Open AccessNear‐infrared properties of i ‐drop galaxies in the Hubble Ultra Deep Field
Author(s) -
Stanway Elizabeth R.,
McMahon Richard G.,
Bunker Andrew J.
Publication year - 2005
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.1365-2966.2005.08977.x
Subject(s) - physics , galaxy , astrophysics , redshift , photometry (optics) , hubble ultra deep field , astronomy , hubble space telescope , advanced camera for surveys , infrared , star formation , wide field camera 3 , luminous infrared galaxy , hubble deep field , infrared telescope , photometric redshift , stars
We analyse near‐infrared Hubble Space Telescope ( HST )/Near‐Infrared Camera and Multi‐Object Spectrometer F 110 W ( J ) and F 160 W ( H ) band photometry of a sample of 27 i ′‐drop candidate z ≃ 6 galaxies in the central region of the HST /Advanced Camera for Surveys Ultra Deep Field . The infrared colours of the 20 objects not affected by near neighbours are consistent with a high‐redshift interpretation. This suggests that the low‐redshift contamination of this i ′‐drop sample is smaller than that observed at brighter magnitudes, where values of 10–40 per cent have been reported. The J – H colours are consistent with a slope flat in f ν ( f λ ∝λ −2 ) , as would be expected for an unreddened starburst. However, there is evidence for a marginally bluer spectral slope ( f λ ∝λ −2.2 ) , which is perhaps indicative of an extremely young starburst (∼10 Myr old) or a top heavy initial mass function and little dust. The low levels of contamination, median photometric redshift of z ∼ 6.0 and blue spectral slope, inferred using the near‐infrared data, support the validity of the assumptions in our earlier work in estimating the star formation rates, and that the majority of the i ‐drop candidates galaxies lie at z ∼ 6 .