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arXiv · 2209.07087

On the Origin of the Strong Optical Variability of Emission-line Galaxies

Ruqiu Lin·Zhen-Ya Zheng·Weida Hu·Chunyan Jiang·Xiang Pang·Chenwei Yang·Fang-Ting Yuan·Rahna P. T.·Jian-Guo Wang·Yibo Wang·Ning Jiang·Shuairu Zhu
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Abstract

Emission-line galaxies (ELGs) are crucial in understanding the formation and evolution of galaxies, while little is known about their variability. Here we report the study on the optical variability of a sample of ELGs selected in the COSMOS field, which has narrow-band observations in two epochs separated by $\gtrsim$ 12 years. This sample was observed with Suprime-Cam (SC) and Hyper Suprime-Cam (HSC) on the $Subaru$ telescope in NB816 and $i'/i$ bands, respectively. After carefully removing the wing effect of a narrow-band filter, we check the optical variability in a sample of 181 spectroscopically confirmed ELGs. We find that 0 (0/68) Ha emitters, 11.9% (5/42) [OIII] emitters, and 0 (0/71) [OII] emitters show significant variability ($|\Delta m_{NB}| \geq 3\,\sigma_{\Delta m_{NB,AGN}} = 0.20\, mag$) in the two-epoch narrow-band observations. We investigate the presence of active galactic nucleus (AGN) in this variable ELG (var-ELG) sample with three methods, including X-ray luminosity, mid-infrared activity, and radio-excess. We find zero bright AGN in this var-ELG sample, but cannot rule out the contribution from faint AGN. We find that SNe could also dominate the variability of the var-ELG sample. The merger morphology shown in the HST/F814W images of all the var-ELG sample is in agreement with the enhancement of star formation, i.e., the SNe activity.

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Ruqiu Lin, Zhen-Ya Zheng, Weida Hu, Chunyan Jiang, Xiang Pang, Chenwei Yang, Fang-Ting Yuan, Rahna P. T., Jian-Guo Wang, Yibo Wang, Ning Jiang, Shuairu Zhu. 2022-09-15. On the Origin of the Strong Optical Variability of Emission-line Galaxies. https://doi.org/10.3847/1538-4357/ac9232

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