HST Resolves Stars in a Tiny Body Falling on the Dwarf Galaxy DDO 68
Abstract
We present new Hubble Space Telescope imaging of a stream-like system associated with the dwarf galaxy DDO 68, located in the Lynx-Cancer void at a distance of D ~ 12.65 Mpc from us. The stream, previously identified in deep Large Binocular Telescope images as a diffuse low surface brightness structure, is resolved into individual stars in the F606W (broad V) and F814W (~I) images acquired with the Wide Field Camera 3. The resulting V, I color–magnitude diagram (CMD) of the resolved stars is dominated by old (age 1–2 Gyr) red giant branch (RGB) stars. From the observed RGB tip, we conclude that the stream is at the same distance as DDO 68, confirming the physical association with it. A synthetic CMD analysis indicates that the large majority of the star formation activity in the stream occurred at epochs earlier than ~1 Gyr ago, and that the star formation at epochs more recent than ~500 Myr ago is compatible with zero. The total stellar mass of the stream is ~10^6 M⊙, about 1/100 of that of DDO 68. This is a striking example of hierarchical merging in action at the dwarf galaxy scales.
Additional Information
© 2019 The American Astronomical Society. Received 2019 April 2; revised 2019 July 9; accepted 2019 July 19; published 2019 September 17. These data are associated with the HST GO program 14716 (PI: F. Annibali). Support for program number 14716 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA contract NAS5-26555. F.A., M.C., and M.T. kindly acknowledge funding from INAF PRIN-SKA-2017 program 1.05.01.88.04. We thank the anonymous referee for her/his useful comments and suggestions. Facilities: HST(ACS and WFC3) - Hubble Space Telescope satellite, LBT(LBC). - Software: Drizzlepac (Gonzaga et al. 2012), Dolphot (Dolphin 2000).Attached Files
Published - Annibali_2019_ApJ_883_19.pdf
Accepted Version - 1904.01986.pdf
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Additional details
- Eprint ID
- 98694
- Resolver ID
- CaltechAUTHORS:20190917-144733563
- NAS5-26555
- NASA
- 1.05.01.88.04
- Istituto Nazionale di Astrofisica (INAF)
- Created
-
2019-09-17Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)