Recent theoretical studies have suggested that a magnetic field may play a crucial role in the first star formation in the universe. However, the influence of the magnetic field on the first star formation has yet to be understood well. In this study, we perform three-dimensional magnetohydrodynamic simulations taking into account all the relevant cooling processes and non-equilibrium chemical reactions up to the protostar density, in order to study the collapse of magnetized primordial gas cores with self-consistent thermal evolution. Our results show that the thermal evolution of the central core is hardly affected by a magnetic field, because magnetic forces do not prevent the contraction along the fields lines. We also find that the magnetic braking extracts the angular momentum from the core and suppresses fragmentation depending on the initial strength of the magnetic field. The angular momentum transport by the magnetic outflows is less effective than that by the magnetic braking because the outflows are launched only in a late phase of the collapse. Our results indicate that the magnetic effects become important for the field strength $B> 10^{-8}(n_{\rm H}/1\ \rm cm^{-3})^{2/3}\ \rm G$, where $n_{\rm H}$ is the number density, during the collapse phase. Finally, we compare our results with simulations using a barotropic approximation and confirm that this approximation is reasonable at least for the collapse phase. Nevertheless, self-consistent treatment of the thermal and chemical processes is essential for extending simulations to the accretion phase, in which radiative feedback by protostars plays a crucial role.
The Herschel Gould Belt Survey key project mapped the bulk of nearby star-forming molecular clouds in five far-infrared bands with the aim of compiling complete census of prestellar cores and young, embedded protostars. In this paper, we present the catalogue of the dense cores and YSOs/protostars extracted from the Herschel maps of the Lupus I, III, and IV molecular clouds. The physical properties of the detected objects were derived by fitting their spectral energy distributions. A total of 532 dense cores, out of which 103 are presumably prestellar in nature, and 38 YSOs/protostars have bee…
Context. The nitrogen isotopic ratio is considered an important diagnostic tool of the star formation process, and $N_2H^+$ is particularly important because it is directly linked to molecular nitrogen $N_2$. However, theoretical models still lack to provide an exhaustive explanation for the observed $^{14}N/^{15}N$ values. Aims. Recent theoretical works suggest that the $^{14}N/^{15}N$ behaviour is dominated by two competing reactions that destroy $ N_2H^+$: dissociative recombination and reaction with CO. When CO is depleted from the gas phase, if $N_2H^+$ recombination rate is lower with re…
Direct evidence for magnetohydrodynamic disk winds driving rotating outflows in protostar HOPS 358
Seoul National University（首尔大学）；SNU Astronomy Research Center, Seoul National University（首尔大学天文研究中心）；NRC Herzberg Astronomy and Astrophysics（NRCA Herzberg天体物理学与天文学研究所）；University of Victoria（维多利亚大学）；Peking University（北京大学）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学柯尔夫天体物理与天文学研究所）；Academia Sinica（中央研究院）；Institute of Astronomy and Astrophysics, Academia Sinica（中央研究院天文及天体物理研究所）；Leiden University（莱顿大学）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；National Radio Astronomy Observatory（美国国家射电天文台）
Corona Australis 151: an extremely young protostar
European Southern Observatory（欧洲南方天文台）；Max-Planck-Institut für Extraterrestrische Physik（马克斯·普朗克地外物理研究所）；University of Helsinki（赫尔辛基大学）；Institute for Advanced Study, Kyushu University（九州大学高等研究院）；Kyushu University（九州大学）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Kyushu Sangyo University（九州产业大学）；National Astronomical Observatory of Japan（日本国立天文台）
A numerical hydrodynamical model for the evolution of spherically symmetric collapsing clouds, designed for the calculation of the thermal structure of these objects in both the prestellar and protostellar stages of their evolution, is presented. Distinctive features of the model include the possibility of independently describing the temperatures of the gas and dust, which is extremely important when calculating the thermal structure of prestellar and protostellar clouds, and the account of the radiation flux from the central protostar. This model is used to compare the theoretical density an…
