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arXiv · 1312.4975

The colour distribution of galaxies at redshift five

A. B. Rogers·R. J. McLure·J. S. Dunlop·R. A. A. Bowler·E. F. Curtis-Lake·P. Dayal·S. M. Faber·H. C. Ferguson·S. L. Finkelstein·N. A. Grogin·N. P. Hathi·D. Kocevski·A. M. Koekemoer·P. Kurczynski
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Abstract

We present the results of a study investigating the rest-frame ultra-violet (UV) spectral slopes of redshift z~5 Lyman-break galaxies (LBGs). By combining deep Hubble Space Telescope imaging of the CANDELS and HUDF fields with ground-based imaging from the UKIDSS Ultra Deep Survey (UDS), we have produced a large sample of z~5 LBGs spanning an unprecedented factor of >100 in UV luminosity. Based on this sample we find a clear colour-magnitude relation (CMR) at z~5, such that the rest-frame UV slopes (beta) of brighter galaxies are notably redder than their fainter counterparts. We determine that the z~5 CMR is well described by a linear relationship of the form: d beta = (-0.12 +/- 0.02) d Muv, with no clear evidence for a change in CMR slope at faint magnitudes (i.e. Muv > -18.9). Using the results of detailed simulations we are able, for the first time, to infer the intrinsic (i.e. free from noise) variation of galaxy colours around the CMR at z~5. We find significant (12 sigma) evidence for intrinsic colour variation in the sample as a whole. Our results also demonstrate that the width of the intrinsic UV slope distribution of z~5 galaxies increases from Delta(beta)=0.1 at Muv=-18 to Delta(beta)=0.4 at Muv=-21. We suggest that the increasing width of the intrinsic galaxy colour distribution and the CMR itself are both plausibly explained by a luminosity independent lower limit of beta=-2.1, combined with an increase in the fraction of red galaxies in brighter UV-luminosity bins.

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A. B. Rogers, R. J. McLure, J. S. Dunlop, R. A. A. Bowler, E. F. Curtis-Lake, P. Dayal, S. M. Faber, H. C. Ferguson, S. L. Finkelstein, N. A. Grogin, N. P. Hathi, D. Kocevski, A. M. Koekemoer, P. Kurczynski. 2014-03-24. The colour distribution of galaxies at redshift five. https://doi.org/10.1093/mnras%2Fstu558

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