Filaments are ubiquitous structures in molecular clouds and play an important role in the mass assembly of stars. We present results of dynamical stability analyses for filaments in the infrared dark cloud G14.225−0.506, where a delayed onset of massive star formation was reported in the two hubs at the convergence of multiple filaments of parsec length. Full-synthesis imaging is performed with the Atacama Large Millimeter/submillimeter Array (ALMA) to map the N 2 H + (1 − 0) emission in two hub-filament systems with a spatial resolution of ∼ 0.034 pc. Kinematics are derived from sophisticated spectral fitting algorithm that accounts for line blending, large optical depth, and multiple velocity components. We identify five velocity coherent filaments and derive their velocity gradients with principal component analysis. The mass accretion rates along the filaments are up to 10 −4 M yr −1 and are significant enough to affect the hub dynamics within one free-fall time (∼ 10 5 yr). The N 2 H + filaments are in equilibrium with virial parameter α vir ∼ 1.2. We compare α vir measured in the N 2 H + filaments, NH 3 filaments, 870 µm dense clumps, and 3 mm dense cores. The decreasing trend in α vir with decreasing spatial scales persists, suggesting an increasingly important role of gravity at small scales. Meanwhile, α vir also decreases with decreasing non-thermal motions. In combination with the absence of high-mass protostars and massive cores, our results are consistent with the global hierarchical collapse scenario.
The latest generation of Galactic-plane surveys is enhancing our ability to study the effects of galactic environment upon the process of star formation. We present the first data from CO Heterodyne Inner Milky Way Plane Survey 2 (CHIMPS2). CHIMPS2 is a survey that will observe the Inner Galaxy, the Central Molecular Zone (CMZ), and a section of the Outer Galaxy in 12CO, 13CO, and C18O (J = 3 → 2) emission with the Heterodyne Array Receiver Program on the James Clerk Maxwell Telescope (JCMT). The first CHIMPS2 data presented here are a first look towards the CMZ in 12CO J = 3→2 and cover −3○ ≤ ℓ ≤ 5○ and ∣${b}$∣ ≤ 0${_{.}^{\circ}}$5 with angular resolution of 15 arcsec, velocity resolution of 1 km s−1, and rms $\Delta \, T_A ^\ast =$ 0.58 K at these resolutions. Such high-resolution observations of the CMZ will be a valuable data set for future studies, whilst complementing the existing Galactic Plane surveys, such as SEDIGISM, the ${Herschel}$ infrared Galactic Plane Survey, and ATLASGAL. In this paper, we discuss the survey plan, the current observations and data, as well as presenting position-position maps of the region. The position-velocity maps detect foreground spiral arms in both absorption and emission.
Radial colour gradients within galaxies arise from gradients of stellar age, metallicity, and dust reddening. Large samples of colour gradients from wide-area imaging surveys can be used to constrain galaxy formation models. Here we measured colour gradients for low-redshift galaxies using photometry from the 9th DESI Legacy Imaging Survey (LS), which reaches r ∼ 24 over ∼14,000 deg2. We investigate empirical relationships between colour gradients, M*, and sSFR. We compared our results with the prediction of the Illustris TNG-100 simulation using SDSS mock images.
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