“2018年IOAA数据分析第1题-产星星系中的尘埃与年轻恒星”的版本间的差异
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− | '''<big>(D1) Dust and Young Stars in Star-forming Galaxies [75 points]</big>''' | + | {{需要解答}}'''<big>(D1) Dust and Young Stars in Star-forming Galaxies [75 points]</big>''' |
As a by-product of the star-forming process in a galaxy, interstellar dust can significantly absorb stellar light in ultraviolet (UV) and optical bands, and then re-emit in far-infrared (FIR), which corresponds to a wavelength range of 10-300 µm. | As a by-product of the star-forming process in a galaxy, interstellar dust can significantly absorb stellar light in ultraviolet (UV) and optical bands, and then re-emit in far-infrared (FIR), which corresponds to a wavelength range of 10-300 µm. |
2019年9月10日 (二) 22:49的版本
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(D1) Dust and Young Stars in Star-forming Galaxies [75 points]
As a by-product of the star-forming process in a galaxy, interstellar dust can significantly absorb stellar light in ultraviolet (UV) and optical bands, and then re-emit in far-infrared (FIR), which corresponds to a wavelength range of 10-300 µm.
1.1. In the UV spectrum of a galaxy, the major contribution is from the light of the young stellar population generated in recent star-formation processes, thus the UV luminosity can act as a reliable tracer of the starformation rate (SFR) of a galaxy. Since the observed UV luminosity is strongly affected by dust attenuation, extragalactic astronomers define an index called the UV continuum slope (β) to quantify the shape of the UV continuum:
𝑓 V=𝑄⋅𝜆Z
where 𝑓V is the monochromatic flux of the galaxy at a given wavelength 𝜆 (in the unit of W m-3) and 𝑄 is a scaling constant.
(D1.1.1) (6 points) AB magnitude is a specific magnitude system. The AB magnitude is defined as:
mAB=−2.5log( 𝑓ν /3631Jy)
The AB magnitude of a typical galaxy is roughly constant in the UV band. What is the UV continuum slope of this kind of galaxy? (Hint: 𝑓λ∆𝜈=𝑓𝜆∆𝜆 )
(D1.1.2) (12 points) Table 1 presents the observed IR photometry results for a 𝑧=6.60 galaxy called CR7. Plot the AB magnitude of CR7 versus the logarithm of the rest-frame wavelength on graph paper and labelled as Figure 1.
Band | Y | J | H | K |
---|---|---|---|---|
Central Wavelength (μm) | 1.05 | 1.25 | 1.65 | 2.15 |
AB Magnitude | 24.71±0.11 | 24.63±0.13 | 25.08±0.14 | 25.15±0.15 |
(D1.1.3) (5 points) Calculate CR7’s UV slope, plot the best-fit UV continuum on Figure 1 and make a comparison with the results you obtained in (D1.1.1). Is it dustier than the typical galaxy in (D1.1.1)? Please answer with [YES] or [NO]. (Hint: Express mABas a function of 𝜆 and 𝑚1600 , where 𝑚1600 is the AB magnitude at 𝜆0=160 nm (1600 Å))