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There are two contradictory views of the eROSITA bubbles: either a 104 pc scale pair of giant bubbles blown by the Galactic center (GC), or a 102 pc scale local structure coincidentally located in the direction of GC. A key element of this controversy is the distance to the bubbles. Based on the 3D dust distribution in the Galactic plane, we found three isolated, distant (500–800 pc) clouds at intermediate Galactic latitudes. Their projected morphologies perfectly match the X-ray shadows on the defining features of the north eROSITA bubble, i.e., the North Polar Spur (NPS) and the Lotus Petal Cloud (LPC), indicating that both the NPS and LPC are distant, with a distance lower limit of nearly 1 kpc. In the X-ray-dark region between the NPS and LPC, we found a few polarized radio arcs and attributed them to the bubble’s shock front. These arcs match up perfectly with the outer border of the NPS and LPC and provide a way to define the bubble’s border. The border defined in this way can be well described by the line-of-sight tangent of a 3D skewed cup model rooted in the GC. We conclude that, instead of being two independent, distant features, the NPS and LPC compose a single, giant bubble, which therefore is most plausibly a 10 kpc scale bubble rooted at the GC.

We address the nature and origin of a spiral disk at the center of NGC 1275, the giant elliptical galaxy at the center of the Perseus cluster, that spans a radius of ∼5 kpc. By comparing stellar absorption lines measured in long-slit optical spectra with synthetic spectra for single stellar populations, we find that fitting of these lines requires two stellar populations: (i) a very young population that peaks in radial velocity at ±250 km s−1 of the systemic velocity within a radius of ∼720 pc of the nucleus, a 1σ velocity dispersion significantly lower than 140 km s−1, and an age of 0.15 ± 0.05 Gyr; and (ii) a very old population having a constant radial velocity with a radius corresponding to the systemic velocity, a much broader velocity dispersion of ∼250 km s−1, and an age of around 10 Gyr. We attribute the former to a post-starburst population associated with the spiral disk, and the latter to the main stellar body of NGC 1275 along the same sight line. If the spiral disk is the remnant of a cannibalized galaxy, then its progenitor would have had to retain an enormous amount of gas in the face of intensive ram-pressure stripping so as to form a total initial mass in stars of ∼3 × 109 M ⊙. More likely, the central spiral originally comprised a gaseous body accreted over the distant past from a residual cooling flow, before experiencing a starburst ∼0.15 Gyr ago to form its stellar body.

Unveiling the true nature of dark matter, which manifests itself only through gravity, is one of the principal quests in physics. Leading candidates for dark matter are weakly interacting massive particles or ultralight bosons (axions), at opposite extremes in mass scales, that have been postulated by competing theories to solve deficiencies in the Standard Model of particle physics. Whereas dark matter weakly interacting massive particles behave like discrete particles (ϱDM), quantum interference between dark matter axions is manifested as waves (ψDM). Here, we show that gravitational lensing leaves signatures in multiply lensed images of background galaxies that reveal whether the foreground lensing galaxy inhabits a ϱDM or ψDM halo. Whereas ϱDM lens models leave well documented anomalies between the predicted and observed brightnesses and positions of multiply lensed images, ψDM lens models correctly predict the level of anomalies remaining with ϱDM lens models. More challengingly, when subjected to a battery of tests for reproducing the quadruply lensed triplet images in the system HS 0810+2554, ψDM is able to reproduce all aspects of this system whereas ϱDM often fails. The ability of ψDM to resolve lensing anomalies even in demanding cases such as HS 0810+2554, together with its success in reproducing other astrophysical observations, tilt the balance toward new physics invoking axions.Modelling of the gravitationally lensed system HS 0810+2554 with wavelike dark matter resolves brightness and position anomalies remaining after the standard massive-particle dark matter treatment.

We address the nature and origin of super star clusters (SSCs) discovered by Holtzman et al. within a radius of ∼5 kpc from the center of NGC 1275, the giant elliptical galaxy at the center of the Perseus Cluster. We show that, in contrast with the much more numerous population of SSCs subsequently discovered up to ∼30 kpc from the center of this galaxy, the central SSC population have maximal masses an order of magnitude higher and a mass function with a shallower power-law slope. Furthermore, whereas the outer SSC population have ages spanning a few Myr to at least ∼1 Gyr, the central SSC population have ages strongly concentrated around ∼500 Myr with a 1σ dispersion of ∼100 Myr. These SSCs share a close spatial and temporal relationship with the “central spiral,” which also has a radius ∼5 kpc centered on NGC 1275 and a characteristic stellar age of ∼150 Myr. We argue that both the central SSC population and the central spiral formed from gas deposited by a residual cooling flow, with the SSCs forming first followed by the formation of the stellar body of the central spiral ∼300–400 Myr later. The ages of the central SSC population imply that they are able to withstand very strong tidal fields near the center of NGC 1275, making them genuine progenitor globular clusters. Evidently, a spiral disk hosting progenitor globular clusters has recently formed at the center of a giant elliptical galaxy.