High degrees of deuterium fractionation are commonly found in cold prestellar cores and in the envelopes around young protostars. As it brings strong constraints to chemical models, deuterium chemistry is often used to infer core history or molecule formation pathways. Whereas a large number of observations is available regarding interstellar deuterated stable molecules, relatively little is known about the deuteration of hydride radicals, as their fundamental rotational transitions are at high frequencies where the atmosphere is mostly opaque. Nitrogen hydride radicals are important species i…
Using three-dimensional magnetohydrodynamics simulations, the driving of protostellar jets is investigated in different star-forming cores with the parameters of magnetic field strength and mass accretion rate. Powerful high-velocity jets appear in strongly magnetized clouds when the mass accretion rate onto the protostellar system is lower than $\dot{M} \lesssim 10^{-3}\,{\rm M}_\odot$ yr$^{-1}$. On the other hand, even at this mass accretion rate range, no jets appear for magnetic fields of prestellar clouds as weak as $μ_0 \gtrsim 5$--$10$, where $μ_0$ is the mass-to-flux ratio normalized b…
ALMA observations of the Extended Green Object G19.01$-$0.03: II. A massive protostar with typical chemical abundances surrounded by four low-mass prestellar core candidates
Formation of protostars and the launching of stellar core outflows with moving-mesh radiation non-ideal magnetohydrodynamics
Max-Planck-Institut für Astrophysik（马克斯·普朗克天体物理研究所）；Excellence Cluster ORIGINS（ORIGINS 卓越集群）；Center for Astrophysics | Harvard & Smithsonian（哈佛与史密森尼天体物理中心）；Max-Planck-Institut für Extraterrestrische Physik（马克斯·普朗克地外物理研究所）
Direct observational measurements of the magnetic field strength in prestellar cores typically find supercritical mass-to-flux ratios, suggesting that the magnetic field is insufficient to prevent gravitational collapse. These measurements suffer from significant uncertainties; an alternative approach is to utilise the sensitivity of prestellar chemistry to the evolutionary history, and indirectly constrain the degree of magnetic support. We combine non-ideal magnetohydrodynamic simulations of prestellar cores with time-dependent chemistry and radiative transfer modelling, producing synthetic …
We perform a sequence of 3D magnetohydrodynamic (MHD) simulations of the outflow-core interaction for a massive protostar forming via collapse of an initial cloud core of $60~{M_\odot}$. This allows us to characterize the properties of disk wind driven outflows from massive protostars, which can allow testing of different massive star formation theories. It also enables us to assess quantitatively the impact of outflow feedback on protostellar core morphology and overall star formation efficiency. We find that the opening angle of the flow increases with increasing protostellar mass, in agreem…
The origin of the heavily fractionated reservoir of nitrogen in comets remains an issue in the theory of their formation and hence of the solar system. Whether the fractionated reservoir traced by comets is inherited from the interstellar cloud or is the product of processes taking place in the protostar, or in the protoplanetary disk, remains unclear. So far, observations of nitrogen isotopic ratios in protostars or prestellar cores have not securely identified such a fractionated reservoir owing to the intrinsic difficulty of direct isotopic ratios measurements. In this article, we report th…
We summarize the first results from the Gould Belt survey, obtained toward the Aquila Rift and Polaris Flare regions during the 'science demonstration phase' of Herschel. Our 70-500 micron images taken in parallel mode with the SPIRE and PACS cameras reveal a wealth of filamentary structure, as well as numerous dense cores embedded in the filaments. Between ~ 350 and 500 prestellar cores and ~ 45-60 Class 0 protostars can be identified in the Aquila field, while ~ unbound starless cores and no protostars are observed in the Polaris field. The prestellar core mass function (CMF) derived for the…
