Instrumentation and Methods for Astrophysics
The Chandra-Gaia Catalog of Counterparts: Resolving ambiguous Gaia matches to X-ray sources in the Chandra Source Catalog using Machine Learning
V. Samuel Pérez-Díaz, Vinay L. Kashyap, Joshua D. Ingram et al. (+6 more)
We present a framework to cross-match sources from the Chandra Source Catalog (CSC v2.1) with optical sources from
Gaia Data Release 3. Unlike purely spatial approaches, we use source properties such as magnitudes, colors, and distances to identify true counterparts, detect chance coincidences, and resolve ambiguities when multiple plausible candidates exist. We define a training set of high-confidence matches using NWAY, a
Bayesian cross-matching framework that accounts for positional errors and source densities. We train a gradient-boosted classifier (LightGBM) on a variety of features from both catalogs. Of the ~$254$k unique X-ray sources, we find counterparts for ~$113$k sources, of which plausible multiple counterparts are found for ~$7$k. We find no counterparts for ~$20$k sources for which separation-based cross-matching does find a match, and attribute half of these to chance coincidences. We validate the pipeline on the Chandra Orion Ultradeep Project (COUP), where the machine-learning matches reproduce 95% of NWAY cross-matches without using any positional information. We release a catalog of the ~$113$k Chandra-
Gaia counterparts, together with ~$7$k alternative matches and ~$20$k ambiguous NWAY associations, supporting future population studies of sources detectable by both Chandra and
Gaia. We discuss limitations and provide a generalization of the framework that is applicable in other cross-matching scenarios.
Read the full abstract ▾
All authors V. Samuel Pérez-Díaz, Vinay L. Kashyap, Joshua D. Ingram, David Fouhey, Juan Rafael Martínez-Galarza, Pavlos Protopapas, Jeremy J. Drake, Dong-Woo Kim, Cecilia Garraffo
High Energy Astrophysical Phenomena
GRMHD and GRRT Simulations of Black Hole Accretion: Flares, Precession, and Complex Spacetimes
Hong-Xuan Jiang
This dissertation studies the electromagnetic signatures of accreting supermassive black holes using general relativistic magnetohydrodynamic simulations and covariant radiative-transfer calculations. It develops a unified numerical framework for modeling black-hole
accretion, jet launching, flaring activity, and multi-band variability in Kerr, non-Kerr, and binary black-hole spacetimes. For isolated Kerr black holes, I investigate how
magnetic-field geometry affects
accretion dynamics and transient emission. Multi-loop
magnetic configurations naturally produce reconnection events and flux-rope structures that can power near-infrared
flares from Sagittarius A*, while the evolving optical depth of expanding
plasma explains delayed millimeter emission. I also show that in tilted magnetically arrested disks,
magnetic torques can drive retrograde disk and jet precession. The dissertation then applies the same framework to more complex spacetimes. Simulations of
accretion onto regular loop-
quantum black holes show that
quantum-
gravity corrections can modify
photon-ring size, polarization structure, and jet power, leading to observational constraints from Event Horizon
Telescope data. Finally, simulations of supermassive binary black holes in time-dependent spacetimes reveal how gravitational self-
lensing, shock activity, and
spin-orbit coupling shape multi-wavelength light curves and jet precession. Together, these results connect relativistic
plasma dynamics with current and future observations of black-hole systems.
Read the full abstract ▾
Solar and Stellar Astrophysics
A New Methodology for Classifying Eclipsing Binaries with Kepler Data and Deep Learning
Mousam Mondal, Patricia Cruz, Hugh R. A. Jones et al. (+2 more)
We present a new method for the automated classification of eclipsing binaries, into contact, detached, and semi-detached types using Kepler data. Phase-folded light curves are generated and chi-square vs. box size plots are constructed by comparing flux values to the median flux, revealing distinct class patterns. These patterns were first modelled using a
polynomial damped sinusoidal function, whose period served as classification feature, achieving an overall accuracy of 86.5 percent. To capture more features and enhance accuracy, we trained a convolutional neural network, which improved the total accuracy to 90 percent, including 47 percent for the challenging semi-detached systems. However, several binaries displayed irregular chi-square signatures. To mitigate this, we incorporated simulated light curves generated with the PHOEBE modelling code, achieving 99 per cent accuracy in distinguishing contact and detached binaries. The resulting chi-square morphologies show a strong correlation with orbital period, and a subset of systems exhibit quarterly variability in their light curves and chi-square trends. We designate these as Temporally Varying systems. By measuring the normalized spread of the chi-square period across quarters, we define a statistical threshold that separates these systems from stable binaries. We reported four Temporally Varying systems not previously noted in the literature with
magnetic activity that requires further investigation. Furthermore, cooler
stars, namely late-F, G, K, and M types, display systematically higher variability than hotter
stars. Cross-matching with catalogues of magnetically active
stars indicates that
stellar flares and starspots are the most likely causes of this enhanced variability.
Read the full abstract ▾
All authors Mousam Mondal, Patricia Cruz, Hugh R. A. Jones, M. C. Gálvez-Ortiz, John F. Aguilar
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
A Potential Black Hole Mimicker From Non-Minimal Coupling
Debanjan Debnath, Rikpratik Sengupta and Kaushik Bhattacharya
We present a class of horizonless, regular ultra-compact objects arising in a theory of
gravity that allows
curvature-fluid coupling. The non-minimal interaction between fluid variables and the
Ricci scalar generates a
vacuum-like equation of state in the interior, while the exterior remains exactly Schwarzschild. The two spacetimes are glued through a thin shell at the junction. The interior metric is non-singular, the shell acquires a stiff-matter equation of state, and near-horizon compactness allows the configuration to mimic black-hole phenomenology without an event horizon. For radii in the astrophysically motivated range $5$–$7$ km, imposed as an external input rather than predicted by the theory, the model's mass-compactness relation maps this radius window onto a mass window of $1.4$-$2.1 M_\odot$ for a suitable choice of the
curvature-fluid coupling coefficient. We carry out a detailed stability analysis of the shell in the frozen-bulk approximation, identify the compactness window in which the interior is everywhere regular and the shell is stable, and quantify the accuracy of the frozen-bulk approximation through an explicit adiabaticity parameter. We then develop the surface thermodynamics of the shell assuming a first order phase transition-like origin of the ultra-compact object. This idea then gives rise to shell temperature and radiation, the shell temperature scaling $T_\Sigma \propto M^{-1/2}$ turns out to be a falsifiable predictions of the model.
