Day 1221

Friday.

1702.05090
A Very Large ($\theta_{E} gtrsim40$") strong gravitational lens selected with the Sunyaev-Zel'dovich Effect: PLCK G287.0+32.9 (z=0.38)
Zitrin et al

Since galaxy clusters sit at the high-end of the mass function, the number of galaxy clusters both massive and concentrated enough to yield particularly large Einstein radii uses useful constraints on cosmo and structure formation models.  To date, less than a handful of clusters are known to have Einstein radii exceeding ~40" (for a source at z_s~2, nominally).  Here, report an addition to that list of the SZ selected cluster, PLCK G287.0+32.9 (z=0.38), the second-highest SZ-mass (M500) cluster from the Planck catalog.  Present the first strong lensing analysis of the cluster, identifying 20 sets of multiply-imaged galaxies and candidates in new Hubble Space Telescope data, including a long, l~22" giant arc, as well as a quadruply-imaged, apparently bright (magnified to J_F110S=25.3 AB), likely high-redshift dropout galaxy at z_phot=6.90 [6.13==8.43] (95% CL).  The analysis reveals a very large critical area (1.55 arcmin2, z_s~2), corresponding to an effective Einstein radius of theta_E~42".  The model suggests the critical area will expand to 2.58 arcmin2 (effective theta_E~54") for sources at z_s~10.  The work adds to recent efforts to model very massive clusters towards the approaching launch of the JWST, in order to identify the most useful cosmic lenses for studying the early Universe.  Spectroscopic redshifts for the multiply-imaged galaxies and additional HST data will be useful for refining the lens model and verifying the nature of the z~7 dropout.