Kavli Affiliate: Michael D. Gladders
| First 5 Authors: Joseph F. V. Allingham, Joseph F. V. Allingham, , ,
| Summary:
Massive galaxy clusters act as prominent strong-lenses. Due to a combination
of observational biases, cluster evolution and lensing efficiency, most of the
known cluster lenses lie typically at $z_lsim0.2-0.7$, with only a few
prominent examples at higher redshifts. Here we report a first strong-lensing
analysis of the massive galaxy cluster SPT-CL J0546-5345 at a redshift
$z_l=1.07$. This cluster was first detected through the Sunyaev-Zel’dovich
effect, with a high estimated mass for its redshift of $M_200,c = (7.95 pm
0.92) times 10^14,M_odot$. Using recent JWST/NIRCam and archival HST
imaging, we identify at least 10 secure and 6 candidate sets of multiply imaged
background galaxies, which we use to constrain the mass distribution in the
cluster. We derive effective Einstein radii of $theta_E= 18.1 pm 1.8 ”$
for a source at $z_s=3$, and $theta_E= 27.9 pm 2.8 ”$ for a source at
$z_s=9$. The total projected mass within a $200$ kpc radius around the
strong-lensing region is $M(<200,mathrmkpc) = (1.9 pm 0.3) times
10^14,M_odot$. While our results rely on photometric redshifts warranting
spectroscopic follow-up, this central mass resembles that of the Hubble
Frontier Fields clusters – although SPT-CL J0546-5345 is observed when the
Universe was $sim 3-4$ Gyr younger. Amongst the multiply-imaged sources, we
identify a hyperbolic-umbilic-like configuration, and, thanks to its point-like
morphology, a possible Active Galactic Nucleus (AGN). If confirmed
spectroscopically, it will add to just a handful of other quasars and AGN known
to be multiply lensed by galaxy clusters.
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