We report our new results on Herbig-Haro (HH) objects in the star forming region of Taurus from a wide-field survey with the 60/90 cm Schmidt telescope of the Beijing Astronomical Observatory. This survey using CCD im...We report our new results on Herbig-Haro (HH) objects in the star forming region of Taurus from a wide-field survey with the 60/90 cm Schmidt telescope of the Beijing Astronomical Observatory. This survey using CCD imaging with a narrow band [SII] filter and an intermediate band [BATC10] filter covered approximately 30 square degrees in Taurus. Besides confirming the known HH Objects in the region, we discovered seven new HH candidates, and groups. Six of these are HH 701A-B, HH 702A-D, HH 703, HH 704A-D, HH 705, HH 706 and the seventh is a group, a new component of HH 319, labeled HH 319B-D. Based on the large-scale distribution of pre-main-sequence (PMS) stars in Taurus, we analyze statistically the most probable distance from the HH objects to each PMS star, from which we estimate the typical timescale of these HH objects to be between (1.3?2.0)×10<SUP>4</SUP> yrs; and we also obtain the birth rates of HH objects: 0.447±0.198 for Class I PMS stars, 0.360±0.222 for Class II PMS stars, and ?0.148±0.234 for Class III PMS stars.展开更多
We make a statistical study of the energy sources of high-velocity phenomena, Herbig-Haro (HH) objects. IRAS counterparts of HH objects are identified. Their colors, brightness, geometric relation to the RH objects an...We make a statistical study of the energy sources of high-velocity phenomena, Herbig-Haro (HH) objects. IRAS counterparts of HH objects are identified. Their colors, brightness, geometric relation to the RH objects and SED are analysed. The sources are found to be concentrated in a band-shaped region in the IRAS color-color diagram. We suggest an explanation of thick surrounding material for this distribution. We propose a new method for identifying the energy sources based on color arid brightness. This method is applied to more than 200 HR objects whose energy sources are still unknown. Finally, a group of very young stellar object candidates which have similar properties to the RH energy sources is picked out. Their large-scale distribution is discussed.展开更多
ISO 27001给出了信息安全管理体系要求方面的最佳实践标准,但并没有说明体系要求方面内在的逻辑关系。该文将ISO 27001分解为过程方法要求和安全控制要求2个部分,在过程方法上按照PDCA的循环模型重新解构了过程方法要求之间的关系,在安...ISO 27001给出了信息安全管理体系要求方面的最佳实践标准,但并没有说明体系要求方面内在的逻辑关系。该文将ISO 27001分解为过程方法要求和安全控制要求2个部分,在过程方法上按照PDCA的循环模型重新解构了过程方法要求之间的关系,在安全控制上按照主体访问客体的方式重组了安全控制要求之间的关系。展开更多
The observation of oxygen(O)-and nitrogen(N)-bearing molecules gives an idea about the complex prebiotic chemistry in the interstellar medium.Recent millimeter and submillimeter wavelength observations have shown the ...The observation of oxygen(O)-and nitrogen(N)-bearing molecules gives an idea about the complex prebiotic chemistry in the interstellar medium.Recent millimeter and submillimeter wavelength observations have shown the presence of complex O-and N-bearing molecules in the star formation regions.So,the investigation of those molecules is crucial to understanding the chemical complexity in the star-forming regions.In this article,we present the identification of the rotational emission lines of N-bearing molecules ethyl cyanide(C_(2)H_(5)CN)and cyanoacetylene(HC_(3)N),and O-bearing molecule methyl formate(CH_(3)OCHO)toward high-mass protostar IRAS18089–1732 using the Atacama Compact Array.We also detected the emission lines of both the N-and O-bearing molecule formamide(NH_(2)CHO)in the envelope of IRAS 18089–1732.We have detected the v=0 and 1 state rotational emission lines of CH_(3)OCHO.We also detected the two vibrationally excited states of HC_(3)N(v7=1 and v7=2).The estimated fractional abundances of C_(2)H_(5)CN,HC_(3)N(v7=1),HC_(3)N(v7=2),and NH_(2)CHO toward IRAS 18089–1732 are(1.40±0.5)×10^(-10),(7.5±0.7)×10^(-11),(3.1±0.4)×10^(-11),and(6.25±0.82)×10^(-11)respectively.Similarly,the estimated fractional abundances of CH_(3)OCHO(v=0)and CH_(3)OCHO(v=1)are(1.90±0.9)×10^(-9)and(8.90±0.8)×10^(-10),respectively.We also created the integrated emission maps of the detected molecules,and the observed molecules may have originated from the extended envelope of the protostar.We show that C_(2)H_(5)CNand HC_(3)N are most probably formed via the subsequential hydrogenation of the CH_(2)CHCNand the reaction between C_(2)H_(2)and CN on the grain surface of IRAS 18089–1732.We found that NH_(2)CHO is probably produced due to the reaction between NH_(2)and H_(2)CO in the gas phase.Similarly,CH_(3)OCHO is possibly created via the reaction between radical CH_(3)O and radical HCO on the grain surface of IRAS 18089–1732.展开更多
