skip to main content

Title: Morphological parameters of a Spitzer survey of stellar structure in galaxies

The morphology of galaxies can be quantified to some degree using a set of scale-invariant parameters. Concentration (C), asymmetry (A), smoothness (S), the Gini index (G), the relative contribution of the brightest pixels to the second-order moment of the flux (M {sub 20}), ellipticity (E), and the Gini index of the second-order moment (G{sub M} ) have all been applied to morphologically classify galaxies at various wavelengths. Here, we present a catalog of these parameters for the Spitzer Survey of stellar structure in Galaxies, a volume-limited, near-infrared (NIR) imaging survey of nearby galaxies using the 3.6 and 4.5 μm channels of the Infrared Array Camera on board the Spitzer Space Telescope. Our goal is to provide a reference catalog of NIR quantified morphology for high-redshift studies and galaxy evolution models with enough detail to resolve stellar mass morphology. We explore where normal, non-interacting galaxies—those typically found on the Hubble tuning fork—lie in this parameter space and show that there is a tight relation between concentration (C {sub 82}) and M {sub 20} for normal galaxies. M {sub 20} can be used to classify galaxies into earlier and later types (i.e., to separate spirals from irregulars). Several criteria using these parametersmore » exist to select systems with a disturbed morphology, i.e., those that appear to be undergoing a tidal interaction. We examine the applicability of these criteria to Spitzer NIR imaging. We find that four relations, based on the parameters A and S, G and M {sub 20}, G{sub M} , C, and M {sub 20}, respectively, select outliers in morphological parameter space, but each selects different subsets of galaxies. Two criteria (G{sub M} > 0.6, G > –0.115 × M {sub 20} + 0.384) seem most appropriate to identify possible mergers and the merger fraction in NIR surveys. We find no strong relation between lopsidedness and most of these morphological parameters, except for a weak dependence of lopsidedness on concentration and M {sub 20}.« less
 [1] ; ; ;  [2] ; ; ; ;  [3] ; ;  [4] ;  [5] ; ;  [6] ;  [7] ;  [8] ; ; ;  [9] ;  [10] ;  [11] more »; « less
  1. ESTEC, Keplerlaan 1, 2200-AG Noordwijk (Netherlands)
  2. National Radio Astronomfy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
  3. Astronomy Division, Department of Physical Sciences, FI-90014 University of Oulu, P.O. Box 3000, Oulu (Finland)
  4. Max-Planck-Institut für Astronomie/Königstühl 17, D-69117 Heidelberg (Germany)
  5. Spitzer Science Center, Mail Stop 220-6, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
  6. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
  7. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  8. Departamento de Astrofísica, Universidad Complutense de Madrid, E-28040 Madrid (Spain)
  9. The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
  10. European Southern Observatory, Casilla 19001, Santiago 19 (Chile)
  11. Instituto de Astrofísica de Canarias, Vía Láctea s/n E-38205 La Laguna (Spain)
Publication Date:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 781; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States