A Search for a Near-Infrared Halo around NGC 4565

Abstract

We present a near-infrared (3.5-5 μm) search for the integrated emission from low-mass stars and/or brown dwarfs in the halo of the nearby edge-on spiral galaxy NGC 4565. The observation was made with a liquidhelium-cooled rocket-borne telescope using a 256 × 256 InSb array with a pixel scale of 17″. Images of NGC 4565 were successfully obtained with sensitivity near the natural background limit. Our search reveals no evidence of a faint halo around the galaxy, in contrast with the previous reports of a halo around NGC 5907. The lower limit of the mass-to-light ratio for the halo of NGC 4565 is 260 (2 σ) in solar units at 3.5-5 μm. This implies that hydrogen-burning stars do not contribute significantly to the mass of the dark halo in NGC 4565. © 1998. The American Astronomical Society. All rights reserved.