The Intrinsic Ellipticity of Spiral Disks
David R. Andersen (MPIA), Matthew A. Bershady (UW-Madison)

TL;DR
This study measures the intrinsic ellipticity distribution of spiral galaxy disks using combined kinematic and photometric data, revealing a mostly circular shape with some ellipticity affecting galaxy scaling relations.
Contribution
It provides the first direct measurement of intrinsic ellipticities for face-on spiral disks using combined velocity and imaging data.
Findings
Disks have a log-normal ellipticity distribution with mean 0.06.
Ellipticities range from 0 (circular) to 0.2.
Disk ellipticity contributes to Tully-Fisher scatter.
Abstract
We have measured the distribution of intrinsic ellipticities for a sample of 28 relatively face-on spiral disks. We combine H-alpha velocity fields and R and I-band images to determine differences between kinematic and photometric inclination and position angles, from which we estimate intrinsic ellipticities of galaxy disks. Our findings suggest disks have a log-normal distribution of ellipticities (mean epsilon =0.06) and span a range from epsilon= 0 (circular) to epsilon=0.2. We are also able to construct a tight Tully-Fisher relation for our face-on sample. We use this to assess the contribution of disk ellipticity on the observed Tully-Fisher scatter.
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Taxonomy
TopicsGalaxies: Formation, Evolution, Phenomena · Plant Water Relations and Carbon Dynamics
