Open AccessSegregated optical‐‐near‐infrared colour distributions of Medium Deep Survey galaxies
Author(s) -
Ferreras I.,
Cayón L.,
MartínezGonzález E.,
Benítez N.
Publication year - 1999
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.1365-8711.1999.02308.x
Subject(s) - physics , astrophysics , galaxy , redshift , magnitude (astronomy) , limiting magnitude , star formation , population , absolute magnitude , stellar population , astronomy , infrared , apparent magnitude , photometric redshift , redshift survey , limiting , stars , demography , sociology , mechanical engineering , engineering
We present a K survey of 29 fields covering approximately 90 arcmin 2 from the Medium Deep Survey (MDS) catalogue down to a completeness magnitude of K=18.0 (limiting magnitude K=19.0). The morphology obtained by the MDS team using high‐resolution images from HST/WFPC2 along with our near‐infrared (NIR) observations allows colour‐‐magnitude and colour‐‐colour analysis that agrees in general with spectral evolution models, especially if a reasonable range of metallicities for the simple stellar populations used (0.2 < Z/Z ⊙ < 2.5) is considered. However, a significant population of spheroids was found, which appears bluer than expected, confirming previous observations. This blueness might possibly signal the existence of non‐negligible star formation in ellipticals and bulges at medium redshift. A number counts calculation for different morphological types shows that discs become the dominant population at faint magnitudes. The median redshift of the sample is z ∼ 0.2, from a photometric redshift estimation using V‐K and I‐K . A search for Extremely Red Objects (EROs) in the survey field was also performed, with no detection of objects having I‐K>4.5, setting an upper limit to the number density of EROs d n EROs /d Ο < 0.011 arcmin ‐2 (K ≤ 18.0).