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Galaxy And Mass Assembly (GAMA): refining the local galaxy merger rate using morphological information

Casteels, KRV and Conselice, CJ and Bamford, SP and Salvador-Sole, E and Norberg, PR and Agius, NK and Baldry, IK and Brough, S and Brown, MJI and Drinkwater, MJ and Driver, SP and Graham, AW and Bland-Hawthorn, J and Hopkins, AM and Kelvin, LS and Lopez-Sanchez, AR and Loveday, J and Robotham, ASG and Vazquez-Mata, JA (2014) Galaxy And Mass Assembly (GAMA): refining the local galaxy merger rate using morphological information. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 445 (2). pp. 1157-1169. ISSN 0035-8711

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Abstract

We use the Galaxy And Mass Assembly (GAMA) survey to measure the local Universe mass dependent merger fraction and merger rate using galaxy pairs and the CAS structural method, which identifies highly asymmetric merger candidate galaxies. Our goals are to determine which types of mergers produce highly asymmetrical galaxies, and to provide a new measurement of the local galaxy major merger rate. We examine galaxy pairs at stellar mass limits down to M∗ = 108M⊙ with mass ratios of <100:1 and line of sight velocity differences of _V < 500 km s−1. We find a significant increase in mean asymmetries for projected separations less than the sum of the individual galaxy’s Petrosian 90 radii. For systems in major merger pairs with mass ratios of <4:1 both galaxies in the pair show a strong increase in asymmetry, while in minor merger systems (with mass ratios of >4:1) the lower mass companion becomes highly asymmetric, while the larger galaxy is much less affected. The fraction of highly asymmetric paired galaxies which have a major merger companion is highest for the most massive galaxies and drops progressively with decreasing mass. We calculate that the mass dependent major merger fraction is fairly constant at _ 1.3 − 2% between 109.5 < M∗ < 1011.5M⊙, and increases to _ 4% at lower masses. When the observability time scales are taken into consideration, the major merger rate is found to approximately triple over the mass range we consider. The total co-moving volume major merger rate over the range 108.0 < M∗ < 1011.5M⊙ is (1.2 ± 0.5) × 10−3 h3 70 Mpc−3 Gyr−1.

Item Type: Article
Additional Information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record "Galaxy And Mass Assembly (GAMA): refining the local galaxy merger rate using morphological information", MNRAS, v.445(2), pp.1157-69 is available online at: http://dx.doi.org/10.1093/mnras/stu1799
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: OXFORD UNIV PRESS
Related URLs:
Date Deposited: 06 Jul 2015 11:21
Last Modified: 08 Sep 2015 13:41
DOI or Identification number: 10.1093/mnras/stu1799
URI: http://researchonline.ljmu.ac.uk/id/eprint/1520

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