Gas-Grain Modeling of Interstellar O2

Molecular oxygen(O2)is essential to human beings on the earth.Although elemental oxygen is rather abundant,O2 is rare in the interstellar medium.It was only detected in two galactic and one extra-galactic region.The inconsistency between observations and theoretical studies is a big challenge for astrochemical models.Here we report a two-phase modeling research of molecular oxygen,using the Nautilus gas-grain code.We apply the isothermal cold dense models in the interstellar medium with two typical sets of initial elemental abundances,as well as the warm-up models with various physical conditions.Under cold dense conditions,we nd that the timescales for gas-phase CO,O2 and H2O to reach peak values are dependent on the hydrogen density and are shortened when hydrogen density increases.In warm-up models,O2 abundances are in good agreement with observations at temperatures rising after 10^5 yr.In both isothermal and warm-up models,the steady-state O2 fractional abundance is independent of the hydrogen density,as long as the temperature is high enough(>30 K),at which O2 is prevented from signi cant depleting onto grain surface.In addition,low density is preferable for the formation of O2,whether molecular oxygen is under cold conditions or in warm regions.

Magnetic field and Faraday rotation from large-scale interstellar medium to plasma near the black-hole horizon

Magnetic fields appear to be ubiquitous in the astrophysical environments of our Universe,but are still poorly understood despite playing an important role in understanding different-scale celestial objects(e.g.,Earth,planets,stars,normal galaxies,active galactic nuclei,clusters etc.).We briefly review the results and progress in magnetic field estimation based on rotation measures from the large-scale interstellar medium,megaparsec-scale radio jets to the plasma near the black-hole horizon.We find that there is no evident correlation between electron density and magnetic field in warm ionized plasma,which suggests that the estimation of the magnetic field from the ratio of the rotation measure and dispersion measure correctly reflects the intrinsic field.The estimation of the magnetic field from the rotation measure is also discussed near the black hole horizon in M 87.The Square Kilometre Array will greatly improve the understanding of the magnetic field in our Universe,which will provide high-quality polarization imaging and extragalactic rotation measures in the near future.

The Polarization Potential as a Probe into Interstellar Matter

By simple arguments, it is shown how alkaline types of atoms can be seen in dense molecular clouds depending on the average temperature of such regions of the Universe. This paper predicts infrared lines of such atoms that could be seen in molecular clouds. The theory is developed in the first part and the predicted experimental results will follow. It results that the alkaline atoms modelized using the short-range polarization potential are found in quantum states n* > 2.

Recovering the pulse profiles and polarization position angles of some pulsars from interstellar scattering

Interstellar scattering causes broadening and distortion in the mean pulse profiles and polarization position angle （PPA） curves of pulsars, especially pulse profiles observed at lower frequencies. This paper implements a method to recover the pulse profiles and PPA curves of five pulsars which have obvious scattered pulse pro- files at lower frequency. It reports a simulation to show the scattering and descatter- ing of pulse profiles and PPA curves, and as a practical application the lower frequency profiles and PPA curves of PSR 1356-60, PSR 1831-03, PSR 1838＋04, PSR 1859＋03 and PSR 1946＋35 are obtained. It is found that the original pulse profiles and PPA curves can be recovered.

“Interstellar Express”:A Possible Successor to Voyagers

Voyagers,the first and the only mission sent by human beings beyond the end of the solar wind,might be out of service in just several years.In the cosmos beyond 2025,very likely no artificial detector will be flying at the outer brim of the solar system.The Interstellar Express,a mission proposed by CAS scientists,might come timely as a possible successor to fill in the gap.Unlike Voyagers,its detectors are expected to fly not only to the nose part of the heliosphere,but also the tail part and the altitude dimension.As planned in the shortterm stage of its three-step layout,the first two detectors will be launched by the end of 2025,if everything goes well.

Periodic interstellar scintillation variations of PSRs J0613-0200 and J0636+5128 associated with the Local Bubble shell

Annual variations of interstellar scintillation can be modelled to constrain parameters of the ionized interstellar medium.If a pulsar is in a binary system,then investigating the orbital parameters is possible through analysis of the orbital variation of scintillation.In observations carried out from 2011 to 2020 by the European Pulsar Timing Array radio telescopes,PSRs J0613-0200and J0636+5128 show strong annual variations in their scintillation velocity,while the former additionally exhibits an orbital fluctuation.Bayesian theory and Markov-chain-Monte-Carlo methods are used to interpret these periodic variations.We assume a thin and anisotropic scattering screen model,and discuss the mildly and extremely anisotropic scattering cases.PSR J0613-0200is best described by mildly anisotropic scattering,while PSR J0636+5128 exhibits extremely anisotropic scattering.We measure the distance,velocity,and degree of anisotropy of the scattering screen for our two pulsars,finding that scattering screen distances from Earth for PSRs J0613-0200 and J0636+5128 are 316_(-20)^(+28)pc and 262_(-38)^(+96)pc,respectively.The positions of these scattering screens are coincident with the shell of the Local Bubble towards both pulsars.These associations add to the growing evidence of the Local Bubble shell as a dominant region of scattering along many sightlines.

