Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2009-04-04
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
Accepted for Publication in RAA, 12 pages, 1 figure, 2 tables
Scientific paper
Mayall II = G1 is one of the most luminous globular clusters (GCs) in M31. Here, we determine its age and mass by comparing multicolor photometry with theoretical stellar population synthesis models. Based on far- and near-ultraviolet GALEX photometry, broad-band UBVRI, and infrared JHK_s 2MASS data, we construct the most extensive spectral energy distribution of G1 to date, spanning the wavelength range from 1538 to 20,000 A. A quantitative comparison with a variety of simple stellar population (SSP) models yields a mean age that is consistent with G1 being among the oldest building blocks of M31 and having formed within ~1.7 Gyr after the Big Bang. Irrespective of the SSP model or stellar initial mass function adopted, the resulting mass estimates (of order $10^7 M_\odot$) indicate that G1 is one of the most massive GCs in the Local Group. However, we speculate that the cluster's exceptionally high mass suggests that it may not be a genuine GC. We also derive that G1 may contain, on average, $(1.65\pm0.63)\times10^2 L_\odot$ far-ultraviolet-bright, hot, extreme horizontal-branch stars, depending on the SSP model adopted. On a generic level, we demonstrate that extensive multi-passband photometry coupled with SSP analysis enables one to obtain age estimates for old SSPs to a similar accuracy as from integrated spectroscopy or resolved stellar photometry, provided that some of the free parameters can be constrained independently.
de Grijs Richard
Fan Zhanyou
Ma Jun
Rey Soo-Chang
Wu Zhenyu
No associations
LandOfFree
Old stellar population synthesis: New age and mass estimates for Mayall II = G1 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Old stellar population synthesis: New age and mass estimates for Mayall II = G1, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Old stellar population synthesis: New age and mass estimates for Mayall II = G1 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-122930