Shanghai Astronomical Observatory,Chinese Academy of Sciences
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Disentangling the formation history of galaxies via population-orbit superposition: method validation
No full textWe present population-orbit superposition models for external galaxies based on Schwarzschild's orbit-superposition method, by tagging the orbits with age and metallicity. The models fit the density distributions, kinematic, and age and metallicity maps from integral field unit (IFU) spectroscopy observations. We validate the method and demonstrate its power by applying it to mock data, similar to those obtained by the Multi-Unit Spectroscopic Explorer (MUSE) IFU on the Very Large Telescope (VLT). These mock data are created from Auriga galaxy simulations, viewed at three different inclination angles (theta = 40 degrees, 60 degrees, 80 degrees). Constrained by MUSE-like mock data, our model can recover the galaxy's stellar orbit distribution projected in orbital circularity lambda(z) versus radius r, the intrinsic stellar population distribution in age t versus metallicity Z, and the correlation between orbits' circularity lambda(z) and stellar age t. A physically motivated age-metallicity relation improves the recovering of intrinsic stellar population distributions. We decompose galaxies into cold, warm, and hot+counter-rotating components based on their orbit circularity distribution, and find that the surface density, velocity, velocity dispersion, and age and metallicity maps of each component from our models well reproduce those from simulation, especially for projections close to edge-on. These galaxies exhibit strong global age versus sigma(z) relation, which is well recovered by our model. The method has the power to reveal the detailed build-up of stellar structures in galaxies, and offers a complement to local resolved, and high-redshift studies of galaxy evolution
ALMA Observations Reveal No Preferred Outflow-filament and Outflow-magnetic Field Orientations in Protoclusters
No full textWe present a statistical study of the orientation of outflows with respect to large-scale filaments and magnetic fields. Although filaments are widely observed toward Galactic star-forming regions, the exact role of filaments in star formation is unclear. Studies toward low-mass star-forming regions revealed both preferred and random orientations of outflows with respect to the filament long axes, while outflows in massive star-forming regions are mostly oriented perpendicular to the host filaments and parallel to the magnetic fields at similar physical scales. Here, we explore outflows in a sample of 11 protoclusters in H II regions, a more evolved stage compared to infared dark clouds, using Atacama Large Millimeter/submillimeter Array CO (3-2) line observations. We identify a total of 105 outflow lobes in these protoclusters. Among the 11 targets, 7 are embedded within parsec-scale filamentary structures detected in (CO)-C-13 line and 870 mu m continuum emissions. The angles between outflow axes and corresponding filaments (gamma(Fil)) do not show any hint of preferred orientations (i.e., orthogonal or parallel as inferred in numerical models) with respect to the position angle of the filaments. Identified outflow lobes are also not correlated with the magnetic fields and Galactic plane position angles. Outflows associated with filaments aligned along the large-scale magnetic fields are also randomly oriented. Our study presents the first statistical results of outflow orientation with respect to large-scale filaments and magnetic fields in evolved massive star-forming regions. The random distribution suggests a lack of alignment of outflows with filaments, which may be a result of the evolutionary stage of the clusters
The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333
No full textWe present new observations of the active star formation region NGC 1333 in the Perseus molecular cloud complex from the James Clerk Maxwell TelescopeB-Fields In Star-forming Region Observations (BISTRO) survey with the POL-2 instrument. The BISTRO data cover the entire NGC 1333 complex (similar to 1.5 pc x 2 pc) at 0.02 pc resolution and spatially resolve the polarized emission from individual filamentary structures for the first time. The inferred magnetic field structure is complex as a whole, with each individual filament aligned at different position angles relative to the local field orientation. We combine the BISTRO data with low- and high- resolution data derived from Planck and interferometers to study the multiscale magnetic field structure in this region. The magnetic field morphology drastically changes below a scale of similar to 1 pc and remains continuous from the scales of filaments (similar to 0.1 pc) to that of protostellar envelopes (similar to 0.005 pc or similar to 1000 au). Finally, we construct simple models in which we assume that the magnetic field is always perpendicular to the long axis of the filaments. We demonstrate that the observed variation of the relative orientation between the filament axes and the magnetic field angles are well reproduced by this model, taking into account the projection effects of the magnetic field and filaments relative to the plane of the sky. These projection effects may explain the apparent complexity of the magnetic field structure observed at the resolution of BISTRO data toward the filament network
KiDS-SQuaD. II. Machine learning selection of bright extragalactic objects to search for new gravitationally lensed quasars
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