We investigate differences in the molecular abundances between magnetically super- and sub-critical prestellar cores, performing three-dimensional non-ideal magnetohydrodynamical (MHD) simulations with varying densities and magnetic field strengths, and post-processing the results with a time-dependent gas-grain chemical code. Most molecular species show significantly more central depletion in subcritical models, due to the longer duration of collapse. However, the directly observable quantities - the molecule to hydrogen column density ratios - are generally too similar for observational data…
We have performed survey-type observations in 1 mm continuum and molecular lines toward dense cores (32 prestellar + 7 protostellar) with an average density of $\gtrsim$10$^5$ cm$^{-3}$ in the Taurus molecular clouds using the Atacama Large Millimeter/submillimeter Array-Atacama Compact Array (ALMA-ACA) stand-alone mode with an angular resolution of 6.$''$5 ($\sim$900 au). The primary purpose of this study is to investigate the innermost part of dense cores toward understanding the initial condition of star formation. In the protostellar cores, contributions from protostellar disks dominate th…
The formation of a close binary system is investigated using a three-dimensional resistive magnetohydrodynamics simulation. Starting from a prestellar cloud, the cloud evolution is calculated until about 400 yr after protostar formation. Fragmentation occurs in the gravitationally collapsing cloud and two fragments evolve into protostars. The protostars orbit each other and a protobinary system appears. A wide-angle low-velocity outflow emerges from the circumbinary streams that encloses two protostars, while each protostar episodically drives high-velocity jets. Thus, the two high-velocity je…
Extremely large deuteration of several molecules has been observed towards prestellar cores and low-mass protostars for a decade. New observations performed towards low-mass protostars suggest that water presents a lower deuteration in the warm inner gas than in the cold external envelope. We coupled a gas-grain astrochemical model with a one-dimension model of collapsing core to properly follow the formation and the deuteration of interstellar ices as well as their subsequent evaporation in the low-mass protostellar envelopes with the aim of interpreting the spatial and temporal evolutions of…
Recent observations of the HDO/H$_2$O ratio toward protostars in isolated and clustered environments show an apparent dichotomy, where isolated sources show higher D/H ratios than clustered counterparts. Establishing which physical and chemical processes create this differentiation can provide insights into the chemical evolution of water during star formation and the chemical diversity during the star formation process and in young planetary systems. Methods: The evolution of water is modeled using 3D physicochemical models of a dynamic star-forming environment. The physical evolution during …
We present high angular resolution SMA and Spitzer observations toward the Bok globule CB17. SMA 1.3mm dust continuum images reveal within CB17 two sources with an angular separation of about 21" (about 5250 AU at a distance of 250 pc). The northwestern continuum source, referred to as CB17 IRS, dominates the infrared emission in the Spitzer images, drives a bipolar outflow extending in the northwest-southeast direction, and is classified as a low luminosity Class0/I transition object (L_bol ~ 0.5 L_sun). The southeastern continuum source, referred to as CB17 MMS, has faint dust continuum emis…
The extremely young Class 0 object B1b-S and the first hydrostatic core (FSHC) candidate, B1b-N, provide a unique opportunity to study the chemical changes produced in the elusive transition from the prestellar core to the protostellar phase. We present 40"x70" images of Barnard 1b in the 13CO 1->0, C18O 1->0, NH2D 1_{1,1}a->1_{0,1}s, and SO 3_2->2_1 lines obtained with the NOEMA interferometer. The observed chemical segregation allows us to unveil the physical structure of this young protostellar system down to scales of ~500au. The two protostellar objects are embedded in an elongated conden…
Observations of dust polarized emission toward star forming regions trace the magnetic field component in the plane of the sky and provide constraints to theoretical models of cloud collapse. We compare high-angular resolution observations of the submillimeter polarized emission of the low-mass protostellar source NGC 1333 IRAS 4A with the predictions of three different models of collapse of magnetized molecular cloud cores. We compute the Stokes parameters for the dust emission for the three models. We then convolve the results with the instrumental response of the Submillimeter Array observa…
