An Upper Limit on Galactic Free-Free Emission Near the North Celestial Pole
Session 8 -- Surveys and Cosmology
Display presentation, Monday, June 12, 1995, 9:20am - 6:30pm

## [8.06] An Upper Limit on Galactic Free-Free Emission Near the North Celestial Pole

John E. Gaustad, Eun S. Oh (Swarthmore College), Peter R. McCullough (University of Illinois), Dave Van Buren (IPAC)

We have observed several $7\deg \times 7\deg$ fields at $+84\deg$ declination with a wide-angle CCD camera and narrow-band (1 nm) H-$\alpha$ filter. After subtracting the stellar background using offband images and smoothing to $0.1\deg$ resolution, we set an upper limit on fluctuations in the H$\alpha$ emission at this angular scale of 0.7 Rayleigh, which corresponds to fluctuations in the brightness temperature of the free-free emission at 30 GHZ of $4 \mu K$. Thus the microwave background fluctuations of $44 \mu K$ at $1\deg$ angular scale reported by Netterfield et al. (1995) are probably not significantly contaminated by Galactic free-free emission. This work was supported in part by the Fund for Astrophysical Research, the Keck Foundation, the AAS-REU program, and Swarthmore College.