Clustering of Star-forming Galaxies Near a Radio Galaxy at z = 5.2

We present HST ACS observations of the most distant radio galaxy known, TN J0924-2201 at z = 5.2. This radio galaxy has six spectroscopically confirmed Lya-emitting companion galaxies and appears to lie within an overdense region. The radio galaxy is marginally resolved in i sub(775) and z sub(850),...

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Bibliographic Details
Published in:	The Astrophysical journal 2006-01, Vol.637 (1), p.58-73
Main Authors:	Overzier, Roderik A, Miley, G. K, Bouwens, R. J, Cross, N. J. G, Zirm, A. W, Benítez, N, Blakeslee, J. P, Clampin, M, Demarco, R, Ford, H. C, Hartig, G. F, Illingworth, G. D, Martel, A. R, Röttgering, H. J. A, Venemans, B, Ardila, D. R, Bartko, F, Bradley, L. D, Broadhurst, T. J, Coe, D, Feldman, P. D, Franx, M, Golimowski, D. A, Goto, T, Gronwall, C, Holden, B, Homeier, N, Infante, L, Kimble, R. A, Krist, J. E, Mei, S, Menanteau, F, Meurer, G. R, Motta, V, Postman, M, Rosati, P, Sirianni, M, Sparks, W. B, Tran, H. D, Tsvetanov, Z. I, White, R. L, Zheng, W
Format:	Article
Language:	eng
Subjects:	Astronomy Earth, ocean, space Exact sciences and technology
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Summary:	We present HST ACS observations of the most distant radio galaxy known, TN J0924-2201 at z = 5.2. This radio galaxy has six spectroscopically confirmed Lya-emitting companion galaxies and appears to lie within an overdense region. The radio galaxy is marginally resolved in i sub(775) and z sub(850), showing continuum emission aligned with the radio axis, similar to what is observed for lower redshift radio galaxies. Both the half-light radius and the UV star formation rate are comparable to the typical values found for Lyman break galaxies at z 6 4-5. The Lya emitters are sub-L sub(*) galaxies, with deduced star formation rates of 1-10 M sub( )yr super(-1). One of the Lya emitters is only detected in Lya. Based on the star formation rate of 63 M sub( )yr super(-1) calculated from Lya, the lack of continuum emission could be explained if the galaxy is younger than 62 Myr and is producing its first stars. Observations in V sub(606)i sub(775)z sub(850) were used to identify additional Lyman break galaxies associated with this structure. In addition to the radio galaxy, there are 22 V sub(606) break (z 6 5) galaxies with z sub(850) < 26.5 (5 s), two of which are also in the spectroscopic sample. We compare the surface density of 62 arcmin super(-2) to that of similarly selected V sub(606) dropouts extracted from GOODS and the UDF parallel fields. We find evidence for an overdensity to very high confidence (>99%), based on a counts-in-cells analysis applied to the control field. The excess suggests that the V sub(606) break objects are associated with a forming cluster around the radio galaxy.
ISSN:	0004-637X 1538-4357