{
  "id": "2109.10929",
  "version": "v1",
  "published": "2021-09-22T18:00:17.000Z",
  "updated": "2021-09-22T18:00:17.000Z",
  "title": "The inner density profile of an elliptical galaxy at z=1.15 from gravitational lensing",
  "authors": [
    "H. R. Stacey",
    "C. M. O'Riordan",
    "S. Vegetti",
    "D. M. Powell",
    "M. W. Auger",
    "G. Despali"
  ],
  "comment": "8 pages, 5 figures; submitted to MNRAS",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "The density profiles of lensing galaxies are typically parameterised by singular power-law models with a logarithmic slope close to isothermal ($\\zeta=2$). This is sufficient to fit the lensed emission near the Einstein radius but may not be sufficient when extrapolated to smaller or larger radii if the large-scale density profile is more complex. Here, we consider a broken power-law model for the density profile of an elliptical galaxy at $z=1.15$ using observations with the Atacama Large (sub-)Millimetre Array of the strong gravitational lens system SPT0532$-$50. This is the first application of such a model to real data. We find the lensed emission is best fit by a density profile that is sub-isothermal ($\\zeta = 1.87^{+0.02}_{-0.03}$) near the Einstein radius and steepens to super-isothermal ($\\zeta = 2.14^{+0.03}_{-0.02}$) at around half the Einstein radius, demonstrating that the lensing data probes the mass distribution inside the region probed by the lensed images. Assuming that a broken power-law is the underlying truth, we find that a single power-law would result in a $10\\pm1$ percent underestimate of the Hubble constant from time-delay cosmography. Our results suggest that a broken power-law could be useful for precision lens modelling and probing the structural evolution of elliptical galaxies.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-09-22T18:00:17.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "elliptical galaxy",
      "inner density profile",
      "broken power-law",
      "einstein radius",
      "strong gravitational lens system spt0532"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 8,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}