Dust and star formation in the centre of NGC 3311

TL;DR

This study investigates the dust and gas structures in the central region of NGC 3311, revealing a rotating disc with star formation likely triggered by cold gas accretion, contributing to dust longevity.

Contribution

It provides detailed analysis of dust, gas, and star formation in NGC 3311 using archival HST and MUSE data, highlighting a rotating gas disc and its role in star formation.

Findings

Presence of a rotating gas disc aligned with dust structures

Star formation activity associated with the disc's highest emission regions

Supersolar metallicity and significant neutral gas mass inferred

Abstract

NGC 3311 is the central galaxy of the Hydra I galaxy cluster. It has a hot interstellar medium and hosts a central dust lane with emission lines. These dust lanes are frequent in elliptical galaxies, but the case of NGC 3311 might be particularly interesting for problems of dust lifetime and the role of cool gas in the central parts. We aim to use archival HST images and MUSE data to investigate the central dust structure of NGC 3311. We used the tool PyParadise to model the stellar population and extract the emission lines. The HST/ACS colour map reveals the known dust structures, but also blue spots, which are places of strong line emission. A dusty 'mini-jet' emanates from the centre. The distribution of the emission line gas matches the dust silhouette almost exactly. Close to the brightest Halpha emission, the ratio [NII]/Halpha resembles that of HII-regions; in the outer parts, [NII] gets stronger and is similar to LINER-like spectra. The gas kinematics is consistent with that of a rotating disc. The Doppler shifts of the strongest line emissions, which indicate the areas of highest star formation activity, smoothly fit into the disc symmetry. The metallicity is supersolar. The presence of neutral gas is indicated by the fit residuals of the stellar NaI D absorption line, which we interpret as interstellar absorption. We estimate the mass of the neutral gas to be of the order of the X-ray mass. The dynamical mass infers a stellar population of intermediate age, whose globular clusters have already been identified. Our findings can be harmonised in a scenario in which the star formation is triggered by the accretion of cold gas onto a pre-existing gas/dust disc or ring. Newly produced dust then contributes to the longevity of the dust.