Astrophys. J., 630, L137-L140 (2005/September-2)
UV continuum spectroscopy of a 6L*z = 5.5 starburst galaxy.
DOW-HYGELUND C.C., HOLDEN B.P., BOUWENS R.J., VAN DER WEL A., ILLINGWORTH G.D., ZIRM A., FRANX M., ROSATI P., FORD H., VAN DOKKUM P.G., STANFORD S.A., EISENHARDT P. and FAZIO G.G.
Abstract (from CDS):
We have obtained a high S/N (22.3 hr integration) UV continuum VLT FORS2 spectrum of an extremely bright (z850=24.3) z = 5.515±0.003 star-forming galaxy (BD38) in the field of the z = 1.24 cluster RDCS 1252.9-2927. From HST Advanced Camera for Surveys imaging, this object was selected as a potential z ∼ 6 Lyman break galaxy (LBG) based on its red i775-z850=1.5 color. This object shows substantial continuum (0.41±0.02 µJy at 1300 Å) 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 Lyα absorbers. No noticeable Lyα emission was detected (F≤1.4x10–18 ergs/cm2/s, 3 σ). This object is at most amplified 0.3 mag from gravitational lensing by the foreground cluster. The delensed half-light radius of this object is 1.6 kpc (0".25), and the star formation rate derived from the rest-frame UV luminosity is SFRUV=38 h–20.7M☉/yr (142 h–20.7M☉/yr 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 (delensed) in the 3.6 and 4.5 µm channels, respectively, implying a mass of (1-6) x1010 M☉from population synthesis models. This galaxy is brighter than any confirmed z ∼ 6 i-dropout to date in the z850 band, and in the 3.6 and 4.5 µm channels, and is the most massive starbursting galaxy known at z > 5.
Galaxies: High-Redshift - galaxies: individual (J1252-5224-4599) - Galaxies: Starburst
Fig. 2 : BD38 = [BIR2003] J1252-5224-4599, LBG with z = 4.695 is [AOI2004] 2, LBG composite = SAS-LBG Q0000-D6 with z = 2.96 ?
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