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

TL;DR
This paper reports the discovery of an early-type galaxy with an inner star-forming disk, providing direct evidence of gas-rich merging as a formation process for low-mass ETGs, which is rare and transient.
Contribution
It presents the first direct observational evidence linking gas-rich merging to the formation of low-mass early-type galaxies.
Findings
Inner disk shows ongoing star formation.
Outer and inner regions have distinct kinematics.
Presence of tidal features indicating recent merging.
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…
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