2011A&A...526A..79E

Query : 2011A&A...526A..79E

2011A&A...526A..79E - Astronomy and Astrophysics, volume 526A, 79-79 (2011/2-1)

The cool-core bias in X-ray galaxy cluster samples. I. Method and application to HIFLUGCS.

ECKERT D., MOLENDI S. and PALTANI S.

Abstract (from CDS):

When selecting flux-limited cluster samples, the detection efficiency of X-ray instruments is not the same for centrally-peaked and flat objects, which introduces a bias in flux-limited cluster samples. We quantify this effect in the case of a well-known cluster sample, HIFLUGCS. We simulate a population of X-ray clusters with various surface-brightness profiles, and use the instrumental characteristics of the ROSAT All-Sky Survey (RASS) to select flux-limited samples similar to the HIFLUGCS sample and predict the expected bias. For comparison, we also estimate observationally the bias in the HIFLUGCS sample using XMM-Newton and ROSAT data. We find that the selection of X-ray cluster samples is significantly biased (∼29%) in favor of the peaked, cool-core (CC) objects, with respect to non-cool-core (NCC) systems. Interestingly, we find that the bias affects the low-mass, nearby objects (groups, poor clusters) much more than the more luminous objects (i.e massive clusters). We also note a moderate increase of the bias for the more distant systems. Observationally, we propose to select the objects according to their flux in a well-defined physical range excluding the cores, 0.2r500-r500, to get rid of the bias. From the fluxes in this range, we reject 13 clusters out of the 64 in the HIFLUGCS sample, none of which appears to be NCC. As a result, we estimate that less than half (35-37%) of the galaxy clusters in the local Universe are strong CC. In the paradigm where the CC objects trace relaxed clusters as opposed to unrelaxed, merging objects, this implies that to the present day the majority of the objects are not in a relaxed state. From this result, we estimate a rate of heating events of ∼1/3Gyr–1 per dark-matter halo.

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Journal keyword(s): galaxies: clusters: general - galaxies: clusters: intracluster medium - X-rays: galaxies: clusters

