Astronomy & Astrophysics最新文献

{"title":"CHANG-ES","authors":"M. Stein, J. Kleimann, B. Adebahr, R.-J. Dettmar, H. Fichtner, J. English, V. Heesen, P. Kamphuis, J. Irwin, C. Mele, D. J. Bomans, J. Li, N. B. Skeggs, Q. D. Wang, Y. Yang","doi":"10.1051/0004-6361/202452322","DOIUrl":"https://doi.org/10.1051/0004-6361/202452322","url":null,"abstract":"<i>Context.<i/> Understanding the configuration of galactic magnetic fields is essential for interpreting feedback processes in galaxies. Despite their importance, the exact structure of these fields, particularly in galactic halos, remains unclear. Accurate descriptions are crucial for understanding the interaction between star formation and halo magnetisation.<i>Aims.<i/> By systematically analysing the polarisation patterns in halos of nearby galaxies, we aim to deepen the understanding of the interplay between galactic magnetic fields and star formation processes. Here, we focus on the process of magnetising the galactic halo. Furthermore, we provide an analytical description of the observed X shaped halos.<i>Methods.<i/> Based on <i>C<i/> band (6 GHz) radio polarimetry data, we manually classified the polarisation patterns of a sample of nearby late-type edge-on galaxies, by using a newly introduced three-class system: disc-dominated, small-scale, and X shaped. We then fitted X shaped patterns to the polarisation data for galaxies classified as X shaped and explored links between the polarisation patterns and other physical properties of these galaxies.<i>Results.<i/> The classification process shows that 11 out of 18 analysed galaxies with extended polarised halo emission display an X shaped polarisation pattern. Galaxies classified as disc-dominated seem less efficient at forming stars than expected for their stellar mass and rotate faster than galaxies with similarly sized HI discs. X shape modelling reveals that the polarisation patterns are best fitted by a constant-angle model, and we observe a correlation between the X shape opening angle and star formation rate surface density, indicating the interplay between the star formation in the disc and the magnetisation of the galactic halo.<i>Conclusions.<i/> The analysis of polarisation patterns in nearby galaxies reveals that most exhibit an X shaped configuration, indicating a common magnetic field structure in galactic halos. The introduced models capture the X shaped morphology and reveal the link between the X shape’s opening angle and star formation rate surface density.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"75 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143814230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A possible GeV-TeV connection in the direction of the globular cluster UKS 1","authors":"J. Shin, C. Y. Hui, S. Kim, K. Oh, E. R. Owen","doi":"10.1051/0004-6361/202554239","DOIUrl":"https://doi.org/10.1051/0004-6361/202554239","url":null,"abstract":"<i>Aims.<i/> Using public data collected by the <i>Fermi<i/> Large Area Telescope (LAT) over 16 years and the 1523 days of survey data (3HWC) from the High Altitude Water Cherenkov (HAWC) observatory, we searched for possible GeV-TeV connections in globular clusters (GCs).<i>Methods.<i/> Excluding 44 confirmed <i>γ<i/>-ray detections of GCs in the latest Fourth <i>Fermi<i/>-LAT point source catalog (4FGL-DR4), we searched for possible GeV emission from the other 113 known GCs based on 16 years of LAT data. We performed a systematic binned likelihood analysis in the energy range of 0.3–100 GeV toward these targets. We also searched for possible TeV excesses in the directions of 27 GeV-detected GCs covered by the 3HWC survey area, assuming a point-source morphology and a power-law spectrum of <i>E<i/><sup>−2.5<sup/>.<i>Results.<i/> In addition to the confirmed <i>γ<i/>-ray GCs in the 4FGL catalog, we report a GeV detection at the position of UKS 1 with a post-trial probability of ∼8 × 10<sup>−5<sup/> of it proving to be a fluctuation. Its spectrum within this energy range is well described by a power-law model with Γ ≃ 2.3 ± 0.5. Furthermore, this GeV feature appears to extend southeast in a direction toward the Galactic plane. From the 3HWC survey data, we have also identified a TeV feature in the direction of UKS 1. It is well resolved from any known very-high-energy (VHE) source. The post-trial probability that this feature is a fluctuation is ∼3 × 10<sup>−4<sup/>. If confirmed, this would mark the second detection of a TeV feature in the proximity of a GC. While the GeV emission mostly coincides with the center of UKS 1, the TeV peak is displaced from the cluster center by several tidal radii in the trailing direction of the GC’s proper motion. Given the supersonic speed of UKS 1 at ∼270 km s<sup>−1<sup/>, our findings are consistent with a scenario where the VHE <i>γ<i/>-rays are produced by inverse Compton scattering between relativistic particles and ambient soft photon fields during the course of their propagation away from the head of the bow shock.