The study of multiple molecular spectral lines in gas infalling sources can provide the physical and chemica properties of these sources and help us estimate their evolutionary stages.We report line detections within ...The study of multiple molecular spectral lines in gas infalling sources can provide the physical and chemica properties of these sources and help us estimate their evolutionary stages.We report line detections within the 3 mm band using the FTS wide-sideband mode of the IRAM 30 m telescope toward 20 gas-infalling sources.Using XCLASS,we identify the emission lines of up to 22 molecular species(including a few isotopologues)and on hydrogen radio recombination line in these sources.H^(13)CO^(+),HCO^(+),HCN,HNC,c-C_(3)H_(2),and CCH lines are detected in 15 sources.We estimate the rotation temperatures and column densities of these molecular species using the LTE radiative transfer model,and compare the molecular abundances of these sources with those from nine high mass star-forming regions reported in previous studies and with those from the chemical model.Our results sugges that G012.79-0.20,G012.87-0.22 clump A and B,and G012.96-0.23 clump A may be in the high-mass protostella object stage,while sources with fewer detected species may be in the earlier evolutionary stage.Additionally,th CCH and c-C_(3)H_(2)column densities in our sources reveal a linear correlation,with a ratio of N(CCH)/N(c-C_(3)H_(2)=89.2±5.6),which is higher than the ratios reported in the literature.When considering only sources with lowe column densities,this ratio decreases to 29.0±6.1,consistent with those of diffuse clouds.Furthermore,comparison between the N(CCH)/N(c-C_(3)H_(2))ratio and the sources’physical parameters reveals a correlation,with sources exhibiting higher ratios tending to have higher kinetic temperatures and H2column densities.展开更多
G116.6−26.1 has been newly discovered as a supernova remnant(SNR)through the SRG/eROSITA X-ray survey,located in a high-latitude,low-density region.Its distance and progenitor nature remain uncertain.Our objective is ...G116.6−26.1 has been newly discovered as a supernova remnant(SNR)through the SRG/eROSITA X-ray survey,located in a high-latitude,low-density region.Its distance and progenitor nature remain uncertain.Our objective is to explore the surroundings of SNR G116.6−26.1 to determine its distance and surrounding environmental conditions.High-resolution and sensitive H I observations around G116.6−26.1 from the Fivehundred-meter Aperture Spherical radio Telescope,with an rms level of 1.0 mJy beam^(−1),were utilized to study the distribution of cold gas in this SNR region.Furthermore,an extinction map for this area helps estimate the distance to G116.6−26.1.We identified four H I structures associated with G116.6−26.1 in the local standard of rest velocity range−133.9 to−63.9 km s^(−1):clouds A1,B1,B2,and C1.Together with other components in the A-series and the C-series,they form a large cloud that exhibits a cavity in this SNR region.The A-and C-series share similar velocities,while B1 and B2,both in the SNR area,differ by 10−30 km s^(−1).The X-ray morphology displays deformation features that align spatially with the H I structure C1 boundary interface.Using threedimensional extinction data,we estimate the cloud’s distance to be 2.7_(0.50)^(+3.18) kpc,suggesting that G116.6−26.1 exploded within an H I cloud beyond the Galactic plane,about 2.7 kpc away.展开更多
This paper presents an overview of the QUARKS survey,which stands for Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures."The QUARKS survey is observing139 m...This paper presents an overview of the QUARKS survey,which stands for Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures."The QUARKS survey is observing139 massive clumps covered by 156 pointings at Atacama Large Millimeter/submillimeter Array(ALMA)Band 6(λ~1.3 mm).In conjunction with data obtained from the ALMA-ATOMS survey at Band 3(λ~3 mm),QUARKS aims to carry out an unbiased statistical investigation of massive star formation process within protoclusters down to a scale of 1000 au.This overview paper describes the observations and data reduction of the QUARKS survey,and gives a