dropout

Dropouts are a means of identifying candidates for distant galaxies through photometry. A dropout is the instance of a source showing in some bands but not others. A high redshift will cause some of the galaxy's typically strong electromagnetic radiation (EMR) bands (e.g., the high point of its black body spectrum) to be shifted to the degree that the images taken in some bands do not show the galaxy at all. Given a set of bands, a galaxy that shows in bands up to, but not including an R band can be termed a red dropout galaxy. Similarly for a blue dropout galaxy. The term OIR-dark galaxy is also used, for those that show in neither optical nor near infrared The advantage of the method for locating distant galaxies is that a few images of a single field of view provide information on multiple galaxies, hinting as to which ones might be extremely distant, reducing the necessary spectrography to identify examples.