Scintillation optics of pulsar binaries and microstructure in the local ionized interstellar medium

Interstellar scintillation(ISS)caused by scattering from electron density microstructure(?1 AU)provides unequaled spatial resolving power for a number of applications in astronomy.These include studies of the interstellar medium on scales as small as 100 km and constraints on emission structure in the magnetospheres of compact objects on similar scales.

可撤销属性加密的区块链数据访问控制方法

针对区块链数据共享中存在的粗粒度访问控制问题,提出一种基于属性撤销密文策略属性基加密的区块链数据访问控制方法。在现有方案基础上进行改造,引入预解密过程,结合属性撤销列表实现属性实时撤销;基于非对称群下的DBDH困难问题假设进行安全性证明;基于超级账本Fabric进行系统设计,结合星际文件系统采用链上链下存储方式解决区块链容量不足和系统效率问题。实验结果表明,所提方案撤销属性时无需更新密钥密文重复上链,仅需要6次Pairing操作进行预解密和解密,且在大规模属性集下,预解密时间和解密时间平均保持在百毫秒左右的常量级上,实现区块链数据高效、细粒度的访问控制。

Cosmic Ray-driven Bioenergetics for Life in Molecular Clouds

According to models such as panspermia or the Nebula-Relay hypothesis,the ancestors of life on Earth once lived in molecular clouds.Then what are the energy source and bioenergetics for such lifeforms?A new bioenergetic mechanism powered by cosmic ray ionization of hydrogen molecules is proposed and its relation with the origin of chemiosmosis is also discussed in this paper.Based on this mechanism,the Last Universal Common Ancestor may be a type of lifeform that utilizes hydrogen molecules as donors of electron transport chains.

The Radcliffe Wave Parameters from Data on Open Star Clusters

A spectral analysis of the vertical positions and velocities of 374 open star clusters(OSCs)was carried out.We took these OSCs from the Hunt and Reffert catalog;they have an average age of about 10 million years,and are located on the galactic plane XY in a narrow zone inclined by 25°to the galactic axis Y.The following estimates of the parameters of the Radcliffe wave were obtained:(a)the maximum value in periodic perturbations of vertical coordinates Z_(max)=92±10pc with the wavelength of these perturbations λ_(z)=4.82±0.09 kpc;(b)the maximum value of the velocity of vertical disturbances Wmax=4.36±0.12km s^(-1) with disturbance wavelengthλ_(W)=1.78±0.02 kpc.Note that the results of the vertical velocity analysis are first-class in accuracy and completely new.

Observation of HⅠaround three Satellite Galaxies of M31 with FAST:AndromedaⅡ,NGC 205,and NGC 185

With the exceptional sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope,we conducted observations of the neutral hydrogen(HⅠ)in the circumgalactic medium of Andromeda’s(M31)satellite galaxies,specifically AndromedaⅡ,NGC 205,and NGC 185.Initially,three drift scans were executed for these satellites,with a detection limit of 4×10^(18)cm^(-2)(approximately 1.88×10^(3)M_Θof HⅠmass),followed by a more in-depth scan of a specific region.We discovered a C-shaped HⅠarc structure sharing a position and line-of-sight velocity similar to a stellar ring structure around AndromedaⅡ,hinting at a potential connection with AndromedaⅡ.In the context of NGC 205,we identified two mass concentrations in the northeast direction,which could be indicative of tidal streams resulting from the interaction between this galaxy and M31.These new lumps discovered could be very helpful in solving the missing interstellar medium problem for NGC 205.Observations regarding NGC 185are consistent with previous studies,and we did not detect any additional HⅠmaterial around this galaxy.These observational results enhance our understanding of the evolution of these satellite galaxies and provide insight into their historical interactions with the galaxy M31.

