Astronomy & Astrophysics最新文献

{"title":"Dust in the wind of outbursting young stars","authors":"Kundan Kadam, Eduard Vorobyov, Peter Woitke, Manuel Güdel","doi":"10.1051/0004-6361/202554021","DOIUrl":"https://doi.org/10.1051/0004-6361/202554021","url":null,"abstract":"<i>Context.<i/> Young stellar objects (YSOs) have been observed to undergo powerful accretion events known as FU Orionis outbursts (FUors). These types of episodic accretion events are now considered to be commonplace during low-mass star formation, wherein accretion onto the protostar occurs through a surrounding centrifugal disk. Increasing evidence suggests that the magnetic disk winds are crucial for driving disk accretion, as they carry both mass and momentum away from the disk.<i>Aims.<i/> We aim to investigate the phenomenon of the ejection of magnetic disk winds during episodic accretion, with a focus on the dust contained within these winds.<i>Methods.<i/> We conducted magnetohydrodynamic (MHD) simulations of the formation and evolution of a protoplanetary disk (PPD) in the thin-disk limit. We included the evolution of dust with two populations and a realistic prescription for viscosity during outbursts, which depends on the local thermal ionization fraction. The disk evolves with the concurrent action of viscosity, self-gravity, and magnetic disk winds.<i>Results.<i/> The simulated disk exhibits outbursting behavior in the early stages, with the duration and frequency of the bursts, their rise times, and brightness amplitudes resembling the properties observed for FUors. We find that during the outbursts, the winds are over an order of magnitude more dusty, as compared to in quiescence. However, despite this increased dust content, the winds are still dust-depleted as the dust-to-gas ratio is about an order of magnitude lower than the canonical interstellar value of 0.01. The results of our numerical experiments are in general agreement with the available observational findings, shedding light on the mechanism behind the production of dusty winds during outbursting events in YSOs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"35 1","pages":"A43"},"PeriodicalIF":6.5,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143910272","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":"Impact of T- and ρ-dependent decay rates and new (n,γ) cross-sections on the s process in low-mass asymptotic giant branch stars","authors":"B. Szányi, A. Yagüe López, A. I. Karakas, M. Lugaro","doi":"10.1051/0004-6361/202453089","DOIUrl":"https://doi.org/10.1051/0004-6361/202453089","url":null,"abstract":"<i>Aims.<i/> We study the impact of nuclear input related to weak-decay rates and neutron-capture reactions on predictions for the slow neutron-capture process (<i>s<i/> process) in asymptotic giant branch (AGB) stars. We provide the first database of surface abundances and stellar yields of the isotopes heavier than iron from the Monash models.<i>Methods.<i/> We ran nucleosynthesis calculations with the Monash post-processing code for seven stellar structure evolution models of low-mass AGB stars with three different sets of nuclear inputs. The reference set has constant decay rates and represents the set used in the previous Monash publications. The second set contains the temperature and density dependence of <i>β<i/> decays and electron captures based on the default rates of nuclear NETwork GENerator (NETGEN). In the third set, we further update 92 neutron-capture rates based on re-evaluated experimental cross sections from the ASTrophysical Rate and rAw data Library. We compare and discuss the predictions of the sets relative to each other in terms of isotopic surface abundances and total stellar yields. We also compare the results to isotopic ratios measured in presolar stardust silicon carbide (SiC) grains from AGB stars.<i>Results.<i/> The new sets of models result in a ∼66% solar <i>s<i/>-process contribution to the <i>p<i/>-nucleus <sup>152<sup/>Gd, confirming that this isotope is predominantly made by the <i>s<i/> process. The nuclear input updates result in predictions for the <sup>80<sup/>Kr/<sup>82<sup/>Kr ratio in the He intershell and surface <sup>64<sup/>Ni/<sup>58<sup/>Ni, <sup>94<sup/>Mo/<sup>96<sup/>Mo, and <sup>137<sup/>Ba/<sup>136<sup/>Ba ratios that are more consistent with the corresponding ratios measured in stardust; however, the new predicted <sup>138<sup/>Ba/<sup>136<sup/>Ba ratios are higher than the typical values of the SiC grains. The W isotopic anomalies are in agreement with data from the analyses of other meteoritic inclusions. We confirm that the production of <sup>176<sup/>Lu and <sup>205<sup/>Pb is affected by too large uncertainties in their decay rates from NETGEN.