We report 1.7 GHz Very Long Baseline Interferometry ( VLBI ) observations of IRAS F10214+4724 , a lensed z = 2.3 obscured quasar with prodigious star formation .
We detect what we argue to be the obscured active nucleus with an effective angular resolution of < 50 pc at z = 2.3 .
The S _ { 1.7 } = 210 \mu Jy ( 9- \sigma ) detection of this unresolved source is located within the HST rest-frame ultraviolet/optical arc , however , \gtrsim 100 milli-arcseconds northward of the arc centre of curvature .
This leads to a source plane inversion that places the European VLBI Network detection to within milli-arcseconds of the modelled cusp caustic , resulting in a very large magnification ( \mu \sim 70 ) , over an order of magnitude larger than the CO ( 1 \rightarrow 0 ) derived magnification of a spatially resolved JVLA map , using the same lens model .
We estimate the quasar bolometric luminosity from a number of independent techniques and with our X-ray modelling find evidence that the AGN may be close to Compton-thick , with an intrinsic bolometric luminosity \log _ { 10 } ( \langle L _ { bol,QSO } \rangle / { L } _ { \odot } ) = 11.34 \pm 0.27 dex .
We make the first black hole mass estimate of IRAS F10214+4724 and find \log _ { 10 } ( M _ { BH } / \mathrm { M _ { \odot } } ) = 8.36 \pm 0.56 which suggests a low black hole accretion rate ( \lambda = \dot { M } / \dot { M } _ { Edd } \sim 3 \pm ^ { 7 } _ { 2 } percent ) .
We find evidence for a M _ { BH } / M _ { spheroid } ratio that is 1-2 orders of magnitude larger than that of submillimetre galaxies ( SMGs ) at z \sim 2 .
At face value , this suggests IRAS F10214+4724 has undergone a different evolutionary path compared to SMGs at the same epoch .
A primary result of this work is the demonstration that emission regions of differing size and position can undergo significantly different magnification boosts ( > 1 dex ) and therefore distort our view of high-redshift , gravitationally lensed galaxies .