Local analogues of high-redshift star-forming galaxies: integral field
  spectroscopy of green peas
  We use integral field spectroscopy, from the SWIFT and Palm3K instruments, to
perform a spatially-resolved spectroscopic analysis of four nearby highly
star-forming `green pea' (GP) galaxies, that are likely analogues of
star-forming systems at z~2.5-3. By studying emission-line maps in H$\alpha$,
[NII]$\lambda \lambda$6548,6584 and [SII]$\lambda$$\lambda$6716,6731, we
explore the kinematic morphology of these systems and constrain properties such
as gas-phase metallicities, electron densities and gas-ionization mechanisms.
Two of our GPs are rotationally-supported while the others are
dispersion-dominated systems. The rotationally-supported galaxies both show
evidence for recent or ongoing mergers. However, given that these systems have
intact disks, these interactions are likely to have low mass ratios (i.e. minor
mergers), suggesting that the minor-merger process may be partly responsible
for the high SFRs seen in these GPs. Nevertheless, the fact that the other two
GPs appear morphologically undisturbed suggests that mergers (including minor
mergers) are not necessary for driving the high star formation rates in such
galaxies. We show that the GPs are metal-poor systems (25-40 per cent of solar)
and that the gas ionization is not driven by AGN in any of our systems,
indicating that AGN activity is not co-eval with star formation in these
starbursting galaxies.
