We analyze new high-spectral resolution SITELLE observations (R = λ/Δλ = 7000) of the filamentary nebula surrounding NGC 1275, central galaxy of the Perseus cluster. We present here analysis of the λ6716 and λ6731 emission line doublet, using its ratio to determine the electron density of the optically emitting filaments. We compare these measurements with electron densities derived from deep Chandra X-ray observations of the intra-cluster medium (ICM) to determine if any correlations in density can be found. We report the detection of a clear dichotomy between the outer filaments, displaying on average lower emission line ratio of ∼ 1.1 and the inner filaments displaying higher ratios of ∼ 1.3. These results indicate that most of the gaseous filaments lie close to the low-density threshold for the density measurement of ∼ 10^2 cm^-3. Using radial profiles, we find that the inner filaments have a roughly constant density, whereas the ICM density decreases with radius. In the outer filaments, we observe hints of local connections between the densities of the ICM and optical filaments, but no clear correlation seems to be observed overall. We also combined these density measurements with cold molecular CO gas observations to derive a relationship between temperature, density and pressure for the multiphase environment surrounding NGC 1275. Finally, we investigated potential models to explain the observed density measurements and explored similar studies of filamentary nebula around other central galaxies of cool-core galaxy clusters.

We present new Hubble Space Telescope (HST) imaging of ionised filaments in the brightest group galaxy NGC 5044. These filaments extend several kiloparsecs and have widths of ∼50–120 pc, with some as narrow as those in cluster cores and others broader, reflecting the lower confining pressure in groups. Filament width (W) scales with ambient pressure (P) as W ∝ P^-0.4. Combining HST, ALMA, and MUSE data, we measure column densities and magnetic field strengths. Equipartition fields decline from ∼40 μG at the centre to ∼20 μG at 5 kpc, about 2–3 times weaker than in clusters. Dynamical stability requires stronger radial fields (∼10^2 μG), consistent with simulations and magnetic draping, though such high values exceed Faraday Rotation Measure limits. Turbulence and cosmic rays also contribute support. Group and cluster filaments are stable against gravitational collapse, and ultraviolet imaging reveals no star formation in NGC 5044 (<10^-3 M_⊙ yr^-1). NGC 5044 hosts an ionised gas core within its Bondi radius with n_e ∝ r^-1 and filling factor f ≳ 3 × 10^-3, that is connected to the extended filaments, suggesting a channel for gas inflow toward the black hole. Group and cluster filaments likely share a common origin, with magnetic fields and AGN feedback preserving their structure. Ambient pressure and dust survival regulate molecular gas formation. Lower-pressure groups favour broader, more diffuse filaments with sporadic molecular clumps and weaker dust shielding, whereas higher-pressure clusters host narrower strands with stronger molecular-ionised gas alignment. We predict that (i) filament width scales with ambient pressure, (ii) filament-coincident Faraday rotation structures emerge at ≤ 0.1 kpc resolution, and (iii) molecular/ionised gas co-spatiality is weaker in groups than in clusters.

We report the multi-temperature structure of the intracluster medium (ICM) in the Centaurus cluster core observed with XRISM/Resolve. Thanks to its high energy resolution, Resolve enables us to measure fine structures of highly ionized emission lines from Si to Fe and to directly determine the excitation temperature and the ionization temperature from the emission line ratio diagnostics. The observed spectrum in the Centaurus core is well-represented by a double-temperature thermal plasma at collisional ionization equilibrium state rather than an isothermal one. The line ratio diagnostics also support this biphasic temperature structure. Particularly, the observed line ratios show a trend of increasing ionization temperature with atomic mass, while the ionization and excitation temperatures of Fe show nearly the same temperature. The resultant line ratios, which are well-represented by the two temperatures ICM, similar to 1 . 6 and similar to 3 keV, are also fairly consistent with the expected numbers when assuming the radial single-temperature ICM was projected in the cluster core along the line of sight. Due to the limited low-energy sensitivity of the Resolve with the gate valve closed, we investigated the effect of the cool component using the XMM-Newton/RGS spectrum, but it ultimately did not affect our results. The observed flux ratio between the Fe XXV He alpha resonance and forbidden lines shows an about 20% reduction, suggesting the presence of resonant scattering.

