Our GMRT (Giant Metrewave Radio Telescope) H I observations of the ultra-diffuse galaxy (UDG) UGC 2162, projected ∼ 300 kpc from the centre of the M 77 group, reveal it to a have an extended H I disc (RH I/R25 ∼ 3.3) with a moderate rotational velocity (Vrot ∼ 31 km s−1). This Vrotis in line with that of dwarf galaxies with similar H I mass. We estimate an Mdyn of ∼1.14 × 109 M within the galaxy’s RH I ∼ 5.2 kpc. Additionally, our estimates of M200 for the galaxy from NFW models are in the range of 5.0–8.8 × 1010 M. Comparing UGC 2162 to samples of UDGs with H I detections show it to have amongst the smallest Re with its MH I/M∗ being distinctly higher and g – i colour slightly bluer than typical values in those samples. We also compared H I and dark matter (DM) halo properties of UGC 2162 with dwarf galaxies in the LITTLE THINGS sample and find its DM halo mass and profile are within the range expected for a dwarf galaxy. While we were unable to determine the origin of the galaxy’s present-day optical form from our study, its normal H I rotation velocity in relation to its H I mass, H I morphology, environment, and dwarf mass DM halo ruled out some of the proposed ultra-diffuse galaxy formation scenarios for this galaxy.
Bibliographical noteFunding Information:
We thank the staff of the GMRT who have made these observations possible. The GMRT is operated by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. TS acknowledges support by Fundac¸ão para a Ciência e a Tecnologia (FCT) through national funds (UID/FIS/04434/2013), FCT/MCTES through national funds (PIDDAC) by this grant UID/FIS/04434/2019 and by FEDER through COMPETE2020 (POCI-01-0145-FEDER-007672). TS also acknowledges the support by the fellowship SFRH/BPD/103385/2014 funded by FCT (Portugal) and POPH/FSE (EC). TS additionally acknowledges support from DL 57/2016/CP1364/CT0009. This work was supported by FCT/MCTES through national funds (PIDDAC) by this grant PTDC/FIS-AST/29245/2017. Support for this work was provided by the National Research Foundation of Korea to the Center for Galaxy Evolution Research (No. 2010-0027910) and NRF grant no. 2018R1D1A1B07048314. This research has made use of the NED that is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has made use of the SDSS. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS web site is http: //www.sdss.org/. This research made use of APLPY, an open-source plotting package for PYTHON hosted at http://aplpy.github.com (Robitaille & Bressert 2012). The Parkes telescope is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science