In star formation regions,the complex organic molecules(COMs)that contain peptide bonds(-NH-C(=O)-)play a major role in the metabolic process because-NH-C(=O)-is connected to amino acids(R-CHNH_2-COOH).Over the past f...In star formation regions,the complex organic molecules(COMs)that contain peptide bonds(-NH-C(=O)-)play a major role in the metabolic process because-NH-C(=O)-is connected to amino acids(R-CHNH_2-COOH).Over the past few decades,many COMs containing peptide-like bonds have been detected in hot molecular cores(HMCs),hot corinos,and cold molecular clouds,however,their prebiotic chemistry is poorly understood.We present the first detection of the rotational emission lines of formamide(NH_2CHO)and isocyanic acid(HNCO),which contain peptide-like bonds toward the chemically rich HMC G358.93-0.03 MM1,using high-resolution and high-sensitivity Atacama Large Millimeter/submillimeter Array bands 6 and 7.We estimate that the column densities of NH_2CHO and HNCO toward G358.93-0.03 MM1 are(2.80±0.29)×10~(15)cm~(-2)and(1.80±0.42)×10~(16)cm~(-2)with excitation temperatures of 165±21 K and 170±32 K,respectively.The fractional abundances of NH_2CHO and HNCO toward G358.93-0.03 MM1 are(9.03±1.44)×10~(-10)and(5.80±2.09)×10^(-9).We compare the estimated abundances of NH_2CHO and HNCO with the existing threephase warm-up chemical model abundance values and notice that the observed and modeled abundances are very close.We conclude that NH_2CHO is produced by the reaction of NH_2and H_2CO in the gas phase toward G358.93-0.03 MM1.Likewise,HNCO is produced on the surface of grains by the reaction of NH and CO toward G358.93-0.03 MM1.We also find that NH_2CHO and HNCO are chemically linked toward G358.93-0.03 MM1.展开更多
Previous observations have revealed an accretion disk and outflow motion in the high-mass starforming region G192.16–3.84, but collapse has not been reported before. Here we present molecular line and continuum obser...Previous observations have revealed an accretion disk and outflow motion in the high-mass starforming region G192.16–3.84, but collapse has not been reported before. Here we present molecular line and continuum observations toward the massive core G192.16–3.84 with the Submillimeter Array. C18 O(2–1) and HCO+(3–2) lines show pronounced blue profiles, indicating gas infalling in this region. This is the first time that infall motion has been reported in the G192.16–3.84 core. Two-layer model fitting gives infall velocities of 2.0±0.2 and 2.8±0.1 km s-1. Assuming that the cloud core follows a power-law density profile(ρ∝ r1.5), the corresponding mass infall rates are(4.7±1.7)×10-3 and(6.6±2.1)×10-3 M⊙yr-1 for C18 O(2–1) and HCO+(3–2), respectively. The derived infall rates are in agreement with the turbulent core model and those in other high-mass star-forming regions, suggesting that high accretion rate is a general requirement for forming a massive star.展开更多
We have conducted a large-field simultaneous survey of 12 CO,13 CO and C18O J=1-0 emission toward the Orion A giant molecular cloud(GMC)with a sky coverage of4.4 deg2 using the Purple Mountain Observatory(PMO)-13.7 m ...We have conducted a large-field simultaneous survey of 12 CO,13 CO and C18O J=1-0 emission toward the Orion A giant molecular cloud(GMC)with a sky coverage of4.4 deg2 using the Purple Mountain Observatory(PMO)-13.7 m millimeter-wavelength telescope.We use the probability distribution function of the column density(N-PDF)to investigate the distribution of molecular hydrogen in the Orion A GMC.The H2 column density,derived from the 13CO emission,of the GMC is dominated by a log-normal distribution in the range from4×1021 to1.5×1023 cm-2 with excesses both at the low-density and high-density ends.The excess of the low-density end is possibly caused by an extended and low-temperature(10 K)component with velocities in the range of 5-8 km s-1.Compared with the northern sub-regions,the southern sub-regions of the Orion A GMC contain less gas with column density in NH2>1.25×1022 cm-2.The dispersions of the N-PDFs of the sub-regions are found to correlate with the evolutionary stages of the clouds across the Orion A GMC.The structure hierarchy of Orion A GMC is explored with the DENDROGRAM algorithm,and it is found that the GMC is composed of two branches.All structures except one in the tree have virial parameters less than 2,indicating self-gravity is important on the spatial scales from0.3 to4 pc.Although power-laws and departures from lognormal distributions are found at the high-density end of N-PDFs for active star-forming regions,the N-PDFs of structures in the Orion A GMC are predominantly lognormal on scales from R0.4 to 4 pc.展开更多