The observed deficit of bright late-type giants in the central parsec of the Milky Way remains an open problem. We investigate whether repeated passages of red giants (RGs) through a past jet from SgrA^* can modify their envelopes and apparent spectral types. Three-dimensional hydrodynamical simulations follow a 1 M_⊙, 100 R_⊙ RG through up to ten jet crossings at 10^-3 pc, using jet kinetic luminosities of 10^42, 10^44, and 10^48 erg s^-1. Each passage produces shocks, envelope ablation, and an asymmetric downstream tail. For jet luminosities up to 10^44 erg s^-1, the cumulative ablated mass evolves approximately as ΔM∝ t^1/2 and reaches about 10^-4 M_⊙ over a 10^5 yr active phase. Repeated heating also raises the surface temperature from about 3600 to 8500 K during the first ten passages, potentially making an M-type giant appear as an A-type source. Jet feedback may therefore contribute to the apparent depletion of cool giants and the excess of hot stars in galactic nuclei (GN).

We present extended gas kinematic maps of the Perseus cluster based on a combination of five new XRISM/Resolve pointings observed in 2025 with four performance verification datasets from 2024, totaling a net exposure of 745 ks. To date, Perseus remains the only cluster that has been extensively mapped out to ≃0.7r2500 by XRISM/Resolve, while simultaneously offering sufficient spatial resolution to resolve gaseous substructures driven by mergers and active galactic nucleus (AGN) feedback. Our observations cover multiple radial directions and a broad range of dynamical scales, enabling us to characterize the kinematic properties of the intracluster medium up to a scale of ∼500 kpc. In the measurements, we detected high-velocity dispersions (≃300km s−1) in the eastern region of the cluster that are spatially coincident with the extended X-ray surface brightness excess and correspond to a nonthermal pressure fraction of ≃7 − 13%. The velocity field outside the AGN-dominant region can be effectively described by a single, large-scale kinematic driver based on the velocity structure function, which statistically favors an energy injection scale of at least a few hundred kpc. The estimated turbulent dissipation energy is comparable to the gravitational potential energy released by a recent merger, implying a significant role of turbulent cascade in the merger energy conversion. In the bulk velocity field, we observed a dipole-like pattern along the east-west direction with an amplitude of ≃ ± 200 − 300 km s−1, indicating rotational motions induced by the recent merger event. This feature constrains the viewing direction to ≃30° −50° relative to the normal of the merger plane. Our hydrodynamic simulations suggest that Perseus has experienced at least two energetic mergers since redshift z ∼ 1, the most recent of which is associated with the radio galaxy IC310, in agreement with recent SRG/eROSITA findings. This study showcases exciting scientific opportunities for future missions with high-resolution spectroscopic capabilities (e.g., HUBS, LEM, and NewAthena).

