Astronomy & Astrophysics最新文献

{"title":"Protostellar Outflows at the EarliesT Stages (POETS)","authors":"L. Moscadelli, C. Goddi, T. Hirota, A. Sanna","doi":"10.1051/0004-6361/202553842","DOIUrl":"https://doi.org/10.1051/0004-6361/202553842","url":null,"abstract":"<i>Context<i/>. The hyper-compact (HC) HII region phase of a newly born massive star is presently poorly understood, particularly in relation to how the enhanced UV radiation impacts the kinematics of the surrounding gas and affects mass accretion.<i>Aims<i/>. This article focuses on NGC 7538 IRS1, one of the most luminous and studied HC HII regions in the northern hemisphere. Our aim is to identify the young stellar objects (YSOs) embedded within the ionized gas and study their nearby kinematic structures. This work expands on a recent survey called Protostellar Outflows at the EarliesT Stages (POETS), which has been devoted to studying young outflow emission on scales of 10–100 au near luminous YSOs, before they start photoionizing the surrounding medium.<i>Methods<i/>. We carried out multi-epoch Very Long Baseline Array (VLBA) observations of the 22 GHz water masers toward NGC 7538 IRS1 to measure the maser 3D velocities, which, following POETS’ findings, are reliable tracers of the protostellar winds. Recently, we reobserved the water masers in NGC 7538 IRS1 with sensitive global very long baseline interferometry (VLBI) observations to map weaker maser emission and also study the maser time variability.<i>Results<i/>. Our study confirms the presence of two embedded YSOs, IRS1a and IRS1b, at the center of the two linear distributions of 6.7 GHz methanol masers observed in the southern and northern cores of the HC HII region, which have been previously interpreted in terms of edge-on rotating disks. The water masers trace an extended (≥200 au) stationary shock front adjacent to the inner portion of the disk around IRS1a. This shock front corresponds to the edge of the southern tip of the ionized core and might be produced by the interaction of the disk wind ejected from IRS1a with the infalling envelope. The water masers closer to IRS1b follow the same local standard of rest (LSR) velocity (<i>V<i/><sub>LSR<sub/>) pattern of the 6.7 GHz masers rotating in the disk, but the direction and amplitude of the water maser proper motions are inconsistent with rotation. We propose that these water masers are tracing a photo-evaporated disk wind, where the maser <i>V<i/><sub>LSR<sub/> traces mainly the disk rotation and the proper motions the poloidal velocity of the wind. Finally, a sensitive NSF’s Karl G. Jansky Very Large Array (JVLA) 1.3 cm image of the HC HII region obtained from archival data reveals a disk-jet system, illuminated by the UV radiation from IRS1a, associated with an YSO, IRS1c, placed ≈0<sup>′′<sup/>.5 (or ≈1350 au) to the south of the ionized core.<i>Conclusions<i/>. This work shows that VLBI observations of the 22 GHz water masers can be used to trace disk winds near ionizing YSOs embedded within compact HII regions.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"183 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745488","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":"3D shape models for describing monolithic asteroids and meteoroids","authors":"David Čapek, Michal Petřík, Jiří Pachman, Erkai Watson, Jakub Haloda, Robert Macke, Tomáš Henych, Pavel Koten, Martin Schimmerohn, Zuzana Stravová, Tomáš Zikmund, Jozef Kaiser","doi":"10.1051/0004-6361/202452886","DOIUrl":"https://doi.org/10.1051/0004-6361/202452886","url":null,"abstract":"<i>Context.<i/> Detailed knowledge of shapes is necessary for modeling certain processes affecting small Solar System bodies, such as the influence of radiative effects – like the YORP effect – on rotation. For meteoroids and small monolithic asteroids, such shapes have not been available up till now. This has strongly limited the possibilities of theoretical studies of the non-gravitational phenomena acting on these bodies.<i>Aims.<i/> Our goal is to create a database of digital 3D shape models that would be suitable for describing the shapes of meteoroids and small monolithic asteroids.<i>Methods.<i/> We performed catastrophic disruption experiments on samples from L3-6 ordinary chondrite NWA 869 and terrestrial tephriphonolite, including one hypervelocity impact and two explosion experiments. We selected fragments with masses of <i>m<i/> ≥ 0.2 g that originated from the interior of the samples and did not contain the original target surface. Their size range is approximately 5–24 mm. Their shapes were digitized using X-ray computed tomography, with voxel sizes of about 50 µm.