A Comparison of Paralichthid Flounder Size-Structure in Northwest Florida Based on Trammel Net Catches Adjusted for Mesh Selectivity and Collection by SCUBA Divers

By applying a selectivity model for trammel net catches of Gulf flounder, we found that the resulting adjusted length distribution was similar to the offshore diver-sampled length distribution. We found two dominant size modes that seem to be consistent inshore and offshore, a lower mode composed of males and females and an upper mode composed exclusively of females. Southern flounder demonstrated a lower mode of males and small females but also showed larger females and possibly multiple-size modes after trammel net captures were adjusted for size selectivity. The two species showed very similar values for 91 (91 = 76.2-79.2), a coefficient affecting the mode of the gamma function used for selectivity. Our findings support the idea that the initial approximation of the mesh selectivities may be simple and could be based on parameters determined from related species. Gulf flounder were more abundant in the trammel net catch than were southern flounder, atid Gulf flounder comprised 80% of the net catches but was the only paralichthid flounder we collected offshore. Because southern flounder have been reported offshore from similar depths and habitats along the southeastern U.S. coast, partitioning of spawning habitat may be occurring in our area

The polarized image of a synchrotron-emitting ring of gas orbiting a black hole

High Energy Astrophysic

Constraints on black-hole charges with the 2017 EHT observations of M87*

InstrumentationHigh Energy Astrophysic

The variability of the black hole image in M87 at the dynamical timescale

The black hole images obtained with the Event Horizon Telescope (EHT) are expected to be variable at the dynamical timescale near their horizons. For the black hole at the center of the M87 galaxy, this timescale (5–61 days) is comparable to the 6 day extent of the 2017 EHT observations. Closure phases along baseline triangles are robust interferometric observables that are sensitive to the expected structural changes of the images but are free of station-based atmospheric and instrumental errors. We explored the day-to-day variability in closure-phase measurements on all six linearly independent nontrivial baseline triangles that can be formed from the 2017 observations. We showed that three triangles exhibit very low day-to-day variability, with a dispersion of ∼3°–5°. The only triangles that exhibit substantially higher variability (∼90°–180°) are the ones with baselines that cross the visibility amplitude minima on the u–v plane, as expected from theoretical modeling. We used two sets of general relativistic magnetohydrodynamic simulations to explore the dependence of the predicted variability on various black hole and accretion-flow parameters. We found that changing the magnetic field configuration, electron temperature model, or black hole spin has a marginal effect on the model consistency with the observed level of variability. On the other hand, the most discriminating image characteristic of models is the fractional width of the bright ring of emission. Models that best reproduce the observed small level of variability are characterized by thin ring-like images with structures dominated by gravitational lensing effects and thus least affected by turbulence in the accreting plasmas.https://iopscience.iop.org/article/10.3847/1538-4357/ac332e/pdfPublished versio

Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

InstrumentationLarge scale structure and cosmolog

A universal power-law prescription for variability from synthetic images of black hole accretion flows

Instrumentatio

First sagittarius A* Event Horizon Telescope results. VI. Testing the black hole metric

Galaxie

Millimeter light curves of sagittarius A* observed during the 2017 Event Horizon Telescope campaign

Galaxie

First Sagittarius A* Event Horizon Telescope results. I. The shadow of the supermassive black hole in the center of the Milky Way

Galaxie

First Sagittarius A* event horizon telescope results. II. EHT and multiwavelength observations, data processing, and calibration

Instrumentatio