An Imaging Survey of the Northern Galactic H Emission with Arcminute Resolution

Introduction

We are presently carrying out an imaging survey of the Galactic H emission in the northern hemisphere. Our instrument, the Virginia Tech Spectral Line Imaging Camera (SLIC) utilizes a fast objective lens (f/1.2, 58mm focal length) with a cryogenically-cooled TK 512512 CCD. The CCD is back-illuminated and has a quantum efficiency of 80% at 650nm. A filter wheel in front of the lens allows us to select interference filters, including a narrowband (1.75nm) H filter and a broader bandpass continuum filter in a line free part of the spectrum. The fast optics in combination with the low noise CCD result in sub-Rayleigh sensitivity at confusion limited levels. (1 Rayleigh = photons cm s sr.) This corresponds to an emission measure sensitivity of 1 pc cm.

Our survey with its resolution is complementary to the WHAM (Wisconsin H-Alpha Mapper) survey of Reynolds and collaborators (see these proceedings) which collects detailed spectral information with approximately resolution. Other efforts in the southern hemisphere are also complementary to ours. These include a similar survey by J. Gausted, P. McCullough and D. Van Buren, a galactic plane Schmidt survey by Q. Parker and collaborators (these proceedings), and Fabry-Perot observations by D. Russeil and collaborators at Marseille (these proceedings).

© Copyright Astronomical Society of Australia 1997