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

PASJ: Publications of the Astronomical Society of Japan

Huang, Song¹  Leauthaud, Alexie¹  Lupton, Robert H²  Tanaka, Masayuki²  Miyazaki, Satoshi³  Strauss, Michael A³  Greene, Jenny E³  Greco, Johnny P³  Price-Whelan, Adrian M³  Goulding, Andy D³  Usuda, Tomonori⁴  Komiyama, Yutaka⁵  Takada, Masahiro⁵ 

[1] Department of Astronomy and Astrophysics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA;Department of Astronomy, School of Science, Graduate University for Advanced Studies (SOKENDAI), 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan;Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA;Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), The University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa, Chiba 277-8582, Japan;National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

关键词: galaxies: dwarf;    galaxies: general;    galaxies: interactions;   

DOI  :  10.1093/pasj/psx051

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

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 ∼26.4 mag 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 tidal material will be necessary to reveal the true nature of this object.

【 授权许可】

CC BY