Read the full abstract ▾
Astrophysics of Galaxies
Direct Tests of Black Hole Accretion Rate Prescriptions: I. Bondi Accretion at Different Scales
James Agostino, Ming-Yi Lin, Natasha Jones et al. (+9 more)
We present spatially resolved parsec-scale measurements of
nuclear conditions (gas density and kinetic temperature) relevant for black hole
accretion rate predictions in the Seyfert 2
galaxy, NGC 1068. We inject these parameters into the prescription for a Bondi-like
accretion model, then compare the resulting
accretion rate prediction to the empirical
accretion rate derived from hard X-ray observations. Cosmological simulations have spatial resolution ranging from $\sim$10 pc to $\sim$kpc scales, and so for reasonable comparison we test these
accretion rate predictions in pixel-sized radial steps out to 500 pc. Compared to warm H$_2$ gas, CO gas is the dominant mass carrier close to the SMBH. We find that the Bondi
accretion rate ($\dot{\mathrm{M}}_{\mathrm{Bondi}}$) of cold molecular gas alone (measured using CO) overestimates the true
accretion rate by up to 14 dex in a small aperture (r$\lesssim$5 pc) around the black hole, and by at least 8 dex inside large apertures (r$\lesssim$500 pc). These results are the first in a series of direct tests of
accretion rate prescriptions, and they suggest that using a Bondi
accretion formalism to model supermassive black hole
accretion in Seyfert 2
galaxies may lead to overestimated
accretion rates in simulations.
Read the full abstract ▾
All authors James Agostino, Ming-Yi Lin, Natasha Jones, Anne M. Medling, Loreto Barcos-Muñoz, Daniel Anglés-Alcázar, Claudio Ricci, George C. Privon, Vivian U, Paul Torrey, Philip F. Hopkins, Claire Max
Astrophysics of Galaxies
The first detection of dense gas in a massive main-sequence galaxy at cosmic noon
Jianhang Chen, Natascha M. Förster Schreiber, Rodrigo Herrera Camus et al. (+18 more)
Dense gas is the direct fuel for
star formation, but measuring it has long been difficult at z>2, especially in typical
star-forming main-sequence
galaxies. In this work, we report the first detection of HNC (J = 5–4) and CN (N = 4–3) emission in a massive main-sequence
galaxy, BX610, at z=2.21. The velocity integrated emission of HNC(5–4)+CN(4–3) is concentrated in the
galactic centre, coincident with the region of ongoing intense
star formation. Based on line decomposition, we measure a line flux ratio HNC(5–4)/CN(4–3) of $1.05\pm0.23$, similar to that of starburst
galaxies at comparable
redshifts but lower than that of
quasar/AGN host
galaxies. The comparatively fainter HNC(5–4) disfavours the presence of a strongly buried AGN in BX610, consistent with optical line diagnostics. The radiative transfer analysis favours the presence of dense gas with a density of $(2-4)\times10^{6}\,\text{cm}^{-3}$ and a kinetic temperature of 50-80 K. The derived abundance ratio between N(HNC) and N(CN) favours dense gas clouds near photodissociation regions, as commonly seen in typical starburst environments. The inferred dense-gas line luminosity closely follows the scaling relation between far-IR and dense-gas line luminosities established for local luminous infrared
galaxies (LIRGs). Our observations support the view that
star formation in
cosmic noon
galaxies is primarily controlled by the availability of dense gas, which could be enhanced in central
galactic regions with efficient cold gas inflows as observed in BX610 along the inner spiral arms and a possible
stellar bar.
Read the full abstract ▾
All authors Jianhang Chen, Natascha M. Förster Schreiber, Rodrigo Herrera Camus, Lilian L. Lee, Minju M. Lee, Claudia Pulsoni, Daizhong Liu, Sebastián Arriagada-Neira, Capucine Barfety, Ric Davies, Frank Eisenhauer, Juan Manuel Espejo Salcedo, Reinhard Genzel, Jean-Baptiste Jolly, Dieter Lutz, Giovanni Mazzolari, Stavros Pastras, Alvio Renzini, Linda Tacconi, Giulia Tozzi, Hannah Übler
High Energy Astrophysical Phenomena
Improved proper motion and gravity tests with PSR J1913+1102
Xueli Miao, Paulo C. C. Freire, Norbert Wex et al. (+11 more)
PSR J1913+1102 is a highly asymmetric double
neutron star system and an excellent laboratory for testing scalar-tensor
gravity theories, as well as a potential progenitor analogue of GW170817 that will merge in 470 Myr. We present an updated timing analysis combining 13 years of historical Arecibo observations and new FAST measurements, using two approaches to model dispersion-measure variations. The new timing solution provides precise measurements of four post-Keplerian parameters and improves the system mass estimates. Assuming general relativity and modelling the DM variation with a Gaussian process, we obtain a three-fold improvement in the total mass, m_{tot}=2.88948(20) M_\odot, and nearly four-fold improvements in the
pulsar and companion masses, m_p=1.599(8) M_\odot and m_c=1.290(8) M_\odot, giving the mass ratio, q=0.807(8). We also measure an improved proper motion, \mu=7.71(25) mas yr^{-1}, enabling a more accurate correction of the observed orbital-period derivative. Combined with the improved orbital-decay measurement, this yields an intrinsic orbital-period derivative \dot{P}_b^{intr}=-4.60(6)\times10^{-13} s s^{-1}, five times more precise than the previous value and fully consistent with the general-relativistic prediction for gravitational-wave damping. The improved masses and precise \dot{P}*b^{intr} place stringent constraints on dipolar gravitational-wave emission and the spontaneous-scalarisation window around 1.6 M*\odot. The refined proper motion and mass measurements also provide tighter constraints on the final helium-
star mass immediately prior to its core collapse and formation of the second NS in a
supernova, as well as on the magnitude and direction of the associated natal kick of the DNS system.
