Astronomy & Astrophysics最新文献

{"title":"The persistent shadow of the supermassive black hole of M87","authors":"Kazunori Akiyama, Ezequiel Albentosa-Ruíz, Antxon Alberdi, Walter Alef, Juan Carlos Algaba, Richard Anantua, Keiichi Asada, Rebecca Azulay, Uwe Bach, Anne-Kathrin Baczko, David Ball, Mislav Baloković, Bidisha Bandyopadhyay, John Barrett, Michi Bauböck, Bradford A. Benson, Dan Bintley, Lindy Blackburn, Raymond Blundell, Katherine L. Bouman, Geoffrey C. Bower, Michael Bremer, Roger Brissenden, Silke Britzen, Avery E. Broderick, Dominique Broguiere, Thomas Bronzwaer, Sandra Bustamante, John E. Carlstrom, Andrew Chael, Chi-kwan Chan, Dominic O. Chang, Koushik Chatterjee, Shami Chatterjee, Ming-Tang Chen, Yongjun Chen, Xiaopeng Cheng, Ilje Cho, Pierre Christian, Nicholas S. Conroy, John E. Conway, Thomas M. Crawford, Geoffrey B. Crew, Alejandro Cruz-Osorio, Yuzhu Cui, Brandon Curd, Rohan Dahale, Jordy Davelaar, Mariafelicia De Laurentis, Roger Deane, Jessica Dempsey, Gregory Desvignes, Jason Dexter, Vedant Dhruv, Indu K. Dihingia, Sheperd S. Doeleman, Sergio A. Dzib, Ralph P. Eatough, Razieh Emami, Heino Falcke, Joseph Farah, Vincent L. Fish, Edward Fomalont, H. Alyson Ford, Marianna Foschi, Raquel Fraga-Encinas, William T. Freeman, Per Friberg, Christian M. Fromm, Antonio Fuentes, Peter Galison, Charles F. Gammie, Roberto García, Olivier Gentaz, Boris Georgiev, Ciriaco Goddi, Roman Gold, Arturo I. Gómez-Ruiz, José L. Gómez, Minfeng Gu, Mark Gurwell, Kazuhiro Hada, Daryl Haggard, Ronald Hesper, Dirk Heumann, Luis C. Ho, Paul Ho, Mareki Honma, Chih-Wei L. Huang, Lei Huang, David H. Hughes, Shiro Ikeda, C. M. Violette Impellizzeri, Makoto Inoue, Sara Issaoun, David J. James, Buell T. Jannuzi, Michael Janssen, Britton Jeter, Wu Jiang, Alejandra Jiménez-Rosales, Michael D. Johnson, Svetlana Jorstad, Adam C. Jones, Abhishek V. Joshi, Taehyun Jung, Ramesh Karuppusamy, Tomohisa Kawashima, Garrett K. Keating, Mark Kettenis, Dong-Jin Kim, Jae-Young Kim, Jongsoo Kim, Junhan Kim, Motoki Kino, Jun Yi Koay, Prashant Kocherlakota, Yutaro Kofuji, Patrick M. Koch, Shoko Koyama, Carsten Kramer, Joana A. Kramer, Michael Kramer, Thomas P. Krichbaum, Cheng-Yu Kuo, Noemi La Bella, Sang-Sung Lee, Aviad Levis, Zhiyuan Li, Rocco Lico, Greg Lindahl, Michael Lindqvist, Mikhail Lisakov, Jun Liu, Kuo Liu, Elisabetta Liuzzo, Wen-Ping Lo, Andrei P. Lobanov, Laurent Loinard, Colin J. Lonsdale, Amy E. Lowitz, Ru-Sen Lu, Nicholas R. MacDonald, Jirong Mao, Nicola Marchili, Sera Markoff, Daniel P. Marrone, Alan P. Marscher, Iván Martí-Vidal, Satoki Matsushita, Lynn D. Matthews, Lia Medeiros, Karl M. Menten, Izumi Mizuno, Yosuke Mizuno, Joshua Montgomery, James M. Moran, Kotaro Moriyama, Monika Moscibrodzka, Wanga Mulaudzi, Cornelia Müller, Hendrik Müller, Alejandro Mus, Gibwa Musoke, Ioannis Myserlis, Hiroshi Nagai, Neil M. Nagar, Dhanya G. Nair, Masanori Nakamura, Gopal Narayanan, Iniyan Natarajan, Antonios Nathanail, Santiago Navarro Fuentes, Joey Neilsen, Chunchong Ni, Michael A. Nowak, Junghwan Oh, Hiroki Okino, Héctor Raúl Olivares Sánchez, Tomoaki Oyama, Feryal Özel, Daniel C. M. Palumbo, Georgios Filippos Paraschos, Jongho Park, Harriet Parsons, Nimesh Patel, Ue-Li Pen, Dominic W. Pesce, Vincent Piétu, Aleksandar PopStefanija, Oliver Porth, Ben Prather, Giacomo Principe, Dimitrios Psaltis, Hung-Yi Pu, Venkatessh Ramakrishnan, Ramprasad Rao, Mark G. Rawlings, Luciano Rezzolla, Angelo Ricarte, Bart Ripperda, Freek Roelofs, Cristina Romero-Cañizales, Eduardo Ros, Arash Roshanineshat, Helge Rottmann, Alan L. Roy, Ignacio Ruiz, Chet Ruszczyk, Kazi L. J. Rygl, Salvador Sánchez, David Sánchez-Argüelles, Miguel Sánchez-Portal, Mahito Sasada, Kaushik Satapathy, Tuomas Savolainen, F. Peter Schloerb, Jonathan Schonfeld, Karl-Friedrich Schuster, Lijing Shao, Zhiqiang Shen, Des Small, Bong Won Sohn, Jason SooHoo, León D. S. Salas, Kamal Souccar, Joshua S. Stanway, He Sun, Fumie Tazaki, Alexandra J. Tetarenko, Paul Tiede, Remo P. J. Tilanus, Michael Titus, Kenji Toma, Pablo Torne, Teresa Toscano, Efthalia Traianou, Tyler Trent, Sascha Trippe, Matthew Turk, Ilse