HCN分子是恒星与行星形成区中元素氮化学演化的重要示踪物，这主要是因为N原子和N₂分子难以在射电与红外波段被观测到。相应地，气相HCN可在恒星形成的多个阶段被观测到，包括年轻恒星周围的原行星盘、彗星彗发以及行星卫星的大气。尽管气相HCN的观测范围十分广泛，但星际HCN冰的身份确认工作仍处于空白状态。本研究利用新搭建的超高真空低温装置开展了一系列红外光谱测量，旨在为星际HCN冰的搜寻工作提供支持。研究获取了温度为10 K时，嵌入H₂O、H₂O:NH₃、CO、CO₂和CH₃OH冰中的HCN分子的一系列高分辨率实验室红外光谱。这些星际冰类似物用于模拟星际颗粒表面冰幔主要成分构成的HCN分子所处环境。此外，研究还获取了嵌入固态C₆H₆、C₅H₅N和C₆H₅NH₂中的HCN分子的光谱，以模拟HCN分子与富含多环芳烃的颗粒碳质物质的相互作用。研究将所得的实验室光谱数据，与ICEAge团队利用詹姆斯·韦伯空间望远镜（James Webb Space Telescope，JWST）的NIRSpec仪器对静息分子云开展观测的公开结果进行了对比。
英文摘要：
HCN molecules serve as an important tracer for chemical evolution of elemental nitrogen in the regions of star and planet formation. This is largely explained by the fact that N atoms and N$_2$ molecules are poorly accessible for the observation in the radio and infrared ranges. In turn, gas-phase HCN can be observed at various stages of star formation including disks arounds young stars, cometary comas and atmospheres of the planetary satellites. Despite the large geography of gas-phase observations, an identification of interstellar HCN ice is still lacking. In this work we present a series of infrared spectroscopic measurements performed at the new ultra-high vacuum cryogenic apparatus aiming to facilitate the search for interstellar HCN ice. A series of high resolution laboratory infrared spectra of HCN molecules embedded in the H$_2$O, H$_2$O:NH$_3$, CO, CO$_2$ and CH$_3$OH ices at 10~K temperature is obtained. These interstellar ice analogues aim to simulate the surroundings of HCN molecules by the main constituents of the icy mantles on the surface of the interstellar grains. In addition, the spectra of HCN molecules embedded in the solid C$_6$H$_6$, C$_5$H$_5$N and C$_6$H$_5$NH$_2$ are obtained to somehow simulate the interaction of HCN molecules with carbonaceous material of the grains rich in polycyclic aromatic hydrocarbons. The acquired laboratory spectroscopic data are compared with the publicly available results of NIRSpec James Webb Space Telescope observations towards quiescent molecular clouds performed by the ICEAge team.
Ice chemistry that can be unveiled with the JWST: SynthIceSpec, a synthetic spectrum generator to test spectral limits. Solid CO_2 as a dust thermometer and solid CH_3CN detectability in cold cores
Laboratoire d’Astrophysique de Bordeaux (LAB), Univ. Bordeaux, CNRS（波尔多大学天体物理实验室）；Centro de Astrobiología (CAB), CSIC-INTA（天体生物学中心）；Physique des Interactions Ioniques et Moléculaires, CNRS, Aix Marseille Univ.（离子与分子相互作用物理研究所）；Institut des sciences Moléculaires d’Orsay, CNRS, Université Paris-Saclay（奥赛分子科学研究所）；Institute for Astronomy（天文研究所）；CEA-CESTA（法国原子能及替代能源委员会塞斯塔研究中心）；CELIA, University of Bordeaux-CNRS-CEA（波尔多的激光化学和光化学实验室）
Chemical models and experiments indicate that interstellar dust grains and their ice mantles play an important role in the production of complex organic molecules (COMs). To date, the most complex solid-phase molecule detected with certainty in the ISM is methanol, but the James Webb Space Telescope (JWST) may be able to identify still larger organic species. In this study, we use a coupled chemo-dynamical model to predict new candidate species for JWST detection toward the young star-forming core Cha-MMS1, combining the gas-grain chemical kinetic code MAGICKAL with a 1-D radiative hydrodynami…
The UV radiation field is a critical regulator of gas-phase chemistry in surface layers of disks around young stars. In an effort to understand the relationship between photocatalyzing UV radiation fields and gas emission observed at infrared and sub-mm wavelengths, we present an analysis of new and archival HST, Spitzer, ALMA, IRAM, and SMA data for five targets in the Lupus cloud complex and 14 systems in Taurus-Auriga. The HST spectra were used to measure LyA and FUV continuum fluxes reaching the disk surface, which are responsible for dissociating relevant molecular species (e.g. HCN, N2).…
JWST/MIRI Hydrocarbon and Water Absorption in the Wind of a Young Disk: Signatures of Pebble Drift and Carbon Grain Sublimation
University of Michigan（密歇根大学）；University of Wisconsin-Madison（威斯康星大学麦迪逊分校）；California Institute of Technology（加州理工学院）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；University of Hawai`i at Mānoa（夏威夷大学马诺阿分校）；University of Maryland, College Park（马里兰大学帕克分校）；NSFs NOIRLab（美国国家科学基金会NOIR天文台实验室）；Vassar College（瓦萨学院）；University of Exeter（埃克塞特大学）；University of Arizona（亚利桑那大学）；CNRS（法国国家科学研究中心）；Institut d’Astrophysique Spatiale（空间天体物理研究所）；University of Copenhagen（哥本哈根大学）；Peking University（北京大学）；University College London（伦敦大学学院）
