Spatially Resolved Stellar Kinematics of the Ultra-diffuse Galaxy Dragonfly 44. I. Observations, Kinematics, and Cold Dark Matter Halo Fits
Abstract
We present spatially resolved stellar kinematics of the well-studied ultra-diffuse galaxy (UDG) Dragonfly 44, as determined from 25.3 hr of observations with the Keck Cosmic Web Imager. The luminosity-weighted dispersion within the half-light radius is σ_(1/2) = 33^(+3)_(−3) km s^(−1), lower than what we had inferred before from a DEIMOS spectrum in the Hα region. There is no evidence for rotation, with V_(max)/ σ < 0.12 (90% confidence) along the major axis, in possible conflict with models where UDGs are the high-spin tail of the normal dwarf galaxy distribution. The spatially averaged line profile is more peaked than a Gaussian, with Gauss–Hermite coefficient h_4 = 0.13 ± 0.05. The mass-to-light ratio (M/L) within the effective radius is (M_(dyn)/L_I)(
Additional Information
© 2019 The American Astronomical Society. Received 2019 March 31; revised 2019 May 25; accepted 2019 June 5; published 2019 July 30. This paper is dedicated to Mariella Silvia, a young woman with a passion for astronomy who has inspired us with her fortitude. Support from HST grant HST-GO-14643 and NSF grants AST-1312376, AST-1616710, AST-1518294, and AST-1613582 is gratefully acknowledged. This work was partially supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. 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. We are grateful to the staff of Keck Observatory, and in particular Luca Rizzi, for their excellent support and help. The authors recognize 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. A.J.R. is a Research Corporation for Science Advancement Cottrell Scholar.Attached Files
Published - van_Dokkum_2019_ApJ_880_91.pdf
Submitted - 1904.04838.pdf
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Additional details
- Eprint ID
- 97547
- Resolver ID
- CaltechAUTHORS:20190731-100739159
- HST-GO-14643
- NASA Hubble Fellowship
- AST-1312376
- NSF
- AST-1616710
- NSF
- AST-1518294
- NSF
- AST-1613582
- NSF
- W. M. Keck Foundation
- Cottrell Scholar of Research Corporation
- Created
-
2019-07-31Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)