摘要
B037 is of interest because it is both the most luminous and the most highly reddened cluster known in M31. Deep observations and high spatial resolution images with the Advanced Camera for Surveys on the Hubble Space Telescope （HST） first showed that this cluster is crossed by a dust lane. Photometric data in the F606W and F814W filters obtained in this paper indicate that colors of （F606W - F814W） in the dust lane are redder-0.4 mag than ones in the other regions of B037. The HST images show that this dust lane seems to be contained in B037, instead of in the M31 disk or the Milky Way. As far as we know, the formation of dust requires gas with a rather high metallicity. However, B037 has a low metallicity of [Fe/H] =→1.07 ±0.20. So, it seems improbable that the observed dust lane is physically associated with B037. It is clear that the origin of this dust lane is worthy of future study. In addition, based on these images, we present the precise variation of ellipticity and position angle, and of surface brightness profile, and determine the structural parameters of B037 by fitting a single-mass isotropic King model. In the F606W filter, we derive the best-fitting scale radius r0 = 0.56±0.02＂ （= 2.16±0.08 pc）, a tidal radius rt = 8.6±0.4I＂ （= 33.1±1.5 pc）, and a concentration index c = log（rt/ro） = 1.19±0.02. In the F814W filter, we derive r0 = 0.56 4± 0.01H （_=2.16 ±0.04 pc）, rt = 8.9 ±0.3＂ （= 34.3±1.2 pc）, and c = log（rt/ro） = 1.20±0.01. The extinction-corrected central surface brightness is μ0 = 13.53±0.03 mag arcsec^-2 in the F606W filter, and 12.85±0.03 mag arcsec^-2 in the F814W filter. We also calculate the half-light radius at rh = 1.05±0.03＂（= 4.04±0.12 pc） in the F606W filter and rh =1.07±0.01＂（= 4.12±0.04 pc） in the F814W filter. In addition, we derived the complete magnitudes of B037 in the V and I bands by transforming the magnitudes from the ACS system to the standard system, which are in good agreement with previous ground-based broad- band photometry studies.
B037 is of interest because it is both the most luminous and the most highly reddened cluster known in M31. Deep observations and high spatial resolution images with the Advanced Camera for Surveys on the Hubble Space Telescope （HST） first showed that this cluster is crossed by a dust lane. Photometric data in the F606W and F814W filters obtained in this paper indicate that colors of （F606W - F814W） in the dust lane are redder-0.4 mag than ones in the other regions of B037. The HST images show that this dust lane seems to be contained in B037, instead of in the M31 disk or the Milky Way. As far as we know, the formation of dust requires gas with a rather high metallicity. However, B037 has a low metallicity of [Fe/H] =→1.07 ±0.20. So, it seems improbable that the observed dust lane is physically associated with B037. It is clear that the origin of this dust lane is worthy of future study. In addition, based on these images, we present the precise variation of ellipticity and position angle, and of surface brightness profile, and determine the structural parameters of B037 by fitting a single-mass isotropic King model. In the F606W filter, we derive the best-fitting scale radius r0 = 0.56±0.02＂ （= 2.16±0.08 pc）, a tidal radius rt = 8.6±0.4I＂ （= 33.1±1.5 pc）, and a concentration index c = log（rt/ro） = 1.19±0.02. In the F814W filter, we derive r0 = 0.56 4± 0.01H （_=2.16 ±0.04 pc）, rt = 8.9 ±0.3＂ （= 34.3±1.2 pc）, and c = log（rt/ro） = 1.20±0.01. The extinction-corrected central surface brightness is μ0 = 13.53±0.03 mag arcsec^-2 in the F606W filter, and 12.85±0.03 mag arcsec^-2 in the F814W filter. We also calculate the half-light radius at rh = 1.05±0.03＂（= 4.04±0.12 pc） in the F606W filter and rh =1.07±0.01＂（= 4.12±0.04 pc） in the F814W filter. In addition, we derived the complete magnitudes of B037 in the V and I bands by transforming the magnitudes from the ACS system to the standard system, which are in good agreement with previous ground-based broad- band photometry studies.
基金
supported by the National Natural Science Foundation of China (Grant Nos.10873016 and 10633020)
the National Basic Research Program of China (973 Program),No. 2007CB815403
