Accurate photometry of extended spherically symmetric sources
Accurate photometry of extended spherically symmetric sources
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DOI：
10.1051/0004-6361:20054175
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发表时间：
2006-02
影响因子：
6.5
通讯作者：
P. Anders;M. Gieles;R. M. F. Astrophysik;Goettingen;H Germany;A. Institute;Utrecht;The Netherlands.-The-N
中科院分区：
文献类型：
--
作者：
P. Anders;M. Gieles;R. M. F. Astrophysik;Goettingen;H Germany;A. Institute;Utrecht;The Netherlands.-The-N
我们提出了一种新方法，可以从HST图像（WFPC 2、ACS/WFC和NICMOS/NIC 2相机）中推导出扩展球对称源的可靠测光，扩展了现有的点源和边缘分辨率源的研究。我们开发了一种新的方法来准确地确定扩展的球对称源，如本星系群以外的星系中的星星团（在距离<20 Mpc）的内在大小，并提供了一个详细的食谱，以执行孔径测光对这样的源，通过确定大小相关的孔径校正（AC），并考虑天空过减作为源大小的函数。在一个广泛的附录中，我们提供了多项式之间的关系参数的FWHM的各种输入配置文件和那些通过拟合高斯配置文件（我们已经使用的原因计算的鲁棒性，虽然使用的确切的模型配置文件是无关紧要的），和集群和派生AC的内在和测量的FWHM。这两种关系给出了一些物理相关的集群光剖面，内在和观测参数。为各种孔径提供了AC关系。根据光源的大小和测光所用的环带，这种扩展天体的绝对星等可以被低估3等，相当于质量误差的15倍。我们仔细地将我们的结果与更广泛使用的DeltaMag方法的结果进行了比较，发现在尺寸测定和AC方面都有3 - 40倍的改进。
We present a new method to derive reliable photometry of extended spherically symmetric sources from HST images (WFPC2, ACS/WFC and NICMOS/NIC2 cameras), extending existing studies of point sources and marginally resolved sources. We develop a new approach to accurately determine intrinsic sizes of extended spherically symmetric sources, such as star clusters in galaxies beyond the Local Group (at distances <20 Mpc), and provide a detailed cookbook to perform aperture photometry on such sources, by determining size-dependent aperture corrections (ACs) and taking sky oversubtraction as a function of source size into account. In an extensive Appendix, we provide the parameters of polynomial relations between the FWHM of various input profiles and those obtained by fitting a Gaussian profile (which we have used for reasons of computational robustness, although the exact model profile used is irrelevant), and between the intrinsic and measured FWHM of the cluster and the derived AC. Both relations are given for a number of physically relevant cluster light profiles, intrinsic and observational parameters. AC relations are provided for a wide range of apertures. Depending on the size of the source and the annuli used for the photometry, the absolute magnitude of such extended objects can be underestimated by up to 3 mag, corresponding to an error in mass of a factor of 15. We carefully compare our results to those from the more widely used DeltaMag method, and find an improvement of a factor of 3−40 in both the size determination and the AC.