Abstracts of Interest
Selected by:
Jemma Pilossof
Abstract: 2501.15902
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Title:Precession for the mode change in a gamma-ray pulsar
View PDF HTML (experimental)Abstract:PSR J2021+4026 is a gamma-ray pulsar having variations in its spin-down rate and gamma-ray flux. Its variations in timing and emission are correlated, e.g., a larger spin-down rate for a low gamma-ray flux. We show that the mode change in PSR J2021+4026 can be understood in the precession scenario. In the precession model, the inclination angle is modulated due to precession. At the same time, the wobble angle may decay with time. This results in damping of the precession. Combined with magnetospheric torque model and the outer gap model, the damped precession can explain: (1) when the inclination angle is larger, the spin-down rate will be larger, accompanied by a lower gamma-ray flux. (2) The variation amplitude of the gamma-ray flux and spin-down rate is smaller than previous results due to the damping of the precession. The modulation period is becoming shorter due to a smaller wobble angle. In the end, we propose that there are two kinds of modulations in pulsars. Long-term modulations in pulsars may be due to precession. Short-term modulations may be of magnetospheric origin.
Abstract: 2501.16058
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Title:The Observed Luminosity Correlations of Gamma-Ray Bursts and Their Applications
View PDF HTML (experimental)Abstract:Gamma-ray bursts (GRBs) are among the most luminous electromagnetic transients in the universe, providing unique insights into extreme astrophysical processes and serving as promising probes for cosmology. Unlike Type Ia supernovae, which have a unified explosion mechanism, GRBs cannot directly act as standard candles for tracing cosmic evolution at high redshifts due to significant uncertainties in their underlying physical origins. Empirical correlations derived from statistical analyses involving various GRB parameters provide valuable information regarding their intrinsic properties. In this brief review, we describe various correlations among GRB parameters involving the prompt and afterglow phases, discussing possible theoretical interpretations behind them. The scarcity of low-redshift GRBs poses a major obstacle to the application of GRB empirical correlations in cosmology, referred to as the circularity problem. We present various efforts aiming at calibrating GRBs to address this challenge and leveraging established empirical correlations to constrain cosmological parameters. The pivotal role of GRB sample quality in advancing cosmological research is underscored. Some correlations that could potentially be utilized as redshift indicators are also introduced.
Abstract: 2501.16097
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Title:Gamma rays from star clusters and implications for the origin of Galactic cosmic rays
View PDF HTML (experimental)Abstract:Context. Star clusters are often invoked as contributors to the flux of Galactic cosmic rays and as sources potentially able to accelerate particles to $\sim$PeV energies. The gamma radiation with $E\gtrsim$ TeV recently observed from selected star clusters has profound implications for the origin of Galactic cosmic rays.
Aims. We show that if the gamma rays observed from the Cygnus cocoon and Westerlund 1 are of hadronic origin, then the cosmic rays escaping the cluster at energies $\gtrsim$ 10 TeV must cross a grammage inside the cluster that exceeds the Galactic grammage. At lower energies, depending on the model adopted to describe the production of gamma rays, such grammage may exceed or be comparable with the grammage inferred from propagation on Galactic scales.
Methods. The flux of gamma rays is analytically computed for a few models of injection of cosmic rays in star clusters, and compared with the flux measured from selected clusters.
Results. In all models considered here, comparing the inferred and observed gamma ray fluxes at $E\gtrsim$ TeV, we conclude that CRs must traverse a large grammage inside or around the cluster before escaping. Clearly these implications would not apply to a scenario in which gamma rays are produced due to radiative losses of leptons in the cluster. Leptonic models typically require weaker magnetic fields, which in turn result in maximum energies of accelerated particles much below $\sim$ PeV.
Conclusions. We conclude that if gamma ray emission in SCs is a generic phenomenon and if this radiation is due to hadronic interactions, either star clusters cannot contribute but a small fraction of the total cosmic ray flux at the Earth, or their contribution to the grammage cannot be neglected and the paradigm of Galactic transport should be profoundly revisited.