We present new Hubble Space Telescope (HST) imaging of the ionised filaments in the brightest group galaxy NGC 5044, providing the first high-resolution view of such structures in a galaxy group. The filaments extend several kiloparsecs from the centre, with widths of $\sim$ 50-120 pc. Some strands are as narrow as those in cluster cores, while others are broader, consistent with the weaker confining pressure of the intragroup medium. With our limited sample, we find that the filament width (W) roughly scales with ambient pressure (P) as $W \propto P<^>{-0.4}$ . Combining HST with molecular and MUSE observations, we measure column densities and magnetic field strengths. Equipartition magnetic fields decline from $\sim$ 40 $\unicode{x03BC}$ G near the centre to $\sim$ 20 $\unicode{x03BC}$ G at 5 kpc, about 2-3 times weaker than in clusters. Dynamical stability arguments require stronger radial magnetic fields ( $\sim$ 10 $<^>2$ $\unicode{x03BC}$ G), consistent with simulations and magnetic field lines draping and flux freezing around cavities, though such high values may be difficult to reconcile with Faraday Rotation Measure limits. Turbulence and cosmic rays can also provide complementary support. Filaments are stable against gravitational collapse, and ultraviolet imaging reveals no star formation in NGC 5044 ( $\lt$ 10 $<^>{-3}$ M $_\odot$ yr $<^>{-1}$ ), confirming that star formation in filaments in both groups and clusters remains largely quenched. NGC 5044 hosts an ionised gas core within its Bondi radius with $n_e \propto r<^>{-1}$ and filling factor $f \gtrsim 3 \times 10<^>{-3}$ , that is connected to the extended filaments, suggesting a channel for gas inflow toward the black hole. Our results show that group filaments share the same origin and stabilising mechanisms as cluster filaments, with magnetic fields and AGN feedback preserving filamentary structures with ambient pressure and dust survival as key factors for molecular gas formation and survival. Lower pressure groups favour broader, diffuse filaments with sporadic molecular clumps and less dust shielding, while higher pressure clusters host narrower strands with stronger molecular/ionised gas alignment. We predict that (i) filament widths scale with ambient pressure, (ii) filament-coincident Faraday rotation structures should appear at $\leq$ 0.1 kpc resolution, and (iii) molecular/ionised gas co-spatiality is weaker in groups than in clusters.

Recent observations of the transient sky at all wavelengths are increasingly revealing the importance of the multi-messenger and multi-wavelength approach. The GRINTA (Gamma-Ray INternational Transient Array Observatory) mission, proposed for launch around the middle of the next decade, is conceived as a small mission with good sensitivity, excellent angular resolution and fast follow-up capability for studying transient sources at timescales from ms to hours, at the same time ensuring optimal integration with multi-messenger networks. The GRINTA mission will carry two complementary payloads to cover in total the 5 keV-10 MeV band, that will detect and localise gamma-ray bursts covering ∼ half of the sky and will be able to perform imaging surveys with sub-arcmin resolution. GRINTA will operate in synergy with the most powerful electromagnetic, gravitational wave and neutrino observatories foreseen to be operational after 2035.

Context. Via scaling relations, it is well-known that active galactic nuclei (AGN) and bulges are linked. This link was thought to be driven by mergers, but recent studies show that secular processes are the dominant mechanism of supermassive black hole growth. One such secular mechanism is gas inflow driven by large-scale bars. Since bulges can also grow via these bars, there is likely some common process between these three features. Aims. We investigate whether the observed correlation between AGN and bars is real or arises as a result of correlations between bars and bulges. Methods. Using a catalogue of AGN identifications and galaxy morphologies in the DESI Legacy Survey at z≤0.1, we control for mass and colour and investigate the AGN fraction variation with bulge prominence and bar strength. Results. We first show that the variation in AGN fraction between strongly barred, weakly barred and unbarred galaxies does not qualitatively change if we additionally control for bulge prominence. Second, we find that in fixed bins of bulge prominence, the AGN fraction increases with increasing bar strength. In subsamples split by bar strength, the AGN fraction increases with bulge prominence, indicating that AGN presence correlates with both bar strength and bulge prominence simultaneously.

In this work, we report the successful application of silicon photomultipliers (SiPMs) in gamma-ray burst (GRB) detectors used in CubeSats operating in the low Earth orbit (LEO) radiation environment. It is known that SiPMs are susceptible to radiation damage, leading to an increase in the dark count rate. This results in an increase in the low-energy threshold in detectors combining SiPMs and scintillators. Despite this drawback, they became popular in gamma-ray detectors on CubeSats due to their low operating voltage, small size and fast response. Therefore, it is important to characterise their long-term performance in the space environment. Here, we describe the changes in the dark count rate and low-energy threshold of S13360-3050PE multi-pixel photon counters (MPPCs) by Hamamatsu Photonics K.K., using measurements from the GRBAlpha, GRBBeta, and VZLUSAT-2 CubeSats. In the case of GRBAlpha, the measurement of SiPM performance in space lasted over 4 years. GRBAlpha was a 1U CubeSat launched on 2021/03/22 to a 550 km altitude polar orbit carrying a CsI(Tl) scintillator GRB detector employing eight MPPCs and sensitive in the range of 30-900 keV. GRBAlpha de-orbited on 2025/06/09. VZLUSAT-2 was a 3U CubeSat launched on 2022/01/13 to a 535 km altitude polar orbit and de-orbited on 2025/11/30. GRBBeta was launched on 2024/07/09 to a 580 km altitude, 62° inclination orbit. Both VZLUSAT-2 and GRBBeta carry detectors similar to the one on GRBAlpha. We have flight-proven the Hamamatsu MPPCs S13360-3050 PE and demonstrated that SiPMs, shielded by 2.5 mm of PbSb alloy, can be used in a LEO environment on a scientific mission lasting beyond 4 years. This shows the potential for SiPMs to be employed in future satellites.

