Integral Field Spectroscopy of the cometary starburst galaxy NGC 4861

Journal Article · 24 April 2023 · Monthly Notices of the Royal Astronomical Society

DOI: https://doi.org/10.1093/mnras/stad1219 · OSTI ID:1975166

Roche, Nathan ; Vílchez, José M. ; Iglesias-Páramo, Jorge; Papaderos, Polychronis; Sánchez, Sebastian F. ; Kehrig, Carolina; Duarte Puertas, Salvador

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.

• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office
• OSTI ID: 1975166
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 1 Vol. 523; ISSN 0035-8711
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United Kingdom
• Language: English