A physical approach to the identification of high-Z mergers: Morphological classification in the stellar mass domain

Journal Article · Mon Jun 01 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/805/2/181· OSTI ID:22883129

Cibinel, A. ^[1]; Floc’h, E. Le; Bournaud, F.; Daddi, E.; Elbaz, D.; Duc, P. -A. ^[2]; Perret, V. ^[3]; Pannella, M. ^[4]

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1. Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH (United Kingdom)
2. CEA Saclay, DSM/Irfu/Service d’Astrophysique, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France)
3. Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science and Physik Institut, University of Zürich, 190 Winterthurestrasse, Zürich 8057 (Switzerland)
4. Universitäts-Sternwarte München, Scheinerstr. 1, D-81679 München (Germany)

At z ≳ 1, the distinction between merging and “normal” star-forming galaxies based on single band morphology is often hampered by the presence of large clumps which result in a disturbed, merger-like appearance even in rotationally supported disks. In this paper we discuss how a classification based on canonical, non-parametric structural indices measured on resolved stellar mass maps, rather than on single-band images, reduces the misclassification of clumpy but not merging galaxies. We calibrate the mass-based selection of mergers using the MIRAGE hydrodynamical numerical simulations of isolated and merging galaxies which span a stellar mass range of 10{sup 9.8}–10{sup 10.6} M{sub ⊙} and merger ratios between 1:1–1:6.3. These simulations are processed to reproduce the typical depth and spatial resolution of observed Hubble Ultra Deep Field (HUDF) data. We test our approach on a sample of real z≃2 galaxies with kinematic classification into disks or mergers and on ∼100 galaxies in the HUDF field with photometric/spectroscopic redshift between 1.5 ≤ z ≤ 3 and M > 10{sup 9.4} M{sub ⊙}. We find that a combination of the asymmetry A{sub MASS} and M{sub 20, MASS} indices measured on the stellar mass maps can efficiently identify real (major) mergers with ≲20% contamination from clumpy disks in the merger sample. This mass-based classification cannot be reproduced in star-forming galaxies by H-band measurements alone, which instead result in a contamination from clumpy galaxies which can be as high as 50%. Moreover, we find that the mass-based classification always results in a lower contamination from clumpy galaxies than an H-band classification, regardless of the depth of the imaging used (e.g., CANDELS versus HUDF).

• OSTI ID: 22883129
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 805; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CLASSIFICATION
COMPUTERIZED SIMULATION
GALAXIES
INTERACTIONS
MASS
RED SHIFT
SPATIAL RESOLUTION
STARS