Ionized and Cold Gas Components in Low Surface Brightness Galaxy AGC 102004

• Published in: The Astrophysical journal Vol. 971; no. 2; pp. 181 - 189
• Main Authors: Cao, Tian-Wen, Li, Zi-Jian, Chen, Pei-Bin, Zhang, Chun-Yi, Galaz, Gaspar, Cheng, Cheng, Yu, Qingzheng, Kalari, Venu M., Wang, Junfeng, Wu, Hong
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.08.2024; IOP Publishing
• Subjects: Cold gas; Galaxies; Galaxy distribution; Galaxy mergers; H alpha line; Low surface brightness galaxies; Metallicity; Molecular gas; Molecular gases; Noise levels; Spectroscopic observation; Surface brightness; Velocity distribution
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ad6848

We present the integral field spectroscopic observations of ionized gas (H α and [N II ]) using the PCWI, along with deep CO(2–1) observations by the ‵ U ¯ ‵ u ¯ receiver on JCMT for AGC 102004. The velocity field of H α shows an anomalous distribution in the northwestern (NW) disk. The H α spectrum is well-fitted by two Gaussian components, and the weak Gaussian component is dominated by the anomalous H α in the NW disk. The Gaussian fit center of H α emission is offset by +24.2 km s −1 from the systemic velocity obtained from the H i emission. We derive the gas-phase metallicity, 12+log(O/H), using [N II ] λ 6583/H α ratio as a proxy. The mean value of 12+log(O/H) is 8.30 ± 0.19 over the whole galaxy. The metallicity in the outer disk is lower than the detection limit of 7.72, indicating the metallicity gradient exists in AGC 102004. We speculate a minor/mini-merger event could have happened to the NW disk. CO(2–1) emission has nondetection in AGC 102004, reaching a noise level of 0.33 mK smoothed to 30 km s −1 . The upper limit of molecular gas mass in AGC 102004 is 2.1 × 10 7 M ⊙ with X CO = 3.02 × 10 20 cm −2 (K km s −1 ) −1 . The M H 2 / M H I corr of AGC 102004 is lower than 0.0037 and lower than that of normal galaxies.