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"12 1","pages":"L11"},"PeriodicalIF":6.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143798107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intergalactic magnetism in a γ-ray beam as a model of Porphyrion","authors":"Andrii Neronov, Franco Vazza, Axel Brandenburg, Chiara Caprini","doi":"10.1051/0004-6361/202453099","DOIUrl":"https://doi.org/10.1051/0004-6361/202453099","url":null,"abstract":"We estimate the magnetic field in the jets of the recently discovered 7 Mpc long Porphyrion system. We used nondetection of the system in gamma-rays to derive a lower bound on the co-moving magnetic field strength at the level of ∼10 nG (comoving). This value is consistent with recent estimates of magnetic fields in the filaments of the large-scale structure. We discuss the possibility that, instead of being the extreme case of a radio jet formation scenario, Porphyrion actually traces a very high-energy <i>γ<i/>-ray beam emitted by an active galactic nucleus. In such a model, jets do not need to spread into the voids of the large-scale structure to appear straight on a very large distance range, and several anomalies of the standard radio jet scenarios can be solved at once.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"72 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143798109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Further evidence of saturated, boosted, and disrupted magnetic braking from evolutionary tracks of cataclysmic variables","authors":"Joaquín A. Barraza-Jorquera, Matthias R. Schreiber, Diogo Belloni","doi":"10.1051/0004-6361/202553757","DOIUrl":"https://doi.org/10.1051/0004-6361/202553757","url":null,"abstract":"<i>Context.<i/> Angular momentum loss through magnetic braking drives the spin-down of low-mass stars and the orbital evolution of a variety of close binary stars. Current theories for magnetic braking, often calibrated for one particular type of system, predict angular momentum loss rates that differ by several orders of magnitude. A unified prescription, even if fully empirical, would provide important constraints on the relation between angular momentum loss, stellar dynamos, and stellar magnetic activity.<i>Aims.<i/> Recent studies have shown that a saturated, boosted, and disrupted (SBD) magnetic braking prescription explains the increase in the fraction of close systems among white dwarf plus M-dwarf binaries at the fully convective boundary, the period distribution of main-sequence star binaries, and the mass distribution of close M-dwarf companions to hot subdwarfs. With the aim of analyzing whether this prescription is also applicable to related binaries, we investigated the evolution of cataclysmic variables assuming a SBD magnetic braking prescription.<i>Methods.<i/> We incorporated the SBD magnetic braking model into the stellar evolution code MESA and simulated the evolution of cataclysmic variables, testing different values for the boosting (<i>K<i/>) and the disruption (<i>η<i/>) parameters for different stellar parameters.<i>Results.<i/> The model accurately reproduces the mass transfer rates and the donor star mass-radius relation. The corresponding evolutionary tracks are in good agreement with the observed boundaries of the orbital period gap as well as the period minimum when assuming <i>K<i/> ≃ <i>η<i/> ≃ 30 − 50. These values for <i>K<i/> and <i>η<i/> are slightly smaller than but consistent with those determined from detached binaries (<i>K<i/> ≃ <i>η<i/> ≳ 50).<i>Conclusions.<i/> Angular momentum loss through SBD magnetic braking can explain not only observations of detached binaries but also cataclysmic variables, that is, it is the only prescription currently available that is suitable for several types of close binary stars. The model needs to be tested further in the context of other close binary and single stars, and the currently used semi-empirical convective turnover time for main-sequence stars needs to be replaced with self-consistent turnover times.