2008/11/30 by L. A. M. Tasca, M. Huertas-Company, Daniel Rouan +18
Computer Science · Environmental Science · Mathematics · Physics and Astronomy · #Advanced Vision and Imaging #Artificial intelligence #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Biology #Computer science #Context (archaeology) #Cosmos (plant) #Field (mathematics) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Luminosity #Mathematics #Pattern recognition (psychology) #Photometric redshift #Physics #Redshift #Remote Sensing in Agriculture #Stellar, planetary, and galactic studies #Support vector machine #astro-ph
paper · pdf · doi:10.1051/0004-6361/200811255
accepted for publication in A&A, updated with referee comments, 12 pages, 10 figures
openalex publication_date 2009/01/01 · arxiv created 2009/02/24 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We quantify the effects of morphological k-correction at 1<z<2 by comparing morphologies measured in the K and I-bands in the COSMOS area. Ks-band data have indeed the advantage of probing old stellar populations for z<2, enabling a determination of galaxy morphological types unaffected by recent star formation. In paper I we presented a new non-parametric method to quantify morphologies of galaxies on seeing limited images based on support vector machines. Here we use this method to classify ∼50 000 Ks selected galaxies in the COSMOS area observed with WIRCam at CFHT. The obtained classification is used to investigate the redshift distributions and number counts per morphological type up to z∼2 and to compare to the results obtained with HST/ACS in the I-band on the same objects from other works. We associate to every galaxy with Ks<21.5 and z<2 a probability between 0 and 1 of being late-type or early-type. The classification is found to be reliable up to z∼2. The mean probability is p∼0.8. It decreases with redshift and with size, especially for the early-type population but remains above p∼0.7. The classification is globally in good agreement with the one obtained using HST/ACS for z<1. Above z∼1, the I-band classification tends to find less early-type galaxies than the Ks-band one by a factor ∼1.5 which might be a consequence of morphological k-correction effects. We argue therefore that studies based on I-band HST/ACS classifications at z>1 could be underestimating the elliptical population. [abridged]