Harmonizing the RR Lyrae and Clump Distance Scales-Stretching the Short Distance Scale to Intermediate Ranges?

Popowski, P.

Lawrence Livermore National Laboratory

关键词: Calibration;    Magellanic Clouds;    Stars;    71 Classical And Quantum Mechanics, General Physics;   

DOI  :  10.2172/792620
RP-ID  :  UCRL-ID-137445
RP-ID  :  W-7405-Eng-48
RP-ID  :  792620

美国|英语

来源: UNT Digital Library

【 摘 要 】

I explore the consequences of making the RR Lyrae and clump giant distance scales consistent in the solar neighborhood, Galactic bulge and Large Magellanic Cloud (LMC). I employ two major assumptions: (1) that the absolute magnitude -metallicity, M{sub V}(RR) - [Fe/H], relation for RR Lyrae stars is universal, and (2) that absolute I-magnitudes of clump giants, M{sub I}(RC), in Baade's Window can be inferred from the local Hipparcos calibration of clump giants' magnitudes. A comparison between the solar neighborhood and Baade's Window sets M{sub V}(RR) at [Fe/H] = -1.6 in the range (0.59 {+-} 0.05, 0.70 {+-} 0.05), somewhat brighter than the statistical parallax solution. A comparison between Baade's Window and the LMC sets the M{sub I}{sup LMC}(RC) in the range (-0.33 {+-} 0.09, -0.53 {+-} 0.09). The distance modulus to the LMC is {mu}{sup LMC} {element_of} (18.24 {+-} 0.08, 18.44 {+-} 0.07). I argue that the currently available information slightly favors the short distance scale but is insufficient to select the correct solutions with high confidence.