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"23 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143798220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The eventful life of a luminous galaxy at z = 14: metal enrichment, feedback, and low gas fraction?","authors":"Stefano Carniani, Francesco D’Eugenio, Xihan Ji, Eleonora Parlanti, Jan Scholtz, Fengwu Sun, Giacomo Venturi, Tom J. L. C. Bakx, Mirko Curti, Roberto Maiolino, Sandro Tacchella, Jorge A. Zavala, Kevin Hainline, Joris Witstok, Benjamin D. Johnson, Stacey Alberts, Andrew J. Bunker, Stéphane Charlot, Daniel J. Eisenstein, Jakob M. Helton, Peter Jakobsen, Nimisha Kumari, Brant Robertson, Aayush Saxena, Hannah Übler, Christina C. Williams, Christopher N. A. Willmer, Chris Willott","doi":"10.1051/0004-6361/202452451","DOIUrl":"https://doi.org/10.1051/0004-6361/202452451","url":null,"abstract":"JADES-GS-z14-0 is the most distant spectroscopically confirmed galaxy yet, at <i>z<i/>≳14. With a UV magnitude of –20.81, it is one of the most luminous galaxies at cosmic dawn and its half-light radius of 260 pc means that stars dominate the observed UV emission. We report the Atacama Large Millimeter/submillimeter Array (ALMA) detection of [O III]88 μm line emission with a significance of 6.67<i>σ<i/> and at a frequency of 223.524 GHz, corresponding to a redshift of 14.1796±0.0007, which is consistent with the candidate C III] line detected in the NIRSpec spectrum. At this spectroscopic redshift, the Lyman-<i>α<i/> break identified with NIRSpec requires a damped Lyman-<i>α<i/> absorber with a column density of log(<i>N<i/><sub>HI<sub/>/cm<sup>−2<sup/>) = 21.96. The total [O III]88 μm luminosity (log(<i>L<i/><sub>[OIII]<sub/>/L<sub>⊙<sub/>) = 8.3±0.1) is fully consistent with the local <i>L<i/><sub>[OIII]<sub/>−<i>SFR<i/> relation and indicating a gas-phase metallicity >0.1 Z<sub>⊙<sub/>. Using prospector spectral energy distribution (SED) modeling and combining the ALMA data with JWST observations, we find <i>Z<i/> = 0.17 Z<sub>⊙<sub/> and a non-zero escape fraction of ionizing photons (∼11%), which is necessary by the code to reproduce the UV spectrum. We measure an [OIII]5007 Å/[OIII]88 μm line flux ratio between 1 and 20, resulting in an upper limit to the electron density of roughly 700 cm<sup>−3<sup/> assuming a single-cloud photoionization model. The [O III]emission line is spectrally resolved, with a FWHM of 102 km s<sup>−1<sup/>, resulting in a dynamical mass of log(M<sub>dyn<sub/>/M<sub>⊙<sub/>) = 9.0±0.2. When compared to the stellar mass, this value represents a conservative upper limit on the gas mass fraction, which ranges from 50% to 80%, depending on the assumed star formation history. Past radiation-driven outflows may have cleared the galaxy from the gas, reducing the gas fraction and thus increasing the escape fraction of ionizing photons.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"183 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143798222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Secondary black hole-induced magnetic reconnection in OJ 287: Implications for X-ray and radio emission","authors":"S. Boula, A. Nathanail","doi":"10.1051/0004-6361/202453332","DOIUrl":"https://doi.org/10.1051/0004-6361/202453332","url":null,"abstract":"<i>Context.<i/> OJ 287, a nearby blazar, has exhibited remarkable variability in its optical light curve since 1888, characterized by 2-year quasi-periodic outbursts. These events are attributed to the orbital dynamics of a supermassive binary black hole system at the heart of the blazar. This study explores the role of magnetic reconnection and the formation of plasmoid chains in driving the energetic processes responsible for OJ 287’s variability. We propose that the passage of the secondary black hole through the magnetic field of the primary black hole’s accretion disk triggers magnetic reconnection, which contributes to the observed X-ray and radio emission features in OJ 287.<i>Aims.<i/> We explore the connection between binary black hole interactions, accretion disk dynamics, and the formation of plasmoid chains as the secondary black hole passes through the magnetic field forest from the accretion disk and the jet of the primary. Magnetic reconnection is the fundamental process behind particle acceleration, potentially influencing the observed emissions and variability, particularly during specific orbital phases of OJ 287.<i>Methods.