We present the first results of high-spectral resolution (0.023 km s−1) N2H+ observations of dense gas dynamics at core scales (∼0.01 pc) using the recently commissioned Argus instrument on the Green Bank Telescope (GBT). While the fitted linear velocity gradients across the cores measured in our targets nicely agree with the well-known power-law correlation between the specific angular momentum and core size, it is unclear if the observed gradients represent core-scale rotation. In addition, our Argus data reveal detailed and intriguing gas structures in position–velocity (PV) space for all five targets studied in this project, which could suggest that the velocity gradients previously observed in many dense cores actually originate from large-scale turbulence or convergent flow compression instead of rigid-body rotation. We also note that there are targets in this study with their star-forming discs nearly perpendicular to the local velocity gradients, which, assuming the velocity gradient represents the direction of rotation, is opposite to what is described by the classical theory of star formation. This provides important insight on the transport of angular momentum within star-forming cores, which is a critical topic on studying protostellar disc formation.
Hollow-core photonic crystal fibers offer a versatile platform for developing cutting edge optical sensors through particle levitation. Here, the orbital angular momentum mode of such a fiber is utilized to rotate a dielectric nanoparticle, levitated inside the fiber via the gradient force. The rotation frequency, measured from the output intensity modulation caused by the particle rotation, enables sensing of the input power, core pressure, and particle size. Different types of particle dynamics can be obtained by using various orders of angular momentum modes supported by the fiber. At high input power, the system exhibits interesting nonlinear dynamics. Our proposal represents a versatile platform for fiber-based nanoparticle rotation sensing.
more » « less- NSF-PAR ID:
- 10148332
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Journal of the Optical Society of America B
- Volume:
- 37
- Issue:
- 6
- ISSN:
- 0740-3224; JOBPDE
- Page Range / eLocation ID:
- Article No. 1598
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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