Star-formation at z=4.7 in the environment of the QSO BR1202-07

Abstract

We present here the spectrum of the galaxy companion to the z=4.7 quasar BR1202-0725, in the optical range 6000-9000 A, corresponding to 1050-1580 A rest-frame. We detect a strong Lya emission line at z=4.702, with an integrated flux of 2x10^{-16} ergs/cm^2/s, and a UV continuum longward of the Lya emission at a flux level of 3x10^{-19}ergs/cm^2/s/A. We fail to detect any CIV[1550] emission with a 3 sigma upper limit of 3x10^{-17} ergs/cm^2/s $. We show that the ratio between Lya and continuum intensity and the absence of a strong CIV emission imply that the UV continuum radiation is the result of an intense star-formation activity rather than of a reprocessing of the QSO flux. The total estimated SFR of this z=4.7 star-forming region is about 15-54 Msun/yr, depending on the IMF and the metallicity. The present data suggest that the Lya emission has a velocity and spatial structure, with possible velocity differences of about 500 km/s on scales of few kpc. These velocity patterns may be a signature of collapsing or merging phenomena in the QSO and its environment, as expected from current models of galaxy formation at high z.

14 pages + 2 figures. To appear on AJ, April 1998

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Cited by in corpus (11)

• Photometric redshifts and selection of high redshift galaxies in the NTT and Hubble Deep Fields
• The Fall of the Quasar Population
• High resolution imaging of molecular line emission from high redshift QSOs
• Molecular gas at high redshift: jet-induced star formation?
• A Detection of [CII] line emission in the z=4.7 QSO BR1202-0725
• BR1202-0725: An Extreme Multiple Merger at z = 4.7
• Herschel/PACS far-infrared photometry of two z>4 quasars
• Hints of star fomation at z>6: the chemical abundances of the DLA system in the QSO BRI 1202-0725 (z_abs = 4.383)
• Subaru Deep Spectroscopy of a Star-forming Companion Galaxy of BR 1202-0725 at $z=4.7$
• New Constraints on the Molecular Gas in the Prototypical HyLIRGs BRI1202-0725 & BRI1335-0417
• K band SINFONI spectra of two $z\sim 5$ SMGs: upper limits to the un-obscured star formation from [O II] optical emission line searches