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.

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.

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.

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.

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.

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 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.

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.

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.

LAMOST Medium-Resolution Spectral Survey of Galactic Nebulae(LAMOST MRS-N):An overview of scientific goals and survey plan

Since Sep.2018,LAMOST has started the medium-resolution(R~7500)spectral survey(MRS).We proposed the spectral survey of Galactic nebulae,including HⅡregions,HH objects,supernova remnants,planetary nebulae and the special stars with MRS(LAMOST MRS-N).LAMOST MRS-N covers about 1700 square degrees of the northern Galactic plane within 40°<l<215°and-5°<b<5°.In this 5-year survey,we plan to observe about 500 thousand nebulae spectra.According to the commissioning observations,the nebulae spectra can provide precise radial velocity with uncertainty less than 1 km s^(-1).These high-precision spectral data are of great significance to our understanding of star formation and evolution.

Gas compression and likely triggered star formation in the infrared bubble N107

The expansion of HII regions can regulate the evolution of their natal clouds and the star for-mation therein. Infrared dust bubbles, which are frequently associated with HII regions, are ideal labora-tories to test whether impulse（s） driven by the expanding bubbles enhances or suppresses star-formation. In this work, we present a comprehensive study of a 20-pc scale infrared bubble N107 to reveal the com- pression of the neutral gas and associated star-forming activities. We obtain column density （NH2） and dust temperature （Tdust） maps via fitting modified blackbodies to multi-band far-infrared Herschel data. The shell structure can be recognized on the column density map. The molecular gas along the rim of N107 fragments into 94 dense clumps at an angular resolution of 18＂. Besides, based on the GLIMPSE point source catalog, we have identified 228 young stellar objects （YSOs） which are categorized into 55 Class I objects, 127 Class II objects and 46 transition disks （TDs）. The 94 clumps and 55 Class I type YSOs are mainly distributed along the shell, which may suggest triggered star formation exists in N107. In addition, analysis of NH2 probability density functions （PDFs） helps us reveal the condition of natal clouds. The two lognormal profiles of PDFs suggest that the surrounding molecular gas has been compressed due to expansion of the bubble. This compression may trigger the star formation process. Moreover, we find the shape of the PDFs changed after removing the background. Taken together, this big bubble seems to compress the surrounding gas and strongly regulate star formation therein.

Gas emission and dynamics in the infrared dark cloud G31.23＋0.05

We performed a multiwavelength study towards the infrared dark cloud （IRDC） G31.23＋0.05 with new CO observations from Purple Mountain Observatory and archival data （the GLIMPSE, MIPSGAL, HERSCHEL, ATLASGAL, BGPS and NVSS surveys）. From these observations, we iden- tified three IRDCs with systemic velocities of 108.36 ± 0.06 （cloud A）, 104.22 ± 0.11 （cloud B） and 75.73 ± 0.07 km s-1 （cloud C） in the line of sight towards IRDC G31.23. Analyses of the molecular and dust emission suggest that cloud A is a filamentary structure containing a young stellar object; clouds B and C both include a starless core. Clouds A and B are gravitationally bound and have a chance to form stars. In addition, the velocity information and the position-velocity diagram suggest that clouds A and B are adjacent in space and provide a clue hinting at a possible cloud-cloud collision. Additionally, the distribution of dust temperature shows a temperature bubble. The compact core in cloud A is associated with an UCHII region, an IRAS source, H20 masers, CH3OH masers and OH masers, suggesting that massive star formation is active there. We estimate the age of the HII region to be （0.03-0.09）Myr, indicating that the star inside is young.

Statistical Properties of 6.7 GHz Methanol Maser Sources

We present a statistical analysis of 482 6.7 GHz methanol maser sources from the available literature, on their maser emission and the characteristics of their associated infrared sources. On the color-color diagram, more than 70% of the objects fall within a very small region (0.57 ≤ [25-12] ≤ 1.30 and 1.30 ≤ [60-12] ≤ 2.50). This suggests that 6.7 GHz methanol maser emission occurs only within a very short evolutionary phase during the earliest stage of star formation. The velocity ranges of the masers belong to two main groups: one from 1 to 10 km s?1, and one from about 11 to 20 km s?1. These velocity ranges indicate that the masers are probably associated with both disks and outflows. The correlations between the maser and infrared flux densities, and between the maser and infrared luminosities, suggest that far-infrared radiation is a possible pumping mechanism for the masers which most probably originate from some outer molecular envelopes or disks.

