Statistics and properties of HII regions in a sample of grand design galaxies I. Luminosity functions

TL;DR

This study analyzes the properties and luminosity functions of HII regions in four grand-design galaxies, revealing consistent slopes across different zones and comparing results with other spiral galaxies to understand star formation.

Contribution

It provides detailed measurements and luminosity functions of HII regions in four galaxies, including separate analysis of arm and interarm zones, and compares findings with previous studies.

Findings

Luminosity function slopes agree with other spiral galaxies.

Slopes in arm and interarm zones are similar within errors.

Results have implications for understanding massive star formation.

Abstract

We present new high quality continuum-subtracted H alpha images of the grand-design galaxies NGC 157, NGC 3631, NGC 6764 and NGC 6951. We have determined the positions, angular sizes, and fluxes of their individual HII regions, and describe statistical properties of the HII region samples. We construct luminosity functions for all the HII regions in the disc and separately for arm and interarm zones for each galaxy. The slopes of the luminosity functions for the complete sample agree well with values published for other spiral galaxies of comparable morphological type. For three galaxies we determined the slopes of the luminosity functions for the spiral arm and interarm zones separately. We find that for NGC 157, NGC 3631, and NGC 6951 these slopes are equal within the errors of determination. We compare our results to those found from earlier work, specifically for M51 and NGC 6814, and discuss implications for massive star forming processes.