HCN is a molecule central to interstellar chemistry, since it is the simplest molecule containing a carbon-nitrogen bond and its solid state chemistry is rich. The aim of this work was to study the NH3 + HCN -> NH4+CN- thermal reaction in interstellar ice analogues. Laboratory experiments based on Fourier transform infrared spectroscopy and mass spectrometry were performed to characterise the NH4+CN- reaction product and its formation kinetics. This reaction is purely thermal and can occur at low temperatures in interstellar ices without requiring non-thermal processing by photons, electrons o…
We present results from the James Webb Space Telescope (JWST) Director's Discretionary Time Early Release Science (ERS) program 1328 targeting the nearby, Luminous Infrared Galaxy (LIRG), VV 114. We use the MIRI and NIRSpec instruments to obtain integral-field spectroscopy of the heavily obscured Eastern nucleus (V114E) and surrounding regions. The spatially resolved, high-resolution, spectra reveal the physical conditions in the gas and dust over a projected area of 2-3 kpc that includes the two brightest IR sources, the NE and SW cores. Our observations show for the first time spectroscopic …
First Observation of CO$_2$ Emission and foreground absorption Toward the Galactic Center with JWST
University of California, Los Angeles（加州大学洛杉矶分校）；Observatoire de Paris（巴黎天文台）；PSL Research University（PSL研究大学）；CNRS（法国国家科学研究中心）；Sorbonne Université（索邦大学）；Université Paris Cité（巴黎西岱大学）；Texas State University（德克萨斯州立大学）
Mid-infrared JWST spectra of carbon stars in the Large Magellanic Cloud
Space Telescope Science Institute（太空望远镜科学研究所）；University of North Carolina, Chapel Hill（北卡罗来纳大学教堂山分校）；Uppsala University（乌普萨拉大学）；University of Vienna（维也纳大学）；Boston College（波士顿学院）；The University of Western Ontario（韦仕敦大学）；Chalmers University of Technology（查尔姆斯理工大学）；Université Côte d’Azur（蔚蓝海岸大学）
Over the last few years, the chemistry of molecules other than CO in the planet-forming zones of disks is starting to be explored with Spitzer and high-resolution ground-based data. However, these studies have focused only on a few simple molecules. The aim of this study is to put observational constraints on the presence of more complex organic and sulfur-bearing molecules predicted to be abundant in chemical models of disks and to simulate high resolution spectra in view of future missions. High S/N Spitzer spectra at 10-30 micron of the near edge-on disks IRS46 and GVTau are used to search …
Current gas phase models do not account for the abundances of HNCO isomers detected in various environments, suggesting a formation in icy grain mantles. We attempted to study a formation channel of HNCO and its possible isomers by vacuum-UV photoprocessing of interstellar ice analogues containing H$_2$O, NH$_3$, CO, HCN, CH$_3$OH, CH$_4$, and N$_2$ followed by warm-up, under astrophysically relevant conditions. Only the H$_2$O:NH$_3$:CO and H$_2$O:HCN ice mixtures led to the production of HNCO species. The possible isomerization of HNCO to its higher energy tautomers following irradiation or …
Almost 20% of the ~ 200 different species detected in the interstellar and circumstellar media present a carbon atom linked to nitrogen by a triple bond. Among these 37 molecules, 30 are nitrile R-CN compounds, the remaining seven belonging to the isonitrile R-NC family. How these species behave in presence of the grain surfaces is still an open question. In this contribution we investigate whether the difference between nitrile and isonitrile functional groups may induce differences in the adsorption energies of the related isomers at the surfaces of interstellar grains of different nature an…
From Young to Older Disks: JWST/MIRI Evidence for Fading Molecular Emission and Hints for Elevated C/O in Upper Scorpius
The University of Arizona（亚利桑那大学）；Peking University（北京大学）；NASA Ames Research Center（NASA艾姆斯研究中心）；SETI Institute（SETI研究所）；Texas State University（德克萨斯州立大学）；University of Leeds（利兹大学）；California Institute of Technology（加州理工学院）；Joint ALMA Observatory（ALMA联合天文台）；Chinese Academy of Sciences（中国科学院）
A first taste of MEAD (Measuring Extinction and Abundances of Dust) -- I. Diffuse Milky Way interstellar dust extinction features in JWST infrared spectra
