The Milky Way contains thousands of H ii region candidates identified by their characteristic mid-infrared morphology, but lacking detections of ionized gas tracers such as radio continuum or radio recombination line emission. These targets thus remain unconfirmed as H ii regions. With only ∼2500 confirmed H ii regions in the Milky Way, Galactic surveys are deficient by several thousand nebulae when compared to external galaxies with similar star formation rates. Using sensitive 9 GHz radio continuum observations with the Karl G. Jansky Very Large Array, we explore a sample of H ii region candidates in order to set observational limits on the actual total population of Galactic H ii regions. We target all infrared–identified “radio-quiet” sources from the Wide-field Infrared Survey Explorer Catalog of Galactic H ii regions between 245 ≥ ℓ ≥ 90 with infrared diameters less than 80^′′. We detect radio continuum emission from 50% of the targeted H ii region candidates, providing strong evidence that most of the radio-quiet candidates are bona fide H ii regions. We measure the peak and integrated radio flux densities and compare the inferred Lyman continuum fluxes using models of OB stars. We conclude that stars of approximately spectral type B2 and earlier are able to create H ii regions with similar infrared and radio continuum morphologies as the more luminous H ii regions created by O stars. From our 50% detection rate of “radio-quiet” sources, we set a lower limit of ∼7000 for the H ii region population of the Galaxy. Thus the vast majority of the Milky Way’s H ii regions remain to be discovered.

银河系包含数千个H ii区域候选物，这些候选物通过其特征性的中红外形态来识别，但缺少对电离气体示踪剂（如无线电连续谱或无线电重组线发射）的检测。因此，这些目标仍未被确认为H ii地区。在银河系中只有约2500个已确认的H ii区，与具有类似恒星形成速度的外部星系相比，银河系调查的星云不足。我们使用卡尔·詹斯基（Karl G.Jansky）超大型阵列对9 GHz无线电连续谱进行敏感观测，探索了H ii区域候选样本，以便为银河H ii的实际总种群设置观测极限。地区。我们的目标从银河H的宽视场红外线探测目录所有红外线识别的“无线电安静”源II之间245≥区域ℓ 90≥用红外直径小于80 ^'' 。我们从目标H ii地区的50％候选者中检测到无线电连续辐射，提供了有力的证据，证明大多数无线电安静的候选者都是真正的H ii地区。我们测量峰值和积分无线电通量密度，并使用OB星模型比较推断的Lyman连续谱通量。我们得出结论，大约光谱类型为B2或更早的恒星能够产生H ii区域具有与O恒星产生的更发光的H ii区域相似的红外和射电连续体形态。从“无线电安静”源的50％检出率来看，我们为银河H ii地区人口设定了约7000的下限。因此，银河系的大部分H ii地区仍有待发现。