A SURVEY OF DIFFUSE INTERSTELLAR BANDS IN THE ANDROMEDA GALAXY: OPTICAL SPECTROSCOPY OF M31 OB STARS
A SURVEY OF DIFFUSE INTERSTELLAR BANDS IN THE ANDROMEDA GALAXY: OPTICAL SPECTROSCOPY OF M31 OB STARS
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DOI：
10.1088/0004-637x/726/1/39
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发表时间：
2010-11
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影响因子：
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通讯作者：
M. Cordiner;N. Cox;C. Evans;C. Trundle;Keith T. Smith;P. Sarre;K. Gordon
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作者：
M. Cordiner;N. Cox;C. Evans;C. Trundle;Keith T. Smith;P. Sarre;K. Gordon
我们提出了迄今为止最大的样本中分辨率蓝到红光谱的B型超巨星在M31和进行第一次调查的弥漫星际带（DIBs）在这个星系。光谱分类，径向速度，和星际红化的34颗恒星在三个地区的M31。基于这些恒星的一个子集，前景校正的红化EM 31 B-V <$0.05，M31 DIBs的强度分析相对于尘埃量，紫外辐射场强度和多环芳烃排放通量。给出了λ5780和λ6283 DIBs朝向11颗恒星的径向速度和等效宽度。在M31的三条视线中检测到的以下DIB的等效宽度也被呈现：λλ 4428、5705、5780、5797、6203、6269、6283、6379、6613、6660和6993。所有这些M31 DIB载体都以与星际Na i和/或H i相匹配的径向速度驻留在云中。DIB等效宽度和红化（EM 31 B-V）之间的关系与在银河系（MW）的本地星际介质（ISM）中观察到的一致。许多观测到的视线显示DIB强度（每单位红化）位于银河值范围的上端。DIB强度每单位变红（68%的置信度）与星际紫外辐射场强度。在星际紫外线通量最低的地方观察到最强的DIB。在我们的三个视场中，平均Spitzer 8/24 μm发射比略低于MW中的测量值，但我们确定该比值与M31中的DIB强度之间没有相关性。由其中一个区域的三个M31 H ii区的光谱导出的星际氧丰度表明，该区域ISM的平均金属丰度为12 + log [O/H] = 8.54 ± 0.18，与太阳附近的值大致相等。
We present the largest sample to date of intermediate-resolution blue-to-red optical spectra of B-type supergiants in M31 and undertake the first survey of diffuse interstellar bands (DIBs) in this galaxy. Spectral classifications, radial velocities, and interstellar reddenings are presented for 34 stars in three regions of M31. Based on a subset of these stars with foreground-corrected reddening EM 31B−V⩾ 0.05, the strengths of the M31 DIBs are analyzed with respect to the amount of dust, ultraviolet radiation field strength, and polycyclic aromatic hydrocarbon emission flux. Radial velocities and equivalent widths are given for the λ5780 and λ6283 DIBs toward 11 stars. Equivalent widths are also presented for the following DIBs detected in three sightlines in M31: λλ4428, 5705, 5780, 5797, 6203, 6269, 6283, 6379, 6613, 6660, and 6993. All of these M31 DIB carriers reside in clouds at radial velocities matching those of interstellar Na i and/or H i. The relationships between DIB equivalent widths and reddening (EM 31B−V) are consistent with those observed in the local interstellar medium (ISM) of the Milky Way (MW). Many of the observed sightlines show DIB strengths (per unit reddening) which lie at the upper end of the range of Galactic values. DIB strengths per unit reddening are found (with 68% confidence) to correlate with the interstellar UV radiation field strength. The strongest DIBs are observed where the interstellar UV flux is lowest. The mean Spitzer 8/24 μm emission ratio in our three fields is slightly lower than that measured in the MW, but we identify no correlation between this ratio and the DIB strengths in M31. Interstellar oxygen abundances derived from the spectra of three M31 H ii regions in one of the fields indicate that the average metallicity of the ISM in that region is 12 + log [O/H] = 8.54 ± 0.18, which is approximately equal to the value in the solar neighborhood.