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arXiv · 2410.20583

Do strong bars exhibit strong non-circular motions?

Taehyun Kim·Dimitri A. Gadotti·Yun Hee Lee·Carlos López-Cobá·Woong-Tae Kim·Minjin Kim·Myeong-gu Park
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Abstract

Galactic bars induce characteristic motions deviating from pure circular rotation, known as non-circular motions. As bars are non-axisymmetric structures, stronger bars are expected to show stronger non-circular motions. However, this has not yet been confirmed by observations. We use a bisymmetric model to account for the stellar kinematics of 14 barred galaxies obtained with the Multi-Unit Spectroscopic Explorer (MUSE) and characterize the degree of bar-driven non-circular motions. For the first time, we find tight relations between the bar strength (bar ellipticity and torque parameter) and the degree of stellar non-circular motions. We also find that bar strength is strongly associated with the stellar radial velocity driven by bars. Our results imply that stronger bars exhibit stronger non-circular motions. Non-circular motions beyond the bar are found to be weak, comprising less than 10% of the strength of the circular motions. We find that galaxies with a boxy/peanut (B/P) bulge exhibit a higher degree of non-circular motions and higher stellar radial velocity compared to galaxies without a B/P bulge, by 30-50%. However, this effect could be attributed to the presence of strong bars in galaxies with a B/P feature in our sample, which would naturally result in higher radial motions, rather than to B/P bulges themselves inducing stronger radial motions. More observational studies, utilizing both stellar and gaseous kinematics on statistically complete samples, along with numerical studies, are necessary to draw a comprehensive view of the impact that B/P bulges have on bar-driven non-circular motions.

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Taehyun Kim, Dimitri A. Gadotti, Yun Hee Lee, Carlos López-Cobá, Woong-Tae Kim, Minjin Kim, Myeong-gu Park. 2024-10-27. Do strong bars exhibit strong non-circular motions?. https://arxiv.org/abs/2410.20583

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