David Martinez-Delgado, Aaron J. Romanowsky, R. Jay Gabany, Francesca Annibali, Jacob A. Arnold, Juergen Fliri, Stefano Zibetti, Roeland P. van der Marel, Hans-Walter Rix, Taylor S. Chonis, Julio A. Carballo-Bello, Alessandra Aloisi, Andrea V. Maccio, J. Gallego-Laborda, Jean P. Brodie, Michael R. Merrifield
We map and analyze a stellar stream in the halo of the nearby dwarf starburst
galaxy NGC 4449, detecting it in deep integrated-light images using the Black
Bird Observatory 0.5-meter telescope, and resolving it into red giant branch
stars using Subaru/Suprime-Cam. The properties of the stream imply a massive
dwarf spheroidal progenitor, which will continue to disrupt and deposit an
amount of stellar mass that is comparable to the existing stellar halo of the
main galaxy. The ratio between luminosity or stellar-mass between the two
galaxies is ~1:50, while the dynamical mass-ratio when including dark matter
may be ~1:10-1:5. This system may thus represent a "stealth" merger, where an
infalling satellite galaxy is nearly undetectable by conventional means, yet
has a substantial dynamical influence on its host galaxy. This singular
discovery also suggests that satellite accretion can play a significant role in
building up the stellar halos of low-mass galaxies, and possibly in triggering
their starbursts.
View original:
http://arxiv.org/abs/1112.2154
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