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"20 1","pages":"A48"},"PeriodicalIF":6.5,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143910286","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":"Combining high-contrast imaging with high-resolution spectroscopy: Actual on-sky MIRI/MRS results compared to expectations","authors":"S. Martos, A. Bidot, A. Carlotti, D. Mouillet","doi":"10.1051/0004-6361/202453382","DOIUrl":"https://doi.org/10.1051/0004-6361/202453382","url":null,"abstract":"&lt;i&gt;Context.&lt;i/&gt; Combining high-contrast imaging with high-resolution spectroscopy represents a powerful approach to detecting and characterizing exoplanets around nearby stars, despite the challenges posed by their faintness. Instruments like VLT/SPHERE represent the state of the art in high-contrast imaging; however, their spectral resolution (&lt;i&gt;R&lt;i/&gt; ≈ 50) limits them to basic characterization of close companions. These instruments can observe planets with masses as low as 5–10 M&lt;sub&gt;Jup&lt;sub/&gt; at distances of around 10 AU from their stars. Detection limits are primarily constrained by speckle noise, which dominates over photon and detector noise at short separations around bright stars, even when advanced differential imaging techniques are used. Similarly, image stability also limits space-based high-contrast imaging capability. This speckle noise can, however, be largely mitigated by molecular mapping, a more recent method that leverages information from high-resolution spectroscopic data.&lt;i&gt;Aims.&lt;i/&gt; Our objective is to understand and predict the effective detection limits associated with spectro-imaging data after processing with molecular mapping. This involves analyzing the propagation of fundamental noise sources, such as photon and detector noise, and comparing these predictions to real instrument data to assess performance losses due to instrument-based factors. Our goal is to identify and propose potential mitigation strategies for these additional sources of noise. Another key aim is to compare the predictions made by our analytical approach with actual observational data to validate and refine the model’s accuracy where necessary.&lt;i&gt;Methods.&lt;i/&gt; We analyzed JWST/MIRI/MRS data using the recently developed semi-analytical and numerical tool, FastCurves, and compared the results with outputs from the end-to-end MIRI simulator. This simulator allows one to examine nonideal instrumental effects in detail. Additionally, we applied principal component analysis (PCA), a statistical method that identifies correlated patterns in the data, to help isolate systematic effects, both with and without molecular mapping.&lt;i&gt;Results.&lt;i/&gt; Our analysis involves investigating the systematic effects introduced by the instrument, identifying their origins, and evaluating their impact on both noise and signal. We show that valuable insights are gained regarding the effects of straylight, fringes, and aliasing artifacts, each linked to different residual systematic noise terms in the data. The results are further supported by principal component analysis, which also demonstrates its effectiveness in mitigating these effects. Additionally, we explore the similarities and discrepancies between observed and modeled companion spectra from an astronomical perspective.&lt;i&gt;Conclusions.&lt;i/&gt; We modified FastCurves to account for systematic effects and improve its modeling of MIRI/MRS noise, with its signal-to-noise predictions validated against empirical data. In hig","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"99 1","pages":"A27"},"PeriodicalIF":6.5,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143910425","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":"Enigmatic diffuse ionized gas structures in a cluster of galaxies near cosmic noon","authors":"C. Maier, B. L. Ziegler, T. Kodama","doi":"10.1051/0004-6361/202554203","DOIUrl":"https://doi.org/10.1051/0004-6361/202554203","url":null,"abstract":"We explore the massive cluster XMMXCS J2215.9-1738 at <i>z<i/> ∼ 1.46 with MUSE and KMOS integral field spectroscopy. Using MUSE spectroscopy, we traced the kinematics of the ionized gas using [O II] <i>λλ<i/> 3726, 3729 in the central 500 × 500 kpc<sup>2<sup/> area of the cluster, which contains 28 spectroscopically identified cluster galaxies. We detected [O II] <i>λλ<i/> 3726, 3729 emission lines in the integrated spectra of 21 galaxies. The remaining seven are passive galaxies. Six of these passive galaxies lie in the central part of the cluster, which has a diameter of 200 kpc and contains no star-forming objects. In this place, star formation in galaxies is quenched. An interesting discovery in this central area of the cluster are three diffuse ionized [O II] <i>λλ<i/> 3726, 3729 gas structures, which we refer to as [OII] blobs. They extend over areas of some hundred kpc<sup>2<sup/>. The ionization source of one of the gaseous structures that displays two prominent