In current photoionization models, determination of the ionization structure of the nebulae is a crucial part of the calculations for non-uniform hydrogen density. We have been tried to compute temperature fluctuation...In current photoionization models, determination of the ionization structure of the nebulae is a crucial part of the calculations for non-uniform hydrogen density. We have been tried to compute temperature fluctuations of electron and electron density by changing hydrogen density by scale factor of 10 at high temperature of blackbody. We have studied the ionization structure of hydrogen and helium by means of cloudy C13.01 codes. We find a reasonable close agreement of the computed value. Moreover, the ionization structure of oxygen at ionization stages of, O I - O IV, in gaseous nebulae are studied by changing non uniform hydrogen density with power law. Our simulation also shows that how the change of this density affect temperature fluctuations, electron density and ionization structures of oxygen, helium and hydrogen with and without grains. The result also shows the impact of the forbidden lines of [O III] and [O II] to cool down the temperature of electron.展开更多
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 spec...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.展开更多
We present the dependence of electron temperature fluctuations of O++ and H+ by the chemical abundances of oxygen and nitrogen. Models assume that hydrogen density is uniform in one case and non uniform in the second ...We present the dependence of electron temperature fluctuations of O++ and H+ by the chemical abundances of oxygen and nitrogen. Models assume that hydrogen density is uniform in one case and non uniform in the second case, which vary with the distance from the central star. The abundances of oxygen and nitrogen change by scale factor 5 and 1/5. Our analysis suggests that temperature fluctuations are consistent with photoionization. Using the cloudy photoionization code, we found a reasonable close agreement of the computed value with the one that was done before this work. Our simulation also shows that how change of abundances affects temperature fluctuations and its value is less than 0.01.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
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 TUBITA...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.展开更多
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 R...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.展开更多
文摘In current photoionization models, determination of the ionization structure of the nebulae is a crucial part of the calculations for non-uniform hydrogen density. We have been tried to compute temperature fluctuations of electron and electron density by changing hydrogen density by scale factor of 10 at high temperature of blackbody. We have studied the ionization structure of hydrogen and helium by means of cloudy C13.01 codes. We find a reasonable close agreement of the computed value. Moreover, the ionization structure of oxygen at ionization stages of, O I - O IV, in gaseous nebulae are studied by changing non uniform hydrogen density with power law. Our simulation also shows that how the change of this density affect temperature fluctuations, electron density and ionization structures of oxygen, helium and hydrogen with and without grains. The result also shows the impact of the forbidden lines of [O III] and [O II] to cool down the temperature of electron.
基金supported by the National Natural Science Foundation of China(Grant Nos.12073051,12090040,12090041,11733006,11403061,11903048,U1631131,11973060,12090044,12073039,11633009,U1531118,11403037,11225316,11173030,11303038,Y613991N01,U1531245,11833006)the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences+4 种基金the Key Research Program of Frontier Sciences,CAS(Grant No.QYZDY-SSW-SLH007)the supports from the Science and Technology Development Fund,Macao SAR(file No.0007/2019/A)Faculty Research Grants of the Macao University of Science and Technology(No.FRG19-004-SSI)a National Major Scientific Project built by the Chinese Academy of SciencesFunding for the project has been provided by the National Development and Reform Commission。
文摘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.
文摘We present the dependence of electron temperature fluctuations of O++ and H+ by the chemical abundances of oxygen and nitrogen. Models assume that hydrogen density is uniform in one case and non uniform in the second case, which vary with the distance from the central star. The abundances of oxygen and nitrogen change by scale factor 5 and 1/5. Our analysis suggests that temperature fluctuations are consistent with photoionization. Using the cloudy photoionization code, we found a reasonable close agreement of the computed value with the one that was done before this work. Our simulation also shows that how change of abundances affects temperature fluctuations and its value is less than 0.01.
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This work is supported by TUBITAK (the Scientific and Technical Research Council of Turkey) with grant number 104T252.
文摘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.
基金funded by the National Science Foundation undergrants AST-9800334,AST-0098562,AST-0100793,AST-0228993,& AST-0507657
文摘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.