first look at an exemplar source,the mini-starburst Sgr B2(M).The wide-b and width(7.5 GHz)and high-angular-resolution(~0."3)observations of the QUARKS survey allow for the resolution of much more compact cores than those could be done by the ATOMS survey,and to detect previously unrevealed fainter filamentary structures.The spectral windows cover transitions of species including CO,SO,N_(2)D^(+),SiO,H_(30)α,H_(2)CO,CH_(3)CN,and many other complex organic molecules,tracing gas components with different temperatures and spatial extents.QUARKS aims to deepen our understanding of several scientific topics of massive star formation,such as the mass transport within protoclusters by(hub-)filamentary structures,the existence of massive starless cores,the physical and chemical properties of dense cores within protoclusters,and the feedback from already formed high-mass young protostars.展开更多
We present large-scale(2°×2°)observations toward the molecular cloud M120.1+3.0,using ^(12)CO,^(13)CO and C^(18)O(J=1-0)data from the Purple Mountain Observatory 13.7 m millimeter telescope.The distance...We present large-scale(2°×2°)observations toward the molecular cloud M120.1+3.0,using ^(12)CO,^(13)CO and C^(18)O(J=1-0)data from the Purple Mountain Observatory 13.7 m millimeter telescope.The distance of the cloud is measured to be~1.1 kpc.Using the ^(13)CO data,we identify a main filament F1 and two sub-filaments F2 and F3 in the cloud,which together show a"hub-filament"structure.Filaments F1 and F2 are thermally supercritical.Furthermore,F1 displays clear localized systematic motions in the ^(13)CO position-velocity diagram,which could be explained by accretion along the filament.The mean estimated accretion rate is~132M_(⊙)Myr^(-1).Approximately 150 ^(13)CO clumps are identified in the cloud,of which 39 are gravitationally bound.Most of these virialized clumps are well distributed along the supercritical filaments F1 and F2.Based on the complementary infrared and optical data,we identify~186 young stellar objects in the observed area and extract five clusters within the dense ridge of F1.The calculated star formation rate(SFR)surface densities(∑_(SFR))in the clusters range from 1.4 to 2.5 M_(⊙)Myr^(-1)pc^(-2),with a mean value of~2.0M_(⊙)Myr^(-1)pc^(-2).We therefore regard them as mini-starburst cluster candidates.The comparison between ∑_(SFR) and column density N_(gas) along the skeleton of F1 suggests that star formation is closely related to the dense gas in the cloud.Along the main filament F1,five bipolar outflows are also found.All these results indicate intense star-forming activities in the M120.1+3.0 molecular cloud.展开更多
The most extensive survey of carbon monoxide(CO)gas in the Taurus molecular cloud relied on ^(12)CO and ^(13)CO J=1→0 emission only,distinguishing the region where ^(12)CO is detected without ^(13)CO(named mask 1 reg...The most extensive survey of carbon monoxide(CO)gas in the Taurus molecular cloud relied on ^(12)CO and ^(13)CO J=1→0 emission only,distinguishing the region where ^(12)CO is detected without ^(13)CO(named mask 1 region)from the one where both are detected(mask 2 region)(Goldsmith et al.2008;Pineda et al.2010).We have taken advantage of recent ^(12)CO J=3→2 James Clerk Maxwell Telescope observations,where they include mask 1regions to estimate density,temperature,and N(CO)with a large velocity gradient model.This represents 1395 pixels out of~1.2 million in the mark 1 region.Compared to Pineda et al.(2010)results and assuming a Tkin of 30 K,we find a higher volume density of molecular hydrogen of 3.3×10^(3) cm^(-3),compared to their 250-700 cm^(-3),and a CO column density of 5.7×10^(15)cm^(-2),about a quarter of their value.The differences are important and show the necessity to observe several CO transitions to better describe the intermediate region between the dense cloud and the diffuse atomic medium.Future observations to extend the ^(12)CO J=3→2 mapping further away from the ^(13)COdetected region comprising mask 1 are needed to revisit our understanding of the diffuse portions of dark clouds.展开更多