van Bemmel, Huib Jan van Langevelde, Daniel R. van Rossum, Jesse Vos, Jan Wagner, Derek Ward-Thompson, John Wardle, Jasmin E. Washington, Jonathan Weintroub, Robert Wharton, Maciek Wielgus, Kaj Wiik, Gunther Witzel, Michael F. Wondrak, George N. Wong, Qingwen Wu, Nitika Yadlapalli, Paul Yamaguchi, Aristomenis Yfantis, Doosoo Yoon, André Young, Ziri Younsi, Wei Yu, Feng Yuan, Ye-Fei Yuan, J. Anton Zensus, Shuo Zhang, Guang-Yao Zhao, Shan-Shan Zhao","doi":"10.1051/0004-6361/202451296","DOIUrl":"https://doi.org/10.1051/0004-6361/202451296","url":null,"abstract":"The Event Horizon Telescope (EHT) observation of M87<sup>∗<sup/> in 2018 has revealed a ring with a diameter that is consistent with the 2017 observation. The brightest part of the ring is shifted to the southwest from the southeast. In this paper, we provide theoretical interpretations for the multi-epoch EHT observations for M87<sup>∗<sup/> by comparing a new general relativistic magnetohydrodynamics model image library with the EHT observations for M87<sup>∗<sup/> in both 2017 and 2018. The model images include aligned and tilted accretion with parameterized thermal and nonthermal synchrotron emission properties. The 2018 observation again shows that the spin vector of the M87<sup>∗<sup/> supermassive black hole is pointed away from Earth. A shift of the brightest part of the ring during the multi-epoch observations can naturally be explained by the turbulent nature of black hole accretion, which is supported by the fact that the more turbulent retrograde models can explain the multi-epoch observations better than the prograde models. The EHT data are inconsistent with the tilted models in our model image library. Assuming that the black hole spin axis and its large-scale jet direction are roughly aligned, we expect the brightest part of the ring to be most commonly observed 90 deg clockwise from the forward jet. This prediction can be statistically tested through future observations.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"33 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143020593","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":"Suppression of photospheric velocity fluctuations in strongly magnetic O stars in radiation-magnetohydrodynamic simulations","authors":"A. ud-Doula, J. O. Sundqvist, N. Narechania, D. Debnath, N. Moens, R. Keppens","doi":"10.1051/0004-6361/202452375","DOIUrl":"https://doi.org/10.1051/0004-6361/202452375","url":null,"abstract":"<i>Context<i/>. O stars generally show clear signs of strong line broadening (in addition to rotational broadening) in their photospheric absorption lines (typically referred to as macroturbulence), believed to originate in a turbulent sub-surface zone associated with enhanced opacities due to the recombination of iron-group elements (at <i>T<i/> ~ 150–200 kK). O stars with detected global magnetic fields also display such macroturbulence; the sole exception to this is NGC 1624-2, which also has the strongest (by far) detected field of the known magnetic O stars. It has been suggested that this lack of additional line broadening is due to NGC 1624-2’s exceptionally strong magnetic field, which might be able to suppress the turbulent velocity field generated in the iron opacity peak zone.<i>Aims<i/>. We tested this hypothesis based on two-dimensional (2D), time-dependent, radiation magnetohydrodynamical (RMHD) box- in-a-star simulations for O stars that encapsulate the deeper sub-surface atmosphere (down to T ~ 400 kK), the stellar photosphere, and the onset of the supersonic line-driven wind in one unified approach. To study the potential suppression of atmospheric velocity fluctuations, we extended our previous non-magnetic O star radiation-hydrodynamic (RHD) simulations to include magnetic fields of varying strengths and orientations.<i>Methods<i/>. We used MPI-AMRVAC, which is a Fortran 90 based publically available parallel finite volume code that is highly modular. We used the recently added RMHD module to perform all our simulations here.