Euclid: A complete Einstein ring in NGC 6505 | Astronomy & Astrophysics (A&A)

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Table 2.

Comparison of strong lensing models.

Additions	θ_E	γ	q	ϕ_L	\|γ_ext\|	m₄	λ_s	Δlnε
γ_ext+m₄	$2 \overset{″}{.} 500$ $2{{\overset{\prime\prime}{.}}}500$	2.03	0.702	143.3	0.027	0.012	203	133.3
γ_ext+m₄+GC	$2 \overset{″}{.} 500$ $2{{\overset{\prime\prime}{.}}}500$	2.13	0.684	143.3	0.019	0.018	198	128.9
γ_ext	$2 \overset{″}{.} 503$ $2{{\overset{\prime\prime}{.}}}503$	1.97	0.714	143.7	0.032	–	181	95.9
m₄	$2 \overset{″}{.} 500$ $2{{\overset{\prime\prime}{.}}}500$	2.33	0.637	144.6	–	0.037	175	78.6
None	$2 \overset{″}{.} 496$ $2{{\overset{\prime\prime}{.}}}496$	2.26	0.698	144.6	–	–	148	0.0

Notes. The deflector is an elliptical power-law (EPL) to which we add either an external shear, γ_ext, or an m = 4 multipole representing boxiness, or both. One model includes both angular additions plus a mass component for the assumed globular cluster (GC). The columns give the maximum a posteriori values for: the Einstein radius, θ_E, the power-law slope, γ, the axis ratio, q, the position angle, ϕ_L, the absolute strength of the external shear component, |γ_ext|, the strength of the m = 4 multipole, m₄, the source regularisation strength λ_s, and the difference in log-evidence versus the simplest model. The number of significant figures given indicates the mean uncertainty on that parameter across the different models (see also Sect. 4.3).

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