Given the low ionization fraction of molecular clouds, ambipolar diffusion is thought to be an integral process in star formation. However, chemical and radiative-transfer effects, observational challenges, and the fact that the ion-neutral drift velocity is inherently very small render a definite detection of ambipolar diffusion extremely non-trivial. Here, we study the ion-neutral drift velocity in a suite of chemodynamical, non-ideal magnetohydrodynamic (MHD), two-dimensional axisymmetric simulations of prestellar cores where we alter the temperature, cosmic-ray ionization rate, visual exti…
To constrain models of high-mass star formation, the Herschel/HOBYS KP aims at discovering massive dense cores (MDCs) able to host the high-mass analogs of low-mass prestellar cores, which have been searched for over the past decade. We here focus on NGC6334, one of the best-studied HOBYS molecular cloud complexes. We used Herschel PACS and SPIRE 70-500mu images of the NGC6334 complex complemented with (sub)millimeter and mid-infrared data. We built a complete procedure to extract ~0.1 pc dense cores with the getsources software, which simultaneously measures their far-infrared to millimeter f…
With the Submillimeter Array, the brightest (sub)millimeter continuum source in the OMC-2/3 region, MMS 6, has been observed in the 850 um continuum emission with approximately 10 times better angular resolution than previous studies (~0.3"; ~120 AU at Orion). The deconvolved size, the mass, and the column density of MMS 6-main are estimated to be 0.32"x0.29" (132 AUx120 AU), 0.29 Mo, and 2.1x10^{25} cm^{-2}, respectively. The estimated extremely high mean number density, 1.5x10^{10} cm^{-3}, suggests that MMS 6-main is likely optically thick at 850 um. We compare our observational data with t…
The formation epoch of protostellar disks is debated because of the competing roles of rotation, turbulence, and magnetic fields in the early stages of low-mass star formation. Magnetohydrodynamics simulations of collapsing cores predict that rotationally supported disks may form in strongly magnetized cores through ambipolar diffusion or misalignment between the rotation axis and the magnetic field orientation. Detailed studies of individual sources are needed to cross check the theoretical predictions. We present 0.06-0.1" resolution images at 350 GHz toward B1b-N and B1b-S, which are young …
We present high-resolution (< ~160 au) Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm observations of the high-mass prestellar core candidate G11.92-0.61 MM2, which reveal that this source is in fact a protobinary system with a projected separation of 505 au. The binary components, MM2E and MM2W, are compact (radii < 140 au) sources within the partially optically thick dust emission with alpha$_{0.9 cm-1.3 mm}$=2.47-2.94. The 1.3 mm brightness temperatures, T$_b$=68.4/64.6 K for MM2E/MM2W, imply internal heating and minimum luminosities L$_*$ > 24.7 Lsun for MM2E and L$_*$ > 12.6 L…
Exploring the structure and dynamics of cold starless clouds is necessary to understand the different steps leading to the formation of protostars. Because clouds evolve slowly, many of them must be studied in detail to pick up different moments of a cloud's lifetime. We study here L1506C in the Taurus region, a core with interesting dust properties which have been evidenced with the PRONAOS balloon-borne telescope. To trace the mass content of L1506C and its kinematics, we mapped the dust emission, and the line emission of two key species, C18O and N2H+ (plus 13CO and C17O). This cloud shows …
Non-ideal magnetohydrodynamic (MHD) effects are thought to be gravity's closest ally in overcoming the support of magnetic fields and in forming stars. Here, we modify the publicly available version of the adaptive mesh refinement code FLASH (Fryxell et al. 2000; Dubey et al. 2008) to include a detailed treatment of non-ideal MHD and study such effects in collapsing prestellar cores. We implement two very extended non-equilibrium chemical networks, the largest of which is comprised of $\sim$ 300 species and includes a detailed description of deuterium chemistry. The ambipolar-diffusion, Ohmic …
