155 research outputs found
A rotating satellite plane around Milky Way-like galaxy from the TNG50 simulation
We study the Satellite Plane Problem of the Milky Way\ (MW) by using the
recently published simulation data of TNG50-1. Here, we only consider the
satellite plane consisting of the brightest 14 MW satellites \ (11 classical
satellites plus Canes Venatici I\ (CVn I), Crater II and Antlia II). One halo\
(haloID=395, at z=0, hereafter halo395 ) of 231 MW like candidates, possesses a
satellite plane as spatially thin and kinematically coherent as the observed
one has been found. Halo395 resembles the MW in a number of intriguing ways: it
hosts a spiral central galaxy and its satellite plane is almost ()perpendicular to the central stellar disk. In addition, halo395 is
embedded in a sheet plane, with a void on the top and bottom, similar to the
local environment of MW. More interestingly, we found that the 11 of 14 of the
satellites on the plane of halo395, arise precisely from the peculiar geometry
of its large-scale environment\ (e.g. sheet and voids). The remaining three
members appeared at the right place with the right velocity by chance at z=0.
Our results support previous studies wherein the Satellite Plane Problem is not
seen as a serious challenge to the CDM model and its formation is
ascribed to the peculiarities of our environment.Comment: Accepted for publication by ApJ. The article title has been changed
since the last version, and some minor corrections have been mad
Quenching of Massive Disk Galaxies in the IllustrisTNG Simulation
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 supermassive black
holes(SMBHs) (above ) than their star forming counterparts.
By tracing their formation history, we found that quenched disk galaxies formed
early and preserved disk morphology for cosmological time scales. They have
experienced less than one major merger on average and it is mainly mini-mergers
(mass ratio 1/10) that contribute to the growth of their SMBHs. In the
Illustris-TNG simulation the black hole feedback mode switches from thermal to
kinetic feedback when the black hole mass is more massive than , which is more efficient to eject gas outside of the galaxy
and to suppress further cooling of hot gaseous halo. We conclude that kinetic
AGN feedback in massive red/quenched disk galaxy is the dominant quenching
mechanism.Comment: 15 pages, 13 figures, accepted to Ap
Merger by Migration at the Final Phase of Common Envelope Evolution
I find the common envelope (CE) energy formalism, the CE \alpha-prescription,
to be inadequate to predict the final orbital separation of the CE evolution in
massive envelopes. I find that when the orbital separation decreases to ~10
times the final orbital separation predicted by the CE \alpha-prescription, the
companion has not enough mass in its vicinity to carry away its angular
momentum. The core-secondary binary system must get rid of its angular momentum
by interacting with mass further out. The binary system interacts
gravitationally with a rapidly-rotating flat envelope, in a situation that
resembles planet-migration in protoplanetary disks. The envelope convection of
the giant carries energy and angular momentum outward. The basic assumption of
the CE \alpha-prescription, that the binary system's gravitational energy goes
to unbind the envelope, breaks down. Based on that, I claim that merger is a
common outcome of the CE evolution of AGB and red super-giants stars with an
envelope to secondary mass ratio of (M_env/M_2)>~5. I discuss some other
puzzling observations that might be explained by the migration and merger
processes.Comment: New Astronomy, in pres
Sound Waves Excitation by Jet-Inflated Bubbles in Clusters of Galaxies
We show that repeated sound waves in the intracluster medium (ICM) can be
excited by a single inflation episode of an opposite bubble pair. To reproduce
this behavior in numerical simulations the bubbles should be inflated by jets,
rather than being injected artificially. The multiple sound waves are excited
by the motion of the bubble-ICM boundary that is caused by vortices inside the
inflated bubbles and the backflow (`cocoon') of the ICM around the bubble.
These sound waves form a structure that can account for the ripples observed in
the Perseus cooling flow cluster. We inflate the bubbles using slow massive
jets, with either a wide opening angle or that are precessing. The jets are
slow in the sense that they are highly sub-relativistic, ,
and they are massive in the sense that the pair of bubbles carry back to the
ICM a large fraction of the cooling mass, i.e., \sim 1-50 M_\odot \yr^{-1}.