<i>Results<i/>. For moderately strong magnetic cases (~1 kG), the simulated atmospheres are highly structured and characterised by large root-mean-square velocities, and our results are qualitatively similar to those found in previous non-magnetic studies. By contrast, we find that a strong horizontal magnetic field in excess of 10 kG can indeed suppress the large velocity fluctuations, and can thus stabilise (and thereby also inflate) the atmosphere of a typical early O star in the Galaxy. On the other hand, an equally strong radial field is only able to suppress horizontal motions, and as a consequence these models exhibit significant radial fluctuations.<i>Conclusions<i/>. Our simulations provide an overall physical rationale as to why NGC 1624-2 with its strong ~20 kG dipolar field lacks the large macroturbulent line broadening that all other known slowly rotating early O stars exhibit. However, our simulations also highlight the importance of field geometry for controlling the atmospheric dynamics in massive and luminous stars that are strongly magnetic, tentatively suggesting latitudinal dependence of macroturbulence and basic photospheric parameters.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"33 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142991958","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":"Extragalactic globular cluster near-infrared spectroscopy","authors":"E. Eftekhari, A. Vazdekis, R. Riffel, L. G. Dahmer-Hahn, A. L. Chies-Santos, M. A. Beasley, A. Villaume, E. Zanatta","doi":"10.1051/0004-6361/202449571","DOIUrl":"https://doi.org/10.1051/0004-6361/202449571","url":null,"abstract":"Many recent studies have pointed out significant discrepancies between observations and models of stellar populations in the near-infrared (NIR). With current and future observing facilities being focused in this wavelength range, properly assessing and solving these issues is of utmost importance. Here, we present the first application of the extragalactic globular cluster (GC) near-infrared spectroscopy survey, and present evidence that these GCs reveal an age zero-point problem of stellar population synthesis (SPS) models. This problem has already been identified in the optical range for the GCs of the Milky Way. Such an issue arises when derived GC spectroscopic ages appear older than the Universe itself. We extend this discussion for the first time to the NIR, specifically using the Pa<i>β<i/> line at 1.28 microns. We focus on the GCs of the nearby Centaurus A galaxy using their NIR spectra. This work broadens our understanding of the age zero-point problem and emphasises the necessity to revisit and refine SPS models, especially in the NIR domain.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"74 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142992325","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":"Continuous evolution of the polarization properties in the transient X-ray pulsar RX J0440.9+4431/LS V +44 17","authors":"Q. C. Zhao, L. Tao, S. S. Tsygankov, A. A. Mushtukov, H. Feng, M. Y. Ge, H. C. Li, S. N. Zhang, L. Zhang","doi":"10.1051/0004-6361/202452872","DOIUrl":"https://doi.org/10.1051/0004-6361/202452872","url":null,"abstract":"We present a detailed time-resolved and phase-resolved polarimetric analysis of the transient X-ray pulsar RX J0440.9+4431/LS V +44 17, using data from the Imaging X-ray Polarimetry Explorer (IXPE) during the 2023 giant outburst. We conducted a time-resolved analysis by dividing the data into several intervals for each observation. This analysis reveals a continuous rotation of the phase-averaged polarization angle (PA) across the observations performed during the supercritical and subcritical regimes. To investigate the origin of the PA rotation, we performed a pulse phase-resolved polarimetric analysis over four time intervals, each spanning approximately three days. Applying the rotating vector model (RVM), the geometric parameters of the system were determined for each interval. Despite the short time gap of just ∼20 days, we observed significant variation in the RVM parameters