Deuterated methanol is one of the most robust windows astrochemists have on the individual chemical reactions forming deuterium-bearing molecules and the physicochemical history of the regions where they reside. The first-time detection of mono- and di-deuterated methanol in a cometary coma is presented for comet 67P/Churyumov-Gerasimenko using Rosetta-ROSINA data. D-methanol (CH3OD and CH2DOH combined) and D2-methanol (CH2DOD and CHD2OH combined) have an abundance of 5.5+/-0.46 and 0.00069+/-0.00014 per cent relative to normal methanol. The data span a methanol deuteration fraction (D/H ratio…
The canonical theory of star formation in a magnetized environment predicts the formation of hourglass-shaped magnetic fields during the prestellar collapse phase. In protostellar cores, recent observations reveal complex and strongly distorted magnetic fields in the inner regions that are sculpted by rotation and outflows. We conduct resistive, nonideal magnetohydrodynamic (MHD) simulations of a protostellar core and employ the radiative transfer code POLARIS to produce synthetic polarization segment maps. Comparison of our mock-polarization maps based on the toroidal-dominated magnetic field…
One critical remaining issue to unclear the initial mass function of the first (Population III) stars is the final fate of secondary protostars formed in the accretion disk, specifically whether they merge or survive. We focus on the magnetic effects on the first star formation under the cosmological magnetic field. We perform a suite of ideal magnetohydrodynamic simulations until 1000 years after the first protostar formation. Instead of the sink particle technique, we employ a stiff equation of state approach to represent the magnetic field structure connecting to protostars. Ten years after…
Massive protostars attain high luminosities as they are actively accreting and the radiation pressure exerted on the gas in the star's atmosphere may launch isotropic high-velocity winds. These winds will collide with the surrounding gas producing shock-heated ($T\sim 10^7$ K) tenuous gas that adiabatically expands and pushes on the dense gas that may otherwise be accreted. We present a suite of 3D radiation-magnetohydrodynamic simulations of the collapse of massive prestellar cores and include radiative feedback from the stellar and dust-reprocessed radiation fields, collimated outflows, and,…
Probing the ion-neutral drift velocity towards the L1544 prestellar core: Detection of ambipolar diffusion using N$_2$D$^+$ and para-NH$_2$D
Institute for Advanced Study, Kyushu University（九州大学高等研究院）；Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University（九州大学理学部地球行星科学系）；National Astronomical Observatory of Japan（日本国立天文台）；Max-Planck-Institut für Extraterrestrische Physik（马克斯·普朗克地外物理研究所）；Kaghoshima University（鹿儿岛大学）；Faculty of Science and Engineering, Kyushu Sangyo University（九州产业大学理工学部）；Institut de Radioastronomie Millimétrique (IRAM)（毫米波射电天文学研究所）
The infrared dark clouds (IRDCs) G11.11$-$0.12 and G28.34$+$0.06 are two of the best-studied IRDCs in our Galaxy. These two clouds host clumps at different stages of evolution, including a massive dense clump in both clouds that is dark even at 70 and 100$μ$m. Such seemingly quiescent massive dense clumps have been speculated to harbor cores that are precursors of high-mass stars and clusters. We observed these two "prestellar" regions at 1mm with the Submillimeter Array (SMA) with the aim of characterizing the nature of such cores. We show that the clumps fragment into several low- to high-ma…
In the present-day universe, magnetic fields play such essential roles in star formation as angular momentum transport and outflow driving, which control circumstellar disc formation/fragmentation and also the star formation efficiency. While only a much weaker field has been believed to exist in the early universe, recent theoretical studies find that strong fields can be generated by turbulent dynamo during the gravitational collapse. Here, we investigate the gravitational collapse of a cloud core ($\sim 10^{3}\ \rm cm^{-3}$) up to protostar formation ($\sim 10^{20}\ \rm cm^{-3}$) by non-ide…
