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天文物理理論與觀測整合研究計畫(CHARMS)

CHARMS (英文)

研究成果藝廊

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<b>Left</b> – Surface density distribution of a forming circumplanetary disk in a protoplanetary disk with the Antares three-dimensional global simulation. A planet of one-Jupiter mass is placed at (x,y) = (5.2,0) au. The color scale is stretched logarithmically. The level boundaries of the nested-grid mesh refinement are shown in white lines. <b>Center</b> – Temperature distribution of the disk obtained with the radiative transfer code Hyperion. The photon sources are the central 4500-K star and an accreting planet of ~1000 K at 5.2 au from the star. The circumplanetary dust is heated up to ~ 1000 K and produces thermal emission. <b>Right</b> – Monochromatic synthetic image corresponding to the 1-mm dust continuum imaging, obtained with Hyperion. The surface brightness is logarithmically stretched in units of MJy/arcsec<sup>2</sup>.

Dust Radiative Transfer on a Global Hydrodynamic Simulation of a Forming Circumplanetary Disk

HIGH-RESOLUTION CO OBSERVATION OF THE CARBON STAR CIT 6

A sample picture based on the radiative transfer code Perspective exploring a very early stage disk formed within the MHD model of Li et al. (2014). The picture shows gas column density and linear polarization component q along the line of sight, inclined 15 degrees from the midplane. The early disk in the model shows a spiral-like shape, presumably created by the magnetic field aligned along the rotational plane of the original cloud. (Väisälä, Shang et al., a work in progress)

Polarization Calculation and Visualization from MHD Simulation Data

Illustration of wind model (left) and attempts to reproduce the velocity pattern of the blue lobe of the I04166 jet (right). The upper part of the left illustration shows two pieces of spherical shell layers, whose velocities point purly in spherical-r directions. The lower part shows how they appear on a position-velocity diagram, where two tooth-like features is seen. Such features greatly resemble the observed velocity pattern in the right. In the upper-right panel we plot the observed CO J=2–1 and CO J=3–2 emissions with blue contours, and the green line segments are model predictions. The color scale in the lower-right panel shows the synthesized CO J=2–1 PV diagram from one of our MHD numerical simulations. The good agreement demonstrates the feasibility of the wind geometry model. The simulated data was convolved with a Gaussian beam of 420 AU FWHM before extracting the PV diagram to better mimic the observation result.

Ejection History of Protostellar Outflow IRAS 04166+2706

$Density plots in log scale from simulations of two-temperature outflow model. (Left) Mosaic of simulations demonstrating effects of varying temperature and magnetization degree. Panel indices of (a) to (c) shows decreasing magnetic field strength, and (1) to (3) shows increasing wind temperature. The central axial jet is less collimated and the shell structure is widened when magnetic force is relatively unimportant. (Right) Comparisons that demonstrates the effect of poloidal magnetic field. The top panel is run with poloidal field and the lower without. Thick solid line is where wind mass fraction is 1%, and thick dashed line is where bulk velocities equal the ambient sound speed. The shell is mode corrugated in cases without poloidal field (Wang et al. 2015)$

A Two-temperature Model of Magnetized Protostellar Outflows

Visualization of RT Simulation

Distribution of the logarithm of the mass density ρ and velocity field (unit vectors) on the equatorial plane, for Models I (left panel, non-rotating) and J (right, rotating) that include both ambipolar diffusion and (enhanced) Ohmic dissipation for magnetic decoupling at small radii. Again, both models show filamentary structures in the inner protostellar accretion flow driven by magnetic interchange instability.

Protostellar Accretion Flows Destabilized by Magnetic Flux Redistribution

<b>Effects of temperature and magnetization on molecular outflows:</b> the structure of the base of outflows at 1000 yr is shown with different physical conditions. Panels (a) to (c) shows the Alfvénic Mach number from 6, 30, to 90 [decreasing magnetic field strength]; and (1) to (3) shows the wind temperature from 10 K, 400 K, to 2000 K [increasing wind temperature]. These corresponds to different plasma beta parameter (β<sub>plasma</sub> ≣ 8πa<sup>2</sup>ρ/B<sup>2</sup>) from 0.001 to 46. The central axial jet is less collimated and the shell structure is widened when β<sub>plasma</sub> increases. In these cases, the poloidal magnetic field in the toroid is not included.

Two-Temperature Model for Magnetized Protostellar Outflows

天文物理理論與觀測整合研究計畫（CHARMS）由中研院天文所與高等理論天文物理中心發起，旨在結合最尖端的理論與計算天文物理，詮釋最新觀測天文學得到的資料，作為理論與觀測的橋樑。面對當代高靈敏度與高解析度天文儀器，如阿塔卡瑪大型毫米與次毫米波陣列（ALMA），其觀測資料具備的細節前所未有，亟需計算輻射機制，從數值模擬數據推得光度分佈，才能確實合理地比較模型預測與觀測結果。本計畫即藉由發展能夠進行流體力學與磁流體力學數值模擬、計算化學方程式平衡、與計算輻射轉移模型的軟體模組，達到比較並詮釋觀測結果的目標。

自2008年起，本計畫持續致力於數值計算方法的開發，包括三大方向：流體力學與磁流體力學數值模擬程式集ZeusTW、同時計算化學方程與流體力學方程之數值模擬程式集KM1/KM2、與輻射轉移計算程式集SPARX。其科學研究方向廣泛，已應用於年輕恆星形成前期塌縮雲氣、恆星盤形成、年輕恆星噴流與分子外流、原始拱行星盤形成、大質量恆星形成區域、與低質量恆星晚期演化等。當代天文物理學各領域將面對數量與質量更豐富的觀測資料，本計畫亦將持續發展演進，冀望能提供臺灣天文學界研究的支持後盾與前進動能。