A Group of Galaxies at Redshift 2.38

Paul Francis; Bruce Woodgate; Steve Warren; Palle Moller; Marg Mazzolini; Andy Bunker; James Lowenthal; Ted Williams; Takeo Minezaki; Yukiyasu Kobayashi; Yuzuru Yoshii

doi:10.1086/176747

arXiv · astro-ph/9511040

A Group of Galaxies at Redshift 2.38

Paul Francis·Bruce Woodgate·Steve Warren·Palle Moller·Marg Mazzolini·Andy Bunker·James Lowenthal·Ted Williams·Takeo Minezaki·Yukiyasu Kobayashi·Yuzuru Yoshii

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Abstract

We report the discovery of a group of galaxies at redshift 2.38. We imaged about 10% of a claimed supercluster of QSO absorption-lines at z=2.38 (Francis & Hewett 1993). In this small field (2 arcmin radius) we detect two Ly-alpha emitting galaxies. The discovery of two such galaxies in our tiny field supports Francis & Hewett's interpretation of the absorption-line supercluster as a high redshift "Great Wall". One of the Ly-alpha galaxies lies 22 arcsec from a background QSO, and may be associated with a multi-component Ly-alpha absorption complex seen in the QSO spectrum. This galaxy has an extended (50kpc) lumpy Ly-alpha morphology, surrounding a compact IR-bright nucleus. The nucleus shows a pronounced break in its optical-UV colors at about 4000 A (rest-frame), consistent with a stellar population of mass about 7E11 solar masses, an age of more than 500 Myr, and little on-going star-formation. C IV emission is detected, suggesting that a concealed AGN is present. Extended H-alpha emission is also detected; the ratio of Ly-alpha flux to H-alpha is abnormally low (about 0.7), probable evidence for extended dust. This galaxy is surrounded by a number of very red (B-K>5) objects, some of which have colors suggesting that they too are at z=2.38. We hypothesize that this galaxy, its neighbors and a surrounding lumpy gas cloud may be a giant elliptical galaxy in the act of bottom-up formation.

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Paul Francis, Bruce Woodgate, Steve Warren, Palle Moller, Marg Mazzolini, Andy Bunker, James Lowenthal, Ted Williams, Takeo Minezaki, Yukiyasu Kobayashi, Yuzuru Yoshii. 1995-11-10. A Group of Galaxies at Redshift 2.38. https://doi.org/10.1086/176747

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