filamentary patterns indicating outflow of gas is an active galactic nucleus (AGN). The KMOS data enabled us to use the BPT diagram to identify this object as a type 2 AGN. The other two diffuse ionized oxygen gaseous structures are more enigmatic. They are located between the stellar components of passive cluster galaxies. One of these blobs lacks a stellar counterpart in the HST optical and near-infrared data, and the other blob has only a very faint counterpart. Ram-pressure stripping of photoionized gas or AGN feedback might be an explanation. Additionally, the galaxy velocity distribution in this high-redshift cluster is bimodal, which indicates that the cluster is probably not fully virialized and that recent and ongoing merging events that produced shocks might provide photoionization sources for the two enigmatic [OII] blobs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"12 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143898209","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 manifest link between Terzan 5 and the Galactic bulge","authors":"L. Origlia, F. R. Ferraro, C. Fanelli, B. Lanzoni, D. Massari, E. Dalessandro, C. Pallanca","doi":"10.1051/0004-6361/202452110","DOIUrl":"https://doi.org/10.1051/0004-6361/202452110","url":null,"abstract":"We address the chemical link between Terzan 5 (hereafter Ter5) and the Galactic bulge, as probed by the observed distributions of [<i>α<i/>/Fe] abundance ratios with varying [Fe/H] and by suitable statistical tests to evaluate their significance. We also present a comprehensive review of the kinematic and evolutionary properties of Ter5, based on all the available observational signatures and the scenarios proposed so far in the literature for the formation and evolution of Ter5, as well as on the recent modelling of its star formation and chemical enrichment history. This analysis confirms the complex nature of this massive stellar system, with robust evidence of in situ bulge formation and of a subsequent evolution that cannot be simply explained by a single merging and/or accretion event of two globulars or a globular and a giant molecular cloud, as has been proposed in the literature, but it requires a more complex star formation likely accompanied by some self-enrichment.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143893778","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":"Abundances of refractory ions in Beta Pictoris exocomets","authors":"T. Vrignaud, A. Lecavelier des Etangs, P. A. Strøm, F. Kiefer","doi":"10.1051/0004-6361/202453568","DOIUrl":"https://doi.org/10.1051/0004-6361/202453568","url":null,"abstract":"<i>β<i/> Pictoris is a young A5V star known for harbouring a large number of cometary-like objects (or exocomets) that frequently transit the star and create variable absorption signatures in its spectrum. The physical and chemical properties of these exocomets can be probed by the recently introduced curve of growth approach, which enables column densities measurements in cometary tails using absorption measurements in numerous spectral lines. Through this approach, we present a new study of archival spectra of <i>β<i/> Pic obtained with the <i>Hubble<i/> Space Telescope, the HARPS spectrograph, and at the Mont John University Observatory aimed at constraining the abundance of refractory ions in <i>β<i/> Pic exocomets. We studied 29 individual objects, all of which were observed in Fe II lines (used as a reference ion) and at least one other species (e.g. Ni II, Ca II, Cr II). We find that the refractory composition of <i>β<i/> Pic exocomets is stable overall, especially for singly ionised species, and consistent with solar abundances. This outcome validates the use of the curve of growth approach to study exocometary composition. We also show that some ions, such as Ca II, are significantly depleted compared to solar abundances, which allowed us to constrain the typical ionisation state in <i>β<i/> Pic exocomets. We find that most refractory elements (e.g. Mg, Ni, Fe) are split into similar fractions between their first and second ionisation states, with the exception of Ca, which is mostly ionised twice. A strong correlation between the Al III/Fe II ratio and radial velocity is also found, showing that the most redshifted exocomets tend to be more ionised. These results open the way for further modelling of exocomets in order to unveil their composition and the physical processes that affect their tails.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"34 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143893843","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 multi-scale investigation into the diagnostic potential of the HCN/HCO+ ratio for active galactic nucleus and starburst activity in nearby galaxies","authors":"J. Butterworth, S. Viti, Y. Wang","doi":"10.1051/0004-6361/202453357","DOIUrl":"https://doi.org/10.1051/0004-6361/202453357","url":null,"abstract":"<i>Context.