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1. Large-scale poloidal magnetic field dynamo leads to powerful jets in GRMHD simulations of black hole accretion with toroidal field

   https://doi.org/10.1093/mnras/staa955  

   Liska, M ; Tchekhovskoy, A ; Quataert, E ( May 2020 , Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Accreting black holes (BHs) launch relativistic collimated jets, across many decades in luminosity and mass, suggesting the jet launching mechanism is universal, robust, and scale-free. Theoretical models and general relativistic magnetohydrodynamic (GRMHD) simulations indicate that the key jet-making ingredient is large-scale poloidal magnetic flux. However, its origin is uncertain, and it is unknown if it can be generated in situ or dragged inward from the ambient medium. Here, we use the GPU-accelerated GRMHD code h-amr to study global 3D BH accretion at unusually high resolutions more typical of local shearing box simulations. We demonstrate that turbulence in a radially extended accretion disc can generate large-scale poloidal magnetic flux in situ, even when starting from a purely toroidal magnetic field. The flux accumulates around the BH till it becomes dynamically important, leads to a magnetically arrested disc (MAD), and launches relativistic jets that are more powerful than the accretion flow. The jet power exceeds that of previous GRMHD toroidal field simulations by a factor of 10 000. The jets do not show significant kink or pinch instabilities, accelerate to γ ∼ 10 over three decades in distance, and follow a collimation profile similar to the observed M87 jet.
2. Kinematics around the B335 protostar down to au scales

   https://doi.org/10.1051/0004-6361/201935948  

   Bjerkeli, Per ; Ramsey, Jon P. ; Harsono, Daniel ; Calcutt, Hannah ; Kristensen, Lars E. ; van der Wiel, Matthijs H. ; Jørgensen, Jes K. ; Muller, Sébastien ; Persson, Magnus V. ( November 2019 , Astronomy & Astrophysics)

   Context. The relationship between outflow launching and the formation of accretion disks around young stellar objects is still not entirely understood, which is why spectrally and spatially resolved observations are needed. Recently, the Atacama Large Millimetre/sub-millimetre Array (ALMA) carried out long-baseline observations towards a handful of young sources, revealing connections between outflows and the inner regions of disks. Aims. Here we aim to determine the small-scale kinematical and morphological properties of the outflow from the isolated protostar B335 for which no Keplerian disk has, so far, been observed on scales down to 10 au. Methods. We used ALMA in its longest-baseline configuration to observe emission from CO isotopologues, SiO, SO 2 , and CH 3 OH. The proximity of B335 provides a resolution of ~3 au (0.03′′). We also combined our long-baseline data with archival observations to produce a high-fidelity image covering scales up to 700 au (7′′). Results. 12 CO has an X-shaped morphology with arms ~50 au in width that we associate with the walls of an outflow cavity, similar to what is observed on larger scales. Long-baseline continuum emission is confined to <7 au from the protostar, while short-baseline continuum emission follows the 12 CO outflow andmore »cavity walls. Methanol is detected within ~30 au of the protostar. SiO is also detected in the vicinity of the protostar, but extended along the outflow. Conclusions. The 12 CO outflow does not show any clear signs of rotation at distances ≳30 au from the protostar. SiO traces the protostellar jet on small scales, but without obvious rotation. CH 3 OH and SO 2 trace a region <16 au in diameter, centred on the continuum peak, which is clearly rotating. Using episodic, high-velocity, 12 CO features, we estimate the launching radius of the outflow to be <0.1 au and dynamical timescales of the order of a few years.« less
3. SOLIS: XVI. Mass ejection and time variability in protostellar outflows: Cep E

   https://doi.org/10.1051/0004-6361/202142931  

   de A. Schutzer, A. ; Rivera-Ortiz, P. R. ; Lefloch, B. ; Gusdorf, A. ; Favre, C. ; Segura-Cox, D. ; López-Sepulcre, A. ; Neri, R. ; Ospina-Zamudio, J. ; De Simone, M. ; et al ( June 2022 , Astronomy & Astrophysics)

   Context. Protostellar jets are an important agent of star formation feedback, tightly connected with the mass-accretion process. The history of jet formation and mass ejection provides constraints on the mass accretion history and on the nature of the driving source. Aims. We characterize the time-variability of the mass-ejection phenomena at work in the class 0 protostellar phase in order to better understand the dynamics of the outflowing gas and bring more constraints on the origin of the jet chemical composition and the mass-accretion history. Methods. Using the NOrthern Extended Millimeter Array (NOEMA) interferometer, we have observed the emission of the CO 2–1 and SO N J = 5 4 –4 3 rotational transitions at an angular resolution of 1.0″ (820 au) and 0.4″ (330 au), respectively, toward the intermediate-mass class 0 protostellar system Cep E. Results. The CO high-velocity jet emission reveals a central component of ≤400 au diameter associated with high-velocity molecular knots that is also detected in SO, surrounded by a collimated layer of entrained gas. The gas layer appears to be accelerated along the main axis over a length scale δ 0 ~ 700 au, while its diameter gradually increases up to several 1000 au at 2000more »au from the protostar. The jet is fragmented into 18 knots of mass ~10 −3 M ⊙ , unevenly distributed between the northern and southern lobes, with velocity variations up to 15 km s −1 close to the protostar. This is well below the jet terminal velocities in the northern (+ 65 km s −1 ) and southern (−125 km s −1 ) lobes. The knot interval distribution is approximately bimodal on a timescale of ~50–80 yr, which is close to the jet-driving protostar Cep E-A and ~150–20 yr at larger distances >12″. The mass-loss rates derived from knot masses are steady overall, with values of 2.7 × 10 −5 M ⊙ yr −1 and 8.9 × 10 −6 M ⊙ yr −1 in the northern and southern lobe, respectively. Conclusions. The interaction of the ambient protostellar material with high-velocity knots drives the formation of a molecular layer around the jet. This accounts for the higher mass-loss rate in the northern lobe. The jet dynamics are well accounted for by a simple precession model with a period of 2000 yr and a mass-ejection period of 55 yr.« less
4. Magnetization of Relativistic Current-carrying Jets with Radial Velocity Shear

