Global photometric analysis of Galactic HII regions

Total infrared fluxes are estimated for 99 HII regions around massive stars. The following wavebands have been used for the analysis： 8 and 24 μm, based on data from the Spitzer Space Telescope （IRAC and MIPS, respectively）; 70, 160, 250, 350 and 500 μm, based on data from the Herschel Space Observatory （PACS and SPIRE）. The estimated fluxes are used to evaluate the polycyclic aromatic hy- drocarbon （PAH） mass fraction （qPAH） and the intensity of ultraviolet emission in the studied objects. It is shown that the PAH mass fraction, qPAH, is much lower in these objects than the average Galactic value, implying effective destruction of aromatic particles in HII regions. Estimated radiation field inten- sities （U） are close to those derived for extragalactic HII complexes. Color indices [F24/F8], [F70/F24], [F160/F24] and [F160/F70] are compared to criteria proposed to distinguish between regions of ionized hydrogen and planetary nebulae. Also, we relate our results to analogous color indices for extragalactic complexes of ionized hydrogen.

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.

H_2CO and H110α survey toward UCHII regions

We report results of the H2CO and H110α survey toward 281 UCHII regions using the Urumqi 25m radio telescope.We obtained 37 new H2CO detections,and H110α was simultaneously detected in eight of them.Only H110α was detected in another UCHII region.We calculated kinematic distances of nine UCHII regions with the detected H110α and resolved the kinematic distance ambiguity for six of them.The detection rate of H2CO of our observation was 13.2%,which is low compared with one of the other authors.The possible reason is that the sensitivity of our telescope is relatively low.

Properties of the UCHII region G25.4NW and its associated molecular cloud

Ultra compact HII （UCHII） G25.4NW is a bright IR source in the region of the inner Galaxy. New HI images from the Very Large Array Galactic Plane Survey show clear absorption features associated with the UCHII region up to 95 km s^-1, and there are no other absorptions up to the tangential velocity. This reveals that G25.4NW has a near-side distance of 5.7 kpc, and it is located in the region of the inner Galactic molecular ring. Using the new distance, the bolometric luminosity of G25.4NW is estimated as 105.6 L⊙, which corresponds to an 06 star. It contains 460 M⊙ of ionized gas. A high-resolution ^13CO image from the Galactic Ring Survey reveals that G25.4NW is part of a more extended star-forming complex with about 104 M⊙ of molecular gas.

A Search for High-velocity Gas Associated H_2O Masers and Ultracompact HII Regions

With the objective of studying the relationships between high-velocity gas and water maser emissions the results of a search from 95 IRAS sources for high-velocity gas associated with star forming molecular clouds are reported. 21 sources have been identified as molecular outflow candidates.

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.

Molecular clouds associated with compact HII regions in Galactic plane

13CO (J = 1 ? 0) emission of massive star forming region including 15 ultracompact and 4 compact HII regions in Galactic plane was mapped with the 13.7 m millimeter wave telescope of Purple Mountain Observatory. The present observations provide the first complete structure of the clouds in 13CO with a higher spatial resolution and a wide-field coverage of 28′ x 45′. Combined with the images of far-infrared emission and dust color temperature obtained from ISSA, various possible dynarnical connections between the compact HII regions and associated clouds were found. We presente some reasons to explain the formation of new dense cold core and molecular emission cavity in the massive star formation and early evolution. The luminosities of excitation stars for all HI1 regions and the main parameters of associated clouds are also derived. The results show that the newborn stars’ luminosities are correlated with the13CO column densities, masses (in 55″beam) and 13CO velocity widths obviously.

Identification of ten new Galactic HII regions

We discovered ten large HII regions in the Sino-German λ6 cm polarization survey of the Galactic plane. They have been identified according to their flat spectral indexes and the high ratio between the 60 μm infrared emission and the λ6 cm emission. The integrated flux densities as well as the sizes of these sources are given at 4800 MHz. Cross-identifications are made with other major radio catalogs.

High-velocity gas associated ultracompact HII regions

We present the results of a survey for high-velocity 12CO (1-0) emission associated H2O masers and ultracompact (UC) HII regions. The aim is to investigate the relationship between H2O masers, CO high-velocity gas (HVG) and their associated infrared sources. Our sample satisfies Wood & Churchwell criterion. Almost 70 % of the sources have full widths (FWs) greater than 15 km@ s?1 at T*a = 100 mK and 15 % have FWs greater than 30 km@ s?1. In most of our objects there is excess high velocity emission in the beam. There is a clear correlation between CO line FWs and far-infrared luminosities: the FW increases with the FIR luminosity. The relation suggests that more luminous sources are likely to be more energetic and able to inject more energy into their surroundings. As a result, larger FW of the CO line could be produced. In most of our sources, the velocities of peak of the H2O emission are in agreement with those of the CO cloud, but a number of them have a large blueshift with respect to the CO peak. These masers might stem from the amplifications of a background source, which may amplify some unobservable weak masers to an observable level.

