How does star formation proceed in the circumnuclear starburst ring of NGC 6951?

TL;DR

This study investigates star formation in the circumnuclear ring of NGC 6951, combining multi-wavelength data to determine the age, distribution, and preferred sites of star formation, supporting the 'pearls-on-a-string' scenario.

Contribution

It provides detailed analysis of star formation history and spatial distribution in NGC 6951's ring, combining optical IFU data with archival observations to test star formation models.

Findings

The ring is approximately 1-1.5 Gyr old.

Evidence supports star formation occurring at preferred sites within the ring.

The 'pearls-on-a-string' scenario is favored for the youngest stellar populations.

Abstract

Gas inflowing along stellar bars is often stalled at the location of circumnuclear rings, that form an effective reservoir for massive star formation and thus shape the central regions of galaxies. However, how exactly star formation is proceeding within these circumnuclear starburst rings is subject of debate. Two main scenarios for this process have been put forward: In the first the onset of star formation is regulated by the total amount of gas present in the ring with star forming starting once a mass threshold has reached in a `random' position within the ring like `popcorn'. In the second star formation preferentially takes place near the locations where the gas enters the ring. This scenario has been dubbed `pearls-on-a-string'. Here we combine new optical IFU data covering the full stellar bar with existing multi-wavelength data to study in detail the 580 pc radius circumnuclear starburst ring in the nearby spiral galaxy NGC 6951. Using HST archival data together with Sauron and Oasis IFU data, we derive the ages and stellar masses of star clusters as well as the total stellar content of the central region. Adding information on the molecular gas distribution, stellar and gaseous dynamics and extinction, we find that the circumnuclear ring in NGC 6951 is ~1-1.5 Gyr old and has been forming stars for most of that time. We see evidence for preferred sites of star formation within the ring, consistent with the `pearls-on-a-string' scenario, when focusing on the youngest stellar populations. Due to the ring's longevity this signature is washed out when older stellar populations are included in the analysis.