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arXiv · 1808.01730

An early-type galaxy with an inner star-forming disk

Song-lin Li·Yong shi·Yan-mei Chen·Martha Tabor·Dmitry Bizyaev·Jian-hang Chen·Xiao-ling Yu·Long-ji Bing
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Abstract

Early-type galaxies (ETGs) are composed of two distinct populations: high-mass and low-mass, which are likely to be built via gas-poor merging and gas-rich merging/accretion, respectively. However, it is difficult to directly associate low-mass ETGs with gas-rich processes, because currently they are gas poor with no signs of ongoing star formation. We report a discovery of an ETG (SDSS J142055.01+400715.7) with Mstellar=10^10 Msun that offers direct evidence for gas-rich merging as the origin of low-mass ETGs. The integrated properties of the galaxy are consistent with a typical low-mass ETG, but the outer and inner regions show distinct dispersion- and rotation-dominated kinematics, respectively. There are some tidal features surrounding the galaxy. These two facts suggest very recent galaxy merging. Furthermore, the inner disk harbors on-going star formation, indicating the merging to be gas rich. This type of galaxy is rare but it may be a demonstration of the role the transient phase of gas-rich merging plays in making a low-mass ETG.

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Song-lin Li, Yong shi, Yan-mei Chen, Martha Tabor, Dmitry Bizyaev, Jian-hang Chen, Xiao-ling Yu, Long-ji Bing. 2018-08-06. An early-type galaxy with an inner star-forming disk. https://doi.org/10.1093/mnras%2Fsty2008

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