Speaker
Mark Sargent
Description
The bimodal distribution of galaxy-integrated star-formation efficiencies (SFE) in
the Schmidt-Kennicutt plane (i.e. the SFR vs. M(H2) diagram) has been the subject of
much debate in recent years. Is the proposed split into a ‘sequence of disks’ and a
‘sequence of starbursts’ a genuine effect or rather an artefact of selection effects
or assumptions underlying the calculation of molecular gas masses? Is this split the
consequence of the time-scales on which galaxies switch from a low-efficiency to a
high-efficiency mode of star formation during, e.g., galaxy interactions or mergers?
I will report on H2+HI gas measurements for a sample of ~40 morphologically selected
SDSS post-merger galaxies which we recently observed with a dedicated program at the
IRAM/30m telescope. By using a careful mass- and SFR-matching technique we are able
to compare the SFE-distribution of our post-mergers with ‘normal’ galaxies from,
e.g., the COLD GASS project, with post-starburst galaxies (e.g., French et al. 2015;
Alatalo et al. 2016), and with close kinematic pair galaxies from SDSS (Violino et
al., in prep.). I will discuss our findings in the context of (a) the evolution of
simulated mergers in the Schmidt-Kennicutt plane, and (b) empirical expectations for
unbiased SFE-distributions we derived using the 2-Star Formation Mode framework
(2-SFM, Sargent et al. 2014).
