Inclination-dependent Luminosity Function of Spiral Galaxies in the Sloan Digital Sky Survey: Implications for Dust Extinction
Inclination-dependent Luminosity Function of Spiral Galaxies in the Sloan Digital Sky Survey: Implications for Dust Extinction
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DOI：
10.1086/511131
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发表时间：
2006-11
期刊：
影响因子：
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通讯作者：
Z. Shao;Q. Xiao;S. Shen;H. Mo;X. Xia;Z. Deng
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文献类型：
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作者：
Z. Shao;Q. Xiao;S. Shen;H. Mo;X. Xia;Z. Deng
使用从SDSS DR2中选出的61,506个螺旋星系样本，我们检查了具有不同倾角的螺旋星系的光度函数（LF）。我们发现 LF 的特征光度 L* 随着倾角的增加而减小，而微弱端斜率 α 对其的依赖性很小。 LF 的倾角依赖性与简单模型的预期一致，其中光学深度与倾角的余弦成正比，并且我们使用似然方法来恢复余弦前面的系数 γ 和正面观察的星系的 LF。 γ 的值与给定波段内的星系光度完全无关，通过这种方式获得的 5 个 SDSS 波段的 γ 值给出了一条消光曲线，该曲线是波长的幂律 (τ ∝ λ-n)，幂指数为 n = 0.96 ± 0.04。利用考夫曼和同事获得的星系尘埃消光，我们推导出螺旋星系的“消光校正”光度函数。尘埃消光使 M* 在 z 波段变暗约 0.5 星等，在 u 波段变暗约 1.2 星等。由于我们的分析是基于选择效应得到很好控制的样本，因此边缘星系相对于正面星系的变暗最好通过假设星系盘在灰尘吸收方面具有光学厚度来解释。
Using a sample of 61,506 spiral galaxies selected from the SDSS DR2, we examine the luminosity function (LF) of spiral galaxies with different inclination angles. We find that the characteristic luminosity of the LF, L*, decreases with increasing inclination, while the faint-end slope, α, depends only weakly on it. The inclination dependence of the LF is consistent with that expected from a simple model in which the optical depth is proportional to the cosine of the inclination angle, and we use a likelihood method to recover both the coefficient in front of the cosine, γ, and the LF for galaxies viewed face-on. The value of γ is quite independent of galaxy luminosity in a given band, and the values of γ obtained in this way for the five SDSS bands give an extinction curve that is a power law of wavelength (τ ∝ λ-n), with a power index of n = 0.96 ± 0.04. Using the dust extinction for galaxies obtained by Kauffmann and coworkers, we derive an "extinction-corrected" luminosity function for spiral galaxies. Dust extinction makes M* dimmer by ~0.5 mag in the z band and by ~1.2 mag in the u band. Since our analysis is based on a sample in which selection effects are well under control, the dimming of edge-on galaxies relative to face-on galaxies is best explained by assuming that galaxy disks are optically thick in dust absorption.