Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2012-01-16
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
The Astrophysical Journal, in press. Full-resolution version available on request from the first author
Scientific paper
We present new Hubble Space Telescope Advanced Camera for Surveys imaging of six positions spanning 5.8 kpc of the HI major axis of the Local Group dIrr NGC 6822, including both the putative companion galaxy and the large HI hole. The resulting deep color magnitude diagrams show that NGC 6822 has formed >50% of its stars in the last ~5 Gyr. The star formation histories of all six positions are similar over the most recent 500 Myr, including low-level star formation throughout this interval and a weak increase in star formation rate during the most recent 50 Myr. Stellar feedback can create the giant HI hole, assuming that the lifetime of the structure is longer than 500 Myr; such long-lived structures have now been observed in multiple systems and may be the norm in galaxies with solid-body rotation. The old stellar populations (red giants and red clump stars) of the putative companion are consistent with those of the extended halo of NGC 6822; this argues against the interpretation of this structure as a bona fide interacting companion galaxy and against its being linked to the formation of the HI hole via an interaction. Since there is no evidence in the stellar population of a companion galaxy, the most likely explanation of the extended HI structure in NGC 6822 is a warped disk inclined to the line of sight.
Bigiel Frank
Cannon John M.
Cole Andrew A.
de Blok J. G. W.
Dolphin Andrew E.
No associations
LandOfFree
On the Origin of the Supergiant HI Shell and Putative Companion in NGC 6822 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with On the Origin of the Supergiant HI Shell and Putative Companion in NGC 6822, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and On the Origin of the Supergiant HI Shell and Putative Companion in NGC 6822 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-409446