2013A&A...560A..64H

Query : 2013A&A...560A..64H

2013A&A...560A..64H - Astronomy and Astrophysics, volume 560A64-64 (2013/12-1)

Probing the cosmic-ray content of galaxy clusters by stacking Fermi-LAT count maps.

HUBER B., TCHERNIN C., ECKERT D., FARNIER C., MANALAYSAY A., STRAUMANN U. and WALTER R.

Abstract (from CDS):

Radio observations have shown that galaxy clusters are giant reservoirs of cosmic rays (CR). Although a gamma-ray signal from the cluster volume is expected to arise through interactions of CR protons with the ambient plasma, a confirming observation is still missing. We searched for a cumulative gamma-ray emission in the direction of galaxy clusters by analysing a collection of stacked Fermi-LAT count maps. Additionally, we investigated possible systematic differences in the emission between cool-core and non-cool-core cluster populations. Making use of a sample of 53 clusters selected from the HIFLUGCS catalog, we do not detect a significant signal from the stacked sample. The upper limit on the average flux per cluster derived for the total stacked sample is at the level of a few 10–11ph/cm2/s at a 95% confidence level in the 1-300GeV band, assuming power-law spectra with photon indices 2.0, 2.4, 2.8, and 3.2. Separate stacking of the cool-core and non-cool-core clusters in the sample lead to similar values of around 5x10–11ph/cm2/s and 2x10–11ph/cm2/s, respectively. Under the assumption that decaying π0, produced in collisions between CRs and the ambient thermal gas, are responsible for gamma-ray emission, we set upper limits on the average CR content in galaxy clusters. For the entire cluster population, our upper limit on the gamma-ray flux translates into an upper limit on the average CR-to-thermal energy ratio of 4.6% for a photon index of 2.4, although it is possible for individual systems to exceed this limit. Our 95% upper limits are at the level expected from numerical simulations, which most likely suggests that the injection of CR at cosmological shocks is less efficient than previously assumed.

Abstract Copyright: ∼

Journal keyword(s): galaxies: clusters: general - gamma rays: galaxies: clusters - methods: data analysis - astroparticle physics - rays cosmic

