| Abstract |
We present new observations of the ionized gas in Complexes A, K, and L
obtained with the Wisconsin H-Alpha Mapper (WHAM). To date, there have
been only a limited number of studies of the ionized components of
intermediate and high velocity clouds. Investigating their emission
provides a rare probe of the physical conditions of the clouds and the
halo they are embedded within. These types of measurements will help
guide discussion of the origin and evolution of these neutral halo
structures. Here we follow up on the H-alpha maps we have presented
elsewhere with deeper observations in H-alpha, [S II], [N II], and [O
I]. Distance constraints from absorption studies place this gas in the
mid to lower Galactic halo. Complex A has been constrained to a distance
of 8-10 kpc (Wakker et al. 2008); Complex K has an upper limit of 6.8
kpc; and Complex L at a distance of 8-15 kpc (Wakker 2000). Some halo
gas structures have clear metal line emission (e.g., Smith Cloud; Hill
et al. 2009 and this meeting); however, the lack of [S II] emission
toward Complex C combined with absorption-line observations demonstrates
that it has very low metallically (Wakker, et al. 1999). Such
discoveries reveal ongoing gas replenishment of the evolving Milky Way.
Here, we find a similar lack of emission toward the high-velocity
Complex A. In particular, the cores of its cloud components designated
III and IV show no evidence for metal line emission in our new
observations, which places new constraints on the metallically of this
complex. These observations were taken with WHAM at Kitt Peak, and we
thank the excellent, decade-long support from its staff. WHAM operations
are supported through NSF award AST-0607512. |