Integral Field Spectroscopy of the cometary starburst galaxy NGC 4861

DOI: 
10.1093/mnras/stad1219
Publication date: 
13/07/2023
Main author: 
Roche, Nathan
IAA authors: 
Roche, Nathan;Vílchez, José M.;Iglesias-Páramo, Jorge;Kehrig, Carolina;Duarte Puertas, Salvador
Authors: 
Roche, Nathan;Vílchez, José M.;Iglesias-Páramo, Jorge;Papaderos, Polychronis;Sánchez, Sebastian F.;Kehrig, Carolina;Duarte Puertas, Salvador
Journal: 
Monthly Notices of the Royal Astronomical Society
Publication type: 
Article
Volume: 
523
Pages: 
270
Abstract: 
Using the PMAS Integral Field Unit on the Calar Alto 3.5 m telescope, we observed the southern component (Markarian 59) of the 'cometary' starburst galaxy NGC 4861. Mrk 59 is centred on a giant nebula and concentration of stars 1 kpc in diameter. Strong $\rm H\,\alpha$ emission points to a star-formation rate (SFR) at least 0.47 $\rm M_{\odot }\, yr^{-1}$. Mrk 59 has a very high [O III] $\rm \lambda 5007/H\,\beta$ ratio, reaching 7.35 in the central nebula, with a second peak at a star-forming hotspot further north. Fast outflows are not detected but nebular motion and galaxy rotation produce relative velocities up to 40 km $\rm s^{-1}$. Spectral analysis of different regions with 'Fitting Analysis using Differential evolution Optimization' (FADO) finds that the stars in the central and 'spur' nebulae are very young, $\rm \le 125~Myr$ with a large $\rm \lt 10~Myr$ contribution. Older stars ($\rm \sim 1~Gyr$) make up the northern disk component, while the other regions show mixtures of 1 Gyr age with very young stars. This and the high specific SFR $\rm \sim 3.5~Gyr^{-1}$ imply a bimodal star formation history, with Mrk 59 formed in ongoing starbursts fuelled by a huge gas inflow, turning the galaxy into an asymmetric 'green pea' or blue compact dwarf. We map the He II λ4686 emission, and identify a broad component from the central nebula, consistent with the emission of ~300 Wolf-Rayet stars. About a third of the He II λ4686 flux is a narrow line emitted from a more extended area covering the central and spur nebulae, and may have a different origin.
Database: 
ADS
URL: 
https://ui.adsabs.harvard.edu/#abs/2023MNRAS.523..270R/abstract
ADS Bibcode: 
2023MNRAS.523..270R
Keywords: 
stars: Wolf-Rayet;galaxies: evolution;galaxies: individual: NGC 4861: Markarian 59;galaxies: starburst;Astrophysics - Astrophysics of Galaxies