We present the most comprehensive catalog of 12.2 GHz methanol maser sources within the Milky Way to date,consisting of 45712.2 GHz methanol masers associated with 10856.7 GHz methanol masers,resulting in a detection ...We present the most comprehensive catalog of 12.2 GHz methanol maser sources within the Milky Way to date,consisting of 45712.2 GHz methanol masers associated with 10856.7 GHz methanol masers,resulting in a detection rate of 42%.Distances to these sources are derived from the Bar and Spiral Structure Legacy Survey project Distance Calculator.Our analysis shows that both 6.7 and 12.2 GHz methanol masers are more likely to be excited near galactocentric distances of 5–6 kpc,with the detection rate of 12.2 GHz methanol masers decreasing as the galactocentric distance increases.There are no significant differences in the detection rates of 12.2 GHz masers across the four spiral arms,which consistently range between 40%and 50%.However,the detection rate of12.2 GHz methanol masers tends to be higher in the heads of the spiral arms compared to the tails.Analysis of data from the APEX Telescope Large Area Survey of the Galaxy(ATLASGAL)indicates that the luminosity of6.7 GHz masers peaks at a clump dust temperature of about 30 K,while that of 12.2 GHz masers grows with increasing dust temperature.Clumps associated with 12.2 GHz methanol masers generally have higher dust temperatures,bolometric luminosities,and hydrogen densities than those associated only with 6.7 GHz methanol masers or without either maser.Furthermore,clumps in the HⅡregion stage exhibit a higher detection rate of12.2 GHz masers compared to those in other stages,as indicated by the evolutionary stages derived from the ATLASGAL survey results.展开更多
Leveraging the high resolution,sensitivity,and wide frequency coverage of the Atacama Large Millimeter/submillimeter Array(ALMA),the QUARKS survey,standing for“Querying Underlying mechanisms of massive star formation...Leveraging the high resolution,sensitivity,and wide frequency coverage of the Atacama Large Millimeter/submillimeter Array(ALMA),the QUARKS survey,standing for“Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures”,is observing 139 massive starforming clumps at ALMA Band 6(λ~1.3 mm).This paper introduces the Atacama Compact Array(ACA)7 m data of the QUARKS survey,describing the ACA observations and data reduction.Combining multiwavelength data,we provide the first edition of QUARKS atlas,offering insights into the multiscale and multiphase interstellar medium in high-mass star formation.The ACA 1.3 mm catalog includes 207 continuum sources that are called ACA sources.Their gas kinetic temperatures are estimated using three formaldehyde transitions with a non-LTE radiation transfer model,and the mass and density are derived from a dust emission model.The ACA sources are massive(16–84 percentile values of 6–160 M_(⊙)),gravity-dominated(M∝R^(1.1))fragments within massive clumps,with supersonic turbulence(M>1)and embedded star-forming protoclusters.We find a linear correlation between the masses of the fragments and the massive clumps,with a ratio of 6%between the two.When considering fragments as representative of dense gas,the ratio indicates a dense gas fraction(DGF)of 6%,although with a wide scatter ranging from 1%to 10%.If we consider the QUARKS massive clumps to be what is observed at various scales,then the size-independent DGF indicates a self-similar fragmentation or collapsing mode in protocluster formation.With the ACA data over four orders of magnitude of luminosity-to-mass ratio(L/M),we find that the DGF increases significantly with L/M,which indicates clump evolutionary stage.We observed a limited fragmentation at the subclump scale,which can be explained by a dynamic global collapse process.展开更多