Planetary systems such as our own are formed after a long process where matter condenses from diffuse clouds to stars, planets, asteroids, comets and residual dust, undergoing dramatic changes in physical and chemical state in less than a few million years. Several studies have shown that the chemical composition during the early formation of a Solar-type planetary system is a powerful diagnostic to track the history of the system itself. Among the approximately 270 molecules so far detected in the ISM, the so-called interstellar complex organic molecules (iCOMs) are of particular interest bot…
Chamaeleon I is the most active region in terms of star formation in the Chamaeleon molecular cloud complex. Its population of prestellar and protostellar cores is not known and a controversy exists concerning its history of star formation. Our goal is to characterize the earliest stages of star formation in this cloud. We used the bolometer array LABOCA at APEX to map the cloud in dust continuum emission at 870 micron. The detected sources are analysed by carefully taking into account the spatial filtering inherent in the data reduction process. A search for associations with YSOs is performe…
Recent studies of the nearest star-forming clouds of the Galaxy at submillimeter wavelengths with the Herschel Space Observatory have provided us with unprecedented images of the initial conditions and early phases of the star formation process. The Herschel images reveal an intricate network of filamentary structure in every interstellar cloud. These filaments all exhibit remarkably similar widths - about a tenth of a parsec - but only the densest ones contain prestellar cores, the seeds of future stars. The Herschel results favor a scenario in which interstellar filaments and prestellar core…
Recent studies of the nearest star-forming clouds of the Galaxy at submillimeter wavelengths with the Herschel Space Observatory have provided us with unprecedented images of the initial conditions and early phases of the star formation process. The Herschel images reveal an intricate network of filamentary structure in every interstellar cloud. These filaments all exhibit remarkably similar widths - about a tenth of a parsec - but only the densest ones contain prestellar cores, the seeds of future stars. The Herschel results favor a scenario in which interstellar filaments and prestellar core…
In dense starless and protostellar cores, the relative abundance of deuterated species to their non-deuterated counterparts can become orders of magnitude greater than in the local interstellar medium. This enhancement proceeds through multiple pathways in the gas phase and on dust grains, where the chemistry is strongly dependent on the physical conditions. In this Chapter, we discuss how sensitive, high resolution observations with the ngVLA of emission from deuterated molecules will trace both the dense gas structure and kinematics on the compact physical scales required to track the gravit…
Protostellar Outflows at the EarliesT Stages (POETS). IX. Magnetohydrodynamic disk winds traced by SO and SO$_2$ in luminous protostars
INAF - Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切特里天文台）；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；INAF - Osservatorio Astronomico di Cagliari（意大利国家天体物理研究所卡利亚里天文台）；UK Astronomy Technology Centre, Royal Observatory Edinburgh（英国天文学技术中心爱丁堡皇家天文台）；Faculty of Physics, University of Duisburg-Essen（杜伊斯堡-埃森大学物理学院）；I. Physikalisches Institut, Universität zu Köln（科隆大学第一物理研究所）；Universidad Nacional Autónoma de México, Instituto de Radioastronomía y Astrofísica（墨西哥国立自治大学无线电天文学与天体物理研究所）；Department of Physics and Astronomy, McMaster University（麦克马斯特大学物理与天文学系）
During the transition phase from a prestellar to a protostellar cloud core, one or several protostars can form within a single gas core. The detailed physical processes of this transition, however, still remain unclear. We present 1.3 mm dust continuum and molecular line observations with the Atacama Large Millimeter/submillimeter Array (ALMA) toward 43 protostellar cores in the Orion Molecular Cloud Complex ($λ$ Orionis, Orion B, and Orion A) with an angular resolution of $\sim$ 0.35" ($\sim$ 140 au). In total, we detect 13 binary/multiple systems. We derive an overall multiplicity frequency …
