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Kinematic classifications of local interacting galaxies: implications for the merger/disk classifications at high-z

Hung, Chao-Ling and Rich, Jeffrey A. and Yuan, Tiantian and Larson, Kirsten L. and Casey, Caitlin M. and Smith, Howard A. and Sanders, D. B. and Kewley, Lisa J. and Hayward, Christopher C. (2015) Kinematic classifications of local interacting galaxies: implications for the merger/disk classifications at high-z. Astrophysical Journal, 803 (2). Art. No. 62. ISSN 0004-637X.

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The classification of galaxy mergers and isolated disks is key for understanding the relative importance of galaxy interactions and secular evolution during the assembly of galaxies. Galaxy kinematics as traced by emission lines have been used to suggest the existence of a significant population of high-z star-forming galaxies consistent with isolated rotating disks. However, recent studies have cautioned that post-coalescence mergers may also display disk-like kinematics. To further investigate the robustness of merger/disk classifications based on kinematic properties, we carry out a systematic classification of 24 local (U)LIRGs spanning a range of morphologies: from isolated spiral galaxies, ongoing interacting systems, to fully merged remnants. We artificially redshift the Wide Field Spectrograph observations of these local (U)LIRGs to z = 1.5 to make a realistic comparison with observations at high-z, and also to ensure that all galaxies have the same spatial sampling of ~900 pc. Using both kinemetry-based and visual classifications, we find that the reliability of kinematic classification shows a strong trend with the interaction stage of galaxies. Mergers with two nuclei and tidal tails have the most distinct kinematics compared to isolated disks, whereas a significant population of the interacting disks and merger remnants are indistinguishable from isolated disks. The high fraction of mergers displaying disk-like kinematics reflects the complexity of the dynamics during galaxy interactions. Additional merger indicators such as morphological properties traced by stars or molecular gas are required to further constrain the merger/disk classifications at high-z.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hung, Chao-Ling0000-0002-6879-3639
Rich, Jeffrey A.0000-0002-5807-5078
Larson, Kirsten L.0000-0003-3917-6460
Casey, Caitlin M.0000-0002-0930-6466
Sanders, D. B.0000-0002-1233-9998
Kewley, Lisa J.0000-0001-8152-3943
Hayward, Christopher C.0000-0003-4073-3236
Additional Information:© 2015 American Astronomical Society. Received 24 July 2014, accepted for publication 16 March 2015. Published 16 April 2015. We thank the referee for the great effort with improving the paper. C.-L.H. thanks A. W. Mann for technical help with Figures 1 and 5. C.-L.H. wishes to acknowledge support from NASA grants NNX14AJ61G, NNX11AB02G, and the Smithsonian Predoctoral Fellowship program. K.L.L. and D.B.S. gratefully acknowledge support from NASA grant NNX11AB02G. C.M.C. acknowledges support from a McCue Fellowship through the University of California, Irvine's Center for Cosmology. H.A.S. acknowledges partial support from NASA grants NNX14AJ61G and NNX12AI55G. C.C.H. is grateful to the Klaus Tschira Foundation and Gordon and Betty Moore Foundation for financial support. The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions.
Funding AgencyGrant Number
Smithsonian Astrophysical ObservatoryUNSPECIFIED
Klaus Tschira FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Non-Subject Keywords:galaxies: kinematics and dynamics−galaxies: structure−galaxies: interactions
Issue or Number:2
Record Number:CaltechAUTHORS:20150323-165346748
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55997
Deposited By: Joy Painter
Deposited On:24 Mar 2015 15:45
Last Modified:04 Nov 2019 00:33

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