Local analogues of high-redshift star-forming galaxies: integral field spectroscopy of green peas

TL;DR

This study uses integral field spectroscopy to analyze four nearby green pea galaxies, revealing their kinematic states, metallicities, and ionization sources, and exploring their similarities to high-redshift star-forming galaxies.

Contribution

It provides the first spatially-resolved spectroscopic analysis of green pea galaxies, showing their diverse kinematic properties and the role of minor mergers in their high star formation rates.

Findings

Two GPs are rotationally-supported; two are dispersion-dominated.

Green peas are metal-poor, with 25-40% of solar metallicity.

Star formation is not driven by AGN activity.

Abstract

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.

Figures

Full text

See pages 1-last of green-peas-clean2.pdf