We describe a numerical scheme for magnetohydrodynamics simulations of dust-gas mixture by extending smoothed particle magnetohydrodynamics. We employ the single-species particle approach to describe dust-gas mixture with several modifications from the previous studies. We assume that the charged and neutral dusts can be treated as single-fluid and the electro-magnetic force acts on the gas and that on the charged dust is negligible. The validity of these assumption in the context of protostar formation is not obvious and is extensively evaluated. By investigating the electromagnetic force and…
The degree of coupling between the gas and the magnetic field during the collapse of a core and the subsequent formation of a disk depends on the assumed dust size distribution. We study the impact of grain-grain coagulation on the evolution of magnetohydrodynamic (MHD) resistivities during the collapse of a prestellar core. We use a 1-D model to follow the evolution of the dust size distribution, out-of-equilibrium ionization state and gas chemistry during the collapse of a prestellar core. To compute the grain-grain collisional rate, we consider models for both random and systematic, size-de…
We present Herschel, ALMA Compact Array (ACA), and Caltech Submillimeter Observatory (CSO) observations of the prestellar core in L1689N, which has been suggested to be interacting with a molecular outflow driven by the nearby solar type protostar IRAS 16293-2422. This source is characterized by some of the highest deuteration levels seen in the interstellar medium. The change in the NH2D line velocity and width across the core provides clear evidence of an interaction with the outflow, traced by the high-velocity water emission. Quiescent, cold gas, characterized by narrow line widths is seen…
We investigate the molecular evolution and D/H abundance ratios that develop as star formation proceeds from a dense-cloud core to a protostellar core, by solving a gas-grain reaction network applied to a 1-D radiative hydrodynamic model with infalling fluid parcels. Spatial distributions of gas and ice-mantle species are calculated at the first-core stage, and at times after the birth of a protostar. Gas-phase methanol and methane are more abundant than CO at radii $r\lesssim 100$ AU in the first-core stage, but gradually decrease with time, while abundances of larger organic species increase…
The formation of Population III stars is investigated using resistive magnetohydrodynamic simulations. Starting from a magnetized primordial prestellar cloud, we calculate the cloud evolution several hundreds of years after first protostar formation, resolving the protostellar radius. When the natal minihalo field strength is weaker than B \lesssim 10^-13 (n/1 cm^-3)^-2/3 G (n is the hydrogen number density), magnetic effects can be ignored. In this case, fragmentation occurs frequently and a stellar cluster forms, in which stellar mergers and mass exchange between protostars contribute to the…
Inventories of Rich Carbon-Chain Chemistry in Prestellar and Starless Cores in the Perseus Molecular Cloud
University of California, Berkeley（加州大学伯克利分校）；National Radio Astronomy Observatory（美国国家射电天文台）；RIKEN Cluster for Pioneering Research（理化学研究所先导研究集群）；Steward Observatory, University of Arizona（亚利桑那大学斯图尔德天文台）；Centro de Astrobiología (CAB), CSIC-INTA（天体生物学中心，西班牙科学研究中心-国家航空航天技术研究所）
We calculate the evolution of cloud cores embedded in different envelopes to investigate environmental effects on the mass accretion rate onto protostars. As the initial state, we neglect the magnetic field and cloud rotation, and adopt star-forming cores composed of two parts: a centrally condensed core and an outer envelope. The inner core has a critical Bonnor-Ebert density profile and is enclosed by the outer envelope. We prepare 15 star-forming cores with different outer envelope densities and gravitational radii, within which the gas flows into the collapsing core, and calculate their ev…
Astronomers have yet to establish whether high-mass protostars form from high-mass prestellar cores, similar to their lower-mass counterparts, or from lower-mass fragments at the heart of a pre-protostellar cluster undergoing large-scale collapse. Part of the uncertainty is due to a shortage of envelope structure data on protostars of a few tens of solar masses, where we expect to see a transition from intermediate-mass star formation to the high-mass process. We sought to derive the masses, luminosities, and envelope density profiles for eight sources in Cygnus-X, whose mass estimates in the …
