The Planetary Nebula IC 2149 with Adaptive Optics on the MMT

The planetary nebula IC 2149, imaged by the ARIES near-infrared imager and adaptive secondary on the 6.5m MMT. The image is a false color composite of three narrow band filters at 2.088, 2.118, and 2.17 um, (blue, green, and red, respectively). The central star has been allowed to saturate in order to bring out details in the surrounding nebula, which is several thousand times fainter. The inset is a narrow band continuum image of the central bright region magnified by a factor of two. The contrast has been adjusted so that details in the inner dusty shell around the central star can be seen. The 2.17 um filter includes the Brackett-gamma transition of atomic hydrogen, and the 2.118 um filter falls on an important emission line of molecular hydrogen. The 2.088 um filter provides a baseline against which to estimate the strength of the emission lines. The gas of the nebula is glowing brightly in the light of ionized hydrogen, reflected by the predominantly red color of the image. There is no excess emission at 2.118 um, indicating that all the molecular hydrogen has been destroyed long since by the light of the central star. There is substantial continuum emission at all wavelengths. This may be light from the central star being scattered by dust or thermal emission from the dust itself. It is likely that IC 2149 is a relatively old planetary nebula, with an age of perhaps several thousand years out of a lifetime of ten thousand. The progenitor was likely a star somewhat less massive than the sun, which will end its life in a similar fashion. The image has a spatial resolution of ~0.1". This is comparable to the resolution of the WFPC2 instrument on HST at optical wavelengths, and two and a half times better than that of NICMOS on HST at 2um. The adaptive secondary on the MMT allows astronomers to remove the distorting effects of the atmosphere, allowing nearly diffraction-limited images. The unique design of the adaptive optics system also minimizes background noise in the infrared. Thus the full light gathering power and resolution of the MMT's 6.5m aperture can be utilized for the study of diffuse objects such as nebulae and distant galaxies.

Full resolution tiff file: IC2149.full.tif