Read the full abstract ▾
All authors Xueli Miao, Paulo C. C. Freire, Norbert Wex, Lingqi Meng, Thomas M. Tauris, Junjie Zhao, Weiwei Zhu, Robert Ferdman, Michael Kramer, Huanchen Hu, Lijing Shao, Yanjun Guo, David J. Champion, Youling Yue
Astrophysics of Galaxies
Ages of the resolved stellar populations inside the JWST/MIRI bubbles in NGC 628
Avinash Ck, Divakara Mayya, Alessandro Bressan et al. (+3 more)
JWST images in the MIRI filters are characterized by prominent interstellar bubbles, most of which are expected to be created by mechanical energy injected into the interstellar medium by dying massive
stars. In this work, we use resolved
stellar populations (RSPs) in JWST/NIRCam images of NGC 628 from the JWST-FEAST
dataset to determine the demography of
stellar populations within these bubbles by comparing them with PARSEC+COLIBRI isochrones using a
Bayesian framework. Our analysis reveals the presence of multiple
stellar populations younger than 100 Myr within the bubbles, suggesting secondary
star formation following the first generation of
stars that formed the bubble. We find a clear preference for the most recently formed
stars to lie closer to the bubble shell. In contrast, relatively older
stars are distributed throughout the bubble interior, consistent with a scenario in which
stars formed in dense shells are left behind as the shell expands. We also examine PHANGS-HST cluster candidates within large bubbles and find no convincing progenitor clusters responsible for the initial trigger, indicating that low-mass clusters or OB associations may be sufficient to drive the initial expansion. However, the cluster may dissolve as it co-evolves with the bubble, producing the dispersed
stellar distributions observed in larger bubbles. We establish a fundamental plane relation for
stellar feedback-driven bubbles that involves the
stellar population mass, age, bubble size, gas density, and feedback efficiency, highlighting the ability of JWST/NIRCam CMDs to characterize
stellar populations driving interstellar bubble expansion in nearby
galaxies
Read the full abstract ▾
All authors Avinash Ck, Divakara Mayya, Alessandro Bressan, Jairo Andres Alzate Trujillo, Léo Girardi, Bolivia Cuevas-Otahola
Solar and Stellar Astrophysics
Multi-Thermal CME Detection with ALMANAC
Thomas Williams, Christopher B. Prior, David MacTaggart et al. (+1 more)
Reliable identification of low-coronal CME origins remains a key limitation in space weather
forecasting with coronagraphs not directly resolving low-coronal signatures. We present a re-engineered multi-thermal implementation of the ALMANAC
algorithm, designed to detect eruptive signatures in EUV observations. The framework extends the method to a multi-wavelength system, improving robustness against projection effects, instrumental artifacts, and wavelength-dependent ambiguities via complementary temperature responses. A spatiotemporal clustering scheme merges detections across channels, reducing event bifurcation and improving coherence while maintaining NRT performance through parallel computing. Benchmarking against 20
halo CMEs from CDAW shows improved interpretability and operational usability, with clearer separation of eruptions and more consistent onset localisation relative to coronagraph estimates. The main benefits arise from improved event discrimination, reduced fragmentation, and more interpretable source region identification. ALMANAC shows sensitivity to precursor low-coronal activity not always captured in white-light catalogues, highlighting its advantages for early warning detection. When coupled with the ARTop framework, it enables co-analysis of coronal intensity variability and photospheric
magnetic evolution. In this context, kurtosis time-series from multi-wavelength EUV data exhibit recurrent pre-eruptive spikes that frequently align with enhancements in
magnetic winding and helicity injection. Across multiple regions, these signatures often precede
solar activity, including potential discrimination of X-class
flares, while remaining suppressed during magnetically quiet intervals. Overall, integrating coronal diagnostics with photospheric
topology offers a pathway toward improved eruption
forecasting and space weather prediction.
Read the full abstract ▾
All authors Thomas Williams, Christopher B. Prior, David MacTaggart, Huw Morgan
Solar and Stellar Astrophysics
Global Multi-ion Solar Wind Model. I. Ion Temperatures
Bart van der Holst, Judit Szente and Enrico Landi
Over the past several decades, observations have shown that minor ions have a higher temperature and flow faster than
protons in the
solar wind. Theories based on
turbulence have been developed that can explain many of these observed phenomena. We present our first step in developing a global multi-ion
solar wind model with
turbulence by including ion temperatures but not yet including differential streaming. The extent of this model is from the lower transition region (50,000 K temperature) to the corona and inner heliosphere. It uses low-frequency, reflection-driven incompressible
turbulence to address coronal heating and
solar wind acceleration. The energy partitioning of the
turbulence dissipation to the electrons and various ions is based on
stochastic heating and linear Landau and transit-time damping. In order to test the validity of our approach we have carried out a three-dimensional simulation of the
solar corona and the
solar wind using an idealized dipole
magnetic field configuration, calculated the Oxygen temperature across the entire domain, and compared it to measurements obtained from the UltraViolet Coronagraph Spectrometer (UVCS) on the
Solar and Heliospheric Observatory (SOHO) satellite and with the
Solar Wind Ion Composition Spectrometer (SWICS) on board Advanced Composition Explorer (ACE). The comparison shows that even with the simplified
magnetic field configuration the multi-ion model predictions reproduce the heavy-ion preferential heating phenomena in both remote-sensing and in-situ observations.
Read the full abstract ▾
Earth and Planetary Astrophysics
JWST-TST High Contrast: First Direct Spectroscopy of GJ 504 b reveals Clouds and Possible Metal Enrichment
Aneesh Baburaj, Jean-Baptiste Ruffio, Marshall Perrin et al. (+27 more)
Characterizing the coldest directly imaged companions through direct spectroscopy has only recently become possible with the James Webb Space
Telescope. We present moderate-resolution (R $\sim$ 2,700) spectroscopic observations of the directly imaged planetary-mass companion (PMC), GJ 504 b, using the $JWST$/NIRSpec. As the coldest imaged PMC of the pre-JWST era GJ 504 b is too faint for ground-based spectroscopy, with only photometric observations possible. Leveraging advanced post-processing techniques with a forward modeling framework, we detect the companion at high signal-to-noise (S/N$>$300). We also present the first successful PSF subtraction with angular differential imaging (ADI) in the NIRSpec point cloud, detecting GJ 504 b at S/N$>10$ and reaching contrast limits $<10^{-4}$. The extracted 2.9–5.3 $\mu m$ spectra show strong signatures of several molecular species, including H$_2$O, $^{12}$C$^{16}$O, CH$_4$, CO$_2$, NH$_3$, H$_2$S, $^{13}$C$^{16}$O, and $^{12}$C$^{18}$O. Atmospheric modeling of the spectra using petitRADTRANS, yields an effective temperature = 564$\pm$4 K, surface
gravity $\log{g}$ = 4.87$^{+0.13}_{-0.12}$,
metallicity [M/H] = 0.67$^{+0.13}_{-0.12}$, C/O ratio = 0.64$^{+0.02}_{-0.02}$, interstellar $^{12}$C/$^{13}$C and $^{16}$O/$^{18}$O isotopologue ratios, and strong evidence of disequilibrium chemistry and salt clouds. The retrieved parameters indicate a mass 25.2$^{+8.4}_{-6.0}$ $M_\mathrm{Jup}$, which is in agreement with the mass range (19–27 $M_\mathrm{Jup}$) obtained from ATMO evolutionary models, implying an age of 2.5–4.0 Gyr. Lastly, we compare the abundances of GJ 504 b to its primary, obtaining a
stellar abundance of sulfur (S), super-
stellar carbon (C), and possibly, oxygen (O). The observed metal enrichment tentatively supports
planet-like formation, but does not entirely exclude
stellar abundances for GJ 504 b.
