IRAC photometric analysis and the mid-IR photometric properties of Lyman-break galaxies |
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| Authors: | G E Magdis D Rigopoulou J-S Huang G G Fazio S P Willner M L N Ashby |
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| Institution: | Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH;Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA |
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| Abstract: | We present photometric analysis of deep mid-infrared (mid-IR) observations obtained by Spitzer /IRAC covering the fields Q1422+2309, Q2233+1341, DSF2237a,b, HDFN, SSA22a,b and B20902+34, giving the number counts and the depths for each field. In a sample of 751 Lyman-break galaxies (LBGs) lying in those fields, 443, 448, 137 and 152 are identified at 3.6-, 4.5-, 5.8-, 8.0-μm IRAC bands, respectively, expanding their spectral energy distribution to rest-near-IR and revealing that LBGs display a variety of colours. Their rest-near-IR properties are rather inhomogeneous, ranging from those that are bright in IRAC bands and exhibit R ]?3.6] > 1.5 colours to those that are faint or not detected at all in IRAC bands with R ]?3.6] < 1.5 colours and these two groups of LBGs are investigated. We compare the mid-IR colours of the LBGs with the colours of star-forming galaxies and we find that LBGs have colours consistent with star-forming galaxies at z ～ 3 . The properties of the LBGs detected in the 8-μm IRAC band (rest-frame K band) are examined separately, showing that they exhibit redder R ]?3.6] colours than the rest of the population and that although in general, a multiwavelength study is needed to reach more secure results, IRAC 8-μm band can be used as a diagnostic tool, to separate high z , luminous AGN-dominated objects from normal star-forming galaxies at z ～ 3 . |
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| Keywords: | galaxies: evolution galaxies: high redshift galaxies: statistics cosmology: observations infrared: galaxies |
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