between the first interval and the subsequent three, indicating the presence of an additional polarized component alongside the RVM component. Using a two-polarized component model with the assumption that this additional component remains constant across pulse phases, we calculated the phase-averaged PA and polarized flux of both the variable and constant components. The phase-averaged PA of each component remained relatively stable over time, but the polarized flux of the constant component decreased, while that of the variable component increased. The observed rotation of the PA is attributed to the gradual shift in the polarized flux ratio between the two components and is not directly related to the different accretion regimes.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"62 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142991956","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":"CRIRES+ transmission spectroscopy of WASP-127 b","authors":"L. Nortmann, F. Lesjak, F. Yan, D. Cont, S. Czesla, A. Lavail, A. D. Rains, E. Nagel, L. Boldt-Christmas, A. Hatzes, A. Reiners, N. Piskunov, O. Kochukhov, U. Heiter, D. Shulyak, M. Rengel, U. Seemann","doi":"10.1051/0004-6361/202450438","DOIUrl":"https://doi.org/10.1051/0004-6361/202450438","url":null,"abstract":"<i>Context<i/>. General circulation models of gas giant exoplanets predict equatorial jets that drive inhomogeneities in the atmospheric physical parameters across the planetary surface.<i>Aims<i/>. We studied the transmission spectrum of the hot Jupiter WASP-127 b during one transit in the <i>K<i/> band with CRIRES<sup>+<sup/>.<i>Methods<i/>. Telluric and stellar signals were removed from the data using SYSREM and the planetary signal was investigated using the cross-correlation technique. After detecting a spectral signal indicative of atmospheric inhomogeneities, we employed a Bayesian retrieval framework with a two-dimensional modelling approach tailored to address this scenario.<i>Results<i/>. We detected strong signals of H<sub>2<sub/>O and CO, which exhibited not one but two distinct cross-correlation peaks. The doublepeaked signal can be explained by a supersonic equatorial jet and muted signals at the planetary poles, with the two peaks representing the signals from the planet’s morning and evening terminators. We calculated an equatorial jet velocity of 7.7 ± 0.2 km s<sup>−1<sup/> from our retrieved overall equatorial velocity and the planet’s tidally locked rotation, and derive distinct atmospheric properties for the two terminators as well as the polar region. Our retrieval yields a solar C/O ratio and metallicity, and shows that the muted signals from the poles can be explained by either significantly lower temperatures or a high cloud deck. It provides tentative evidence for the morning terminator to be cooler than the evening terminator by −175<sub>−117<sub/><sup>+133<sup/> K.<i>Conclusions<i/>. Our detection of CO challenges previous non-detections of this species in WASP-127b’s atmosphere. The presence of a clear double-peaked signal highlights the importance of taking planetary three-dimensional structure into account during interpretation of atmospheric signals. The measured supersonic jet velocity and the lack of signal from the polar regions, representing a detection of latitudinal inhomogeneity in a spatially unresolved target, showcases the power of high-resolution transmission spectroscopy for the characterisation of global circulation in exoplanet atmospheres.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"38 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142992326","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":"Magnetic topology of quiet-Sun Ellerman bombs and associated ultraviolet brightenings","authors":"Aditi Bhatnagar, Avijeet Prasad, Luc Rouppe van der Voort, Daniel Nóbrega-Siverio, Jayant Joshi","doi":"10.1051/0004-6361/202452822","DOIUrl":"https://doi.org/10.1051/0004-6361/202452822","url":null,"abstract":"<i>Context.