arXiv subjects

Monique Arnaud

Publications and source records attributed to Monique Arnaud.

21 records · Page 2Linked to original sources

arXiv2000

A Mosaic of the Coma Cluster of Galaxies with XMM-Newton

The Coma cluster of galaxies was observed with XMM-Newton in 12 partially overlapping pointings. We present here the resulting X-ray map in different energy bands and discuss the large scale structure of this cluster. Many point sources were found throughout the observed area, at least 11 of them are coincident with bright galaxies. We also give a hardness ratio map at the so far highest angular resolution obtained for a cluster of galaxies. In this map we found soft regions at the position of bright galaxies, little variation in the central 15 arcmin, but some harder regions north of the line NGC 4874 - NGC 4889.

astro-ph↗

arXiv1999

The Lx-T Relation and Intracluster Gas Fractions of X-ray Clusters

We re-examine the X-ray luminosity-temperature relation using a nearly homogeneous data set of 24 clusters selected for statistically accurate temperature measurements and absence of strong cooling flows. The data exhibit a remarkably tight power-law relation between bolometric luminosity and temperature with a slope 2.88 \pm 0.15. With reasonable assumptions regarding cluster structure, we infer an upper limit on fractional variations in the intracluster gas fraction <(δ\fgas/\fgas)^2)^1/2 \le 15%. Imaging data from the literature are employed to determine absolute values of fgas within spheres encompassing density contrast 500 and 200 with respect to the critical density. Comparing binding mass estimates based on the virial theorem (VT) and the hydrostatic, betamodel (BM), we find a temperature-dependent discrepancy in fgas between the two methods caused by sytematic variation of the outer slope parameter beta with temperature. There is evidence that cool clusters have a lower mean gas fraction that hot clusters, but it is not possible to assess the statistical significance of this effect in the present dataset. The temperature dependance of the ICM density structure, coupled with the increase of the gas fraction with T in the VT aproach, explains the steepening of the Lx-T relation. The small variation about the mean gas fraction within this majority sub-population of clusters presents an important constraint for theories of galaxy formation and supports arguments against an Einstein-deSitter universe based on the population mean gas fraction and primordial nucleosynthesis. The apparent trend of lower gas fractions and more extended atmospheres in low T systems are consistent with expectations of models incorporating the effects of galactic winds on the ICM. ABRIDGED

astro-ph↗

arXiv1999

Regularity in the X-ray surface brightness profiles of galaxy clusters and the M-T relation

We used archival ROSAT observations to investigate the X-ray surface brightness profiles of a sample of 26 clusters in the redshift range (0.04-0.06). For 15 of these clusters accurate temperature (kT>3.5 keV) were available from the literature. The scaled emission measure profiles look remarkably similar above ~0.2 times the virial radius r_V. On the other hand a large scatter is observed in the cluster core properties. We fitted a \betamodel (with and without excising the central part) to all the ROSAT profile to quantify the structural variations in the cluster population, unraveling a robust quadratic correlation between the core radius r_c and the slope parameter beta. We quantified the shape of each gas density profile by the variation with radius of the logarithmic slope, α_n. The bi-weight dispersion of α_n among the clusters is less than 20% for any given scaled radii above x=0.2. There is a clear minimum spread at x=0.3, which is related to the existence of a correlation between r_c and β. These ensemble properties are insensitive to the exact treatment of a possible central excess when fitting the profiles. On the other hand the scatter is decreased when the radii are scaled to r_V. The regularity we found in the gas profiles at x>0.2 supports the existence of an universal underlying dark matter profile. It suggests that non gravitational heating is negligible for clusters with temperature above ~3.5keV. The very large scatter observed in the core properties favor scenario where Cooling Flows are periodically erased by merger events. Our results are consistent with the classical scaling M-T relation. Accordingly the spread in the reduced mass profiles derived from the hydrostatic isothermal betamodel is small.

astro-ph↗