Sulfur-bearing species are widely utilized to investigate the physical structure of star-forming regions in interstellar media;however,the underlying sulfur chemistry in these environments remains poorly understood.Th...Sulfur-bearing species are widely utilized to investigate the physical structure of star-forming regions in interstellar media;however,the underlying sulfur chemistry in these environments remains poorly understood.Therefore,further studies of S-bearing species are fundamentally important,as they can enhance our understanding of the physical evolution of star-forming regions.This study presents observations of C_(2)S and C_(3)S in L1544,acquired using the Nanshan 26-m radio telescope,along with simulations of their chemical behavior using a one-dimensional physical model.The simulation results reveal significant radial variations in the column densities of C_(2)S and C_(3)S.Additionally,the column densities of both molecules are found to be sensitive to the cosmic ray ionization rate at several radial positions,while variations in the C/O ratio have comparatively minimal impact on L1544.展开更多
Infrared(IR)spectral energy distribution(SED)is the major tracer of protoplanetary disks.It was recently proposed to use the near-to-mid IR(or K-24)SED slopeαdefined between 2 and 24μm as a potential quantitative tr...Infrared(IR)spectral energy distribution(SED)is the major tracer of protoplanetary disks.It was recently proposed to use the near-to-mid IR(or K-24)SED slopeαdefined between 2 and 24μm as a potential quantitative tracer of disk age.We critically examine the viability of this idea and confront it with additional statistics of IR luminosities and SED shapes.We point out that,because the statistical properties of most of the complicated physical factors involved in disk evolution are still poorly understood in a quantitative sense,the only viable way is to assume them to be random so that an idealized“average disk”can be defined,which allows theαhistogram to trace its age.We confirm that the statistics of the zeroth order(luminosity),first order(slopeα),and second order characteristics(concavity)of the observed K-24 SEDs indeed carry useful information upon the evolutionary processes of the“average disk”.We also stress that intrinsic diversities in K-24 SED shapes and luminosities are always large at the level of individual stars so that the application of the evolutionary path of the“average disk”to individual stars must be done with care.The data of most curves in plots are provided on GitHub(Disk-age package https://github.com/starage/disk-age/).展开更多
In this paper,we present a new gas-grain chemical code for interstellar clouds written in pure Python(GGCHEMPY(GGCHEMPY is available on https://github.com/JixingGE/GGCHEMPY)).By combining with the high-performance Pyt...In this paper,we present a new gas-grain chemical code for interstellar clouds written in pure Python(GGCHEMPY(GGCHEMPY is available on https://github.com/JixingGE/GGCHEMPY)).By combining with the high-performance Python compiler Numba,GGCHEMPY is as efficient as the Fortran-based version.With the Python features,flexible computational workflows and extensions become possible.As a showcase,GGCHEMPY is applied to study the general effects of three-dimensional projection on molecular distributions using a two-core system which can be easily extended for more complex cases.By comparing the molecular distribution differences between two overlapping cores and two merging cores,we summarized the typical chemical differences such as N2 H+,HC3 N,C2 S,H2 CO,HCN and C2 H,which can be used to interpret 3 D structures in molecular clouds.展开更多
There have been several studies on sulfur depletion in dense cores like TMC-1(Taurus Molecular Cloud 1),employing updated reaction networks for sulfur species to explain the missing sulfur in the gas within dense clou...There have been several studies on sulfur depletion in dense cores like TMC-1(Taurus Molecular Cloud 1),employing updated reaction networks for sulfur species to explain the missing sulfur in the gas within dense clouds.Most of these studies used a C/O ratio of 0.7 or lower.We present NSRT(NanShan 26m Radio Telescope)observations of TMC-1 alongside results from time-dependent chemical simulations using an updated chemical network.Our findings highlight the impact of the C/O ratio on the gas-phase evolution of C2S and C3S.The simulation results show that the C/O ratio is an important parameter,playing a fundamental role in determining the gas-phase abundances of sulfur species in dense cores.展开更多
基金the support from the Natural Science Foundation of Xinjiang Uygur Autonomous Region(Grant No.2024D01E37)the National Science Foundation of China(Grant No.12473025)+5 种基金funded by the National Natural Science Foundation of China(Grant Nos.12373026,12203091,12173075,and 11973076)the Xinjiang Tianchi Talent Program(2024)the support from the Xinjiang Tianchi Talent Program(2023)the Shanghai Natural Science Foundation(Grant No.22ZR1421400)the Natural Science Foundation of Xinjiang Uygur Autonomous Region(Grant No.2022D01A156)partially funded by the Regional Collaborative Innovation Project of Xin jiang Uyghur Autonomous Region(Grant No.2022E01050)。
文摘Sulfur-bearing species are widely utilized to investigate the physical structure of star-forming regions in interstellar media;however,the underlying sulfur chemistry in these environments remains poorly understood.Therefore,further studies of S-bearing species are fundamentally important,as they can enhance our understanding of the physical evolution of star-forming regions.This study presents observations of C_(2)S and C_(3)S in L1544,acquired using the Nanshan 26-m radio telescope,along with simulations of their chemical behavior using a one-dimensional physical model.The simulation results reveal significant radial variations in the column densities of C_(2)S and C_(3)S.Additionally,the column densities of both molecules are found to be sensitive to the cosmic ray ionization rate at several radial positions,while variations in the C/O ratio have comparatively minimal impact on L1544.
