A photometric and kinematic analysis of UDG1137+16 (dw1137+16): probing ultradiffuse galaxy formation in a group environment

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The dominant physical formation mechanism(s) for ultradiffuse galaxies (UDGs) is still poorly understood. Here, we combine new, deep imaging from the Jeanne Rich Telescope with deep integral field spectroscopy from the Keck II telescope to investigate the formation of UDG1137+16 (dw1137+16). Our new analyses confirm both its environmental association with the low density UGC 6594 group, along with its large size of 3.3 kpc and status as a UDG. The new imaging reveals two distinct stellar components for UDG1137+16, indicating that a central stellar body is surrounded by an outer stellar envelope undergoing tidal interaction. Both the components have approximately similar stellar masses. From our integral field spectroscopy, we measure a stellar velocity dispersion within the half-light radius (15 ± 4 km s^(−1)) and find that UDG1137+16 is similar to some other UDGs in that it is likely dark matter dominated. Incorporating literature measurements, we also examine the current state of UDG observational kinematics. Placing these data on the central stellar velocity dispersion–stellar mass relation, we suggest there is little evidence for UDG1137+16 being created through a strong tidal interaction. Finally, we investigate the constraining power current dynamical mass estimates (from stellar and globular cluster velocity dispersions) have on the total halo mass of UDGs. As most are measured within the half-light radius, they are unable to accurately constrain UDG total halo masses.
© 2021 The Author(s). We thank the anonymous referee for their careful consideration of our work and for providing useful comments to improve upon it. We thank R. Turner and A. Romanowsky for insightful conversations throughout the creation of this work. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Tthe authors wish to recognise and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. JSG acknowledges financial support received through a Swinburne University Postgraduate Research Award through out the creation of this work. DAF thanks the ARC for financial support via DP160101608. AFM has received financial support through the Post-doctoral Junior Leader Fellowship Programme from “La Caixa” Banking Foundation (LCF/BQ/LI18/11630007). JPB gratefully acknowledges support from National Science foundation grants AST-1518294 and AST-1616598. B.T.D acknowledges supports from a Spanish postdoctoral fellowship “Ayudas 1265 para la atracción del talento investigador. Modalidad 2: jóvenes investigadores.” funded by Comunidad de Madrid under grant number 2016-T2/TIC-2039 and from the grant “High-resolution, multiband analysis of galaxy centers (HiMAGC)” with reference number PR65/19-22417 financed by Comunidad de Madrid and Universidad Complutense de Madrid. JR acknowledge financial support from the grants AYA2015-65973-C3-1-R and RTI2018-096228-B-C31 (MINECO7FEDER. UE), as well as from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709).
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