We have carried out CO J=2 - 1 and CO J = 3 - 2 observations toward Tycho＇s supernova remnant （SNR） using the KOSMA 3m-telescope. From these observations, we identified three molecular clouds （MCs） around the SNR...We have carried out CO J=2 - 1 and CO J = 3 - 2 observations toward Tycho＇s supernova remnant （SNR） using the KOSMA 3m-telescope. From these observations, we identified three molecular clouds （MCs） around the SNR. The small cloud in the southwest was discovered for the first time. In the north and east, two MCs （Cloud A and Cloud B） adjacent in space display a bow-shaped morphology, and have broad emission lines, which provide some direct evidences of the SNR-MCs interaction. The MCs are revealed at-69∽-59 km s-1, coincident with Tycho＇s SNR. The MCs associated with Tycho＇s SNR have a mass of-2.13 x 10^3 Mo. Position- velocity diagrams show the two clouds to be adjacent in velocity, which means cloud- cloud collision could occur in this region. The maximum value （0.66±0.10） of the integrated CO line intensity ratio （IcoJ=3-2/Icoj=2-1） for the three MCs agrees well with the previous measurement of individual Galactic MCs, implying that the SNR shock drove into the MCs. The two MCs have a line intensity ratio gradient. The distribution of the ratio appears to indicate that the shock propagates from the southwest to the northeast.展开更多
Abstract G349.7＋0.2 is an interacting supernova remnant （SNR） expanding in a dense medium. Recently, a very strong γ-ray source coincident with this SNR has been revealed by Fermi-LAT and H.E.S.S. ob- servations w...Abstract G349.7＋0.2 is an interacting supernova remnant （SNR） expanding in a dense medium. Recently, a very strong γ-ray source coincident with this SNR has been revealed by Fermi-LAT and H.E.S.S. ob- servations which shows a broken power-law-like spectrum. An escaping-diffusion model, including the power-law and g-function injection, is applied to this source which can naturally explain the spectral fea- ture in both the GeV and TeV regime. We use the Markov Chain Monte Carlo method to constrain the model parameters and find that the correction factor of slow diffusion around this SNR, X-0.01 for power-law injection and X - 0.1 for g-function injection, can fit the data best with reasonable molecular cloud mass. This slow diffusion is also consistent with previous results from both phenomenological models and theoretical predication.展开更多
基金Supported by the National Natural Science Foundation of China
文摘We report our new results on Herbig-Haro (HH) objects in the star forming region of Taurus from a wide-field survey with the 60/90 cm Schmidt telescope of the Beijing Astronomical Observatory. This survey using CCD imaging with a narrow band [SII] filter and an intermediate band [BATC10] filter covered approximately 30 square degrees in Taurus. Besides confirming the known HH Objects in the region, we discovered seven new HH candidates, and groups. Six of these are HH 701A-B, HH 702A-D, HH 703, HH 704A-D, HH 705, HH 706 and the seventh is a group, a new component of HH 319, labeled HH 319B-D. Based on the large-scale distribution of pre-main-sequence (PMS) stars in Taurus, we analyze statistically the most probable distance from the HH objects to each PMS star, from which we estimate the typical timescale of these HH objects to be between (1.3?2.0)×10<SUP>4</SUP> yrs; and we also obtain the birth rates of HH objects: 0.447±0.198 for Class I PMS stars, 0.360±0.222 for Class II PMS stars, and ?0.148±0.234 for Class III PMS stars.
文摘We make a statistical study of the energy sources of high-velocity phenomena, Herbig-Haro (HH) objects. IRAS counterparts of HH objects are identified. Their colors, brightness, geometric relation to the RH objects and SED are analysed. The sources are found to be concentrated in a band-shaped region in the IRAS color-color diagram. We suggest an explanation of thick surrounding material for this distribution. We propose a new method for identifying the energy sources based on color arid brightness. This method is applied to more than 200 HR objects whose energy sources are still unknown. Finally, a group of very young stellar object candidates which have similar properties to the RH energy sources is picked out. Their large-scale distribution is discussed.
