High resolution spectroscopy of the BCD galaxy Haro 15: II. Chemodynamics

TL;DR

This study investigates the physical and chemical properties of nebular material in four star-forming regions of the blue compact dwarf galaxy Haro 15, revealing similarities in ionization structure and differences in evolutionary stages.

Contribution

It provides a detailed chemodynamical analysis of Haro 15's star-forming knots using spectroscopy, highlighting ionization similarities and evolutionary differences.

Findings

Similar ionization structures across kinematical components.

Different evolutionary stages inferred from ionizing structures.

Presence of an older stellar population in one knot.

Abstract

We present a detailed study of the physical properties of the nebular material in four star-forming knots of the blue compact dwarf galaxy Haro 15. Using long-slit and echelle spectroscopy obtained at Las Campanas Observatory, we study the physical conditions (electron density and temperatures), ionic and total chemical abundances of several atoms, reddening and ionization structure, for the global flux and for the different kinematical components. The latter was derived by comparing the oxygen and sulphur ionic ratios to their corresponding observed emission line ratios (the $\eta$ and $\eta$' plots) in different regions of the galaxy. Applying the direct method or empirical relationships for abundance determination, we perform a comparative analysis between these regions. The similarities found in the ionization structure of the different kinematical components implies that the effective temperatures of the ionizing radiation fields are very similar in spite of some small differences in the ionization state of the different elements. Therefore the different gaseous kinematical components identified in each star forming knot are probably ionized by the same star cluster. However, the difference in the ionizing structure of the two knots with knot A showing a lower effective temperature than knot B, suggests a different evolutionary stage for them consistent with the presence of an older and more evolved stellar population in the first.