Anomalously steep reddening law in quasars: an exceptional example observed in iras 14026+4341
Anomalously steep reddening law in quasars: an exceptional example observed in iras 14026+4341
复制标题
类星体中异常陡峭的红化定律：在 IRAS 14026 4341 中观察到的一个例外例子
DOI：
10.1088/0004-6256/145/6/157
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发表时间：
2013
影响因子：
5.3
通讯作者：
Wang Tinggui
中科院分区：
文献类型：
--
作者：
Jiang Peng;Zhou Hongyan;Ji Tuo;Shu Xinwen;Liu Wenjuan;Wang Jianguo;Dong Xiaobo;Bai Jinming;Wang Huiyuan;Wang Tinggui
A fraction of the heavily reddened quasars require a reddening curve that is even steeper than that of the Small Magellanic Cloud. In this paper, we thoroughly characterize the anomalously steep reddening law in quasars via an exceptional example observed in IRAS 14026+4341. By comparing the observed spectrum to the quasar composite spectrum, we derive a reddening curve in the rest-frame wavelength range of 1200–10000 Å. It has a steep rise at wavelengths shorter than 3000 Å, but no significant reddening at longer wavelengths. The absence of dust reddening in the optical continuum is confirmed by the normal broad-line Balmer decrement (the Hα/Hβ ratio) in IRAS 14026+4341. The anomalous reddening curve can be satisfactorily reproduced with a dust model containing silicate grains in a power-law size distribution, dn(a)/da∝a−1.4, truncated at a maximum size of amax = 70 nm. The unusual size distribution may be caused by the destruction of large “stardust” grains by quasar activities or a different dust formation mechanism (i.e., the in situ formation of dust grains in quasar outflows). It is also possible that the analogies of the dust grains observed near the Galactic center are responsible for the steep reddening curve. In addition, we find that IRAS 14026+4341 is a weak emission-line quasar (i.e., PHL 1811 analogies) with heavy dust reddening and blueshifted broad absorption lines.