We use a two-dimensional axisymmetric (referred to as 2.5D) hydrodynamical
numerical code (VH-1).Comment: submitted to MNRA
Fermi-arc diversity on surface terminations of the magnetic Weyl semimetal Co3Sn2S2
Bulk-surface correspondence in Weyl semimetals assures the formation of
topological "Fermi-arc" surface bands whose existence is guaranteed by bulk
Weyl nodes. By investigating three distinct surface terminations of the
ferromagnetic semimetal Co3Sn2S2 we verify spectroscopically its classification
as a time reversal symmetry broken Weyl semimetal. We show that the distinct
surface potentials imposed by three different terminations modify the Fermi-arc
contour and Weyl node connectivity. On the Sn surface we identify
intra-Brillouin zone Weyl node connectivity of Fermi-arcs, while on Co
termination the connectivity is across adjacent Brillouin zones. On the S
surface Fermi-arcs overlap with non-topological bulk and surface states that
ambiguate their connectivity and obscure their exact identification. By these
we resolve the topologically protected electronic properties of a Weyl
semimetal and its unprotected ones that can be manipulated and engineered
Constrained simulations of the Local Group: on the radial distribution of substructures
We examine the properties of satellites found in high resolution simulations
of the local group. We use constrained simulations designed to reproduce the
main dynamical features that characterize the local neighborhood, i.e. within
tens of Mpc around the Local Group (LG). Specifically, a LG-like object is
found located within the 'correct' dynamical environment and consisting of
three main objects which are associated with the Milky Way, M31 and M33. By
running two simulations of this LG from identical initial conditions - one with
and one without baryons modeled hydrodynamically - we can quantify the effect
of gas physics on the population of subhaloes in an environment similar
to our own. We find that above a certain mass cut, subhaloes in hydrodynamic simulations are more
radially concentrated than those in simulations with out gas. This is caused by
the collapse of baryons into stars that typically sit in the central regions of
subhaloes, making them denser. The increased central density of such a subhalo,
results in less mass loss due to tidal stripping than the same subhalo
simulated with only dark matter. The increased mass in hydrodynamic subhaloes
with respect to dark matter ones, causes dynamical friction to be more
effective, dragging the subhalo towards the centre of the host. This results in
these subhaloes being effectively more radially concentrated then their dark
matter counterparts.Comment: 12 pages, 9 figure
Transient outburst events from tidally disrupted asteroids near white dwarfs
We discuss the possibility of observing the transient formation event of an
accretion disk from the tidal destruction process of an asteroid near a white
dwarf (WD). This scenario is commonly proposed as the explanation for dusty
disks around WDs. We find that the initial formation phase lasts for about a
month and material that ends in a close orbit near the WD forms a gaseous disk
rather than a dusty disk. The mass and size of this gaseous accretion disk is
very similar to that of Dwarf Novae (DNe) in quiescence. The bolometric
luminosity of the event at maximum is estimated to be 0.001-0.1Lsun. Based on
the similarity with DNe we expect that transient outburst events such as
discussed here will be observed at wavelengths ranging from visible to the
X-ray, and be detected by present and future surveys.Comment: Accepted by New Astronom
Brain structural covariance networks in obsessive-compulsive disorder: a graph analysis from the ENIGMA Consortium.
Brain structural covariance networks reflect covariation in morphology of different brain areas and are thought to reflect common trajectories in brain development and maturation. Large-scale investigation of structural covariance networks in obsessive-compulsive disorder (OCD) may provide clues to the pathophysiology of this neurodevelopmental disorder. Using T1-weighted MRI scans acquired from 1616 individuals with OCD and 1463 healthy controls across 37 datasets participating in the ENIGMA-OCD Working Group, we calculated intra-individual brain structural covariance networks (using the bilaterally-averaged values of 33 cortical surface areas, 33 cortical thickness values, and six subcortical volumes), in which edge weights were proportional to the similarity between two brain morphological features in terms of deviation from healthy controls (i.e. z-score transformed). Global networks were characterized using measures of network segregation (clustering and modularity), network integration (global efficiency), and their balance (small-worldness), and their community membership was assessed. Hub profiling of regional networks was undertaken using measures of betweenness, closeness, and eigenvector centrality. Individually calculated network measures were integrated across the 37 datasets using a meta-analytical approach. These network measures were summated across the network density range of K = 0.10-0.25 per participant, and were integrated across the 37 datasets using a meta-analytical approach. Compared with healthy controls, at a global level, the structural covariance networks of OCD showed lower clustering (P < 0.0001), lower modularity (P < 0.0001), and lower small-worldness (P = 0.017). Detection of community membership emphasized lower network segregation in OCD compared to healthy controls. At the regional level, there were lower (rank-transformed) centrality values in OCD for volume of caudate nucleus and thalamus, and surface area of paracentral cortex, indicative of altered distribution of brain hubs. Centrality of cingulate and orbito-frontal as well as other brain areas was associated with OCD illness duration, suggesting greater involvement of these brain areas with illness chronicity. In summary, the findings of this study, the largest brain structural covariance study of OCD to date, point to a less segregated organization of structural covariance networks in OCD, and reorganization of brain hubs. The segregation findings suggest a possible signature of altered brain morphometry in OCD, while the hub findings point to OCD-related alterations in trajectories of brain development and maturation, particularly in cingulate and orbitofrontal regions
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