Bolocam银河平面巡天-- III。双子座OB1分子云大质量恒星形成区的物理性质
The Bolocam Galactic Plane Survey -- III. Characterizing Physical Properties of Massive Star-Forming Regions in the Gemini OB1 Molecular Cloud
摘要：
我们提出了1.1毫米Bolocam银河平面调查（BGPS）的双子座OB 1分子云复杂的观测，并有针对性的氨观测的BGPS源。当与致密气体示踪剂的分子光谱学配对时，毫米观测产生物理特性，如质量、半径、平均密度、动力学温度和线宽。我们检测到34个不同的BGPS源以上5-西格玛=0.37焦耳/梁与相应的5-西格玛检测氨（1，1）过渡。八个物体显示水脉泽发射（20%）。对34个BGPS源的样品，我们发现平均毫米波源半高宽为1.12秒差距，平均动力学温度为20 K。所观察到的氨谱线宽度主要由非热运动，通常被发现是几倍的热声速预期的派生动力学温度。我们从毫米通量计算每个源的质量，假设源是等温的，并在120”孔径内找到230 +/- 180太阳质量的平均等温质量。我们发现双子座OB 1分子云中所有BGPS源的总质量为8，400太阳质量，占云质量的6.5%。通过将毫米等温质量与等于从氨线宽计算的毫米源尺寸的半径内的维里质量进行比较，我们发现样品的平均维里参数（M_vir/M_iso）为1.0 +/-0.9。我们发现，H_2的柱密度分布平均值为10^22 cm^-2，氨的柱密度分布平均值为3.0 × 10^14 cm^-2，因此氨相对于H_2的平均丰度为3.0 × 10 ^-8。我们发现体积平均密度在10^3-10^4 cm^-3的数量级。大小和密度表明，在宝石OB 1区域，BGPS正在检测形成星团的团块，而不是形成单个恒星或小型多系统的更小，更高密度的核心。
英文摘要：
We present the 1.1 millimeter Bolocam Galactic Plane Survey (BGPS) observations of the Gemini OB1 molecular cloud complex, and targeted ammonia observations of the BGPS sources. When paired with molecular spectroscopy of a dense gas tracer, millimeter observations yield physical properties such as masses, radii, mean densities, kinetic temperatures and line widths. We detect 34 distinct BGPS sources above 5-sigma=0.37 Jy/beam with corresponding 5-sigma detections in the ammonia (1,1) transition. Eight of the objects show water maser emission (20%). We find a mean millimeter source FWHM of 1.12 pc, and a mean kinetic temperature of 20 K for the sample of 34 BGPS sources. The observed ammonia line widths are dominated by non-thermal motions, typically found to be a few times the thermal sound speed expected for the derived kinetic temperature. We calculate the mass for each source from the millimeter flux assuming the sources are isothermal and find a mean isothermal mass within a 120" aperture of 230 +/- 180 solar masses. We find a total mass of 8,400 solar masses for all BGPS sources in the Gemini OB1 molecular cloud, representing 6.5% of the cloud mass. By comparing the millimeter isothermal mass to the virial mass within a radius equal to the mm source size calculated from the ammonia line widths, we find a mean virial parameter (M_vir/M_iso) of 1.0 +/- 0.9 for the sample. We find mean values for the distributions of column densities of 10^22 cm^-2 for H_2, and 3.0x10^14 cm^-2 for ammonia, giving a mean ammonia abundance of 3.0x10^-8 relative to H_2. We find volume-averaged densities on the order of 10^3-10^4 cm^-3. The sizes and densities suggest that in the Gem OB1 region the BGPS is detecting the clumps from which stellar clusters form, rather than smaller, higher density cores where single stars or small multiple systems form.
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