Abstract: 2501.16109
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Title:Search for H3 cloudlets in our backyard
View PDF HTML (experimental)Abstract:Several observational lines of evidence imply that a fraction of the dark matter in the Galaxy may be comprised of small cold clouds of molecular hydrogen. Such objects are difficult to detect because of their small size and low temperature, but they can reveal themselves with gamma radiation arising in interactions between such clouds and cosmic rays or as dark shadows cast on the optical, UV and X-ray sky background. In our work we use the data of Fermi LAT 4FGL-DR4 catalogue of gamma-ray sources together with the data of GALEX UV All-Sky Survey to search for small dark clouds of molecular hydrogen in the Solar neighbourhood. This approach allows us to put an upper limit on the local concentration of such objects: $n < 2.2 \times 10^{-11} {\mathrm{AU}^{-3}}$. Constraints (upper limits) on the total amount of matter in this form bound to the Sun strongly depend on the radial profile of the clouds' distribution and reside in $0.05-30~M_{\odot}$ mass range.
Abstract: 2501.16158
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Title:UHECR deflections in the Galactic magnetic field
View PDF HTML (experimental)Abstract:We study the deflections of ultra-high-energy cosmic rays in several widely used models of the coherent Galactic magnetic field (GMF), including PT11 (Pshirkov et al. [1]), JF12 (Jansson and Farrar [2]), UF23 (Unger and Farrar [3]) and KST24 (Korochkin, Semikoz, and Tinyakov [4]). We propagate particles with rigidities of 5, 10, and 20 EV and analyze the differences in deflection predictions across these GMF models. We identify the GMF components responsible for deflections in various regions of the sky and discuss the uncertainties in modeling these components, as well as potential future improvements.
Abstract: 2501.16311
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Title:TiDES: The 4MOST Time Domain Extragalactic Survey
View PDF HTML (experimental)Abstract:The Time Domain Extragalactic Survey (TiDES) conducted on the 4-metre Multi-Object Spectroscopic Telescope (4MOST) will perform spectroscopic follow-up of extragalactic transients discovered in the era of the NSF-DOE Vera C. Rubin Observatory. TiDES will conduct a 5-year survey, covering ${>}14\,000\,\mathrm{square\, degrees}$, and use around 250 000 fibre hours to address three main science goals: (i) spectroscopic observations of ${>}30 000$ live transients, (ii) comprehensive follow-up of ${>}200 000$ host galaxies to obtain redshift measurements, and (iii) repeat spectroscopic observations of Active Galactic Nuclei to enable reverberation mapping studies. The live spectra from TiDES will be used to reveal the diversity and astrophysics of both normal and exotic supernovae across the luminosity-timescale plane. The extensive host-galaxy redshift campaign will allow exploitation of the larger sample of supernovae and improve photometric classification, providing the largest-ever sample of spec-confirmed type Ia supernovae, capable of a sub-2 per cent measurement of the equation-of-state of dark energy. Finally, the TiDES reverberation mapping experiment of 700--1\,000 AGN will complement the SN Ia sample and extend the Hubble diagram to $z\sim2.5$
Abstract: 2501.16440
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Title:Time-Integrated Southern-Sky Neutrino Source Searches with 10 Years of IceCube Starting-Track Events at Energies Down to 1 TeV
View PDF HTML (experimental)Abstract:In the IceCube Neutrino Observatory, a signal of astrophysical neutrinos is obscured by backgrounds from atmospheric neutrinos and muons produced in cosmic-ray interactions. IceCube event selections used to isolate the astrophysical neutrino signal often focus on t/he morphology of the light patterns recorded by the detector. The analyses presented here use the new IceCube Enhanced Starting Track Event Selection (ESTES), which identifies events likely generated by muon neutrino interactions within the detector geometry, focusing on neutrino energies of 1-500 TeV with a median angular resolution of 1.4°. Selecting for starting track events filters out not only the atmospheric-muon background, but also the atmospheric-neutrino background in the southern sky. This improves IceCube's muon neutrino sensitivity to southern-sky neutrino sources, especially for Galactic sources that are not expected to produce a substantial flux of neutrinos above 100 TeV. In this work, the ESTES sample was applied for the first time to searches for astrophysical sources of neutrinos, including a search for diffuse neutrino emission from the Galactic plane. No significant excesses were identified from any of the analyses; however, constraining limits are set on the hadronic emission from TeV gamma-ray Galactic plane objects and models of the diffuse Galactic plane neutrino flux.