An MSX infrared analysis of the superbubble around the giant HII region NGC3603

Using the MSX mid-infrared observations,we reveal a 100pc-scale superbubble surrounding the giant HII region NGC3603.We suggest that the diffuse surrounding infrared emission in bands A,C,and D is dominated by that of PAH and the emission in band E is dominated by that of dust grains.The fitted dust temperature is consistent with heating by the central cluster's UV photons.The derived gas-to-dust mass ratio for the bubble shell is of order 102.

Ionization Equilibrium and NLTE Effects on Compact Circumstellar HII Regions

This paper presents the results of an extensive set of calculations about ionization equilibrium and NLTE effects on compact circumstellar HII regions embedded in clouds. In the mode! of a spherically symmetric and isothermal wind with a steady mass loss, pure hydrogen composition as well as Sobolev approximation, our research indicates that compact HII regions are far away from LTE state. The collisional ionization and photoionization from excited levels have great effects on the size of an HII region, the distribution of departure coefficients and the flux ratio of observed spectral lines. They can be used to explain the infrared line excess and the line deficit problems of YSOs. We conclude that it is unreasonable to infer the spectral type, mass loss rate and foreground extinction of the central star from optically thin line recombination theory.

银道面HII区复合体G18．2－0．3的射电及红外发射

本文作者用上海天文台的２５米天线和１２．２ＧＨｚ的接收系统，对银道面附近的一个ＨＩＩ区复合体Ｇ１８．２—０．３进行了射电连续谱观测．采用沿源运动轨迹，对观测曲线进行多子源模型拟合的方法，将该复合体中的６个子源从延展的ＨＩＩ区辐射中分离了出来，并导出了每个子源在１２．２ＧＨｚ频率上的流量和角大小．结合外台站在２６９５ＭＨｚ，４７５０ＭＨｚ和１０．５５ＧＨｚ上的流量还得到了这些子源的辐射频谱．分析表明它们具有热辐射性质．对具有射电复合线（Ｈ７６α）资料和角尺度的４个子源导出了它们的电子密度在（１—３）×１０２ｃｍ－３间．此外通过对Ｇ１８．２—０．３复合体子源ＩＲＡＳ资料的分析和模型拟合还得到了每个子源周围冷尘埃的等效黑体温度．其中４个子源并具有ＩＲＡＳ－ＬＲＳ资料．分析它们得到了与该ＨＩＩ区成协尘埃的性质．根据５个子源的ＩＲＡＳ流量、频带以及色改正因子又求出了这些子源在１—５００μｍ间的总红外光度在２×１０４—１０５Ｌ间．它表明与Ｇ１８．２—０．３中各子源成协的新形成星是一些大质量的ＯＢ型星，它们在同一个延展ＨＩＩ区中如此密集证明了大质量星“致密—堆积”形成模式的合理性．

HGC5930 HII区的环形结构

用美国甚大阵(VLA)对河外棒旋星系NGC5930在2cm,3.6cm波长上进行射电连续辐射的观测,发现HII区呈复杂的环形结构,上面分布着热斑,环的外角径为2.″2,内角径为0.″3,中心部分为空洞,没有探测到射电辐射,HII区的电子密度为80-90cm^(-3),气体质量为10~7个太阳质量单位,NGC5930有非常强的红外辐射,红外光度为射电光度的一百万倍,很陡的巴尔末衰减,是恒星正在剧烈形成的区域。

