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Published April 2012 | Published
Journal Article Open

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_* ≳ 10^(11) 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 inline imagem (Spitzer/MIPS); 70, 100 and 160 inline imagem (Herschel/PACS); 250, 350 and 500 inline imagem (BLAST); and 870 inline imagem (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.

Additional Information

© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS. Accepted 2011 December 25. Received 2011 December 25; in original form 2011 July 23. Article first published online: 10 Feb 2012. The authors would like to extend a big thanks to the LESS team for providing the 870-μm map, and to David Frayer for the Spitzer 70-μm map used in the first version of this paper. We would also like to thank Ian Smail, Kimberly Scott and Ivana Damjanov for constructive comments. Finally, we would like to thank Hervé Aussel for his helpful advice. We acknowledge the support of NASA through grant numbers NAG5-12785, NAG5-13301 and NNGO-6GI11G, the NSF Office of Polar Programmes, the Canadian Space Agency, the Natural Sciences and Engineering Research Council (NSERC) of Canada, and the UK Science and Technology Facilities Council (STFC). This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX) under programme numbers 078.F-9028(A), 079.F-9500(A), 080.A-3023(A) and 081.F- 9500(A). APEX is a collaboration between the Max-Planck-Institut fur Radioastronomie, the European Southern Observatory and the Onsala Space Observatory.

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August 22, 2023
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