Galaxies at Very High Redshifts (z > 1)

Abstract

Observational cosmology is partly based upon wishful thinking. (I am not even going to hint on what is the theoretical cosmology based.) This is, perhaps, inevitable: most, if not all, cosmological tests seem to require idealized test particles or conditions, and there is much skill in coming up with a setup which is the least unrealistically oversimplified. Some classical tests, such as the m vs. z diagram, require the “standard candles”, that is, sources of light whose intrinsic behavior is well understood, and which span a large baseline in redshift. QSO’s are much too finicky, variable, and poorly understood to serve in this role; and ever since the days of Hubble, giant elliptical galaxies were a favorite choice. They seem to qualify, since they are luminous, and can be spotted at high redshifts; this is made easier by the facts that they are often found in rich clusters, and sometimes have powerful radio lobes. Moreover, here and now (z ≃ 0) they seem to live apparently clean and quiet lives, with no ongoing star formation, no optically thick dust, etc. On a closer look this simplicity disappears, but we cannot be too picky now.