基金supported by the Natural Science Foundation of Yunnan Province(No.202201 BC070003)supported by the ANID FONDECYT Postdoctoral program No.3220029+2 种基金support by ANID,—Millennium Science Initiative Program—NCN19_171sponsored(in part)by the Chinese Academy of Sciences(CAS)the CAS South America Center for Astronomy(CASSACA)in Santiago,Chile.
文摘Infrared(IR)spectral energy distribution(SED)is the major tracer of protoplanetary disks.It was recently proposed to use the near-to-mid IR(or K-24)SED slopeαdefined between 2 and 24μm as a potential quantitative tracer of disk age.We critically examine the viability of this idea and confront it with additional statistics of IR luminosities and SED shapes.We point out that,because the statistical properties of most of the complicated physical factors involved in disk evolution are still poorly understood in a quantitative sense,the only viable way is to assume them to be random so that an idealized“average disk”can be defined,which allows theαhistogram to trace its age.We confirm that the statistics of the zeroth order(luminosity),first order(slopeα),and second order characteristics(concavity)of the observed K-24 SEDs indeed carry useful information upon the evolutionary processes of the“average disk”.We also stress that intrinsic diversities in K-24 SED shapes and luminosities are always large at the level of individual stars so that the application of the evolutionary path of the“average disk”to individual stars must be done with care.The data of most curves in plots are provided on GitHub(Disk-age package https://github.com/starage/disk-age/).
文摘In this paper,we present a new gas-grain chemical code for interstellar clouds written in pure Python(GGCHEMPY(GGCHEMPY is available on https://github.com/JixingGE/GGCHEMPY)).By combining with the high-performance Python compiler Numba,GGCHEMPY is as efficient as the Fortran-based version.With the Python features,flexible computational workflows and extensions become possible.As a showcase,GGCHEMPY is applied to study the general effects of three-dimensional projection on molecular distributions using a two-core system which can be easily extended for more complex cases.By comparing the molecular distribution differences between two overlapping cores and two merging cores,we summarized the typical chemical differences such as N2 H+,HC3 N,C2 S,H2 CO,HCN and C2 H,which can be used to interpret 3 D structures in molecular clouds.
基金supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region (Grant No. 2022D01B221)he Xinjiang Tianchi Talent Program (2023)+4 种基金the NSRT operators for their assistance during the observationspartly supported by the OperationMaintenance and Upgrading Fund for Astronomical Telescopes and Facility Instrumentsbudgeted from the Ministry of Finance of China and administrated by the Chinese Academy of Sciencesthe Urumqi Nanshan Astronomy and Deep Space Exploration Observation and Research Station of Xinjiang (Grant No. XJYWZ2303)
文摘There have been several studies on sulfur depletion in dense cores like TMC-1(Taurus Molecular Cloud 1),employing updated reaction networks for sulfur species to explain the missing sulfur in the gas within dense clouds.Most of these studies used a C/O ratio of 0.7 or lower.We present NSRT(NanShan 26m Radio Telescope)observations of TMC-1 alongside results from time-dependent chemical simulations using an updated chemical network.Our findings highlight the impact of the C/O ratio on the gas-phase evolution of C2S and C3S.The simulation results show that the C/O ratio is an important parameter,playing a fundamental role in determining the gas-phase abundances of sulfur species in dense cores.
