A Pair of Compact Red Galaxies at Redshift 2.38, Immersed in a 100 kpc Scale Ly-alpha Nebula

P. J. Francis; G. M. Williger; N. R. Collins; P. Palunas; E. M. Malumuth; B. E. Woodgate; H. I. Teplitz; A. Smette; R. S. Sutherland; A. C. Danks; R. S. Hill; D. Lindler; R. A. Kimble; S. A. Heap; J. B. Hutchings

doi:10.1086/321417

arXiv · astro-ph/0102263

A Pair of Compact Red Galaxies at Redshift 2.38, Immersed in a 100 kpc Scale Ly-alpha Nebula

P. J. Francis·G. M. Williger·N. R. Collins·P. Palunas·E. M. Malumuth·B. E. Woodgate·H. I. Teplitz·A. Smette·R. S. Sutherland·A. C. Danks·R. S. Hill·D. Lindler·R. A. Kimble·S. A. Heap·J. B. Hutchings

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Abstract

We present Hubble Space Telescope (HST) and ground-based observations of a pair of galaxies at redshift 2.38, which are collectively known as 2142-4420 B1 (Francis et al. 1996). The two galaxies are both luminous extremely red objects (EROs), separated by 0.8 arcsec. They are embedded within a 100 kpc scale diffuse Ly-alpha nebula (or blob) of luminosity ~10^44 erg/s. The radial profiles and colors of both red objects are most naturally explained if they are young elliptical galaxies: the most distant yet found. It is not, however, possible to rule out a model in which they are abnormally compact, extremely dusty starbursting disk galaxies. If they are elliptical galaxies, their stellar populations have inferred masses of ~10^11 solar masses and ages of ~7x10^8 years. Both galaxies have color gradients: their centers are significantly bluer than their outer regions. The surface brightness of both galaxies is roughly an order of magnitude greater than would be predicted by the Kormendy relation. A chain of diffuse star formation extending 1 arcsec from the galaxies may be evidence that they are interacting or merging. The Ly-alpha nebula surrounding the galaxies shows apparent velocity substructure of amplitude ~ 700 km/s. We propose that the Ly-alpha emission from this nebula may be produced by fast shocks, powered either by a galactic superwind or by the release of gravitational potential energy.

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P. J. Francis, G. M. Williger, N. R. Collins, P. Palunas, E. M. Malumuth, B. E. Woodgate, H. I. Teplitz, A. Smette, R. S. Sutherland, A. C. Danks, R. S. Hill, D. Lindler, R. A. Kimble, S. A. Heap, J. B. Hutchings. 2001-02-15. A Pair of Compact Red Galaxies at Redshift 2.38, Immersed in a 100 kpc Scale Ly-alpha Nebula. https://doi.org/10.1086/321417

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