Clumpy Starburst in a Local Dwarf Galaxy, NGC 1522

TL;DR

This study uses VLT/MUSE observations to analyze star formation in the dwarf galaxy NGC 1522, revealing a clumpy star-forming ring, metallicity gradients, and external gas accretion as key factors in its starburst activity.

Contribution

First detailed integral field spectroscopic analysis of star-forming clumps and metallicity distribution in NGC 1522, highlighting external gas inflow as a starburst trigger.

Findings

Identification of nine star-forming clumps with high SFR

Detection of positive metallicity gradient and low N/O ratio

Evidence for external metal-poor gas inflow fueling star formation

Abstract

To investigate the star-forming process in nearby dwarf galaxies, we present Integral Field Units (IFU) observation of the star-forming dwarf galaxy, NGC 1522, with the Very Large Telescope (VLT)/Multi Unit Spectroscopic Explorer (MUSE) as a part of Dwarf Galaxy Integral Survey (DGIS). Our observation reveals the presence of a star-forming clumpy ring in its central region. We identify nine distinct star-forming clumps based on extinction-corrected H$\alpha$ emission-line map, with the total star formation rate (SFR) of about 0.1 $M_\odot$ yr$^{-1}$. The nine clumps are considered to be starbursts, which represent an extreme case in the local universe, without invoking major merging. We investigate the properties of ionized gas using the strong emission lines and `BPT' diagrams, in conjunction with the velocity mapping. Our analysis unveils intriguing patterns, including the positive metallicity gradient and low N/O abundance ratio. This peculiar distribution of metallicity may signify external gas accretion. Our results suggest that the ongoing star formation in NGC 1522 might be triggered and sustained by the inflow of external metal-poor gas.