Gravitational collapse of the OMC-1 region

CARMA-NRO Orion Survey: unbiased survey of dense cores and core mass functions in Orion A

The mass distribution of dense cores is a potential key to understand the process of star formation. Applying dendrogram analysis to the CARMA-NRO Orion C$^{18}$O ($J$=1--0) data, we identify 2342 dense cores, about 22 \% of which have virial ratios smaller than 2, and can be classified as gravitationally bound cores. The derived core mass function (CMF) for bound starless cores which are not associate with protostars has a slope similar to Salpeter's initial mass function (IMF) for the mass range above 1 $M_\odot$, with a peak at $\sim$ 0.1 $M_\odot$. We divide the cloud into four parts based…

Filament Intersections and Cold Dense Cores in Orion A North

We studied the filament structures and dense cores in OMC-2,3 region in Orion A North molecular cloud using the high-resolution N2H+ (1-0) spectral cube observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). The filament network over a total length of 2 pc is found to contain 170 intersections and 128 candidate dense cores. The dense cores are all displaced from the infrared point sources (possible young stars), and the major fraction of cores (103) are located around the intersections. Towards the intersections, there is also an increasing trend for the total column density Nt…

Scale-free gravitational collapse as the origin of $ρ\sim r^{-2}$ density profile -- a possible role of turbulence in regulating gravitational collapse

Astrophysical systems, such as clumps that form star clusters share a density profile that is close to $ρ\sim r^{-2}$. We prove analytically this density profile is the result of the scale-free nature of the gravitational collapse. Therefore, it should emerge in many different situations as long as gravity is dominating the evolution for a period that is comparable or longer than the free-fall time, and this does not necessarily imply an isothermal model, as many have previously believed. To describe the collapse process, we construct a model called the turbulence-regulated gravitational colla…

Independent Core Rotation in Massive Filaments in Orion

We present high-angular-resolution ALMA (Atacama Large Millimeter Array) images of N$_{2}$H$^{+}$ (1--0) that has been combined with those from the Nobeyama telescope toward OMC-2 and OMC-3 filamentary regions. The filaments (with typical widths of $\sim$ 0.1 pc) and dense cores are resolved. The measured 2D velocity gradients of cores are between 1.3 and 16.7 km\,s$^{-1}$\,pc$^{-1}$, corresponding to a specific angular momentum ($J/M$) between 0.0012 and 0.016 pc\,km\,s$^{-1}$. With respect to the core size $R$, the specific angular momentum follows a power law $J/M \propto R^{1.52~\pm~0.14}$…

Hierarchical Fragmentation of the Orion Molecular Filaments

We present a high angular resolution map of 850 um continuum emission of the Orion Molecular Cloud-3 (OMC 3) obtained with the Submillimeter Array (SMA); the map is a mosaic of 85 pointings covering an approximate area of 6'.5 x 2'.0 (0.88 x 0.27 pc). We detect 12 spatially resolved continuum sources, each with an H_2 mass between 0.3-5.7 Mo and a projected source size between 1400-8200 AU. All the detected sources are on the filamentary main ridge n_H2>10^6 cm^-3), and analysis based on the Jeans theorem suggests that they are most likely gravitationally unstable. Comparison of multi-waveleng…

ALMA Fragmented Source Catalogue in Orion (FraSCO) I. Outflow interaction within an embedded cluster in OMC-2/FIR3, FIR4, and FIR5

We present a high angular resolution ($\sim1"$) and wide-field ($2'.9 \times 1'.9$) image of the 1.3-mm continuum, CO($J$ = 2--1) line, and SiO($J$ = 5--4) line emissions toward an embedded protocluster, FIR3, FIR4, and FIR5, in the Orion Molecular Cloud 2 obtained from the Atacama Large Millimeter/submillimeter Array (ALMA). We identify 51 continuum sources, 36 of which are newly identified in this study. Their dust masses, projected sizes, and $\mathrm{H_2}$ gas number densities are estimated to be $3.8 \times 10^{-5}$--$ 1.1 \times 10^{-2} \mathrm{M_{\odot}}$, 290--2000 au, and $6.4 \times …

猎户座A整体形状纤维中重力驱动的多重分形密度结构涌现

Gravity-driven Emergence of Multi-fractal Density Structure in the Orion A Integral Shaped Filament

本研究通过密度指数分析猎户座A整体形状纤维，发现其密度结构呈多重分形标度，斜率从静止区到恒星形成区逐渐变陡，揭示重力驱动的差异坍缩过程。

Massive Quiescent Cores in Orion: Dynamical State Revealed by High-Resolution Ammonia Maps

We present combined VLA and Green Bank Telescope images of \ammonia\ inversion transitions (1,1) and (2,2) toward OMC2 and OMC3. We focus on the relatively quiescent Orion cores, which are away from the Trapezium cluster and have no sign of massive protostars nor evolved star formation, such as IRAS source, water maser, and methanol maser. The 5\arcsec\ angular resolution and $0.6 \rm{}km\,s^{-1}$ velocity resolution of these data enable us to study the thermal and dynamic state of these cores at $\sim{}0.02 \rm{}pc$ scales, comparable to or smaller than those of the current dust continuum sur…

Cosmological implications of gravitational collapse in F(R) theories

We will make a comparison between the dynamics of spherical gravitational collapse for a perturbed FLRW universe to first order in the context of general relativity, with the corresponding results obtained for the gravitational collapse under theories of modified gravity f(R). This work is aimed at obtaining an analytical model of explanation a source of large scale structures in the universe presenting an approximation of model spherical gravitational collapse under theories of modified gravity f(R).

膨胀宇宙中的引力坍缩

Gravitational collapse in the expanding Universe

该研究利用Tolman度规分析含宇宙学常数的膨胀时空中无压强流体的引力坍缩，推导得出质量为M的此类流体形成星系的最大半径表达式。