{
  "id": "astro-ph/9802026",
  "version": "v1",
  "published": "1998-02-03T01:38:12.000Z",
  "updated": "1998-02-03T01:38:12.000Z",
  "title": "The Cosmological Parameters H_0 and Omega_0",
  "authors": [
    "R. Brent Tully"
  ],
  "comment": "10 pages with 2 figures encapsulated in the .ps file",
  "categories": [
    "astro-ph"
  ],
  "abstract": "The first section discusses a recalibration of the luminosity-linewidth technique and its use in a determination of H_0. The recalibration introduces (i) new cluster calibration data, (ii) new corrections for reddening as a function of inclination, and (iii) a new zero-point calibration using 13 galaxies with distances determined via the cepheid period-luminosity method. It is found that H_0=82+/-16 km/s/Mpc (95% confidence). The second section concerns a dynamic measurement of Omega_0. The non-linear Least Action method can be used to reconstruct the orbits galaxies have followed to reach their current positions. The three free parameters of the models are M/L, age of the Universe, and a measure of the possible extended nature of dark halos compared with the distribution of light. Models are constrained by 900 observed distances. Best chi^2 fits are for models with M/L values consistent with Omega_0=0.25+/-0.2. The concept of `antibiasing' is introduced in an attempt to reconcile this low estimate of Omega_0 with the results from linear analyses. It is argued that M/L values in elliptical-rich regions are a factor of 7 larger than those in spiral-rich regions. Hence, whereas it is commonly thought that there is the bias that mass is more extended than light, there may be a cosmologically important regime where there is the antibias of mass more concentrated than light. This possibility makes the inferrance of Omega_0 from beta unclear.",
  "revisions": [
    {
      "version": "v1",
      "updated": "1998-02-03T01:38:12.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "cosmological parameters",
      "cepheid period-luminosity method",
      "second section concerns",
      "m/l values consistent",
      "first section discusses"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 453755
    }
  }
}