Measuring star formation in high-z massive galaxies: a mid-infrared to submillimetre study of the GOODS NICMOS Survey sample
Abstract
We present measurements of the mean mid-infrared to submillimetre flux densities of massive (M★≳ 1011 M⊙) galaxies at redshifts 1.7 < z < 2.9, obtained by stacking positions of known objects taken from the GOODS NICMOS Survey (GNS) catalogue on maps at 24 ?m (Spitzer/MIPS); 70, 100 and 160 ?m (Herschel/PACS); 250, 350 and 500 ?m (BLAST); and 870 ?m (LABOCA). A modified blackbody spectrum fit to the stacked flux densities indicates a median [interquartile] star formation rate (SFR) of SFR = 63[48, 81] M⊙ yr-1. We note that not properly accounting for correlations between bands when fitting stacked data can significantly bias the result. The galaxies are divided into two groups, disc-like and spheroid-like, according to their Sérsic indices, n. We find evidence that most of the star formation is occurring in n≤ 2 (disc-like) galaxies, with median [interquartile] SFR = 122[100, 150] M⊙ yr-1, while there are indications that the n > 2 (spheroid-like) population may be forming stars at a median [interquartile] SFR = 14[9, 20] M⊙ yr-1, if at all. Finally, we show that star formation is a plausible mechanism for size evolution in this population as a whole, but find only marginal evidence that it is what drives the expansion of the spheroid-like galaxies.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 2012
- DOI:
- 10.1111/j.1365-2966.2012.20456.x
- arXiv:
- arXiv:1008.4359
- Bibcode:
- 2012MNRAS.421.2161V
- Keywords:
-
- galaxies: evolution;
- galaxies: high-redshift;
- infrared: galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- Accepted by MNRAS. 10 pages, 3 figures, 3 tables