The bubbling galactic disk.: II. The inner 20°

We report 269 mid-infrared bubbles within 10 degrees of the Galactic center from visual inspection of the Spitzer GLIMPSE II Legacy Science program images. The surface density of bubbles is similar to 5 deg(-2) or about 3 times that detected in longitudes broken vertical bar l vertical bar = 10 degrees -65 degrees, because the inner 10 degrees of longitude were more thoroughly searched for small bubbles. There is a gradient in the number of bubbles with longitude with an increase of about a factor of 2 from 2 degrees to 10 degrees; this is probably the result of several factors, including decreasing diffuse background brightness, confusion, and opacity with longitude. Bubble eccentricities are typically between 0.6 and 0.8, and > 50% show evidence for blowouts, which we suggest result from local density fluctuations of the ISMand/ or anisotropic stellar winds and radiation fields. The fraction of bubbles identified with H ii regions and clusters is only about half that found at broken vertical bar l vertical bar > 10 degrees. This is largely a result of the much smaller angular diameter of bubbles cataloged in the inner Galaxy than in the outer Galaxy. At least 12% of the bubbles have morphologies suggestive of triggered star formation. Most of the bubbles that show evidence for triggered star formation in the inner Galaxy have not formed secondary bubbles; it is postulated that this may be because they are too young to have had time for this to occur.