Abstract: 2501.16447
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Title:The Role of Pressure in the Structure and Stability of GMCs in the Andromeda Galaxy
View PDF HTML (experimental)Abstract:We revisit the role of pressure in the structure, stability and confinement of Giant Molecular Clouds (GMCs) in light of recently published observations and analysis of the GMCs in the Andromeda galaxy (M31). That analysis showed, that in the absence of any external pressure, most GMCs (57\% by number) in M31 would be gravitationally unbound. Here, after a more detailed examination of the global measurements of surface densities and velocity dispersions, we find that GMCs in M31, when they can be traced to their outermost boundaries, require external pressures for confinement that are consistent with estimates for the mid-plane pressure of this galaxy. We introduce and apply a novel methodology to measure the radial profile of internal pressure within any GMC that is spatially resolved by the CO observations. We show that for the best resolved examples in M31 the internal pressures increase steeply with surface density in a power-law fashion with $p_{int} \sim \Sigma^2$. At high surface densities many of these extragalactic GMCs break from the single power-law and exhibit upward curvature. Both these characteristics of the variation of internal pressure with surface density are in agreement with theoretical expectations for hydrostatic equilibrium at each radial surface of a GMC, including the outermost boundary.
Abstract: 2501.16474
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Title:Differential virial analysis: a new technique to determine the dynamical state of molecular clouds
View PDF HTML (experimental)Abstract:Since molecular clouds form stars, at least some parts of them must be in a state of collapse. However, there is a long-standing debate as to whether that collapse is local, involving only a small fraction of the cloud mass, or global, with most mass in a state of collapse up to the moment when it is dispersed by stellar feedback. In principle it is possible to distinguish these possibilities from clouds' virial ratios, which should be a factor of two larger for collapse than for equilibrium, but systematic uncertainties have thus far prevented such measurements. Here we propose a new analysis method to overcome this limitation: while the absolute value of a cloud's virial ratio is too uncertain to distinguish global from local collapse, the differential change in virial ratio as a function of surface density is also diagnostic of clouds' dynamical state, and can be measured with far fewer systematic uncertainties. We demonstrate the basic principles of the method using simple analytic models of supported and collapsing clouds, validate it from full 3D simulations, and discuss possible challenges in applying the method to real data. We then provide a preliminary application of the technique to recent observations of the molecular clouds in Andromeda, showing that most of them are inconsistent with being in a state of global collapse.
Abstract: 2501.16881
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Title:Influence of the Galactic Halo on the UHECR Multipoles
View PDF HTML (experimental)Abstract:We examine the effects of a giant magnetized halo around the Galaxy on the angular distribution of the arriving ultra-high energy cosmic rays (UHECR) observed at Earth. We investigate three injection scenarios for UHECRs, and track them through isotropic turbulent magnetic fields of varying strengths in the Galactic halo. We calculate the resultant dipole and quadrupole amplitudes for the arriving UHECRs detected by an observer in the Galactic plane region. We find that, regardless of the injection scenario considered, when the scattering length of the particles is comparable to the size of the halo, the UHECRs skymap resembles a dipole. However, as the scattering length is increased, the dipolar moment always increases, and the quadrupolar moment increases rapidly for two of the three cases considered. Additionally, the quadrupole amplitude is highlighted to be a key discriminator in discerning the origin of the observed dipole. We conclude that, to understand the origin of the UHECR dipole, one has to measure the strength of the quadrupole amplitude as well.
Abstract: 2501.16967
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Title:Uncertainties in astrophysical gamma-ray and neutrino fluxes from proton-proton cross-sections in the GeV to PeV range
View PDF HTML (experimental)Abstract:The identification of Cosmic Ray (CR) sources represents one of the biggest and long-standing questions in astrophysics. Direct measurements of cosmic rays cannot provide directional information due to their deflection in (extra)galactic magnetic fields. Cosmic-ray interactions at the sources lead to the production of high-energy gamma rays and neutrinos, which, combined in the multimessenger picture, are the key to identifying the origins of CRs and estimating transport properties. While gamma-ray observations alone raise the question of whether their origin is hadronic or leptonic, the observation of high-energy neutrino emission directly points to the presence of CR hadrons. To identify the emission signatures from acceleration and transport effects a proper modeling of those interactions in a transport framework is needed. Significant work has been done to tune the production cross sections to accelerator data and different models exist that put the exact evolution of the Monte-Carlo generated showers into a statistical approach of a probabilistic description of the production of the final states of the showers relevant for astrophysical observations.
