Mysterious Globular Cluster System of the Peculiar Massive Galaxy M85

We present a study on the stellar population and kinematics of globular clusters (GCs) in the peculiar galaxy M85. We obtain optical spectra of 89 GCs at 8 kpc < R < 160 kpc using the MMT/Hectospec. We divide them into three groups, blue/green/red GCs (B/G/RGCs), with their (g − i)0 colors. Al...

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Bibliographic Details
Published in:The Astrophysical journal 2020-11, Vol.903 (2), p.110
Main Authors: Ko, Youkyung, Lee, Myung Gyoon, Park, Hong Soo, Sohn, Jubee, Lim, Sungsoon, Hwang, Narae, Park, Byeong-Gon
Format: Article
Language:English
Subjects:
Astrophysics
Dark matter
Dispersion
Elliptical galaxies
Galactic clusters
Galaxies
Globular clusters
Globular star clusters
Kinematics
Lenticular galaxies
Peculiar galaxies
Rotating disks
Rotation
Stars & galaxies
Subpopulations
Velocity
Virgo Cluster
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Summary:We present a study on the stellar population and kinematics of globular clusters (GCs) in the peculiar galaxy M85. We obtain optical spectra of 89 GCs at 8 kpc < R < 160 kpc using the MMT/Hectospec. We divide them into three groups, blue/green/red GCs (B/G/RGCs), with their (g − i)0 colors. All GC subpopulations have mean ages of about 10 Gyr, but showing differences in metallicities. The BGCs and RGCs are the most metal-poor ([Z/H] ∼ −1.49) and metal-rich ([Z/H] ∼ −0.45), respectively, and the GGCs are in between. We find that the inner GC system exhibits a strong overall rotation that is entirely due to a disklike rotation of the RGC system. The BGC system shows little rotation. The GGCs show kinematic properties clearly distinct among the GC subpopulations, having higher mean velocities than the BGCs and RGCs and being aligned along the major axis of M85. This implies that the GGCs have an origin different from the other GC subpopulations. The rotation-corrected velocity dispersion of the RGC system is much lower than that of the BGC system, indicating the truncation of the red halo of M85. The BGCs have a flat velocity dispersion profile out to R = 67 kpc, reflecting the dark matter extent of M85. Using the velocity dispersion of the BGC system, we estimate the dynamical mass of M85 to be 3.8 × 1012 M . We infer that M85 has undergone merging events lately, resulting in the peculiar kinematics of the GC system.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/abbd39