北双子星座多目标光谱仪的光度定标
Calibration of photometry from the Gemini Multi-Object Spectrograph on Gemini North
摘要：
利用2001年8月至2003年12月期间在北双子座的双子座多目标分光仪获得的光度标准星的所有可用观测数据，建立了该仪器获得的光度校准。本文中提出的校准是基于显着更多的光度标准恒星观测比通常使用的个人用户。夜间光度零点以及颜色项的确定。颜色项预计对UT 2004年11月21日之前进行的所有观测都有效，当时双子座北主镜涂有银而不是铝。虽然夜间零点精确到0.02等或更好（随机误差），但校准的准确性受到所谓“天空集中”的系统误差的限制，这是所有焦点减少器仪器中都会出现的一种效应。我们的结论是，0.035至0.05 mag的准确度可以通过使用本文导出的校准实现。颜色项对于非常红的物体是最强的，例如，对于具有（r '-z'）=3.0的物体，如果忽略颜色项，则所得到的z'幅度将是~0.35 mag太亮。这些校准对于拥有2004年11月21日UT之前获得的数据的大型Gemini用户社区以及来自这一时期的achive数据的未来用户来说非常重要。
英文摘要：
All available observations of photometric standard stars obtained with the Gemini Multi-Object Spectrograph at Gemini North in the period from August 2001 to December 2003 have been used to establish the calibrations for photometry obtained with the instrument. The calibrations presented in this paper are based on significantly more photometric standard star observations than usually used by the individual users. Nightly photometric zero points as well as color terms are determined. The color terms are expected to be valid for all observations taken prior to UT 2004 November 21 at which time the Gemini North primary mirror was coated with silver instead of aluminum. While the nightly zero points are accurate to 0.02 mag or better (random errors), the accuracy of the calibrations is limited by systematic errors from so-called "sky concentration", an effect seen in all focal reducer instruments. We conclude that an accuracy of 0.035 to 0.05 mag can be achieved by using calibrations derived in this paper. The color terms are strongest for very red objects, e.g. for objects with (r'-z')=3.0 the resulting z' magnitudes will be ~0.35 mag too bright if the color term is ignored. The calibrations are of importance to the large Gemini user community with data obtained prior to UT 2004 November 21, as well as future users of achive data from this period in time.
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