Bibcode
Pović, M.; Huertas-Company, M.; Márquez, I.; Masegosa, J.; Aguerri, J. A. L.; Husillos, C.; Molino, A.; Cristóbal-Hornillos, D.
Bibliographical reference
Highlights of Astronomy, Volume 16, pp. 378-378
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2015
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Description
The Advanced Large Homogeneous Area Medium Band Redshift Astronomical
(ALHAMBRA) survey is a photometric survey designed to study
systematically cosmic evolution and cosmic variance (Moles et al. 2008).
It employs 20 continuous medium-band filters (3500 - 9700 Å), plus
JHK near-infrared (NIR) bands, which enable measurements of photometric
redshifts with good accuracy. ALHAMBRA covers > 4 deg2 in
eight discontinuous regions (~ 0.5 deg2 per region), of
theseseven fields overlap with other extragalactic, multiwavelength
surveys (DEEP2, SDSS, COSMOS, HDF-N, Groth, ELAIS-N1). We detect >
600.000 sources, reaching the depth of R(AB) ~ 25.0, and photometric
accuracy of 2-4% (Husillos et al., in prep.). Photometric redshifts are
measured using the Bayesian Photometric Redshift (BPZ) code
(Benítez et al. 2000), reaching one of the best accuracies up to
date of δz/z <= 1.2% (Molino et al., in prep.).
To deal with the morphological classification of galaxies in the
ALHAMBRA survey (Pović et al., in prep.), we used the galaxy
Support Vector Machine code (galSVM; Huertas-Company 2008, 2009), one of
the new non-parametric methods for morphological classification,
specially useful when dealing with low resolution and high-redshift
data. To test the accuracy of our morphological classification we used a
sample of 3000 local, visually classified galaxies (Nair & Abraham
2010), moving them to conditions typical of our ALHAMBRA data (taking
into account the background, redshift and magnitude distributions,
etc.), and measuring their morphology using galSVM. Finally, we measured
the morphology of ALHAMBRA galaxies, obtaining for each source seven
morphological parameters (two concentration indexes, asymmetry, Gini,
M20 moment of light, smoothness, and elongation), probability
if the source belongs to early- or late-type, and its error. Comparing
ALHAMBRA morph COSMOS/ACS morphology (obtained with the same method) we
expect to have qualitative separation in two main morphological types
for ~ 20.000 sources in 8 ALHAMBRA fields. For early-type galaxies we
expect to recover ~ 70% and 30-40% up to magnitudes 20.0 and 21.5,
respectively, having the contamination of late-types of < 7%. For
late-type galaxies, we expect to recover ~ 70%, 60 - 70%, and ~ 30% of
sources up to magnitudes 22.0, 22.5, and 23.0, respectively, having the
contamination of early-types of <= 10%. These data will be used to
study the evolution of active and non-active galaxies respect to
morphology and morphological properties of galaxies in groups and
clusters.