<i/> Our approach relies on numerical simulations to understand the formation of plasmoid chains resulting from black hole interactions and accretion disk dynamics. Based on such results, we employ simulation outcomes to examine the potential contribution to observed emissions, validating our assumptions about plasmoid chain creation. With this idea, we aim to establish a direct link between numerical simulations and observed emission, particularly in the case of OJ 287.<i>Results.<i/> Our findings confirm that the formation of plasmoid chains coincides with specific anomalous emission events observed in OJ 287. Notably, the radio emission patterns cannot be explained by a single blob model, as the necessary size to mitigate synchrotron self-absorption would be too large. This highlights the complexity of the emission processes and suggests that plasmoid chains could contribute to additional emission components beyond the steady jet.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"27 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143797979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Search and analysis of giant radio galaxies with associated nuclei (SAGAN)","authors":"P. Dabhade, K. Chavan, D. J. Saikia, M. S. S. L. Oei, H. J. A. Röttgering","doi":"10.1051/0004-6361/202451918","DOIUrl":"https://doi.org/10.1051/0004-6361/202451918","url":null,"abstract":"To test the hypothesis that megaparsec-scale giant radio galaxies (GRGs) experience multiple epochs of recurrent activity leading to their giant sizes and to understand the nature of double-double radio galaxies (DDRGs), we have built the largest sample of giant DDRGs from the LOFAR Two Metre Sky Survey (LoTSS) data release 2. This sample comprises 111 sources, including 76 newly identified DDRGs, with redshifts ranging from 0.06 to 1.6 and projected sizes between 0.7 Mpc and 3.3 Mpc. We conducted a detailed analysis to characterise their properties, including arm-length ratios, flux density ratios of pairs of lobes, and misalignment angles. These measurements allow us to study the symmetry parameters, which are influenced by the immediate and large-scale environments of DDRGs. Our study shows that based on the observed asymmetries of the inner lobes, the cocoons in which the inner lobes of DDRGs grow are often (approximately about 26%) asymmetrically contaminated with surrounding material from the external medium. Our analysis also reveals highly misaligned DDRGs, which could be due to environmental factors and/or changes in the supermassive black hole jet ejection axes. By studying the misalignment angles, we assess the stability of the jets in these systems in relation to their environment. For the first time, we systematically characterised the large-scale environments of DDRGs, identifying their association with dense galaxy clusters and revealing the influence of ‘cluster weather’ on their morphologies. We have discovered a DDRG in a distant galaxy cluster at <i>z<i/> ∼ 1.4. Our findings empirically confirm that dynamic cluster environments can induce significant misalignment in DDRGs, which aligns with previous simulation predictions and offers insights into how cluster weather shapes their morphology. Additionally, we have identified two gigahertz peaked-spectrum (GPS) candidates in the unresolved cores of the DDRGs, as well as one triple-double candidate, which, if confirmed, would be only the fifth known case. Overall, this study enhances our understanding of the life cycle of radio AGNs and underscores the critical role of the environment in shaping the properties and evolution of giant DDRGs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143798342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PDRs4All","authors":"J. R. Goicoechea, J. Pety, S. Cuadrado, O. Berné, E. Dartois, M. Gerin, C. Joblin, J. Kłos, F. Lique, T. Onaka, E. Peeters, A. G. G. M. Tielens, F. Alarcón, E. Bron, J. Cami, A. Canin, E. Chapillon, R. Chown, A. Fuente, E. Habart, O. Kannavou, F. Le Petit, M. G. Santa-Maria, I. Schroetter, A. Sidhu, B. Trahin, D. Van De Putte, M. Zannese","doi":"10.1051/0004-6361/202453350","DOIUrl":"https://doi.org/10.1051/0004-6361/202453350","url":null,"abstract":"The infrared emission from polycyclic aromatic hydrocarbons (PAHs), along with emission from atomic carbon and simple hydrocarbons, is a robust tracer of the interaction between stellar far-UV (FUV) radiation and molecular clouds. We present subarcsecond-resolution ALMA mosaics of the Orion Bar photodissociation region (PDR) in [C I] 609 μm (<sup>3<sup/>P<sub>1<sub/>−<sup>3<sup/>P<sub>0<sub/>), C<sub>2<sub/>H (<i>N<i/> = 4−3), and C<sup>18<sup/>O (<i>J<i/> = 3−2) emission lines complemented by JWST images of H<sub>2<sub/> and aromatic infrared