Stellar X-ray Sources in the Rosette Nebula

We present optical photometric and spectroscopic studies of ROSAT X-ray stellar sources in the Rosette Nebula star-forming region. The brightest X-ray sources are either massive stars or active T Tauri stars associated with the open cluster NGC 2244, or are foreground stars. Some of the spectra of the young stars newly identified in the region are presented.

A Survey and Statistics of Interstellar OH and H_2O Masers

We present a statistical analysis of a sky survey of interstellar H2O and OH masers. These masers can be classified into three categories: isolated H2O masers, isolated OH masers, and simple OH/H2O maser associations. The total number of sources in each category is of the same order of magnitude, and as an evolutionary phase they can maintain ~ 105 yr. An improved radiative pumping mechanism is proposed. This model avoids some of the deficiencies of previous radiative models, such as shortage of exciting photons. The statistical results obtained from the survey can be interpreted by the new mechanism together with the evolutionary model in which the gravitational force of the central stellar objects is responsible for the HII region.

The Role of Magnetic Fields in Triggered Star Formation of RCW 120

We report on the near-infrared polarimetric observations of RCW 120 with the 1.4 m IRSF telescope.The starlight polarization of the background stars reveals for the first time the magnetic field of RCW 120.The global magnetic field of RCW 120 is along the direction of 20°,parallel to the Galactic plane.The field strength on the plane of the sky is 100 ± 26 μG.The magnetic field around the eastern shell shows evidence of compression by the H Ⅱ region.The external pressure(turbulent pressure+ magnetic pressure) and the gas density of the ambient cloud are minimum along the direction where RCW 120 breaks out,which explains the observed elongation of RCW 120.The dynamical age of RCW 120,depending on the magnetic field strength,is~1.6 Myr for field strength of100 μG,older than the hydrodynamic estimates.In direction perpendicular to the magnetic field,the density contrast of the western shell is greatly reduced by the strong magnetic field.The strong magnetic field in general reduces the efficiency of triggered star formation,in comparison with the hydrodynamic estimates.Triggered star formation via the "collect and collapse" mechanism could occur in the direction along the magnetic field.Core formation efficiency(CFE) is found to be higher in the southern and eastern shells of RCW 120 than in the infrared dark cloud receiving little influence from the H Ⅱ region,suggesting increase in the CFE related to triggering from ionization feedback.

DEFPOS and Its First Results

A spectrometer was built to examine the interstellar medium (ISM) using the hydrogen Balmer α line. It is called Dual Etalon Fabry-Perot Optical Spectrometer (DEFPOS). DEFPOS will be coupled to coudé exit of the 150 cm telescope (RTT150) installed at TüBITAK National Observatory (TUG). DEFPOS was ready for observations about two years ago, but work was still continuing on the RTT150 coudé exit alignment. So we have started observing HII regions with DEFPOS without the RTT150. We present here some characteristics of the instrument and some of the results obtained.

Hα measurements using DEFPOS/RTT150 Telescope: Instrumentation and observations

To investigate the physical properties of HII regions and some PNe about 4＇ in size, a DEFPOS Fabry-Perot spectrometer has been redesigned and set up at the coude exit of the 150cm RTT150 telescope （f/48） at TUBITAK National Observatory （Antalya/Baklrhtepe, Turkey）. The spectrometer has a 4＇ circular field of view and a velocity resolution of 27.27 km s^-1 （a spectral resolving power of 11000） over a 200 km s^-1 spectral window near Hα. This work presents the details of the newly redesigned instrument for coude observations, the data reduction techniques and finally presents some physical results of our new Hα observations selected from the Reynolds et al. （2005） and Fich et al. （1990） papers. The DEFPOS system has been fully tested and the first observations of HII regions and PNe in the Galaxy are used to illustrate the power of the instrument. We feel that our first Fabry-Perot observations can provide a powerful tool for the study of objects with small angular size. In the future, we are planning to prepare a catalog including some physical properties such as radial velocity, line width, and intensity of some PNe and HII regions close to the 4＇ field of view.

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.

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.