<i/> Quiet-Sun Ellerman bombs (QSEBs) are small-scale magnetic reconnection events in the lower atmosphere of the quiet Sun. Recent work has shown that a small percentage of them can occur co-spatially and co-temporally with ultraviolet (UV) brightenings in the transition region.<i>Aims.<i/> We aim to understand how the magnetic topologies associated with closely occurring QSEBs and UV brightenings can facilitate energy transport and connect these events.<i>Methods.<i/> We used high-resolution H<i>β<i/> observations from the Swedish 1-m Solar Telescope (SST) and detected QSEBs using <i>k<i/>-means clustering. We obtained the magnetic field topology from potential field extrapolations using spectro-polarimetric data in the photospheric Fe I 6173 Å line. To detect UV brightenings, we used coordinated and co-aligned data from the Interface Region Imaging Spectrograph (IRIS) and imposed a threshold of 5<i>σ<i/> above the median background on the (IRIS) 1400 Å slit-jaw image channel.<i>Results.<i/> We identify four distinct magnetic configurations that associate QSEBs with UV brightenings, including a simple dipole configuration and more complex fan-spine topologies with a 3D magnetic null point. In the fan-spine topology, the UV brightenings occur near the 3D null point, while QSEBs can be found close to the footpoints of the outer spine, the inner spine, and the fan surface. The height of the 3D null varies between 0.2 Mm and 2.6 Mm, depending on the magnetic field strength in the region. Some QSEBs and UV brightenings, though occurring close to each other, are not topologically connected with the same reconnection process. The energy released during QSEBs falls in the range 10<sup>23<sup/>–10<sup>24<sup/> ergs.<i>Conclusions.<i/> This study shows that magnetic connectivity and topological features, such as 3D null points, are crucial in linking QSEBs in the lower atmosphere with UV brightenings in the transition region.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"101 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990127","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":"Molecular chemistry induced by a J-shock toward supernova remnant W51C","authors":"Tian-Yu Tu, Valentine Wakelam, Yang Chen, Ping Zhou, Qian-Qian Zhang","doi":"10.1051/0004-6361/202452270","DOIUrl":"https://doi.org/10.1051/0004-6361/202452270","url":null,"abstract":"<i>Context.<i/> Shock waves from supernova remnants (SNRs) strongly affect the physical and chemical properties of molecular clouds (MCs). Shocks propagating into magnetized MCs can be classified into jump or J-shocks and continuous or C-shocks. The molecular chemistry in the re-formed molecular gas behind J-shocks is still only poorly understood. It is expected to provide a comprehensive view of the chemical feedback of SNRs and the chemical effects of J-shocks.<i>Aims.<i/> We conducted a <i>W<i/>-band (71.4–89.7 GHz) observation toward a re-formed molecular clump behind a J-shock induced by SNR W51C with the Yebes 40 m radio telescope to study the molecular chemistry in the re-formed molecular gas.<i>Methods.<i/> Assuming local thermodynamic equilibrium (LTE), we estimated the column densities of HCO<sup>+<sup/>, HCN, C<sub>2<sub/>H and <i>o<i/>-<i>c<i/>-C<sub>3<sub/>H<sub>2<sub/>, and derived their abundance ratio maps with CO. The gas density was constrained by a non-LTE analysis of the HCO<sup>+<sup/> <i>J<i/> = 1–0 line. The abundance ratios were compared with the values in typical quiescent MCs and shocked MCs, and they were also compared with the results of chemical simulations with the Paris-Durham shock code to verify and investigate the chemical effects of J-shocks.<i>Results.