Soft protons populating the space environment have affected the performance of the X-ray detectors on board Chandra and XMM-Newton, and they pose a threat for future high energy astrophysics missions with larger aperture, such as ATHENA. In this paper, we aim to predict the soft proton induced ATHENA backgrounds from the modelling of the orbital flux obtained using eROSITA on board SRG. To this end, we analysed the background measured by eROSITA and with the help of simulations we defined a range of values for the potential count-rate of quiet-time soft protons focused through the mirror shells. We used it to derive an estimate of the orbital soft proton flux, from which the induced background for the WFI and X-IFU detectors can be predicted, assuming ATHENA in the same L2-orbit as SRG. The scaling, based on the computed proton transmission yields of the optics and optical/thermal filters, indicates that the soft proton induced WFI and X-IFU backgrounds could be expected within the requirement. Regardless of where ATHENA will be placed (L1 or L2), our analysis also suggests that increasing somewhat the thickness of the WFI optical blocking filter, e.g. by ∼ 30%, would help to further reduce the soft proton flux onto the detector, which might be worth in case the planned magnetic diverters perform worse than expected due to soft proton neutralisation at the mirror level.

Magnetic halos of galaxies are crucial for understanding galaxy evolution, galactic-scale outflows and feedback from star formation activity. Identifying the magnetized halo of the Milky Way is challenging because of the potential contamination from foreground emission arising in local spiral arms. In addition, it is unclear how our magnetic halo is influenced by recently revealed large-scale structures such as the X-ray-emitting eROSITA Bubbles detected by the extended Roentgen Survey with an Imaging Telescope Array (eROSITA). Here we report the identification of several kiloparsec-scale magnetized structures on the basis of their polarized radio emission and their gamma-ray counterparts, which can be interpreted as the radiation of relativistic electrons in the Galactic magnetic halo. These non-thermal structures extend far above and below the Galactic plane and are spatially coincident with the thermal X-ray emission from the eROSITA Bubbles. The morphological consistency of these structures suggests a common origin, which can be sustained by Galactic outflows driven by active star-forming regions located in the Galactic Disk at 3–5 kpc from the Galactic Centre. These results reveal how X-ray-emitting and magnetized halos of spiral galaxies can be related to intense star formation activities and suggest that the X-shaped coherent magnetic structures observed in their halos can stem from galactic outflows. A magnetic galactic halo featuring coherent ridges several kiloparsecs above and below the Galactic Disk has been detected in multi-wavelength observations. The halo is probably a consequence of outflows driven by active star-forming regions in the disk.

SRG/eROSITA is situated in a halo orbit around L2 where the highly variable solar wind charge exchange (SWCX) emission from Earth's magnetosheath is expected to be negligible. The soft X-ray foreground emissions from the local hot bubble (LHB) and the remaining heliospheric SWCX emissions could be studied in unprecedented detail with eROSITA All-Sky Survey (eRASS) data in a 6-month cadence and better spectral resolution than ROSAT. We aim to use eRASS data of the sight lines towards three giant molecular clouds away from the Galactic plane to isolate and study the soft X-ray diffuse foreground emission. These X-ray shadows will serve as calibration baselines for the future three-dimensional structural study of the LHB. We conducted spectral analysis on the diffuse X-ray spectra of these clouds from the first four eRASSs to estimate and separate the heliospheric SWCX contribution from the LHB emission. We find the density of the LHB to be independent of the sight line with \\(n_e 4 10^-3\\,\\)cm\\(^-3\\), but not the temperature. We report a lower temperature of \\(kT_LHB=0.0840.004\\,\\)keV towards Chamaeleon\\(~\\)II & III (Cha\\(~\\)II & III) than Ophiuchus (Oph) and Corona Australis (CrA), in which we measured \\(0.1020.006\\) and \\(0.1120.009\\,\\)keV, respectively. We measured the emission measure of the LHB to be \\( 210^-3\\,\\)cm\\(^-6\\,\\)pc at medium Galactic latitudes (\\(|b| 20^\\)). A monotonic increase in the SWCX contribution has been observed since the start of 2020, coincidental with the beginning of solar cycle 25. For Oph, SWCX has dominated the LHB in the \\(0.3\\)-\\(0.7\\,\\)keV band intensity since eRASS2. We observed lower SWCX contributions in Cha\\(~\\)II & III and CrA, consistent with the expected decreasing solar wind ion density at high heliographic latitudes.

