_esc is the escape velocity from the central source. We note that this is not the case for dusty shells and clouds. Instead, if the shell or cloud is initially optically-thick to the UV emission from the source of luminosity L, then there is a significant boost in V that reflects the integral of the momentum absorbed as it is accelerated. For shells reaching a generalized Eddington limit, we show that V ~ (4R_UV L/M_sh c)^1/2, in both point-mass and isothermal-sphere pote…
We present a model for the dynamical evolution of subhaloes based on an approach combining numerical and analytical methods. Our method is based on tracking subhaloes in an N-body simulation up to the last point that it can be resolved, and applying an analytic prescription for its merger timescale that takes dynamical friction and tidal disruption into account. When applied to cosmological N-body simulations with mass resolutions that differ by two orders of magnitude, the technique produces halo occupation distributions that agree to within 3%.
Mass Determination of Supermassive Black Holes Governing Evolution of Radio Emitters
本研究构建了盘风驱动射电辐射壳层的动力学框架，推导其膨胀标度规律，提出可通过射电观测估算超大质量黑洞质量，为潮汐瓦解事件研究及黑洞质量测量提供新方法。
Shell-type Tidal Features Are More Frequently Detected in Slowly Rotating Early-type Galaxies than Stream- and Tail-type Features
本研究基于DESI Legacy Survey深场图像和MaNGA运动学数据，分类1244个低红移早型星系的潮汐特征，发现壳层型特征与更低的$λ_{R_e}$及慢旋转体显著相关，支持径向并合形成壳层。
We use N-body simulations to study the tidal evolution of globular clusters (GCs) in dwarf spheroidal (dSph) galaxies. Our models adopt a cosmologically motivated scenario in which the dSph is approximated by a static NFW halo with a triaxial shape. We apply our models to five GCs spanning three orders of magnitude in stellar density and two in mass, chosen to represent the properties exhibited by the five GCs of the Fornax dSph. We show that only the object representing Fornax's least dense GC (F1) can be fully disrupted by Fornax's internal tidal field--the four denser clusters survive even …
Shells are low surface brightness tidal debris that appear as interleaved caustics with large opening angles, often situated on both sides of the galaxy center. In this paper, we study the incidence and formation processes of shell galaxies in the cosmological gravity+hydrodynamics Illustris simulation. We identify shells at redshift z=0 using stellar surface density maps, and we use stellar history catalogs to trace the birth, trajectory and progenitors of each individual star particle contributing to the tidal feature. Out of a sample of the 220 most massive galaxies in Illustris ($\mathrm{M…
A Massive Black Hole 0.8 kpc from the Host Nucleus Revealed by the Offset Tidal Disruption Event AT2024tvd
本文报告了首个通过光学巡天发现的核外潮汐瓦解事件 AT2024tvd，揭示了距宿主星系核 0.8 kpc 处存在一个质量比中心黑洞低至少10倍的大质量黑洞，支持了宇宙学模拟中偏心黑洞数量与宿主晕质量线性相关的预期。
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