Read the full abstract ▾
All authors Aneesh Baburaj, Jean-Baptiste Ruffio, Marshall Perrin, Jerry W. Xuan, William O. Balmer, Yayaati Chachan, Quinn M. Konopacky, Travis S. Barman, Mathilde Mâlin, Kielan K. W. Hoch, Emily Rickman, Kimberly Ward-Duong, Laurent Pueyo, Julien H. Girard, Isabel Rebollido, Alexis Bidot, Christine Chen, Kadin Worthen, Cicero Lu, Jens Kammerer, Roeland P. van der Marel, Nikole K. Lewis, Jeff Valenti, Sara Seager, Chris Stark, Rémi Soummer, Jay Anderson, Charles-Philippe Lajoie, Mark Clampin, C. Matt Mountain
Instrumentation and Methods for Astrophysics
Thermal Characterization of a 6-Positioner, 6.2-mm-Pitch Module for Stage-5 Telescopes
Maxime Rombach, Malak Galal, Jonathan Wei et al. (+3 more)
Ensuring thermal stability of robotic fiber positioners is essential for reliable operation in the real environments of Stage-5
telescopes, where temperature variations can influence mechanical behavior and impact fiber-target accuracy. We present the results of thermal qualification tests conducted on 6.2-mm-pitch robotic positioner modules developed for high-density fiber positioning in next-generation astronomical systems. The positioners were characterized at discrete temperatures spanning negative 20 deg C to positive 30 deg C, representative of expected operational conditions. At each temperature point, key performance metrics, positioning repeatability, hard-stop repeatability, backlash, and non-linearity, were measured and compared to nominal performance. Across the full temperature range, the positioners maintained stable behavior with no measurable degradation in any metric and no evidence of mechanical or electrical damage. These results confirm that the 6.2-mm-pitch architecture provides the necessary thermal resilience for deployment in Stage-5
telescope instrumentation.
Read the full abstract ▾
All authors Maxime Rombach, Malak Galal, Jonathan Wei, Stefane Caseiro, Corentin Magnenat, Jean-Paul Kneib
Astrophysics of Galaxies
Solitary dwarf galaxy groups as tracers of dark matter halos in the local Universe
Z. S. Yuan, Z. L. Wen and J. L. Han
In $\Lambda$CDM cosmology,
galaxies and clusters form within dark matter
halos and merge in the hierarchical assembly paradigm to form massive systems. Using the released optical survey data, we searched for groups composed solely of
dwarf galaxies, each with a
stellar mass $M_*<10^{9.5}~M_{\odot}$. We identified 14
dwarf galaxy groups with at least 5
dwarf galaxies, all located within a projected radius of 200 kpc and with a line-of-sight velocity of $\pm$300 km s$^{-1}$. We checked photometric and imaging data and found that these 14
dwarf galaxy groups are solitary, with no neighboring massive
galaxies with $M_*>10^{10}~M_{\odot}$ within 500 kpc and within $\pm$1200 km s$^{-1}$. These
dwarf galaxies are gravitationally bound within
halos with a dynamical mass of around $M_{\rm dyn} \sim 10^{12}~M_{\odot}$ and a virial radius of less than 400 kpc. The
stellar mass fractions of these
dwarf galaxy groups with $M_{\rm dyn}>10^{12}~M_{\odot}$ are one magnitude lower than predicted by the canonical
stellar mass and
halo mass relation. These
dwarf galaxy groups, therefore, are indications of dark matter
halos in the local Universe that host only a few newly formed
dwarf galaxies.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
Guiding Design Choices for Wide-Field IFS: Trade-Offs Between Replication and Complexity for WST
C. Cudennec, A. Jeanneau, R. Bacon et al. (+7 more)
The Wide-field Spectroscopic
Telescope (WST) is a proposed 12-meter segmented facility optimized for seeing- and Ground Layer Adaptive Optics-limited observations in the visible and designed to operate both a high-multiplex multi-object spectrograph and a panoramic integral field spectrograph (IFS). The WST IFS concept builds on instruments such as MUSE at the VLT (Very Large
Telescope), using field splitters and image slicers to reformat a large field into pseudo-slits feeding spectrographs with two optimized spectral channels. This paper presents the integrated design approach adopted for the IFS, focusing on a trade study of spectrograph architectures. We explore design choices such as pixel pitch, detector format, and camera optical design against throughput, image quality, error budgets, volume, cost. The study adds one ecological metric: the carbon footprint of building each spectrograph, to inform design sustainability. The study also explores the potential of curved detectors. Early results suggest that many simpler spectrographs outperform fewer complex units technically and economically.
