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Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - The LABOCA survey of the Extended Chandra Deep Field-South: a photometric redshift survey of submillimetre galaxies
AU - Wardlow, J. L.
AU - Smail, Ian
AU - Coppin, K. E. K.
AU - Alexander, D. M.
AU - Brandt, W. N.
AU - Danielson, A. L. R.
AU - Luo, B.
AU - Swinbank, A. M.
AU - Walter, F.
AU - Weiß, A.
AU - Xue, Y. Q.
AU - Zibetti, S.
AU - Bertoldi, F.
AU - Biggs, A. D.
AU - Chapman, S. C.
AU - Dannerbauer, H.
AU - Dunlop, J. S.
AU - Gawiser, E.
AU - Ivison, R. J.
AU - Knudsen, K. K.
AU - Kovács, A.
AU - Lacey, C. G.
AU - Menten, K. M.
AU - Padilla, N.
AU - Rix, H.-W.
AU - van der Werf, P. P.
PY - 2011/8/1
Y1 - 2011/8/1
N2 - We derive photometric redshifts from 17-band optical to mid-infrared photometry of 78 robust radio, 24-μm and Spitzer IRAC counterparts to 72 of the 126 submillimetre galaxies (SMGs) selected at 870 μm by LABOCA observations in the Extended Chandra Deep Field-South (ECDF-S). We test the photometric redshifts of the SMGs against the extensive archival spectroscopy in the ECDF-S. The median photometric redshift of identified SMGs is z= 2.2 ± 0.1, the standard deviation is σz= 0.9 and we identify 11 (˜15 per cent) high-redshift (z≥ 3) SMGs. A statistical analysis of sources in the error circles of unidentified SMGs identifies a population of possible counterparts with a redshift distribution peaking at z= 2.5 ± 0.2, which likely comprises ˜60 per cent of the unidentified SMGs. This confirms that the bulk of the undetected SMGs are coeval with those detected in the radio/mid-infrared. We conclude that at most ˜15 per cent of all the SMGs are below the flux limits of our IRAC observations and thus may lie at z≳ 3 and hence at most ˜30 per cent of all SMGs have z≳ 3. We estimate that the full S870 μm > 4 mJy SMG population has a median redshift of 2.5 ± 0.5. In contrast to previous suggestions, we find no significant correlation between submillimetre flux and redshift. The median stellar mass of the SMGs derived from spectral energy distribution fitting is (9.1 ± 0.5) × 1010 M⊙ although we caution that the uncertainty in the star formation histories results in a factor of ˜5 uncertainty in these stellar masses. Using a single temperature modified blackbody fit with β= 1.5, the median characteristic dust temperature of SMGs is 37.4 ± 1.4 K. The infrared luminosity function shows that SMGs at z= 2-3 typically have higher far-infrared luminosities and luminosity density than those at z= 1-2. This is mirrored in the evolution of the star formation rate density (SFRD) for SMGs which peaks at z˜ 2. The maximum contribution of bright SMGs to the global SFRD (˜5 per cent for SMGs with S870 μm≳ 4 mJy or ˜50 per cent extrapolated to SMGs with S870 μm > 1 mJy) also occurs at z˜ 2.
AB - We derive photometric redshifts from 17-band optical to mid-infrared photometry of 78 robust radio, 24-μm and Spitzer IRAC counterparts to 72 of the 126 submillimetre galaxies (SMGs) selected at 870 μm by LABOCA observations in the Extended Chandra Deep Field-South (ECDF-S). We test the photometric redshifts of the SMGs against the extensive archival spectroscopy in the ECDF-S. The median photometric redshift of identified SMGs is z= 2.2 ± 0.1, the standard deviation is σz= 0.9 and we identify 11 (˜15 per cent) high-redshift (z≥ 3) SMGs. A statistical analysis of sources in the error circles of unidentified SMGs identifies a population of possible counterparts with a redshift distribution peaking at z= 2.5 ± 0.2, which likely comprises ˜60 per cent of the unidentified SMGs. This confirms that the bulk of the undetected SMGs are coeval with those detected in the radio/mid-infrared. We conclude that at most ˜15 per cent of all the SMGs are below the flux limits of our IRAC observations and thus may lie at z≳ 3 and hence at most ˜30 per cent of all SMGs have z≳ 3. We estimate that the full S870 μm > 4 mJy SMG population has a median redshift of 2.5 ± 0.5. In contrast to previous suggestions, we find no significant correlation between submillimetre flux and redshift. The median stellar mass of the SMGs derived from spectral energy distribution fitting is (9.1 ± 0.5) × 1010 M⊙ although we caution that the uncertainty in the star formation histories results in a factor of ˜5 uncertainty in these stellar masses. Using a single temperature modified blackbody fit with β= 1.5, the median characteristic dust temperature of SMGs is 37.4 ± 1.4 K. The infrared luminosity function shows that SMGs at z= 2-3 typically have higher far-infrared luminosities and luminosity density than those at z= 1-2. This is mirrored in the evolution of the star formation rate density (SFRD) for SMGs which peaks at z˜ 2. The maximum contribution of bright SMGs to the global SFRD (˜5 per cent for SMGs with S870 μm≳ 4 mJy or ˜50 per cent extrapolated to SMGs with S870 μm > 1 mJy) also occurs at z˜ 2.
KW - galaxies: evolution
KW - galaxies: high-redshift
KW - galaxies: starburst
KW - submillimetre: galaxies
U2 - 10.1111/j.1365-2966.2011.18795.x
DO - 10.1111/j.1365-2966.2011.18795.x
M3 - Journal article
VL - 415
SP - 1479
EP - 1508
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 2
ER -