Morphological Parameters of a Spitzer Survey of Stellar Structure in Galaxies

Holwerda, B. W.; Muñoz-Mateos, J.-C.; Pirzkal, N.; Bosma, A.; Athanassoula, E.; Knapen, J. H.; Ho, L. C.; Erroz-Ferrer, S.; Zaritsky, D.; Gadotti, D. A.; Laine, J.; Salo, H.; Mizusawa, T.; Laurikainen, E.; Kim, T.; Seibert, M.; Menéndez-Delmestre, K.; Gil de Paz, A.; Sheth, K.; Meidt, S.; Comerón, S.; Regan, M. W.; Laine, S.; Hinz, J. L.
Bibliographical reference

The Astrophysical Journal, Volume 781, Issue 1, article id. 12, 19 pp. (2014).

Advertised on:
1
2014
Number of authors
24
IAC number of authors
2
Citations
31
Refereed citations
30
Description
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 20), ellipticity (E), and the Gini index of the second-order moment (GM ) 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 82) and M 20 for normal galaxies. M 20 can be used to classify galaxies into earlier and later types (i.e., to separate spirals from irregulars). Several criteria using these parameters 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 20, GM , C, and M 20, respectively, select outliers in morphological parameter space, but each selects different subsets of galaxies. Two criteria (GM > 0.6, G >–0.115 × M 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 20.
Related projects
Project Image
Spiral Galaxies: Evolution and Consequences
Our small group is well known and respected internationally for our innovative and important work on various aspects of the structure and evolution of nearby spiral galaxies. We primarily use observations at various wavelengths, exploiting synergies that allow us to answer the most pertinent questions relating to what the main properties of
Johan Hendrik
Knapen Koelstra