A series of plane-parallel photodissociation region （PDR） models are calculated using the spectral synthesis code CLOUDY. These models span a wide range of physical conditions, with gas densities of n=10^2-10^6cm^-3...A series of plane-parallel photodissociation region （PDR） models are calculated using the spectral synthesis code CLOUDY. These models span a wide range of physical conditions, with gas densities of n=10^2-10^6cm^-3 and incident far-ultraviolet （FUV） fields of Go=10^0-10^6 （where Go is the FUV flux in units of the local interstellar value）, which are comparable with various astrophysical environments from interstellar diffuse clouds to the dense neutral gas around galactic compact H Ⅱ regions. Based on the calculated results, we study the thermal balance of PDR gas and the emissions of [C Ⅱ], [C I] and [O I] fine-structure lines under different physical conditions. The intensities and strength ratios of the studied lines, which are frequently used as PDR diagnostics, are presented using contour diagrams as functions of n and Go. We compare the calculated PDR surface gas temperatures Ts with those from Kaufman et al. and find that Ts from our models are systematically higher over most of the adopted n-Go parameter space. The predicated line intensities and ratios from our work and those from Kaufman et al. can be different by a factor greater than 10, and such large differences usually occur near the border of our parameter space. The different methods of treating the dust grain physics, the change of H2 formation and dissociation rates, and the improvement in the radiation transfer of line emissions in our CLOUDY models are likely to be the major reasons for the divergences. Our models represent an up-to-date treatment of PDR diagnostic calculations and can be used to interpret observational data. Meanwhile, the uncertainties in the treatment of microphysics and chemical processes in PDR models have significant effects on PDR diagnostics.展开更多
基金supported by the National Key R&D Program of China(No.2022YFA1603102)the National Natural Science Foundation of China(NSFC,Grant Nos.U2031202,12373030,and 11873093)。
文摘The study of multiple molecular spectral lines in gas infalling sources can provide the physical and chemica properties of these sources and help us estimate their evolutionary stages.We report line detections within the 3 mm band using the FTS wide-sideband mode of the IRAM 30 m telescope toward 20 gas-infalling sources.Using XCLASS,we identify the emission lines of up to 22 molecular species(including a few isotopologues)and on hydrogen radio recombination line in these sources.H^(13)CO^(+),HCO^(+),HCN,HNC,c-C_(3)H_(2),and CCH lines are detected in 15 sources.We estimate the rotation temperatures and column densities of these molecular species using the LTE radiative transfer model,and compare the molecular abundances of these sources with those from nine high mass star-forming regions reported in previous studies and with those from the chemical model.Our results sugges that G012.79-0.20,G012.87-0.22 clump A and B,and G012.96-0.23 clump A may be in the high-mass protostella object stage,while sources with fewer detected species may be in the earlier evolutionary stage.Additionally,th CCH and c-C_(3)H_(2)column densities in our sources reveal a linear correlation,with a ratio of N(CCH)/N(c-C_(3)H_(2)=89.2±5.6),which is higher than the ratios reported in the literature.When considering only sources with lowe column densities,this ratio decreases to 29.0±6.1,consistent with those of diffuse clouds.Furthermore,comparison between the N(CCH)/N(c-C_(3)H_(2))ratio and the sources’physical parameters reveals a correlation,with sources exhibiting higher ratios tending to have higher kinetic temperatures and H2column densities.
基金supported by the China National Key Program for Science and Technology Research and Development of China(Nos.2022YFA1602901 and 2023YFA1608204)the China Manned Space Program(Nos.CMS-CSST-2025-A03 and CMSCSST-2025-A10)+3 种基金the National SKA Program of China(No.2022SKA0110201)the National Natural Science Foundation of China(Nos.11873051,11988101,12033008,12041305,12125302,12173016 and 12203065)the CAS Project for Young Scientists in Basic Research grant(No.YSBR-062)support from the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS.
