Vol. 707
9. The Sun and the Heliosphere

Three-dimensional mapping of coronal magnetic field and plasma parameters in a solar flare

by Tatyana Kaltman, Sijie Yu, Gregory D. Fleishman, Daniel F. Ryan 2026, A&A, 707, A158

The study presents reconstructed 3D maps of the magnetic field strength, Alfvén speed, and plasma beta in a solar flare volume based on imaging microwave spectroscopy and stereoscopic soft X-ray data. They reveal a magnetically dominated environment. This diagnostic provides important constraints for modeling magnetic reconnection, which drives flare dynamics, and represents a step toward a realistic 3D characterization of energy release in solar energetic phenomena.

Vol. 707
3. Cosmology (including clusters of galaxies)

STRAWBERRY: Finding haloes in the gravitational potential

by Tamara R. G. Richardson, Jens Stücker, Raul E. Angulo 2026, A&A, 707, A117

Numerical simulations of structure formation in a cosmological context provide an ideal testbed for studying galaxy formation and evolution. Typically, underlying dark matter density is simulated by a number of collisionless particles that only abide by the laws of gravitation. One of the first tasks in analyzing simulation output concerns the detection and identification of halos: bound structures at the center of which galaxies are born. This paper presents a novel algorithm (Strawberry) for identifying such structures, while circumventing the problems associated with standard methods such as friends-of-friends or those that impose spherical symmetry. The authors propose using a potential defined in an accelerated frame – the so-called "boosted potential" – that avoids the arbitrary threshold definition and is defined on a given time snapshot. This potential can be adopted to select the contribution of matter distribution over different scales, so that it can be specifically defined on a smaller structure. The methodology provides an interesting separation of halos into a virialized component and a rapidly evolving one. Figure 3 illustrates the particle assignment, which relies on the turnaround boosted potential definition and iteratively adds particles until another potential valley is found. The code is available in a GitHub repository.

Vol. 706
3. Cosmology (including clusters of galaxies)

A sub-ppm upper limit on the cosmological variations of the fine structure constant α

by S. Muller, A. Beelen, M. Guélin, et al. 2026, A&A, 706, A365

Using molecular lines toward two lensed quasars at different, moderate redshifts, the paper presents the most stringent limits to date on the simultaneous variation of the fine structure constant and the proton-to-electron mass ratios for a lookback of about half of the Hubble time comparing two CH transitions and one water one for relative velocity shifts. The two sources are unique in regard to their strength and the observability of the subcomponents; one target was observed at several epochs to constrain possible time variations. A notable feature of the study is the detailed analysis of the contributing uncertainties.

Vol. 706
4. Extragalactic astronomy

Search and analysis of giant radio galaxies with associated nuclei (SAGAN). VI. When jets meet filaments -- Environmental imprints on the growth of giant radio galaxies

by Mousumi Mahato, Elmo Tempel, Shishir Sankhyayan, Pratik Dabhade, Kshitij Chavan 2026, A&A, 706, A310

Galaxy formation relies on a number of factors spanning a wide range of physical scales, from local sites of star formation to large-scale structure. This recent work by Mahato et al. focuses on the connection between the properties of giant radio galaxies (GRGs) and the environments in which they live. The authors make use of previous work that characterized the cosmic web with a catalog of large-scale filaments from SDSS and cross-matched it with a sample of GRGs. Their results reveal an interesting trend in the alignment angle between the radio-detected jets of the GRGs and the closest filament. This angle is found to be larger in GRGs compared to lower-mass radio galaxies, which instead show random alignment. Figures A1-A3 show this behavior in three GRGs. This statistically significant trend suggests environmental coupling, whereby the jets of GRGs propagate along directions preferentially perpendicular to the filament, flowing into lower-density, void-facing regions. Moreover, this result highlights the usefulness of GRGs as tools for analyzing large-scale structure.

Vol. 706
6. Interstellar and circumstellar matter

Interaction of the central jet with the surrounding gas in the protostellar outflow from IRAS 04166+2706

by M. Tafalla, D. Johnstone, J. Santiago-García, Q. Zhang, H. Shang, C.-F. Lee 2026, A&A, 706, A248

How protostellar jets structure and interact with their surroundings is a major challenge for understanding feedback in the star formation process. This study provides an exquisite multimolecular-tracer view of the dynamics in the bipolar outflow of a Class 0 protostar. The jets show two distinct components, distinguished by their velocity intervals: one, below about 25 km/s with a conical, wall-bounded structure, and the other at higher velocities with distinct quasiperiodic arcs and shocks in the inner core indicating a shearing flow within the outer walls. The authors present and model a remarkable set of ALMA CO (2-1) observations, reproducing with pulsed shearing ejections the velocity-position characteristics of both jets. The paper is a harbinger of things to come as more protostellar sources are studied with high-spatial and velocity resolution, showing the wealth of energetic and dynamical information that can be retrieved from spectral line observations.

