2017年IAO理论高年组第5题-赛弗特星系

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英文题目

β-5. Seyfert galaxy. The low-resolution spectrum of a galaxy: NGC 7479 (α= 23^h04^m57^s, δ=+12°19'22") was observed by the 2.16 m telescope of Xinglong Station near Beijing, National Astronomical Observatories of China, on September 14, 2009. The red part of this spectrum is shown in Fig.β5 (see separate sheet). The emission lines in the part of the spectrum are (from left to right): [NII]a, Hα, [NII]b.

5.1. Find the Beijing time (UTC+8, write the answer in 24h format: hh:mm) of the upper culmination of this galaxy in Xinglong Observatory on the observing date, in form of «T_c = ...».

5.2. Estimate the redshift z of this galaxy (write the answer in form of «z = ...»).

5.3. Find the distance to NGC 7479 (in units of Mpc, write the answer in form of «D = ...»).

5.4. Estimate the full width at half maximum (FWHM) of the Hα line (in units of km/s, write the answer in form of «FWHM(Hα) = ...»).

5.5. If the galaxy is known as a Seyfert galaxy, based on the line width of Hα, which type it should be ("Seyfert-l" or "Seyfert-ll")? Write the answer in English in form of «Type = ...». (Assume that the instrumental broadening can be neglected.)

IAO2017Tβ5

中文题目

β-5 赛弗特星系

2009年9月14日，中国国家天文台兴隆观测站2.16米望远镜拍摄到NGC 7479星系的低分辨率光谱：NGC 7479（α= 23h04m57s，δ= + 12°19'22“）

该光谱的红色部分如图β5所示（见单独的表）。部分光谱中的发射线是（从左到右）：[NII] a，Hα，[NII] b。

5.1 在观测日，以“Tc = ...”的形式写出兴隆天文台该星系上中天的北京时间（UTC + 8，写成24h格式：hh：mm）。（兴隆台：东经117°34′38″，北纬40°23′45″）

5.2 估计这个星系的红移z（以“z = ...”的形式写出答案）。

5.3 计算地球与NGC 7479的距离（以Mpc为单位，以“D = ......”的形式写出答案）。

5.4 估算Hα线的半高全宽（FWHM）（以km / s为单位，以“FWHM（Hα）= ......”的形式写出答案）。

5.5 如果星系被称为Seyfert星系，基于Hα的线宽，应该是哪种类型（“Seyfert-l”或“Seyfert-ll”）？ 用«Type = ...»的形式用英语写下答案。 （假设可以忽略仪器放大。）