We report the results of infrared photometry on 39 extended red objects
(EROs) in the Carina Nebula, observed with the Spitzer Space Telescope. Most
EROs are identified by bright, extended 8.0 um emission, which ranges from 10''
to 40'' in size, but our sample also includes 4 EROs identified by extended 24
um emission. Of particular interest are nine EROs associated with late O or
early B-type stars and characterized by arc-shaped morphology, suggesting
dusty, stellar-wind bow shocks. These objects are preferentially oriented
towards the central regions of the Carina Nebula, suggesting that these bow
shocks are generally produced by the interactions of OB winds with the bulk
expansion of the H II region rather than high proper motion. We identify
preferred regions of mid-infrared color space occupied by our bow shock
candidates, which also contain bow shock candidates in M17 and RCW 49 but are
well-separated from polycyclic aromatic hydrocarbon emission or circumstellar
discs. Color cuts identify an additional 12 marginally-resolved bow shock
candidates, 10 of which are also associated with known late O or early B stars.
H II region expansion velocities derived from bow shock candidate standoff
distances are ~10 km/s, assuming typical H II region gas densities, comparable
to expansion velocities derived from bow shocks in M17 and RCW 49. One
candidate bow shock provides direct evidence of physical interaction between
the massive stellar winds originating in the Trumpler 15 and Trumpler 14
clusters, supporting the conclusion that both clusters are at similar
heliocentric distances.Comment: 15 pages, 7 figures, MNRAS accepted (2014 October 10