Measurement of the spin of the M87 black hole from its observed twisted light

ABSTRACT We present the first observational evidence that light propagating near a rotating black hole is twisted in phase and carries orbital angular momentum (OAM). This physical observable allows a direct measurement of the rotation of the black hole. We extracted the OAM spectra from the radio intensity data collected by the Event Horizon Telescope from around the black hole M87* by using wavefront reconstruction and phase recovery techniques and from the visibility amplitude and phase maps. This method is robust and complementary to black hole shadow circularity analyses. It shows that the M87* rotates clockwise with an estimated rotation parameter a = 0.90 ± 0.05 with an $\sim 95{{\ \rm per\ cent}}$ confidence level (c.l.) and an inclination i = 17° ± 2°, equivalent to a magnetic arrested disc with an inclination i = 163° ± 2°. From our analysis, we conclude that, within a 6σ c.l., the M87* is rotating.

Gain stabilization for radio intensity mapping using a continuous-wave reference signal

ABSTRACT Stabilizing the gain of a radio astronomy receiver is of great importance for sensitive radio intensity mapping. In this paper we discuss a stabilization method using a continuous-wave reference signal injected into the signal chain and tracked in a single channel of the spectrometer to correct for the gain variations of the receiver. This method depends on the fact that gain fluctuations of the receiver are strongly correlated across the frequency band, which we can show is the case for our experimental set-up. This method is especially suited for receivers with a digital back-end with high spectral resolution and moderate dynamic range. The sensitivity of the receiver is unaltered except for one lost frequency channel. We present experimental results using a new 4–8.5 GHz receiver with a digital back-end that shows substantial reduction of the 1/f noise and the 1/f knee frequency.

Power spectrum modelling of galaxy and radio intensity maps including observational effects

ABSTRACT Fluctuations in the large-scale structure of the Universe contain significant information about cosmological physics, but are modulated in survey data sets by various observational effects. Building on existing literature, we provide a general treatment of how fluctuation power spectra are modified by a position-dependent selection function, noise, weighting, smoothing, pixelization, and discretization. Our work has relevance for the spatial power spectrum analysis of galaxy surveys with spectroscopic or accurate photometric redshifts, and radio intensity-mapping surveys of the sky brightness temperature including generic noise, telescope beams, and pixelization. We consider the autopower spectrum of a field, the cross-power spectrum between two fields and the multipoles of these power spectra with respect to a curved sky, deriving the corresponding power spectrum models, estimators, errors, and optimal weights. We note that ‘FKP weights’ for individual tracers do not in general provide the optimal weights when measuring the cross-power spectrum. We validate our models using mock data sets drawn fromN-body simulations.1 Our treatment should be useful for modelling and studying cosmological fluctuation fields in observed and simulated data sets.

Probing Radio Intensity at High-Z from Marion: 2017 Instrument

We introduce Probing Radio Intensity at high-Z from Marion (PRIZM), a new experiment designed to measure the globally averaged sky brightness, including the expected redshifted 21[Formula: see text]cm neutral hydrogen absorption feature arising from the formation of the first stars. PRIZM consists of two dual-polarization antennas operating at central frequencies of 70 and 100[Formula: see text]MHz, and the experiment is located on Marion Island in the sub-Antarctic. We describe the initial design and configuration of the PRIZM instrument that was installed in 2017, and we present preliminary data that demonstrate that Marion Island offers an exceptionally clean observing environment, with essentially no visible contamination within the FM band.

High-Accuracy Location Estimation Method Using Public Wireless Networks Based on Radio Intensity Prediction for Logistics Tracking Terminal

For higher positioning accuracy of the low-power-consumption tracking terminal specific to the physical distribution management, a positioning technique using the Personal Handy-phone System (PHS) was developed.