New H i Observations Toward the NGC 5055 Galaxy Group with FAST

This is the authors' abstract. We don't add key points for this paper.

We report a new high-sensitivity H i mapping observation of the NGC 5055 galaxy group over an area of 1.°5 × 0.°75 with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Our observation reveals that the warped H i disk of NGC 5055 is more extended than what was previously observed by WSRT, out to 23.′9 (61.7 kpc). The total H i mass of NGC 5055 is determined to be ∼1.1 × 10 10 M ⊙ . We identified three H i clouds with H i masses of the order of ∼10 7 M ⊙ at the southeastern edge of the H i disk, as well as a candidate high-velocity cloud with an H i mass of (1.2 ± 0.5) × 10 6 M ⊙ to the north of NGC 5055. The H i content of UGCA 337 is robustly detected for the first time by the FAST observations. It has a narrow H i linewidth of W 50 = 17.4 ± 3.8 km s −1 with a total H i mass of (3.5 ± 0.3) × 10 6 M ⊙ . Comparing the gas content and g − r color of UGCA 337 with typical low-mass dwarf galaxies, UGCA 337 appears relatively gas-poor despite its blue color. This suggests that UGCA 337 may have undergone gas stripping in the past. We also analyzed the possible origin of the diffuse H i clouds located at the outskirts of NGC 5055, and speculate that they might be the remnant features of a merger event in the past.