The FMOS-COSMOS Survey of Star-forming Galaxies at z ~ 1.6. I. Hα-based Star Formation Rates and Dust Extinction

November 2013 • 2013ApJ...777L...8K

Authors • Kashino, D. • Silverman, J. D. • Rodighiero, G. • Renzini, A. • Arimoto, N. • Daddi, E. • Lilly, S. J. • Sanders, D. B. • Kartaltepe, J. • Zahid, H. J. • Nagao, T. • Sugiyama, N. • Capak, P. • Carollo, C. M. • Chu, J. • Hasinger, G. • Ilbert, O. • Kajisawa, M. • Kewley, L. J. • Koekemoer, A. M. • Kovač, K. • Le Fèvre, O. • Masters, D. • McCracken, H. J. • Onodera, M. • Scoville, N. • Strazzullo, V. • Symeonidis, M. • Taniguchi, Y.

Abstract • We present the first results from a near-IR spectroscopic survey of the COSMOS field, using the Fiber Multi-Object Spectrograph on the Subaru telescope, designed to characterize the star-forming galaxy population at 1.4 < z < 1.7. The high-resolution mode is implemented to detect Hα in emission between 1.6-1.8 μm with f _Hα >~ 4 × 10^-17 erg cm^-2 s^-1. Here, we specifically focus on 271 sBzK-selected galaxies that yield a Hα detection thus providing a redshift and emission line luminosity to establish the relation between star formation rate and stellar mass. With further J-band spectroscopy for 89 of these, the level of dust extinction is assessed by measuring the Balmer decrement using co-added spectra. We find that the extinction (0.6 <~ A _Hα <~ 2.5) rises with stellar mass and is elevated at high masses compared to low-redshift galaxies. Using this subset of the spectroscopic sample, we further find that the differential extinction between stellar and nebular emission E _star(B - V)/E _neb(B - V) is 0.7-0.8, dissimilar to that typically seen at low redshift. After correcting for extinction, we derive an Hα-based main sequence with a slope (0.81 ± 0.04) and normalization similar to previous studies at these redshifts.

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IPAC Authors
(alphabetical)

Elise Furlan

Associate Scientist

Daniel Masters

Assistant Scientist