Read the full abstract ▾
All authors C. Cudennec, A. Jeanneau, R. Bacon, T. Lépine, M. Lehnert, R. Giroud, J-E. Migniau, D. Lee, R. de Jong, L. Fréour
High Energy Astrophysical Phenomena
2D magnetohydrodynamic jet simulations: properties of recollimation shocks
Stella Boula, Fabrizio Tavecchio, Gianluigi Bodo et al. (+2 more)
Recollimation shocks are a frequent outcome in overpressured relativistic jets and are crucial for interpreting stationary features in Active
Galactic Nuclei. The precise influence of
magnetic fields on jet stability, energy dissipation, and variability remains debated, particularly as different field configurations can significantly alter shock properties and the onset of fluid instabilities. We perform a study of 2D axisymmetric RMHD jets to quantify how the ambient density contrast ($\nu$), pressure ratio ($P$), magnetization ($\sigma$), and
magnetic pitch parameter ($\alpha$) govern the formation and strength of the first recollimation shock. We also assess how these parameters create the local
geometric conditions favorable for the centrifugal instability (CFI), utilizing linear theory as a diagnostic. We find that the jet's global geometry is affected by the
magnetic pressure. The recollimation distance decreases monotonically with increasing magnetization $\sigma$, as increased
magnetic forces immediately limit jet expansion. Remarkably, in the magnetically dominated regime, the ratio of the magnetized recollimation distance ($z_{\rm MHD}$) to its purely hydrodynamic counterpart ($z_{\rm HD}$) converges onto a power-law scaling, $z_{MHD}/z_{HD} \propto (B_0^2/P_{ext})^{-1/3}$, where $B_0$ the initial
magnetic field and $P_{ext}$ the external pressure. Jets with high density contrast relative to the ambient medium or high internal pressure further enhance field compression. Furthermore, synthetic synchrotron maps show that a dominant toroidal field yields highly boosted, localized emission
knots, whereas a strong poloidal field creates a diffuse profile and shifts the recollimation zone downstream. Regions susceptible to CFI are determined primarily by the local $\sigma_{\text{tor}}/\Gamma^2$ profile and streamline
curvature created during recollimation.
Read the full abstract ▾
All authors Stella Boula, Fabrizio Tavecchio, Gianluigi Bodo, Nektarios Vlahakis, Paolo Coppi
Solar and Stellar Astrophysics
The formation radius of HCN in O-rich asymptotic giant branch stars
L. Marinho, J. P. Fonfría, M. Agúndez et al. (+3 more)
Molecules detected in circumstellar envelopes around asymptotic
giant branch (AGB)
stars are generally well explained in terms of formation under chemical
equilibrium in the
stellar atmosphere or photochemistry in the outer expanding layers. However, several molecules are detected in the inner circumstellar regions with abundances orders of magnitude above the predictions of chemical
equilibrium. Anomalously abundant molecules comprise H2O, NH3, SiH4, and PH3 in C-rich envelopes and HCN, CS, and NH3 in O-rich sources. These molecules are formed by some yet unknown nonequilibrium processes. Aims: We aim to shed light on the nonequilibrium process that enhances the abundance of anomalously abundant molecules in the inner regions of circumstellar envelopes. Here, we focus on HCN in O-rich
stars to constrain its formation radius. Method: We observed the O-rich AGB
stars RCrt and IKTau with ALMA at high angular resolution (HPBW=~0.05") in the J=4-3 line of HCN in both the ground and the \nu_2=1 vibrational states. The radial distribution of the emission was modeled using a large velocity gradient radiative transfer code in which we considered an abundance profile with a central hole. Results: The models with a hole in the abundance distribution of HCN reproduce the specific shape of the radial emission distribution around the two studied O-rich
stars. The best models locate the formation radius of HCN at 4-6 Rstar in RCrt and 3-5 Rstar in IKTau. Conclusion: The formation radius of HCN inferred from observations is consistent with models that invoke shocked-induced chemistry but also with models where photochemistry acts as the solely disequilibrium process. High angular resolution observations of more O-rich
stars and tailored shocked-induced and/or photochemical models are needed to unambiguously unveil the underlying mechanism behind anomalously abundant molecules in AGB envelopes.
Read the full abstract ▾
All authors L. Marinho, J. P. Fonfría, M. Agúndez, L. Velilla-Prieto, G. Quintana-Lacaci, J. Cernicharo
Instrumentation and Methods for Astrophysics
Comparative Study of Hollow-Core and Standard Optical Fibers for Astronomy
Malak Galal, Oliver Pineda Suárez, Frédéric Gérôme et al. (+3 more)
Efficient light transmission in the blue-visible regime remains a major limitation for fiber-fed astronomical spectrographs, where low
photon flux and the intrinsic attenuation of conventional silica fibers reduce survey sensitivity and depth. Inhibited-coupling hollow-core fibers (IC-HCFs) with reduced surface roughness offer a promising alternative, providing guidance predominantly in air and enabling significantly lower loss across the visible spectrum. In this study, we present a comparative evaluation of IC-HCFs against standard multi-mode fibers used in current astronomical instrumentation. We assess the throughput loss that occurs due to bending, twisting, or pinching of the optical fibers when moved using one of the robotic fiber-positioner prototypes designed for next-generation
telescopes. These measurements quantify the performance gains offered by IC-HCFs for blue-sensitive spectroscopy and assess their suitability for integration into future survey facilities.
Read the full abstract ▾
All authors Malak Galal, Oliver Pineda Suárez, Frédéric Gérôme, Benoit Debord, Fetah Benabid, Jean-Paul Kneib
Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Prospects for Observing Gravity-gradient Noise and Earthquake Gravity Signals with CHRONOS
Mario Juvenal S. Onglao III, Yuki Inoue and Daiki Tanabe
Ground-based gravitational-wave detectors operating in the sub-Hertz regime are expected to be strongly limited by environmental
gravity-gradient fluctuations, commonly referred to as Newtonian Noise (NN). At the same time, this frequency band provides unique opportunities to probe terrestrial gravitational perturbations associated with seismic and atmospheric processes. In this work, we investigate the feasibility of using the proposed Cryogenic sub-Hz cROss torsion-bar detector with
quantum NOn-demolition speed meter (CHRONOS) as a platform for studying
gravity-gradient noise and detecting
prompt gravitational signals from earthquakes. We model
gravity-gradient contributions from Rayleigh-wave-induced seismic fields, atmospheric infrasound fluctuations, and transient mass redistribution during earthquakes, and project these onto the CHRONOS torsion-bar response. CHRONOS achieves a peak strain sensitivity of order ~1e-18 Hz^(-1/2) near ~2 Hz. Rayleigh-wave NN is found to be the dominant environmental contribution below approximately 0.5 Hz, while atmospheric NN remains several orders of magnitude smaller throughout the frequency range considered. We further assess the detectability of
prompt gravitational signals from earthquakes. For a representative Mw = 5.2 event, sources within approximately 90 km may produce detectable signals. At 40 km distance, we obtain a signal-to-noise ratio (SNR) of approximately 3.62 integrated over the sub-Hz band, with a corresponding strain amplitude reaching the CHRONOS sensitivity curve around 0.2 to 0.6 Hz. The gravitational signal is expected to precede seismic P-wave arrival by several seconds, depending on the assumed propagation velocity. These results demonstrate the potential of CHRONOS to probe both
gravity-gradient noise and transient geophysical
gravity signals in the sub-Hertz regime.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
PHANTOM: A MATLAB and Octave Toolbox Connecting Linear Field Statistics to Dark Matter Halo Observables
Mohammad Abu Thaher Chowdhury
We present phantom (Profile and
Halo Analysis for Numerous Theoretical dark Matter Observables), a public MATLAB toolbox and Octave package for calculations that connect the linear density field to dark matter
halo observables. The package combines a flexible cosmology module with linear power spectrum, variance, and correlation function solvers, and a
halo module that covers mass functions, linear bias, density profiles, and concentration-mass relations for cold, warm, and fuzzy dark matter scenarios. All core routines are validated against the Python package colossus, hmf, and halomod, yielding sub-percent agreement for shared models across distances, power spectra, variance, correlation functions,
halo mass functions, and density profiles. Phantom is organised around a cosmology structure that stores background expansion, growth, and linear power-spectrum handles; this object is constructed once and passed through the call graph, so that
halo statistics and
halo structure calculations remain consistent by design. From this single entry point, users can obtain field statistics (power spectrum, variance, correlation function),
halo statistics (mass functions, linear bias), and
halo observables (enclosed mass, circular velocity, projected density, and
lensing convergence) on arbitrary user-defined grids. The toolbox targets users whose analysis pipelines are written in MATLAB or Octave, where a validated native implementation of these models has been absent. The code is released under the MIT licence at phantom(https://github.com/matc-thaher/PHANTOM).
