681 research outputs found
The Entire Virial Radius of the Fossil Cluster RXJ1159+5531: I. Gas Properties
Previous analysis of the fossil-group/cluster RXJ1159+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 () 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 . 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 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 for a small number of other
clusters observed with Suzaku. These azimuthal measurements verify that
RXJ1159+5531 is a regular, highly relaxed system. The well-behaved entropy
profiles we have measured for RXJ1159+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 RXJ1159+5531 seems to have little impact on its gas
properties near .Comment: Accepted for publication in Ap
The formation channels of multiphase gas in nearby early-type galaxies
The processes responsible for the assembly of cold and warm gas in early-type
galaxies (ETGs) are not well-understood. We report on the multiwavelength
properties of 15 non-central, nearby ( 0.00889) ETGs primarily through
Multi-Unit Spectroscopic Explorer (MUSE) and Chandra X-ray observations, to
address the origin of their multiphase gas. The MUSE data reveals 8/15 sources
contain warm ionized gas traced by the H emission line. The morphology
of this gas is found to be filamentary in 3/8 sources: NGC 1266, NGC 4374, and
NGC 4684 which is similar to that observed in many group and cluster-centered
galaxies. All H filamentary sources have X-ray luminosities exceeding
the expected emission from the stellar population, suggesting the presence of
diffuse hot gas which likely cooled to form the cooler phases. The morphology
of the remaining 5/8 sources are rotating gas disks, not as commonly observed
in higher mass systems. Chandra X-ray observations (when available) of the ETGs
with rotating H disks indicate that they are nearly void of hot gas. A
mixture of stellar mass loss and external accretion was likely the dominant
channel for the cool gas in NGC 4526 and NGC 4710. These ETGs show full
kinematic alignment between their stars and gas, and are fast rotators. The
H features within NGC 4191 (clumpy, potentially star-forming ring), NGC
4643 and NGC 5507 (extended structures) along with loosely overlapping stellar
and gas populations allow us to attribute external accretion to be the primary
formation channel of the cool gas in these systems.Comment: 16 pages, 7 figures, accepted for publication in MNRA
Buoyant AGN bubbles in the quasi-isothermal potential of NGC 1399
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
5\,kpc diameter to the northwest. We find that the amount of gas lifted by AGN
bubbles is comparable to that which would otherwise cool, demonstrating that
AGN driven outflow is effective in offsetting cooling in low-mass clusters. The
cluster cooling time scale is times longer than the dynamical time scale,
which is consistent with the lack of cold molecular gas at the cluster center.
The X-ray hydrostatic mass is consistent within 10\% with the total mass
derived from the optical data. The observed entropy profile rises linearly,
following a steeper slope than that observed at the centers of massive
clusters; gas shed by stars in NGC 1399 may be incorporated in the hot phase.
However, it is far-fetched for supernova-driven outflow to produce and maintain
the thermal distribution in NGC 1399 and it is in tension with the metal
content in the hot gas.Comment: 11 pages, 6 figures, Matches the version published in Ap
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