Formamide (NH$_2$CHO), a potential prebiotic precursor, has been proposed to play an important role in the context of origin of life on our planet. It has been observed in different environments in space including the protostellar regions and comets. The abundance and stability of NH$_2$CHO in the early stages of star formation can be better understood by incorporating the formation and destruction data in the astrochemical models. We carried out an experimental investigation to study the destruction of pure NH$_2$CHO ice at 12 K by the interaction of Ly$α$ (121.6 nm) photons. The UV photo des…
The origin of complex organic molecules (COMs) in young Class 0 protostars has been one of the major questions in astrochemistry and star formation. While COMs are thought to form on icy dust grains via gas-grain chemistry, observational constraints on their formation pathways have been limited to gas-phase detection. Sensitive mid-infrared spectroscopy with JWST enables unprecedented investigation of COM formation by measuring their ice absorption features. We present an overview of JWST/MIRI MRS spectroscopy and imaging of a young Class 0 protostar, IRAS 15398-3359, and identify several majo…
We present Spitzer 10-34 μm spectroscopic observations of the diffuse gas in the inner region of the star-forming region IC 348 of the Perseus Molecular Cloud. We find evidence for the strongest mid-IR bands of common molecules as H\textsubscript{2}, OH, H\textsubscript{2}O,CO\textsubscript{2} and NH\textsubscript{3} and of several carbonaceous molecules which may play an important role in the production of more complex hydrocarbons: HCN, C\textsubscript{2}H\textsubscript{2}, C\textsubscript{4}H\textsubscript{2}, HC\textsubscript{3}N, HC\textsubscript{5}N, C\textsubscript{2}H\textsubscript{6},…
Here we present our current updates of the gas-phase chemical reaction rates and molecular lines in the spectral synthesis code CLOUDY, and its implications in spectroscopic modelling of various astrophysical environments. We include energy levels, radiative and collisional rates for HF, CF$^+$, HC$_3$N, ArH$^+$, HCl, HCN, CN, CH, and CH$_2$. Simultaneously, we expand our molecular network involving these molecules. For this purpose, we have added 561 new reactions and have updated the existing 165 molecular reaction rates involving these molecules. As a result, CLOUDY now predicts all the lin…
The latest evolutionary phases of low- and intermediate mass stars are characterized by complex physical processes like turbulence, convection, stellar pulsations, magnetic fields, condensation of solid particles, and the formation of massive outflows that inject freshly produced heavy elements and dust particles into the interstellar medium. We use the Northern Extended Millimeter Array (NOEMA) to obtain spatially and spectrally resolved observations of the semi-regular Asymptotic Giant Branch star RS Cancri to shed light on the morpho-kinematic structure of its inner, wind forming environmen…
(Abridged) The terrestrial planets, comets, and meteorites are significantly enriched in 15N compared to the Sun and Jupiter. While the solar and jovian nitrogen isotope ratio is believed to represent the composition of the protosolar nebula, a still unidentified process has caused 15N-enrichment in the solids. Several mechanisms have been proposed to explain the variations, including chemical fractionation. However, observational results that constrain the fractionation models are scarce. While there is evidence of 15N-enrichment in prestellar cores, it is unclear how the signature evolves in…
Carbon stars have been and are extensively studied, given their complex internal structure and their peculiar chemical composition, which make them living laboratories to test stellar structure and evolution theories of evolved stars. They are the most relevant dust manufacturers, thus playing a crucial role in the evolution of galaxies. We study the dust mineralogy of circumstellar envelope (CE) of C-stars in the Large Magellanic Cloud (LMC), to achieve a better understanding of the dust formation process in the outflow of these objects. We investigate the expected distribution of C-stars in …
Context. Compact Obscured Nuclei (CONs) are an extreme phase of galaxy evolution where rapid supermassive black hole growth and$/$or compact star-forming activity is completely obscured by gas and dust. Aims. We investigate the properties of CONs in the mid-infrared and explore techniques aimed at identifying these objects such as through the equivalent width (EW) ratios of their Polycyclic Aromatic Hydrocarbon (PAH) features. Methods. We model Spitzer spectra by decomposing the continua into nuclear and star-forming components from which we then measure the nuclear optical depth, $τ_N$, of th…