<i/> The identification of active galactic nuclei (AGNs) and starburst (SB) regions in galaxies is crucial for understanding the role of various physical processes in galaxy evolution. Molecular line ratios, such as the HCN/HCO<sup>+<sup/> ratio, have been proposed as potential tracers of these distinct environments.<i>Aims.<i/> We aim to assess the reliability of the HCN/HCO<sup>+<sup/> ratio, from J = 1–0 to J = 4–3 transitions, as a diagnostic tool for differentiating AGN and SB activity across a diverse sample of nearby galaxies. We focus on evaluating the effect of spatial resolution on the robustness of these ratios and investigate the underlying physical conditions that drive observed variations.<i>Methods.<i/> We compiled observations of HCN and HCO<sup>+<sup/> lines across multiple J transitions from various sources, covering different galaxy types, including Seyferts, SBs, and (ultra-)luminous infrared galaxies. The observations span spatial scales from cloud-sized regions (tens of parsecs) to kiloparsec scales. We analysed the behaviour of these ratios at varying resolutions and employed non-local thermodynamic equilibrium (non-LTE) radiative transfer models to infer the physical conditions that drive the observed ratios.<i>Results.<i/> We find that the HCN/HCO<sup>+<sup/> ratio from higher J transitions (e.g. J = 4–3) can differentiate between AGN and SB activity when observed at high spatial resolution (< 100 pc). This distinction occurs around unity, with HCN/HCO < 1 observed in SB-dominated and > 1 in AGN-dominated regions. However, at lower resolutions, contamination from multiple emission sources and beam averaging effects destroy these distinctions. Radiative transfer modelling suggests that elevated HCN/HCO<sup>+<sup/> ratios in AGN-dominated regions are largely driven by an increase in HCN abundance relative to HCO<sup>+<sup/>, likely due to high-temperature chemistry or increased excitation.<i>Conclusions.<i/> Our study confirms that the HCN/HCO<sup>+<sup/> ratio, particularly of higher J transitions, can be a reliable tracer of AGN versus SB activity if observations are conducted at sufficiently high spatial resolution. However, caution must be exercised in interpreting these ratios at larger spatial scales due to contamination effects. Further high-resolution observations are needed to refine the conditions under which these ratios can serve as reliable diagnostics.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"21 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143894036","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 dust polarisation and magnetic field structure in the centre of NGC253 with ALMA","authors":"Davide Belfiori, Rosita Paladino, Annie Hughes, Jean-Philippe Bernard, Dana Alina, Ivana Bešlić, Enrique Lopez Rodriguez, Mark D. Gorski, Serena A. Cronin, Alberto D. Bolatto","doi":"10.1051/0004-6361/202451615","DOIUrl":"https://doi.org/10.1051/0004-6361/202451615","url":null,"abstract":"<i>Context.<i/> Magnetic fields (B fields) have an impact on galaxy evolution on multiple scales. They are particularly important for starburst galaxies, where they play a crucial role in shaping the interstellar medium (ISM), influencing star formation processes and interacting with galactic outflows.<i>Aims.<i/> The primary aim of this study is to obtain a parsec-scale map of the dust polarisation and B field structure within the central starburst region of NGC253. This includes examining the relationship between the morphology of B fields, galactic outflows, and the spatial distribution of super starclusters (SSCs), to understand their combined effects on the galaxy’s star formation and ISM.<i>Methods.<i/> We used ALMA full polarisation data in Bands 4 (∼145 GHz) and 7 (∼345 GHz) with a resolution of ∼25 and ∼5 pc scale, respectively. The Stokes <i>I<i/>, <i>Q<i/>, and <i>U<i/> maps of the two bands have been used to compute the polarised intensity (<i>PI<i/>), polarisation fraction (<i>PF<i/>), B field orientation on the plane of the sky, and dispersion angle function (𝒮) maps. We computed the pixel-by-pixel uncertainties of these maps taking into account the covariance between the Stokes parameters <i>I<i/>, <i>Q<i/>, and <i>U<i/>. The uncertainty allowed us to detect values of <i>PF<i/> as low as ∼0.1% with a S/N (signal-to-noise ratio) greater than 3. Through a spectral energy distribution (SED)-fitting analysis including archival data, we investigated the main emitting components that contribute to the total and polarised emission in several areas of the starburst region.<i>Results.