Spectroscopic survey of red giants in the small magellanic cloud. I. Kinematics

Jason Harris, Dennis F Zaritsky

Research output: Contribution to journalArticle

100 Citations (Scopus)

Abstract

We present a spectroscopic survey of 2046 red giant stars, distributed over the central 4 kpc × 2 kpc of the Small Magellanic Cloud (SMC). After fitting and removing a small velocity gradient across the SMC (8.3 km s -1 deg -1 oriented at 23°.4 east of north), we measure an rms velocity scatter of 27.5 ± 0.5 km s -1. The line-of-sight velocity distribution is well-characterized by a Gaussian, and the velocity dispersion profile is nearly constant as a function of radius. We find no kinematic evidence of tidal disturbances. Without a high-precision measurement of the SMC's proper motion, it is not possible to constrain its true rotation speed from our measured radial velocity gradient. However, even with conservative assumptions, we find that ν < σ, and hence that the SMC is primarily supported by its velocity dispersion. We find that the shape of the SMC, as measured from the analysis of the spatial distribution of its red giant stars, is consistent with the degree of rotational flattening expected for the range of allowed νi/σ values. As such, the properties of the SMC are consistent with similar low-luminosity spheroidal systems. We conclude that the SMC is primarily a low-luminosity spheroid whose irregular visual appearance is dominated by recent star formation. A simple virial analysis using the measured kinematics implies an enclosed mass within 1.6 kpc of between 1.4 and 1.9 × 10 9M and a less well-constrained mass within 3 kpc of between 2.7 and 5.1 × 10 9 M .

Original languageEnglish (US)
Pages (from-to)2514-2524
Number of pages11
JournalAstronomical Journal
Volume131
Issue number5
DOIs
StatePublished - May 2006

Fingerprint

Magellanic clouds
kinematics
red giant stars
luminosity
gradients
spheroids
proper motion
flattening
radial velocity
line of sight
star formation
spatial distribution
disturbances
velocity distribution
disturbance
radii
profiles

Keywords

  • Galaxies: evolution
  • Galaxies: individual (Small Magellanic Cloud)
  • Galaxies: stellar content
  • Magellanic Clouds

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Spectroscopic survey of red giants in the small magellanic cloud. I. Kinematics. / Harris, Jason; Zaritsky, Dennis F.

In: Astronomical Journal, Vol. 131, No. 5, 05.2006, p. 2514-2524.

Research output: Contribution to journalArticle

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