Near-infrared structure of the edge-on spiral NGC 4565

Near-infrared J, H, and K band images of the edge-on Sb spiral NGC 4565 are analyzed to investigate the underlying stellar structure of the galaxy. The integrated near-infrared magnitudes of the galaxy and the "intrinsic" (J - K) and (H - K) colors of the disk and bulge outside the NGC 4565 dust lane are reported. The 2.2 μm K-light surface brightness distribution of the NGC 4565 disk and bulge are modeled. The disk is fit to a decaying exponential along the radial direction and a hyperbolic secant function along the vertical (z-height) direction. The bulge brightness profile along the minor axis cannot be adequately modeled with the most popular bulge fitting laws or with an exponential as proposed by Frankston & Schild [AJ, 81, 500 (1976)]. We use a combination of an r^1/4 law for the bulge core and an exponential for the outer bulge to model the bulge. The azimuthal brightness distribution of the bulge is modeled with a "boxy" ellipsoid. The residual near-infrared absorption and emission features of NGC 4565 after removal of the model galaxy are examined. Within the NGC 4565 dust lane E(J - K) increases with the depth of the dust extinction. The K-light optical depth derived for the densest regions of the dust lane (τ_K≈0.40) is similar to that found by Rix & Rieke [ApJ, 418, 123 (1993)] for the dust lanes of M51. Estimates of the scale length and scale height of the dust lane are reported. Based on a comparison of the radial profile of the residual K-light emission of the NGC 4565 disk to constructed "edge-on profiles" of the face-on galaxy M100 we propose a possible face-on appearance for the edge-on galaxy.