Reflection of Bulge Light from a 2 Kiloparsec Segment of Dust Lane in the Galaxy NGC 2841

Abstract

The highly inclined galaxy NGC 2841 shows an amorphous linear strip transverse to the nearside minor axis that is bright in the optical but coincident with a dark dust lane at 2.1 μm. Spectra of this strip obtained with the Low-Resolution Imaging Spectrometer on the Keck II telescope are essentially identical to spectra of the bulge, indicating that the emission from the strip is scattered light from the bulge. Fifteen Lick/IDS absorption features (including the G band, the MgH + Mg b band, and Na D) have been measured in the strip spectrum, and their indices are typical of late-type bulge stars. The equivalent widths of these absorption indices are essentially the same in the bulge and strip spectra, as are the shapes of the continua. The spectrum of a typical association of stars in the disk close to the strip is very different from both bulge and strip spectra, showing Balmer lines characteristic of a young population of stars. We estimate that ~2% of the bulge light received by the amorphous strip is scattered in our direction. This is consistent with our previous prediction of this effect, based on V and K' imaging data. Considering the geometry, we suggest the scattering cloud could extend to ~500 pc above the plane, similar to the heights of other dust features recently found in galaxies.