HST Resolves Stars in a Tiny Body Falling on the Dwarf Galaxy DDO 68

Journal
Date Issued
2019
Author(s)
•
•
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Sacchi, E.
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Cignoni, M.
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Aloisi, A.
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Calzetti, D.
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Ciotti, L.
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Lee, J.
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Nipoti, C.
DOI
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 ∼106 M ☉, about 1/100 of that of DDO 68. This is a striking example of hierarchical merging in action at the dwarf galaxy scales.
Volume
883
Issue
1
Start page
19
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2019ApJ...883...19A
Rights
open.access
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