Optical and Infrared Images of Galaxies: What’s to be Learned?
Multiwavelength imaging surveys of galaxies are of great value for investigations of their structure and stellar content. The advent of large format near-IR (NIR) arrays means that such surveys need no longer be confined to the optical. There are major advantages in concurrently carrying out a survey in the optical and NIR. While optical light traces the young blue stellar content of a galaxy, the NIR images will be effective tracers of the older stars and hence, as we will argue, of the stellar mass distribution. In the NIR the effects of dust extinction are minimized. The variation in appearance of structures such as spiral arms, bars, and disks as they are viewed from 0.4 to 2.2μm can set constraints on theories of their formation and evolution. The effects of internal dust absorption and scattering on the observed properties of a galaxy can be better studied. The effects of stellar and dynamical evolution on observations of distant galaxies can be better predicted. This review will give examples of applications of multicolor galaxy surveys and show some results from a partially completed OSU survey of ∼230 spiral galaxies in BVRJHK. A new technique developed to detect dynamical structures in disk galaxies based on observed color gradients will be discussed in some detail.
KeywordsStar Formation Infrared Image Spiral Galaxy Surface Brightness Stellar Population
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