We present extended gas kinematic maps of the Perseus cluster based on a combination of five new XRISM/Resolve pointings observed in 2025 with four performance verification datasets from 2024, totaling a net exposure of 745 ks. To date, Perseus remains the only cluster that has been extensively mapped out to similar or equal to 0.7r(2500) by XRISM/Resolve, while simultaneously offering sufficient spatial resolution to resolve gaseous substructures driven by mergers and active galactic nucleus (AGN) feedback. Our observations cover multiple radial directions and a broad range of dynamical scales, enabling us to characterize the kinematic properties of the intracluster medium up to a scale of similar to 500 kpc. In the measurements, we detected high-velocity dispersions (similar or equal to 300km s(-1)) in the eastern region of the cluster that are spatially coincident with the extended X-ray surface brightness excess and correspond to a nonthermal pressure fraction of similar or equal to 7 - 13%. The velocity field outside the AGN-dominant region can be effectively described by a single, large-scale kinematic driver based on the velocity structure function, which statistically favors an energy injection scale of at least a few hundred kpc. The estimated turbulent dissipation energy is comparable to the gravitational potential energy released by a recent merger, implying a significant role of turbulent cascade in the merger energy conversion. In the bulk velocity field, we observed a dipole-like pattern along the east-west direction with an amplitude of similar or equal to +/- 200 - 300 km s(-1), indicating rotational motions induced by the recent merger event. This feature constrains the viewing direction to similar or equal to 30 degrees -50 degrees relative to the normal of the merger plane. Our hydrodynamic simulations suggest that Perseus has experienced at least two energetic mergers since redshift z similar to 1, the most recent of which is associated with the radio galaxy IC310, in agreement with recent SRG/eROSITA findings. This study showcases exciting scientific opportunities for future missions with high-resolution spectroscopic capabilities (e.g., HUBS, LEM, and NewAthena).

The recent microcalorimetric X-ray observations of the Coma cluster by XRISM have prompted discussion regarding the physical origin of its gas-velocity features. Here, we demonstrate that an off-axis minor merger in its early phase, when the infalling subhalo is near its primary apocenter and the stripped tail is not yet mixed with the main cluster atmosphere, can drive intracluster gas motions generally consistent with the XRISM results. These include a pronounced velocity gradient and an approximately uniform velocity dispersion of similar or equal to 100 - 200 km s(-1) in the cluster core. This merger scenario was originally proposed to reproduce the major X-ray morphological features of Coma. In addition, we introduce a simple and robust diagnostic of intracluster gas motions based on the ratio of the line-of-sight velocity to the velocity dispersion.

