A Bigger Cloud 9? New HI Observations of the RELHIC Candidate M94-Cloud 9

Abstract

We present new HI observations of the REionization-Limited HI Cloud (RELHIC) candidate, M94-CL9, detected around M94 by Zhou et al. using the Five-hundred-meter Aperture Spherical Telescope (FAST). M94-CL9's HI properties as detected by FAST are consistent with a RELHIC as noted by Benitez-Llambay & Navarro. Our observations with the Robert C. Byrd Green Bank Telescope (GBT) detect greater HI emission in M94-CL9 and result in HI properties that are larger (corrected velocity width, $W_{50,c,t}=35.7\pm 0.6\mathrm{km}{\mathrm{s}}^{-1}$; and integrated flux, $\int \mathrm{Sdv}=0.28\pm 0.04\mathrm{Jy}\cdot \mathrm{km}{\mathrm{s}}^{-1}$) than those found by Zhou et al. but that match those from the FAST All-Sky HI (FASHI) survey. These larger properties do not preclude M94-CL9 from being a RELHIC, but the wider spectral extent and spectral asymmetry reported here may be in tension with predictions of RELHIC properties.

Accepted for publication in RNAAS