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 : sseminar_at_subaru.naoj.org (please change"_at" to @).
May 8, Monday, 11am in 104B
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,