标题： 星系中超紧致HII区的亮度函数和大质量恒星的初始质量函数（IMF） 显示英文标题

标题： The luminosity function of galactic ultra-compact HII regions and the IMF for massive stars

摘要： 研究了仍在其母分子云中形成的新一代大质量恒星群体，这一研究是在银河盘尺度上进行的。 我们分析了红外天文卫星（IRAS）点源的亮度函数，这些源具有超紧致HII区的远红外（FIR）颜色，并且已经在CS(2-1)线（高密度分子气体的示踪剂）中被探测到。 从555个大质量恒星形成区域（MSFRs）的四条IRAS波段的流量以及根据CS(2-1)速度剖面推导出的运动学距离，推测出其中413个位于太阳圈内的FIR亮度。 对于UCHII区候选体的亮度函数（LF），其峰值明显高于完整性极限，并且在太阳圈内和之外有所不同（置信度为96%）。在太阳圈内，LF的最大值出现在2E5 Lo；而在太阳圈外，最大值出现在5E4 Lo。 我们用三个自由参数对LF进行了建模： -alpha，初始质量函数（IMF）以log(M/Mo)表示的指数； -beta，MSFR中每颗星数量N*的幂律分布指数；以及N*max，N*的上限。 虽然alpha在整个银河系中的值约为2.0，但beta从太阳圈内的约0.5变化到太阳圈外的约0.7，MSFR中每颗星的数量最大值约为650和约450（1 < M/Mo < 120）。 尽管IMF似乎没有变化，但太阳圈内的MSFR中平均每颗星的数量高于外部银河系。 显示英文摘要

摘要： The population of newly formed massive stars, while still embedded in their parent molecular clouds, is studied on the galactic disk scale. We analyse the luminosity function of IRAS point-like sources, with far-infrared (FIR) colours of ultra-compact HII regions, that have been detected in the CS(2-1) line - a tracer of high density molecular gas. The FIR luminosities of 555 massive star forming regions (MSFRs), 413 of which lie within the solar circle, are inferred from their fluxes in the four IRAS bands and from their kinematic distances, derived using the CS(2-1) velocity profiles. The luminosity function (LF) for the UCHII region candidates shows a peak well above the completeness limit, and is different within and outside the solar circle (96% confidence level). While within the solar circle the LF has a maximum for 2E5 Lo, outside the solar circle the maximum is at 5E4 Lo. We model the LF using three free parameters: -alpha, the exponent for the initial mass function (IMF) expressed in log(M/Mo); -beta, the exponent for a power law distribution in N*, the number of stars per MSFR; and N*max, an upper limit for N*. While alpha has a value of \~ 2.0 throughout the Galaxy, beta changes from ~ 0.5 inside the solar circle to \~ 0.7 outside, with a maximum for the number of stars per MSFR of ~650 and \~450 (with 1 <M/Mo< 120). While the IMF appears not to vary, the average number of stars per MSFR within the solar circle is higher than for the outer Galaxy.