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arXiv 0906.4839astro-ph.CO
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M31恒星形成区的紫外研究

An Ultraviolet Study of Star-Forming Regions in M31

Yongbeom Kang, Luciana Bianchi, Soo-Chang Rey

摘要:

本文对最近的大旋涡星系M31中的恒星形成区进行了全面的研究。我们使用GALEX远紫外(1344-1786 nm,FUV)和近紫外(1771-2831 nm,NUV)成像来探测年轻的大质量恒星,并追踪整个星系最近的恒星形成。SF区域的FUV和NUV通量测量,结合用于估计来自它们所包含的大质量恒星的星际尘埃变红的地面数据,被用来推导它们的年龄和质量。GALEX成像结合了深度灵敏度和整个星系的覆盖范围,提供了M31最近恒星形成及其随整个星系环境变化的完整图片。FUV和NUV测量对于探测几百万年前的恒星星族是敏感的。在整个26 kpc星系盘上,我们探测到了894个SF区域,其大小大于1600 pc^{2},高于平均FUV通量极限~ 26 ABmag角秒^{-2}。我们推导出M31在这段时间内的恒星形成历史。正如预期的那样,来自最年轻的紫外源(年龄<1000万年)的恒星形成率(SFR)与来自H_{alpha}的恒星形成率相当。我们显示的依赖性的结果上假设的金属丰度。当从红外测量的加热尘埃中检测到的恒星形成被添加到紫外测量的恒星形成中时,(从未模糊的种群)在最近几个百万年,我们发现SFR在最近的时代略有下降,可能在10到100百万年之间达到峰值,在过去的4亿年中,SFR的平均值约为0.6或0.7 M_{sun} yr^{-1}(金属丰度Z分别为0.02或0.05)。

英文摘要:

We present a comprehensive study of star-forming (SF) regions in the nearest large spiral galaxy M31. We use GALEX far-UV (1344-1786 Å, FUV) and near-UV (1771-2831 Å, NUV) imaging to detect young massive stars and trace the recent star formation across the galaxy. The FUV and NUV flux measurements of the SF regions, combined with ground-based data for estimating the reddening by interstellar dust from the massive stars they contain, are used to derive their ages and masses. The GALEX imaging, combining deep sensitivity and coverage of the entire galaxy, provides a complete picture of the recent star formation in M31 and its variation with environment throughout the galaxy. The FUV and NUV measurements are sensitive to detect stellar populations younger than a few hundred Myrs. We detected 894 SF regions, with size > 1600 pc^{2} above an average FUV flux limit of ~ 26 ABmag arcsecond^{-2}, over the whole 26 kpc galaxy disk. We derive the star-formation history of M31 within this time span. The star formation rate (SFR) from the youngest UV sources (age < 10 Myr) is comparable to that derived from H_{alpha}, as expected. We show the dependence of the results on the assumed metallicity. When star formation detected from IR measurements of the heated dust is added to the UV-measured star formation (from the unobscured populations) in the recent few Myrs, we find the SFR has slightly decreased in recent epochs, with a possible peak between 10 and 100 Myrs, and an average value of SFR ~ 0.6 or 0.7 M_{sun} yr^{-1} (for metallicity Z=0.02 or 0.05 respectively) over the last 400 Myrs.

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