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High - High-redshift galaxies can now be identified...

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High-redshift galaxies can now be identified wholesale by a particularly simple kind of photometric redshift, using that fact that any non-AGN galaxy goes black at the Lyman limit (912 Å). Thus faint objects which are blue in some passband like V-R but undetectable to low limits in U or B are likely to be high-redshift systems whose Lyman limit is redshifted into the optical band. This approach was described by Steidel and Hamilton (1992 AJ 104, 941), and exploited by many starting with Steidel et al. (1996 ApJL 462, L17 and AJ 112, 352) to find a rich field of objects for followup spectroscopy. Most galaxies known at z > 3 started detection in this way. This selection - deep in the emitted UV - will impose unavoidable biases in what kinds of galaxies show up, favoring objects with high star-formation rate, high UV luminosity, and low net extinction. Galaxies have been identified in this way out to z =5.5, and maybe to 6.7. The panels below show the brightest of the Lyman-break galaxies above z=3 in the original Hubble Deep Field, with wavelengths near 3000, 4500, 6060, and 8140 A. The clumpy object in the
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