HD1
High-redshift galaxy in the constellation Sextans
HD1 is a high-redshift galaxy, which was once a candidate for the most distant known galaxies yet identified in the observable universe. From early data the redshift was estimated of approximately z=13. Followup JWST spectroscopy found it to be an interloper, and is in fact a passive galaxy at a much lower redshift (z = 4.0).
01Discovery
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.
Sources and credits
This article is adapted from the Wikipedia article “HD1”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- Three-color image of galaxy HD1.jpg by Harikane et al., CC BY 4.0
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