Open AccessThe discovery of a significant sample of massive galaxies at redshifts 5 < z < 6 in the UKIDSS Ultra Deep Survey early data release
Author(s) -
McLure R. J.,
Cirasuolo M.,
Dunlop J. S.,
Sekiguchi K.,
Almaini O.,
Foucaud S.,
Simpson C.,
Watson M. G.,
Hirst P.,
Page M. J.,
Smail I.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10864.x
Subject(s) - physics , astrophysics , galaxy , redshift , photometry (optics) , stellar mass , dark matter , astronomy , galaxy formation and evolution , stars , star formation
We have exploited the large area coverage of the combined UKIDSS Ultra Deep Survey (UDS) and Subaru/ XMM–Newton Deep Survey (SXDS) to search for bright Lyman‐break galaxies (LBGs) at z ≥ 5. Using the available optical + near‐infrared photometry to efficiently exclude low‐redshift contaminants, we identify nine z ≥ 5 LBG candidates brighter than z ′ AB = 25 within the 0.6‐deg 2 overlap region between the UDS early data release and the optical coverage of the SXDS. Accounting for selection incompleteness, we estimate the corresponding surface density of z ≥ 5 LBGs with z ′ AB ≤ 25 to be 0.005 ± 0.002 arcmin −2 . Modelling of the optical + near‐infrared photometry constrains the candidates' redshifts to lie in the range 5.1 < z < 5.9 , and provides estimates for their stellar masses. Although the stellar mass estimates are individually uncertain, a stacking analysis suggests that the typical stellar mass of the LBG candidates is ≳5 × 10 10 M ⊙ which, if confirmed, places them amongst the most massive galaxies currently known at z ≥ 5. It is found that Lambda cold dark matter structure formation can produce sufficient numbers of dark matter haloes at z ≥ 5 to accommodate our estimated number density of massive LBGs for plausible values of σ 8 and the ratio of stellar to dark matter. Moreover, it is found that recent galaxy formation models can also account for the existence of such massive galaxies at z ≥ 5. Finally, no evidence is found for the existence of LBGs with stellar masses in excess of ≃3 × 10 11 M ⊙ at this epoch, despite the large comoving volume surveyed.