Unravelling the enigmatic ISM conditions in Minkowski's Object

TL;DR

This study investigates the interstellar medium conditions in Minkowski's Object, a star-forming dwarf galaxy affected by a radio jet, revealing recent star formation, metallicity variations, and possible origins related to jet interactions.

Contribution

It provides detailed spectroscopic analysis of Minkowski's Object, highlighting its young stellar population, metallicity variation, and proposing two scenarios for its origin related to jet-induced star formation.

Findings

Young stellar population (~10 Myr) confirms recent jet interaction.

Significant metallicity variation (~0.5 dex) within the object.

Evidence of low-level non-stellar ionising source contamination.

Abstract

Local examples of jet-induced star formation lend valuable insight into its significance in galaxy evolution and can provide important observational constraints for theoretical models of positive feedback. Using optical integral field spectroscopy, we present an analysis of the ISM conditions in Minkowski's Object ($z = 0.0189$), a peculiar star-forming dwarf galaxy located in the path of a radio jet from the galaxy NGC 541. Full spectral fitting with PPXF indicates that Minkowski's Object primarily consists of a young stellar population $\sim 10$ Myr old, confirming that the bulk of the object's stellar mass formed during a recent jet interaction. Minkowski's Object exhibits line ratios largely consistent with star formation, although there is evidence for a low level ($\lesssim 15$ per cent) of contamination from a non-stellar ionising source. Strong-line diagnostics reveal a significant variation in the gas-phase metallicity within the object, with $\log\left( \rm O / H \right) + 12$ varying by $\sim 0.5$ dex, which cannot be explained by in-situ star formation, an enriched outflow from the jet, or enrichment of gas in the stellar bridge between NGC 541 and NGC 545/547. We hypothesise that Minkowski's Object either (a) was formed as a result of jet-induced star formation in pre-existing gas clumps in the stellar bridge, or (b) is a gas-rich dwarf galaxy that is experiencing an elevation in its star formation rate due to a jet interaction, and will eventually redden and fade, becoming an ultra-diffuse galaxy as it is processed by the cluster.