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.)

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