<i>Results.<i/> The resulting database contains 868 shape models in Wavefront OBJ format, as well as a list of the basic properties of each one. The numbers of triangular surface facets of these models range from ∼20 000 to ∼760 000. These shape models correspond to meteoroids and small asteroids created by hypervelocity collisions. When using this database for a particular purpose, it is necessary to consider the selection of appropriate models based on the absence or presence of certain morphological features, such as chondrules, significant cracks, or minor artefacts. The possible presence of these features in a specific shape model has been recorded in the database.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"216 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745496","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 probabilistic model to estimate number densities from column densities in molecular clouds","authors":"Brandt A. L. Gaches, Michael Y. Grudić","doi":"10.1051/0004-6361/202451753","DOIUrl":"https://doi.org/10.1051/0004-6361/202451753","url":null,"abstract":"Constraining the physical and chemical evolution of molecular clouds is essential to our understanding of star formation. These investigations often necessitate knowledge of some local representative number density of the gas along the line of sight. However, constraining the number density is a difficult endeavor. Robust constraints on the number density often require line observations of specific molecules along with radiation transfer modeling, which provides densities traced by that specific molecule. Column density maps of molecular clouds are more readily available, with many high-fidelity maps calculated from dust emission and extinction, in particular from surveys conduction with the Herschel Space Observatory. We introduce a new probabilistic model which is based on the assumption that the total hydrogen nuclei column density along a line of sight can be decomposed into a turbulent component and a gravitationally dominated component. Therefore, for each pixel in a column density map, the line of sight was decomposed into characteristic diffuse (dubbed “turbulent”) and dense (dubbed “gravitational”) gas number densities from column density maps. The method thus exploits a physical model of turbulence to decouple the random turbulent column from gas in dense bound structures empirically using the observed column density maps. We find the model produces reasonable turbulent and gravitational densities in the Taurus L1495/B213 and Polaris Flare clouds. The model can also be used to infer an effective attenuating column density into the cloud, which is useful for astrochemical models of the clouds. We conclude by demonstrating an application of this method by predicting the emission of the [C II] 1900 GHz, [C I] 492 GHz, and CO (J = 1–0) 115 GHz lines across the Taurus L1495/B213 region at the native resolution of the column density map utilizing a grid of photodissociation-region models.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"72 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745693","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":"Kilonova ejecta opacity inferred from new large-scale HFR atomic calculations in all elements between Ca (Z = 20) and Lr (Z = 103)","authors":"J. Deprince, G. Wagle, S. Ben Nasr, H. Carvajal Gallego, M. Godefroid, S. Goriely, O. Just, P. Palmeri, P. Quinet, S. Van Eck","doi":"10.1051/0004-6361/202452967","DOIUrl":"https://doi.org/10.1051/0004-6361/202452967","url":null,"abstract":"<i>Context.<i/> The production of elements heavier than iron in the Universe still remains an unsolved mystery. About half of them are thought to be produced by the astrophysical r-process (rapid neutron-capture process), for which neutron star mergers (NSMs) are among the most promising production sites. In August 2017, gravitational waves generated by a NSM were detected for the first time by the LIGO detectors (event GW170817), and the observation of its electromagnetic counterpart, the kilonova (KN) AT2017gfo, suggested the presence of heavy elements in the KN ejecta. The luminosity and spectra of such KN emission depend significantly on the ejecta opacity. Atomic data and opacities for heavy elements are thus sorely needed to model and interpret KN light curves and spectra.<i>Aims.