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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 (Thayne Currie, Tae-Soo Pyo, Nagayoshi Ohashi) by email : (please change"_at" to @).

May 8, Monday, 11am in 104B

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Antonello Calabro (CEA/Saclay, France)

Low-mass (dwarf) galaxies are the most abundant systems of the Universe at all cosmic epochs, and they are considered the building blocks from which more massive galaxies assemble. This assembly process is not constant, but it peaks at z ∼ 2 and then declines exponentially at later times. Almost 25% of the stellar mass observed today has been assembled after this peak, and a significant part of it formed in young low-mass galaxies in strong, short-lived starbursts. Tracing the galaxy-averaged properties of large, representative samples of star-forming dwarf galaxies out to z ∼ 1 is a necessary step for understanding the evolution of low mass galaxies and and the build-up of stellar mass during the last 9-10 billion years. In this talk I will show the discovery and spectrophotometric characterization of a large sample of 164 faint star-forming dwarf galaxies at redshift 0.13 ≤ z ≤ 0.88 selected by the presence of bright optical emission lines in the VIMOS Ultra Deep Survey (VUDS). I will present their integrated physical properties, including oxygen abundances and ionization conditions, which are used to discuss the low-mass end of the mass-metallicity relation (MZR) and other key scaling relations. The MZR for this sample shows a flatter slope compared to previous studies of galaxies in the same mass range and redshift, while the increasing scatter toward the low-mass end (already found in other works) is partly explained by varying specific SFRs and gas fractions. Comparing the results with simple chemical evolution models, I will show that most star-forming dwarf galaxies do not follow the predictions of a ”closed-box” model, but those from a gas-regulating model in which gas flows are considered. While strong stellar feedback may produce large-scale outflows favoring the cessation of vigorous star formation and promoting the removal of metals, younger and more metal-poor dwarfs may have recently accreted large amounts of fresh, very metal-poor gas, that is used to fuel current star formation.

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

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