Peculiarities of the chemical abundance distribution in galaxies NGC 3963 and NGC 7292

TL;DR

This study investigates the chemical abundance distributions in two galaxies, revealing peculiarities likely caused by external gas accretion and major merging, based on spectroscopic analysis of HII regions.

Contribution

It provides detailed spectroscopic measurements of HII regions in NGC 3963 and NGC 7292, highlighting unusual abundance patterns and proposing explanations for these peculiarities.

Findings

Outer arm of NGC 3963 shows excess oxygen and nitrogen.

Abundances in NGC 7292 are uniform across the galaxy.

Peculiarities attributed to external gas accretion and merging.

Abstract

Spectroscopic observations of 32 HII regions in the spiral galaxy NGC 3963 and the barred irregular galaxy NGC 7292 were carried out with the 2.5-m telescope of the Caucasus Mountain Observatory of the Sternberg Astronomical Institute using the Transient Double-beam Spectrograph with a dispersion of 1A/pixel and a spectral resolution of 3A. These observations were used to estimate the oxygen and nitrogen abundances and the electron temperatures in HII regions through modern strong-line methods. In general, the galaxies have oxygen and nitrogen abundances typical of stellar systems with similar luminosities, sizes, and morphology. However, we have found some peculiarities in chemical abundance distributions in both galaxies. The distorted outer segment of the southern arm of NGC 3963 shows an excess oxygen and nitrogen abundances. Chemical elements abundances in NGC 7292 are constant and do not depend on the galactocentric distance. These peculiarities can be explained in terms of external gas accretion in the case of NGC 3963 and major merging for NGC 7292.