Read the full abstract ▾
Astrophysics of Galaxies
IllustrisTNG50 angular momentum maps: tracing the morpho-kinematic evolution of galaxies
Juan Manuel Pacheco-Arias, Benoît Epinat, Philippe Amram et al. (+2 more)
Following the first observational study of the two-dimensional spatial distribution of
stellar specific angular momentum (sAM) in late-type
galaxies, we quantify the morpho-kinematic diversity of
galaxy simulations using the newly proposed j-types classification. We analyse the
stellar sAM surface density (sAMSD) of $\sim$8000 TNG50
stellar discs spanning $0 \leq z \leq 3.5$ and $9.5 \leq \log(M_\star/\mathrm{M}_\odot) \leq 11.2$, selected from the TNG50 MW/M31 parent sample. We characterize their j-substructures using four morpho-kinematic metrics derived from comparisons with the Freeman sAMSD distribution and the
Fourier decomposition of the
galaxies in the sAMSD space. A Gaussian mixture model with four fully covariant components assigns each
galaxy a probability of belonging to one of four j-types. We find that TNG50 discs exhibit a morpho-kinematic diversity consistent with observations, redistributing
stellar angular momentum through four dominant j-substructures that evolve with
redshift as follows: j-irregulars ($\bar{z}=0.91$), j-spirals ($\bar{z}=0.76$), j-rings ($\bar{z}=0.62$), and j-bars ($\bar{z}=0.39$). The gas fraction and
stellar rotational support ($V/\sigma$) drive this
evolution: gas-rich
galaxies preferentially host j-irregulars and j-spirals, whereas gas-poor systems favour j-rings and j-bars. At fixed gas fraction, higher $V/\sigma$ favours j-spirals and j-rings, respectively. We conclude that there is a canonical pathway for the redistribution of angular momentum within
galactic discs undergoing secular
evolution in TNG50, accessible only through their morpho-kinematic description. The sAMSD analysis links variations in
stellar dynamics to their consequences for mass redistribution, enabling the reconstruction of comprehensive
galactic evolutionary histories.
Read the full abstract ▾
All authors Juan Manuel Pacheco-Arias, Benoît Epinat, Philippe Amram, Wilfried Mercier, Katarina Kraljic
Solar and Stellar Astrophysics
Stellar proper motions compared with the plane-of-sky magnetic field
S.G. Ansari
6 pages, 1 figure, 2 tables. Separates the motions superposed in a young
star's proper motion,
solar reflex,
Galactic rotation, the cloud's own space velocity, subgroup motion and internal flow, and asks which of them a field-
alignment statistic actually measures. v4: adds a frame-independent bound on the
alignment amplitude; adds an independent check of the bulk motion left by the LSR frame against Kounkel et al. (2022) for Orion A North; corrects one reference; journal-neutral formatting.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Resolving the Hubble Tension in the Early Dark Energy Framework with JWST and DESI Data
Guo-Hong Du, Tian-Nuo Li, Lu Yin et al. (+4 more)
In the JWST and DESI era, the JWST high-
redshift galaxy observations and DESI
baryon acoustic oscillation (BAO) measurements severely challenge the standard $\Lambda$CDM model, while the $H_0$ tension becomes increasingly prominent. In this work, we investigate the capability of the early dark energy (EDE) model to alleviate the $H_0$ tension utilizing
cosmic microwave background data from Planck, ACT, and SPT, BAO data from DESI, and ultraviolet luminosity function observations from the JWST. Within the canonical
axion EDE framework, the CMB+DESI+JWST data significantly increase the $H_0$ value to $71.58\pm1.05\,\mathrm{km\,s^{-1}\,Mpc^{-1}}$, alleviating the $H_0$ tension to the $1.0\sigma$ level. Simultaneously, this model improves the fit to the JWST data and exhibits statistical performance significantly better than the $\Lambda$CDM model, with $\Delta\chi^2_{\mathrm{tot}} = -18.26$ and $\Delta\mathrm{DIC} = -11.89$. Our results highlight the complementary advantages of JWST high-
redshift galaxy data alongside early- and late-time observations in testing EDE and alleviating the $H_0$ tension.
Read the full abstract ▾
All authors Guo-Hong Du, Tian-Nuo Li, Lu Yin, Sheng-Han Zhou, Hao Wang, Jing-Fei Zhang, Xin Zhang
Astrophysics of Galaxies
A comparative study of O, Ne, Cl, and Ar in Hii regions and PNe of the Galactic disk: Temporal evolution of radial gradients?
