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The Subaru Seminar is usually held in Room 104 of the Hilo Base Facility, adjacent to the main lobby. Everyone is welcome to attend. If you are interested in giving a seminar, please contact Subaru seminar organizers (Tae-Soo Pyo, Sherry Yeh, Nagayoshi Ohashi) by email : (please change"_at" to @).

March 10, Tuesday, 11:00 am in 104

" Physical conditions of the interstellar medium in star-forming galaxies at z~1.5 "

Masao Hayashi


We present results from Subaru/FMOS NIR spectroscopy for 118 [OII] emission line galaxies at z=1.47 and 1.62 in the Subaru Deep Field. We use six nebular emission lines in the individual and composite spectra in the rest-frame optical to investigate physical conditions of the ISM in the star-forming galaxies at z~1.5. We have found that the [OII] emitters have strong [OIII] emission lines, showing the [OIII]/[OII] ratios larger than normal star-forming galaxies in the local Universe. There is a dependence of the line ratio on stellar mass in the sense that less massive galaxies have larger [OIII]/[OII] ratios. With evidence that the electron density estimated from the flux ratio of [SII] doublet is consistent with the local galaxies, the high ionization parameter of galaxies at high redshifts is likely to be attributed to harder radiation field by young stellar populations and/or the increasing number of ionizing photon from massive stars. Moreover, we have found that there is a tight correlation between Halpha and [OII], which suggests that [OII] can be a good indicator of star formation rate for galaxies at z~1.5. The line ratios of Halpha/[OII] are consistent with those of the local galaxies.

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