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2014ApJS..210....6L - Astrophys. J., Suppl. Ser., 210, 6 (2014/January-0)
Toward a better understanding of the distance scale from RR Lyrae variable stars: a case study for the inner halo globular cluster NGC 6723.
LEE J.-W., LOPEZ-MORALES M., HONG K., KANG Y.-W., POHL B.L. and WALKER A.
Abstract (from CDS):
We present BV photometry for 54 variables in the metal-rich inner halo globular cluster NGC 6723. With the discovery of new RR Lyrae variables (RRLs), we obtain ab> = 0.541±0.066 and c> = 0.292±0.030 day, n(c)/n(ab+c) = 0.167, and int= 15.459±0.055. We carry out the Fourier decomposition analysis and obtain [Fe/H]ZW= -1.23±0.11 and E(B - V) = 0.063±0.015 for NGC 6723. By calibrating the zero point from the recent absolute trigonometric parallax measurements for RR Lyr, we derive the revised MV(RR)-[Fe/H] relation, providing MV(RR) = 0.52 at [Fe/H] = -1.50 and (m - M)0= 18.54 for the Large Magellanic Cloud, in excellent agreement with others. We obtain (m - M)0= 14.65±0.05, equivalent to a distance from the Sun of 8.47±0.17 kpc, for NGC 6723 from various distance measurement methods using RRLs. We find that RRLs in NGC 6723 do not have magnitude dependency on the radial distance because there is not a severe degree of apparent crowdedness. Finally, we show that a relation exists between the degree of photometric contamination and the apparent crowdedness of the central region of globular cluster systems, |µ - µr|∝ logρcd2. The use of this relation can play a significant role in mitigating the discrepancy in establishing a cosmic distance scale using RRLs in resolved stellar populations in near-field cosmology.
Abstract Copyright: ∼
Journal keyword(s): globular clusters: individual: NGC 6723 - stars: distances - stars: horizontal-branch - stars: variables: RR Lyrae
Nomenclature: Table 3: [LLH2014] NVNN (Nos NV1-NV22) = Cl* NGC 6723 SAW VNN N=15 (Nos V33-V47) added.
Simbad objects: 67
