Open AccessProjection effects in X‐ray cores of cooling flow galaxy clusters
Author(s) -
Ettori Stefano
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05160.x
Subject(s) - physics , astrophysics , flatness (cosmology) , emissivity , galaxy cluster , cooling flow , galaxy , sky , cluster (spacecraft) , bin , projection (relational algebra) , radiative cooling , optics , universe , algorithm , computer science , programming language
Recent analyses of Newton‐XMM and Chandra data of the cores of X‐ray bright clusters of galaxies show that modelling with a multi‐phase gas in which several temperatures and densities are in equilibrium might not be appropriate. Instead, a single‐phase model seems able to reproduce properly the spectra collected in annuli from the central region. The measured single‐phase temperature profiles indicate a steep positive gradient in the central 100–200 kpc and the gas density shows a flat profile in the central few 10s of kpc. Given this observational evidence, we estimate the contribution to the projected‐on‐the‐sky rings from the cluster emissivity as function of the shell volume fraction sampled. We show that the observed projected X‐ray emission mimics the multi‐phase status of the plasma even though the input distribution is single‐phase. This geometrical projection affects (i) analyses of data where insufficient spatial resolution is accessible, (ii) the central bin when its dimension is comparable to the extension of any flatness in the central gas density profile.