Cm-wavelength Studies of Molecular Gas and Star Formation at High Redshift with the SKA
Peking University（北京大学）；Kavli Institute of Astronomy and Astrophysics at Peking University（北京大学天文与天体物理研究所）；Laboratoire Lagrange, OCA, CNRS（拉格朗日实验室，尼斯蔚蓝海岸天文台，法国国家科学研究中心）；University Catholic of Lyon- University of Lyon（里昂天主教大学-里昂大学）；International Centre for Radio Astronomy Research, University of Western Australia（西澳大利亚大学国际射电天文研究中心）；Leiden Observatory（莱顿天文台）
Where Have All the Sulfur Atoms Gone? Polycyclic Aromatic Hydrocarbon as a Possible Sink for the Missing Sulfur in the Interstellar Medium. I. The C--S Band Strengths
CORINOS IV: Quantifying Baseline-Fitting Uncertainties in SO$_2$ Ice Measurements with JWST/MIRI
University of Virginia（弗吉尼亚大学）；Star and Planet Formation Laboratory, RIKEN Pioneering Research Institute（RIKEN先锋研究所星与行星形成实验室）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；Max Planck Institute for Extraterrestrial Physics（马克斯·普朗克地外物理研究所）；Astrochemistry Laboratory, Code 691, NASA Goddard Space Flight Center（NASA戈达德太空飞行中心天体化学实验室）；Department of Physics, Catholic University of America（美利坚天主教大学物理系）；Department of Chemistry, Virginia Military Institute（弗吉尼亚军事学院化学系）；Korea Astronomy and Space Science Institute（韩国天文学与空间科学研究院）；Department of the Geophysical Sciences, University of Chicago（芝加哥大学地球物理科学系）
JWST Observations of Young protoStars (JOYS+): Detection of icy complex organic molecules and ions. I. CH$_4$, SO$_2$, HCOO$^-$, OCN$^-$, H$_2$CO, HCOOH, CH$_3$CH$_2$OH, CH$_3$CHO, CH$_3$OCHO, CH$_3$COOH
Context. Infrared spectroscopy of star and planet forming regions is at the dawn of a new age with the upcoming James Webb Space Telescope. In support of these observations, laboratory spectra are required to identify complex organic molecules in the ices that cover the dust grains in these regions. Aims. This study aims to provide reference spectra to firmly detect icy methyl formate in the different stages of star and planet forming regions. Methyl formate is mixed in astronomically relevant matrices, and the peak positions, FWHMs, and relative band intensities are characterized for differen…
Cyanogen (NCCN) is the simplest member of the series of dicyanopolyynes. It has been hypothesized that this family of molecules can be important constituents of interstellar and circumstellar media, although the lack of a permanent electric dipole moment prevents its detection through radioastronomical techniques. Here we present the first solid evidence of the presence of cyanogen in interstellar clouds through the detection of its protonated form toward the cold dark clouds TMC-1 and L483. Protonated cyanogen (NCCNH+) has been identified through the J=5-4 and J=10-9 rotational transitions us…
Binding Energies of Astrophysically Relevant Molecules on CO$_2$ Clusters: Benchmarking and the Donor-Acceptor Origin of Surface-Dependent Binding
School of Physics and Astronomy, University of Leeds（利兹大学物理与天文学院）；Departamento de Físico-Química, Facultad de Ciencias Químicas, Universidad de Concepción（康塞普西翁大学化学科学学院物理化学系）
We introduce a new modelling framework called FLiTs to simulate infrared line emission spectra from protoplanetary discs. This paper focuses on the mid-IR spectral region between 9.7 um to 40 um for T Tauri stars. The generated spectra contain several tens of thousands of molecular emission lines of H2O, OH, CO, CO2, HCN, C2H2, H2 and a few other molecules, as well as the forbidden atomic emission lines of SI, SII, SIII, SiII, FeII, NeII, NeIII, ArII and ArIII. In contrast to previously published works, we do not treat the abundances of the molecules nor the temperature in the disc as free par…
The increasing sensitivity and resolution of ground-based telescopes have enabled the detection of gas-phase complex organic molecules (COMs) across a variety of environments. Many of the detected species are expected to form on the icy surface of interstellar grains and transfer later into the gas phase. Therefore, icy material is regarded as a primordial source of COMs in the ISM. Upcoming JWST observations of interstellar ices in star-forming regions will reveal IR features of frozen molecules with unprecedented resolution and sensitivity. To identify COM features in the JWST data, lab IR s…
