JHK IMAGING OF THE EDGE-ON SPIRAL GALAXY NGC 891

New near-infrared imaging observations of the edge-on spiral galaxy NGC 891 are presented. The dust lane which is prominent in optical images is also visible at J, H, and even at K. It is confirmed that NGC 891 is not exactly edge-on. The asymmetry of the color distribution with respect to the dust lane indicates that the north-west side is the near side. A map of the color distribution of NGC 891 shows a red central region (A(V) approximately 8 mag), suggesting a condensation of dust in the galactic center. Other observations in the CO emission line and 21 cm continuum also show central peaks. All of these results suggest active star formation in the galactic center. The color excess [E(H - K)], H I, and CO are almost constant along the dust lane in the range of the galactocentric distance r = 2-5 kpc. This suggests that the extinction and the column density of the gas are proportional in this region. The gas-to-extinction ratio is derived to be N(H)/A(V) = 3.6 +/- 1.2 x 10(21) atoms cm-2 mag-1 and the gas-to-dust ratio is estimated to be M(gas)/M(dust) = 110-270. This value is similar to the estimate for our Galaxy (100-200). However, it is about 1/5 of the value (940) derived for NGC 891 from 50-mu-m and 100-mu-m flux observed by IRAS. The K-band luminosity profiles perpendicular to the disk plane were extracted from the data in the range of r = 1.9-3.8 kpc and corrected for the extinction. These extinction-corrected perpendicular profiles show remarkable deviations near the galactic plane (z less-than-or-equal-to 0.5 kpc) from the isothermal sheet model; it is well fitted by an exponential model with a scale height of 350 +/- 50 pc in the range of 0.09 less-than-or-equal-to z less-than-or-equal-to 1.5 kpc. The B-band and I-band profiles obtained with an optical CCD camera are fitted by both an exponential model and an isothermal model with a scale height of about 500 pc. This component with a scale height of approximately 500 pc has been considered to be the old disk component of NGC 891. Therefore, the thin component with an apparent scale height of 350 pc discovered in this study is quite different from the old disk component in terms of the scale height, i.e., the age. The thinness suggests that the component is very young with a close association with star-forming activity. Because this thin component is remarkable in the near-infrared, M-supergiants may be a dominant component.