Year: 2013
Type: article
Abstract: We present the first strong-lensing (SL) analysis of the galaxy cluster ACT-CL J0102−4915 (El Gordo), in recent HST /ACS images, revealing a prominent strong lens at a redshift of z = 0.87. This finding adds to the already-established unique properties of El Gordo: it is the most massive, hot, X-ray luminous, and bright Sunyaev–Zeldovich effect cluster at z ≳ 0.6, and the only "bullet"-like merging cluster known at these redshifts. The lens consists of two merging massive clumps, where, for a source redshift of z s ∼ 2, each clump exhibits only a small, separate critical area, with a total area of 0.69 ± 0.11□' over the two clumps. For a higher source redshift, z s ∼ 4, the critical curves of the two clumps merge together into one bigger and very elongated lens (axis ratio ≃ 5.5), enclosing an effective area of 1.44 ± 0.22□'. The critical curves continue expanding with increasing redshift so that for high-redshift sources ( z s ≳ 9) they enclose an area of ∼1.91 ± 0.30□' (effective θ e ≃ 46 8 ± 3 7) and a mass of 6.09 ± 1.04 × 10 14 M ☉ . According to our model, the area of high magnification (μ > 10) for such high-redshift sources is ≃1.2□', and the area with μ > 5 is ≃2.3□', making El Gordo a compelling target for studying the high-redshift universe. We obtain a strong lower limit on the total mass of El Gordo, ≳ 1.7 × 10 15 M ☉ from the SL regime alone, suggesting a total mass of roughly M 200 ∼ 2.3 × 10 15 M ☉ . Our results should be revisited when additional spectroscopic and HST imaging data are available.
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2042536772