   https://doi.org/10.3847/1538-4357/ac634a  

   Król, Dominika Ł. ; Stawarz, Łukasz ; Begelman, Mitchell C. ; Martí, José-María ; Perucho, Manel ; Petrenko, Bohdan A. ( April 2022 , The Astrophysical Journal)

   Abstract Astrophysical jets, launched from the immediate vicinity of accreting black holes, carry away large amounts of power in a form of bulk kinetic energy of jet particles and electromagnetic flux. Here we consider a simple analytical model for relativistic jets at larger distances from their launching sites, assuming a cylindrical axisymmetric geometry with a radial velocity shear, and purely toroidal magnetic field. We argue that as long as the jet plasma is in magnetohydrostatic equilibrium, such outflows tend to be particle dominated, i.e., the ratio of the electromagnetic to particle energy flux, integrated over the jet cross-sectional area, is typically below unity, σ < 1. At the same time, for particular magnetic and radial velocity profiles, magnetic pressure may still dominate over particle pressure for certain ranges of the jet radius, i.e., the local jet plasma parameter β pl < 1, and this may be relevant in the context of particle acceleration and production of high-energy emission in such systems. The jet magnetization parameter can be elevated up to the modest values of σ ≲  ( 10 ) only in the case of extreme gradients or discontinuities in the gaseous pressure, and a significantly suppressed velocity shear. Suchmore »configurations, which consist of a narrow, unmagnetized jet spine surrounded by an extended, force-free layer, may require an additional poloidal field component to stabilize them against current-driven oscillations, but even this will not substantially elevate their σ parameter.« less
5. Volcanic and Topographic Evolution of the Sierra San Francisco, Baja California Sur, Mexico

   https://doi.org/10.1130/abs/2022CD-373847  

   HAUSBACK, Brian ; GRANDY, Samuel ; DORSEY, Rebecca J. ; DARIN, Michael ; BENNETT, Scott ( April 2022 , GSA Cordilleran 2022 Meeting)

   The Sierra San Francisco (SSF) is a Neogene volcanic range along the topographic crest of the Baja California peninsula in northern Baja California Sur, Mexico. The SSF is ~55 km long (NW-SE) and ~30 km wide and its highest peaks exceed 1500 m elevation. The SSF has a long history of volcanism and has been eroded by deep, rugged, radially-draining canyons. The development of SSF topography is intimately associated with the volcanic evolution of the range. The SSF is a large and complex dacitic adakite dome complex largely built of a thick, up to 800 m, stratigraphic succession of dacitic tuff breccias with minor interbedded basaltic andesite lavas. These deposits overlie rare exposures of aeolian sandstone of unknown age. The tuff breccias represent block-and-ash-flows and lahars generated from steep-sided peleean dacite and andesite domes, with three radiometric dates of 11-10 Ma. This intermediate sequence is unconformably capped by widespread bajaite mafic lavas, 5.5-4.5 Ma. SSF topography evolved dramatically since the late Miocene: 1) From 11-10 Ma, adakite domes erupted across the central SSF, locally along NNW faults. Thick sequences of bedded tuff breccias accumulated around the domes and are radially inclined away from source domes. The duration of this volcanismmore »is unknown. 2) From 10-5 Ma, deep erosion of the pyroclastic strata formed a range-wide radial drainage network, with channel depths of up to 130 m or more. 3) From 5.5-4.5 Ma, voluminous bajaite lavas from cinder cones and dike vents flooded the top of the range and flowed down the radial drainages with flow distances up to 12 km. Vents are strongly aligned along steep NNW normal faults. 4) After 4.5 Ma, erosion removed interfluves of tuff breccia not armored by younger mafic lavas. Today, the long, steep-sided, lava-capped ridges are inverted topographically. At Santa Martha, an area in the central SSF with the highest concentration of domes, hydrothermal alteration of the volcanic deposits during and after the dome volcanism caused severe material weakening and slope failure within the volcanic center. The area is now a distinctive erosional basin, partly filled with clay-rich landslide deposits. Comparable volcanic history and topographic development are likely to have occurred in a dome field of similar age and size at Santa Agueda, 60 km SE of Santa Martha.« less