<i/> We obtained the following abundance ratios: <i>N<i/>(HCO<sup>+<sup/>)/<i>N<i/>(CO) ~ (1.0–4.0) × 10<sup>−4<sup/>, <i>N<i/>(HCN)/<i>N<i/>(CO) ~ (1.8–5.3) × 10<sup>−4<sup/>, <i>N<i/>(C<sub>2<sub/>H)/<i>N<i/>(CO) ~ (1.6–5.0) × 10<sup>−3<sup/>, and <i>N<i/>(<i>o<i/>-<i>c<i/>-C<sub>3<sub/>H<sub>2<sub/>)/<i>N<i/>(CO) ~ (1.2–7.9) × 10<sup>−4<sup/>. The non-LTE analysis suggests that the gas density is <i>n<i/><sub>H<sub>2<sub/><sub/> ≳ 10<sup>4<sup/> cm<sup>−3<sup/>. We find that the <i>N<i/>(C<sub>2<sub/>H)/<i>N<i/>(CO) and <i>N<i/>(<i>o<i/>-<i>c<i/>-C<sub>3<sub/>H<sub>2<sub/>)/<i>N<i/>(CO) are higher than typical values in quiescent MCs and shocked MCs by 1–2 orders of magnitude, which can be qualitatively attributed to the abundant C<sup>+<sup/> and C in the earliest phase of molecular gas re-formation. The Paris-Durham shock code can reproduce, although not perfectly, the observed abundance ratios, especially the enhanced <i>N<i/>(C<sub>2<sub/>H)/<i>N<i/>(CO) and <i>N<i/>(<i>c<i/>-C<sub>3<sub/>H<sub>2<sub/>)/<i>N<i/>(CO), with J-shocks propagating into both nonirradiated and irradiated molecular gas with a preshock density of <i>n<i/><sub>H<sub/> = 2 × 10<sup>3<sup/> cm<sup>−3<sup/>.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"77 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142989676","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 puzzle of isolated and quenched dwarf galaxies in cosmic voids","authors":"Bahar Bidaran, Isabel Pérez, Laura Sánchez-Menguiano, María Argudo-Fernández, Anna Ferré-Mateu, Julio F. Navarro, Reynier F. Peletier, Tomás Ruiz-Lara, Glenn van de Ven, Simon Verley, Almudena Zurita, Salvador Duarte Puertas, Jesús Falcón-Barroso, Patricia Sánchez-Blázquez, Andoni Jiménez","doi":"10.1051/0004-6361/202452688","DOIUrl":"https://doi.org/10.1051/0004-6361/202452688","url":null,"abstract":"We report, for the first time, the detection of a sample of quenched and isolated dwarf galaxies (with 8.9 < log(M<sub>⋆<sub/>/M<sub>⊙<sub/>) < 9.5) in the least dense regions of the cosmic web, including voids, filaments, and walls. These dwarfs have no neighboring galaxy within 1.0 Mpc in projected distance. Based on the full spectral fitting of their central spectra using Sloan Digital Sky Survey data, these galaxies are gas-deprived, while also exhibiting a stellar mass assembly very similar to dwarfs in the central regions of galaxy clusters. Furthermore, they have experienced no significant star formation in the past 2 Gyr. Additionally, analyses of <i>r<i/>-band images from the Dark Energy Camera Legacy Survey have shown that these dwarf galaxies host a central nuclear star cluster (NSC). Detecting quenched, isolated dwarf galaxies in cosmic voids indicates that environmental factors are not the sole drivers of their quenching. Internal mechanisms, such as feedback from in situ star formation, which also contribute to the NSC formation, along with black holes or variations in the conditions around their formation, offer potential explanations for star formation suppression in these galaxies. These findings highlight the need for a significant revision in our understanding of baryonic physics, particularly concerning the formation and evolution of low-mass galaxies.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"5 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990122","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":"Superbubbles as the source of dynamical friction: Gas migration, and stellar and dark matter contributions","authors":"Rain Kipper, Indrek Vurm, Aikaterini Niovi Triantafyllaki, Peeter Tenjes, Elmo Tempel","doi":"10.1051/0004-6361/202450564","DOIUrl":"https://doi.org/10.1051/0004-6361/202450564","url":null,"abstract":"The gas distribution in galaxies is smooth on large scales, but is usually time-dependent and inhomogeneous on smaller scales. The time-dependence originates from processes such as cloud formation, their collisions, and supernovae (SNe) explosions, which also create inhomogeneities. The inhomogeneities in the matter distribution give rise to variations in the local galactic gravitational potential, which can contribute to dynamically coupling the gas disc to the stellar and the dark matter (DM) components of the galaxy. Specifically, multiple SNe occurring in young stellar clusters give rise to superbubbles (SBs), which modify the local acceleration field and alter the energy and momentum of stars or DM particles traversing them, in broad analogy to the dynamical friction caused by a massive object. Our