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Dark matter and HI in ultra-diffuse galaxy UGC 2162

C. Sengupta, T. C. Scott, A. C. Wonders, A. Chung, O. I. Wong

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 ( ∼ 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 ∼ 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 – icolour 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.

galaxies: individual: UGC 2162, galaxies: kinematics and dynamics, galaxies: ISM, galaxies: haloes, radio lines: galaxies

Monthly Notices of the Royal Astronomical Society
Volume 488, Issue 3, Page 3222
2019 September

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia