Unravelling the enigmatic ISM conditions in Minkowski's Object

Henry Zovaro (1) , Robert Sharp (1) , Nicole Nesvadba (2) , Lisa Kewley (1) , Ralph Sutherland (1) , Philip Taylor (1) , Brent Groves (1) , Alexander Wagner (3) , Dipanjan Mukherjee (4) , Geoffrey Bicknell (1)

1 ANU - Australian National University
2 LAGRANGE - Joseph Louis LAGRANGE
3 Université de Tsukuba = University of Tsukuba
4 IUCAA - Inter-University Centre for Astronomy and Astrophysics [Pune]

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.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]

Henry Zovaro, Robert Sharp, Nicole Nesvadba, Lisa Kewley, Ralph Sutherland, et al.. Unravelling the enigmatic ISM conditions in Minkowski's Object. Monthly Notices of the Royal Astronomical Society, 2020, 499 (4), pp.4940-4960. ⟨10.1093/mnras/staa3121⟩. ⟨hal-03386093⟩