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تسجيل مستخدم جديدThe FMOS-COSMOS survey of star-forming galaxies at z ~ 1.6. I. Halpha -based star formation rates and dust extinction
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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 H$alpha$ in emission between $1.6{rm -}1.8 mathrm{mu m}$ with $f_{rm Halpha}gtrsim4times10^{-17}$ erg cm$^{-2}$ s$^{-1}$. Here, we specifically focus on 271 sBzK-selected galaxies that yield a H$alpha$ 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 ($0.6lesssim A_mathrm{Halpha} lesssim 2.5$) 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 hbox{$E_mathrm{star}(B-V)/E_mathrm{neb}(B-V)$} is 0.7--0.8, dissimilar to that typically seen at low redshift. After correcting for extinction, we derive an H$alpha$-based main sequence with a slope ($0.81pm0.04$) and normalization similar to previous studies at these redshifts.
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We investigate the relationships between stellar mass, gas-phase oxygen abundance (metallicity), star formation rate, and dust content of star-forming galaxies at z$sim$1.6 using Subaru/FMOS spectroscopy in the COSMOS field. The mass-metallicity rela
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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 Halpha emission line that falls
within the H-band (1.6-1.8 um) spectroscopic window from star-forming galaxies with 1.4 < z < 1.7 and M_stellar>~10^10 Msolar. With the high multiplex capability of FMOS, it is now feasible to construct samples of over one thousand galaxies having spectroscopic redshifts at epochs that were previously challenging. The high-resolution mode (R~2600) effectively separates Halpha and [NII]6585 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 - stellar mass relation. Galaxies with Halpha detections are followed up with FMOS observations at shorter wavelengths using the J-long (1.11-1.35 um) grating to detect Hbeta and [OIII]5008 that provides an assessment of extinction required to measure star formation rates 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.
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