2009A&A...508.1269V


C.D.S. - SIMBAD4 rel 1.7 - 2021.02.26CET02:30:30

2009A&A...508.1269V - Astronomy and Astrophysics, volume 508, 1269-1273 (2009/12-4)

The discovery of diffuse steep spectrum sources in Abell 2256.

VAN WEEREN R.J., INTEMA H.T., OONK J.B.R., ROETTGERING H.J.A. and CLARKE T.E.

Abstract (from CDS):

Hierarchical galaxy formation models indicate that during their lifetime galaxy clusters undergo several mergers. An example of such a merging cluster is Abell 2256. Here we report on the discovery of three diffuse radio sources in the periphery of Abell 2256, using the Giant Metrewave Radio Telescope (GMRT). The aim of the observations was to search for diffuse ultra-steep spectrum radio sources within the galaxy cluster Abell 2256. We have carried out GMRT 325 MHz radio continuum observations of Abell 2256. V, R and I band images of the cluster were taken with the 4.2m William Herschel Telescope (WHT). We have discovered three diffuse elongated radio sources located about 1Mpc from the cluster center. Two are located to the west of the cluster center, and one to the southeast. The sources have a measured physical extent of 170, 140 and 240kpc, respectively. The two western sources are also visible in deep low-resolution 115-165MHz Westerbork Synthesis Radio Telescope (WSRT) images, although they are blended into a single source. For the combined emission of the blended source we find an extreme spectral index (α) of -2.05±0.14 between 140 and 351MHz. The extremely steep spectral index suggests these two sources are most likely the result of adiabatic compression of fossil radio plasma due to merger shocks. For the source to the southeast, we find that α←1.45 between 1369 and 325MHz. We did not find any clear optical counterparts to the radio sources in the WHT images. The discovery of the steep spectrum sources implies the existence of a population of faint diffuse radio sources in (merging) clusters with such steep spectra that they have gone unnoticed in higher frequency (>1GHz) observations. Simply considering the timescales related to the AGN activity, synchrotron losses, and the presence of shocks, we find that most massive clusters should possess similar sources. An exciting possibility therefore is that such sources will determine the general appearance of clusters in low-frequency high resolution radio maps as will be produced by for example LOFAR or LWA.

Abstract Copyright:

Journal keyword(s): radio continuum: general - galaxies: clusters: individual: Abell 2256 - large-scale structure of Universe

Nomenclature: Fig. 1: [RSM94] AA (Nos AG, AH, AI) added.

Simbad objects: 19

goto Full paper

goto View the reference in ADS

Number of rows : 19

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 3C 48 QSO 01 37 41.2995845985 +33 09 35.079126038   16.62 16.20     ~ 2563 2
2 ICRF J054236.1+495107 Sy1 05 42 36.13789843 +49 51 07.2337251   18.45 17.80 17.210   ~ 1299 1
3 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825108   17.51 17.25     ~ 3838 2
4 3C 295 Sy2 14 11 20.467 +52 12 09.52   22.34 20.80 18.54   ~ 908 5
5 [RSM94] S Rad 16 59 26.6 +78 41 15           ~ 5 0
6 [BLC2002] 56 GiC 16 59 30.8 +78 43 25           ~ 2 0
7 [RSM94] AH Rad 16 59 35 +78 42.7           ~ 2 0
8 2MASX J16594813+7842055 GiC 16 59 48.1615131543 +78 42 04.878352102           ~ 2 0
9 [RSM94] AG Rad 17 00 14 +78 42.0           ~ 2 0
10 2MASX J17002352+7842076 GiC 17 00 23.525 +78 42 07.63           ~ 4 0
11 [BF76] H Rad 17 02 31.5 +78 42 37           ~ 11 0
12 2MASX J17030269+7835549 GiC 17 03 02.692 +78 35 54.91           ~ 31 0
13 2MASS J17032933+7837548 GiC 17 03 29.3879463505 +78 37 54.943959241   17.02       ~ 25 0
14 2MASX J17033002+7839536 GiC 17 03 30.026 +78 39 53.65   17.57       ~ 30 0
15 [BF76] G Rad 17 03 43.2 +78 50 04           ~ 13 0
16 ACO 2256 ClG 17 03 43.5 +78 43 03           ~ 839 1
17 MCG+13-12-019 GiC 17 04 48.1036792107 +78 38 29.205715757   17       ~ 24 0
18 [BF76] F Rad 17 06 14.4 +78 39 04           ~ 8 0
19 [RSM94] AI Rad 17 08 07 +78 33.8           ~ 2 0

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2009A&A...508.1269V and select 'bookmark this link' or equivalent in the popup menu


2021.02.26-02:30:30

© Université de Strasbourg/CNRS

    • Contact