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Abstract
ABSTRACT Large galaxy surveys have demonstrated that galaxy–galaxy mergers can dramatically change the morphologies, star formation rates (SFRs), and metallicities of their constituents. However, most statistical studies have been limited to the measurement of global quantities, through large fibres or integrated colours. In this work, we present the first statistically significant study of spatially resolved star formation and metallicity profiles using integral field spectroscopy, using a sample of ∼20 000 spaxels in 36 visually selected post-merger galaxies from the Mapping Nearby Galaxies at Apache Point Observatory survey. By measuring offsets from SFR and metallicity scaling relations on a spaxel-by-spaxel basis, we are able to quantify where in the galaxy these properties are most affected by the interaction. We find that the SFR enhancements are generally centrally peaked, by a factor of 2.5 on average, in agreement with predictions from simulations. However, there is considerable variation in the SFR behaviour in the galactic outskirts, where both enhancement and suppression are seen. The median SFR remains enhanced by 0.1 dex out to at least 1.9 Re. The metallicity is also affected out to these large radii, typically showing a suppression of ∼−0.04 dex.
Highlights
Simulations have long predicted that galaxy-galaxy interactions can have a dramatic effect on morphologies, star formation rates (SFRs), metallicities and nuclear accretion (e.g. Toomre & Toomre 1972; Barnes & Hernquist 1996; Mihos & Hernquist 1996; Springel, Di Matteo & Hernquist 2005; Di Matteo et al 2008)
The main physical mechanism considered to be responsible for triggering many of the changes during an interaction has been the growth of non-axisymmetric structures, E-mail: mallorythorp@uvic.ca
There is a lot of variation amongst the post-merger gradients, in the galactic outskirts. This is well illustrated by the three example post-mergers presented in Fig. 2 whose ∆ΣSFR gradients are shown in bold in the top panel of Fig. 3
Summary
Simulations have long predicted that galaxy-galaxy interactions can have a dramatic effect on morphologies, star formation rates (SFRs), metallicities and nuclear accretion (e.g. Toomre & Toomre 1972; Barnes & Hernquist 1996; Mihos & Hernquist 1996; Springel, Di Matteo & Hernquist 2005; Di Matteo et al 2008). Simulations have long predicted that galaxy-galaxy interactions can have a dramatic effect on morphologies, star formation rates (SFRs), metallicities and nuclear accretion The sample sizes of most previous galaxy merger MOS and IFU studies have been small. The advent of large IFU surveys is set to revolutionize our ability to spatially map galaxy properties for statistically significant samples of galaxy mergers. Based on ∼100 galaxy mergers selected from the Calar Alto Legacy Integral Field Area (CALIFA, Sanchez et al 2012) survey, Barrera-Ballesteros et al (2015) studied the spatial changes in SFR and metallicity in two aperture bins (see Sanchez et al 2014). Full spatial profiling of SFRs and metallicities in mergers drawn from the new generation of IFU surveys has yet to be realized
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Schedule a callMore From: Monthly Notices of the Royal Astronomical Society: Letters
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