Physics and Astronomy
Scale-invariant morphology parameters applied to atomic hydrogen maps (H i) of galaxies can be used to quantify the effects of tidal interaction or star formation on the interstellar matter (ISM). Here we apply these parameters, concentration, asymmetry, smoothness, Gini, M20, and the GM parameter, to two public surveys of nearby dwarf galaxies, the Very Large Array-ANGST and Local Irregulars That Trace Luminosity Extremes-The H i Nearby Galaxy Survey, to explore whether tidal interaction or the ongoing or past star formation is a dominant force shaping the H i disc of these dwarfs. Previously, H i 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 H i morphology. We compare the H i morphology to three star formation rates based on either Hα, far-ultraviolet or the resolved stellar population, probing different star formation time-scales. The H i 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 Sloan Digital Sky Survey measures of star formation and stellar mass to the H i morphological parameters for all four H i surveys. In the two lower resolution H i surveys (12 arcsec), there is no relation between star formation measures and H i morphology. The morphology of the two high-resolution H i surveys (6 arcsec), the asymmetry, smoothness, Gini, M20, and GM do show a link to the total star formation, but a weak one.
Original Publication Information
Holwerda, B. W., N. Pirzkal, W. J. G. de Blok and S. -L. Blyth. "Quantified H i Morphology - VII. Star Formation and Tidal Influence on Local Dwarf H i Morphology." 2013. Monthly Notices of the Royal Astronomical Society 435(2): 1020-1036.
Holwerda, Benne W.; Pirzkal, N.; de Blok, W. J. G.; and Blyth, S. -L., "Quantified H i morphology – VII. Star formation and tidal influence on local dwarf H I morphology." (2013). Faculty Scholarship. 210.