258 research outputs found
Non-thermal X-rays, a high abundance ridge and fossil bubbles in the core of the Perseus cluster of galaxies
Using a deep Chandra observation of the Perseus cluster of galaxies, we find
a high-abundance shell 250 arcsec (93 kpc) from the central nucleus. This ridge
lies at the edge of the Perseus radio mini-halo. In addition we identify two
Halpha filaments pointing towards this shell. We hypothesise that this ridge is
the edge of a fossil radio bubble, formed by entrained enriched material lifted
from the core of the cluster. There is a temperature jump outside the shell,
but the pressure is continuous indicating a cold front. A non-thermal component
is mapped over the core of the cluster with a morphology similar to the
mini-halo. Its total luminosity is 4.8x10^43 erg/s, extending in radius to ~75
kpc. Assuming the non-thermal emission is the result of inverse Compton
scattering of the CMB and infrared emission from NGC 1275, we map the magnetic
field over the core of the cluster.Comment: 8 pages, colour, accepted by MNRA
The X-ray luminous cluster underlying the bright radio-quiet quasar H1821+643
We present a Chandra observation of the only low redshift, z=0.299, galaxy
cluster to contain a highly luminous radio-quiet quasar, H1821+643. By
simulating the quasar PSF, we subtract the quasar contribution from the cluster
core and determine the physical properties of the cluster gas down to 3 arcsec
(15 kpc) from the point source. The temperature of the cluster gas decreases
from 9.0\pm0.5 keV down to 1.3\pm0.2 keV in the centre, with a short central
radiative cooling time of 1.0\pm0.1 Gyr, typical of a strong cool-core cluster.
The X-ray morphology in the central 100 kpc shows extended spurs of emission
from the core, a small radio cavity and a weak shock or cold front forming a
semi-circular edge at 15 arcsec radius. The quasar bolometric luminosity was
estimated to be 2 x 10^{47} erg per sec, requiring a mass accretion rate of 40
Msolar per yr, which corresponds to half the Eddington accretion rate. We
explore possible accretion mechanisms for this object and determine that Bondi
accretion, when boosted by Compton cooling of the accretion material, could
provide a significant source of the fuel for this outburst. We consider
H1821+643 in the context of a unified AGN accretion model and, by comparing
H1821+643 with a sample of galaxy clusters, we show that the quasar has not
significantly affected the large-scale cluster gas properties.Comment: 20 pages, 19 figures, accepted by MNRA
Mapping small-scale temperature and abundance structures in the core of the Perseus cluster
We report further results from a 191 ks Chandra observation of the core of
the Perseus cluster, Abell 426. The emission-weighted temperature and abundance
structure is mapped detail. There are temperature variations down to ~1 kpc in
the brightest regions. Globally, the strongest X-ray surface brightness
features appear to be caused by temperature changes. Density and temperature
changes conspire to give approximate azimuthal balance in pressure showing that
the gas is in hydrostatic equilibrium. Si, S, Ar, Ca, Fe and Ni abundance
profiles rise inward from about 100 kpc, peaking at about 30-40 kpc. Most of
these abundances drop inwards of the peak, but Ne shows a central peak, all of
which may be explained by resonance scattering. There is no evidence for a
widespread additional cooler temperature component in the cluster with a
temperature greater than a factor of two from the local temperature. There is
however evidence for a widespread hard component which may be nonthermal. The
temperature and abundance of gas in the cluster is observed to be correlated in
a manner similar to that found between clusters.Comment: ~20 pages, colour, accepted by MNRAS. Updates include a more
extensive discussion of the hard component, reference corrections, and a few
other minor changes. A version with good figure quality is at
http://www-xray.ast.cam.ac.uk/papers/perdetail
Extreme AGN Feedback and Cool Core Destruction in the X-ray Luminous Galaxy Cluster MACS J1931.8-2634
We report on a deep, multiwavelength study of the galaxy cluster MACS
J1931.8-2634 using Chandra X-ray, Subaru optical, and VLA 1.4 GHz radio data.