LAMOST MRS-N Observation of the W80 Region

The spectral observations and analysis for the W80 region are presented by using the data of Medium-Resolution Spectroscopic Survey of Nebulae(MRS-N) with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST).A total of 2982 high-quality nebular spectra have been obtained in the 20 square degree field of view which covers the W80 complex,and the largest sample of spectral data has been established for the first time.The relative intensities,radial velocities(RVs),and full widths at half maximum(FWHMs) are measured with the high spectral resolution of LAMOST MRS-N,for Ha λ6563?,[NⅡ] λλ6548 A,6584 A,and [SⅡ] λλ6716A,6731 A emission lines.In the field of view of the whole W80 region,the strongest line emissions are found to be consistent with the bright nebulae NGC 7000,IC 5070,and LBN 391,and weak line emissions also exist in the Middle Region,where no bright nebulae are detected by the wide-band optical observations.The large-scale spectral observations of the W80 region reveal the systematic spatial variations of RVs and FWHMs,and several unique structural features.A "curved feature" to the east of NGC 7000,and a "jet feature" to the west of LBN 391 are detected to be showing larger RVs.A "wider FWHM region" is identified in the eastern part of NGC 7000.The variations of[S Ⅱ]/Ha ratios display a gradient from southwest to northeast in the NGC 7000 region,and manifest a ring shape around the "W80 bubble" ionized by an O-type star in L935.Further spectral and multi-band observations are guaranteed to investigate in detail the structural features.

A multiwavelength study of the star forming HⅡ region Sh2-82

Based on a multiwavelength study, the interstellar medium and young stel- lar objects （YSOs） around the H II region Sh2-82 have been analyzed. Two molecular clumps were found from the archival data of the Galactic Ring Survey, and using the Two Micron All-Sky Survey catalog, we found two corresponding young clusters embedded in the molecular clumps. The very good relations between CO emission, infrared shells and YSOs suggest that it is probably a triggered star formation region from the expansion of Sh2-82. We further used the data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire from Spitzer to study the YSOs within the two clumps, confirming star formation in this region. By spectral energy distribution fits to each YSO candidate with infrared excess, we derived the slope of the initial mass function. Finally, comparing the H II region＇s dynamical age and the fragmenta- tion time of the molecular shell, we discard the ＂collect and collapse＂ process as being the triggering mechanism for YSO formation. Sh2-82 can be a mixture of other pro- cesses such as radiative-driven implosion and/or collisions with pre-existing clumps.

A Kinematical Study of the NGC 7538 IRS 1 Region

We present high angular resolution images of both NH3 (1, 1) and (2, 2) lines toward NGC 7538 IRS 1. The density and velocity-position plots have been used to study the interaction among the outflows, winds and their environment. For the first time we have found an expanding half-shell of molecular gas around the HII region associated with IRS 1, which may be produced by the interaction of the bipolar outflows and the winds originating in IRS 1-3, and optical HII region NGC 7538 with ambient molecular gas.

S252 HII区—分子云复合体中小尘埃的红外发射

本文利用IRAS资料,详细研究了HII区一分子云复合体S252中12μm频带的辐射强度随辐射场的变化.结果表明,为了解释过量的短波辐射,必须涉及到非常小的尘埃(PAHs及其它小粒子)的非平衡发射过程.这些小尘埃发射总红外光度的36%,其大部分是在λ<25μm的频段辐射。PAHs在HII区中受到辐射场的强烈破坏,而稠密云的屏蔽作用使其相对少地受到影响.一个考虑了PAHs在HII区中的径向分布的模型可以满意地解释观测到的12μm辐射强度随空间的变化.

<i>Spitzer</i>IRAC Colors of Nebulae Associated with Star-Forming Regions

Star-forming regions are often associated with nebulosity. In this study, we investigated infrared diffuse emission in Spitzer IRAC images. The infrared nebula L1527 traces outflows emanating from a low-mass protostar. The nebular color is consistent with the color of a stellar photosphere with large extinction. Nebulae around the HII region W5-East are bright in the infrared. These colors are consistent with the model color of dust containing polycyclic aromatic hydrocarbon (PAH). The strength of ultraviolet irradiation of the nebulae and the small dust fraction were deduced from the infrared colors of the nebulae. We found that the edges of the nebulae are irradiated by strong ultraviolet radiation and have abundant small dust. Dust at the surface of the molecular cloud is thought to be destroyed by ultraviolet radiation from an early-type star.

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.

18个电离氢区的2.5cm射电连续谱观测

十八个致密电离氢区的2.5cm连续谱观测在上海天文台佘山站25m望远镜上于1990年8月完成.望远镜指向精度为20〃,在该波段当仰角为77°时效率为68％,空间分辨率为4.′2.所用接收机中心频率为11.95GHz,带宽为500MHz,系统噪声温度平均为130K.经校准的噪声管用于定标,每次观测同时测量.观测采用等待式或位置调制,所有源在测量时仰角在28°以上,系统误差在10％以内.观测结果经大气吸收改正转换为流量密度.结合Parkes 64m望远镜在6cm的观测结果和气体星云中射电连续谱的一般规律,对结果作了初步分析.