CAJ | 학술논문

利用从斯隆数字巡天(Sloan Digital Sky Survey,简称SDSS)第 4 次释放的光谱数据中选取的 10~5个发射线星系样本,研究了[O Ⅱ]λ3727/Hα流量比与星系尘埃消光、气体电离态和金属丰度的关系.发现尘埃消光改正对[O Ⅱ]λ3727/Hα谱线流量比影响显著,消光改正前、后的[O Ⅱ]λ3727/Hα谱线流量比的中值分别为 0.48 和 0.89;尘埃消光改正后,F([O Ⅱ]λ3727)-F(Hα)的弥散显著减小.贫金属星系的[O Ⅱ]λ3727/Hα谱线流量比随星系气体的电离度增高而减小,而富金属星系不存在这种关系.另外,[O Ⅱ]λ3727/Hα流量比与星系金属丰度相关.当 12+lg(O/H)> 8.5时,星系[O Ⅱ]λ3727/Hα流量比随金属丰度增加而下降; 12+lg(O/H)< 8.5的星系,谱线流量比与金属丰度正相关.最后,利用气体电离度参数和星系的金属丰度,给出了计算不同类型星系[O Ⅱ]λ3727/Hα流量比的公式.LAMOST 望远镜将观测到大量红移 z > 0.4 的星系光谱,利用该公式可以给出星系的[O Ⅱ]λ3727/Hα流量比,从而可以利用[O Ⅱ]λ3727谱线流量计算 z > 0.4 星系的恒星形成率.
이용종사륭수자순천(Sloan Digital Sky Survey,간칭SDSS)제 4 차석방적광보수거중선취적 10~5개발사선성계양본,연구료[O Ⅱ]λ3727/Hα류량비여성계진애소광、기체전리태화금속봉도적관계.발현진애소광개정대[O Ⅱ]λ3727/Hα보선류량비영향현저,소광개정전、후적[O Ⅱ]λ3727/Hα보선류량비적중치분별위 0.48 화 0.89;진애소광개정후,F([O Ⅱ]λ3727)-F(Hα)적미산현저감소.빈금속성계적[O Ⅱ]λ3727/Hα보선류량비수성계기체적전리도증고이감소,이부금속성계불존재저충관계.령외,[O Ⅱ]λ3727/Hα류량비여성계금속봉도상관.당 12+lg(O/H)> 8.5시,성계[O Ⅱ]λ3727/Hα류량비수금속봉도증가이하강; 12+lg(O/H)< 8.5적성계,보선류량비여금속봉도정상관.최후,이용기체전리도삼수화성계적금속봉도,급출료계산불동류형성계[O Ⅱ]λ3727/Hα류량비적공식.LAMOST 망원경장관측도대량홍이 z > 0.4 적성계광보,이용해공식가이급출성계적[O Ⅱ]λ3727/Hα류량비,종이가이이용[O Ⅱ]λ3727보선류량계산 z > 0.4 성계적항성형성솔.
Although the Hα emission line provides a useful star formation rate(SFR)indicator for nearby galaxies,it is not easily observed for distant galaxies since this line shifts out of the visible band for z >0.4.Instead,the[O Ⅱ]λ3727 line is often used as an alternative indicator of SFR.Unfortunately,the[O Ⅱ]emission line is subjected to several factors,such as reddening,excitation state and abundance dependence.To investigate the systematic dependence of the[O Ⅱ]λ3727/Hα flux ratio on these different factors,10~5 emission line galaxies are selected from the Sloan Digital Sky Survey Data Release 4(SDSS DR4).The effective V-band optical depths(TV)of galaxies are calculated based on fluxes of Hα and Hβ lines.The dust extinction correction is very important to the[O Ⅱ]λ3727/Hα flux ra-tio.The mean observed and extinction-corrected flux ratios are 0.48 and 0.89.respectively.The extinction-corrected[O Ⅱ]λ3727/Hα flux ratio correlates with the ionization states of the interstellar gas for metal-poor galaxies,but there is no strong dependence for metal-rich galaxies.In additional,the[O Ⅱ]λ3727/Hα ratio depends on the oxygen abundance.For 12+lg(O/H)> 8.5,the emission-line ratio decreases with the increase of metallicity and conversely for metal-poor galaxies.We provide simple formulae to estimate the[O Ⅱ]λ3727/Hα flux ratio as a function of metallicity and excitation state.These formulae can be used to calculate SFR of galaxies with z > 0.4,such as galaxies to be observed from the deep field survey of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST).