Sumo Puff: Tidal debris or disturbed ultra-diffuse galaxy?

Johnny P. Greco, Jenny E. Greene, Adrian M. Price-Whelan, Alexie Leauthaud, Song Huang, Andy D. Goulding, Michael A. Strauss, Yutaka Komiyama, Robert H. Lupton, Satoshi Miyazaki, Masahiro Takada, Masayuki Tanaka, Tomonori Usuda

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


We report the discovery of a diffuse stellar cloud with an angular extent 30, which we term "Sumo Puff" in data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP).While we do not have a redshift for this object, it is in close angular proximity to a post-merger galaxy at redshift z = 0.0431 and is projected within a few virial radii (assuming similar redshifts) of two other ∼L∗ galaxies, which we use to bracket a potential redshift range of 0.0055 < z < 0.0431. The object's light distribution is flat, as characterized by a low Sérsic index (n ∼ 0.3). It has a low central g-band surface brightness of ∼26.4mag arcsec-2, large effective radius of ∼13 (∼11 kpc at z = 0.0431 and ∼1.5 kpc at z = 0.0055), and an elongated morphology (b/a ∼ 0.4). Its red color (g - i ∼ 1) is consistent with a passively evolving stellar population and similar to the nearby post-merger galaxy, and we may see tidal material connecting Sumo Puff with this galaxy. We offer two possible interpretations for the nature of this object: (1) it is an extreme, galaxy-sized tidal feature associated with a recent merger event, or (2) it is a foreground dwarf galaxy with properties consistent with a quenched, disturbed, ultra-diffuse galaxy. We present a qualitative comparison with simulations that demonstrates the feasibility of forming a structure similar to this object in a merger event. Follow-up spectroscopy and/or deeper imaging to confirm the presence of the bridge of tidalmaterial will be necessary to reveal the true nature of this object.

Original languageEnglish (US)
Article numberS19
JournalPublications of the Astronomical Society of Japan
Issue numberSpecial Issue 1
StatePublished - Jan 1 2018

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Dwarf-galaxies
  • Galaxies
  • General-galaxies
  • Interactions


Dive into the research topics of 'Sumo Puff: Tidal debris or disturbed ultra-diffuse galaxy?'. Together they form a unique fingerprint.

Cite this