Considering that the existence of relativistic particles in the protostellar jet has been confirmed by the detection of linearly polarized radio emission from the HH 80–81 jet,we search for gamma-rays from the HH 80...Considering that the existence of relativistic particles in the protostellar jet has been confirmed by the detection of linearly polarized radio emission from the HH 80–81 jet,we search for gamma-rays from the HH 80–81 system using ten-year Fermi-LAT observations.A significant point-likeγ-ray excess is found in the direction of the HH80–81 system with the Test-Statistic value>100,which is likely produced in the HH 80–81 jet.Theγ-ray spectrum extends only to 1 Ge V with a photon index of 3.5.No significant variability is found in the gamma-ray emission.It is discussed that the properties of HH 80–81 jet suffice for producing the observedγ-rays.展开更多
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） an...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.展开更多
We present Caltech Submillimeter Observatory CO （2-1） and Spitzer IRAC observations toward IRAS 22506＋5944, which is a 104 Lo massive star-forming region. The CO （2-1） maps show an east-west bipolar molecular out...We present Caltech Submillimeter Observatory CO （2-1） and Spitzer IRAC observations toward IRAS 22506＋5944, which is a 104 Lo massive star-forming region. The CO （2-1） maps show an east-west bipolar molecular outflow originating from the 3 mm dust continuum peak. The Spitzer IRAC color-composite image reveals a pair of bow-shaped tips which are prominent in excess 4.5 p.m emission and are located at the leading fronts of the bipolar outflow, providing compelling evidence for the existence of bow-shocks as the driving agents of the molecular outflow. By comparing our CO （2- 1） observations with previously published CO （1-0） data, we find that the CO （2-1）/（1-0） line ratio increases from low （-5 km s- 1） to moderate （- 8-12 km s- 1） velocities, and then decreases at higher velocities. This is qualitatively consistent with the scenario that the molecular outflow is driven by multiple bow-shocks. We also revisit the position-velocity diagram of the CO （1-0） data, and find two spur structures along the outflow axis, which are further evidence for the presence of multiple jet bow- shocks. Finally, power-law fittings to the mass spectrum of the outflow gives power law indexes more consistent with the jet bow-shock model than the wide-angle wind model.展开更多
基金supported by the National Key R&D Program of China(2022YFA1603102)the National Natural Science Foundation of China(11873002,12011530065,and 11590781)China Postdoctoral Science Foundation(2023M740803)。
文摘We present the most comprehensive catalog of 12.2 GHz methanol maser sources within the Milky Way to date,consisting of 45712.2 GHz methanol masers associated with 10856.7 GHz methanol masers,resulting in a detection rate of 42%.Distances to these sources are derived from the Bar and Spiral Structure Legacy Survey project Distance Calculator.Our analysis shows that both 6.7 and 12.2 GHz methanol masers are more likely to be excited near galactocentric distances of 5–6 kpc,with the detection rate of 12.2 GHz methanol masers decreasing as the galactocentric distance increases.There are no significant differences in the detection rates of 12.2 GHz masers across the four spiral arms,which consistently range between 40%and 50%.However,the detection rate of12.2 GHz methanol masers tends to be higher in the heads of the spiral arms compared to the tails.Analysis of data from the APEX Telescope Large Area Survey of the Galaxy(ATLASGAL)indicates that the luminosity of6.7 GHz masers peaks at a clump dust temperature of about 30 K,while that of 12.2 GHz masers grows with increasing dust temperature.Clumps associated with 12.2 GHz methanol masers generally have higher dust temperatures,bolometric luminosities,and hydrogen densities than those associated only with 6.7 GHz methanol masers or without either maser.Furthermore,clumps in the HⅡregion stage exhibit a higher detection rate of12.2 GHz masers compared to those in other stages,as indicated by the evolutionary stages derived from the ATLASGAL survey results.
