DIISC-I: The Discovery of Kinematically Anomalous HI Clouds in M 100

Abstract

We report the discovery of two kinematically anomalous atomic hydrogen (HI) clouds in M 100 (NGC 4321), which was observed as part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey in HI 21 cm at 3.3 km s −1 spectroscopic and 44 ×30 spatial resolution using the Karl G. Jansky Very Large Array a) . These clouds were identified as structures that show significant kinematic offsets from the rotating disk of M100. The velocity offsets of 40 km s −1 observed in these clouds are comparable to the offsets seen in intermediatevelocity clouds (IVCs) in the circumgalactic medium (CGM) of the Milky Way and nearby galaxies. We find that one anomalous cloud in M 100 is associated with star-forming regions detected in Hα and far-ultraviolet imaging. Our investigation shows that anomalous clouds in M 100 may originate from multiple mechanisms, such as star formation feedback-driven outflows, ram-pressure stripping, and tidal interactions with satellite galaxies. Moreover, we do not detect any cool CGM at 38.8 kpc from the center of M 100, giving an upper limit of N(HI) ≤ 1.7×10 13 cm −2 (3σ). Since M 100 is in the Virgo cluster, the non-existence of neutral/cool CGM is a likely pathway for turning it into a red galaxy.