Bibcode
Hempel, A.; Cristóbal-Hornillos, D.; Prieto, M.; Trujillo, I.; Balcells, M.; López-Sanjuan, C.; Abreu, D.; Eliche-Moral, M. C.; Domínguez-Palmero, L.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 414, Issue 3, pp. 2246-2264.
Advertised on:
7
2011
Citations
5
Refereed citations
4
Description
We present a new catalogue of EROs from the Groth Strip and study the
relation between their morphology and mass. With a selection criterion
F814W-Ks≥ 4 and Ks≤ 21.0 we find 102 EROs,
over a survey area of 155 arcmin2, leading to a surface
density of 0.66 arcmin-2. The photometric data include U, B,
F606W, F814W, J, Ks bands. Morphologies are based on a by eye
classification and we distinguish between three basic classes: compact
objects, targets with a disc and/or a bulge component and irregular or
merger candidates. An additional group consists of the few objects which
could not be classified.
The majority of our targets has either a very compact morphology (34
± 6 per cent), or show more or less distinct disc components (43
± 6 per cent). 14 ± 4 per cent are merger or irregulars
and seven objects (approximately 9 per cent) could not be classified.
We also study the dependence of structural parameters (effective radius:
reff, Sérsic index: n) on morphological appearance. As
expected, EROs that are either compact or show a distinct bulge
component have smaller median effective radii (1.22 ± 0.14 kpc
and 3.31 ± 0.53 kpc) than disc dominated (5.50 ± 0.51 kpc)
or possible irregular galaxies or merger candidates (4.92 ± 0.14
kpc). More importantly, the Sérsic index changes from 2.30
± 0.34 and 3.24 ± 0.55, to 1.03 ± 0.24 and 1.54
± 0.40, respectively.
As found in previous studies, most the EROs in our sample have redshifts
between z= 1 and 2; however, compact EROs in our sample are found at
redshifts as low as z= 0.4 and as high as z= 2.8; the latter qualify as
well as distant red galaxies (DRGs). Disc-like EROs are also found up to
z= 2.8; however, those with a bulge-disc structure are only seen at z
< 1.5.
For each of these EROs we determined the stellar mass and mean
population age by fitting synthetic Bruzual (2007) spectra to the
photometric spectral energy distributions, via χ2
minimization. Mass estimates were obtained by assuming an exponentially
declining star formation rate with a wide set of parameters, e.g. decay
time, redshift of last star formation, metallicity and optical depth.
Total stellar masses for our sample are in the range 9.1 <
log(M/M&sun;) < 11.6. We cannot detect significant
differences between the stellar mass distribution of the morphological
classes. EROs with masses of log(M/M&sun;) > 11.0
dominantly show compact morphologies, but also include a significant
number of sources with a disc morphology.
Related projects
Traces of Galaxy Formation: Stellar populations, Dynamics and Morphology
We are a large, diverse, and very active research group aiming to provide a comprehensive picture for the formation of galaxies in the Universe. Rooted in detailed stellar population analysis, we are constantly exploring and developing new tools and ideas to understand how galaxies came to be what we now observe.
Ignacio
Martín Navarro