The red extended structure of IC 10, the nearest blue compact galaxy

Abstract

The Local Group starburst galaxy IC10 is the closest example of a blue compact galaxy. Here, we use optical gi imaging from CFHT/MegaCam and near infra-red JHK imaging from UKIRT/WFCAM to conduct a comprehensive survey of the structure of IC10. We examine the spatial distribution of its resolved young, intermediate and old stellar populations to large radius and low effective surface brightness levels. Akin to other dwarfs with multiple populations of different ages, stellar populations of decreasing average age are increasingly concentrated in this galaxy. We find that the young, star-bursting population, and the AGB population, are both offset from the geometric center of the older RGB population by a few hundred parsecs, implying that the younger star formation occurred significantly away from the center of the galaxy. The RGB population traces an extended structure that is typical of blue compact galaxies, with an effective radius of ∼ 5.75 arcmins (∼ 1.25 kpc). These measurements show that IC10 is much more extended than has previously been realized, and this blue compact galaxy is one of the most extended dwarf galaxies in the Local Group. The outermost isophotes of this galaxy are very regular in shape and essentially circular in morphology. Based on this analysis, we do not find any evidence to suggest that IC10 has undergone a recent, significant, interaction with an unknown companion.

DUSTiNGS. III. DISTRIBUTION OF INTERMEDIATE-AGE AND OLD STELLAR POPULATIONS IN DISKS AND OUTER EXTREMITIES OF DWARF GALAXIES

“…This previous study measured the effective radius based on a Sérsic profile of the RGB stars to be ¢  5.75 0.11 and of the AGB stars to be ¢  3.22 0.30. We derive an effective radius of the RGB stars to be ¢ 7.0 based on the best-fitting Sérsic profile, but also note that the scale length measured by the cumulative distributions is ¢  5.5 0.5, in close agreement with the value from Gerbrandt et al (2015).…”

“…Because of the larger angular extent, our observations do not reach the edge of the stellar disk. The RGB population has been reported to be not only more spatially extended than the young population and the AGB stars, but offset from these two populations (Gerbrandt et al 2015). This previous study measured the effective radius based on a Sérsic profile of the RGB stars to be ¢  5.75 0.11 and of the AGB stars to be ¢  3.22 0.30.…”

Ghostly haloes in dwarf galaxies: constraints on the star formation efficiency before reionization

“…In addition, we calculated the central galaxy stellar mass using the same procedure (integrating the galaxy exponential profile for the number of red-giant stars, and using the same conversion to stellar mass). However, the central galaxy is (Gerbrandt et al 2015), and NGC6822 (Battinelli et al 2006). The points with errorbars is the data from the references listed above.…”

H i observations of IC 10 with the DRAO synthesis telescope

“…Recent Hi studies of IC 10 suggest that an interaction or merger with another unknown low surface density dwarf galaxy is the most probable explanation for the observed morphology of this galaxy (Nidever et al 2013;Ashley et al 2014). However, Gerbrandt et al (2015) argued that the lack of streams or shells, or any disturbances in the stellar component of IC 10 strongly indicates that it is unlikely that IC 10 has undergone an interaction with an unknown companion. Nidever et al (2013) used a Gravitylab N-body integrator code to perform orbit calculations to determine if the origin of the new Hi feature near IC 10 was due to an IC 10 -M 31 interaction.…”