| タイトル | A Giant Radio Halo in a Low-Mass SZ-Selected Galaxy Cluster: ACT-CL J0256.5+0006 |
| 著者（英） | Srianand, R.; Sifon, C.; Cress, C.; Marriage, T. A.; Hlozek, R.; Bond, J. R.; Lindner, R. R.; Hajian, A.; Menanteau, F.; Gupta, N.; Niemack, M. D.; Baker, A. J.; Knowles, K.; Hincks, A. D.; Wollack, Edward J.; Hughes, J. P.; Bharadwaj, V.; Moodley, K.; Hilton, M.; Reese, E. D.; Sievers, J.; Intema, H. T. |
| 著者所属（英） | NASA Goddard Space Flight Center |
| 発行日 | 2016-04-29 |
| 言語 | eng |
| 内容記述 | We present the detection of a giant radio halo (GRH) in the Sunyaev-Zel'dovich (SZ)-selected merging galaxy cluster ACT-CL J0256.5+0006 (zeta = 0.363), observed with the Giant Metrewave Radio Telescope at 325 MHz and 610 MHz. We find this cluster to host a faint (S(sub 610) = 5.6 +/- 1.4 mJy) radio halo with an angular extent of 2.6 arcmin, corresponding to 0.8 Mpc at the cluster redshift, qualifying it as a GRH. J0256 is one of the lowest-mass systems, M(sub 500,SZ) = (5.0 +/- 1.2) x 10(sup14) solar mass foud to host a GRH. We measure the GRH at lower significance at 325 MHz (S(sub 325) = 10.3 +/- 5.3 mJy), obtaining a spectral index measurement of alpha sup 610 sub 325 = 1.0(sup +0.7)(sub 0.9). This result is consistent with the mean spectral index of the population of typical radio halos, alpha = 1.2 +/- 0.2. Adopting the latter value, we determine a 1.4 GHz radio power of P(sub 1.4GHz) = (1.0 +/- 03) x 10(sup 24) W Hz(sup -1), placing this cluster within the scatter of known scaling relations. Various lines of evidence, including the ICM morphology, suggest that ACT-CL J0256.5+0006 is composed of two subclusters. We determine a merger mass ratio of 7:4, and a line-of-sight velocity difference of perpendicular = 1880 +/- 210 km s(sup -1). We construct a simple merger model of infer relevant time-scales in the merger. From its location on the P1.4GHz-L(sub x) scaling relation, we infer that we observe ACT-CL J0256.5+0006 just before first core crossing. |
| NASA分類 | Astrophysics |
| レポートNO | GSFC-E-DAA-TN32419 |
| 権利 | Copyright |
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