<i/> The present work focuses on large-scale atomic data and opacity computations for all heavy elements with <i>Z<i/> ≥ 20, with a special effort on lanthanides and actinides, for a grid of typical KN ejecta conditions (temperature, density, and time post-merger) between one day and one week after the merger (corresponding to the local thermodynamical equilibrium photosphere phase of the KN ejecta).<i>Methods.<i/> In order to do so, we used the pseudo-relativistic Hartree–Fock (HFR) method as implemented in Cowan’s codes, in which the choice of the interaction configuration model is of crucial importance.<i>Results.<i/> In this paper, HFR atomic data and opacities for all elements between Ca (<i>Z<i/> = 20) and Lr (<i>Z<i/> = 103) are presented, with a special focus on lanthanides and actinides. In particular, we found increased lanthanide opacities compared to previous works. Besides, we also discuss the contribution of every single element with <i>Z<i/> ≥ 20 to the total KN ejecta opacity for a given NSM model, depending on their Planck mean opacities and elemental abundances. An important result is that lanthanides are found to not be the dominant sources of opacity, at least on average. The impact on KN light curves of considering such atomic-physics-based opacity data instead of typical crude approximation formulae is also evaluated. In addition, the importance of taking the ejecta composition into account directly in the expansion opacity determination (instead of estimating single-element opacities) is highlighted. A database containing all the relevant atomic data and opacity tables has also been created and published online along with this work.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"16 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745495","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":"Solving for the 2D water snowline with hydrodynamic simulations","authors":"Yu Wang, Chris W. Ormel, Shoji Mori, Xue-Ning Bai","doi":"10.1051/0004-6361/202453036","DOIUrl":"https://doi.org/10.1051/0004-6361/202453036","url":null,"abstract":"<i>Context.<i/> In protoplanetary disks, the water snowline marks the location where inwardly drifting, ice-rich pebbles sublimate, releasing silicate grains and water vapor. These processes can trigger pile-ups of solids, making the water snowline a promising site for the formation of planetesimals, for instance, via streaming instabilities. However, previous studies exploring the dust pile-up conditions have typically employed 1D, vertically averaged, and isothermal assumptions.<i>Aims.<i/> In this work, we investigate how the 2D flow pattern and a realistic temperature structure affect the accumulation of pebbles at the snowline. Furthermore, we explore how latent heat imprints snowline observations.<i>Methods.<i/> We performed 2D multifluid hydrodynamic simulations in the disk’s radial-vertical plane with Athena++, tracking chemically heterogeneous pebbles and the released vapor. With a recently-developed phase change module, the mass transfer and latent heat exchange during ice sublimation are calculated self-consistently. The temperature is calculated by a two-stream radiation transfer method with various opacities and stellar luminosity.<i>Results.<i/> We find that vapor injection at the snowline drives a previously unrecognized outflow, leading to a pile-up of ice outside the snowline. Vapor injection also decreases the headwind velocity in the pile-up, promoting planetesimal formation and pebble accretion. In actively heated disks, we are able to identify a water cycle: after ice sublimates in the hotter midplane, vapor recondenses onto pebbles in the upper, cooler layers, which settle back to the midplane. This cycle enhances the trapped ice mass in the pile-up region. Latent heat exchange flattens the temperature gradient across the snowline, broadening the width, while reducing the peak solid-to-gas ratio of pile-ups.<i>Conclusions.<i/> Due to the water cycle, active disks are more conducive to planetesimal formation than passive disks. The significant temperature dip (up to 40 K) caused by latent heat cooling is manifested as an intensity dip in the dust continuum, presenting a new channel for identifying the water snowline in outbursting systems.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"103 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745494","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 CARMENES search for exoplanets around M dwarfs","authors":"S. V. Jeffers, J. R. Barnes, P. Schöfer, S. Reffert, V. J. S. Béjar, A. Quirrenbach, A. Reiners, Y. Shan, M. R. Zapatero Osorio, B. Fuhrmeister, P. J. Amado, J. A. Caballero, I. Ribas, C. Cardona Guillén, F. Del Sordo, M. Fernández, A. García-López, A. Guijarro, A. P. Hatzes, M. Lafarga, N. Lodieu, M. Kürster, K. Molaverdikhani, D. Montes, J. C. Morales","doi":"10.1051/0004-6361/202347510","DOIUrl":"https://doi.org/10.1051/0004-6361/202347510","url":null,"abstract":"<i>Context.