Methods. We utilized the combined five SRG/eROSITA All-Sky Survey data (eRASS:5) to perform X-ray imaging and spectral analyses of the Centaurus cluster in various directions to large radii. Surface brightness (SB) profiles out to \\(2R_200\\) were constructed. We acquired gas temperature, metallicity, and normalization per area profiles out to \\(R_200\\). We compared our results with previous Centaurus studies, cluster outskirts measurements, and simulations. Comprehensive sky background analysis was done across the FoV, in particular, to assess the variation of the eROSITA Bubble emission that partially contaminates the field. Results. The processed X-ray images show the known sloshing-induced structures in the core. The core (\\(r11~kpc\\)) is better described with a 2T model than a 1T model. Here, we measured lower T from the cooler component (~1.0 keV) and higher Z (\\(\\!1.6Z_\\)), signifying an iron bias. In the intermediate radial range, we observed prominent SB and normalization per area excesses in the eastern sector (Cen 45 location), reaching out to \\(R_500\\). Temperature enhancements near the location of Cen 45 imply that the gas is shock-heated due to the interaction with Cen 30, the significant excess behind Cen 45 center might be the tail/ram-pressure-stripped gas. We found good agreement between the outskirt temperatures with the profile from simulations and fit from Suzaku outskirts measurements. We detected significant SB emission to the sky background level out to \\(R_200\\) with a \\(3.5\\) and followed by \\(2.9\\) at \\(1.1R_200\\). The metallicity at \\(R_500-R_200\\) is low but within the ranges of other outskirts studies. Conclusions. We present the first measurement of ICM morphology and properties of Centaurus cluster sampling the whole azimuth beyond \\(30'\\), increasing the probed volume by a factor of almost 30.

The SRG/eROSITA All-Sky Surveys (eRASSs) combine the advantages of complete sky coverage and the energy resolution provided by the charge couple device and offer the most holistic and detailed view of the diffuse soft X-ray background (SXRB) to date. The first eRASS (eRASS1) was completed at solar minimum, when solar wind charge exchange emission was minimal, providing the clearest view of the SXRB. We aim to extract spatial and spectral information from each constituent of the SXRB in the western Galactic hemisphere, focusing on the local hot bubble (LHB). We extracted and analysed eRASS1 spectra from almost all directions in the western Galactic hemisphere by dividing the sky into equal signal-to-noise bins. We fitted all bins with fixed spectral templates of known background constituents. We find the temperature of the LHB exhibits a north-south dichotomy at high latitudes (\\(|b|>30^\\)), with the south being hotter, with a mean temperature at \\(kT=121.80.6\\,\\)eV and the north at \\(kT=100.80.5\\,\\)eV. At low latitudes, the LHB temperature increases towards the Galactic plane, especially towards the inner Galaxy. The LHB emission measure (\\( EM_LHB\\)) enhances approximately towards the Galactic poles. The \\( EM_LHB\\) map shows clear anti-correlation with the local dust column density. In particular, we found tunnels of dust cavities filled with hot plasma, potentially forming a wider network of hot interstellar medium. We also constructed a three-dimensional LHB model from \\( EM_LHB\\), assuming constant density. The average thermal pressure of the LHB is \\(P_ thermal/k=10100^+1200_-1500\\, cm^-3\\,K\\), a lower value than typical supernova remnants and wind-blown bubbles. This could be an indication of the LHB being open towards high Galactic latitudes.

We address the nature and origin of Super Star Clusters (SSCs) discovered by Holtzman et al. (1992) within a radius of$\\sim$ $5\\,\\rm kpc\\( from the center of NGC 1275, the giant elliptical galaxy at the center of the Perseus Cluster. We show that, in contrast with the much more numerous population of SSCs subsequently discovered up to \\)\\sim$ $30\\,\\rm kpc\\( from the center of this galaxy, the central SSC population have maximal masses an order of magnitude higher and a mass function with a shallower power-law slope. Furthermore, whereas the outer SSC population have ages spanning a few \\)\\rm Myr\\( to at least \\)\\sim$ $1\\,\\rm Gyr\\(, the central SSC population have ages strongly concentrated around \\)\\sim$ $500 \\rm \\, Myr\\( with a \\)1\\,\\sigma\\( dispersion of \\)\\sim$ $100\\,\\rm Myr\\(. These SSCs share a close spatial and temporal relationship with the \"central spiral,\" which also has a radius \\)\\sim$ $5\\,\\rm kpc\\( centered on NGC 1275 and a characteristic stellar age of \\)\\sim$ $150\\,\\rm Myr\\( (Paper I). We argue that both the central SSC population and the central spiral formed from gas deposited by a residual cooling flow, with the SSCs forming first followed by the formation of the stellar body of the central spiral \\)\\sim$ $300\\(-\\)400\\,\\rm Myr$later. The ages of the central SSC population imply that they are able to withstand very strong tidal fields near the center of NGC 1275, making them genuine progenitor globular clusters. Evidently, a spiral disk hosting progenitor globular clusters has recently formed at the center of a giant elliptical galaxy.