band (AIB) emission. We interpreted the data using up-to-date PDR and radiative transfer models, including high-temperature C<sub>2<sub/>H (X<sup>2<sup/> Σ<sup>+<sup/>)-<i>o<i/>/<i>p<i/>-H<sub>2<sub/> and C (<sup>3<sup/>P)-<i>o<i/>/<i>p<i/>-H<sub>2<sub/> inelastic collision rate coefficients (we computed the latter up to 3000 K). The rim of the Bar shows very corrugated and filamentary structures made of small-scale H<sub>2<sub/> dissociation fronts (DFs). The [C I] 609 μm emission peaks very close (≲ 0.002 pc) to the main H<sub>2<sub/>-emitting DFs, suggesting the presence of gas density gradients. These DFs are also bright and remarkably similar in C<sub>2<sub/>H emission, which traces “hydrocarbon radical peaks” characterized by very high C<sub>2<sub/>H abundances, reaching up to several ×10<sup>−7<sup/>. The high abundance of C<sub>2<sub/>H and of related hydrocarbon radicals, such as CH<sub>3<sub/>, CH<sub>2<sub/>, and CH, can be attributed to gas-phase reactions driven by elevated temperatures, the presence of C<sup>+<sup/> and C, and the reactivity of FUV-pumped H<sub>2<sub/>. The hydrocarbon radical peaks roughly coincide with maxima of the 3.4/3.3 μm AIB intensity ratio, which is a proxy for the aliphatic-to-aromatic content of PAHs. This implies that the conditions triggering the formation of simple hydrocarbons also favor the formation (and survival) of PAHs with aliphatic side groups, potentially via the contribution of bottom-up processes in which abundant hydrocarbon radicals react in situ with PAHs. Ahead of the DFs, in the atomic PDR zone (where [H] ≫ [H<sub>2<sub/>]), the AIB emission is the brightest, but small PAHs and carbonaceous grains undergo photo-processing due to the stronger FUV field. Our detection of trace amounts of C<sub>2<sub/>H in this zone may result from the photoerosion of these species. This study provides a spatially resolved view of the chemical stratification of key carbon carriers in a PDR. Overall, both bottom-up and top-down processes appear to link simple hydrocarbon molecules with PAHs in molecular clouds; however, the exact chemical pathways and their relative contributions remain to be quantified.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"38 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143798346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A molecule-rich torus-like structure in the 21 µm source IRAS 23304+6147","authors":"Hao-Min Sun, Yong Zhang, Xu-Jia Ouyang, Sheng-Li Qin, Junichi Nakashima, Jian-Jie Qiu, Xiao-Hu Li","doi":"10.1051/0004-6361/202452355","DOIUrl":"https://doi.org/10.1051/0004-6361/202452355","url":null,"abstract":"<i>Context.<i/> A long-standing enigma in observational astronomy is the identification of the so-called 21 µm feature in a subset of envelopes of post-asymptotic giant branch (post-AGB) stars. Identifying this transient feature is important for understanding the chemical processes during the brief post-AGB phase and the enrichment of the interstellar medium. Understanding the structures and chemical environments of these objects is a prerequisite for this endeavor.<i>Aims.<i/> We investigate the structure of the circumstellar envelope and the spatial distribution of gas-phase molecules in the 21 µm source IRAS 23304+6147 with the aim to explore the potential physicochemical conditions required for the emergence of the 21 µm feature.<i>Methods.<i/> Molecular line observations toward IRAS 23304+6147 at the 1.3 mm band were performed using the Northern Extended Millimeter Array. A morpho-kinematic model was built to reproduce the observed <sup>13<sup/>CO images and to decipher the structures of the nebula.<i>Results.<i/> The imaging results reveal an elliptically elongated shell with an equatorial density enhancement (or a torus-like structure), which shows in detail how the various molecules are distributed in the envelope. The nebular morphology indicates a binary system in which the ultraviolet radiation from the companion might trigger photochemistry in the inner regions. The torus-like structure exhibits an enrichment of linear carbon-chain molecules and a depletion of silicon-bearing molecules. This nebula has a lower mass limit of 1.3 × 10<sup>−2<sup/> M<sub>⊙<sub/> and might exhibit a low <sup>12<sup/>CO/<sup>13<sup/>CO abundance ratio.<i>Conclusions.<i/> The chemically stratified structure of <sup>13<sup/>CN, HC<sub>3<sub/>N, and C<sub>4<sub/>H represents observational evidence of the internal radiation that initiates photochemistry. The carbon-rich torus-like structure probably offers a conducive environment for the formation of dust and complex molecules that are part of the rare 21 µm emission. We hypothesize that the 21 µm sources probably descend from J-type carbon stars via a binary evolutionary channel.