We present deep ALMA Band 7 observations of the $\mathrm{[O\,III]}88\,\mu\mathrm{m}$ line and underlying dust continuum emission in four UV-bright, gravitationally lensed (magnification $\mu = 1.4-3.8$), JWST-selected galaxies at $z = 8.5 - 10.3$, with observed magnitudes $-22.5 \lesssim M_\mathrm{UV} \lesssim -20.5$. $\mathrm{[O\,III]}$ is confidently detected in UNCOVER-10646 at $z=8.5080 \pm 0.0011$ ($15\sigma$) and DHZ1 at $z=9.3113 \pm 0.0006$ ($6\sigma$), with both being intrinsically luminous systems [$L_\mathrm{[O\,III]} = (1.1 - 1.6) \times 10^9\,L_\odot$] that follow the local $\mathrm{[O\,III]}$-SFR relation. $\mathrm{[O\,III]}88\,\mu\mathrm{m}$ remains undetected in the two $z>10$ targets, including in the $z=10.07$ X-ray AGN UHZ1, where we obtain a deep limit of $L_\mathrm{[O\,III]} < 6 \times 10^7\,L_\odot$. Dust emission is not detected in any individual source nor in a stack ($<3\sigma$). The high S/N $\mathrm{[O\,III]}88\,\mu\mathrm{m}$ detection in UNCOVER-10646 uniquely reveals an additional broad component ($\mathrm{FWHM} = 1366_{-329}^{+473}\,\mathrm{km/s}$; $\Delta\mathrm{BIC}\approx20$) indicative of an ionized outflow. We infer a high outflow rate of $\dot{M}_\mathrm{out} = 128_{-46}^{+80}\,M_\odot\,\mathrm{yr}^{-1}$, corresponding to a mass loading factor $\eta = \dot{M}_\mathrm{out}/\mathrm{SFR} = 2.9_{-1.0}^{+1.8}$ that matches or exceeds theoretical predictions and JWST-based studies of ionized outflows at high redshift. While high-resolution ALMA follow-up is required to confirm and spatially resolve the outflow, this first systematic study at $z>8$ highlights the unique diagnostic power of $\mathrm{[O\,III]}88\,\mu\mathrm{m}$ in characterizing galaxies in the early Universe.

Context. Galaxy clusters trace the densest regions of the cosmic web and are crucial laboratories for studying the thermodynamic and chemical evolution of the intracluster medium (ICM). The massive galaxy cluster SPT-CL J0217−5014 ( z ∼ 0.53; M 500 ∼ 3 × 10 14 M ⊙ ) is one of the Swift X-Ray Telescope serendipitous galaxy clusters with the highest reported Fe abundance (∼1.3 ± 0.4 Z ⊙ within ∼ 1 . ′ 7) and a potentially disturbed morphology. Aims. SPT-CL J0217−5014 presents an intriguing opportunity to investigate ICM chemical enrichment and cool-core survival. With this study, we aim to evaluate its chemical and thermodynamic properties with a dedicated Chandra observation. Methods. Using new Chandra observations, we derived surface brightness profiles and dynamical state parameters. We also performed spectral fitting using different backgrounds to constrain the Fe abundance. We performed joint analysis of the X-ray surface brightness, temperature, and integrated Sunyaev-Zel’dovich Compton parameter to constrain the density profile. The DESI optical galaxy cluster catalogue was examined to explore its large-scale environment. Results. The X-ray morphology reveals a disturbed ICM with a surface brightness edge at ∼ 0 . ′ 26 (∼100 kpc) to the west and a tail-like feature extending towards the east. The best-fit metal abundance within $ 1{{\overset{\prime}{.}}}5 $ (∼0.7 R 500 ) is 0.61 +0.26 −0.23 Z ⊙ . The derived central electron number density, entropy, and cooling time classify this system as a non-cool-core cluster, suggesting that merger activity has likely disrupted the possible pre-existing cool core. At larger radii (∼1′−2′), we detected excess X-ray emission to the south spatially aligned with a filamentary distribution of red galaxies, indicating ongoing accretion along an intracluster filament. Based on the DESI DR9 cross-matched optical clusters and photometric redshifts, we identified three nearby lower-mass clusters that likely trace the large-scale structures, suggesting that SPT-CL J0217−5014 is the primary node of a dynamically active environment where past mergers and anisotropic accretion along cosmic filaments have shaped the present-day ICM.

