NAOC Open IR  > 太阳物理研究部
Newberg, Heidi Jo1; Willett, Benjamin A.1; Yanny, Brian2; Xu, Yan3
AbstractWe use recent Sloan Extension for Galactic Understanding and Exploration (SEGUE) spectroscopy and the Sloan Digital Sky Survey (SDSS) and SEGUE imaging data to measure the sky position, distance, and radial velocities of stars in the tidal debris stream that is commonly referred to as the "Orphan Stream." We fit orbital parameters to the data and find a prograde orbit with an apogalacticon, perigalacticon, and eccentricity of 90 kpc, 16.4 kpc, and e = 0.7, respectively. Neither the dwarf galaxy UMa II nor the Complex A gas cloud has velocities consistent with a kinematic association with the Orphan Stream. It is possible that Segue-1 is associated with the Orphan Stream, but no other known Galactic clusters or dwarf galaxies in the Milky Way lie along its orbit. The detected portion of the stream ranges from 19 to 47 kpc from the Sun and is an indicator of the mass interior to these distances. There is a marked increase in the density of Orphan Stream stars near (l, b) = (253 degrees, 49 degrees), which could indicate the presence of the progenitor at the edge of the SDSS data. If this is the progenitor, then the detected portion of the Orphan Stream is a leading tidal tail. We find blue horizontal branch (BHB) stars and F turnoff stars associated with the Orphan Stream. The turnoff color is (g - r)(0) = 0.22. The BHB stars have a low metallicity of [Fe/H](WBG) = -2.1. The orbit is best fit to a halo potential with a halo plus disk mass of about 2.6 x 10(11) M(circle dot), integrated to 60 kpc from the Galactic center. Our fits are done to orbits rather than full N-body simulations; we show that if N-body simulations are used, the inferred mass of the galaxy would be slightly smaller. Our best fit is found with a logarithmic halo speed of v(halo) = 73 +/- 24 km s(-1), a disk+bulge mass of M(R < 60 kpc) = 1.3 x 10(11) M(circle dot), and a halo mass of M(R < 60 kpc) = 1.4 x 10(11) M(circle dot). However, we can find similar fits to the data that use a Navarro-Frenk-White halo profile or that have smaller disk masses and correspondingly larger halo masses. Distinguishing between different classes of models requires data over a larger range of distances. The Orphan Stream is projected to extend to 90 kpc from the Galactic center, and measurements of these distant parts of the stream would be a powerful probe of the mass of the Milky Way.
KeywordGalaxy: Halo Galaxy: Structure Stars: Kinematics And Dynamics
Indexed BySCI
WOS IDWOS:000274417500004
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Cited Times:84[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Affiliation1.Rensselaer Polytech Inst, Dept Phys Appl Phys & Astron, Troy, NY 12180 USA
2.Fermilab Natl Accelerator Lab, Batavia, IL 60510 USA
3.Chinese Acad Sci, Natl Astron Observ China, Beijing, Peoples R China
Recommended Citation
GB/T 7714
Newberg, Heidi Jo,Willett, Benjamin A.,Yanny, Brian,et al. THE ORBIT OF THE ORPHAN STREAM[J]. ASTROPHYSICAL JOURNAL,2010,711(1):32-49.
APA Newberg, Heidi Jo,Willett, Benjamin A.,Yanny, Brian,&Xu, Yan.(2010).THE ORBIT OF THE ORPHAN STREAM.ASTROPHYSICAL JOURNAL,711(1),32-49.
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