In this work, we present the implementation of different hadronic interaction (HI) models into the publicly available transport code CRPropa. We apply different descriptions of the HI, trained on observational data in different energy regimes to a nearby, giant molecular cloud. In this case, the resulting gamma-ray flux can differ by a factor $\sim 2$ dependent on the choice of the HI model.
Abstract: 2501.17041
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Title:Benchmarking Quantum Convolutional Neural Networks for Signal Classification in Simulated Gamma-Ray Burst Detection
View PDF HTML (experimental)Abstract:This study evaluates the use of Quantum Convolutional Neural Networks (QCNNs) for identifying signals resembling Gamma-Ray Bursts (GRBs) within simulated astrophysical datasets in the form of light curves. The task addressed here focuses on distinguishing GRB-like signals from background noise in simulated Cherenkov Telescope Array Observatory (CTAO) data, the next-generation astrophysical observatory for very high-energy gamma-ray science. QCNNs, a quantum counterpart of classical Convolutional Neural Networks (CNNs), leverage quantum principles to process and analyze high-dimensional data efficiently. We implemented a hybrid quantum-classical machine learning technique using the Qiskit framework, with the QCNNs trained on a quantum simulator. Several QCNN architectures were tested, employing different encoding methods such as Data Reuploading and Amplitude encoding. Key findings include that QCNNs achieved accuracy comparable to classical CNNs, often surpassing 90\%, while using fewer parameters, potentially leading to more efficient models in terms of computational resources. A benchmark study further examined how hyperparameters like the number of qubits and encoding methods affected performance, with more qubits and advanced encoding methods generally enhancing accuracy but increasing complexity. QCNNs showed robust performance on time-series datasets, successfully detecting GRB signals with high precision. The research is a pioneering effort in applying QCNNs to astrophysics, offering insights into their potential and limitations. This work sets the stage for future investigations to fully realize the advantages of QCNNs in astrophysical data analysis.
Abstract: 2501.17321
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Title:The highest energy cosmic rays from superheavy dark matter particles
View PDF HTML (experimental)Abstract:It is commonly accepted that high energy cosmic rays up to $10^{19}$ eV can be produced in catastrophic astrophysical processes. However the source of a few observed events with higher energies remains mysterious. We propose that they may originate from decay or annihilation of ultra heavy particles of dark matter. Such particles naturally appear in some models of modified gravity related to Starobinsky inflation.
Abstract: 2501.17467
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Title:Multi-messenger Emission by Magnetically Arrested Disks and Relativistic Jets of Black Hole X-ray Binaries
View PDF HTML (experimental)Abstract:Black hole X-ray binaries (BHXBs) are observed in various wavelengths from radio to GeV gamma-ray. Several BHXBs, including MAXI J1820+070 and Cygnus X-1, are also found to emit ultrahigh-energy (UHE; photon energy $>$100 TeV) gamma rays. The origin and production mechanism of the multi-wavelength emission of BHXBs are under debate. We propose a scenario where relativistic particles from magnetically arrested disks (MADs), which could form when BHXBs are in quiescent or hard states, produce UHE gamma rays, while electrons in the jets produce GeV gamma-ray emission. Specifically, magnetic turbulence in MADs heats up and accelerates electrons and protons, while magnetic reconnection in jets accelerates electrons. Sub-PeV gamma rays and neutrinos are produced when relativistic protons interact with the thermal protons and the radiation by thermal electrons in the disk. We discuss the perspectives of observing sub-PeV multi-messenger signals from individual BHXBs. Finally, we evaluate the integrated fluxes of the quiescent and hard-state BHXB population and find that BHXBs may contribute to the Galactic diffuse emission above $\sim 100$ TeV.
Abstract: 2501.17537
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Title:Neural Networks for the Analysis of Traced Particles in Kinetic Plasma Simulations
View PDF HTML (experimental)Abstract:Cosmic-ray acceleration processes in astrophysical plasmas are often investigated with fully-kinetic or hybrid kinetic numerical simulations, which enable us to describe a detailed microphysics of particle energization mechanisms. Tracing of individual particles in such simulations is especially useful in this regard. However, visually inspecting particle trajectories introduces a significant amount of bias and uncertainty, making it challenging to pinpoint specific acceleration mechanisms. Here, we present a novel approach utilising neural networks to assist in the analysis of individual particle data. We demonstrate the effectiveness of this approach using the dataset from our recent particle-in-cell (PIC) simulations of non-relativistic perpendicular shocks that consists of 252,000 electrons, each characterised by their position, momentum and electromagnetic field at particle's position, recorded in a time series of 1200 time steps. These electrons cross a region affected by the electrostatic Buneman instability, and a small percentage of them attain high energies. We perform classification, regression, and anomaly detection algorithms on the dataset by using a convolutional neural network, a multi-layer perceptron, and an autoencoder. Despite the noisy and imbalanced dataset, all methods demonstrate the capability to differentiate between thermal and accelerated electrons with remarkable accuracy. The proposed methodology may considerably simplify particle classification in large-scale PIC and hybrid simulations.
