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

Cibinel, A, Le Floc'h, E, Perret, V, Bournaud, F, Daddi, E, Pannella, M, Elbaz, D, Amram, P and Duc, P-A (2015) A physical approach to the identification of high-z mergers: morphological classification in the stellar mass domain. The Astrophysical Journal, 805 (2). ISSN 1538-4357

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At z gsim 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 109.8–1010.6 M⊙ 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 $z\simeq 2$ 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 > 109.4 M⊙. We find that a combination of the asymmetry AMASS and M20, MASS indices measured on the stellar mass maps can efficiently identify real (major) mergers with lesssim20% 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).

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Depositing User: Anna Cibinel
Date Deposited: 17 Jul 2015 15:59
Last Modified: 05 Aug 2019 13:06
URI: http://sro.sussex.ac.uk/id/eprint/55415

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