Deep infrared array photometry of globular clusters. 3: M13

Abstract

view Abstract Citations (10) References (55) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Deep Infrared Array Photometry of Globular Clusters. III. M13 Davidge, T. J. ; Harris, W. E. Abstract We have used the California-France-Hawaii Telescope (CFHT) REDEYE infrared camera to obtain deep J and K-prime images of four fields in the globular cluster M13. The composite (K, J-K) color-magnitude diagram (CMD) extends from the upper red giant branch (RGB) to 2 mag below the main-sequence turnoff (MSTO). Selected (Fe/H) approximately -1.6 isochrones from Bergbusch & VandenBerg (1992) and Straniero & Chieffi (1991) are transformed onto the near-infrared observational plane, and these suggest an age for M13 in the range 14-16 Gyr. We emphasize that any effort to estimate ages should be considered as tentative given uncertainties in the input physics; however, these uncertainties notwithstanding, comparisons between the near-infrared isochrones indicate that age differences of order +/- 2 Gyr should be detectable among metal-poor clusters on the (K, J-K) plane. Building on this result, we find that the difference in J-K color between the MSTO and the base of the RGB in M13 is the same as in M4, and we conclude that these clusters have similar ages. This conclusion is verified by comparing (1) the K brightnesses of the MSTO and (2) the morphologies of optical CMDs. Finally, we investigate the mass function of main-sequence stars in M13 with distances between 3 and 6 core radii from the cluster center. The mass functions in the interval 0.55 and 0.8 solar mass are relatively flat, independent of radius. Optical studies at larger radii have found nonzero mass function indices in this same mass interval, and we attribute this radial variation in mass function morphology to dynamical evolution. Publication: The Astrophysical Journal Pub Date: May 1995 DOI: 10.1086/175687 Bibcode: 1995ApJ...445..211D Keywords: Globular Clusters; Infrared Imagery; Main Sequence Stars; Metallicity; Red Giant Stars; Stellar Evolution; Stellar Luminosity; Stellar Mass; Abundance; Brightness; Color-Color Diagram; Color-Magnitude Diagram; Data Reduction; Image Analysis; Astronomy; GALAXY: GLOBULAR CLUSTERS: INDIVIDUAL MESSIER NUMBER: M13; INFRARED: STARS; STARS; EVOLUTION; LUMINOSITY FUNCTION; MASS FUNCTION full text sources ADS | data products SIMBAD (14) Related Materials (6) Part 1: 1994ApJ...423..640D Part 2: 1994ApJ...435..207D Part 4: 1995ApJ...454..545D Part 5: 1996ApJ...462..255D Part 6: 1996ApJ...468..641D Part 7: 1997ApJ...475..584D