Abstract: 2501.16908
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Title:Impact of light sterile neutrinos on cosmological large scale structure
View PDF HTML (experimental)Abstract:Sterile neutrinos with masses on the $\mathrm{eV}$ scale are promising candidates to account for the origin of neutrino mass and the reactor neutrino anomalies. The mixing between sterile and active neutrinos in the early universe could result in a large abundance of relic sterile neutrinos, which depends on not only their physical mass $m_{\rm phy}$ but also their degree of thermalization, characterized by the extra effective number of relativistic degrees of freedom $\Delta N_{\rm eff}$. Using neutrino-involved N-body simulations, we investigate the effects of sterile neutrinos on the matter power spectrum, halo pairwise velocity, and halo mass and velocity functions. We find that the presence of sterile neutrinos suppress the matter power spectrum and halo mass and velocity functions, but enhance the halo pairwise velocity. We also provide fitting formulae to quantify these effects.
Abstract: 2501.18678
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Title:CRexit: how different cosmic ray transport modes affect thermal instability in the circumgalactic medium
View PDF HTML (experimental)Abstract:The circumgalactic medium (CGM) plays a critical role in galaxy evolution, influencing gas flows, feedback processes, and galactic dynamics. Observations show a substantial cold gas reservoir in the CGM, but the mechanisms driving its formation and evolution remain unclear. Cosmic rays (CRs), as a source of non-thermal pressure, are increasingly recognized as key regulators of cold gas dynamics. This study explores how CRs affect cold clouds that condense from the hot CGM via thermal instability (TI). Using 3D CR-magnetohydrodynamic (CRMHD) simulations with AREPO, we assess the impact of various CR transport models on cold gas evolution. Under purely advective CR transport, CR pressure significantly suppresses the collapse of thermally unstable regions, altering the CGM's structure. In contrast, realistic CR transport models reveal that CRs escape collapsing regions via streaming and diffusion along magnetic fields, diminishing their influence on the thermal and dynamic structure of the cold CGM. The ratio of the CR escape time to the cloud collapse time emerges as a critical factor in determining the impact of CRs on TI. CRs remain confined within cold clouds when effective CR diffusion is slow which maximizes their pressure support and inhibits collapse. Fast effective CR diffusion, as realized in our 2-moment CRMHD model, facilitates rapid CR escape, reducing their stabilizing effect. This realistic CR transport model shows a wide dynamic range of the effective CR diffusion coefficient, ranging from $10^{29}$ to $10^{30}\,\mathrm{cm^{2}\,s^{-1}}$ for thermally- to CR-dominated atmospheres, respectively. In addition to these CR transport-related effects, we demonstrate that high numerical resolution is crucial to avoid spuriously large clouds formed in low-resolution simulations, which would result in overly long CR escape times and artificially amplified CR pressure support.
