Spectrophotometry of Haro Starburst Galaxies

Summary

Photometric observations on a group of eleven Haro starburst galaxies were carried out with the 1.0-m JKT over several semesters giving details of galaxy morphology and colour. These photometric images were then used in spectroscopic observations with the 2.5-m INT to enable accurate slit placement across the star forming knots. High and low dispersion spectra of the HII star forming regions were obtained, allowing the calculation of element abundance, abundance gradients, ionised gas dynamics, and estimates on burst age and possible starburst cause.

Introduction

The sample

The galaxies were chosen from Haro's (1956) list of 44 blue galaxies. They are characterised by having an ultra-violet excess spectrum and emission lines from hot gas. Most of the galaxies showed unusual or chaotic morphologies, with the blue emission emanating from compact, usually central, regions. Our more detailed observation revealed a diverse sample of morphological species, including two spirals, five nuclear ellipticals (Loose 1986), two cigar-shaped irregulars and two clumpy irregulars. Table 1 lists the name, type, absolute visual magnitude, heliocentric distance, actual diameter and integrated colour of each galaxy. A Hubble constant of 75 kms⁻¹ Mpc⁻¹ is used throughout.

Observations and data reduction

Photometric observations were carried out on the 1.0-m JKT in February 1985 and January 1988 with 512×320 pixel CCD detectors. The galaxies were observed through B, V and I filters. Contour maps are given in Figure 1.