3 research outputs found
Magnetic field draping around clumpy high-velocity clouds in galactic halo
Throughout the passage within the Galactic halo, high-velocity clouds (HVCs)
sweep up ambient magnetic fields and form stretched and draped configurations
of magnetic fields around them. Many earlier numerical studies adopt
spherically symmetric uniform-density clouds as initial conditions for
simplicity. However, observations demonstrate that HVCs are clumpy and
turbulent. In this paper, we perform 3D magnetohydrodynamic simulations to
study the evolution of clouds with initial density distributions described by
power-law spatial power spectra. We systematically study the role of (i) the
initial density structure, (ii) halo magnetic fields, and (iii) radiative
cooling efficiency upon infalling HVCs. We find that (i) the clouds' density
structure regulates mixing and mass growth. Uniform clouds grow from the onset
of the simulations while clumpy clouds initially lose gas and then grow at
later times. Along the same lines, the growth curve of clumpy clouds depends on
the slope of the initial density power spectra. (ii) Magnetic fields suppress
hydrodynamic instabilities and the growth of small-scale structures. As a
result, magnetized clouds develop long filaments extended along the streaming
direction whereas non-magnetized clouds are fragmented into many small clumps.
(iii) Efficient cooling keeps the main cloud body more compact and produces
decelerated dense clumps condensed from the halo gas. This work potentially
helps us understand and predict the observed properties of HVCs such as the
detectability of magnetized clouds, the presence of decelerated HI structures
associated with HVC complexes and small-scale features, and a possible link
between the origin and the fate of HVCs.Comment: 21 pages, 13 figures, Accepted to MNRA
YZiCS: Unveiling the Quenching History of Cluster Galaxies Using Phase-space Analysis
We used the time since infall (TSI) of galaxies, obtained from the Yonsei Zoom-in Cluster Simulation, and the star formation rate (SFR) from the Sloan Digital Sky Survey Data Release 10 to study how quickly the star formation of disk galaxies is quenched in cluster environments. We first confirm that both simulated and observed galaxies are consistently distributed in phase space. We then hypothesize that the TSI and SFR are causally connected; thus, both the TSI and SFR of galaxies at each position of phase space can be associated through abundance matching. Using a flexible model, we derive the star formation history (SFH) of cluster galaxies that best reproduces the relationship between the TSI and SFR at z ~ 0.08. According to this SFH, we find that galaxies with M * > 109.5 M ⊙ generally follow the so-called "delayed-then-rapid" quenching pattern. Our main results are as follows: (i) part of the quenching takes place outside clusters through mass quenching and preprocessing. The e-folding timescale of this "ex situ quenching phase" is roughly 3 Gyr with a strong inverse mass dependence. (ii) The pace of quenching is maintained roughly for 2 Gyr ("delay time") during the first crossing time into the cluster. During the delay time, quenching remains gentle, probably because gas loss happens primarily on hot and neutral gases. (iii) Quenching becomes more dramatic (e-folding timescale of roughly 1 Gyr) after delay time, probably because ram pressure stripping is strongest near the cluster center. Counterintuitively, more massive galaxies show shorter quenching timescales mainly because they enter their clusters with lower gas fractions due to ex situ quenching
Sampling the Faraday rotation sky of TNG50: Imprint of the magnetised circumgalactic medium around Milky Way-like galaxies
Faraday rotation measure (RM) is arguably the most practical observational
tracer of magnetic fields in the diffuse circumgalactic medium (CGM). We sample
synthetic Faraday rotation skies of Milky Way-like galaxies in TNG50 of the
IllustrisTNG project by placing an observer inside the galaxies at a solar
circle-like position. Our synthetic RM grids emulate specifications of current
and upcoming surveys; the NRAO VLA Sky Survey (NVSS), the Polarisation Sky
Survey of the Universe's Magnetism (POSSUM), and a future Square Kilometre
Array (SKA1-mid) polarisation survey. It has been suggested that magnetic
fields regulate the survival of high-velocity clouds. However, there is only a
small number of observational detections of magnetised clouds thus far. In the
first part of the paper, we test conditions for the detection of magnetised
circumgalactic clouds. Based on the synthetic RM samplings of clouds in the
simulations, we predict upcoming polarimetric surveys will open opportunities
for the detection of even low-mass and distant clouds. In the second part of
the paper, we investigate the imprint of the CGM in the all-sky RM
distribution. We test whether the RM variation produced by the CGM is
correlated with global galaxy properties, such as distance to a satellite,
specific star formation rate, neutral hydrogen covering fraction, and accretion
rate to the supermassive black hole. We argue that the observed fluctuation in
the RM measurements on scales less than 1 degree, which has been considered an
indication of intergalactic magnetic fields, might in fact incorporate a
significant contribution of the Milky Way CGM.Comment: 18 pages, 11 figures, Accepted to MNRA