Multi-wavelength study of triggered star formation around 25 H II regions

We investigate 25 H II regions that show bubble morphology in 13CO（1-0） and infrared data, to search for quantitative evidence of triggered star formation by processes described by the collect and collapse （CC） and radiatively driven implosion （RDI） models. These H II regions display the morphology of a complete or partial bubble at 8 μm, and are all associated with the molecular clouds that surround them. We found that the electron temperature ranges from 5627 K to 6839 K in these H II regions, and the average electron temperature is 6083 K. The age of these H II regions is from 3.0× 10^5 yr to 1.7 × 10^6 yr, and the mean age is 7.7 × 10^5 yr. Based on the mor- phology of the associated molecular clouds, we divide these H II regions into three groups, which may support CC and RDI models. We select 23 young IRAS sources which have an infrared luminosity of 〉 10^3 Lo in 19 H II regions. In addition, we iden- tify some young stellar objects （including Class I sources）, which are only concen- trated in H II regions G29.007＋0.076, G44.339-0.827 and G47.028＋0.232. The poly- cyclic aromatic hydrocarbon emissions of the three H II regions all show a cometary globule. Comparing the age of each H II region with the characteristic timescales for star formation, we suggest that the three H II regions can trigger clustered star forma- tion by an RDI process. In addition, we detect seven molecular outflows in the five H II regions for the first time. These outflow sources may be triggered by the corresponding H II regions.

Star formation associated with the infrared dust bubble N68

We investigated the environment of the infrared dust bubble N68 and searched for evidence of triggered star formation in its surroundings. We performed a multiwavelength study of the nebula with data taken from several large-scale surveys： GLIMPSE, MIPSGAL, IRAS, NVSS, GRS and JCMT. We analyzed the spectral pro- file and the distribution of the molecular gas （13CO J -- 1 - 0 and J -- 3 - 2）, and the dust in the environment of N68. The position-velocity diagram clearly shows that N68 may be expanding outward. We used two three-color images of the mid-infrared emis- sion to explore the physical environment, and one color-color diagram to investigate the distribution of young stellar objects （YSOs）. We found that the 24 p^m emission is surrounded by the 8.0 ~m emission. Morphologically, the 1.4 GHz continuum strongly correlates with the 24 gm emission, and the 13CO J -- 1 - 0 and J -- 3 - 2 emissions correlate well with the 8.0 p^m emission. We investigated two compact cores located in the shell of N68. The spectral intensity ratios of 13CO J -- 3 - 2 to J = 1 - 0 range from 5 to 0.3. In addition, YSOs, masers, IRAS and UC HII regions are distributed in the shell of the bubble. The active region may be triggered by the expansion of the bubble N68.

1_(10)-1_(11) H_2CO and H_(110α) observations towards the giant HII region in cloud complex W43

The 110-111 formaldehyde （H2CO） absorption line and H110α radio recombination line （H RRL） are observed towards the giant HII region in cloud complex W43. The observations are obtained using the Nanshan 25 m single dish operated by Urumqi Observatory, National Astronomical Observatories of China. A region about 30 × 30 is observed, which covers the whole HII region in W43. Except for the central 10 region, all the other seven points are first observed with the H2CO 110-111 absorption. The column density of the H2CO is calculated, and the H2CO density contours show some differences with the infrared image. Multiple features appear in the H2CO and H RRL which indicate complex structure. The intensities of the H2CO and the velocities of the H110α seem to present a linear correlation, which illustrates that the sphere of influence of the central WR/OB cluster may be much more extended than presently known, since the size is nearly 50 pc.

A New Interpretation of the Bipolar HII Region S106 from HCN J = 3 - 2 Mapping Observations

The first mapping observations of the bipolar HII region S106 in HCN J = 3 - 2 line were made by KOSMA submillimeter telescope in April, 2004. The results show that there is a bipolar outflow centered on the high-mass star S106 IRS4 and that the flat structure of molecular cloud core is perpendicular to the axis of the outflow. This image roughly corresponds to the optical image where a dark lane bisects the bipolar HII region. Together with the optical, infrared and radio data, we conclude that the central UC HII region and molecular outflow formed before the two lobes of the bipolar HII region, and that a neutral disk is responsible for the bipolar HII region and the outflow.

Water abundance in four of the brightest water sources in the southern sky

We estimated the ortho-H2O abundances of G267.9–1.1, G268.4–0.9, G333.1–0.4 and G336.5–1.5, four of the brightest ortho-H2O sources in the southern sky observed by the Submillimeter Wave Astronomy Satellite（ortho-H2O1（10） – 1（01） line, 556.936 GHz）. The typical molecular clumps in our sample have H2 column densities of 10^22 to 10^23cm^-2 and ortho-H2O abundances of 10^-10. Compared with previous studies, the ortho-H2O abundances are at a low level, which can be caused by the low temperatures of these clumps. To estimate the ortho-H2O abundances, we used the CS J = 2 → 1 line（97.98095 GHz）and CS J = 5 → 4（244.93556 GHz） line observed by the Swedish-ESO 15 m Submillimeter Telescope（SEST） to calculate the temperatures of the clumps and the 350 μm dust continuum observed by the Caltech Submillimeter Observatory（CSO） telescope to estimate the H2 column densities. The observations of N2H^＋（J = 1 → 0） for these clumps were also acquired by SEST and the corresponding abundances were estimated. The N2H^＋ abundance in each clump shows a common decreasing trend toward the center and a typical abundance range from 10^-11 to 10^-9.