We study the stellar morphological evolution of disc galaxies within clusters in the TNG50 and TNG100 runs from the IllustrisTNG simulation suite. We select satellites of masses $10^{9.7} \leq M_{*,z=0}/\text{M}_{\odot} \leq 10^{11.6}$ residing in clusters of masses $10^{14} \lesssim M_{\text{200c,z=0}}/\text{M}_{\odot} \leq 10^{14.6}$ at $z=0$ and that were discs at accretion according to a kinematic morphology indicator (the circularity fraction). These are traced from the time of accretion to $z=0$ and compared to a control sample of central galaxies mass-matched at accretion. Most cluster discs become non-discy by $z=0$, in stark contrast with the control discs, of which a significant fraction remains discy over the same timescales. Cluster discs become non-discy accompanied by gas removal and star formation quenching, loss of dark matter and little growth or a loss of stellar mass. In contrast, control discs transform while also losing gas mass and quenching, but growing significantly in dark matter and stellar mass. Most cluster satellites change morphologies on similar timescales regardless of stellar mass, in $\sim0.5-4$ Gyr after accretion. Cluster discs that experienced more numerous and closer pericentric passages show the largest change in morphology. Morphological change in all cases requires the presence of a gravitational perturbation to drive stellar orbits to non-discy configurations, along with gas removal/heating to prevent replenishment of the disc through continued star-formation. For cluster discs, the perturbation is impulsive tidal shocking at pericentres and not tidal stripping of outer disc stellar material, whereas for control discs, a combination of mergers and AGN feedback appears to be the key driving force behind morphological transformations.
Low metallicity stars give rise to unique spectacular transients and are of immense interest for understanding stellar evolution. Their importance has only grown further with the recent detections of mergers of stellar mass black holes that likely originate mainly from low metallicity progenitor systems. Moreover, the formation of low metallicity stars is intricately linked to galaxy evolution, in particular to early enrichment and to later accretion and mixing of lower metallicity gas. Because low metallicity stars are difficult to observe directly, cosmological simulations are crucial for un…
We investigate the formation history of massive disk galaxies in hydro-dynamical simulation--the IllustrisTNG, to study why massive disk galaxies survive through cosmic time. 83 galaxies in the simulation are selected with M$_{*,z=0}$ $>8\times10^{10}$ M$_\odot$ and kinematic bulge-to-total ratio less than $0.3$. We find that 8.4 percent of these massive disk galaxies have quiet merger histories and preserve disk morphology since formed. 54.2 percent have a significant increase in bulge components in history, then become disks again till present time. The rest 37.3 percent experience prominent…
A key feature of a large population of low-mass, late-type disk galaxies are star-forming disks with exponential light distributions. They are typically also associated with thin and flat morphologies, blue colors, and dynamically cold stars moving along circular orbits within co-planar thin gas disks. However, the latter features do not necessarily always imply the former, in fact, a variety of different kinematic configurations do exist. In this work, we use the cosmological hydrodynamical IllustrisTNG Simulation to study the nature and origin of dynamically hot, sometimes even counter-rotat…
A rare population of massive disk galaxies have been found to invade the red sequence dominated by early-type galaxies. These red/quenched massive disk galaxies have recently gained great interest into their formation and origins. The usually proposed quenching mechanisms, such as bar quenching and environment quenching, seem not suitable for those bulge-less quenched disks in low-density environment. In this paper, we use the IllustrisTNG-300 simulation to investigate the formation of massive quenched central disk galaxies. It is found that these galaxies contain less gas and harbor giant sup…
We recently developed an automated method, auto-GMM to decompose simulated galaxies. It extracts kinematic structures in an accurate, efficient, and unsupervised way. We use auto-GMM to study the stellar kinematic structures of disk galaxies from the TNG100 run of IllustrisTNG. We identify four to five structures that are commonly present among the diverse galaxy population. Structures having strong to moderate rotation are defined as cold and warm disks, respectively. Spheroidal structures dominated by random motions are classified as bulges or stellar halos, depending on how tightly bound th…
A significant fraction of nearby late-type galaxies are lopsided. We study the asymmetry of the stellar component in a sample of well-resolved disky galaxies selected from the last snapshot of the Illustris TNG100 simulation based on their flatness and rotational support. Among 1912 disks, we identify 161 objects with significant asymmetry in terms of the m=1 Fourier mode of the stellar component within (1-2) stellar half-mass radii and describe their properties using three representative examples. The profiles of the m=1 mode typically increase with radius, and the corresponding phase is cons…
