We investigate the origin and nature of the multiple sloshing cold fronts in the core of Abell 496 by direct comparison between observations and dedicated hydrodynamical simulations. Our simulations ...model a minor merger with a 4 × 1013 M⊙ subcluster crossing A496 from the south-west to the north-north-east, passing the cluster core in the south-east at a pericentre distance of 100 to a few × 100 kpc about 0.6-0.8 Gyr ago. The gas sloshing triggered by the merger can reproduce almost all observed features, e.g. the characteristic spiral-like brightness residual distribution in the cluster centre and its asymmetry out to 500 kpc, also the positions of and contrasts across the cold fronts. If the subcluster passes close (100 kpc) to the cluster core, the resulting shear flows are strong enough to trigger Kelvin-Helmholtz instabilities that in projection resemble the peculiar kinks in the cold fronts of Abell 496. Finally, we show that sloshing does not lead to a significant modification of the global intracluster medium profiles but a mild oscillation around the initial profiles.
Abstract
Analyses of major group mergers are key to understanding the evolution of large-scale structure in the Universe and the microphysical properties of the hot gas in these systems. We present ...imaging and spectral analyses of deep Chandra observations of hot gas structures formed in the major merger of the NGC 7618 and UGC 12491 galaxy groups and compare the observed hot gas morphology, temperatures, and abundances with recent simulations. The morphology of the observed multiple cold front edges and boxy wings are consistent with those expected to be formed by Kelvin–Helmholtz instabilities and gas sloshing in inviscid gas. The arc-shaped slingshot tail morphologies seen in each galaxy suggest that the dominant galaxies are near their orbital apogee after having experienced at least one core passage at a large impact parameter.
ABSTRACT We present an analysis of the complex gas hydrodynamics in the X-ray-luminous galaxy cluster RX J1347.5-1145 caught in the act of merging with a subcluster to its southeast using a combined ...186 ks Chandra exposure, 2.5 times greater than previous analyses. The primary cluster hosts a sloshing cold front spiral traced by four surface brightness edges west, southeast, east, and northeast from the primary central dominant galaxy, suggesting that the merger is in the plane of the sky. We measure temperature and density ratios across these edges, confirming that they are sloshing cold fronts. We observe the eastern edge of the subcluster infall shock, confirming that the observed subcluster is traveling from the southwest to the northeast in a clockwise orbit. We measure a shock density contrast of and infer a Mach number of 1.25 0.08 and a shock velocity of km s−1. Temperature and entropy maps show cool, low-entropy gas trailing the subcluster in a southwestern tail, consistent with core shredding. Simulations suggest that a perturber in the plane of the sky on a clockwise orbit would produce a sloshing spiral winding counterclockwise, opposite to that observed. The most compelling solution to this discrepancy is that the observed southeastern subcluster is on its first passage, shock-heating gas during its clockwise infall, while the main cluster's clockwise cold front spiral formed from earlier encounters with a second perturber orbiting counterclockwise.
Protein arginine methyltransferase 5 (PRMT5) is a type II arginine methyltransferase that catalyzes the post-translational symmetric dimethylation of protein substrates. PRMT5 plays a critical role ...in regulating biological processes including transcription, cell cycle progression, RNA splicing, and DNA repair. As such, dysregulation of PRMT5 activity is implicated in the development and progression of multiple cancers and is a target of growing clinical interest. Described herein are the structure-based drug designs, robust synthetic efforts, and lead optimization strategies toward the identification of two novel 5,5-fused bicyclic nucleoside-derived classes of potent and efficacious PRMT5 inhibitors. Utilization of compound docking and strain energy calculations inspired novel designs, and the development of flexible synthetic approaches enabled access to complex chemotypes with five contiguous stereocenters. Additional efforts in balancing bioavailability, solubility, potency, and CYP3A4 inhibition led to the identification of diverse lead compounds with favorable profiles, promising in vivo activity, and low human dose projections.
ABSTRACT We describe a double-arc-like X-ray structure lying ∼15″-30″ (∼0.8-1.7 kpc) south of the NGC 5195 nucleus, visible in the merged exposures of long Chandra pointings of M51. The curvature and ...orientation of the arcs argues for a nuclear origin. The arcs are radially separated by ∼15″ (∼1 kpc), but are rotated relative to each other by ∼30 . From an archival image, we find a slender H -emitting region just outside the outer edge of the outer X-ray arc, suggesting that the X-ray-emitting gas plowed up and displaced the H -emitting material from the galaxy core. Star formation may have commenced in that arc. H emission is present at the inner arc, but appears more complex in structure. In contrast to an explosion expected to be azimuthally symmetric, the X-ray arcs suggest a focused outflow. We interpret the arcs as episodic outbursts from the central super-massive black hole (SMBH). We conclude that NGC 5195 represents the nearest galaxy exhibiting on-going, large-scale outflows of gas, in particular, two episodes of a focused outburst of the SMBH. The arcs represent a clear demonstration of feedback.