文摘G116.6−26.1 has been newly discovered as a supernova remnant(SNR)through the SRG/eROSITA X-ray survey,located in a high-latitude,low-density region.Its distance and progenitor nature remain uncertain.Our objective is to explore the surroundings of SNR G116.6−26.1 to determine its distance and surrounding environmental conditions.High-resolution and sensitive H I observations around G116.6−26.1 from the Fivehundred-meter Aperture Spherical radio Telescope,with an rms level of 1.0 mJy beam^(−1),were utilized to study the distribution of cold gas in this SNR region.Furthermore,an extinction map for this area helps estimate the distance to G116.6−26.1.We identified four H I structures associated with G116.6−26.1 in the local standard of rest velocity range−133.9 to−63.9 km s^(−1):clouds A1,B1,B2,and C1.Together with other components in the A-series and the C-series,they form a large cloud that exhibits a cavity in this SNR region.The A-and C-series share similar velocities,while B1 and B2,both in the SNR area,differ by 10−30 km s^(−1).The X-ray morphology displays deformation features that align spatially with the H I structure C1 boundary interface.Using threedimensional extinction data,we estimate the cloud’s distance to be 2.7_(0.50)^(+3.18) kpc,suggesting that G116.6−26.1 exploded within an H I cloud beyond the Galactic plane,about 2.7 kpc away.
基金supported by the National Key R&D Program of China(No.2022YFA1603100)the National Natural Science Foundation of China(NSFC)through grants Nos.12203086,12033005,12073061,12122307,and 12103045+12 种基金supported by CPSF No.2022M723278the international partnership program of Chinese Academy of Sciences through grant No.114231K YSB20200009Shanghai Pujiang Program 20PJ1415500the science research grants from the China Manned Space Project with no.CMS-CSST-2021-B06Yunnan Fundamental Research Project(grant No.202301AT070118)sponsored by Natural Science Foundation of Shanghai(No.23ZR1482100)support from the National Natural Science Foundation of China(NSFC)through grants Nos.12273090&12322305the Chinese Academy of Sciences(CAS)‘Light of West China’Program(No.xbzgzdsys-202212)support from the ANID BASAL project FB210003support from the Fondecyt Regular(project code 1220610)partially supported by a Grant-in-Aid for Scientific Research(KAKENHI Number JP22H01271 and JP23H01221)of JSPSsupported by JSPS KAKENHI(grant No.JP20H05645)sponsored(in part)by the Chinese Academy of Sciences(CAS),through a grant to the CAS South America Center for Astronomy(CASSACA)in Santiago,Chile。
文摘This paper presents an overview of the QUARKS survey,which stands for Querying Underlying mechanisms of massive star formation with ALMA-Resolved gas Kinematics and Structures."The QUARKS survey is observing139 massive clumps covered by 156 pointings at Atacama Large Millimeter/submillimeter Array(ALMA)Band 6(λ~1.3 mm).In conjunction with data obtained from the ALMA-ATOMS survey at Band 3(λ~3 mm),QUARKS aims to carry out an unbiased statistical investigation of massive star formation process within protoclusters down to a scale of 1000 au.This overview paper describes the observations and data reduction of the QUARKS survey,and gives a first look at an exemplar source,the mini-starburst Sgr B2(M).The wide-b and width(7.5 GHz)and high-angular-resolution(~0."3)observations of the QUARKS survey allow for the resolution of much more compact cores than those could be done by the ATOMS survey,and to detect previously unrevealed fainter filamentary structures.The spectral windows cover transitions of species including CO,SO,N_(2)D^(+),SiO,H_(30)α,H_(2)CO,CH_(3)CN,and many other complex organic molecules,tracing gas components with different temperatures and spatial extents.QUARKS aims to deepen our understanding of several scientific topics of massive star formation,such as the mass transport within protoclusters by(hub-)filamentary structures,the existence of massive starless cores,the physical and chemical properties of dense cores within protoclusters,and the feedback from already formed high-mass young protostars.