The galaxy Malin 1 contains the largest stellar disk known but the formation mechanism of this structure has been elusive. In this paper, we report a Malin 1 analogue in the 100 Mpc IllustrisTNG simulation and describe its formation history. At redshift zero, this massive galaxy, having a maximum circular velocity $V_{\rm max}$ of 430 ${\rm km\ s^{-1}}$, contains a 100 kpc gas/stellar disk with morphology similar to Malin 1. The simulated galaxy reproduces well many observed features of Malin 1's vast disk, including its stellar ages, metallicities, and gas rotation curve. We trace the extende…
Almost two-thirds of disk galaxies in the local universe host bars, which serve as important drivers of secular evolutionary processes. While cosmological simulations are powerful tools to study the formation and evolution of galaxies, they have often struggled to generate reasonable bar populations. We measure the fraction, size, and strength of bars in 3866 disk galaxies from the TNG100 run of the advanced cosmological simulation IllustrisTNG. Consistent with observations, about 55% of disk galaxies with stellar mass $M_* \approx 10^{10.6}\, M_\odot$ are barred, and the relation between bar …
We present the 3-{\it dimensional} intrinsic alignment power spectra between the projected 2d galaxy shape/spin and the 3d tidal field across $0.1<k/h{\rm Mpc}^{-1}<60$ using cosmological hydrodynamical simulation, Illustris-TNG300, at redshifts ranging from $0.3$ to $2$. The shape-tidal field alignment increases with galaxy mass and the linear alignment coefficient $A_{\rm IA}$, defined with respect to the primordial tidal field, is found to have weak redshift dependence. We also show a promising detection of the shape/spin-tidal field alignments for stellar mass limited samples and a weak or…
We use the IllustrisTNG (TNG) simulations to explore the galaxy-halo connection as inferred from state-of-the-art cosmological, magnetohydrodynamical simulations. With the high mass resolution and large volume achieved by combining the 100 Mpc (TNG100) and 300 Mpc (TNG300) volumes, we establish the mean occupancy of central and satellite galaxies and their dependence on the properties of the dark matter haloes hosting them. We derive best-fitting HOD parameters from TNG100 and TNG300 for target galaxy number densities of $\bar{n}_g = 0.032\,h^3$Mpc$^{-3}$ and $\bar{n}_g = 0.016\,h^3$Mpc$^{-3}$…
We have carried out a controlled comparison of the structural and kinematic properties of the circumgalactic medium (CGM) around Milky Way mass galaxies in the Illustris and IllustrisTNG simulations. Very striking differences are found. At z=0, gas column density and temperature profiles at large radii ($\sim 100$ kpc) correlate strongly with disk gas mass fraction in Illustris, but not in TNG. The neutral gas at large radii is preferentially aligned in the plane of the disk in TNG, whereas it is much more isotropic in Illustris. The vertical coherence scale of the rotationally supported gas i…
How mergers shape galaxy morphology in the IllustrisTNG simulation
The Chinese University of Hong Kong（香港中文大学）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学前沿天文与天体物理研究所）；School of Physics and Microelectronics, Zhengzhou University（郑州大学物理与电气工程学院）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）
Galaxy clusters are known to induce gas loss in infalling galaxies due to the ram pressure exerted by the intracluster medium over their gas content. In this paper, we investigate this process through a set of simulations of Milky Way like galaxies falling inside idealised clusters of 10$^{14}$ M$_\odot$ and 10$^{15}$ M$_\odot$, containing a cool-core or not, using the adaptive mesh refinement code RAMSES. We use these simulations to constrain how much of the initial mass contained in the gaseous disk of the galaxy will be converted into stars and how much of it will be lost, after a single cr…
We present two sets of grid-based hydrodynamical simulations of high-velocity clouds (HVCs) traveling through the diffuse, hot Galactic halo. These HI clouds have been suggested to provide fuel for ongoing star formation in the Galactic disk. The first set of models is best described as a wind-tunnel experiment in which the HVC is exposed to a wind of constant density and velocity. In the second set of models we follow the trajectory of the HVC on its way through an isothermal hydrostatic halo towards the disk. Thus, we cover the two extremes of possible HVC trajectories. The resulting cloud m…
Warps are common features in both stellar and gaseous disks of nearby spiral galaxies with the latter usually easier to detect. Several theories have been proposed in the literature to explain their formation and prevalence, including tidal interactions with external galaxies. Observational correlations also suggest the importance of tides for warp formation. Here, we use the TNG100 run from the magnetohydrodynamical cosmological simulation suite IllustrisTNG to investigate the connection between interactions and the formation of gas warps. We find that in the sample of well-resolved gas-rich …