基金upported by the National Natural Science Foundation of China(NSFC,Grant No.12033005)the National Key R&D Program of China(No.2022YFA1603102)+2 种基金the China Manned Space Project(CMS-CSST-2021-A09,CMS-CSST-2021-B06)the China-Chile Joint Research Fund(CCJRF No.2211)support from the Tianchi Talent Program of Xinjiang Uygur Autonomous Region。
文摘Leveraging the high resolution,sensitivity,and wide frequency coverage of the Atacama Large Millimeter/submillimeter Array(ALMA),the QUARKS survey,standing for“Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures”,is observing 139 massive starforming clumps at ALMA Band 6(λ~1.3 mm).This paper introduces the Atacama Compact Array(ACA)7 m data of the QUARKS survey,describing the ACA observations and data reduction.Combining multiwavelength data,we provide the first edition of QUARKS atlas,offering insights into the multiscale and multiphase interstellar medium in high-mass star formation.The ACA 1.3 mm catalog includes 207 continuum sources that are called ACA sources.Their gas kinetic temperatures are estimated using three formaldehyde transitions with a non-LTE radiation transfer model,and the mass and density are derived from a dust emission model.The ACA sources are massive(16–84 percentile values of 6–160 M_(⊙)),gravity-dominated(M∝R^(1.1))fragments within massive clumps,with supersonic turbulence(M>1)and embedded star-forming protoclusters.We find a linear correlation between the masses of the fragments and the massive clumps,with a ratio of 6%between the two.When considering fragments as representative of dense gas,the ratio indicates a dense gas fraction(DGF)of 6%,although with a wide scatter ranging from 1%to 10%.If we consider the QUARKS massive clumps to be what is observed at various scales,then the size-independent DGF indicates a self-similar fragmentation or collapsing mode in protocluster formation.With the ACA data over four orders of magnitude of luminosity-to-mass ratio(L/M),we find that the DGF increases significantly with L/M,which indicates clump evolutionary stage.We observed a limited fragmentation at the subclump scale,which can be explained by a dynamic global collapse process.
基金financial supports from the National Natural Science Foundation of China(NSFC-11803081,NSFC-U1931114,NSFC-U2031205 and NSFC-12163006)the joint foundation of Department of Science and Technology of Yunnan Province and Yunnan University(2018FY001(-003))supported by the CAS Youth Innovation Promotion Association and Basic research Program of Yunnan Province(202001AW070013)。
文摘Considering that the existence of relativistic particles in the protostellar jet has been confirmed by the detection of linearly polarized radio emission from the HH 80–81 jet,we search for gamma-rays from the HH 80–81 system using ten-year Fermi-LAT observations.A significant point-likeγ-ray excess is found in the direction of the HH80–81 system with the Test-Statistic value>100,which is likely produced in the HH 80–81 jet.Theγ-ray spectrum extends only to 1 Ge V with a photon index of 3.5.No significant variability is found in the gamma-ray emission.It is discussed that the properties of HH 80–81 jet suffice for producing the observedγ-rays.
基金Supported by the National Natural Science Foundation of China
文摘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.
基金the National Natural Science Foundation of China(Grant Nos.11473011 and 11590781)
文摘We present Caltech Submillimeter Observatory CO （2-1） and Spitzer IRAC observations toward IRAS 22506＋5944, which is a 104 Lo massive star-forming region. The CO （2-1） maps show an east-west bipolar molecular outflow originating from the 3 mm dust continuum peak. The Spitzer IRAC color-composite image reveals a pair of bow-shaped tips which are prominent in excess 4.5 p.m emission and are located at the leading fronts of the bipolar outflow, providing compelling evidence for the existence of bow-shocks as the driving agents of the molecular outflow. By comparing our CO （2- 1） observations with previously published CO （1-0） data, we find that the CO （2-1）/（1-0） line ratio increases from low （-5 km s- 1） to moderate （- 8-12 km s- 1） velocities, and then decreases at higher velocities. This is qualitatively consistent with the scenario that the molecular outflow is driven by multiple bow-shocks. We also revisit the position-velocity diagram of the CO （1-0） data, and find two spur structures along the outflow axis, which are further evidence for the presence of multiple jet bow- shocks. Finally, power-law fittings to the mass spectrum of the outflow gives power law indexes more consistent with the jet bow-shock model than the wide-angle wind model.
