Resolving The Generation of Starburst Winds in Galaxy Mergers. (arXiv:1301.0841v1 [astro-ph.CO])

Resolving The Generation of Starburst Winds in Galaxy Mergers. (arXiv:1301.0841v1 [astro-ph.CO]):
We study galaxy super-winds driven in major mergers, using pc-resolution
simulations with detailed models for stellar feedback that can
self-consistently follow the formation/destruction of GMCs and generation of
winds. The models include molecular cooling, star formation at high densities
in GMCs, and gas recycling and feedback from SNe (I&II), stellar winds, and
radiation pressure. We study mergers of systems from SMC-like dwarfs and Milky
Way analogues to z~2 starburst disks. Multi-phase super-winds are generated in
all passages, with outflow rates up to ~1000 M_sun/yr. However, the wind
mass-loading efficiency (outflow rate divided by SFR) is similar to that in
isolated galaxy counterparts of each merger: it depends more on global galaxy
properties (mass, size, escape velocity) than on the dynamical state of the
merger. Winds tend to be bi- or uni-polar, but multiple 'events' build up
complex morphologies with overlapping, differently-oriented bubbles/shells at a
range of radii. The winds have complex velocity and phase structure, with
material at a range of speeds up to ~1000 km/s, and a mix of molecular,
ionized, and hot gas that depends on galaxy properties and different feedback
mechanisms. These simulations resolve a problem in some 'sub-grid' models,
where simple wind prescriptions can dramatically suppress merger-induced
starbursts. But despite large mass-loading factors (>~10) in the winds, the
peak SFRs are comparable to those in 'no wind' simulations. Wind acceleration
does not act equally, so cold dense gas can still lose angular momentum and
form stars, while blowing out gas that would not have participated in the
starburst in the first place. Considerable wind material is not unbound, and
falls back on the disk at later times post-merger, leading to higher
post-starburst SFRs in the presence of stellar feedback. This may require AGN
feedback to explain galaxy quenching.