VLT and HST observations of a candidate high redshift elliptical galaxy in the Hubble Deep Field South

March 1999 • 1999A&A...343L..25S

Authors • Stiavelli, M. • Treu, T. • Carollo, C. M. • Rosati, P. • Viezzer, R. • Casertano, S. • Dickinson, M. • Ferguson, H. • Fruchter, A. • Madau, P. • Martin, C. • Teplitz, H.

Abstract • The combined use of the ESO Very Large Telescope (VLT) UT1 Science Verification (SV) images and of the Hubble Space Telescope (HST) Hubble Deep Field South observations allows us to strengthen the identification as a candidate elliptical galaxy of the Extremely Red Object HDFS 223251-603910 previously identified by us on the basis of NICMOS and Cerro Tololo Interamerican Observatory imaging. The photometry presented here includes VLT data in U, B, V, R, I, a STIS unfiltered image, NICMOS J, H, and K band data, thus combining the 16.5 hours of VLT SV exposures with 101 hours of HST observing. The object is detected in all images except the VLT U band and is one of the reddest known with B-K=9.7+/-0.5. We consider a wide range of models with different ages, metallicities, star formation histories and dust content, and conclude that the observed spectral energy distribution agrees best with that of an old elliptical galaxy at redshift just below 2. Alternative possibilities are discussed in light of their likelihood and of the perspective of spectroscopic confirmation. Based on observations collected at the European Southern Observatory, Paranal, Chile (VLT-UT1 Science Verification Program) and with the NASA/ESA HST, obtained at the STScI, which is operated by AURA, under NASA contract NAS5-26555.

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Harry Teplitz

Senior Scientist