University of Surrey

Test tubes in the lab Research in the ATI Dance Research

A Hubble Space Telescope Study of the Enigmatic Milky Way Halo Globular Cluster Crater

Weisz, DR, Koposov, SE, Dolphin, AE, Belokurov, V, Gieles, M, Mateo, ML, Olszewski, EW, Sills, A and Walker, MG (2016) A Hubble Space Telescope Study of the Enigmatic Milky Way Halo Globular Cluster Crater The Astrophysical Journal: an international review of astronomy and astronomical physics, 822 (1). pp. 1-10.

[img]
Preview
Text
A Hubble Space Telescope Study of the Enigmatic Milky Way Halo Globular Cluster Crater.pdf - Version of Record
Available under License : See the attached licence file.

Download (1MB) | Preview
[img]
Preview
Text (licence)
SRI_deposit_agreement.pdf
Available under License : See the attached licence file.

Download (33kB) | Preview

Abstract

We analyze the resolved stellar populations of the faint stellar system, Crater, based on deep optical imaging taken with the Advanced Camera for Surveys aboard the Hubble Space Telescope. The HST-based colormagnitude diagram (CMD) of Crater extends 4 magnitudes below the oldest main sequence turnoff, providing excellent leverage on Crater’s physical properties. Structurally, we find that Crater has a half-light radius of 20 pc and shows no evidence for tidal distortions. We model the CMD of Crater under the assumption of it being a simple stellar population and alternatively by solving for its full star formation history. In both cases, Crater is well-described by a simple stellar population with an age of 7.5 Gyr, a metallicity of [M/H] -1.65, a total stellar mass of M? 1e4 M , a luminosity of MV -5:3, located at a distance of d 145 kpc, with modest uncertainties in these properties due to differences in the underlying stellar evolution models. We argue that the sparse sampling of stars above the turnoff and sub-giant branch are likely to be 1.0-1.4 M binary star systems (blue stragglers) and their evolved descendants, as opposed to intermediate age main sequence stars. Confusion of these populations highlights a substantial challenge in accurately characterizing sparsely populated stellar systems. Our analysis shows that Crater is not a dwarf galaxy, but instead is an unusually young cluster given its location in the Milky Way’s very outer stellar halo. Crater is similar to SMC cluster Lindsay 38, and its position and velocity are in good agreement with observations and models of the Magellanic stream debris, suggesting it may have accreted from the Magellanic Clouds. However, its age and metallicity are also in agreement with the age-metallicity relationships of lower mass dwarf galaxies such as Leo I or Carina. Despite uncertainty over its progenitor system, Crater appears to have been incorporated into the Galaxy more recently than z 1 (8 Gyr ago), providing an important new constraint on the accretion history of the Milky Way.

Item Type: Article
Subjects : Physycs
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
AuthorsEmailORCID
Weisz, DRUNSPECIFIEDUNSPECIFIED
Koposov, SEUNSPECIFIEDUNSPECIFIED
Dolphin, AEUNSPECIFIEDUNSPECIFIED
Belokurov, VUNSPECIFIEDUNSPECIFIED
Gieles, MUNSPECIFIEDUNSPECIFIED
Mateo, MLUNSPECIFIEDUNSPECIFIED
Olszewski, EWUNSPECIFIEDUNSPECIFIED
Sills, AUNSPECIFIEDUNSPECIFIED
Walker, MGUNSPECIFIEDUNSPECIFIED
Date : 2 May 2016
Identification Number : 10.3847/0004-637X/822/1/32
Copyright Disclaimer : © 2016. The American Astronomical Society. All rights reserved.
Uncontrolled Keywords : Galaxy: halo, Globular clusters: general, Hertzsprung–Russell and C–M diagrams
Related URLs :
Depositing User : Symplectic Elements
Date Deposited : 25 Jul 2016 14:19
Last Modified : 03 Aug 2016 14:21
URI: http://epubs.surrey.ac.uk/id/eprint/811365

Actions (login required)

View Item View Item

Downloads

Downloads per month over past year


Information about this web site

© The University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom.
+44 (0)1483 300800