Title:
Near-infrared integral-field spectroscopy of violent
starburst environments
Authors:
Richard de Grijs
Abstract:
Near-infrared (NIR) integral-field spectroscopy
(IFS) of violent starburst environments at high spatial resolution has
the potential to revolutionise our ideas regarding the local interactions
between the newly-formed massive stars and the interstellar medium of
their host galaxies. To illustrate this point, I will present our NIR IFS
analysis of the central starburst region of NGC 1140, obtained with
CIRPASS on Gemini-South, and planned GNIRS observations of the same system.
While strong [Fe II] emission, thought to originate in the thermal shocks
associated with supernova remnants, is found throughout the galaxy,
higher-order Brackett emission is predominantly associated with the
northern starburst region. The Brackett lines originate from recombination
processes occurring on smaller scales in (young) HII regions.
The time-scale associated with strong [Fe II] line emission implies
that most of the recent star-formation activity in NGC 1140 was induced
in the past ~(35-55) Myr. Based on the spatial distributions of the
[Fe II] versus Brackett line emission, we conclude that a galaxy-wide
starburst was induced several tens of Myr ago, with more recent starburst
activity concentrated around the northern starburst region. This scenario
is confirmed by our analysis of the spectral energy distributions of the
compact, young massive star clusters (YMCs) detected in new and archival
broad-band Hubble Space Telescope images. Our photometric mass estimates
of the NGC 1140 YMCs, likely upper limits, are comparable to those of the
highest-mass Galactic globular clusters and to spectroscopically confirmed
masses of (compact) YMCs in other starburst galaxies. Our detection of
similarly massive YMCs in NGC 1140 supports the scenario that such objects
form preferentially in the extreme environments of interacting and
starburst galaxies. I will argue that IFS at higher spatial resolution
would allow us trace (i) the massive outflows ("superwinds") expected
to originate in the dense YMCs, and (ii) their impact on the galaxy's
ISM.