Summary of a Life in Observational Ultraviolet/Optical Astronomy

I reminisce on my early life in Section 1;on my education in Sections 2 and 3;on the years at Princeton as a research astronomer in Section 4;on the years on the faculty at Chicago in Section 5;on research on Diffuse Interstellar Bands(DIBs) in Section 6;on construction of the 3.5 m telescope at Apache Point Observatory(APO)in Section 7;on work on the Sloan Digital Sky Survey(SDSS) in Section 8;on work in public education in Chicago in Section 9;and on my travels in Section 10. My main science research is of an observational nature,concerning Galactic and intergalactic interstellar gas. Highlights for me included my work on the orbiting telescope Copernicus, including the discovery of interstellar deuterium;early observations of absorption associated with fivetimes ionized oxygen;and discoveries concerning the phases of gas in the local interstellar medium, based on previously unobservable interstellar UV spectral lines. With other instruments and collaborations, I extended interstellar UV studies to the intergalactic cool gas using quasi-stellar object QSO absorption lines redshifted to the optical part of the spectrum;provided a better definition of the emission and morphological character of the source of absorption lines in QSO spectra;and pursued the identification of the unidentified DIBs. For several of these topics, extensive collaborations with many scientists were essential over many years. The conclusions developed slowly, as I moved from being a graduate student at Chicago, to a research scientist position at Princeton and then to a faculty position at Chicago. At each stage of life, I was exposed to new technologies adaptable to my science and to subsequent projects. From high school days, I encountered several management opportunities which were formative. I have been extremely fortunate both in scientific mentors I had and in experimental opportunities I encountered.

Life Origin in the Milky Way Galaxy: I. The Stellar Nucleogenesis of Elements Necessary for the Life Origin

Chemical elements in space can be synthesized by stellar nuclear reactors. Studying the dynamics of processes occurring in the stars introduces a concept of the ensemble-averaged stellar reactor. For future interstellar missions, the terrestrial and solar abundances were compared with considerable number of stars allocated in the ~200 pc solar neighborhood. According to the value of the effective temperature, four stellar classes are distinguished, for which the correlation coefficients and standard deviation are calculated. The statement about the possibility of transferring heavy elements synthesized by stars over long distances in space has been completely refuted. There is no immutability of the distribution of elements on neighboring stars and in the Solar System. It is shown that chemical elements are mainly synthesized inside each stellar reactor. The theory of the buoyancy of elements is generalized to stars. It has been suggested that stars overheat due to a shift in the parameters of nuclear processes occurring inside stars, which leads to the synthesis of heavy elements.

Life Origin in the Milky Way Galaxy: II. Scanning for Habitable Stellar Systems on Behalf of Future Space Missions

The possibility of the life origin in the stellar systems, located at a distance of ~200 pc from the solar system, was investigated. The stars, in the spectrums of which C (carbon), O (oxygen), N (nitrogen), and P (phosphorus) are found, are called DNA-stars. Based on stellar abundances a new method for searching for habitable exoplanets has been developed and a list of 48 DNA-stars in the solar neighborhood, on which life is possible, has been defined. The quota of DNA-stars is equal 1.3% of the total amount of Hypatia Stellar Catalog. Only three DNA-stars out of selected 48 stars belong to the spectral class as our Sun (G2V). The closest to the solar system is the DNA-star with the number HIP 15510, which belongs to the G8V class and is 6 pc away from the solar system. Nine DNA-stars, which have the highest chemical similarity with solar spectrum, were identified. It is identified that one of these nine stars, HIP 24681, has six planets.

The Effect of a Monatomic Layer on a Surface on the Transition Radiation

The transition radiation of a charged particle crossing the interface of two media having a monatomic impurity layer is investigated. It is shown that at sliding angles of incidence of a particle on the boundary of the media, the transition radiation is mainly determined by the properties of the surface layer. The possibility of using transition radiation to study the surface of substances is discussed. In addition, due to the hard radiation present in space, this research may be important for the use of light monoatomic layers as a material for satellite antennas, “solar sails” and cover layers in a future space (interstellar) mission.

