The excitation temperature T_(ex)for molecular emission and absorption lines is an essential parameter for interpreting the molecular environment.This temperature can be obtained by observing multiple molecular transi...The excitation temperature T_(ex)for molecular emission and absorption lines is an essential parameter for interpreting the molecular environment.This temperature can be obtained by observing multiple molecular transitions or hyperfine structures of a single transition,but it remains unknown for a single transition without hyperfine structure lines.Earlier H_(2)CO absorption experiments for a single transition without hyperfine structures adopted a constant value of T_(ex),which is not correct for molecular regions with active star formation and H II regions.For H_(2)CO,two equations with two unknowns may be used to determine the excitation temperature T_(ex)and the optical depthτ,if other parameters can be determined from measurements.Published observational data of the4.83 GHz(λ=6 cm)H_(2)CO(1_(10)-1_(11))absorption line for three star formation regions,W40,M17 and DR17,have been used to verify this method.The distributions of T_(ex)in these sources are in good agreement with the contours of the H110αemission of the H II regions in M17 and DR17 and with the H_(2)CO(1_(10)-1_(11))absorption in W40.The distributions of T_(ex)in the three sources indicate that there can be significant variation in the excitation temperature across star formation and H II regions and that the use of a fixed(low)value results in misinterpretation.展开更多
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, resp...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.展开更多
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 sing...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.展开更多
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 ...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.展开更多
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...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.展开更多
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...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.展开更多
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 regio...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.展开更多
基金funded by the National Key R&D Program of China under grant No.2022YFA1603103partially funded by the Regional Collaborative Innovation Project of Xinjiang Uyghur Autonomous Region under grant No.2022E01050+7 种基金the Tianshan Talent Program of Xinjiang Uygur Autonomous Region under grant No.2022TSYCLJ0005the Natural Science Foundation of Xinjiang Uygur Autonomous Region under grant No.2022D01E06the Chinese Academy of Sciences(CAS)Light of West China Program under grants Nos.xbzg-zdsys-202212,2020-XBQNXZ-017,and 2021-XBQNXZ-028the National Natural Science Foundation of China(NSFC,grant Nos.12173075,11973076,and 12103082)the Xinjiang Key Laboratory of Radio Astrophysics under grant No.2022D04033the Youth Innovation Promotion Association CASfunded by the Chinese Academy of Sciences Presidents International Fellowship Initiative under grants Nos.2022VMA0019 and 2023VMA0030funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan under grant No.AP13067768。
文摘The excitation temperature T_(ex)for molecular emission and absorption lines is an essential parameter for interpreting the molecular environment.This temperature can be obtained by observing multiple molecular transitions or hyperfine structures of a single transition,but it remains unknown for a single transition without hyperfine structure lines.Earlier H_(2)CO absorption experiments for a single transition without hyperfine structures adopted a constant value of T_(ex),which is not correct for molecular regions with active star formation and H II regions.For H_(2)CO,two equations with two unknowns may be used to determine the excitation temperature T_(ex)and the optical depthτ,if other parameters can be determined from measurements.Published observational data of the4.83 GHz(λ=6 cm)H_(2)CO(1_(10)-1_(11))absorption line for three star formation regions,W40,M17 and DR17,have been used to verify this method.The distributions of T_(ex)in these sources are in good agreement with the contours of the H110αemission of the H II regions in M17 and DR17 and with the H_(2)CO(1_(10)-1_(11))absorption in W40.The distributions of T_(ex)in the three sources indicate that there can be significant variation in the excitation temperature across star formation and H II regions and that the use of a fixed(low)value results in misinterpretation.
基金supported by Program 7 of the Presidium of the RAS,“Transitional and Explosive Processes in Astrophysics,”the RFBR(Grant 17-02-00521)
文摘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.
基金supported by the National Natural Science Foundation of China(Grant Nos. 10778703, 10873025)the Program of Light in China’s Western Region(LCWR,Nos. RCPY200605, RCPY200706)
文摘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.
基金Supported by the National Natural Science Foundation of China.
文摘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.
文摘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.
文摘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.
基金the support from the National Natural Science Foundation of China (Grant No. 11073028)the National Basic Research Program of China (973 program, 2012CB821800)+1 种基金the Young Researcher Grant of NAOC the "Hundred-talent program" of the Chinese Academy of Sciences
文摘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.
