A Massive Disk Galaxy at z > 3 along the Line of Sight of QSO 1508+5714

Abstract

We have obtained deep images in the BVRIJHKs bands of the field centered on QSO 1508+5714 5714 (Z_em = 4.28) with the Suprime-Cam, FOCAS, and MOIRCS cameras on Subaru telescope. We report here on the detection of a B-dropout galaxy, which is 3.5'' north-west of the QSO sightline. A photometric redshift analysis is presented to complement the color selection. Given the photometric properties of this object (M = -22.2, making L ≈ 3L^*, if placed at its photometric redshift, z ∼ 3.5), as well as the Sérsic index (n ∼ 1) derived from a 2-D imaging decomposition of the HST WFPC2 image taken with the I_F814 filter, the identified system is consistent with a massive disk galaxy at z > 3. If confirmed, it would be one of the most distant massive disk galaxies known so far.