Alexia Amayo, Leticia Carigi, José Eduardo Méndez-Delgado et al. (+2 more)
(Abridged) We compare the radial abundance gradients of O, Ne, Cl, and Ar using a sample of 42 HII regions and 176 planetary nebulae (PNe) from the DESIRED catalogue in the
Galactic disk, comprising the highest-quality observations currently available and presenting the first gradient analysis for this
dataset. For all objects, two sets of chemical abundances were compiled: one derived from collisionally excited lines (CELs) and another incorporating the temperature fluctuation parameter (t^2). Oxygen abundances were corrected for
dust depletion, and HII region results were compared with Cepheid
stars, which trace the present-day interstellar medium. PNe distances were compiled from recent literature, excluding bulge or
halo objects to ensure a disk-only sample. All gradients are statistically significant (p < 0.05), except for Cl and Ar in HII regions. The O/H gradients from HII regions and Cepheids are consistent when t^2 is included, underscoring the importance of accounting for temperature inhomogeneities in nebular analyses. The O and Ne gradients traced by older objects are flatter than the present-day gradient by -0.028 +- 0.008 dex kpc-1 on average from both RLs and CELs. This could indicate a temporal steepening of the
Galactic abundance gradient; however, this behavior is not reproduced by chemical
evolution models, suggesting additional physical processes are at play. The most plausible explanation is that our PNe sample has been strongly affected by radial migration. Under this interpretation, the PNe gradient cannot reliably trace past abundance gradients, but provides a valuable constraint on radial
stellar migration, offering important input for chemo-dynamical models of the
Galactic disk and for hydrodynamical simulations.
Read the full abstract ▾
All authors Alexia Amayo, Leticia Carigi, José Eduardo Méndez-Delgado, Jorge García-Rojas, Elena Reyes-Rodríguez
Earth and Planetary Astrophysics
Three dimensional temporal evolution of photochemical haze in exoplanet atmospheres I. Description and test application to HD 189733b
Elspeth K.H. Lee, Maria E. Steinrueck, Kazumasa Ohno et al. (+2 more)
The formation and global spatial distribution of photochemically produced haze particles remain a key process in
exoplanet atmospheres for understanding their observed properties. We aim to develop a flexible haze particle formation and
evolution model suitable for time-dependent
exoplanet atmosphere simulations. Inspired by recent 2D photochemical modelling efforts, we include a simple activation timescale mechanism to emulate a delayed formation of solid haze particles. We couple our new microphysical haze formation scheme, mini-haze, to the Exo-FMS general circulation model (GCM) and simulate an idealised HD 189733b case study to examine the 3D spatial distribution and sizes of haze particles. Our results suggest that for our chosen haze formation efficiency, particles do not grow beyond $\sim$30 nm, in line with previous detailed 1D modelling. We find the haze spatial distribution follows the vertical velocity structure of the atmosphere, with equatorial convergence patterns of material deeper in the atmosphere at $\sim$10$^{-2}$ bar. The resulting global distribution leads to enhanced haze opacity at the east and west limbs of the atmosphere. In our test cases, radiative feedback from haze opacity can strongly affect the temperature-pressure structures in the upper atmosphere depending on the production rate. Our synthetic spectra results suggest that longer haze-production timescales give rise to stronger haze opacity effects on the observed transmission spectra compared to short-timescale dayside formation, but the stronger thermal feedback from nightside formation leads to an overall larger dayside emission flux. Our current simulations represent a step towards investigating self-consistent haze formation and
evolution with chemical feedback effects in 3D, and can be readily applied to other objects of interest, such as sub-Neptune atmospheres.
Read the full abstract ▾
All authors Elspeth K.H. Lee, Maria E. Steinrueck, Kazumasa Ohno, Diana Powell, Xi Zhang
Earth and Planetary Astrophysics
Interactions of sublimated frost with volcanic plumes: Modelling Io's SO$_2$ atmosphere using the DSMC method
Leander Schlarmann, Audrey Vorburger, Tim Mosimann et al. (+2 more)
Io's tenuous atmosphere consists primarily of sulphur dioxide (SO$_2$) with observed column densities of approximately $10^{16}{-}10^{17}$ cm$^{-2}$. However, it remains uncertain whether the sublimation of SO$_2$ surface frost or volcanic outgassing is the primary source of the SO$_2$ atmosphere. In this study, we produce a 2D model of Io's SO$_2$ atmosphere using the Direct Simulation Monte Carlo (DSMC) method. For this purpose, we conduct a literature review on thermophysical parameters of Io's SO$_2$ surface frost to refine the surface temperature model in accordance with the most recent observations, which enables accurate modelling of Io's sublimated atmosphere. We find that the thermal conductivity, which shifts the peak temperature and SO$_2$ column density away from the subsolar point, has a pronounced effect on sublimation-driven winds and interactions with volcanic plumes. Furthermore, a background atmosphere could reduce sublimation-driven winds in Io's atmosphere, while the SO$_2$ column and number densities are not substantially altered. Moreover, we study the influence of the eclipse, when Io passes through Jupiter's shadow, finding that it reduces the average column density on the sub-Jovian hemisphere by a factor of ${\sim}$5.5 in relation to the anti-Jovian hemisphere. We also investigate the interaction of the sublimated atmosphere with a medium-sized plume at various locations relative to the subsolar point. We find a strong influence, especially on the dayside, where the atmosphere is enhanced with material being displaced by the plume, most pronounced when the plume is positioned near the point of maximum sublimation in the early afternoon.
Read the full abstract ▾
All authors Leander Schlarmann, Audrey Vorburger, Tim Mosimann, Nicolas Thomas, Peter Wurz
Instrumentation and Methods for Astrophysics
Ultra-precise Multi-fiber Optical Connectors for Astronomy
Malak Galal, Maxime Rombach and Jean-Paul Kneib
The increasing sensitivity of modern astronomical instruments requires optical fiber connections with high crossmating stability and insertion loss as low as 1% (0.05 dB). Conventional connectors, though suitable for telecommunications, introduce excess attenuation, Fresnel reflections, and
alignment instabilities that degrade throughput and calibration accuracy in astronomy. This work presents the design and characterization of ultra-low-loss optical multi-fiber connectors developed for astronomical use. Fabricated using femtosecond-
laser 3-D printing, they achieve sub-micron ferrule tolerances. Preliminary metrology shows excellent hole
alignment and roundness, and initial throughput tests for three simultaneously connected fibers show losses as low as 0.95% (0.04 dB). Further throughput and FRD characterization to be implemented to assess efficiency, stability, and repeatability under observatory conditions.