基金the Swami Vivekananda Merit-cum-Means Scholarship(SVMCM)for financial support for this research。
文摘The observation of oxygen(O)-and nitrogen(N)-bearing molecules gives an idea about the complex prebiotic chemistry in the interstellar medium.Recent millimeter and submillimeter wavelength observations have shown the presence of complex O-and N-bearing molecules in the star formation regions.So,the investigation of those molecules is crucial to understanding the chemical complexity in the star-forming regions.In this article,we present the identification of the rotational emission lines of N-bearing molecules ethyl cyanide(C_(2)H_(5)CN)and cyanoacetylene(HC_(3)N),and O-bearing molecule methyl formate(CH_(3)OCHO)toward high-mass protostar IRAS18089–1732 using the Atacama Compact Array.We also detected the emission lines of both the N-and O-bearing molecule formamide(NH_(2)CHO)in the envelope of IRAS 18089–1732.We have detected the v=0 and 1 state rotational emission lines of CH_(3)OCHO.We also detected the two vibrationally excited states of HC_(3)N(v7=1 and v7=2).The estimated fractional abundances of C_(2)H_(5)CN,HC_(3)N(v7=1),HC_(3)N(v7=2),and NH_(2)CHO toward IRAS 18089–1732 are(1.40±0.5)×10^(-10),(7.5±0.7)×10^(-11),(3.1±0.4)×10^(-11),and(6.25±0.82)×10^(-11)respectively.Similarly,the estimated fractional abundances of CH_(3)OCHO(v=0)and CH_(3)OCHO(v=1)are(1.90±0.9)×10^(-9)and(8.90±0.8)×10^(-10),respectively.We also created the integrated emission maps of the detected molecules,and the observed molecules may have originated from the extended envelope of the protostar.We show that C_(2)H_(5)CNand HC_(3)N are most probably formed via the subsequential hydrogenation of the CH_(2)CHCNand the reaction between C_(2)H_(2)and CN on the grain surface of IRAS 18089–1732.We found that NH_(2)CHO is probably produced due to the reaction between NH_(2)and H_(2)CO in the gas phase.Similarly,CH_(3)OCHO is possibly created via the reaction between radical CH_(3)O and radical HCO on the grain surface of IRAS 18089–1732.
文摘In star formation regions,the complex organic molecules(COMs)that contain peptide bonds(-NH-C(=O)-)play a major role in the metabolic process because-NH-C(=O)-is connected to amino acids(R-CHNH_2-COOH).Over the past few decades,many COMs containing peptide-like bonds have been detected in hot molecular cores(HMCs),hot corinos,and cold molecular clouds,however,their prebiotic chemistry is poorly understood.We present the first detection of the rotational emission lines of formamide(NH_2CHO)and isocyanic acid(HNCO),which contain peptide-like bonds toward the chemically rich HMC G358.93-0.03 MM1,using high-resolution and high-sensitivity Atacama Large Millimeter/submillimeter Array bands 6 and 7.We estimate that the column densities of NH_2CHO and HNCO toward G358.93-0.03 MM1 are(2.80±0.29)×10~(15)cm~(-2)and(1.80±0.42)×10~(16)cm~(-2)with excitation temperatures of 165±21 K and 170±32 K,respectively.The fractional abundances of NH_2CHO and HNCO toward G358.93-0.03 MM1 are(9.03±1.44)×10~(-10)and(5.80±2.09)×10^(-9).We compare the estimated abundances of NH_2CHO and HNCO with the existing threephase warm-up chemical model abundance values and notice that the observed and modeled abundances are very close.We conclude that NH_2CHO is produced by the reaction of NH_2and H_2CO in the gas phase toward G358.93-0.03 MM1.Likewise,HNCO is produced on the surface of grains by the reaction of NH and CO toward G358.93-0.03 MM1.We also find that NH_2CHO and HNCO are chemically linked toward G358.93-0.03 MM1.
