Open AccessLuminous early‐type field galaxies at z ∼ 0.4 – II . Star formation history and space density
Author(s) -
Willis J. P.,
Hewett P. C.,
Warren S. J.,
Lewis G. F.
Publication year - 2002
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 - 10.1046/j.1365-8711.2002.05970.x
Subject(s) - physics , astrophysics , star formation , galaxy , astronomy , luminosity function , redshift , luminosity , luminous infrared galaxy , galaxy formation and evolution
We present a combined photometric and spectroscopic analysis of the star formation history and space density of a sample of 485 luminous, M V − 5 log h < −20.5 , field early‐type galaxies at redshifts 0.3 ≲ z ≲ 0.6. The observed b J ori colours as a function of redshift, mean absorption‐line strengths and [O ii ]λ3727 emission properties are used to constrain the star formation history of the galaxies. The mean star formation history of the early‐type galaxy sample is consistent with an old ( z f > 1) , passively evolving luminosity‐weighted stellar population. 21 per cent of the sample possess detectable [O ii ]λ3727 emission consistent with a low level (≲1 M ⊙ yr −1 ) of on‐going star formation. Parametric and non‐parametric estimates of the space density of the sample are derived. The integrated luminosity density at z ≃ 0.4 , allowing only for passive luminosity evolution, is in excellent agreement with the local, (〈 z 〉= 0.1) , luminosity density of early‐type galaxies. Overall, the sample properties are consistent with a galaxy formation scenario in which the majority of luminous field early‐type galaxies formed at redshifts z > 1 and have largely evolved passively since the formation epoch.