We analyze the kinematics as a function of stellar age for Andromeda (M31) mass analogs from the IllustrisTNG cosmological simulation. We divide the star particles into four age groups: less than 1 Gyr, 1 to 5 Gyr, 5 to 10 Gyr, and greater 10 Gyr, and compare the kinematics of these groups to that of the neutral gas cells. We calculate rotation curves for the stellar and gaseous components of each analog from 2 kpc to 20 kpc from the center of mass. We find that the lag, or asymmetric drift (AD), between the gas rotation curve and the stellar rotation curve on average increases with stellar ag…
We present radial gas-phase metallicity profiles, gradients, and break radii at redshift $z = 0 - 3$ from the TNG50-1 star-forming galaxy population. These metallicity profiles are characterized by an emphasis on identifying the steep inner gradient and flat outer gradient. From this, the break radius, $r_{\rm Break}$, is defined as the region where the transition occurs. We observe the break radius having a positive trend with mass that weakens with redshift. When normalized by the stellar half-mass radius, the break radius has a weaker relation with both mass and redshift. To test if our res…
In the standard disk galaxy formation model, the sizes of galactic disks are tightly related to the spin parameters $λ$ of their dark matter haloes. The model has been wildly adopted by various semi-analytic galaxy formation models which have been extremely successful to interpret a large body of observational data. However, the size-$λ$ correlation was rarely seen in most modern hydrodynamical simulations of galaxy formation. In this short paper, we make use of 4 sets of large hydrodynamical simulations to explore the size-spin parameter relation with a large sample of simulated disk galaxies…
We investigate the influence of active galactic nucleus (AGN) feedback on the galaxy cold gas content and its connection to galaxy quenching in three hydrodynamical simulations of Illustris, IllustrisTNG and SIMBA. By comparing to the observed atomic and molecular neutral hydrogen measurements for central galaxies, we find that Illustris over-predicts the cold gas masses in star-forming galaxies and significantly under-predicts them for quenched galaxies. IllustrisTNG performs better in this comparison than Illustris, but quenched galaxies retain too much cold gas compared with observations. S…
We analyze the optical morphologies of galaxies in the IllustrisTNG simulation at $z\sim0$ with a Convolutional Neural Network trained on visual morphologies in the Sloan Digital Sky Survey. We generate mock SDSS images of a mass complete sample of $\sim12,000$ galaxies in the simulation using the radiative transfer code SKIRT and include PSF and noise to match the SDSS r-band properties. The images are then processed through the exact same neural network used to estimate SDSS morphologies to classify simulated galaxies in four morphological classes (E, S0/a, Sab, Scd). The CNN model finds tha…
Massive high-redshift quiescent compact galaxies (nicknamed red nuggets) have been traditionally connected to present-day elliptical galaxies, often overlooking the relationships that they may have with other galaxy types. We use large bulge-disk decomposition catalogues based on the Sloan Digital Sky Survey (SDSS) to check the hypothesis that red nuggets have survived as compact cores embedded inside the haloes or disks of present-day massive galaxies. In this study, we designate a "compact core" as the bulge component that satisfies a prescribed compactness criterion. Photometric and dynamic…
A significant fraction of spiral galaxies are red, gas-poor, and have low star formation rates (SFRs). We study these unusual objects using the IllustrisTNG100 simulation. Among 1912 well-resolved disk galaxies selected from the last simulation output, we identify 377 red objects and describe their properties and origins using a few representative examples. The simulated red spirals turn out to be typically very gas-poor, have very low SFRs, are more metal-rich, and have larger stellar masses than the remaining disks. Only about 13% of red spirals suffered strong mass loss and thus could have …
The coevolution of galaxies and their metal content serves as an important test for galaxy feedback models. We analyze the distribution and evolution of metals within the IllustrisTNG simulation suite with a focus on the gas-phase mass-metallicity relation (MZR). We find that the IllustrisTNG model broadly reproduces the slope and normalization evolution of the MZR across the redshift range $0<z<2$ and mass range $10^9 < M_*/\mathrm{M}_\odot < 10^{10.5}$. We make predictions for the high redshift ($2<z<10$) metal content of galaxies which is described by a gradual decline in the normalization …
We study a sample of bar-like galaxies in the Illustris TNG100 simulation, in which almost the whole stellar component is in the form of a prolate spheroid. The sample is different from the late-type barred galaxies studied before. In addition to the requirement of a high enough stellar mass and resolution, the 277 galaxies were selected based on the single condition of a low enough ratio of the intermediate to long axis of the stellar component. We followed the mass and shape evolution of the galaxies as well as their interactions with other objects and divided them into three classes based o…
