Subaru Seminars



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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 @).

October 21, Tuesday, at 11 am

"Discovery of [OII] blobs: A Clue to a Feedback/Star-Formation Quenching Process at High Redshifts "

Suraphong Yuma

(ICRR, The University of Tokyo)

We have discovered 12 galaxies at z ~ 1.2 in SXDS field showing a largely extended (> 30 kpc) [OII] nebula, which we call [OII] blobs (OIIBs). Some of these galaxies are probably experiencing the final phase of star formation with their gas heated and expelled out by AGN/supernova feedback, and quenching star formation whose process is a key to produce passively-evolving ellipticals. One of 12 OIIBs is a giant OIIB with a spatial extent over 75 kpc, which hosts an obscured type-2 AGN. The ongoing outflow process in this object is confirmed by VLT/VIMOS optical spectroscopy with an outflow velocity of 500 - 600 km/s, suggesting that a major heating source of this giant blob is AGN or associated shock excitation rather than supernova feedback. Other OIIBs do not show clear AGN activity, but our spectroscopy confirms a moderate outflow with a velocity of ~ 200 - 300 km/s, suggesting that the outflow of these OIIBs is driven by star formation. The number density of OIIBs with AGN is 5x10^-6 Mpc^-3, comparable with that of AGN driving outflow at the similar redshift. Meanwhile, the number density of all OIIBs including no AGN hosting galaxies is 6x10^-5 Mpc^-3, indicating that 3% of star-forming galaxies at z ~ 1 are quenching star formation through outflows involving spatially extended [OII] emission.

" Resolving the Extragalactic Background Light with the Multifield Deep ALMA Data "

Seiji Fujimoto

(University of Tokyo)

Submm galaxies (SMGs) are key for understanding the dusty-side of star-formation activities at high redshift. SMGs are probably major sources contributing to the extra-galactic background light (EBL) in the submm band, but the EBL is not fully resolved, due to the low sensitivity and limited spatial resolution of the previous submm observations. We thus explore the faint SMGs with the 27 pointing deep ALMA data, which is the largest data to date, at Band 6 that allow us to reliably investigate faint SMGs with the FIR star-formation rate of ~10-100 M_sun/yr, which is comparable to those of optically-selected galaxies, such as BzK galaxies. Exploring the high sensitivity and spatial resolution of ALMA, we have identified 22 faint SMGs that are about 2 times larger than the previous ALMA studies. Combining the bright SMG data in the literature, we derive the number counts at 1.2mm in the wide range of flux densities, 0.1-10.0 mJy. Based on the reliable number counts of the SMGs, we discuss the SMGs' contribution to the EBL, their redshift distribution, and the cosmic dust abundance locked up in SMGs at high redshift.

Seminars are also held at JAC, CFHT, and IfA.

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