霍夫斯泰德文化维度理论下的中美差异探究——以《流浪地球2》和《星际穿越》为例

电影作为人类文化生活中重要的精神产物,必定会受到创作者世界观、人生观、价值观的影响,进而展现其背后的民族与文化差异。长期以来,科幻题材因情节独特、创作难度大、人文情怀丰富而备受关注。本文以霍夫斯泰德文化维度理论为理论框架,提取电影《流浪地球2》及《星际穿越》中的经典话语与文化现象,探究中美科幻电影中的文化差异及其深层原因,以期促进大众对不同文化的客观认识,并对文化电影的制作有所启发。

Geminga TeV晕周围星际介质的湍动特性

空间功率谱分析是研究星际介质湍动特性的常用方法。以此方法利用GALFA HI巡天数据分析Geminga附近一块中性氢云的湍动特性,其21 cm谱线积分亮温度图的空间功率谱符合幂律分布,谱指数为-4.0±0.1。与银河系内本地星际介质的功率谱(谱指数大于-3.0)相比,该云的功率谱较陡。分析陡谱的成因,排除了中性氢云在视线方向所取的速度宽度不足、云周围存在垂直于视线方向的有序磁场、能量传递过程中有损失等因素的影响。这个结果暗示Geminga周围可能存在一个区域,其内部湍动特性与银河系其他区域的湍动特性不同,进而导致了Geminga TeV晕中较低的扩散系数。

早期阶段大质量团块中的HCN、HNC、HCO^(+)和CN化学性质研究

选择67个相对孤立的大质量恒星形成团块,使用4种分子谱线(HCN(1-0)、HNC(1-0)、HCO^(+)(1-0)和CN(1-0),括号中的1-0代表分子从转动能级1跃迁到转动能级0)和红外波段数据,研究它们的整体化学性质.通过对源的积分强度、柱密度、分子丰度和丰度比在不同演化阶段的统计,发现大质量恒星形成团块CN(1-0)、HCO^(+)(1-0)、HCN(1-0)和HNC(1-0)的积分强度和柱密度中值随着演化阶段的增加都呈现增加趋势,这与理论预期相符.然而单一分子进行的柱密度和丰度统计结果存在较大的误差,用以示踪的演化阶段有很大的局限性.I(CN)/I(HNC)、I(CN)/I(HCN)和I(HCN)/I(HCO^(+))的积分强度比随演化阶段递增(I代表分子的积分强度),是潜在的用来示踪大质量恒星形成团块演化的探针;N(CN)/N(H2)、N(HNC)/N(H2)和N(HCN)/N(HCO^(+))的中值随演化阶段单调递增(N代表分子的柱密度),有希望作为示踪大质量恒星演化的化学探针.需要注意的是由于研究工作观测数据的限制,不能获得各分子的光学厚度,受光学厚度影响得不到可靠的柱密度,从而得不到可靠的丰度,最终影响对丰度比化学时钟的检验.

电离氢区S187的大尺度CO多谱线观测

大质量恒星强烈的反馈深刻影响其周围的星际介质,并可能触发下一代恒星形成.S187是位于银河系第2象限的大质量恒星形成区,呈现出“扫集-坍缩”的触发式恒星形成模式.基于“银河画卷”巡天^(12)CO/^(13)CO/C^(18)O(J=1-0,下文J=1-0为简便起见省略)谱线数据,对S187区域分子云的基本性质开展了研究,探索了该区域大质量恒星对分子云的反馈.利用GaussPy+和聚类算法,在该区域证认了32个分子云,并结合Gaia(Global Astrometric Interferometer for Astrophysics)卫星恒星消光数据测量得到其中8个分子云的距离.S187区域由^(13)CO和C^(18)O示踪的相对致密的气体含量相比于银道面第2象限大部分区域的分子云高出1–2个量级.S187区域分子云中证认了243个^(13)CO团块和98个C^(18)O团块,其中有7个^(13)CO团块和5个C^(18)O团块有形成大质量恒星的潜力.研究结果显示,大质量恒星的反馈对其周围分子云的聚集作用明显,为下一代大质量恒星的形成提供了条件.

不确定性下的低轨卫星激光星间链路误差模型修正方法

在工程应用中,激光链路构建过程不可避免地会受到各种不确定性的影响,导致激光建链在扫描过程中对指向区域估计不准,降低星间激光建链的准确性.因此,应多方面考虑不确定因素来修正低轨激光星间链路的动力学指向误差模型,为后期的扫描捕获提供基础.提出一种考虑不确定性因素的低轨卫星激光星间链路动力学指向误差模型修正方法,激光星间链路系统以及不确定参数进行描述,建立系统动力学模型;对不确定参数进行了灵敏度分析,并基于灵敏度指标,使用Kriging方法建立了原有系统动力学的代理模型,并验证模型预测精度;确定不确定性量化指标,使用贝叶斯随机模型修正技术对系统动力学模型不确定参数进行修正;通过数值仿真验证了不确定性下的星间链路指向误差动力学模型修正方法的有效性和可行性.