{
  "id": "2101.05321",
  "version": "v1",
  "published": "2021-01-13T19:56:04.000Z",
  "updated": "2021-01-13T19:56:04.000Z",
  "title": "Composite Bulges -- II. Classical Bulges and Nuclear Discs in Barred Galaxies: The Contrasting Cases of NGC 4608 and NGC 4643",
  "authors": [
    "Peter Erwin",
    "Anil Seth",
    "Victor P. Debattista",
    "Marja Seidel",
    "Kianusch Mehrgan",
    "Jens Thomas",
    "Roberto Saglia",
    "Adriana de Lorenzo-Cáceres",
    "Witold Maciejewski",
    "Maximilian Fabricius",
    "Jairo Méndez-Abreu",
    "Ulrich Hopp",
    "Matthias Kluge",
    "John E. Beckman",
    "Ralf Bender",
    "Niv Drory",
    "Deanne Fisher"
  ],
  "comment": "pdflatex, 29 pages, 22 figures; accepted by MNRAS. Data, code, and Jupyter notebooks available at https://github.com/perwin/n4608-n4643",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We present detailed morphological, photometric, and stellar-kinematic analyses of the central regions of two massive, early-type barred galaxies with nearly identical large-scale morphologies. Both have large, strong bars with prominent inner photometric excesses that we associate with boxy/peanut-shaped (B/P) bulges; the latter constitute ~ 30% of the galaxy light. Inside its B/P bulge, NGC 4608 has a compact, almost circular structure (half-light radius R_e approx. 310 pc, S\\'ersic n = 2.2) we identify as a classical bulge, amounting to 12.1% of the total light, along with a nuclear star cluster (R_e ~ 4 pc). NGC 4643, in contrast, has a nuclear disc with an unusual broken-exponential surface-brightness profile (13.2% of the light), and a very small spheroidal component (R_e approx. 35 pc, n = 1.6; 0.5% of the light). IFU stellar kinematics support this picture, with NGC 4608's classical bulge slowly rotating and dominated by high velocity dispersion, while NGC 4643's nuclear disc shows a drop to lower dispersion, rapid rotation, V-h3 anticorrelation, and elevated h4. Both galaxies show at least some evidence for V-h3 correlation in the bar (outside the respective classical bulge and nuclear disc), in agreement with model predictions. Standard 2-component (bulge/disc) decompositions yield B/T ~ 0.5-0.7 (and bulge n > 2) for both galaxies. This overestimates the true \"spheroid\" components by factors of four (NGC 4608) and over 100 (NGC 4643), illustrating the perils of naive bulge-disc decompositions applied to massive barred galaxies.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-01-13T19:56:04.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "barred galaxies",
      "composite bulges",
      "contrasting cases",
      "4608s classical bulge",
      "prominent inner photometric excesses"
    ],
    "tags": [
      "github project"
    ],
    "note": {
      "typesetting": "PDFLaTeX",
      "pages": 29,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}