Lopsidedness in dwarf irregular galaxies

Abstract

We quantify the amplitude of the lopsidedness, the azimuthal angular asymmetry index, and the concentration of star forming regions, as represented by the distribution of the H$\alpha$ emission, in a sample of 78 late-type irregular galaxies. We bin the observed galaxies in two groups representing blue compact galaxies (BCDs) and low surface brightness dwarf galaxies (LSBs). The light distribution is analysed with a novel algorithm, which allows detection of details in the light distribution pattern. We find that while the asymmetry of the underlying continuum light, representing the older stellar generations, is relatively small, the H$\alpha$ emission is very asymmetric and is correlated in position angle with the continuum light. We test a model of random star formation over the extent of a galaxy by simulating HII regions in artificial dwarf galaxies. The implication is that random star formation over the full extent of a galaxy may be generated in LSB dwarf-irregular galaxies but not in BCD galaxies.

42 pages, LaTex. Accepted by: MNRAS, 13 Mar 2000

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Cited by in corpus (10)

• Palomar/Las Campanas Imaging Atlas of Blue Compact Dwarf galaxies: I. Images and integrated photometry
• Star Formation Properties of a Large Sample of Irregular Galaxies
• Lopsided Spiral Galaxies
• Full-Fledged Dwarf Irregular Galaxy Leo A
• On the Origin of Lopsidedness in Galaxies as Determined from the Spitzer Survey of Stellar Structure in Galaxies (S4G)
• In-spiraling Clumps in Blue Compact Dwarf Galaxies
• Are interactions the primary triggers of star formation in dwarf galaxies?
• Local Tadpole Galaxies
• Distribution of star-forming complexes in dwarf irregular galaxies
• Kinematical asymmetry in the dwarf irregular galaxy WLM and a perturbed halo potential