<i/> According to our SED-fitting analysis, the observed Band 4 emission is a combination of dust, synchrotron, and free-free components, while Band 7 traces only dust. The <i>PF<i/> of the synchrotron component measures ∼2%, while that of the dust component is ∼0.3%. The B field orientation maps in both bands at a common resolution show that the same B field structure is traced by dust and synchrotron emission at scales ∼25 pc. The B field morphology suggests a coupling with the multiphase outflow, while the distribution of <i>PF<i/> in Band 7 shows to be correlated with the presence of SSCs. We observed a significant anti-correlation between <i>PF<i/> and column density in both Bands 4 and 7. A negative correlation between <i>PF<i/> and 𝒮 was observed in Band 4 but was nearly absent in Band 7 at a native resolution, suggesting that the tangling of B field geometry along the plane of the sky is the main cause of depolarisation at ∼25 pc scales, while other factors play a role at ∼5 pc scales.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"10 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143893780","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":"Periodic variations in the first and second moments of broad Balmer emission lines from central accretion disks","authors":"XueGuang Zhang","doi":"10.1051/0004-6361/202554136","DOIUrl":"https://doi.org/10.1051/0004-6361/202554136","url":null,"abstract":"Broad emission line regions (BLRs) lying in central accretion disks are widely accepted to explain the unique double-peaked broad emission lines in active galactic nuclei (double-peaked BLAGNs). Accepting the accretion disk origin, we theoretically simulated and determined the periodic variations in the central wavelength <i>λ<i/><sub>0<sub/> (the first moment) and line width <i>σ<i/> (the second moment) of double-peaked broad emission lines. Furthermore, through theoretically simulated periodicities of <i>T<i/><sub><i>λ<i/>0<sub/> and <i>T<i/><sub><i>σ<i/><sub/> for variations in <i>λ<i/><sub>0<sub/> and <i>σ<i/>, a periodicity ratio <i>R<i/><sub><i>fs<i/><sub/> of <i>T<i/><sub><i>λ<i/>0<sub/> to <i>T<i/><sub><i>σ<i/><sub/> of about 2 was applied to support the hypothesis that the spiral arms are preferred in BLRs in central accretion disks. Then, we determined the periodic variations in <i>λ<i/><sub>0<sub/> and <i>σ<i/> and showed them in the known double-peaked BLAGN NGC 1097. This led to the parameter <i>R<i/><sub><i>fs<i/><sub/> ∼ 2, which can be applied as a clue to support the hypothesis that the spiral arm structure in disk-like BLRs in the central accretion disk is the most compelling interpretation of the variability in the double-peaked broad H<i>α<i/> in NGC 1097. The results provide clean criteria for testing the accretion disk origins of double-peaked broad emission lines in AGN.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"38 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143884396","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":"Positive feedback: How a synergy between the streaming instability and dust coagulation forms planetesimals","authors":"Daniel Carrera, Jeonghoon Lim, Linn E. J. Eriksson, Wladimir Lyra, Jacob B. Simon","doi":"10.1051/0004-6361/202554100","DOIUrl":"https://doi.org/10.1051/0004-6361/202554100","url":null,"abstract":"<i>Context.<i/> One of the most important open questions in planet formation is how dust grains in a protoplanetary disk manage to overcome growth barriers and form the ∼100 km planet building blocks that we call planetesimals. There appears to be a gap between the largest grains that can be produce by coagulation, and the smallest grains that are needed for the streaming instability (SI) to form planetesimals.<i>Aims.<i/> Here we explore the novel hypothesis that dust coagulation and the SI work in tandem; in other words, they form a feedback loop where each one boosts the action of the other to bridge the gap between dust grains and planetesimals.<i>Methods.<i/> We developed a semi-analytical model of dust concentration due to the SI, and an analytic model of how the SI affects the fragmentation and radial drift barriers. We then combined them to model our proposed feedback loop.<i>Results.<i/> In the fragmentation-limited regime, we find a powerful synergy between the SI and dust growth that drastically increases both grain sizes and densities. We find that a midplane dust-to-gas ratio of <i>ϵ<i/> ≥ 0.3 is a sufficient condition for the feedback loop to reach the planetesimal-forming region for turbulence values 10<sup>−4<sup/> ≤ <i>α<i/> ≤ 10<sup>−3<sup/> and grain sizes 0.01 ≤ St ≤ 0.1. In contrast, the drift-limited regime only shows grain growth without significant dust accumulation. In other words, planetesimal formation remains challenging in the drift-dominated regime and dust traps may be required to allow planet formation at wide orbital distances.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"53 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143884553","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}