Near‐Infrared Halo Emission in the Edge‐on Spiral Galaxy ESO 240‐G11

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Abstract
In an extremely deep Kdark band (2.27-2.43 μm) image of the southern edge-on spiral galaxy ESO 240-G11, we detect halo emission extending to between 10 and 15 h−169 kpc away from the disk in vertical cuts near the nucleus. In vertical cuts taken well away from the nucleus, no halo emission is detected. To our detection limit, these data are well modeled by a spherically symmetric component having an exponential radial surface brightness profile plus a sech z disk. The exponential radial surface brightness profile suggests an unusually faint and extended spiral bulge. A ρ ∝ r-3.5 spheroid plus sech z disk is nearly as good a fit. It is also possible to fit these data with a ρ ∝ r-2 component tracing the massive halo. However, this requires a larger error in setting the sky level than appears likely. These data, which were taken with a 60 cm infrared optimized telescope at the South Pole, permit surface photometry reaching 25 mag arcsec-2. ESO 240-G11 is dynamically, environmentally, and morphologically similar to NGC 5907. In NGC 5907, several authors have detected red and near-infrared halo emission at comparable imaging depths that appears to trace the dark matter halo.

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