34 research outputs found
XMM-Newton study of 0.012<z<0.024 groups. I: Overview of the IGM thermodynamics
We study the thermodynamic properties of the hot gas in a sample of groups in
the 0.012-0.024 redshift range, using XMM-Newton observations. We present
measurements of temperature, entropy, pressure and iron abundance.
Non-parametric fits are used to derive the mean properties of the sample and to
study dispersion in the values of entropy and pressure. The scaling of the
entropy at 0.2r500 matches well the results of Ponman et al. (2003). However,
compared to cool clusters, the groups in our sample reveal larger entropy at
inner radii and a substantially flatter slope in the entropy in the outskirts,
compared to both the prediction of pure gravitational heating and to
observations of clusters. This difference corresponds to the systematically
flatter group surface brightness profiles, reported previously. The scaled
pressure profiles can be well approximated with a Sersic model with n=4. We
find that groups exhibit a systematically larger dispersion in pressure,
compared to clusters of galaxies, while the dispersion in entropy is similar.Comment: 11 pages, MNRAS in press, the 25 page version with all 176 figures
included is at ftp://ftp.xray.mpe.mpg.de/people/alexis/2dxgs_astroph.ps.g
Cluster scaling and its redshift evolution from XMM-Newton
We put together the results of XMM-Newton observations of a number of
representative group and cluster samples at low and high redshifts. These
results confirm the entropy ramp as an explanation of the observed scaling
relations. We observe a mild evolution in the entropy of clusters. The observed
degree of evolution is consistent with expectations of the shock heating at a
fixed overdensity (500) with respect to the critical density in LCDM. The study
of the evolution in the pressure scaling imposes strong requirements in the
definition of the average temperature of the cluster. The scaling temperature
should be consistent to better than the 10% level. Once such a consistency is
achieved, no additional evolution in the pressure has been detected in addition
to the prediction of the shock heating in the LCDM Universe.Comment: 8 pages, Adv. in Space Research, in pres
The Two-dimensional XMM-Newton Group Survey: z<0.012 groups
We present the results of the 2-dimensional XMM-Newton Group Survey (2dXGS),
an archival study of nearby galaxy groups. In this paper we consider eleven
nearby systems (z<0.012) in Mulchaey et al. (2003), which span a broad range in
X-ray luminosity from 10^40 to 10^43 ergs/s. We measure the iron abundance and
temperature distribution in these systems and derive pressure and entropy maps.
We find statistically significant evidence for structure in the entropy and
pressure of the gas component of seven groups on the 10-20% level. The
XMM-Newton data for the three groups with best statistics also suggest patchy
metalicity distributions within the central 20--50 kpc of the brightest group
galaxy, probed with 2-10 kpc resolution. This provides insights into the
processes associated with thermalization of the stellar mass loss. Analysis of
the global properties of the groups reveals a subclass of X-ray faint groups,
which are characterized by both higher entropy and lower pressure. We suggest
that the merger history of the central elliptical is responsible for both the
source and the observed thermodynamical properties of the hot gas of the X-ray
faint groups.Comment: 18 pages, ApJ, 646, 143, 200
Influence of Social and Behavioural Characteristics of Users on Their Evaluation of Subjective Loudness and Acoustic Comfort in Shopping Malls
A large-scale subjective survey was conducted in six shopping malls in Harbin City, China, to determine the influence of social and behavioural characteristics of users on their evaluation of subjective loudness and acoustic comfort. The analysis of social characteristics shows that evaluation of subjective loudness is influenced by income and occupation, with correlation coefficients or contingency coefficients of 0.10 to 0.40 (p<0.05 or p<0.01). Meanwhile, evaluation of acoustic comfort evaluation is influenced by income, education level, and occupation, with correlation coefficients or contingency coefficients of 0.10 to 0.60 (p<0.05 or p<0.01). The effect of gender and age on evaluation of subjective loudness and acoustic comfort is statistically insignificant. The effects of occupation are mainly caused by the differences in income and education level, in which the effects of income are greater than that of education level. In terms of behavioural characteristics, evaluation of subjective loudness is influenced by the reason for visit, frequency of visit, and length of stay, with correlation coefficients or contingency coefficients of 0.10 to 0.40 (p<0.05 or p<0.01). Evaluation of acoustic comfort is influenced by the reason for visit to the site, the frequency of visit, length of stay, and also season of visit, with correlation coefficients of 0.10 to 0.30 (p<0.05 or p<0.01). In particular, users who are waiting for someone show lower evaluation of acoustic comfort, whereas users who go to shopping malls more than once a month show higher evaluation of acoustic comfort. On the contrary, the influence of the period of visit and the accompanying persons are found insignificant
Modified carbon-containing electrodes in stripping voltammetry of metals. Part II. Composite and microelectrodes
Desenvolvimento de membranas de Ăłxido de alumĂnio anĂłdico para ultramicrofiltração.
Raman amplifier with > 200 W average power based on a step-index fused silica fiber
More than 200 W output power from a Raman amplifier is presented. 1 W seed signal (wavelength 1125 nm) was generated in a Raman oscillator and fed into the Raman Amplifier subsequently. Conversion efficiency of 86% was achieved