ANNIBALI, FRANCESCAFRANCESCAANNIBALIBELLAZZINI, MicheleMicheleBELLAZZINICorrenti, M.M.CorrentiSacchi, E.E.SacchiTOSI, MonicaMonicaTOSICignoni, M.M.CignoniAloisi, A.A.AloisiCalzetti, D.D.CalzettiCiotti, L.L.CiottiCUSANO, FELICEFELICECUSANOLee, J.J.LeeNipoti, C.C.Nipoti2020-12-102020-12-1020190004-637Xhttp://hdl.handle.net/20.500.12386/28773We 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<SUP>6</SUP> M <SUB>☉</SUB>, about 1/100 of that of DDO 68. This is a striking example of hierarchical merging in action at the dwarf galaxy scales.STAMPAenArticle10.3847/1538-4357/ab34092-s2.0-85073189772000486374000019https://iopscience.iop.org/article/10.3847/1538-4357/ab34092019ApJ...883...19AFIS/05 - ASTRONOMIA E ASTROFISICA