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Published September 2015 | Published + Submitted
Journal Article Open

The FMOS-COSMOS Survey of Star-forming Galaxies at z ~ 1.6. III. Survey Design, Performance, and Sample Characteristics


We present a spectroscopic survey of galaxies in the COSMOS field using the Fiber Multi-object Spectrograph (FMOS), a near-infrared instrument on the Subaru Telescope. Our survey is specifically designed to detect the Hα emission line that falls within the H-band (1.6–1.8 μm) spectroscopic window from star-forming galaxies with 1.4 < z < 1.7 and M_(stellar) ≳ 10^(10) M⊙. With the high multiplex capability of FMOS, it is now feasible to construct samples of over 1000 galaxies having spectroscopic redshifts at epochs that were previously challenging. The high-resolution mode (R ~ 2600) effectively separates Hα and [N ii]λ6585, thus enabling studies of the gas-phase metallicity and photoionization state of the interstellar medium. The primary aim of our program is to establish how star formation depends on stellar mass and environment, both recognized as drivers of galaxy evolution at lower redshifts. In addition to the main galaxy sample, our target selection places priority on those detected in the far-infrared by Herschel/PACS to assess the level of obscured star formation and investigate, in detail, outliers from the star formation rate (SFR)—stellar mass relation. Galaxies with Hα detections are followed up with FMOS observations at shorter wavelengths using the J-long (1.11–1.35 μm) grating to detect Hβ and [O iii]λ5008 which provides an assessment of the extinction required to measure SFRs not hampered by dust, and an indication of embedded active galactic nuclei. With 460 redshifts measured from 1153 spectra, we assess the performance of the instrument with respect to achieving our goals, discuss inherent biases in the sample, and detail the emission-line properties. Our higher-level data products, including catalogs and spectra, are available to the community.

Additional Information

© 2015 The American Astronomical Society. Received 2014 September 8; accepted 2015 July 29; published 2015 September 11. J.D.S. is supported by JSPS KAKENHI grant Number 26400221 and the World Premier International Research Center Initiative (WPI), MEXT, Japan. D.K. receives support through the Grant-in-Aid for JSPS Fellows (No. 26-3216). A.R. acknowledges support by a grant PRIN-INAF 2012. Facility: Subaru(FMOS).

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Submitted - 1409.0447v2.pdf

Published - Silverman_2015p12.pdf


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August 20, 2023
August 20, 2023