Washington Photometry of the Globular Cluster System of NGC 4472.I.Analysis of the Metallicities

Details Washington Photometry of the Globular Cluster System of NGC 4472.I.Analysis of the Metallicities Washington Photometry of the Globular Cluster System of NGC 4472.I.Analysis of the Metallicities

Apr 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996aj....111.1529g&link_type=abstract

Astronomical Journal v.111, p.1529

Astronomy and Astrophysics

Astronomy

149

Galaxies: Individual: Ngc 4472, Globular Clusters: General, Galaxies: Formation, Galaxies: Photometry

Scientific paper

We present integrated Washington CT_1_ photometry of the globular cluster system of NGC 4472 (M49), the brightest galaxy in the Virgo cluster. The photometry is deep, reaching beyond T_1_~R ~25 and allows us to investigate metallicities in the cluster system at an unprecedented level. We first examine the age, horizontal branch morphology and metallicity sensitivities of the integrated (C-T_1_,) color and reconfirm its utility as an efficient metal abundance index. As for other broadband colors, the index is much more sensitive to metallicity than age for old clusters (~> 10 Gyr), but (C - T_1_) has twice the metallicity sensitivity of (B-V) or (V-I). The metallicity calibration based on data for Galactic globular clusters yields metal abundances that are in good agreement with spectroscopically-derived values for extragalactic clusters as well. The metallicities of some 1800 of the best globular cluster candidates in NGC 4472 (~1/4 of the total in this galaxy) are then derived from this calibration. These values are, on average, internally precise to < 0.15 dex and accurate to ~0.2 dex. This is by far the largest dataset of accurate metal abundances available for any globular cluster system. The median metallicity of the system is [Fe/H]= -0.9+/-0.2 dex, where the error includes all sources of uncertainty in this value. More importantly, the color distribution is clearly bimodal. Assuming the color differences are determined by metallicity, the resulting metallicity distribution is very well-fit by two Gaussians with peaks at [Fe/H]~- 1.3 and -0.1. In addition, the metal-rich clusters are significantly more concentrated to the center of NGC 4472 than their metal-poor counterparts. These results argue strongly for the presence of two distinct cluster populations and thus two distinct epochs and/or mechanisms of cluster formation, and are in agreement with the predictions of the Ashman & Zepf [ApJ, 384,50(1992)] scenario of secondary globular cluster formation in mergers. As expected, there is a large metallicity dispersion in the globular clusters at any radius, amounting to σ ~ 0.7 dex, and the clusters are more metal- poor than the background halo of the galaxy at all radii, by about 0.8 dex on average. The metallicity difference between the globulars and the halo increases with radius. The total cluster system displays a significant radial metallicity gradient of ~0.4 in {DELTA}[Fe/H]/{DELTA} log R, comparable to those uncovered in similar studies of other globular cluster systems. However, most of this gradient appears to be due to the varying radial concentration of the two populations.

Affiliated with

Also associated with

No associations

Rating

Washington Photometry of the Globular Cluster System of NGC 4472.I.Analysis of the Metallicities 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 Washington Photometry of the Globular Cluster System of NGC 4472.I.Analysis of the Metallicities, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Washington Photometry of the Globular Cluster System of NGC 4472.I.Analysis of the Metallicities will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1333729