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Date and Time of the Query: 2019-06-24 T14:47:10 PDT
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For refcode 1999PASP..111..306C:
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Copyright by Astronomical Society of the Pacific. Reproduced by permission
1999PASP..111..306C The Systemic Velocity and Internal Kinematics of the Dwarf Galaxy LGS 3: An Optical Foray beyond the Milky Way KEM H. COOK, MARIO MATEO, EDWARD W. OLSZEWSKI, STEVEN S. VOGT, C. STUBBS, AND A. DIERCKS Received 1998 September 16; accepted 1998 December 9 ABSTRACT. We have obtained radial velocities of three K giants and one faint carbon star in LGS 3, a dwarf companion of M31, based on 12 individual spectra obtained with the HIRES spectrograph on the Keck I telescope. The mean precision of these measurements is 3.8 km s-1. The mean systemic velocity of LGS 3 is -282.2 +/- 3.5 km s^-1^. Monte Carlo simulations that take into account the individual velocity uncertainties and the maximum observed velocity difference reveal that the central velocity dispersion of LGS 3 is in the range 2.6-30.5 km s^-1^, with 95% confidence; the most likely value for the central dispersion is 7.9_- 2.9_^+5.3^ km s^-1^. These results agree with the kinematics of H I gas in LGS 3. This contrasts with the tendency for the gas and stars in other low- luminosity Local Group dwarfs to exhibit distinct spatial and kinematic properties. Taking into account the relative youth of LGS 3, we conclude that the "asymptotic" M/L ratio-the value the galaxy would exhibit if it were composed only of ancient stars-is M/L_V,LGS3_ >= 11 (at a 97.5% confidence level), with a most probable value of 95_-56_^+175^. These values are consistent with the M/L_V_ ratios observed in other well-studied early-type dwarfs of the Local Group. We have also estimated the mass of LGS 3 using modified Newtonian dynamics. These data represent the first moderately high precision optical spectra of giants in a dwarf system beyond the Galactic halo. We suggest future studies that are now feasible to study the dynamics of dwarf galaxies throughout the Local Group and beyond.
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