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 - 2026 		#notes
1 ACO 85 ClG 00 41 36.21 -09 19 30.4           ~ 974 0
2 ACO 119 ClG 00 56 08.57 -01 12 00.8           ~ 577 2
3 ACO 133 ClG 01 02 41.5 -21 52 53           ~ 391 1
4 ACO 2877 ClG 01 09 49.3 -45 54 02           ~ 160 2
5 NGC 499 LIN 01 23 11.4954761664 +33 27 36.656232300   13.0 12.3     ~ 181 0
6 NGC 507 rG 01 23 39.950 +33 15 22.22   13.0       ~ 459 1
7 ACO 262 ClG 01 52 50.4 +36 08 46           ~ 727 1
8 ACO 400 ClG 02 57 37.4 +06 00 45           ~ 408 3
9 ACO 399 ClG 02 57 56.4 +13 00 59           ~ 420 0
10 ACO 401 ClG 02 58 50.3 +13 34 07           ~ 592 0
11 ACO 3112 ClG 03 17 52.9 -44 15 06           ~ 329 1
12 ACO 426 ClG 03 19 47.6 +41 30 54           ~ 2508 1
13 NGC 1275 Bla 03 19 48.1599902040 +41 30 42.108850836   13.10 12.48 11.09   ~ 4243 3
14 ACO S 373 ClG 03 38 29.4 -35 27 08           ~ 2029 0
15 ACO 3158 ClG 03 43 07.5 -53 38 09           ~ 327 0
16 ACO 478 ClG 04 13 24.8 +10 27 52           ~ 522 0
17 NGC 1550 BiC 04 19 37.9450450152 +02 24 35.918168940   14.0       ~ 183 1
18 ClG 0422-09 ClG 04 25 51.02 -08 33 38.5           ~ 97 0
19 ACO 3266 ClG 04 31 26.4 -61 25 17           ~ 447 0
20 ACO 496 ClG 04 33 40.8 -13 14 34           ~ 728 2
21 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 4971 0
22 ACO 548 ClG 05 47 01.7 -25 36 59           B8 209 2
23 ACO 3376 ClG 06 01 25.000 -39 59 51.00           ~ 334 0
24 ACO 3391 ClG 06 26 15.4 -53 40 52           ~ 222 1
25 ACO 3395 ClG 06 27 31.1 -54 23 58           ~ 229 0
26 ACO 576 ClG 07 21 24.1 +55 44 20           ~ 312 1
27 Z 262-19 BiC 07 40 58.2309667896 +55 25 37.870473828   14.2       ~ 52 1
28 ACO 780 ClG 09 18 30 -12 15.7           ~ 469 0
29 NAME Hydra I Cluster ClG 10 36 36.0 -27 31 04           ~ 905 1
30 ACO 1367 ClG 11 44 44.6 +19 41 59           ~ 1127 1
31 ACO 1413 ClG 11 55 12.87 +23 23 46.9           ~ 456 0
32 NAME NGC 4073 Group GrG 12 04 44.08 +01 48 40.9     13.53     ~ 292 0
33 ZwCl 1215+0400 ClG 12 17 43.62 +03 38 51.5           ~ 169 0
34 M 49 Sy2 12 29 46.8 +08 00 01   13.21 12.17     ~ 2174 2
35 NGC 4636 LIN 12 42 49.8333280080 +02 41 15.951929028   12.62 11.84     ~ 1156 1
36 BAX 193.5900-29.0100 ClG 12 54 22.1 -29 00 46           ~ 45 0
37 BAX 193.6700-29.2254 ClG 12 54 40.6 -29 13 44           ~ 76 0
38 ACO 3530 ClG 12 55 36.0 -30 20 49           ~ 109 0
39 ACO 1644 ClG 12 57 11.6 -17 24 34           ~ 391 1
40 ACO 3532 ClG 12 57 19.2 -30 22 13           ~ 185 2
41 ACO 1650 ClG 12 58 42.0 -01 45 45           ~ 325 0
42 ACO 1651 ClG 12 59 27.3 -04 10 49           ~ 307 0
43 ACO 1656 ClG 12 59 44.40 +27 54 44.9           ~ 5141 2
44 ACO 1689 ClG 13 11 29.5 -01 20 28           ~ 1178 0
45 NGC 5044 BiC 13 15 23.9607836592 -16 23 07.547751744   11.9   10.74   ~ 531 0
46 ACO 1736 ClG 13 26 52.1 -27 06 33           ~ 268 2
47 ACO 3558 ClG 13 28 03.2 -31 31 35           ~ 476 2
48 ACO 3560 ClG 13 32 23.7 -33 08 21           ~ 145 1
49 ACO 3562 ClG 13 33 31.8 -31 40 23           ~ 337 1
50 ACO 1775 ClG 13 41 50.60 +26 21 10.6           ~ 324 0
51 ACO 3571 ClG 13 47 32.4 -32 50 12           ~ 308 2
52 ACO 1795 ClG 13 48 47.4 +26 34 55           ~ 1330 0
53 ACO 1800 ClG 13 49 27.19 +28 04 44.6           ~ 127 0
54 ACO 3581 ClG 14 07 29.8 -27 01 04           ~ 197 3
55 ACO 1914 ClG 14 25 57.4 +37 49 54           ~ 338 0
56 ACO 2065 ClG 15 22 22.7 +27 44 20           ~ 398 0
57 ACO 2142 ClG 15 58 26.5 +27 13 52           ~ 825 0
58 ACO 2151 ClG 16 05 15.0 +17 44 55           ~ 594 3
59 ACO 2199 ClG 16 28 34.5 +39 32 26           ~ 1206 1
60 ACO 2244 ClG 17 02 40.33 +34 02 58.7           ~ 301 0
61 ACO 2256 ClG 17 03 37.5 +78 37 23           ~ 928 1
62 BAX 258.1082-23.3759 ClG 17 12 26.3 -23 21 38           ~ 303 0
63 ACO 2255 ClG 17 12 56.0 +64 04 06           ~ 605 0
64 ACO 3921 ClG 22 49 59.0 -64 25 48           ~ 165 1
65 BAX 349.3187+18.7197 ClG 23 17 11.184 +18 41 48.87           ~ 97 0
66 ACO 2589 ClG 23 24 00.5 +16 49 29           ~ 327 1
67 ACO 2597 ClG 23 25 19.70 -12 07 27.7           ~ 572 0
68 ACO 2634 ClG 23 38 18.4 +27 01 37           ~ 515 2
69 ACO 2657 ClG 23 44 51.0 +09 08 40           ~ 280 3

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