{
  "id": "1804.07730",
  "version": "v1",
  "published": "2018-04-20T17:13:32.000Z",
  "updated": "2018-04-20T17:13:32.000Z",
  "title": "HI observations of Sextans A and B with the SKA pathfinder KAT-7",
  "authors": [
    "Brenda Namumba",
    "Claude Carignan",
    "Sean Passmoor"
  ],
  "comment": "15 pages, 19 figures, Accepted for publication in MNRAS",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "HI observations of the Local Group dwarf irregular galaxies Sextans A and B, obtained with the Karoo Array Telescope (KAT-7) are presented. The KAT-7 wide field of view and excellent surface brightness sensitivity allows us to verify the true HI extent of the galaxies. We derive HI extends of 30$^{\\prime}$ and 20$^{\\prime}$ and total HI fluxes of 181 $\\pm$ 2.0 Jy.km.s$^{-1}$ and 105 $\\pm$ 1.4 Jy.km.s$^{-1}$ for Sextans A and B respectively. This result shows clearly the overestimate of the HI extent and total flux of 54$^{\\prime}$ and 264 Jy.km.s$^{-1}$ reported for Sextans A using the Effelsberg observations. Tilted ring models allow us to derive the rotation curves (RCs) of Sextans A and B out to 550$^{\\prime \\prime}$ ($\\sim$ 3.5 kpc) and 650$^{\\prime \\prime}$ ($\\sim$ 4 kpc) respectively. The RCs of the two galaxies are seen to decline in the outer parts. The dark matter distribution in Sextans A is better described by the pseudo-isothermal halo model when a M/L ratio of 0.2 is used. For Sextans B, the mass model fits are not as good but again an isothermal sphere with a M/L of 0.2 represents best the data. Using the MOdified Newtonian Dynamics (MOND), better fits are obtained when the constant a$_{0}$ is allowed to vary. The critical densities for gravitational instabilities are calculated using the Toomre-$Q$ and cloud-growth based on shear criterion. We find that in regions of star formation, the cloud growth criterion based on shear explains better the star formation in both Sextans A and B.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2018-04-20T17:13:32.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "hi observations",
      "ska pathfinder",
      "group dwarf irregular galaxies sextans",
      "local group dwarf irregular galaxies",
      "star formation"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 15,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}