Simbad objects: 69

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Number of rows : 69
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 ACO 85 ClG 00 41 36.21 -09 19 30.4           ~ 909 0
2 ACO 119 ClG 00 56 08.57 -01 12 00.8           ~ 555 2
3 ACO 133 ClG 01 02 41.5 -21 52 53           ~ 368 1
4 ZwCl 0120+3300 ClG 01 23 36.9 +33 15 03           ~ 78 0
5 NGC 507 BiC 01 23 39.950 +33 15 22.22   13.0       ~ 440 3
6 ACO 262 ClG 01 52 50.4 +36 08 46           ~ 699 1
7 ACO 400 ClG 02 57 37.4 +06 00 45           ~ 399 3
8 ACO 399 ClG 02 57 56.4 +13 00 59           ~ 396 0
9 ACO 401 ClG 02 58 56.9 +13 34 56           ~ 566 0
10 ACO 3112 ClG 03 17 52.4 -44 14 35           ~ 311 1
11 NGC 1399 BiC 03 38 29.083 -35 27 02.67 11.05 9.74 9.59 8.12   ~ 1570 1
12 ACO S 373 ClG 03 38 29.4 -35 27 08           ~ 1827 0
13 ZwCl 0335+0956 ClG 03 38 35.3 +09 57 54           ~ 383 1
14 NGC 1404 GiP 03 38 51.917 -35 35 39.81 11.53 10.69 10.00 9.03   ~ 751 1
15 2MASX J03411752+1523477 BiC 03 41 17.5329189192 +15 23 47.567775336   17.5       ~ 44 1
16 ACO 3158 ClG 03 42 39.6 -53 37 50           ~ 304 0
17 ACO 478 ClG 04 13 20.7 +10 28 35           ~ 502 0
18 NGC 1550 BiC 04 19 37.9450450152 +02 24 35.918168940   14.0       ~ 176 1
19 ClG 0422-09 ClG 04 25 51.02 -08 33 38.5           ~ 91 0
20 ACO 3266 ClG 04 31 11.9 -61 24 23           ~ 410 0
21 ACO 496 ClG 04 33 38.8 -13 15 59           ~ 694 2
22 ACO 3376 ClG 06 01 25.000 -39 59 51.00           ~ 305 0
23 ACO 3391 ClG 06 26 15.4 -53 40 52           ~ 202 1
24 ACO 3395 ClG 06 27 31.1 -54 23 58           ~ 209 0
25 ACO 576 ClG 07 21 24.1 +55 44 20           ~ 297 1
26 ACO 754 ClG 09 09 08.4 -09 39 58           ~ 666 1
27 NAME Hya A LIN 09 18 05.66848602 -12 05 43.8060823   14.38 14.8     ~ 1012 1
28 NAME Hydra I Cluster ClG 10 36 36.0 -27 31 04           ~ 840 1
29 ACO 1367 ClG 11 44 44.6 +19 41 59           ~ 1076 1
30 MKW 3 ClG 11 48 29 -03 10.7     14.88     ~ 52 1
31 NAME NGC 4073 Group GrG 12 04 44.08 +01 48 40.9     13.53     ~ 280 0
32 ZwCl 1215+0400 ClG 12 17 43.62 +03 38 51.5           ~ 153 0
33 NAME Virgo Cluster ClG 12 26 32.1 +12 43 24           ~ 6645 0
34 NGC 4636 LIN 12 42 49.8333280080 +02 41 15.951929028   12.62 11.84     ~ 1117 1
35 ACO 3526 ClG 12 48 51.8 -41 18 21           ~ 1068 2
36 ACO 1644 ClG 12 57 11.6 -17 24 34           ~ 366 1
37 ACO 1650 ClG 12 58 42.0 -01 45 45           ~ 304 0
38 ACO 1651 ClG 12 59 22.43 -04 11 47.1           ~ 290 0
39 ACO 1656 ClG 12 59 44.40 +27 54 44.9           ~ 4803 2
40 NGC 5044 BiC 13 15 23.9607836592 -16 23 07.547751744   11.9   10.74   ~ 501 0
41 ACO 1736 ClG 13 26 52.1 -27 06 33           ~ 249 2
42 ACO 3558 ClG 13 27 54.8 -31 29 32           ~ 442 2
43 ACO 3562 ClG 13 33 31.8 -31 40 23           ~ 314 1
44 ACO 3571 ClG 13 47 28.9 -32 51 57           ~ 284 2
45 ACO 1795 ClG 13 48 50.48 +26 35 07.4           ~ 1267 0
46 ACO 3581 ClG 14 07 29.8 -27 01 04           ~ 184 3
47 BAX 220.1796+03.4530 ClG 14 40 34.37 +03 29 49.7     14.31     ~ 119 0
48 ClG J1504-0248 ClG 15 04 07.4 -02 48 15           ~ 175 0
49 ACO 2029 ClG 15 10 56.2 +05 44 42           ~ 943 0
50 ACO 2052 ClG 15 16 41.64 +07 01 45.5           ~ 730 1
51 ACT-CL J1521.8+0742 ClG 15 21 55.14 +07 41 27.2     15.13     ~ 311 0
52 ACO 2065 ClG 15 22 29.3 +27 42 22           ~ 374 0
53 ACO 2063 ClG 15 23 01.8 +08 38 22           ~ 397 2
54 ACO 2142 ClG 15 58 14.38 +27 12 57.8           ~ 768 0
55 ACO 2147 ClG 16 02 11.96 +15 55 11.5           ~ 403 0
56 ACO 2163 ClG 16 15 46.1 -06 08 50           ~ 563 0
57 ACO 2199 ClG 16 28 43.31 +39 34 07.6           ~ 1171 1
58 ACO 2204 ClG 16 32 45.7 +05 34 43           ~ 436 0
59 ACO 2244 ClG 17 02 40.33 +34 02 58.7           ~ 281 0
60 ACO 2256 ClG 17 03 09.4 +78 39 36           ~ 885 1
61 ACO 2255 ClG 17 12 50.04 +64 03 10.6           ~ 568 0
62 ACO 3667 ClG 20 12 33.68 -56 50 26.3           ~ 627 1
63 ACO S 1101 ClG 23 13 58.5 -42 43 39           ~ 258 1
64 ACO 2589 ClG 23 24 00.5 +16 49 29           ~ 316 1
65 ACO 2597 ClG 23 25 19.70 -12 07 27.7           ~ 539 0
66 ACO 2634 ClG 23 38 18.4 +27 01 37           ~ 503 2
67 ACO 2657 ClG 23 44 51.0 +09 08 40           ~ 269 3
68 ACO 4038 ClG 23 47 31.1 -28 12 10           ~ 335 3
69 ACO 4059 ClG 23 57 02.2 -34 45 58           ~ 380 1

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