Modeling the Initial Conditions of Interacting Galaxy Pairs Using Identikit

Abstract

We develop and test an automated technique to model the dynamics of interacting galaxy pairs. We use Identikit (Barnes & Hibbard 2009, Barnes 2011) as a tool for modeling and matching the morphology and kinematics of the interacting pairs of equal-mass galaxies. In order to reduce the effect of subjective human judgement, we automate the selection of phase-space regions used to match simulations to data, and we explore how selection of these regions affects the random uncertainties of parameters in the best-fit model. In this work, we use an independent set of GADGET SPH simulations as input data to determine the systematic bias in the measured encounter parameters based on the known initial conditions of these simulations. We test both cold gas and young stellar components in the GADGET simulations to explore the effect of choosing HI vs. H$\alpha$ as the line of sight velocity tracer. We find that we can group the results into tests with good, fair, and poor convergence based on the distribution of parameters of models close to the best-fit model. For tests with good and fair convergence, we rule out large fractions of parameter space and recover merger stage, eccentricity, pericentric distance, viewing angle, and initial disc orientations within 3$\sigma$ of the correct value. All of tests on prograde-prograde systems have either good or fair convergence. The results of tests on edge-on discs are less biased than face-on tests. Retrograde and polar systems do not converge and may require constraints from regions other than the tidal tails and bridges.

18 pages, 13 figures, 3 Tables, Accepted for publication in MNRAS

References in corpus (5)

• Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache Point Observatory
• Direct cosmological simulations of the growth of black holes and galaxies
• The effect of galaxy mass ratio on merger--driven starbursts
• Science with ASKAP - the Australian Square Kilometre Array Pathfinder
• Identikit 1: A Modeling Tool for Interacting Disk Galaxies

Cited by in corpus (4)

• Enhanced atomic gas fractions in recently merged galaxies: quenching is not a result of post-merger gas exhaustion
• Galaxy Zoo: Mergers - Dynamical Models of Interacting Galaxies
• Dynamics and Shocks from H$\alpha$ Emission of Nearby Galaxy Mergers
• HI vs. H$\alpha$ - Comparing the Kinematic Tracers in Modeling the Initial Conditions of the Mice