HD1

Discovery

The discovery of HD1 (RA:10:01:51.31 DEC:+02:32:50.0) in the Sextans constellation, along with another high-redshift galaxy, HD2 (RA:02:18:52.44 DEC:-05:08:36.1) in the Cetus constellation, was reported by astronomers at the University of Tokyo on 7 April 2022. These two galaxies were found in two patches of sky surveyed by the Cosmic Evolution Survey and by the Subaru Telescope in the Subaru/XMM-Newton Deep Survey Field respectively. They were found by looking for objects that are much brighter in the so-called K band of infrared than in the H band (around 1.6 microns), which could indicate a Lyman-break galaxy red-shifted by a factor of around 13. In LBG searches, much lower redshift galaxies with Balmer breaks can be misidentified as higher redshift LBGs. As was the case for HD1 and HD2. For this reason they were named "HD 1" and "HD 2" (for "H band dropout", not to be confused with stars HD 1 and HD 2 in the Henry Draper Catalog.