870 research outputs found
Chandra observations of Abell 2199
We present results from an analysis of two Chandra observations of the rich,
nearby galaxy cluster Abell 2199. We find evidence (having corrected for
projection effects) for radial gradients in temperature and metallicity in the
X-ray emitting gas: the temperature drops from kT~4.2 keV at R=200 kpc to 1.6
keV within R=5 kpc of the centre. The metallicity rises from ~0.3 solar at
R=200 kpc to ~0.7 solar at R=30 kpc before dropping to 0.3 solar within the
central 5 kpc. We find evidence for structure in the surface brightness
distribution associated with the central radio source 3C338. No evidence is
found for the gas having a large spread in temperature at any particular
location despite the cooling time being short (<10**9yr) within the central ~15
kpc. Heating and mass cooling rates are calculated for various assumptions
about the state of the gas.Comment: 10 pages, 12 figures. Accepted by MNRAS. Minor changes following
referee's comment
FARMER-TO-CONSUMER DIRECT MARKETING: SALES AND ADVERTISING ASPECTS OF NEW JERSEY OPERATIONS
This article provides insights into the sales and advertising operations and characteristics of direct marketing enterprises in New Jersey. Sales data are analyzed with respect to the number of acres planted, related products, products sold that were grown by marketers, and organic produce. The advertising aspects explored are dollar amount spent on advertising and methods of advertising.Marketing,
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
XMM-Newton observations of the BL Lac MS 0737+7441
We report on the XMM-Newton observations of the BL Lac object MS 0737.9+7441
during the performance verification phase. A simple power-law fit provides an
adequate description of the integrated spectrum in the 0.2-10 keV energy band.
The photon index is slightly steeper in the EPIC pn data with 2.38+-0.01
compared to the EPIC MOS data (2.28+-0.01). The difference is most probably due
to the present uncertainties in the calibration of the EPIC MOS and EPIC pn
data sets. We report evidence for intrinsic absorption in the distant BL Lac
above the Galactic column N_H,Gal=3.2*10^20 cm^-2 which is N_H,fit(z=0.315)=
(2.70+-0.20)*10^20cm^-2 in the EPIC pn data and N_H,fit(z=0.315)=
(3.25+-0.25)*10^20cm^-2 in the EPIC MOS data assuming neutral gas and solar
abundances. The flux variations are found to be of the order of 10 %.Comment: 4 pages, 4 Figures, accepted for publication in the special A&A
Letters issue for XMM-Newto
A Hot Helium Plasma in the Galactic Center Region
Recent X-ray observations by the space mission Chandra confirmed the
astonishing evidence for a diffuse, hot, thermal plasma at a temperature of 9.
K (8 keV) found by previous surveys to extend over a few hundred parsecs
in the Galactic Centre region. This plasma coexists with the usual components
of the interstellar medium such as cold molecular clouds and a soft (~0.8 keV)
component produced by supernova remnants, and its origin remains uncertain.
First, simple calculations using a mean sound speed for a hydrogen-dominated
plasma have suggested that it should not be gravitationally bound, and thus
requires a huge energy source to heat it in less than the escape time. Second,
an astrophysical mechanism must be found to generate such a high temperature.
No known source has been identified to fulfill both requirements. Here we
address the energetics problem and show that the hot component could actually
be a gravitationally confined helium plasma. We illustrate the new prospects
this opens by discussing the origin of this gas, and by suggesting possible
heating mechanisms.Comment: 9 pages, accepted for publication in APJ
Cold Feedback in Cooling-Flow Galaxy Clusters
We put forward an alternative view to the Bondi-driven feedback between
heating and cooling of the intra-cluster medium (ICM) in cooling flow galaxies
and clusters. We adopt the popular view that the heating is due to an active
galactic nucleus (AGN), i.e. a central black hole accreting mass and launching
jets and/or winds. We propose that the feedback occurs with the entire cool
inner region (5-30 kpc). A moderate cooling flow does exist here, and
non-linear over-dense blobs of gas cool fast and are removed from the ICM
before experiencing the next major AGN heating event. Some of these blobs may
not accrete on the central black hole, but may form stars and cold molecular
clouds. We discuss the conditions under which the dense blobs may cool to low
temperatures and feed the black hole.Comment: 6 pages, no figures, to appear in the Proceedings of "Heating vs.
Cooling in Galaxies and Clusters of Galaxies", August 2006, Garching
(Germany
USP compendial methods for analysis of heparin: chromatographic determination of molecular weight distributions for heparin sodium
Heparin is a polysaccharide product isolated from glycosaminoglycans of porcine mucosa (or occasionally other tissues and species). It is a linear non-uniform polymer consisting of alternating glucosamine and uronic acid monosaccharide residues and is highly sulfated. Heparin sodium drug product (HP) used in medicine consists of chains with molecular weight (MW) ranging from under 5,000 to over 50,000. Although HP has been used as an injectable antithrombotic medicine for more than 70 years, many aspects of its structure and purity, including its MW, have not been specified by public standards until recent years. In 2008, a number of HP lots associated with severe adverse effects, including fatalities, were found to have been contaminated with oversulfated chondroitin sulfate. This incident led to thorough revision of compendial standards worldwide. In the USA, the Food and Drug Administration (FDA) encouraged the inclusion of enhanced standards for purity and identity in the relevant monographs of the United States Pharmacopeia (USP) including acceptance criteria for MW distribution
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
Improved constraints on dark energy from Chandra X-ray observations of the largest relaxed galaxy clusters
We present constraints on the mean matter density, Omega_m, dark energy
density, Omega_de, and the dark energy equation of state parameter, w, using
Chandra measurements of the X-ray gas mass fraction (fgas) in 42 hot (kT>5keV),
X-ray luminous, dynamically relaxed galaxy clusters spanning the redshift range
0.05<z<1.1. Using only the fgas data for the 6 lowest redshift clusters at
z<0.15, for which dark energy has a negligible effect on the measurements, we
measure Omega_m=0.28+-0.06 (68% confidence, using standard priors on the Hubble
Constant, H_0, and mean baryon density, Omega_bh^2). Analyzing the data for all
42 clusters, employing only weak priors on H_0 and Omega_bh^2, we obtain a
similar result on Omega_m and detect the effects of dark energy on the
distances to the clusters at ~99.99% confidence, with Omega_de=0.86+-0.21 for a
non-flat LCDM model. The detection of dark energy is comparable in significance
to recent SNIa studies and represents strong, independent evidence for cosmic
acceleration. Systematic scatter remains undetected in the fgas data, despite a
weighted mean statistical scatter in the distance measurements of only ~5%. For
a flat cosmology with constant w, we measure Omega_m=0.28+-0.06 and
w=-1.14+-0.31. Combining the fgas data with independent constraints from CMB
and SNIa studies removes the need for priors on Omega_bh^2 and H_0 and leads to
tighter constraints: Omega_m=0.253+-0.021 and w=-0.98+-0.07 for the same
constant-w model. More general analyses in which we relax the assumption of
flatness and/or allow evolution in w remain consistent with the cosmological
constant paradigm. Our analysis includes conservative allowances for systematic
uncertainties. The small systematic scatter and tight constraints bode well for
future dark energy studies using the fgas method. (Abridged)Comment: Published in MNRAS. 20 pages, 11 figures. The data and analysis code
(in the form of a patch to CosmoMC) are now available at
http://www.stanford.edu/~drapetti/fgas_module
- …