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Subaru Seminars are usually held in Room 104 of the Hilo Base Facility, adjacent to the main lobby. Everyone is welcome to attend. If you would like to give a seminar, please contact Subaru seminar organizers (Rusu Cristian Eduard, Tae-Soo Pyo, Nagayoshi Ohashi) by email : sseminar_at_subaru.naoj.org (please change"_at" to @).

November 21, Tuesday, 11am in 104A

" Starburst to Quiescent from HST/ALMA: Stars and dust unveil minor mergers in SMGs at z~4.5 "

Carlos Gomez-Guijarro (Dark Cosmology Centre - Niels Bohr Institute)


Dust-enshrouded, starbursting, submillimeter galaxies (SMGs) at z >= 3 have been proposed as progenitors of z >= 2 compact quiescent galaxies (cQGs). To test this connection, we present a detailed spatially resolved study of the stars, dust and stellar mass in a sample of six submillimeter-bright starburst galaxies at z ~ 4.5. The stellar UV emission probed by HST is extended, irregular and shows evidence of multiple components, undergoing minor mergers with a typical stellar mass ratio of 1:7. The FIR dust continuum emission traced by ALMA locates the bulk of star formation in extremely compact regions. We compare spatially resolved UV slope maps with the FIR dust continuum to study the infrared excess (IRX)-beta relation. The SGMs display systematically higher IRX values than expected from the nominal trend, demonstrating that the FIR and UV emissions are disconnected. Finally, we show that the SMGs fall on the mass-size plane at smaller stellar masses and sizes than cQGs at z = 2. Taking into account the expected evolution in stellar mass and size between z = 4.5 and z = 2 due to the ongoing starburst and mergers with minor companions, this is in agreement with a direct evolutionary connection between the two populations.

" Predicting line fluxes and number counts for future surveys "

Dr. Francesco Valentino (Dark Cosmology Centre - Niels Bohr Institute)


A new golden era for spectroscopic surveys is coming. Dedicated space missions such as Euclid and WFIRST and new ground-based facilities such as Subaru/PFS, VLT/MOONS, or the LSST telescope will provide crucial spectroscopic data for high-precision cosmology, with obvious beneficial consequences for the entire extragalactic astrophysics community. In order to be prepared to maximally exploit the scientific return of these missions, it is fundamental to know in advance how many and what kind of galaxies will be within reach for the various instruments. Here we propose a hybrid approch exploiting available large photometric datasets and smaller dedicated spectroscopic follow-ups to estimate H-alpha, H-beta, [O III]5007AA, and [O II]3727AA fluxes for 35,000 galaxies in COSMOS and GOODS-S. Given the large statistics and the excellent photometric coverage, we can compute cumulative and differential number counts down to limiting fluxes of ~1e-17 erg/cm2/s for all these lines. We show that the evolution of the so-called "Main Sequence" of star-forming galaxies is enough to reproduce the observed evolution of H-alpha number counts. We further explore the physical properties of bright emitters, finding them fairly massive and large. We derive [NII]/H-alpha line ratios and expected H-alpha equivalent widths for this population, providing corrections to the number counts in case of low-resolution spectroscopy. The catalog of line fluxes and the number counts are all publicly released.


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



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