Clump Giant Distance to the Magellanic Clouds and Anomalous Colors in the Galactic Bulge
Author(s) -
Piotr Popowski
Publication year - 2000
Publication title -
the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.1086/312426
Subject(s) - red clump , physics , astrophysics , distance modulus , bulge , metallicity , rr lyrae variable , photometry (optics) , absolute magnitude , astronomy , gravitational lens , extinction (optical mineralogy) , red giant branch , large magellanic cloud , cosmic distance ladder , stars , globular cluster , gravitational microlensing , galaxy , redshift , optics
I demonstrate that the two unexpected results in the local universe-(1) anomalous intrinsic (V-I&parr0;0 colors of the clump giants and RR Lyrae stars in the Galactic center, and (2) very short distances to the Magellanic Clouds (LMC, SMC) as inferred from clump giants-are connected with each other. The (V-I&parr0;0 anomaly is partially resolved by using the photometry from phase II of the Optical Gravitational Lensing Experiment (OGLE) rather than phase I. The need for V- or I-magnitude-based change in the bulge (V-I&parr0;0 is one option to explain the remaining color discrepancy. Such a change may originate in a coefficient of selective extinction AV&solm0;E&parl0;V-I&parr0; smaller than typically assumed. Application of the (V-I&parr0;0 correction (independent of its source) doubles the slope of the absolute magnitude-metallicity relation for clump giants, so that MI&parl0;RC&parr0;=-0.23+0.19 [Fe/H]. Consequently, the estimates of the clump distances to the LMC and SMC are affected. Udalski's distance modulus of µLMC=18.18+/-0.06 increases to 18.27+/-0.07. The distance modulus to the SMC increases by 0.12 to µSMC=18.77+/-0.08. I argue that a more comprehensive assessment of the metallicity effect on MI&parl0;RC&parr0; is needed.
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