Volume 3 Issue 1, January 2019

Mitchell C. Begelman, Professor in the Department of Astrophysical and Planetary Sciences at the University of Colorado Boulder and a black hole expert, discusses the start of the field with Nature Astronomy.

Intermediate-mass black holes (BHs) in local dwarf galaxies are considered the relics of the early seed BHs. However, their growth might have been impacted by galaxy mergers and BH feedback so that they cannot be treated as tracers of the early seed BH population.

The detection of a gravitational-wave background at nanohertz frequencies can tell us if and how supermassive black holes merge, and inform our knowledge of galaxy merger rates and supermassive black hole masses. All we have to do is time pulsars.

The masses of supermassive black holes, key to many cosmological studies, are highly uncertain beyond our local Universe. The main challenge is to establish the spatial and kinematic structure of the broad-line emitting gas in active galactic nuclei.

Large cosmological datasets have been probing the properties of our Universe and constraining the parameters of dark matter and dark energy with increasing precision. Deep learning techniques have shown potential to be smarter than — and greatly outperform — human-designed statistics.

The stunning discovery image of the spiral dust plumes enshrouding a Wolf–Rayet binary system dubbed Apep provides new trails of evidence that may bring us closer to resolving outstanding questions on the evolution and death of massive stars.

A model of the optical light detected following the merger of two neutron stars reveals polarization to be a unique probe of the geometry of the kilonova explosion that accompanied the gravitational waves.

An ultrahigh-energy neutrino event detected with the IceCube detector in Antarctica, simultaneous and co-spatial with a multi-wavelength outburst of a blazar about 3 billion light years away, points unambiguously to lepto-hadronic cooling mechanisms in jetted active galactic nuclei.

Examining and comparing many of the definitions of a black hole, it is concluded that the profusion of different definitions is a virtue that makes the investigation of black holes possible and fruitful in many different kinds of problems.

KAGRA is a new gravitational wave detector being built in Japan. Unlike LIGO/Virgo, it will operate at cryogenic temperatures with sapphire mirrors. KAGRA will help improve the localization of gravitational wave detections and determination of the source parameters.

Current black hole spin measurements, in X-rays, radio and gravitational waves, are already constraining models for the growth of black holes, the dynamics of stellar core-collapse and the physics of relativistic jet production.

Supermassive black holes are fed through galaxy interactions and mergers, chaotic cold accretion in galaxy clusters and secular processes that may include stellar bars. Observations constraining these mechanisms at different scales are reviewed.

A network of parallel ridges on the northwestern border of Sputnik Planitia on Pluto are the traces of debris material deposited by a glaciation of icy nitrogen that happened early in Pluto’s history, and left there once the N₂ ice disappeared by sublimation.

Dust accretion onto a white dwarf follows a broken power-law decay, assuming the dust source is mainly delivered via dynamically falling asteroids perturbed by a Jovian planet. Dust disks are present in the early stage of the metal pollution process.

Direct measurement of stellar rotational velocities in a Galactic open star cluster, combined with a simulation, show that rapidly rotating stars can appear redder, thus broadening the main sequence turn-off. Multiple populations of cluster stars are not required to reproduce the observations.

A serpentine plume of dust around a Wolf–Rayet binary indicates the presence of an anisotropic colliding-wind system in which one of the components is likely to be rapidly rotating. Spun-up Wolf–Rayet stars are thought to be long gamma-ray burst sources.

With a lepto-hadronic jet model and recent multi-messenger data, it is shown that a moderate enhancement in cosmic rays during a blazar flare can yield an increased neutrino flux, which is limited by co-produced hard X-rays and TeV gamma rays.

A convolutional neural network estimates cosmological parameters from simulated weak lensing convergence maps in an unbiased way. The network analysis motivates a new and robust convergence peak-counting algorithm based on the steepness of peak heights.

A model of optical polarization provides a framework for studying the composition and dynamical evolution of the ejecta from the kilonova explosion accompanying the gravitational-wave event GW 170817, as well as future kilonovae.

Palomar Gattini-IR is the first of a number of infrared transient surveyors that will search the skies nightly, looking for ephemeral phenomena such as novae, supernovae and neutron star merger events, explain Co-lead Researchers Anna Moore and Mansi Kasliwal.