The properties of post-starburst galaxies from spectral fitting
Abstract
A bimodality has been seen in the morphology, colour and star-forming properties of galaxies.
Throughout cosmic time, the number of galaxies that are quenched to join the red-sequence
has increased, unlike the number of star forming galaxies. Post-starburst galaxies (PSB) are
suspected to be a transition phase between these two stages.
We tried to answer the questions of the mechanism for this transformation. The goal of
our work is to see whether or not all PSB in the nearby universe are being quenched to join
the red-sequence and by which mechanism. We try to show if there is any difference between
the low and high redshift PSB with regard to the accumulated stellar mass in the last 1 and
1.5 Gyr, the star formation history and the amount of dust within the galaxies. In this work we
fit the observed galaxies with the new STARLIGHT code that can fit spectra with or without
photometric data with a library of synthetic models.
First we investigate 189 PSB candidates in the low redshift Sloan Digital Sky Survey (SDSS)
and 1877 comparison samples of star forming and passive galaxies. Depending on the mass,
low or high, we found more than one pathway and mechanism that may transform the blue
cloud to become red sequence type galaxies. Secondly we use Ultra Deep Survey (UDS) and
the spectroscopic follow-up of the UKIDSS Ultra-Deep Survey (UDSz) data for the PSB galaxies
at 0.9 ≤ z ≤ 1.2. From the fitting of 323 galaxies, we determine more constrained physical
properties of UDSz high redshift galaxies, such as the star formation history, mass fraction
that formed at the time of the burst and the dust contents of the galaxies. We speculate that a
higher gas content in these galaxies could have led to the higher burst.
Type
Thesis, PhD Doctor of Philosophy
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