A Caltech Library Service

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

Annibali, F. and Bellazzini, M. and Correnti, M. and Sacchi, E. and Tosi, M. and Cignoni, M. and Aloisi, A. and Calzetti, D. and Ciotti, L. and Cusano, F. and Lee, J. and Nipoti, C. (2019) HST Resolves Stars in a Tiny Body Falling on the Dwarf Galaxy DDO 68. Astrophysical Journal, 883 (1). Art. No. 19. ISSN 1538-4357. doi:10.3847/1538-4357/ab3409.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Accepted Version
See Usage Policy.


Use this Persistent URL to link to this item:


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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Annibali, F.0000-0003-3758-4516
Bellazzini, M.0000-0001-8200-810X
Correnti, M.0000-0001-6464-3257
Sacchi, E.0000-0001-5618-0109
Tosi, M.0000-0002-0986-4759
Cignoni, M.0000-0001-6291-6813
Aloisi, A.0000-0003-4137-882X
Calzetti, D.0000-0002-5189-8004
Ciotti, L.0000-0002-5708-5274
Cusano, F.0000-0003-2910-6565
Lee, J.0000-0002-2278-9407
Nipoti, C.0000-0003-3121-6616
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 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).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Istituto Nazionale di Astrofisica (INAF)
Subject Keywords:galaxies: dwarf – galaxies: interactions – galaxies: irregular – galaxies: star formation – galaxies: stellar content
Issue or Number:1
Record Number:CaltechAUTHORS:20190917-144733563
Persistent URL:
Official Citation:F. Annibali et al 2019 ApJ 883 19
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98694
Deposited By: Tony Diaz
Deposited On:17 Sep 2019 22:18
Last Modified:16 Nov 2021 17:40

Repository Staff Only: item control page