Read the full abstract ▾
Solar and Stellar Astrophysics
A comparative study of solar flux emergence and eruptivity in simulations of horizontal versus toroidal magnetic fields
Vaggelis Karantanis, Juxhin Zhuleku, Vasilis Archontis et al. (+1 more)
Context:
Magnetic flux emergence is a fundamental driver of eruptive activity in the
solar atmosphere. While many numerical studies employed idealized horizontal flux tubes, toroidal tubes provide a more realistic geometry for finite emerging loops with anchored footpoints. Aims: We compare the
evolution and eruptive capability of horizontal and toroidal flux tubes under identical initial parameters. Methods: We performed 3D resistive magnetohydrodynamic (MHD) simulations of the emerging
magnetic flux structures to evaluate their respective dynamics Results: Although the toroidal tube emerges later than in the horizontal case, it produces a higher frequency of eruption-driven jets (four versus two) because the supply of coronal axial flux is sustained. In contrast, the horizontal tube injects
magnetic flux and energy more impulsively, driving stronger but less persistent activity and then rapidly stagnating when its atmospheric axial-flux reservoir is depleted. Free
magnetic energy builds up after emergence and is released in discrete drops associated with eruptions. The toroidal case exhibits a quasi-cyclic buildup and release pattern, whereas the horizontal case relaxes to a lower-activity state after its early eruptions. The temporal
evolution of relative
magnetic helicity mirrors the free-energy
evolution. Helicity increases with the stressing and twisting of the coronal field during emergence, peaks near eruptive episodes, and decreases as eruptions remove twisted flux, with the toroidal tube maintaining a more persistent helicity budget that supports recurrent events. Conclusions: Initial flux-tube geometry strongly controls the coronal flux budget and the storage and release of free energy and helicity, and therefore, the frequency and longevity of eruptive phenomena in emergence-driven active regions.
Read the full abstract ▾
All authors Vaggelis Karantanis, Juxhin Zhuleku, Vasilis Archontis, Kostas Moraitis
Instrumentation and Methods for Astrophysics
Embedding Equity, Diversity, and Inclusion in the WST Collaboration
Laurane Fréour, Anna Puglisi, Maria Cristina Fortuna et al. (+11 more)
The proposed Wide-field Spectroscopic
Telescope (WST) is a next-generation
telescope facility with a 12-meter primary mirror that may be operational in the 2040s. The project has a broad range of scientific goals and engages a large Community of more than 1000 members across multiple time zones, institutions, career stages, and professional roles. As for any large-scale scientific collaboration, building WST is therefore not only a technical and scientific challenge, but also a social and organisational one. This is particularly important in Astronomy and STEM disciplines more broadly, where marginalized groups remain underrepresented, particularly in leadership positions. In this paper, we describe the creation and first year of activity of the WST Equity, Diversity, and Inclusion (EDI) working group. We discuss how the group has worked to embed EDI considerations into the early phases of the Collaboration, and we present our ongoing and future projects aimed at broadening participation, accountability, and community sustainability, while delivering groundbreaking science. We also reflect on the challenges of sustaining EDI work in a large and rapidly evolving collaboration, including recognition of EDI contribution, uneven participation, communication across heterogeneous groups, and the need to connect facility-level initiatives with broader organisational and territorial responsibilities. We present our activities as a situated example of how EDI can be approached as part of the governance, communication, and community infrastructure required to build sustainable research environments.
Read the full abstract ▾
All authors Laurane Fréour, Anna Puglisi, Maria Cristina Fortuna, Fatemeh Zahra Majidi, Umberto Rescigno, Amelia Bayo, Francesca Primas, Sabine Thater, Laurence Tresse, Stephanie Escoffier, Letizia P. Cassarà, Roland Bacon, Sofia Randich, Vincenzo Mainieri
Instrumentation and Methods for Astrophysics
Characterisation of the NewAthena WFI's DEPFET Flight Production's Operational Parameters
Léonie Sommer, Johannes Müller-Seidlitz, Valentin Emberger et al. (+9 more)
NewAthena's Wide Field Imager (WFI) uses detectors made up from Depleted P-Channel Field Effect Transistor (DEPFET) pixels operated in rolling shutter mode. The Large Detector Array (LDA) contains a 2 $\times$ 2 array of 512 $\times$ 512 pixels Large Detectors (LDs) allowing for a field of view of 40' $\times$ 40' with a frame time of 2 ms while the 64 $\times$ 64 pixels Fast Detector (FD) can observe very bright X-ray sources due to a faster frame time of 0.08 ms. Prototype sensors (64 $\times$ 64 pixels) were used to analyse the sensor's operational range and to optimise the ASIC and DEPFET parameters i.e. current and voltage settings, as well as the DEPFET read-out timing parameters, resulting in an improved energy resolution, reduced noise and otherwise improved sensor characteristics.
Read the full abstract ▾
All authors Léonie Sommer, Johannes Müller-Seidlitz, Valentin Emberger, Robert Andritschke, Astrid Mayr, Annika Behrens, Günter Hauser, Peter Lechner, Christian Sandow, Anna Schweingruber, Jonas P. Reiffers, Elif Kutdemir Öncü
Astrophysics of Galaxies
Searching for a superdisk in radio galaxy J0116-473
Ankur Sinha, Riya Rathore, Narendra Nath Patra et al. (+1 more)
Superdisks have emerged as an active area of research in recent years, and J0116-473 represents a promising target for studying this extended structure. Our primary objective was to search for HI absorption associated with the suspected superdisk. However, no such absorption feature was detected, suggesting a low, or absence of neutral hydrogen content in the superdisk. In addition, we examined a compact point source located near the
galaxy's core and the presumed plane of the superdisk, enabling us to search for HI absorption against this background continuum. We also present a detailed multi-band morphological analysis of the
galaxy using
Giant Metrewave
Radio Telescope (GMRT) observations in Bands 3, 4, and 5. A spectral analysis of both the
galaxy and the nearby point source was carried out using data from these three frequency bands. A systematic steepening of the spectral index is observed from the core toward the lobes, as expected for aging synchrotron-emitting
plasma. We also found that the northern inner lobe exhibits a significantly steeper spectrum than its southern counterpart, possibly reflecting environmental effects associated with the proposed superdisk. Since superdisks are expected to contain hot, ionized gas, we additionally examined archival X-ray observations from the XMM-Newton
telescope. Although diffuse X-ray emission associated with the
radio lobes is visible, no significant emission is detected from the region corresponding to the suspected superdisk.
Read the full abstract ▾
All authors Ankur Sinha, Riya Rathore, Narendra Nath Patra, Abhirup Datta