{
  "id": "2110.12447",
  "version": "v1",
  "published": "2021-10-24T13:57:59.000Z",
  "updated": "2021-10-24T13:57:59.000Z",
  "title": "Deprojection of X-ray data in galaxy clusters: confronting simulations with observations",
  "authors": [
    "Kartick C Sarkar",
    "Arjun Dey",
    "Prateek Sharma"
  ],
  "comment": "8 figures, 15 pages, submitted to MNRAS. Comments are welcome",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "Numerical simulations with varying realism indicate an emergent principle -- multiphase condensation and large cavity power occur when the ratio of the cooling time to the free-fall time ($t_{\\rm cool}/t_{\\rm ff}$) falls below a threshold value close to 10. Observations indeed show cool-core signatures when this ratio falls below 20-30, but the prevalence of cores with \\tctf~ratio below 10 is rare as compared to simulations. In X-ray observations, we obtain projected spectra from which we have to infer radial gas density and temperature profiles. Using idealized models of X-ray cavities and multiphase gas in the core and 3-D hydro jet-ICM simulations, we quantify the biases introduced by deprojection based on the assumption of spherical symmetry in determining $t_{\\rm cool}/t_{\\rm ff}$. We show that while the used methods are able to recover the $t_{\\rm cool}/t_{\\rm ff}$ ratio for relaxed clusters, they have an uncertainty of a factor of $2-3$ in systems containing large cavities ($\\gtrsim 20$ kpc). We also show that the mass estimates from these methods, in absence of X-ray spectra close to the virial radius, suffer from a degeneracy between the virial mass ($M_{200}$) and the concentration parameter ($c$) in the form of $M_{200}\\: c^2 \\approx$ constant. Additionally, lack of soft-X-ray ($\\lesssim 0.5$ keV) coverage and poor spatial resolution make us overestimate min($t_{\\rm cool}/t_{\\rm ff}$) by a factor of few in clusters with min($t_{\\rm cool}/t_{\\rm ff}$) $\\lesssim 5$. This bias can largely explain the lack of cool-core clusters with min($t_{\\rm cool}/t_{\\rm ff}$) $\\lesssim 5$.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-10-24T13:57:59.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "x-ray data",
      "galaxy clusters",
      "confronting simulations",
      "observations",
      "deprojection"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 15,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}