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 @).

August 28, Thursday, at **3:30 pm**

" ALMA Observation of [CII] Line and Dust Continuum of a Normally Star-forming Galaxy in Reionization Epoch "

Kazuati Ota

(Kavli Institute for Cosmology, University of Cambridge)

High redshift star-forming galaxies in the epoch of cosmic reionization (EoR) have been usually detected via either their Lyman alpha emission or UV continua. However, UV lights from such galaxies trace only the lights from ionized gas or stars, and we have seen merely a portion of star formation activities in galaxies. Another aspect yet unexplored is dust-obscured star formation in EoR galaxies, and rest frame far-infrared (FIR) molecular/atomic lines and continuum can probe it because they reflect fuel for star formation and UV light from stars once absorbed and re-emitted by dust, respectively. FIR lights from galaxies in EoR are redshifted to mm wavelengths and observable from the ground with ALMA. Among many FIR lines, 158 micron [CII] is the strongest cooling line of an interstellar medium and suited for probing faint distant galaxies such as ones in EoR. Here I report the first ALMA observation of [CII] line and underlying FIR (redshifted 1.3 mm) continuum of a normally star-forming galaxy in EoR, a z=6.96 Lyman alpha emitter, IOK-1. Probing to unprecedentedly deep limits, I found it undetected in both [CII] and FIR continuum. I will present the constraints on FIR spectral energy distribution of IOK-1, its dust mass, total FIR/IR luminosity, dust-obscured star formation rate and [CII] luminosity and discuss their implications for early galaxy formation in the context of gas and dust.

" MOSFIRE and LDSS3 Spectroscopy for an [OII] Blob at z=1.18: Gas Outflow and Energy Source "

Yuichi Harikane

(University of Tokyo)

We report our Keck/MOSFIRE and Magellan/LDSS3 spectroscopy for an [OII] Blob, OIIB 10, that is a high-z galaxy with spatially extended [OII] 3726,3729 emission over 30 kpc recently identified by a Subaru large-area narrowband survey. The systemic redshift of OIIB 10 is z = 1.18 securely determined with [OIII] 4959,5007 and Hbeta emission lines. We identify FeII2587 and MgII 2796,2804 absorption lines blueshifted from the systemic redshift by 80 +/- 50 and 260 +/- 40 km/s, respectively, which indicate gas outflow from OIIB 10 with the velocity of 80-260 km/s. This outflow velocity is comparable with the escape velocity, 250+/- 140 km/s, estimated under the assumption of a singular isothermal halo potential profile. Some fraction of the outflowing gas could escape from the halo of OIIB 10, suppressing OIIB 10's star-formation activity. The major energy source of the outflow is unclear with the available data. Although no signature of AGN is found in the X-ray data, OIIB 10 falls in the AGN/star-forming composite region in the line diagnostic diagrams. It is possible that the outflow is powered by star formation and a type-2 AGN with narrow FWHM emission line widths of 70-130 km/s.

" Low-mass passive and post-starburst galaxies at z = 1.5 - 2.0 in the UltraVISTA field "

Akie Ichikawa

(Ehime University)

We will present statistical properties of passively-evolving and post-star burst galaxies at z = 1.5 - 2.0 in the COSMOS field. Using simple color sele ction criteria with the ultra-deep Suprime-Cam z'-band and the UltraVISTA DR 2 data, we selected passive and post-starburst galaxies at the redshift. We investigated the stellar mass function of these passive and post-starburst g alaxies separately, and found that the low-mass end slopes are significantly different between these two populations. At low mass of the stellar mass fu nction of these passive galaxies, the number density of these passive galaxi es decreases with decreasing stellar mass at low-mass end, and the number de nsity of low-mass passive galaxies is smaller than massive ones. On the othe r hand, that of the post-starburst galaxies is almost constant at low mass, and the low-mass end slope is significantly flatter than passive galaxies. S ince post-starburst galaxies evolve into passive galaxies within ~1Gyr, thes e galaxies are expected to cause stronger evolution of the number density of the passive population at lower mass.

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

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