基金supported by the National Key R&D Program of China(grant No.2017YFA0402702)the National Natural Science Foundation of China(NSFC,Grant Nos.12041305,12173090 and 12073079)+2 种基金the CAS International Cooperation Program(grant No.114332KYSB20190009)sponsored by the National Key R&D Program of China with grant 2017YFA0402701the CAS Key Research Program of Frontier Sciences with grant QYZDJ-SSW-SLH047。
文摘We present large-scale(2°×2°)observations toward the molecular cloud M120.1+3.0,using ^(12)CO,^(13)CO and C^(18)O(J=1-0)data from the Purple Mountain Observatory 13.7 m millimeter telescope.The distance of the cloud is measured to be~1.1 kpc.Using the ^(13)CO data,we identify a main filament F1 and two sub-filaments F2 and F3 in the cloud,which together show a"hub-filament"structure.Filaments F1 and F2 are thermally supercritical.Furthermore,F1 displays clear localized systematic motions in the ^(13)CO position-velocity diagram,which could be explained by accretion along the filament.The mean estimated accretion rate is~132M_(⊙)Myr^(-1).Approximately 150 ^(13)CO clumps are identified in the cloud,of which 39 are gravitationally bound.Most of these virialized clumps are well distributed along the supercritical filaments F1 and F2.Based on the complementary infrared and optical data,we identify~186 young stellar objects in the observed area and extract five clusters within the dense ridge of F1.The calculated star formation rate(SFR)surface densities(∑_(SFR))in the clusters range from 1.4 to 2.5 M_(⊙)Myr^(-1)pc^(-2),with a mean value of~2.0M_(⊙)Myr^(-1)pc^(-2).We therefore regard them as mini-starburst cluster candidates.The comparison between ∑_(SFR) and column density N_(gas) along the skeleton of F1 suggests that star formation is closely related to the dense gas in the cloud.Along the main filament F1,five bipolar outflows are also found.All these results indicate intense star-forming activities in the M120.1+3.0 molecular cloud.
基金the National Natural Science Foundation of China(NSFC,grant Nos.11988101,11725313,and U1931117)the International Partnership Program of Chinese Academy of Sciences(grant No.114A11KYSB20210010)supported by the Natural Science Foundation of Jiangsu Province(grant No.BK20201108)。
文摘The most extensive survey of carbon monoxide(CO)gas in the Taurus molecular cloud relied on ^(12)CO and ^(13)CO J=1→0 emission only,distinguishing the region where ^(12)CO is detected without ^(13)CO(named mask 1 region)from the one where both are detected(mask 2 region)(Goldsmith et al.2008;Pineda et al.2010).We have taken advantage of recent ^(12)CO J=3→2 James Clerk Maxwell Telescope observations,where they include mask 1regions to estimate density,temperature,and N(CO)with a large velocity gradient model.This represents 1395 pixels out of~1.2 million in the mark 1 region.Compared to Pineda et al.(2010)results and assuming a Tkin of 30 K,we find a higher volume density of molecular hydrogen of 3.3×10^(3) cm^(-3),compared to their 250-700 cm^(-3),and a CO column density of 5.7×10^(15)cm^(-2),about a quarter of their value.The differences are important and show the necessity to observe several CO transitions to better describe the intermediate region between the dense cloud and the diffuse atomic medium.Future observations to extend the ^(12)CO J=3→2 mapping further away from the ^(13)COdetected region comprising mask 1 are needed to revisit our understanding of the diffuse portions of dark clouds.
文摘A series of plane-parallel photodissociation region （PDR） models are calculated using the spectral synthesis code CLOUDY. These models span a wide range of physical conditions, with gas densities of n=10^2-10^6cm^-3 and incident far-ultraviolet （FUV） fields of Go=10^0-10^6 （where Go is the FUV flux in units of the local interstellar value）, which are comparable with various astrophysical environments from interstellar diffuse clouds to the dense neutral gas around galactic compact H Ⅱ regions. Based on the calculated results, we study the thermal balance of PDR gas and the emissions of [C Ⅱ], [C I] and [O I] fine-structure lines under different physical conditions. The intensities and strength ratios of the studied lines, which are frequently used as PDR diagnostics, are presented using contour diagrams as functions of n and Go. We compare the calculated PDR surface gas temperatures Ts with those from Kaufman et al. and find that Ts from our models are systematically higher over most of the adopted n-Go parameter space. The predicated line intensities and ratios from our work and those from Kaufman et al. can be different by a factor greater than 10, and such large differences usually occur near the border of our parameter space. The different methods of treating the dust grain physics, the change of H2 formation and dissociation rates, and the improvement in the radiation transfer of line emissions in our CLOUDY models are likely to be the major reasons for the divergences. Our models represent an up-to-date treatment of PDR diagnostic calculations and can be used to interpret observational data. Meanwhile, the uncertainties in the treatment of microphysics and chemical processes in PDR models have significant effects on PDR diagnostics.