aim is to quantify how the acceleration field from SBs causes dynamical friction and contributes to the secular evolution of galaxies. In order to assess this, we constructed the time-dependent density modifications to the gas distribution that mimics a SB. By evaluating the acceleration field from these density modifications, we were able to see how the momentum or angular momentum of the gas hosting the SBs changes when stars pass through the SB. Combining the effects of all the stars and SBs, we constructed an empirical approximation formula for the momentum loss in homogeneous and isotropic cases. We find that the rate at which the gas disc loses its specific angular momentum via the above process is up to 4% per Gyr, which translates to under one-half of its original value over the lifetime of the disc. For comparison, the mass transfer rate from SBs is about one order of magnitude less than from gas turbulence, and hence the SB contribution should be included to account for the gas migration rate more accurately than 10%. Finally, we studied how the dynamical coupling of the gas disc with the DM halo depends on assumptions on the halo kinematics (e.g. rotation) and found a ∼0.3% variation in the gas disc secular evolution between different DM kinematic models.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"74 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142990123","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":"Non-local thermodynamic equilibrium (NLTE) abundances of europium (Eu) for a sample of metal-poor stars in the galactic halo and metal-poor disk with 1D and 〈3D〉 models","authors":"Yanjun Guo, Nicholas Storm, Maria Bergemann, Jianhui Lian, Sofya Alexeeva, Yangyang Li, Rana Ezzeddine, Gerber Jeffrey, XueFei Chen","doi":"10.1051/0004-6361/202451536","DOIUrl":"https://doi.org/10.1051/0004-6361/202451536","url":null,"abstract":"<i>Context<i/>. As a key to chemical evolutionary studies, the distribution of elements in galactic provides a wealth of information to understand the individual star formation histories of galaxies. The r-process is a complex nucleosynthesis process, and the origin of r-process elements is heavily debated. Europium (Eu) is viewed as an almost pure r-process element. Accurate measurements of europium abundances in cool stars are essential for an enhanced understanding of the r-process mechanisms.<i>Aims<i/>. We measure the abundance of Eu in solar spectra and a sample of metal-poor stars in the Galactic halo and metal-poor disk, with the metallicities ranging from −2.4 to −0.5 dex, using non-local thermodynamic equilibrium (NLTE) line formation. We compare these measurements with Galactic Chemical Evolution (GCE) models to explore the impact of the NLTE corrections on the contribution of r-process site in Galactic chemical evolution.<i>Methods<i/>. In this work, we used NLTE line formation, as well as one-dimensional (1D) hydrostatic and spatial averages of three-dimensional hydrodynamical (<3D>) model atmospheres to measure the abundance of Eu based on both the Eu II 4129 Å and Eu II 6645 Å lines for solar spectra and metal-poor stars.<i>Results<i/>. We find that for Eu II 4129 Å line the NLTE modeling leads to higher (0.04 dex) solar Eu abundance in 1D and higher (0.07 dex) in <3D> NLTE while NLTE modeling leads to higher (0.01 dex) solar Eu abundance in 1D and lower (0.03 dex) in <3D> NLTE for Eu II 6645 Å line. Although the NLTE corrections for the Eu II <i>λ<i/> 4129 Å and Eu II λ 6645 Å lines are opposite, the discrepancy between the abundances derived from these individual lines reduces after applying NLTE corrections, highlighting the critical role of NLTE abundance determinations. By comparing these measurements with Galactic chemical evolution (GCE) models, we find that the amount of NLTE correction does not require significant change of the parameters for Eu production in GCE models.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"70 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142989675","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}