The Spitzer Space Telescope First Look Survey:: Neutral hydrogen emission

The Spitzer Space Telescope ( formerly SIRTF) extragalactic First Look Survey covered about 5 deg(2) centered on ( J2000.0) alpha = 17(h)18(m), delta = 59 degrees 30' in order to characterize the infrared sky with high sensitivity. We used the 100 m Green Bank Telescope to image the 21 cm Galactic H I emission over a 3 degrees x 3 degrees square, covering this position with an effective angular resolution of 9.'8 and a velocity resolution of 0.62 km s(-1). In the central square degree of the image the average column density is N(HI) = 2.5; 10(20) cm(-2) with an rms fluctuation of 0.3 x 10(20) cm(-2). The Galactic H I in this region has a very interesting structure. There is a high-velocity cloud, several intermediate- velocity clouds ( one of which is probably part of the Draco Nebula), and narrow-line low-velocity filaments. The H i emission shows a strong and detailed correlation with dust. Except for the high-velocity cloud, all features in the NH i map have counterparts in an E( B - V) map derived from infrared data. Relatively high E( B - V)/ NH i ratios in some directions suggest the presence of molecular gas. The best diagnostic of such regions is the peak H i line brightness temperature, not the total NH i : directions where T(b) > 12 K have E( B - V)/ N(HI) significantly above the average value. The data corrected for stray radiation have been released via the World Wide Web.