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The Las Campanas Infrared Survey – II. Photometric redshifts, comparison with models and clustering evolution

Firth, A. E. and Somerville, R. S. and McMahon, R. G. and Lahav, O. and Ellis, R. S. and Sabbey, C. N. and McCarthy, P. J. and Chen, H. -W and Marzke, R. O. and Wilson, J. and Abraham, R. G. and Beckett, M. G. and Carlberg, R. G. and Lewis, J. R. and Mackay, C. D. and Murphy, D. C. and Oemler, A. E. and Persson, S. E. (2002) The Las Campanas Infrared Survey – II. Photometric redshifts, comparison with models and clustering evolution. Monthly Notices of the Royal Astronomical Society, 332 (3). pp. 617-646. ISSN 0035-8711.

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The Las Campanas Infrared (LCIR) Survey, using the Cambridge Infra-Red Survey Instrument (CIRSI), reaches H∼21 over nearly 1 deg^2. In this paper we present results from 744 arcmin^2 centred on the Hubble Deep Field South for which UBVRI optical data are publicly available. Making conservative magnitude cuts to ensure spatial uniformity, we detect 3177 galaxies to H=20.0 in 744 arcmin^2 and a further 842 to H=20.5 in a deeper subregion of 407 arcmin^2. We compare the observed optical–infrared (IR) colour distributions with the predictions of semi-analytic hierarchical models and find reasonable agreement. We also determine photometric redshifts, finding a median redshift of ∼0.55. We compare the redshift distributions N(z) of E, Sbc, Scd and Im spectral types with models, showing that the observations are inconsistent with simple passive-evolution models while semi-analytic models provide a reasonable fit to the total N(z) but underestimate the number of z∼1 red spectral types relative to bluer spectral types. We also present N(z) for samples of extremely red objects (EROs) defined by optical–IR colours. We find that EROs with R-H>4 and H<20.5 have a median redshift z_m ∼ 1 while redder colour cuts have slightly higher z_m. In the magnitude range 19<H<20 we find that EROs with R-H>4 comprise ∼18 per cent of the observed galaxy population, while in semi-analytic models they contribute only ∼4 per cent. We also determine the angular correlation function w(θ) for magnitude, colour, spectral type and photometric redshift-selected subsamples of the data and use the photometric redshift distributions to derive the spatial clustering statistic ξ(r) as a function of spectral type and redshift out to z∼1.2. Parametrizing ξ(r) by ξ(rc,z)=[rc/r∗(z)]^(-1.8), where r_c is in comoving coordinates, we find that r∗(z) increases by a factor of 1.5–2 from z=0 to z∼1.2. We interpret this as a selection effect – the galaxies selected at z∼1.2 are intrinsically very luminous, about 1–1.5 mag brighter than L∗. When galaxies are selected by absolute magnitude, we find no evidence for evolution in r∗ over this redshift range. Extrapolated to z=0, we find r∗(z=0)∼6.5 h^(-1) Mpc for red galaxies and r∗(z=0)∼2–4 h^(-1) Mpc for blue galaxies. We also find that, while the angular clustering amplitude of EROs with R-H>4 or I-H>3 is up to four times that of the whole galaxy population, the spatial clustering length r∗(z=1) is ∼7.5–10.5 h^(-1) Mpc, which is only a factor of ∼1.7 times r∗(z=1) for R-H<4 and I-H<3 galaxies lying in a similar redshift and luminosity range. This difference is similar to that observed between red and blue galaxies at low redshifts.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ellis, R. S.0000-0001-7782-7071
Abraham, R. G.0000-0002-4542-921X
Additional Information:© 2002 RAS. Accepted 2001 December 20. Received 2001 December 20; in original form 2001 August 1. We would like to express our appreciation to the Goddard Space Flight Center group for obtaining, calibrating and making public the wide-field UBVRI images used in this paper, and to the creators of HYPERZ for releasing their excellent photometric redshift code to the astronomy community. Some HYPERZ software was also used in the construction of the passive and no-evolution models in this paper. We would also like to thank the very helpful staff at Las Campanas Observatory. The development and construction of the infrared camera, the Cambridge Infra-Red Survey Instrument (CIRSI), was made possible by a generous grant from the Raymond and Beverly Sackler Foundation. AEF is supported by an Isaac Newton Studentship, L. B. Wood Travelling scholarship, ORS award and Trinity College, Cambridge.
Funding AgencyGrant Number
Isaac Newton StudentshipUNSPECIFIED
L. B. Wood Travelling scholarshipUNSPECIFIED
Cambridge Trinity CollegeUNSPECIFIED
Subject Keywords:surveys; galaxies: distances and redshifts; galaxies: photometry; cosmology: observations; large-scale structure of Universe; infrared: galaxies
Issue or Number:3
Record Number:CaltechAUTHORS:20130305-114649668
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37309
Deposited By: Jason Perez
Deposited On:05 Mar 2013 21:52
Last Modified:09 Mar 2020 13:18

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