Bibcode
Battaglia, G.; Irwin, M.; Tolstoy, E.; de Boer, T.; Mateo, M.
Bibliographical reference
The Astrophysical Journal Letters, Volume 761, Issue 2, article id. L31, 6 pp. (2012).
Advertised on:
12
2012
Citations
48
Refereed citations
43
Description
The evolution of small systems such as dwarf spheroidal galaxies (dSphs)
is likely to have been a balance between external environmental effects
and internal processes within their own relatively shallow potential
wells. Assessing how strong such environmental interactions may have
been is therefore an important element in understanding the baryonic
evolution of dSphs and their derived dark matter distribution. Here we
present results from a wide-area CTIO/MOSAIC II photometric survey of
the Carina dSph, reaching down to about two magnitudes below the oldest
main-sequence turnoff (MSTO). This data set enables us to trace the
structure of Carina in detail out to very large distances from its
center, and as a function of stellar age. We observe the presence of an
extended structure made up primarily of ancient MSTO stars, at distances
between 25' and 60' from Carina's center, confirming results in the
literature that Carina extends well beyond its nominal tidal radius. The
large number statistics of our survey reveals features such as isophote
twists and tails that were undetected in other previous, shallower
surveys. This is the first time that such unambiguous signs of tidal
disruption have been found in a Milky Way "classical" dwarf other than
Sagittarius. We also demonstrate the presence of a negative age gradient
in Carina directly from its MSTOs, and trace it out to very large
distances from the galaxy center. The signs of interaction with the
Milky Way make it unclear whether the age gradient was already in place
before Carina underwent tidal disruption.