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Session 70 - Cosmic Backgrounds and the Distant Universe.
Oral session, Thursday, June 11

[70.06] Near-Infrared Search for Baryonic Dark Matter in the Halo of NGC 4565

J. J. Bock (JPL), A. E. Lange, S. A. Yost (Caltech), K. Uemizu, M. Kawada, T. Matsumoto (ISAS, Japan)

We present near-infrared images of the nearby edge-on spiral galaxy NGC 4565 in a search for infrared emission from baryonic dark matter in the massive galactic halo. The observation was made with a liquid-helium-cooled rocket-borne telescope using a low-background 256 x 256 InSb focal plane array. The field of view subtended 1.2 x 1.2 degrees with 17" pixels to map extended emission out to large radii and to accurately measure and subtract the sky brightness. The images achieve near-background-limited performance at 3.5 - 5.5 \mum where emission from the zodiacal foreground is at a minimum. We are able to map the surface brightness of the galaxy to < 0.5 nW/m^2 sr (0.2 % of the zodiacal foreground). By measuring the surface brightness as a function of radius, we do not detect a component associated with the massive halo, obtaining a lower limit on the mass-to-light ratio of the halo M/L > 250. This observation places strong contraints on the fraction of stars near the hydrogen-burning limit in the galactic halo.

Program listing for Thursday