Vol. 706
5. Galactic structure, stellar clusters and populations

The superclouds of the local Milky Way

by Lilly A. Kormann, João Alves, Michelangelo Pantaleoni González, Cameren Swiggum, Torsten A. Enßlin, Gordian Edenhofer 2026, A&A, 706, A161

Superclouds are the largest structures identified so far in the interstellar medium. With typical sizes of a kiloparsec, superclouds have been identified through HI observations in external galaxies and the inner parts of the Milky Way, but their presence in the solar neighborhood has remained poorly constrained. To remedy this situation, Lilly Kormann and collaborators have investigated the large-scale organization of the local interstellar medium using 3D Gaia-based dust maps and found seven highly elongated and mostly parallel structures in the local 5 kpc^2. These structures resemble superclouds, and nearly all known star-forming regions in the solar neighborhood lie within one of them. This finding supports the idea that superclouds act as gas reservoirs for the formation of giant molecular clouds and therefore regulate cloud formation and star formation on Galactic scales.

Vol. 706
10. Planets, planetary systems, and small bodies

Pre-perihelion evolution of the NiI/FeI abundance ratio in the coma of the interstellar comet 3I/ATLAS: From extreme to normal

by Damien Hutsemékers, Jean Manfroid, Emmanuël Jehin, et al. 2026, A&A, 706, A43

Discovered on July 1, 2025, and with prediscovery observations in June, 3I/Atlas is the third confirmed interstellar object, after asteroid 1I/ʻOumuamua and comet 2I/Borisov. Revealed to be a remarkably active comet immediately after discovery, 3I/Atlas has since been the target of countless photometric and spectroscopic observations from the ground and space, with, for example, JWST data indicating a CO2-dominated and icy-grain-rich coma at 3.3 au from the Sun. Optical/near UV spectroscopy, which mostly samples radicals and atoms, further indicated that 3I/Atlas is a C2-depleted comet, but rich in Ni I, detected as far as 3.88 au pre-perihelion. Based on VLT/UVES and X-SHOOTER data, Hutsemékers et al. here report the first detection of Fe I in 3I/Atlas, as well as the monitoring of the NiI and FeI production rates along its inbound orbit. Compared to Solar-System comets and to 2I/Borisov, 3I/Atlas features an exceptionally high (NiI+FeI) production rate. Most remarkably, the NiI/FeI ratio was initially measured to be very large (~20 at 2.64 au) but became consistent with that found for other C2-depleted comets at distances below 2 au. Ni and Fe in comets have been proposed to originate from the sublimation of carbonyls Ni(CO)4 and Fe(CO)5 and their attendant photodissociation. In this picture, the lower sublimation temperature of Ni(CO)4 versus Fe(CO)5 would explain the preferentially high Ni/Fe ratio at large distances. The scenario could not have been confirmed in Solar-System comets but appears here supported by the 3I/Atlas data. Soon-to-be-expected post-perihelion observations should help clarify the trend with the heliocentric distance, possibly ultimately revealing the intrinsic Ni/Fe ratio in this interstellar visitor.

Vol. 705
4. Extragalactic astronomy

Investigating the growth of little red dot descendants at z<4 with the JWST

by J.-B. Billand, D. Elbaz, F. Gentile, et al. 2026, A&A, 706, A29

One of the "surprises" offered by JWST observations is the discovery of a new type of high redshift (z~6) galaxies termed little red dots (LRDs). They are massive, dense systems that represent an early evolutionary stage in which star formation, dust, and AGN activity produce these intriguing objects with a characteristic V-shaped spectral energy distribution. This paper focuses on potential descendants of LRDs at "lower redshift" (z<~4), exploring the spatial extent of post-LRD candidates from JWST/CEERS. The work involves SED fitting and morphological analysis of a carefully selected sample and suggests an evolutionary scenario requiring growth in the external regions of LRDs. The authors propose three possible channels, as depicted in Fig. 13, with a preference for growth through cold accretion or diffuse inflow.

Vol. 705
2. Astrophysical processes

Fast and "lossless" propagation of relativistic electrons along magnetized nonthermal filaments in galaxy clusters and the Galactic Center region

by Eugene Churazov, Lawrence Rudnick, Ildar Khabibullin, Marisa Brienza, Alex Schekochihin, Dmitri Uzdensky 2026, A&A, 705, A184

This paper addresses a long-standing tension in cluster astrophysics: how relativistic electrons maintain coherence over hundreds of kiloparsecs without extremely fine-tuned reacceleration. It proposes that relativistic electrons are “fast-tracked” along long, low-beta magnetic filaments without strong radiative and adiabatic losses. The paper provides concrete observational tests and unifies multiple environments under a common physical framework. Figure 3 demonstrates how the proposed rapid transport naturally explains the remarkably uniform spectra of extended radio filaments, using the spectral-index gradients along Tail C in Abell 2256 as an illustrative example.