Spectroscopic Confirmation of the Fifth Image of SDSS J1004+4112 and Implications for the MBH-σ* Relation at z = 0.68

We present the results of deep spectroscopy for the central region of the cluster lens SDSSJ1004$+$4112 with the Subaru Telescope. A secure detection of an emission line of the faint blue stellar object (component E) near the center of the brightest cluster galaxy (G1) confirms that it is the central fifth image of the lensed quasar system. In addition, we measured the stellar velocity dispersion of G1 to be σ_*= 352±13kms⁻¹. We combined these results to obtain constraints on the mass MBH of the putative black hole (BH) at the center of the inactive galaxy G1, and hence on the MBH-σ _* relation at the lens redshift zₗ= 0.68. From detailed mass modeling, we placed an upper limit on the black hole mass, MBH<2.1×10¹⁰M_ at the 1σ level (<3.1×10¹⁰M_ at 3σ), which is consistent with black hole masses expected from the local and redshift-evolved MBH-σ _* relations, MBH~ 10⁹-10¹⁰M_.