论文标题
从幼HII地区鉴定的超紧张HII区域的人群
A population of hypercompact HII regions identified from young HII regions
论文作者
论文摘要
语境。通常确定幼年HII区域的派生物理参数，假设发射区域光学上很薄。但是，对于年轻的HII区域（例如超压缩HII（HCHII）和超紧凑型HII（UCHII））区域，这种假设不太可能存在，并且导致其性质低估。可以通过将SED拟合到广泛的无线电频率上来克服。 目标。这项研究的两个主要目标是（1）确定在寻找潜在的HCHII区域中无线电SED的年轻HII区域的物理特性，以及（2）使用这些物理特性来研究其进化。 方法。我们使用了Karl G. Jansky非常大的阵列（VLA）来观察X波段和K波段，其角度分辨率分别为〜1.7“和〜0.7”，朝着114个HII区域，其较高的位于1-5 GHz之间的HII区域。我们使用VLA档案数据进行补充，并在1-26 GHz的范围内构造SED，并假设它们具有均匀密度的电离HII区域。 结果。我们的样品的平均电子密度为Ne = 1.6e4cm^{ - 3}，直径直径= 0.14pc，并且发射测量em = 1.9e7pc*cm^{ - 6}。我们确定HCHII和UCHII区域之间的16个HCHII地区候选者和8个中间物体。 NE，DIAM和EM按预期发生变化，但是随着时间的流逝，Lyman Continuum Flux相对恒定。我们发现，大约67％的Lyman-Continuum光子被这些HII区域内的灰尘吸收，而对于更紧凑和更年轻的HII区域，灰尘吸收比例往往更为重要。 结论。年轻的HII地区通常位于尘土飞扬的团块中。 HCHII区域和中间物体通常与各种MASER，流出，广泛的无线电重组线和扩展的绿色物体有关，并且在两个阶段的积聚往往会迅速减少或停止。
Context. The derived physical parameters for young HII regions are normally determined assuming the emission region to be optically thin. However, this assumption is unlikely to hold for young HII regions such as hyper-compact HII(HCHII) and ultra-compact HII(UCHII) regions and leads to the underestimation of their properties. This can be overcome by fitting the SEDs over a wide range of radio frequencies. Aims. The two primary goals of this study are (1) to determine the physical properties of young HII regions from radio SEDs in the search for potential HCHII regions, and (2) to use these physical properties to investigate their evolution. Method. We used the Karl G. Jansky Very Large Array (VLA) to observe the X-band and K-band with angular resolutions of ~1.7" and ~0.7", respectively, toward 114 HII regions with rising-spectra between 1-5 GHz. We complement our observations with VLA archival data and construct SEDs in the range of 1-26 GHz and model them assuming an ionization-bounded HII region with uniform density. Results. Our sample has a mean electron density of ne=1.6E4cm^{-3}, diameter diam=0.14pc, and emission measure EM = 1.9E7pc*cm^{-6}. We identify 16 HCHII region candidates and 8 intermediate objects between the classes of HCHII and UCHII regions. The ne, diam, and EM change as expected, but the Lyman continuum flux is relatively constant over time. We find that about 67% of Lyman-continuum photons are absorbed by dust within these HII regions and the dust absorption fraction tends to be more significant for more compact and younger HII regions. Conclusion. Young HII regions are commonly located in dusty clumps; HCHII regions and intermediate objects are often associated with various masers, outflows, broad radio recombination lines, and extended green objects, and the accretion at the two stages tends to be quickly reduced or halted.
