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A Giant Radio Halo in a Low-Mass Sz-selected Galaxy Cluster: ACT-CLJ0256.5+0006We present the detection of a giant radio halo (GRH) in the Sunyaev-Zel'dovich (SZ)- selected merging galaxy cluster ACT-CL J0256.5+ 0006 (z = 0.363), observed with the Giant Metrewave Radio Telescope at 325 and 610 MHz. We find this cluster to host a faint (S610 = 5.6 +/- 1.4mJy) 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, M500, SZ = (5.0 +/- 1.2) × 10(exp14) M, found to host a GRH. We measure the GRH at lower significance at 325 MHz (S325 = 10.3 +/- 5.3mJy), obtaining a spectral index measurement of α610 325 = 1.0+ 0.7 − 0.9. This result is consistent with the mean spectral index of the population of typical radio haloes, alpha = 1.2 +/- 0.2. Adopting the latter value, we determine a 1.4 GHz radio power of P1.4 GHz = (1.0 +/- 0.3) × 10(exp 24)W/Hz, placing this cluster within the scatter of known scaling relations. Various lines of evidence, including the intracluster medium 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 v⊥ = 1880 +/- 210 km/s. We construct a simple merger model to infer relevant time-scales in the merger. From its location on the P1.4GHz-LX scaling relation, we infer that we observe ACT-CL J0256.5+ 0006 just before first core crossing.
Document ID
20170002524
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Knowles, Kendra
(KwaZulu-Natal Univ. Durban, South Africa)
Intema, H. T.
(National Radio Astronomy Observatory Socorro, NM, United States)
Baker, A. J.
(Rutgers - The State Univ. Piscataway, NJ, United States)
Bharadwaj, V.
(KwaZulu-Natal Univ. Durban, South Africa)
Bond, J. R.
(Toronto Univ. Ontario, Canada)
Cress, C.
(Centre for High Performance Computing (CHPC) Cape Town, South Africa)
Gupta, N.
(Inter-University Centre for Astronomy and Astrophysics (IUCAA) Pune, India)
Hajian, A.
(Toronto Univ. Ontario, Canada)
Hilton, M.
(KwaZulu-Natal Univ. Durban, South Africa)
Hincks, A. D.
(British Columbia Univ. Vancouver, British Columbia, Canada)
Hlozek, R.
(Princeton Univ. Princeton, NJ, United States)
Hughes, J. P.
(Rutgers - The State Univ. Piscataway, NJ, United States)
Lindner, R. R.
(Wisconsin-Madison Univ. Madison, WI, United States)
Marriage, T. A.
(Johns Hopkins Univ. Baltimore, MD, United States)
Menanteau, F.
(Illinois Univ. Urbana-Champaign, IL, United States)
Moodley, K.
(KwaZulu-Natal Univ. Durban, South Africa)
Niemack, M. D.
(Cornell Univ. Ithaca, NY, United States)
Reese, E. D.
(Moorpark Coll. CA, United States)
Sievers, J.
(KwaZulu-Natal Univ. Durban, South Africa)
Sifon, C.
(Leiden Univ. Netherlands)
Srianand, R.
(Inter-University Centre for Astronomy and Astrophysics (IUCAA) Pune, India)
Wollack, Edward J.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
March 23, 2017
Publication Date
May 19, 2016
Publication Information
Publication: Monthly Notices of the Royal Astronomical Society
Publisher: Monthly Notices of the Royal Astronomical Society
Volume: 459
Issue: 4
ISSN: 0035-8711
e-ISSN: 1365-8711
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN40455
Distribution Limits
Public
Copyright
Other

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