{
  "id": "2004.13435",
  "version": "v1",
  "published": "2020-04-28T11:35:19.000Z",
  "updated": "2020-04-28T11:35:19.000Z",
  "title": "Galaxy mass profiles from strong lensing II: The elliptical power-law model",
  "authors": [
    "Conor M. O'Riordan",
    "Stephen J. Warren",
    "Daniel J. Mortlock"
  ],
  "comment": "11 pages, 8 figures. To be submitted to MNRAS",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We present a systematic analysis of the constraints $\\sigma_\\gamma$ on the mass profile slope $\\gamma$ obtainable when fitting a singular power-law ellipsoid model to a typical strong lensing observation of an extended source. These results extend our previous analysis of circular systems, Paper I. We draw our results from 676 mock observations covering a range of image configurations, each created with a fixed signal to noise ratio $S=100$ in the images. We analyse the results using a combination of theory and a simplified modelling technique which identifies the contribution to the constraints of the individual fluxes and positions in each of the two or four images. The main results are: 1. Regardless of the lens ellipticity, the constraints $\\sigma_\\gamma$ for two image systems are well described by the results of Paper I, transformed to elliptical coordinates; 2. We derive an analytical expression for $\\sigma_\\gamma$ for systems with the source aligned with the axis of the lens; 3. For both two-image systems and aligned systems the slope uncertainties $\\sigma_\\gamma$ are limited by the flux uncertainties; 4. The constraints for off-axis four-image systems are a factor of two to eight better, depending on source size, than for two-image systems, and improve with increasing lens ellipticity. We show that the constraints on $\\gamma$ in these systems derive from the complementary positional information of the images and the flux measurements do not contribute to $\\sigma_\\gamma$. The complementarity improves as the offset of the source from the axis increases, such that the best constraints $\\sigma_\\gamma<0.01$, for $S=100$, occur when the source approaches the caustic.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-04-28T11:35:19.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "galaxy mass profiles",
      "elliptical power-law model",
      "strong lensing",
      "constraints",
      "lens ellipticity"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 11,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}