“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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（创建页面，内容为“'''<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, interstel…”）
 
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{| class="wikitable"
 
{| class="wikitable"
 
|+Table 1. (Observed Frame) IR Photometry of CR7 at z=6.60
 
|+Table 1. (Observed Frame) IR Photometry of CR7 at z=6.60
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!Band                        
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!Band
−
!Y                              
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!Y
 
!J
 
!J
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!H
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!H
 
!K
 
!K
 
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|-
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|Central Wavelength (μm）                    
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|Central Wavelength (μm）
 
|1.05
 
|1.05
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|1.25                    
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|1.25
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|1.65                      
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|1.65
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|2.15                            
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|2.15
 
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|-
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|AB Magnitude                          
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|AB Magnitude
 
|24.71±0.11
 
|24.71±0.11
 
|24.63±0.13
 
|24.63±0.13
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|25.15±0.15
 
|25.15±0.15
 
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(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 m<sub>AB</sub>as a function of 𝜆 and 𝑚<sub>1600</sub> , where 𝑚<sub>1600</sub> is the AB magnitude at 𝜆<sub>0</sub>=160 nm (1600 Å))

2019年9月10日 (二) 13:35的版本

(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.

Table 1. (Observed Frame) IR Photometry of CR7 at z=6.60
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))

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