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arXiv 0905.1177astro-ph.CO
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引力透镜类星体QSO 2237+0305的斯皮策观测

Spitzer observations of a gravitationally lensed quasar, QSO 2237+0305

Eric Agol, Stephanie Gogarten, Varoujan Gorjian, Amy Kimball

摘要:

类星体QSO 2237+0305是一个四像引力透镜类星体,它被透镜星系中的恒星所微透镜化。微透镜变化的幅度可以用来推断类星体的相对大小作为波长的函数,这提供了一个类星体模型的测试。为此,我们提出了斯皮策太空望远镜红外光谱仪和红外阵列相机(IRAC)的观测类星体2237+0305,发现如下。(1)红外光谱能量分布(SED)类似于其他明亮的射电宁静类星体,与先前的说法相反。(2)一个尘埃环模型与一个小的开口角适合的整体形状的红外SED以及,但定量协议是穷人由于偏移波长的硅酸盐功能。(3)四个透镜图像的通量比可以从IRAC数据中导出,尽管尚未解决。我们发现,近红外通量越来越受到微透镜向更短波长。(4)IRAC通量比的波长依赖性与标准类星体模型一致,在标准类星体模型中,吸积盘和尘埃环都贡献了近1微米的静止坐标系。这也与最近的红外光谱偏振附近的类星体。

英文摘要:

The four-image gravitationally lensed quasar QSO 2237+0305 is microlensed by stars in the lens galaxy. The amplitude of microlensing variability can be used to infer the relative size of the quasar as a function of wavelength; this provides a test of quasar models. Toward this end, we present Spitzer Space Telescope Infrared Spectrograph and Infrared Array Camera (IRAC) observations of QSO 2237+0305, finding the following. (1) The infrared (IR) spectral energy distribution (SED) is similar to that of other bright radio-quiet quasars, contrary to an earlier claim. (2) A dusty torus model with a small opening angle fits the overall shape of the IR SED well, but the quantitative agreement is poor due to an offset in wavelength of the silicate feature. (3) The flux ratios of the four lensed images can be derived from the IRAC data despite being unresolved. We find that the near-IR fluxes are increasingly affected by microlensing toward shorter wavelengths. (4) The wavelength dependence of the IRAC flux ratios is consistent with the standard quasar model in which an accretion disk and a dusty torus both contribute near 1 micron in the rest frame. This is also consistent with recent IR spectropolarimetry of nearby quasars.

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