Vol. 534
In section 4. Extragalactic astronomy

GOODS-Herschel: A population of 24 μm dropout sources at z < 2

by G. E Magdis, D. Elbaz, M. Dickinson, H.S. Hwang, V. Charmandaris, et al., A&A 534, A15


From 100- and 160 μm Herschel data in the GOODS survey, the authors have discovered 21 infrared bright galaxies (U/LIRG) previously missed in the deepest 24μm surveys performed by Spitzer. They were missed in that band because their silicate absorption features at 18 μm and 9.7 μm are shifted into the 24 μm band for redshifts z~0.4 and 1.3, respectively. These can be dubbed 24 μm dropouts. The authors propose that with other color ratios involving Herschel bands, it is possible to select galaxies with a redshift around either 0.4 or 1.3. They show that the discovered dropouts have elevated specific star formation rates compared to main sequence galaxies at these redshifts and are likely to be compact starbursts with significant 9.7 μm silicate absorption features.