FMOS near-IR spectroscopy of Herschel-selected galaxies: star formation rates, metallicity and dust attenuation at z ∼ 1
Clements, D. L.; Dunlop, J. S.; Buat, V.; Wang, L.; Bock, J.; Cooray, A.; Farrah, D.; Ibar, E.; Oliver, S. J.; Page, M. J.; Roseboom, I. G.; Symeonidis, M.; Conley, A.; Akiyama, M.; Iwamuro, F.; Magdis, G.; Schulz, B.; Zemcov, M.; Curtis-Lake, E.; Scott, Douglas; Bunker, A.; Mauch, T.; Marsden, G.; Chapin, E.; Takato, N.; Totani, T.; Kimura, M.; Sumiyoshi, M.; Dalton, G.; Bonfield, D.; Casey, C.; Ham, S. J.; Lewis, I.; Macaulay, E.; Maihara, T.; Moritani, Y.; Ohta, K.; Tamura, N.; Yabe, K.
United Kingdom, Japan, United States, France, Canada
Abstract
We investigate the properties (e.g. star formation rate, dust attenuation, stellar mass and metallicity) of a sample of infrared (IR) luminous galaxies at z ∼ 1 via near-IR spectroscopy with Subaru-FMOS. Our sample consists of Herschel SPIRE and Spitzer MIPS selected sources in the COSMOS field with photometric redshifts in the range of 0.7 < zphot < 1.8, which have been targeted in two pointings (0.5 deg2) with FMOS. We find a modest success rate for emission-line detections, with candidate Hα emission lines detected for 57 of 168 SPIRE sources (34 per cent). By stacking the near-IR spectra we directly measure the mean Balmer decrement for the Hα and Hβ lines, finding a value of <E(B - V)> = 0.51 ± 0.27 for <LIR> = 1012 L⊙ sources at <z> = 1.36. By comparing star formation rates estimated from the IR and from the dust-uncorrected Hα line we find a strong relationship between dust attenuation and star formation rate. This relation is broadly consistent with that previously seen in star-forming galaxies at z ∼ 0.1. Finally, we investigate the metallicity via the N2 ratio, finding that z ∼ 1 IR-selected sources are indistinguishable from the local mass-metallicity relation. We also find a strong correlation between dust attenuation and metallicity, with the most metal-rich IR sources experiencing the largest levels of dust attenuation.