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"23 1","pages":"A102"},"PeriodicalIF":6.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143798214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PDRs4All","authors":"M. Zannese, B. Tabone, E. Habart, E. Dartois, J. R. Goicoechea, L. Coudert, B. Gans, M.-A. Martin-Drumel, U. Jacovella, A. Faure, B. Godard, A. G. G. M. Tielens, R. Le Gal, J. H. Black, S. Vicente, O. Berné, E. Peeters, D. Van De Putte, R. Chown, A. Sidhu, I. Schroetter, A. Canin, O. Kannavou","doi":"10.1051/0004-6361/202453441","DOIUrl":"https://doi.org/10.1051/0004-6361/202453441","url":null,"abstract":"&lt;i&gt;Context&lt;i/&gt;. The methylidyne cation (CH&lt;sup&gt;+&lt;sup/&gt;) and the methyl cation (CH&lt;sub&gt;3&lt;sub/&gt;&lt;sup&gt;+&lt;sup/&gt;) are building blocks of organic molecules in the ultraviolet (UV) irradiated gas, yet their coupled formation and excitation mechanisms mostly remain unprobed. The James Webb Space Telescope (JWST), with its high spatial resolution and good spectral resolution, provides unique access to the detection of these molecules.&lt;i&gt;Aims&lt;i/&gt;. Our goal is to use the first detection of CH&lt;sup&gt;+&lt;sup/&gt; and CH&lt;sub&gt;3&lt;sub/&gt;&lt;sup&gt;+&lt;sup/&gt; infrared rovibrational emission in the Orion Bar and in the protoplanetary disk d203-506 to probe their formation and excitation mechanisms and constrain the physico-chemical conditions of the environment.&lt;i&gt;Methods&lt;i/&gt;. We used spectro-imaging acquired using both the NIRSpec and MIRI-MRS instruments on board JWST to study the infrared CH&lt;sup&gt;+&lt;sup/&gt; and CH&lt;sub&gt;3&lt;sub/&gt;&lt;sup&gt;+&lt;sup/&gt; spatial distribution at very small scales (down to 0.1′′) and compared it to excited H&lt;sub&gt;2&lt;sub/&gt; emission. We studied their excitation in detail, and in the case of CH&lt;sup&gt;+&lt;sup/&gt;, we compared the observed line intensities with chemical formation pumping models based on recent quantum dynamical calculations. Throughout this study, we compare the emission of these molecules in two environments: the Bar a photodissociation region – and a protoplanetary disk (d203-506), both of which are irradiated by the Trapezium cluster.&lt;i&gt;Results&lt;i/&gt;. We detected CH&lt;sup&gt;+&lt;sup/&gt; and CH&lt;sub&gt;3&lt;sub/&gt;&lt;sup&gt;+&lt;sup/&gt; vibrationally excited emission both in the Bar and d203-506. These emissions originate from the same region as highly excited H&lt;sub&gt;2&lt;sub/&gt; (high rotational and rovibrational levels) and correlate less with the lower rotational levels of H&lt;sub&gt;2&lt;sub/&gt; (&lt;i&gt;J&lt;i/&gt;′ &lt; 5) or the emission of aromatic and aliphatic infrared bands. Our comparison between the Bar and d203-506 revealed that both CH&lt;sup&gt;+&lt;sup/&gt; and CH&lt;sub&gt;3&lt;sub/&gt;&lt;sup&gt;+&lt;sup/&gt; excitation and/or formation are highly dependent on gas density. The excitation temperature of the observed CH&lt;sup&gt;+&lt;sup/&gt; and CH&lt;sub&gt;3&lt;sub/&gt;&lt;sup&gt;+&lt;sup/&gt; rovibrational lines is around &lt;i&gt;T&lt;i/&gt; ∼ 1500 K in the Bar and &lt;i&gt;T&lt;i/&gt; ∼ 800 K in d203-506. Moreover, the column densities derived from the rovibrational emission are less than 0.1% of the total known (CH&lt;sup&gt;+&lt;sup/&gt;) and expected (CH&lt;sub&gt;3&lt;sub/&gt;&lt;sup&gt;+&lt;sup/&gt;) column densities. These different results show that CH&lt;sup&gt;+&lt;sup/&gt; and CH&lt;sub&gt;3&lt;sub/&gt;&lt;sup&gt;+&lt;sup/&gt; level populations strongly deviate from local thermodynamical equilibrium. The CH&lt;sup&gt;+&lt;sup/&gt; rovibrational supra-thermal emission (&lt;i&gt;v&lt;i/&gt; = 1 and &lt;i&gt;v&lt;i/&gt; = 2) can be explained by chemical formation pumping with excited H&lt;sub&gt;2&lt;sub/&gt; via C&lt;sup&gt;+&lt;sup/&gt; + H&lt;sub&gt;2&lt;sub/&gt;&lt;sup&gt;*&lt;sup/&gt; = CH&lt;sup&gt;+&lt;sup/&gt; + H. The difference in the population distribution of the H&lt;sub&gt;2&lt;sub/&gt;&lt;sup&gt;*&lt;sup/&gt; energy levels between the Orion Bar and d203-506 then result in different excitation temperatures. These results support a gas phase formation pathway of ","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"42 12 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143798110","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}