Kavli Affiliate: Jing Wang
| First 5 Authors: Fujia Li, Enci Wang, Ming Zhu, Yingjie Peng, Jing Wang
| Summary:
We analyze the properties of a rare population, the strongly bulge-dominated
early-type galaxies (referred to as sBDEs) with significant HI gas, using the
databases from the FAST All Sky HI survey (FASHI) and the Arecibo Legacy Fast
ALFA (ALFALFA) survey. We select the sBDEs from the Sloan Digital Sky Survey
(SDSS) and cross-match with the FASHI-ALFALFA combined HI sample, resulting in
104 HI-rich sBDEs. These sBDEs tend to have extremely high HI reservoirs, which
is rare in previous studies such as ATLAS$^{3D}$. 70% of the selected sBDEs are
classified as quiescent galaxies, even though they have a large HI reservoir.
We study the properties of these sBDEs from five main aspects: stellar
population, gas-phase metallicity, stacked HI spectra, environment, and
spatially resolved MaNGA data. The majority of HI-rich sBDEs appear to show
lower gas-phase metallicity and are located in significantly lower-density
environments, suggesting an external origin for their HI gas. We find that
star-forming sBDEs exhibit statistically higher star formation efficiency and
slightly older stellar populations compared to normal star-forming galaxies,
suggesting a recent star formation on Gyr-timescale. They also show narrower
and more concentrated HI profiles compared to control star-forming galaxies,
which may explain their higher star formation efficiency.
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