Morphological Evolution from z ~ 2 in the COSMOS Field from Ks-Band Imaging
Abstract
Morphology is the most accessible tracer of galaxies physical structure, although its interpretation in the framework of galaxy evolution still remains a problem. Its quantification at high redshift requires deep high angular resolution imaging, the reason why space data (HST) are normally employed. At z > 1, the HST visible cameras probe however the UV flux, dominated by the emission of young stars, which could bias the estimated morphologies towards late-type systems. In this paper we quantify the effects of this 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 in the rest-frame for z < 2, enabling a determination of galaxy morphological types unaffected by recent star formation. We employ a new non-parametric method based on SVM to classify∼50,000 Ks selected galaxies in the COSMOS area observed with WIRCam at CFHT. We use a 10-dimensional volume, including 5 morphological parameters, and other characteristics of galaxies such as luminosity and redshift. 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.
- Publication:
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Highlights of Spanish Astrophysics V
- Pub Date:
- 2010
- DOI:
- 10.1007/978-3-642-11250-8_50
- Bibcode:
- 2010ASSP...14..301H
- Keywords:
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- Physics