基金supportedby the National Key R&D Program of China (No.2017YFA0402701)by the National Natural Science Foundation of China (Grant Nos. 11373026 and11433004)+2 种基金the Joint Research Fund in Astronomy(U1631237) under cooperative agreement between the National Natural Science Foundation of China and Chinese Academy of Sciencesby the Top TalentsProgram of Yunnan Province (2015HA030)by Yunnan University’s Research Innovation Fund for Graduate Students
文摘Previous observations have revealed an accretion disk and outflow motion in the high-mass starforming region G192.16–3.84, but collapse has not been reported before. Here we present molecular line and continuum observations toward the massive core G192.16–3.84 with the Submillimeter Array. C18 O(2–1) and HCO+(3–2) lines show pronounced blue profiles, indicating gas infalling in this region. This is the first time that infall motion has been reported in the G192.16–3.84 core. Two-layer model fitting gives infall velocities of 2.0±0.2 and 2.8±0.1 km s-1. Assuming that the cloud core follows a power-law density profile(ρ∝ r1.5), the corresponding mass infall rates are(4.7±1.7)×10-3 and(6.6±2.1)×10-3 M⊙yr-1 for C18 O(2–1) and HCO+(3–2), respectively. The derived infall rates are in agreement with the turbulent core model and those in other high-mass star-forming regions, suggesting that high accretion rate is a general requirement for forming a massive star.
基金supported by National Key R&D Program of China(2017YFA0402701)Key Research Program of Frontier Sciences of CAS(QYZDJSSW-SLH047)supports by the National Natural Science Foundation of China(Grant Nos.11503086 and 11503087)。
文摘We have conducted a large-field simultaneous survey of 12 CO,13 CO and C18O J=1-0 emission toward the Orion A giant molecular cloud(GMC)with a sky coverage of4.4 deg2 using the Purple Mountain Observatory(PMO)-13.7 m millimeter-wavelength telescope.We use the probability distribution function of the column density(N-PDF)to investigate the distribution of molecular hydrogen in the Orion A GMC.The H2 column density,derived from the 13CO emission,of the GMC is dominated by a log-normal distribution in the range from4×1021 to1.5×1023 cm-2 with excesses both at the low-density and high-density ends.The excess of the low-density end is possibly caused by an extended and low-temperature(10 K)component with velocities in the range of 5-8 km s-1.Compared with the northern sub-regions,the southern sub-regions of the Orion A GMC contain less gas with column density in NH2>1.25×1022 cm-2.The dispersions of the N-PDFs of the sub-regions are found to correlate with the evolutionary stages of the clouds across the Orion A GMC.The structure hierarchy of Orion A GMC is explored with the DENDROGRAM algorithm,and it is found that the GMC is composed of two branches.All structures except one in the tree have virial parameters less than 2,indicating self-gravity is important on the spatial scales from0.3 to4 pc.Although power-laws and departures from lognormal distributions are found at the high-density end of N-PDFs for active star-forming regions,the N-PDFs of structures in the Orion A GMC are predominantly lognormal on scales from R0.4 to 4 pc.
基金supported by the National Natural Science Foundation of China(Grant No. 10473014)
文摘We have carried out CO J=2 - 1 and CO J = 3 - 2 observations toward Tycho＇s supernova remnant （SNR） using the KOSMA 3m-telescope. From these observations, we identified three molecular clouds （MCs） around the SNR. The small cloud in the southwest was discovered for the first time. In the north and east, two MCs （Cloud A and Cloud B） adjacent in space display a bow-shaped morphology, and have broad emission lines, which provide some direct evidences of the SNR-MCs interaction. The MCs are revealed at-69∽-59 km s-1, coincident with Tycho＇s SNR. The MCs associated with Tycho＇s SNR have a mass of-2.13 x 10^3 Mo. Position- velocity diagrams show the two clouds to be adjacent in velocity, which means cloud- cloud collision could occur in this region. The maximum value （0.66±0.10） of the integrated CO line intensity ratio （IcoJ=3-2/Icoj=2-1） for the three MCs agrees well with the previous measurement of individual Galactic MCs, implying that the SNR shock drove into the MCs. The two MCs have a line intensity ratio gradient. The distribution of the ratio appears to indicate that the shock propagates from the southwest to the northeast.
基金the support of the National Natural Science Foundation of China(Grant No.11233001)973 Program(Grant 2015CB857100)+1 种基金he Educational Ministry of China(Grant 20120091110048)the program B for Outstanding PhD candidate of Nanjing University
文摘Abstract G349.7＋0.2 is an interacting supernova remnant （SNR） expanding in a dense medium. Recently, a very strong γ-ray source coincident with this SNR has been revealed by Fermi-LAT and H.E.S.S. ob- servations which shows a broken power-law-like spectrum. An escaping-diffusion model, including the power-law and g-function injection, is applied to this source which can naturally explain the spectral fea- ture in both the GeV and TeV regime. We use the Markov Chain Monte Carlo method to constrain the model parameters and find that the correction factor of slow diffusion around this SNR, X-0.01 for power-law injection and X - 0.1 for g-function injection, can fit the data best with reasonable molecular cloud mass. This slow diffusion is also consistent with previous results from both phenomenological models and theoretical predication.
