2010A&A...522A..34G


Query : 2010A&A...522A..34G

2010A&A...522A..34G - Astronomy and Astrophysics, volume 522, A34-34 (2010/11-1)

Apparent high metallicity in 3-4 keV galaxy clusters: the inverse iron-bias in action in the case of the merging cluster Abell 2028.

GASTALDELLO F., ETTORI S., BALESTRA I., BRIGHENTI F., BUOTE D.A., DE GRANDI S., GHIZZARDI S., GITTI M. and TOZZI P.

Abstract (from CDS):

Recent work based on a global measurement of the ICM properties finds evidence for an increase in the iron abundance in galaxy clusters with temperatures around 2-4 keV up to a value about 3 times higher than is typical of very hot clusters ZFe≃0.25Z. We have started a study of the metal distribution in nearby X-ray luminous poor galaxy clusters in the temperature range 3-4keV with measured high abundances. Our study aims at spatially resolving the metal content of the central regions of the ICM, in particular characterizing how our measurements are biased by the diagnostics adopted and by the possible multi-temperature nature of the projected observed spectra. We report here on a 42ks XMM-Newton observation of the first object in the sample, the cluster Abell 2028. We selected interesting regions of the ICM to analyze the spatially resolved structure of projected temperature and abundance, thereby producing two-dimensional maps. The XMM-Newton observation of the first object of the sample, the cluster Abell 2028, reveals the complex structure of the cluster over a scale of ∼300kpc, showing an interaction between two subclusters in cometary-like configurations. Cold fronts have been detected at the leading edges of the two substructures. The core of the main subcluster is likely hosting a cool corona. We show that a one-component fit for this region returns a biased high metallicity. The inverse iron bias is caused by the behavior of the fitting code in shaping the Fe-L complex. In the presence of a multi-temperature structure of the ICM, the best-fit metallicity turns out to be artificially higher when the projected spectrum is modeled with a single temperature component, while it is not related to the presence of both Fe-L and Fe-K emission lines in the spectrum. After accounting for the inverse iron bias, the overall abundance of the cluster is consistent with the one typical of hotter, more massive clusters. We caution against interpreting high abundances inferred when fitting a single thermal component to spectra derived from relatively large apertures in 3-4keV clusters, because the inverse iron bias can be present. Most of the inferences trying to relate high abundances in 3-4keV clusters to fundamental physical processes will probably have to be revised.

Abstract Copyright:

Journal keyword(s): galaxies: clusters: intracluster medium - galaxies: clusters: individual: Abell 2028 - galaxies: abundances - X-rays: galaxies: clusters

CDS comments: Fig.8 RX J15113.7+0713 is a probable misprint for RX J1513.7+0753.

Simbad objects: 16

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Number of rows : 16
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NAME Hya A LIN 09 18 05.6783347248 -12 05 43.634531472   14.38 14.8     ~ 964 1
2 ACO 1656 ClG 12 59 48.7 +27 58 50           ~ 4551 2
3 LEDA 140479 GiC 15 09 20.3 +07 38 19           ~ 5 0
4 2MASX J15092098+0738225 GiC 15 09 20.9486138736 +07 38 22.409839140           ~ 7 0
5 2MASX J15092819+0733247 BiC 15 09 28.1700589248 +07 33 24.496407468           ~ 20 0
6 ACO 2028 ClG 15 09 33 +07 31.6           ~ 70 0
7 RX J1509.5+0846 X 15 09 35.9 +08 46 05           ~ 4 0
8 SDSS J150936.33+084632.8 BiC 15 09 36.339 +08 46 32.85           ~ 4 0
9 ACO 2029 ClG 15 10 58.7 +05 45 42           ~ 896 0
10 ACO 2033 ClG 15 11 23.50 +06 19 08.4           ~ 91 0
11 ACO 2040 ClG 15 12 45.2 +07 25 48           ~ 138 1
12 1WGA J1513.0+0611 X 15 13 04.3 +06 11 55           ~ 1 0
13 RX J1513.7+0753 X 15 13 44.2 +07 53 59           ~ 3 0
14 ACO 2052 ClG 15 16 45.5 +07 00 01           ~ 703 1
15 ACO 2055 ClG 15 18 41.30 +06 12 39.6           ~ 101 0
16 ACO 2066 ClG 15 23 56 +01 02.4           ~ 16 0

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2022.09.30-18:51:52

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