OPTICAL AND INFRARED PHOTOMETRY OF GLOBULAR CLUSTERS IN NGC 1399: EVIDENCE FOR COLOR-METALLICITY NONLINEARITY
- Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC V9E 2E7 (Canada)
- Department of Astronomy and Center for Galaxy Evolution Research, Yonsei University, Seoul 120-749 (Korea, Republic of)
- Department of Astronomy, Peking University, Beijing 100871 (China)
- Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, 7820436 Macul, Santiago (Chile)
We combine new Wide Field Camera 3 IR Channel (WFC3/IR) F160W (H{sub 160}) imaging data for NGC 1399, the central galaxy in the Fornax cluster, with archival F475W (g{sub 475}), F606W (V{sub 606}), F814W (I{sub 814}), and F850LP (z{sub 850}) optical data from the Advanced Camera for Surveys (ACS). The purely optical g{sub 475} - I{sub 814}, V{sub 606} - I{sub 814}, and g{sub 475} - z{sub 850} colors of NGC 1399's rich globular cluster (GC) system exhibit clear bimodality, at least for magnitudes I{sub 814} > 21.5. The optical-IR I{sub 814} - H{sub 160} color distribution appears unimodal, and this impression is confirmed by mixture modeling analysis. The V{sub 606} - H{sub 160} colors show marginal evidence for bimodality, consistent with bimodality in V{sub 606} - I{sub 814} and unimodality in I{sub 814} - H{sub 160}. If bimodality is imposed for I{sub 814} - H{sub 160} with a double Gaussian model, the preferred blue/red split differs from that for optical colors; these 'differing bimodalities' mean that the optical and optical-IR colors cannot both be linearly proportional to metallicity. Consistent with the differing color distributions, the dependence of I{sub 814} - H{sub 160} on g{sub 475} - I{sub 814} for the matched GC sample is significantly nonlinear, with an inflection point near the trough in the g{sub 475} - I{sub 814} color distribution; the result is similar for the I{sub 814} - H{sub 160} dependence on g{sub 475} - z{sub 850} colors taken from the ACS Fornax Cluster Survey. These g{sub 475} - z{sub 850} colors have been calibrated empirically against metallicity; applying this calibration yields a continuous, skewed, but single-peaked metallicity distribution. Taken together, these results indicate that nonlinear color-metallicity relations play an important role in shaping the observed bimodal distributions of optical colors in extragalactic GC systems.
- OSTI ID:
- 22011668
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 746; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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WIDE-FIELD MULTIBAND PHOTOMETRY OF GLOBULAR CLUSTER SYSTEMS IN THE FORNAX GALAXY CLUSTER
The globular cluster system of NGC 1399