Ionized and cold gas components in low surface brightness galaxy AGC 102004

• DOI: 10.48550/arxiv.2407.18530
• Publication Date: 2024-08-01
• Authors: Tian-Wen Cao; Zi-Jian Li; Pei-Bin Chen; Chun-Yi Zhang; Gaspar Galaz; Cheng Cheng; Qingzheng Yu; Venu M. Kalari; Junfeng Wang; Hong Wu
• Keywords: Molecular gas; Galaxy mergers; FOS: Physical sciences; Astrophysics; 530; Astrophysics - Astrophysics of Galaxies; 01 natural sciences; QB460-466; Astrophysics of Galaxies (astro-ph.GA); Metallicity; 0103 physical sciences; Low surface brightness galaxies

Abstract We present the integral field spectroscopic observations of ionized gas (Hα 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 Hα shows an anomalous distribution in the northwestern (NW) disk. The Hα spectrum is well-fitted by two Gaussian components, and the weak Gaussian component is dominated by the anomalous Hα in the NW disk. The Gaussian fit center of Hα 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]λ6583/Hα 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 × 107 M ⊙ with X CO = 3.02 × 1020 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.