Results from GRBAlpha, VZLUSAT-2 and GRBBeta CubeSats and their on-board gamma-ray detectors for monitoring transients are summarised in this article. GRBAlpha was a 1U CubeSat launched in March 2021 to a 550 km altitude polar orbit carrying a CsI(Tl) scintillator gamma-ray burst (GRB) detector with a sensitive range of approximately 30-900 keV. It successfully operated for over four years until June 2025 when it de-orbited. VZLUSAT-2 was a 3U CubeSat launched in January 2022 to a 535 km altitude polar orbit and de-orbited in November 2025 after almost four years of smooth operation. It carried on board two GRB detectors very similar to the one used on GRBAlpha. Both missions have detected about 360 gamma-ray transients, including over 170 long and short gamma-ray bursts (GRBs), and including the most intense GRB ever recorded GRB 221009A and the second brightest GRB 230307A. The new family member, GRBBeta 2U CubeSat, integrated at Masaryk University, was launched in July 2024 to a 580 km altitude, 62 degree inclination orbit. It has been detecting GRBs since its launch without any trouble. Gamma-ray detectors on these nanosatellites are based on CsI(Tl) scintillator readout by silicon photomultipliers (SiPMs). These missions also provide a unique opportunity to study the radiation damage of SiPMs in the low Earth orbit environment and monitor the radiation belts. We have demonstrated that CubeSats can be used in missions lasting beyond three years and routinely detect GRBs.

We present the largest sample of gamma-ray transients observed by any CubeSat mission so far. Observations were acquired by a 1U CubeSat GRBAlpha, the smallest astrophysical space observatory, and a 3U CubeSat VZLUSAT-2. Both missions were technological pathfinders and carried a novel CsI scintillator-based detector read-out by silicon photomultipliers. They operated on Sun-synchronous low Earth orbits below 550 km for about four years; GRBAlpha between March 2021 and June 2025 while VZLUSAT-2 between January 2022 and November 2025. Despite being technological experiments, they observed over 300 gamma-ray transients including gamma-ray bursts (GRBs), solar flares, soft gamma repeaters and one outburst from an X-ray binary. Among these are the two brightest GRBs ever observed, GRB 221009A and GRB 230307A, without saturation and GRBs at redshifts up to z=4.2. GRBAlpha also contributed to the InterPlanetary Network. Regular monitoring of transients was demonstrated by a detection rate of two transients or one GRB a week and the shortest time between two subsequent detections of only 42 minutes. We show that a constellation of nanosatellites around the Earth would observe at least 60

Pathfinder gamma-ray burst (GRB) detecting CubeSat missions such as GRBAlpha and VZLUSAT-2 have demonstrated the successful application of scintillator detectors with silicon photomultipliers in low Earth orbit (LEO). To produce more comprehensive scientific analysis of the data, the effective area of the detector needs to be characterised at different energies. A large part of this process requires a thorough understanding of the detectors response matrices based on the satellite mass model typically performed through Geant4 and MEGAlib simulations. We use a novel voxelization and binning methodology to turn complex 3D geometries into MEGAlib-compatible versions, and we validate these experiments by showing that the simulation results with Geant4 agree within an order of 10

Astronomy-grade cameras with robust performance and heritage in the space environment have long been costly, substantially limiting capacity for space-based astronomy and creating a resource barrier to access. Additionally, ultraviolet observations have historically been limited by the low quantum efficiency of most sensors in this wavelength range. The LUVCam program is designed to address both issues by providing a high-performance, low-cost, UV/optical camera system sufficiently capable to support a wide-array of space-based astronomy missions. LUVCam features a large format, low-noise, large pixel, and high quantum efficiency, commercial-off-the-shelf back(front)-side illuminated CMOS sensor, packaged with custom built readout electronics, firmware, and thermomechanical structure to provide both superlative science capability and precision on-sensor guidance at fast cadence to allow for stable high-resolution imaging. LUVCam is ITAR-free and cheap to fabricate, opening up new opportunities for access to space telescopes. Here we introduce LUVCam, describe its performance characteristics, and the rapid implementation of a technology demonstration for flight. LUVCam, coupled with a small aperture custom-built UV telescope, has been on orbit since July 2024 and has achieved Technology Readiness Level (TRL) 7. LUVCam is manifested for several more near-term orbital missions, including a second technology demonstration CubeSat for launch in 2026, and will provide both focal plane cameras for QUVIK, a two-channel UV transient astronomy mission.