We investigate the stellar mass loss of gas rich galaxies falling into clusters due to the change in the gravitational potential caused by the ram pressure stripping of their gas. We model the satellites with exponential stellar and gas disk profiles, assume rapid ram pressure stripping, and follow the stellar orbits in the shocked potential. Due to the change of the potential, the stars move from circular orbits to elliptical orbits with apocenters that are often outside the tidal radius, causing those stars to be stripped. We explore the impact of the redshift of infall, gas fraction, satell…
We present a new cosmological, magnetohydrodynamical simulation for galaxy formation: TNG50, the third and final installment of the IllustrisTNG project. TNG50 evolves 2x2160^3 dark-matter particles and gas cells in a volume 50 comoving Mpc across. It hence reaches a numerical resolution typical of zoom-in simulations, with a baryonic element mass of 8.5x10^4 Msun and an average cell size of 70-140 parsecs in the star-forming regions of galaxies. Simultaneously, TNG50 samples ~700 (6,500) galaxies with stellar masses above 10^10 (10^8) Msun at z=1. Here we investigate the structural and kinema…
We study the correlation of orbital poles of the 11 classical satellite galaxies of the Milky Way, comparing results from previous proper motions with the independent data by Gaia DR2. Previous results on the degree of correlation and its significance are confirmed by the new data. A majority of the satellites co-orbit along the Vast Polar Structure, the plane (or disk) of satellite galaxies defined by their positions. The orbital planes of eight satellites align to $<20^\circ$ with a common direction, seven even orbit in the same sense. Most also share similar specific angular momenta, though…
Massive disk galaxies with high surface brightness plus low surface brightness stellar disks, hosted by massive dark matter halo -- a TNG50 simulation study
Tata Institute of Fundamental Research（塔塔基础研究所）；Inter-University Centre for Astronomy and Astrophysics（大学间天体物理中心）
Any viable cosmological framework has to match the observed proportion of early- and late-type galaxies. In this contribution, we focus on the distribution of galaxy morphological types in the standard model of cosmology (Lambda cold dark matter, $Λ$CDM). Using the latest state-of-the-art cosmological $Λ$CDM simulations known as Illustris, IllustrisTNG, and EAGLE, we calculate the intrinsic and sky-projected aspect ratio distribution of the stars in subhalos with stellar mass $M_* > 10^{10}\,M_\odot$ at redshift $z=0$. There is a significant deficit of intrinsically thin disk galaxies, which h…
The IllustrisTNG simulations reproduce the observed scaling relation between stellar specific angular momentum (sAM) $j_{\rm s}$ and mass $M_{\rm s}$ of central galaxies. We show that the local $j_{\rm s}$-$M_{\rm s}$ relation ${\rm log}\ j_{\rm s} = 0.55 \ {\rm log}\ M_{\rm s} + 2.77$ develops at $z\lesssim 1$ in disk-dominated galaxies. We provide a simple model that describes well such a connection between halos and galaxies. The index 0.55 of the $j_{\rm s}$-$M_{\rm s}$ relation comes from the product of the indices of the $j_{\rm tot}\propto M_{\rm tot}^{0.81}$, $M_{\rm tot}\propto M_{\rm…
We employ an improved methodology to insert live stellar disks into high-resolution dark matter simulations of Milky Way sized halos, allowing us to investigate the fate of thin stellar disks in the tumultuous environment of cold dark matter structures. We study a set of eight different halos, drawn from the Aquarius simulation project, in which stellar disks are adiabatically grown with a prescribed structure, and then allowed to self-consistently evolve. The initial velocity distribution is set-up in very good equilibrium with the help of the GALIC code. We find that the residual triaxiality…
Disks of gas accreting onto supermassive black holes are thought to power active galactic nuclei (AGN). Stars may form in gravitationally unstable regions of these disks, or may be captured from nuclear star clusters. Because of the dense gas environment, the evolution of such embedded stars can diverge dramatically from those in the interstellar medium. This work extends previous studies of stellar evolution in AGN disks by exploring a variety of ways that accretion onto stars in AGN disks may differ from Bondi accretion. We find that tidal effects from the supermassive black hole significant…
Star-forming disk galaxies at high redshift are often subject to violent disk instability, characterized by giant clumps whose fate is yet to be understood. The main question is whether the clumps disrupt within their dynamical timescale (<50Myr), like molecular clouds in today's galaxies, or whether they survive stellar feedback for more than a disk orbital time (~300Myr) in which case they can migrate inward and help building the central bulge. We present 3.5-7pc resolution AMR simulations of high-redshift disks including photo-ionization, radiation pressure, and supernovae feedback (Renaud …
Tracing the dynamical and structural complexity of spiral galaxy centres
University of Vienna（维也纳大学）；Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Universidad de La Laguna（拉古纳大学）；Graduate Institute for Advanced Studies, SOKENDAI（综合研究大学院大学）；Subaru Telescope, National Astronomical Observatory of Japan（日本国立天文台 Subaru 望远镜）；Leiden University（莱顿大学）；Durham University（杜伦大学）
