STRUCTURAL PARAMETERS FOR 10 HALO GLOBULAR CLUSTERS IN M33

Journal Article · Fri May 15 04:00:00 EDT 2015 · Astronomical Journal (Online)

DOI:https://doi.org/10.1088/0004-6256/149/5/157· OSTI ID:22520204

Ma, Jun ^[1]

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1. Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

In this paper, we present the properties of 10 halo globular clusters (GCs) with luminosities L ≃ 5–7 × 10{sup 5} L{sub ⊙} in the Local Group galaxy M33 using images from the Hubble Space Telescope WFPC2 in the F555W and F814W bands. We obtained the ellipticities, position angles, and surface brightness profiles for each GC. In general, the ellipticities of the M33 sample clusters are similar to those of the M31 clusters. The structural and dynamical parameters are derived by fitting the profiles to three different models combined with mass-to-light ratios (M/L values) from population-synthesis models. The structural parameters include core radii, concentration, half-light radii, and central surface brightness. The dynamical parameters include the integrated cluster mass, integrated binding energy, central surface mass density, and predicted line of sight velocity dispersion at the cluster center. The velocity dispersions of the four clusters predicted here agree well with the observed dispersions by Larsen et al. The results here showed that the majority of the sample halo GCs are better fitted by both the King model and the Wilson model than the Sérsic model. In general, the properties of the clusters in M33, M31, and the Milky Way fall in the same regions of parameter spaces. The tight correlations of cluster properties indicate a “fundamental plane” for clusters, which reflects some universal physical conditions and processes operating at the epoch of cluster formation.

• OSTI ID: 22520204
• Journal Information: Astronomical Journal (Online), Journal Name: Astronomical Journal (Online) Journal Issue: 5 Vol. 149; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BINDING ENERGY
BRIGHTNESS
CONCENTRATION RATIO
CORRELATIONS
LUMINOSITY
MASS
MILKY WAY
STAR CLUSTERS
STAR MODELS
SURFACES
TELESCOPES
VISIBLE RADIATION