Tuesday, 8/9/13

Just one paper I thought might be interesting for our group today and even it’s a bit of a stretch. Anyways, a way to quantify HI morphology in dwarf galaxies by Holwerda et al.:

Title: Quantified HI Morphology VII: star-formation and tidal influence on local dwarf HI morphology
Authors: Holwerda, B. W.; Pirzkal, N.; de Blok, W. J. G.; Blyth, S-L.
Publication: eprint arXiv:1307.2085
Publication Date: 07/2013
Origin: ARXIV
Keywords: Astrophysics – Cosmology and Extragalactic Astrophysics
Comment: 26 figures, 4 tables, two appendices. Third appendix (HI maps of all galaxies) omitted. Accepted by MNRAS
Bibliographic Code: 2013arXiv1307.2085H


Scale-invariant morphology parameters applied to atomic hydrogen maps (HI) of galaxies can be used to quantify the effects of tidal interaction or star-formation on the ISM. Here we apply these parameters, Concentration, Asymmetry, Smoothness, Gini, M20, and the GM parameter, to two public surveys of nearby dwarf galaxies, the VLA-ANGST and LITTLE-THINGS survey, to explore whether tidal interaction or the ongoing or past star-formation is a dominant force shaping the HI disk of these dwarfs. Previously, HI morphological criteria were identified for ongoing spiral-spiral interactions. When we apply these to the Irregular dwarf population, they either select almost all or none of the population. We find that only the Asymmetry-based criteria can be used to identify very isolated dwarfs (i.e., these have a low tidal indication). Otherwise, there is little or no relation between the level of tidal interaction and the HI morphology. We compare the HI morphology to three star-formation rates based on either Halpha, FUV or the resolved stellar population, probing different star-formation time-scales. The HI morphology parameters that trace the inequality of the distribution, the Gini, GM, and M20 parameters, correlate weakly with all these star-formation rates. This is in line with the picture that local physics dominates the ISM appearance and not tidal effects. Finally, we compare the SDSS measures of star-formation and stellar mass to the HI morphological parameters for all four HI surveys. In the two lower-resolution HI surveys (12"), there is no relation between star-formation measures and HI morphology. The morphology of the two high-resolution HI surveys (6"), the Asymmetry, Smoothness, Gini, M20, and GM, do show a link to the total star-formation, but a weak one.

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