Searching for large-scale structures around high-redshift radio galaxies with Herschel

Autor: Rigby, E. E., Hatch, N. A., Röttgering, H. J. A., Sibthorpe, B., Chiang, Y. K., Overzier, R., Herbonnet, R., Borgani, S., Clements, D. L., Dannerbauer, H., De Breuck, C., De Lucia, G., Kurk, J., Maschietto, F., Miley, G., Saro, A., Seymour, N., Venemans, B.
Rok vydání: 2013
Předmět:
Druh dokumentu: Working Paper
DOI: 10.1093/mnras/stt2019
Popis: This paper presents the first results of a far-infrared search for protocluster-associated galaxy overdensities using the SPIRE instrument on-board the {\it Herschel} Space Observatory. Large ($\sim$400 arcmin$^{2}$) fields surrounding 26 powerful high-redshift radio galaxies ($2.0 < z < 4.1$; $L_{\rm 500 MHz} > 10^{28.5}$ WHz$^{-1}$) are mapped at 250, 350 and 500\mic to give a unique wide-field sample. On average the fields have a higher than expected, compared to blank fields, surface density of 500\mic sources within 6 comoving Mpc of the radio galaxy. The analysis is then restricted to potential protocluster members only, which are identified using a far-infrared colour selection; this reveals significant overdensities of galaxies in 2 fields, neither of which are previously known protoclusters. The probability of finding 2 overdensities of this size by chance, given the number of fields observed is $5 \times 10^{-4}$. Overdensities here exist around radio galaxies with $L_{\rm 500 MHz} \gtrsim 10^{29}$ WHz$^{-1}$ and $z < 3$. The radial extent of the average far-infrared overdensity is found to be $\sim$6 comoving Mpc. Comparison with predictions from numerical simulations shows that the overdensities are consistent with having masses $> 10^{14}$Msolar. However, the large uncertainty in the redshift estimation means that it is possible that these far-infrared overdensities consist of several structures across the redshift range searched.
Comment: 13 pages, 9 figures; Accepted for publication in MNRAS
Databáze: arXiv
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