Abstract: 2501.18696
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Title:Cosmic Rays Masquerading as Hot CGM Gas: An Inverse-Compton Origin for Diffuse X-ray Emission in the Circumgalactic Medium
View PDF HTML (experimental)Abstract:Observations have argued that Milky Way (MW), Andromeda, and lower-mass galaxies exhibit extended soft X-ray diffuse halos to radii $R\gtrsim100\,$kpc in the circumgalactic medium (CGM). If interpreted as thermal emission, the shallow surface brightness profiles $S_{X}\propto R^{-1}$ are difficult to explain and contradict other observations. We show that such halos instead arise from inverse Compton (IC) scattering of CMB photons with GeV cosmic ray (CR) electrons. GeV electrons have ~Gyr lifetimes and escape the galaxy, forming a shallow extended profile out to $\gtrsim100\,$kpc, where IC off the CMB should produce soft, thermal-like X-ray spectra peaked at ~keV. The observed keV halo luminosities and brightness profiles agree well with those expected for CRs observed in the local interstellar medium (LISM) escaping the galaxy, with energetics consistent with known CRs from SNe and/or AGN, around galaxies with stellar masses $M_{\ast}\lesssim2\times 10^{11}\,M_{\odot}$. At higher masses observed X-ray luminosities are larger than predicted from IC and should be dominated by hot gas. In the MW+M31, the same models of escaping CRs reproduce gamma-ray observations if we assume an LISM-like proton-to-electron ratio and CR-pressure-dominated halo. In all other halos, the radio and $\gamma$-ray brightness is below detectable limits. If true, the observations provide qualitatively new constraints on CGM and CR physics: X-ray brightness directly traces the CR lepton energy density in the CGM. This agrees with LISM values within 10 kpc, which following the profile expected for escaping CRs in the CGM. The inferred CR pressure is a major part of the MW CGM pressure budget. X-ray surface brightness and luminosity allows one to further determine the CGM diffusivity at radii $\sim10-1000\,$kpc. These also agree with LISM values at small radii but increase in the CGM.
Abstract: 2501.18713
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Title:Tidal disruption events as origin of the eROSITA and Fermi bubbles
View PDF HTML (experimental)Abstract:Context: The recently discovered spherical eROSITA bubbles arise up to a latitude of $\pm$80°-85°in the X-ray regime of the Milky Way halo. Similar to the $\gamma$-ray Fermi bubbles, they evolve around the Galactic center, making a common origin plausible. However, the driving mechanism and evolution of both bubbles are still under debate. Aims: We want to investigate whether hydrodynamic energy injections at the Galactic center, such as e.g. tidal disruption events (TDEs), could have inflated both bubbles. The supermassive black hole Sagittarius A* is expected to tidally disrupt a star every 10-100 kyr, potentially leading to an outflow from the central region that drives a shock propagating into the Galactic halo due to its vertically declining density distribution, ultimately forming a superbubble blown out of the disk similar to the eROSITA and Fermi bubbles. Methods: We model TDEs in the Galaxy using three-dimensional hydrodynamical simulations, considering different Milky Way mass models and TDE rates. We then generate synthetic X-ray maps and compare them to observations. Results: Our simulation results of a $\beta$-model Milky Way halo show that superbubbles, blown for 16 Myr by regular energy injections at the Galactic center that occur every 100 kyr, can have a shape, shell stability, size, and evolution time similar to estimates for the eROSITA bubbles, and an overall structure reminiscent to the Fermi bubbles. The $\gamma$-rays in our model would stem from cosmic ray interactions at the contact discontinuity, where they were previously accelerated by first order Fermi acceleration at in situ shocks. Conclusions: Regular TDEs in the past 10-20 Myr near the Galactic center could have driven an outflow resulting in both, the X-ray emission of the eROSITA bubbles and the $\gamma$-ray emission of the Fermi bubbles.
Abstract: 2501.17239
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Title:The impact of cosmic ray feedback during the epoch of reionisation
View PDF HTML (experimental)Abstract:Galaxies form and evolve via a multitude of complex physics. In this work, we investigate the role of cosmic ray (CR) feedback in galaxy evolution and reionisation, by examining its impact on the escape of ionising radiation from galaxies. For this purpose, we present two Sphinx cosmological radiation-magneto-hydrodynamics simulations, allowing for the first time a study of the impact of CR feedback on thousands of resolved galaxies during the Epoch of Reionisation (EoR). The simulations differ in their feedback prescriptions: one adopts a calibrated strong supernova (SN) feedback, while the other simulation reduces the strength of SN feedback and includes CR feedback instead. We show that both comparably regulate star formation, reasonably match observations of high-redshift UV luminosity functions, and produce a similar amount of hydrogen ionising photons. In contrast to the model with strong SN feedback, the model with CRs lead to incomplete reionisation, which is in strong disagreement with observational estimates of the reionisation history. This is due to CR feedback shaping the ISM differently, filling with gas the low density cavities otherwise carved by SN explosions. As a result, this reduces the escape of ionising photons, at any halo mass, and primarily in the close vicinity of the stars. Our study indicates that CR feedback regulates galaxy growth during the EoR, but negatively affects reionisation, a tension which paves the way for further exploration and refinement of existing galaxy formation and feedback models. Such improvements are crucial in order to capture and understand the process of reionisation and the underlying evolution of galaxies through cosmic time.
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