A study of the neglected Galactic HII region NGC 2579 and its companion ESO 370-9

TL;DR

This paper provides the first detailed observational analysis of the Galactic HII region NGC 2579 and its companion ESO 370-9, clarifying their properties and classifications, and exploring their use in studying Galactic chemical gradients.

Contribution

It offers the first comprehensive study of NGC 2579 and ESO 370-9, including their physical, chemical, and stellar properties, correcting previous misclassifications.

Findings

Determined electron temperature and density of NGC 2579.

Measured chemical abundances and ionizing photon flux.

Identified and classified the ionizing stars.

Abstract

The Galactic HII region NGC 2579 has stayed undeservedly unexplored due to identification problems which persisted until recently. Both NGC 2579 and its companion ESO 370-9 have been misclassified as planetary or reflection nebula, confused with each other and with other objects. Due to its high surface brightness, high excitation, angular size of few arcminutes and relatively low interstellar extinction, NGC 2579 is an ideal object for investigations in the optical range. Located in the outer Galaxy, NGC 2579 is an excellent object for studying the Galactic chemical abundance gradients. In this paper we present the first comprehensive observational study on the nebular and stellar properties of NGC 2579 and ESO 370-9, including the determination of electron temperature, density structure, chemical composition, kinematics, distance, and the identification and spectral classification of the ionizing stars, and discuss the nature of ESO 370-9. Long slit spectrophotometric data in the optical range were used to derive the nebular electron temperature, density and chemical abundances and for the spectral classification of the ionizing star candidates. Halpha and UBV CCD photometry was carried out to derive stellar distances from spectroscopic parallax and to measure the ionizing photon flux.