We present Chandra observations of hot gas structures, which are characteristic of gas-stripping during infall, in the Virgo cluster elliptical galaxy M60 (NGC4649) located 1 Mpc east of M87. Chandra ...X-ray images at 0.5-2 keV show a sharp leading edge in the surface brightness that is 12.4 0.1 kpc north and west of the galaxy center in the direction of M87 and characteristic of a merger cold front due to M60's motion through the Virgo ICM. We measured a temperature of 1.00 0.02 keV for an abundance of inside the edge and for an abundance of in the Virgo ICM free stream region. We find that the observed jump in surface brightness yields a density ratio between gas inside the edge and in the cluster free stream region. If the edge is a cold front due solely to the infall of M60 in the direction of M87, we find a pressure ratio of and Mach number of . For 1.37 keV Virgo gas, we find a total infall velocity for M60 of . We calculate the motion in the plane of the sky to be , implying an inclination angle of °. Surface brightness profiles also show the presence of a faint, diffuse gaseous tail. We identify filamentary gaseous wing structures caused by the galaxy's motion through the ICM. The structure and dimensions of these wings are consistent with simulations of Kelvin-Helmholtz instabilities, as expected if the gas-stripping is close to inviscid.
We use three-dimensional hydrodynamic simulations to investigate the effects of a soft X-ray background, which could have been produced by an early generation of mini-quasars, on the subsequent ...cooling and collapse of high-redshift pre-galactic clouds. The simulations use an Eulerian adaptive mesh refinement technique with initial conditions drawn from a flat Λ-dominated cold dark matter model cosmology to follow the non-equilibrium chemistry of nine chemical species in the presence of both a soft ultraviolet Lyman—Werner H2 photodissociating flux of strength FLW = 10−21 erg s−1 cm−2 Hz−1 and soft X-ray background extending to 7.2 keV, including the ionization and heating effects caused by secondary electrons. Although we vary the normalization of the X-ray background by two orders of magnitude, the positive feedback effect of the X-rays on cooling and collapse of the pre-galactic cloud expected owing to the increased electron fraction is quite mild, only weakly affecting the mass threshold for collapse and the fraction of gas within the cloud that is able to cool, condense and become available for star formation. Inside most of the cloud we find that H2 is in photodissociation equilibrium with the soft ultraviolet (UV) flux. The net buildup of the electron density needed to enhance H2 formation occurs too slowly compared with the H2 photodissociation and dynamical time-scales within the cloud to overcome the negative impact of the soft UV photodissociating flux on cloud collapse. However, we find that even in the most extreme cases the first objects to form do rely on molecular hydrogen as a coolant and we stress that our results do not justify the neglect of these objects in models of galaxy formation. Outside the cloud we find the dominant effect of a sufficiently strong X-ray background is to heat and partially ionize the intergalactic medium, in qualitative agreement with previous studies.
We use Chandra X-ray observations of the hot gas in and around NGC 6868 and NGC 6861 in the Telescopium galaxy group (AS0851) to probe the interaction history between these galaxies. Mean surface ...brightness profiles for NGC 6868 and NGC 6861 are each well described by double beta-models, suggesting that they are each the dominant galaxy in a galaxy subgroup about to merge. Surface brightness and temperature maps of the brightest group galaxy NGC 6868 show a cold front edge {approx}23 kpc to the north, and a cool 0.62 keV spiral-shaped tail to the south. Analysis of the temperature and density across the cold front constrains the relative motion between NGC 6868 and the ambient group gas to be at most transonic; while the spiral morphology of the tail strongly suggests that the cold front edge and tail are the result of gas sloshing due to the subgroup merger. The cooler central region of NGC 6861 is surrounded by a sheath of hot gas to the east and hot, bifurcated tails of X-ray emission to the west and northwest. We discuss supersonic infall of the NGC 6861 subgroup, sloshing from the NGC 6868 and NGC 6861 subgroup merger, and AGN heating as possible explanations for these features, and discuss possible scenarios that may contribute to the order of magnitude discrepancy between the Margorrian and black hole mass-sigma predictions for its central black hole.
We present XMM-Newton observations of a trail of enhanced X-ray emission extending along the full 8.'7 x 4' region between the large spiral galaxy NGC 6872 and the dominant elliptical galaxy NGC 6876 ...in the Pavo group, the first known X-ray trail associated with a spiral galaxy in a poor galaxy group and, with a projected length of 90 kpc, one of the longest known X-ray trails. The X-ray surface brightness in the trail region is roughly constant beyond 620 kpc of NGC 6876 in the direction of the spiral galaxy. The trail is hotter (61 keV) than the undisturbed Pavo IGM (60.5 keV) and has low metal abundances (0.2 Zsubz). The 0.5-2 keV luminosity of the trail, measured using a 67 x 90 kpc rectangular region, is 6.6 x 10super40 ergs ssuper-1. We compare the properties of gas in the trail to the spectral properties of gas in the spiral galaxy NGC 6872 and in the elliptical galaxy NGC 6876 to constrain its origin. We suggest that the X-ray trail is either IGM gas gravitationally focused into a Bondi-Hoyle wake, a thermal mixture of 660% Pavo IGM gas with 640% galaxy gas that has been removed from the spiral galaxy NGC 6872 by turbulent viscous stripping, or both, due to the spiral galaxy's supersonic motion at angle y 6 40 with respect to the plane of the sky, through the densest region of the Pavo IGM. Assuming y = 40 and a filling factor in a cylindrical volume with radius 33 kpc and projected length 90 kpc, the mean electron density and total hot gas mass in the trail are 1 x 10super-3super-1/2 cmsuper-3 and 1.1 x 10super10super1/2 Msubz, respectively. mmachacekcfa.harvard.edu
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