arXiv subjects

Jixing Ge

Publications and source records attributed to Jixing Ge.

6 recordsLinked to original sources

arXiv2026

The ALMA-QUARKS survey: Investigating Thermal Feedback of Massive Protostars in Hot Molecular Cores

We identify a sample of 83 spatially resolved hot molecular cores (HMCs) in the QUARKS survey, aiming at investigating thermal feedback from massive stars. Using CH$_3$CN\,(12--11) line emission together with 1.3\,mm continuum data we derive the radial temperature, volume density and \ch3cn{} abundance profiles for the 83 HMCs. Based on the envelope temperature and density profiles, we compute the luminosities of the embedded massive protostars with \radmc{} radiation transfer model. The derived luminosities are comparable (within $\sim1$ dex) to the bolometric luminosities of their natal clumps and show strong correlations with several core-scale properties, including the HMC mass ($Log[ M_\mathrm{env}] = 1.01\,Log [L_\star] - 4.80$), the inner core radius (the flat radius of Plummer-like volume density profile) ($Log[a] = 0.46\,Log[L_\star] + 0.52$) and the central density $ (Log[n_c] = -0.55 Log[L_\star] +10.47) $. These empirical relations provide useful observational constraints for physical models of protostellar objects. Importantly, we find a strong positive correlation between the massive protostellar luminosity and the local thermal Jeans mass. The derived Jeans masses, $M_\mathrm{Jeans}$, exceed the HMC masses $M_\mathrm{env}$, with the average $M_\mathrm{Jeans}$ being two times larger than the average $M_\mathrm{env}$. This provides observational evidence that thermal feedback from massive protostars can effectively suppress further fragmentation of HMCs, thereby promoting massive star formation. In addition, the positive correlation between massive protostellar luminosity and natal clump mass suggests that more massive clumps preferentially host more luminous protostars, leading to stronger thermal feedback.

astro-ph.GA↗

arXiv2024

Can near-to-mid infrared spectral energy distribution quantitatively trace protoplanetary disk evolution?

Infrared (IR) spectral energy distribution (SED) is the major tracer of protoplanetary disks. It was recently proposed to use the near-to-mid IR (or K-24) SED slope $\alpha$ defined between 2-24$\mu$m as a potential quantitative tracer of disk age. We critically examine the viability of this idea and confront it with additional statistics of IR luminosities and SED shapes. We point out that, because the statistical properties of most of the complicated physical factors involved in disk evolution are still poorly understood in a quantitative sense, the only viable way is to assume them to be random so that an idealized `average disk' can be defined, which allows the $\alpha$ histogram to trace its age. We confirm that the statistics of the zeroth order (luminosity), first order (slope $\alpha$) and second order characteristics (concavity) of the observed K-24 SEDs indeed carry useful information upon the evolutionary processes of the `average disk'. We also stress that intrinsic diversities in K-24 SED shapes and luminosities are always large at the level of individual stars so that the application of the evolutionary path of the `average disk' to individual stars must be done with care. The data of most curves in plots are provided on GitHub.

astro-ph.SR↗

arXiv2022

Disk dissipation, giant planet formation and star-formation-rate fluctuations in the past three-million-year history of Gould's Belt

Although episodic star formation (SF) had been suggested for nearby SF regions, a panoramic view to the latest episodic SF history in the solar neighborhood is still missing. By uniformly constraining the slope $\alpha$ of infrared spectral energy distributions (SEDs) of young stellar objects (YSOs) in the 13 largest Gould's Belt (GB) protoclusters surveyed by Spitzer Space Telescope, we have constructed a cluster-averaged histogram of $\alpha$ representing YSO evolution lifetime as a function of the $\alpha$ value. Complementary to the traditional SED classification scheme (0, I, F, II, III) that is based on different $\alpha$ values, a staging scheme (A,B,C,D,E) of SED evolution is advised on the basis of the $\alpha$ statistical features that can be better matched to the physical stages of disk dissipation and giant planet formation. This has also allowed us to unravel the fluctuations of star formation rate (SFR) in the past three-million-year (3 Myr) history of these GB protoclusters. Diverse evolutionary patterns such as single peak, double peaks and on-going acceleration of SFR are revealed. The SFR fluctuations are between $20\%\sim60\%$ ($\sim40\%$ on average) and no dependence on the average SFR or the number of SFR episodes is found. However, spatially close protoclusters tend to share similar SFR fluctuation trends, indicating that the driving force of the fluctuations should be at size scales beyond the typical cluster sizes of several parsec.

