Yuanyuan Su

Joint XMM-Newton and Chandra observations of the NGC 1407/1400 complex: A tail of an early-type galaxy and a tale of a nearby merging group

The nearby group centered on its bright central galaxy NGC?1407 has been suggested by previous kinematic studies to be an unusually dark system. It is also known for hosting a bright galaxy, NGC?1400, with a large radial velocity (1200?km?s?1) with respect to the group center. Previous ROSAT X-ray observations revealed an extended region of enhanced surface brightness just eastward of NGC?1400. We investigate the NGC?1407/1400 complex with XMM-Newton and Chandra observations. We find that the temperature and metallicity of the enhanced region are different (cooler and more metal rich) than those of the surrounding group gas but are consistent with those of the interstellar medium (ISM) in NGC?1400. The relative velocity of NGC?1400 is large enough that much of its ISM could have been ram pressure stripped while plunging through the group atmosphere. We conclude that the enhanced region is likely to be hot gas stripped from the ISM of NGC?1400. We constrain the motion of NGC?1400 using the pressure jump at its associated stagnation front and the total mass profile of the NGC?1407 group. We conclude that NGC?1400 is moving within ~30? of the line of sight with Mach number . We do not detect any obvious shock features in this complex, perhaps because of the high line-of-sight motion of NGC?1400. With an XMM-Newton pointing on the relatively relaxed eastern side of NGC?1407, we derive a hydrostatic mass for this group of ~1 ? 1013 M ? within 100?kpc. The total mass extrapolated to the virial radius (681?kpc) is 3.8 ? 1013 M ?, which puts an upper limit of ~300 on the mass-to-light ratio of this group. This suggests that the NGC?1407 group is not an unusually dark group.

The Entire Virial Radius of the Fossil Cluster RX J1159+5531: I. Gas Properties

Previous analysis of the fossil-group/cluster RX J1159+5531 with X-ray observations from a central Chandra pointing and an offset-north Suzaku pointing indicate a radial intracluster medium (ICM) entropy profile at the virial radius (Rvir) consistent with predictions from gravity-only cosmological simulations, in contrast to other cool-core clusters. To examine the generality of these results, we present three new Suzaku observations that, in conjunction with the north pointing, provide complete azimuthal coverage out to Rvir. With two new Chandra ACIS-I observations overlapping the north Suzaku pointing, we have resolved ≳50% of the cosmic X-ray background there. We present radial profiles of the ICM density, temperature, entropy, and pressure obtained for each of the four directions. We measure only modest azimuthal scatter in the ICM properties at R200 between the Suzaku pointings: 7.6% in temperature and 8.6% in density, while the systematic errors can be significant. The temperature scatter, in particular, is lower than that studied at R200 for a small number of other clusters observed with Suzaku. These azimuthal measurements verify that RX J1159+5531 is a regular, highly relaxed system. The well-behaved entropy profiles we have measured for RX J1159+5531 disfavor the weakening of the accretion shock as an explanation of the entropy flattening found in other cool-core clusters but is consistent with other explanations such as gas clumping, electron-ion non-equilibrium, non-thermal pressure support, and cosmic-ray acceleration. Finally, we mention that the large-scale galaxy density distribution of RX J1159+5531 seems to have little impact on its gas properties near Rvir.

The Scatter in the Hot Gas Content of Early-type Galaxies

Optically similar early-type galaxies are observed to have a large and poorly understood range in the amount of hot, X-ray-emitting gas they contain. To investigate the origin of this diversity, we studied the hot gas properties of all 42 early-type galaxies in the multiwavelength ATLAS3D survey that have sufficiently deep Chandra X-ray observations. We related their hot gas properties to a number of internal and external physical quantities. To characterize the amount of hot gas relative to the stellar light, we use the ratio of the gaseous X-ray luminosity to the stellar K-band luminosity, ; we also use the deviations of from the best-fit ?LK relation (denoted ). We quantitatively confirm previous suggestions that various effects conspire to produce the large scatter in the observed relation. In particular, we find that the deviations are most strongly positively correlated with the (low rates of) star formation and the hot gas temperatures in the sample galaxies. This suggests that mild stellar feedback may energize the gas without pushing it out of the host galaxies. We also find that galaxies in high galaxy density environments tend to be massive slow rotators, while galaxies in low galaxy density environments tend to be low mass, fast rotators. Moreover, cold gas in clusters and fields may have different origins. The star formation rate increases with cold gas mass for field galaxies but it appears to be uncorrelated with cold gas for cluster galaxies.

DEEP CHANDRA OBSERVATIONS OF NGC 1404: CLUSTER PLASMA PHYSICS REVEALED BY AN INFALLING EARLY-TYPE GALAXY

The intracluster medium (ICM), as a magnetized and highly ionized fluid, provides an ideal laboratory to study plasma physics under extreme conditions that cannot yet be achieved on Earth. NGC 1404 is a bright elliptical galaxy that is being gas stripped as it falls through the ICM of the Fornax Cluster. We use the new {\sl Chandra} X-ray observations of NGC 1404 to study ICM microphysics. The interstellar medium (ISM) of NGC 1404 is characterized by a sharp leading edge, 8 kpc from the galaxy center, and a short downstream gaseous tail. Contact discontinuities are resolved on unprecedented spatial scales (

Buoyant AGN Bubbles in the Quasi-isothermal Potential of NGC 1399

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THE ENTIRE VIRIAL RADIUS OF THE FOSSIL CLUSTER RXJ 1159 + 5531. II. DARK MATTER AND BARYON FRACTION

\,pc) due to the combination of the proximity of NGC 1404, the superb spatial resolution of {\sl Chandra}, and the very deep (670 ksec) exposure. At the leading edge, we observe sub-kpc scale eddies generated by Kelvin-Helmholtz instability and put an upper limit of 5\% Spitzer on the isotropic viscosity of the hot cluster plasma. We also observe mixing between the hot cluster gas and the cooler galaxy gas in the downstream stripped tail, which provides further evidence of a low viscosity plasma. The assumed ordered magnetic fields in the ICM ought to be smaller than 5\,

The Recent Growth History of the Fornax Cluster Derived from Simultaneous Sloshing and Gas Stripping: Simulating the Infall of NGC 1404

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X-ray cavities in the hot corona of the lenticular galaxy NGC 4477

G to allow KHI to develop. The lack of evident magnetic draping layer just outside the contact edge is consistent with such an upper limit.

Gas Sloshing Regulates and Records the Evolution of the Fornax Cluster

The Fornax Cluster is a low-mass cool-core galaxy cluster. We present a deep {\sl Chandra} study of NGC 1399, the central dominant elliptical galaxy of Fornax. The cluster center harbors two symmetric X-ray cavities coincident with a pair of radio lobes fed by two collimated jets along a north-south axis. A temperature map reveals that the AGN outburst has created a channel filled with cooler gas out to a radius of 10 kpc. The cavities are surrounded by cool bright rims and filaments that may have been lifted from smaller radii by the buoyant bubbles. X-ray imaging suggests a potential ghost bubble of

Uplift, Feedback, and Buoyancy: Radio Lobe Dynamics in NGC 4472

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