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UV Continuum Spectroscopy of a 6L* z=5.5 Starburst Galaxy

C. C. Dow-Hygelund·B. P. Holden·R. J. Bouwens·A. van der Wel·G. D. Illingworth·A. Zirm·M. Franx·P. Rosati·H. Ford·P. G. van Dokkum·S. A. Stanford·P. Eisenhardt·G. G. Fazio
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Abstract

We have obtained a high S/N (22.3 hr integration) UV continuum VLT FORS2 spectrum of an extremely bright (z_850 = 24.3) z = 5.515 +/- 0.003 starforming galaxy (BD38) in the field of the z = 1.24 cluster RDCS 1252.9-2927. This object shows substantial continuum (0.41 +/- 0.02 \muJy at \lambda1300) and low-ionization interstellar absorption features typical of LBGs at lower redshift (z ~ 3); this is the highest redshift LBG confirmed via metal absorption spectral features. The equivalent widths of the absorption features are similar to z ~ 3 strong Lyαabsorbers. No noticeable Lyαemission was detected (F <= 1.4 * 10^-18 ergs cm^-2 s^-1, 3σ). The half-light radius of this object is 1.6 kpc (0\farcs25) and the star formation rate derived from the rest-frame UV luminosity is SFR_UV = 38 h^-2_0.7 M_sun yr^-1 (142 h^-2_0.7 M_sun yr^-1 corrected for dust extinction). In terms of recent determinations of the z ~ 6 UV luminosity function, this object appears to be 6L*. The Spitzer IRAC fluxes for this object are 23.3 and 23.2 AB mag (corrected for 0.3 mag of cluster lensing) in the 3.6μand 4.5μchannels, respectively, implying a mass of 1-6 * 10^10 M_sun from population synthesis models. This galaxy is brighter than any confirmed z ~ 6 i-dropout to date in the z_850 band, and both the 3.6μand 4.5μchannels, and is the most massive starbursting galaxy known at z > 5. -- Abstract Abridged

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C. C. Dow-Hygelund, B. P. Holden, R. J. Bouwens, A. van der Wel, G. D. Illingworth, A. Zirm, M. Franx, P. Rosati, H. Ford, P. G. van Dokkum, S. A. Stanford, P. Eisenhardt, G. G. Fazio. 2005-07-12. UV Continuum Spectroscopy of a 6L* z=5.5 Starburst Galaxy. https://doi.org/10.1086/491700

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