astro-ph.SR↗

arXiv2022

ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions -- XI. From inflow to infall in hub-filament systems

We investigate the presence of hub-filament systems in a large sample of 146 active proto-clusters, using H$^{13}$CO$^{+}$ J=1-0 molecular line data obtained from the ATOMS survey. We find that filaments are ubiquitous in proto-clusters, and hub-filament systems are very common from dense core scales ($\sim$0.1 pc) to clump/cloud scales ($\sim$1-10 pc). The proportion of proto-clusters containing hub-filament systems decreases with increasing dust temperature ($T_d$) and luminosity-to-mass ratios ($L/M$) of clumps, indicating that stellar feedback from H{\sc ii} regions gradually destroys the hub-filament systems as proto-clusters evolve. Clear velocity gradients are seen along the longest filaments with a mean velocity gradient of 8.71 km s$^{-1}$pc$^{-1}$ and a median velocity gradient of 5.54 km s$^{-1}$pc$^{-1}$. We find that velocity gradients are small for filament lengths larger than $\sim$1~pc, probably hinting at the existence of inertial inflows, although we cannot determine whether the latter are driven by large-scale turbulence or large-scale gravitational contraction. In contrast, velocity gradients below $\sim$1~pc dramatically increase as filament lengths decrease, indicating that the gravity of the hubs or cores starts to dominate gas infall at small scales. We suggest that self-similar hub-filament systems and filamentary accretion at all scales may play a key role in high-mass star formation.

astro-ph.GA↗

arXiv2021

GGCHEMPY: A pure Python-based gas-grain chemical code for efficient simulation of interstellar chemistry

In this paper, we present a new gas-grain chemical code for interstellar clouds written in pure Python (GGCHEMPY). By combining with the high-performance Python compiler Numba, GGCHEMPY is as efficient as the Fortran-based version. With the Python features, flexible computational workflows and extensions become possible. As a showcase, GGCHEMPY is applied to study the general effects of three-dimensional projection on molecular distributions using a two-core system which can be easily extended for more complex cases. By comparing the molecular distribution differences between two overlapping cores and two merging cores, we summarized the typical chemical differences such as, N2H+, HC3N, C2S, H2CO, HCN and C2H, which can be used to interpret 3-D structures in molecular clouds.

astro-ph.GA↗

arXiv2014

Early-stage star forming cloud cores in GLIMPSE Extended Green Objects (EGOs) as traced by organic species

In order to investigate the physical and chemical properties of massive star forming cores in early stages, we analyse the excitation and abundance of four organic species, CH3OH, CH3OCH3, HCOOCH3 and CH3CH2CN, toward 29 Extended Green Object (EGO) cloud cores that were observed by our previous single dish spectral line survey. The EGO cloud cores are found to have similar methanol J_3-J_2 rotation temperatures of ~44 K, a typical linear size of ~0.036 pc, and a typical beam averaged methanol abundance of several 10^(-9) (the beam corrected value could reach several 10^(-7)). The abundances of the latter three species, normalized by that of methanol, are found to be correlated also across a large variety of clouds such as EGO cloud cores, hot corinos, massive hot cores and Galactic Center clouds. The chemical properties of the EGO cloud cores lie between that of hot cores and hot corinos. However, the abundances and abundance ratios of the four species can not be satisfactorily explained by recent chemical models either among the EGO cloud cores or among the various types of cloud cores from literature.

astro-ph.SR↗