This cluster (z=0.352) harbors one of the most X-ray luminous cool cores yet
discovered, with an equivalent mass cooling rate within the central 50 kpc is
approximately 700 solar masses/yr. Unique features observed in the central core
of MACSJ1931.8-2634 hint to a wealth of past activity that has greatly
disrupted the original cool core. We observe a spiral of relatively cool,
dense, X-ray emitting gas connected to the cool core, as well as highly
elongated intracluster light (ICL) surrounding the cD galaxy. Extended radio
emission is observed surrounding the central AGN, elongated in the east-west
direction, spatially coincident with X-ray cavities. The power input required
to inflate these `bubbles' is estimated from both the X-ray and radio emission
to reside between 4 and 14e45 erg/s, putting it among the most powerful jets
ever observed. This combination of a powerful AGN outburst and bulk motion of
the cool core have resulted in two X-ray bright ridges to form to the north and
south of the central AGN at a distance of approximately 25 kpc. The northern
ridge has spectral characteristics typical of cool cores and is consistent with
being a remnant of the cool core after it was disrupted by the AGN and bulk
motions. It is also the site of H-alpha filaments and young stars. The X-ray
spectroscopic cooling rate associated with this ridge is approximately 165
solar masses/yr, which agrees with the estimate of the star formation rate from
broad-band optical imaging (170 solar masses/yr). MACS J1931.8-2634 appears to
harbor one of most profoundly disrupted low entropy cores observed in a
cluster, and offers new insights into the survivability of cool cores in the
context of hierarchical structure formation.Comment: 19 pages, 15 figures, 5 tables. Accepted by MNRAS for publication
September 30 201
The X-ray luminous cluster underlying the z = 1.04 quasar PKS1229-021
We present a 100 ks Chandra observation studying the extended X-ray emission
around the powerful z=1.04 quasar PKS1229-021. The diffuse cluster X-ray
emission can be traced out to ~15 arcsec (~120 kpc) radius and there is a drop
in the calculated hardness ratio inside the central 5 arcsec consistent with
the presence of a cool core. Radio observations of the quasar show a strong
core and a bright, one-sided jet leading to the SW hot spot and a second hot
spot visible on the counter-jet side. Although the wings of the quasar PSF
provided a significant contribution to the total X-ray flux at all radii where
the extended cluster emission was detected, we were able to accurately subtract
off the PSF emission using ChaRT and marx simulations. The resulting steep
cluster surface brightness profile for PKS1229-021 appears similar to the
profile for the FRII radio galaxy 3C444, which has a similarly rapid surface
brightness drop caused by a powerful shock surrounding the radio lobes (Croston
et al.). Using a model surface brightness profile based on 3C444, we estimated
the total cluster luminosity for PKS1229-021 to be L_X ~ 2 x 10^{44} erg/s. We
discuss the difficulty of detecting cool core clusters, which host bright X-ray
sources, in high redshift surveys.Comment: 10 pages, 9 figures, accepted by MNRA
The ArgoNeuT Detector in the NuMI Low-Energy beam line at Fermilab
The ArgoNeuT liquid argon time projection chamber has collected thousands of
neutrino and antineutrino events during an extended run period in the NuMI
beam-line at Fermilab. This paper focuses on the main aspects of the detector
layout and related technical features, including the cryogenic equipment, time
projection chamber, read-out electronics, and off-line data treatment. The
detector commissioning phase, physics run, and first neutrino event displays
are also reported. The characterization of the main working parameters of the
detector during data-taking, the ionization electron drift velocity and
lifetime in liquid argon, as obtained from through-going muon data complete the
present report.Comment: 43 pages, 27 figures, 5 tables - update referenc
Michael Gera v. County of Schuylkill
USDC for the Middle District of Pennsylvani
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