Speaker
Description
To understand the formation of massive red spirals, we select optically red spirals with $M_{*}> 10^{10.5} M_{☉}$ based on the u-r color-stellar mass diagram from SDSS DR7 and compared the environment of these spirals with different NUV-r colors. All optically red galaxies have similar properties in the center, i.e., no star formation activity, similar bulge size, central velocity dispersion and star formation history. While most NUV-r blue spirals have odd morphologies, i.e., ring, shell or tidal disruption, and have more NUV flux at 1-2 R$_e$ than NUV-r red spirals. Meanwhile, NUV-r blue spirals have larger disks and higher HI fraction. These suggest star-forming activity due to the disruption of gas in the outer parts of NUV-r blue spirals. The gas disruption may originate from the environment. About half of the NUV-r red spirals are satellites, while ~85% NUV-r blue galaxies are central or isolated galaxies. This implies that NUV-r red spirals may be more susceptible to the environment to lose their gas and quenched. While NUV-r blue galaxies would possess more gas and be triggered star formation in the outskirts due to disruption or interaction.
