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arXiv 1208.5682astro-ph.CO
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伪椭圆NFW晶状体模型的有效范围

Domain of validity for pseudo-elliptical NFW lens models

H. S. Dúmet-Montoya, G. B. Caminha, M. Makler

摘要:

在引力透镜的应用中,常使用椭圆势(伪椭圆)模型。然而,它们通常会在某些区域导致非物理质量分布。在本文中,我们重新审视了伪椭圆Navarro-Frenk-White(PNFW)模型的物理局限性,在很宽的范围内的潜在的椭圆度参数ε和特征收敛κ_s集中在切向临界曲线附近的质量分布的行为,切向弧预计将形成。我们调查的形状的质量分布在这个区域和负收敛的存在。我们得到了一个映射从PNFW的NFW模型与椭圆质量分布(ENFW),并提供拟合公式连接两个模型的参数。我们使用“无限小圆源近似”比较这些模型的弧截面。我们发现PNFW模型非常适合在比以前预期的更大的ε - κ_s参数空间上模拟椭圆质量分布。特别地,对于小的κ_s,允许大到ε ~ 0.65的值。然而,如果我们要求PNFW模型再现ENFW阱的弧形截面,则椭圆率受到更多限制。我们还发现,负收敛区域发生在远离弧形成区域,因此不应该是一个问题的研究与引力弧。PNFW模型和ENFW模型的映射的有效性域的确定可能会影响使用PNFW模型的逆建模的镜头和快速电弧模拟。

英文摘要:

Models with elliptical potentials (pseudo-elliptical) are often used in gravitational lensing applications. Nevertheless, they generally lead to nonphysical mass distributions in some regions. In this paper we revisit the physical limitations of the pseudo-elliptical Navarro-Frenk-White (PNFW) model, for a broad range of the potential ellipticity parameter ε and characteristic convergence κ_s focusing on the behavior of the mass distribution close to the tangential critical curve, where tangential arcs are expected to be formed. We investigate the shape of the mass distribution on this region and the presence of negative convergence. We obtain a mapping from the PNFW to the NFW model with elliptical mass distribution (ENFW) and provide fitting formulae for connecting the parameters of both models. We compare the arc cross section for these models using the "infinitesimal circular source approximation". We find that the PNFW model is well-suited to model an elliptical mass distribution on a larger ε - κ_s parameter space than previously expected. In particular values as large as ε ~ 0.65 are allowed for small κ_s. However, if we require the PNFW model to reproduce the arc cross section of the ENFW well, the ellipticity is more restricted. We also find that the negative convergence regions occur far from the arc formation region and should therefore not be a problem for studies with gravitational arcs. The determination of a domain of validity for the PNFW model and the mapping to ENFW models could have implications for the use of PNFW models for the inverse modeling of lenses and for fast arc simulations.

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