2006MNRAS.371..852K

Query : 2006MNRAS.371..852K

2006MNRAS.371..852K - Mon. Not. R. Astron. Soc., 371, 852-866 (2006/September-2)

A search for distant radio galaxies from SUMSS and NVSS - III. Radio spectral energy distributions and the z-α correlation.

KLAMER I.J., EKERS R.D., BRYANT J.J., HUNSTEAD R.W., SADLER E.M. and DE BREUCK C.

Abstract (from CDS):

This is the third in a series of papers that present observations and results for a sample of 76 ultrasteep-spectrum radio sources designed to find galaxies at high redshift. Here we present multifrequency radio observations, from the Australia Telescope Compact Array, for a subset of 37 galaxies from the sample. Matched resolution observations at 2.3, 4.8 and 6.2 GHz are presented for all galaxies, with the z < 2 galaxies additionally observed at 8.6 and 18 GHz. New angular size constraints are reported for 19 sources based on high-resolution 4.8- and 6.2-GHz observations. Functional forms for the rest-frame spectral energy distributions are derived: 89 per cent of the sample is well characterized by a single power law, whilst the remaining 11 per cent show some flattening towards higher frequencies: not one source shows any evidence for high-frequency steepening. We discuss the implications of this result in light of the empirical correlation between redshift and spectral index seen in flux-limited samples of radio galaxies. Finally, a new physical mechanism to explain the redshift - spectral index correlation is posited: extremely steep-spectrum radio galaxies in the local universe usually reside at the centres of rich galaxy clusters. We argue that if a higher fractions of radio galaxies, as a function of redshift, are located in environments with densities similar to nearby rich clusters, then this could be a natural interpretation for the correlation. We briefly outline our plans to pursue this line of investigation.

Abstract Copyright: 2006 The Authors. Journal compilation © 2006 RAS

Journal keyword(s): surveys - galaxies: active - radio continuum: galaxies - radio continuum: general

Simbad objects: 48

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Number of rows : 48
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 ICRF J001259.9-395426 BLL 00 12 59.9097885288 -39 54 26.056833444   18.33   18.05   ~ 84 1
2 PKS J0013-3225 Rad 00 13 39.54 -32 24 47.8           ~ 4 1
3 NVSS J002131-342225 Rad 00 21 31.32 -34 22 28.6           ~ 4 1
4 NVSS J002219-360728 Rad 00 22 19.5 -36 07 30           ~ 3 1
5 NVSS J002402-325253 rG 00 24 02.34 -32 52 56.9           ~ 8 1
6 NVSS J002627-323653 Rad 00 26 27.96 -32 36 48.9           ~ 3 1
7 QSO B0104-408 Bla 01 06 45.10796439 -40 34 19.9603733   18.60 19.0 19.25   ~ 136 1
8 NVSS J011606-331241 Rad 01 16 06.80 -33 12 43.2           ~ 6 1
9 NVSS J012904-324815 rG 01 29 04.267 -32 48 13.17   17.770   16.057   ~ 5 1
10 PMN J0152-3340 Rad 01 52 32.400 -33 39 52.15           ~ 10 1
11 NVSS J015324-334117 Rad 01 53 24.6 -33 41 14           ~ 4 1
12 ICRF J015537.0-404842 Sy2 01 55 37.05930363 -40 48 42.3570102   18.5       ~ 53 1
13 GLEAM J015544-330633 QSO 01 55 44.6109374208 -33 06 34.809221484           ~ 6 1
14 NVSS J021308-322338 Rad 02 13 08.10 -32 23 39.4           ~ 7 1
15 QSO B0220-349 Bla 02 22 56.40164366 -34 41 28.7302247   21.39   21.10   ~ 79 1
16 NVSS J030639-330432 Rad 03 06 39.509 -33 04 28.91           ~ 9 1
17 4C 41.17 rG 06 50 52.098 +41 30 30.53           ~ 349 1
18 QSO B1921-293 BLL 19 24 51.05595254 -29 14 30.1210248   18.71 18.21 15.07   ~ 918 1
19 ICRF J193925.0-634245 Sy2 19 39 25.0245304992 -63 42 45.640373400   18.87 18.37 17.64   ~ 1332 2
20 QSO B1954-388 Bla 19 57 59.81927491 -38 45 06.3558881   18.47 17.07 16.73   ~ 239 1
21 NVSS J202026-372823 Rad 20 20 26.81 -37 28 21.8           ~ 5 1
22 NVSS J202140-373942 Rad 20 21 40.39 -37 39 37.5           ~ 4 1
23 GLEAM J202945-344810 QSO 20 29 45.8129533224 -34 48 15.590190456           ~ 7 1
24 NVSS J204420-334948 Rad 20 44 20.73 -33 49 48.8           ~ 2 1
25 QSO B2058-425 QSO 21 01 59.1137330928 -42 19 16.165821072   17.56 17.20     ~ 54 1
26 NVSS J213510-333703 rG 21 35 10.47 -33 37 01.3           ~ 9 1
27 PKS 2211-388 rG 22 14 38.56966 -38 35 45.0098           ~ 34 1
28 NVSS J225719-343954 Rad 22 57 19.56 -34 39 53.9           ~ 8 1
29 QSO B2255-2814 Bla 22 58 05.96287687 -27 58 21.2567572   17.34 16.77 17.20   ~ 397 1
30 NVSS J230035-363410 Rad 23 00 35.87 -36 34 10.9           ~ 4 1
31 NVSS J230123-364656 rG 23 01 23.34377 -36 46 59.9274           ~ 7 1
32 NVSS J230527-360534 Rad 23 05 27.64 -36 05 31.9           ~ 4 1
33 NVSS J230954-365653 Rad 23 09 54.2 -36 56 52           ~ 2 1
34 NVSS J231144-362215 rG 23 11 44.97 -36 22 15.1           ~ 7 1
35 NVSS J231317-352133 Rad 23 13 17.4 -35 21 29           ~ 2 1
36 NVSS J231338-362708 Rad 23 13 38.73 -36 27 08.4           ~ 4 1
37 NVSS J231402-372925 Rad 23 14 02.42 -37 29 28.1           ~ 7 1
38 NVSS J231727-352606 Rad 23 17 27.30 -35 26 03.2           ~ 9 1
39 NVSS J232058-365157 Rad 23 20 58.16 -36 51 57.4           ~ 3 1
40 NVSS J232100-360223 Rad 23 21 00.61 -36 02 23.1           ~ 7 1
41 NVSS J232219-355816 Rad 23 22 19.68 -35 58 16.9           ~ 1 0
42 NVSS J232408-353547 Rad 23 24 08.5995063144 -35 35 44.837578608           ~ 3 1
43 NVSS J232602-350321 Rad 23 26 02.6 -35 03 27           ~ 4 1
44 NVSS J232651-370909 rG 23 26 51.39 -37 09 11.3           ~ 7 1
45 NVSS J234137-342230 Rad 23 41 37.20 -34 22 32.2           ~ 2 1
46 PKS 2339-353 rG 23 41 45.85196 -35 06 22.1963           ~ 22 1
47 GLEAM J234904-362448 QSO 23 49 04.3343922528 -36 24 52.735397472           ~ 6 1
48 NVSS J235137-362632 Rad 23 51 37.77 -36 26 33.4           ~ 2 1

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