<i/> Current exoplanet surveys are focused on detecting small exoplanets orbiting in the liquid-water habitable zones of their host stars. Despite recent significant advancements in instrumentation, the main limitation in detecting these exoplanets is the intrinsic variability of the host star itself.<i>Aims.<i/> Our aim is to investigate the wavelength dependence of high-precision radial velocities (RV), as stellar activity induced RVs should exhibit a wavelength dependence while the RV variation due to an orbiting planet will be wavelength independent.<i>Methods.<i/> We used the chromatic index (CRX) to quantify the slope of the measured RVs as a function of logarithmic wavelength of the full CARMENES guaranteed time observations (GTO) data set spanning more than eight years of observations of over 350 stars. We investigated the dependence of the CRX in the full Carmenes GTO sample on 24 stellar activity indices in the visible and near-infrared channels of the CARMENES spectrograph and each star’s stellar parameters. We also present an updated convective turnover time scaling for the calculation of the stellar Rossby number for M dwarfs.<i>Results.<i/> Our results show that approximately 17% of GTO stars show a strong or a moderate correlation between the CRX and RV. We can improve the measured RVs by a factor of up to nearly 4 in terms of the root mean square (rms) by subtracting the RV predicted by the CRX-RV correlation from the measured RVs. Mid-M dwarfs with moderate rotational velocities and moderate CRX-gradients, with quasi-stable activity features, have the best rms improvement factors.<i>Conclusions.<i/> We conclude that the CRX is a powerful diagnostic in mitigation of stellar activity and the search for low mass rocky planets.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"49 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745689","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 hot corino-like chemistry of four FUor-like protostars","authors":"F. Cruz-Sáenz de Miera, A. Coutens, Á. Kóspál, P. Ábrahám, A. Dutrey, S. Guilloteau","doi":"10.1051/0004-6361/202451487","DOIUrl":"https://doi.org/10.1051/0004-6361/202451487","url":null,"abstract":"<i>Context.<i/> Compared to Class 0 protostars, the higher densities and lower temperatures of the disk midplanes of Class I young stellar objects (YSOs) limit the detectability of complex organic molecules (COMs). The elevated luminosities of eruptive YSOs increase disk temperatures causing frozen molecules to sublimate, thus making them easier to detect.<i>Aims.<i/> Our aim is to investigate the chemical composition of four FUor-like Class I YSOs (L1551 IRS 5, Haro 5a IRS, V346 Nor, and OO Ser) and to compare their abundances of COMs with other YSOs in the literature.<i>Methods.<i/> We searched for COMs line emission in ALMA Band 6 observations. We used the CASSIS software to determine their column densities (<i>N<i/>) and excitation temperatures (<i>T<i/><sub>ex<sub/>) assuming local thermodynamical equilibrium.<i>Results.<i/> We detected 249 transitions from 12 COMs. In L1551 IRS 5 we identified CH3OH, <sup>13<sup/>CH<sub>3<sub/>OH, CH<sub>3<sub/><sup>18<sup/>OH, CH<sub>2<sub/>DOH, CH<sub>3<sub/>CHO, CH<sub>3<sub/>OCH<sub>3<sub/>, CH<sub>3<sub/>OCHO, CH<sub>3<sub/>COCH<sub>3<sub/>, C<sub>2<sub/>H<sub>5<sub/>OH, C<sub>2<sub/>H<sub>5<sub/>CN, <sup>13<sup/>CH<sub>3<sub/>CN, and CH<sub>3<sub/>C<sup>15<sup/>N. Haro 5a IRS and OO Ser have emission from CH<sub>3<sub/>OH, CH<sub>3<sub/>CHO, CH<sub>3<sub/>OCH<sub>3<sub/> , and CH<sub>3<sub/> OCHO. CH<sub>3<sub/>COCH<sub>3<sub/> is also detected in OO Ser. In V346 Nor we found CH<sub>3<sub/>OH, CH<sub>2<sub/>DOH, CH<sub>3<sub/>CHO, CH<sub>3<sub/>OCH<sub>3<sub/> , CH<sub>3<sub/>OCHO, and C<sub>2<sub/>H<sub>5<sub/>CN. The emission of COMs is compact in all targets. The analysis indicates that their temperatures are above 100 K. The abundance ratios of COMs derived for these eruptive YSOs, and for other protostars in the literature, span several orders of magnitude without any clear differentiation between the eruptive and quiescent YSOs. The column density of the main isotopolog of CH<sub>3<sub/> OH should not be used as a reference, as most of the lines are optically thick.<i>Conclusions.<i/> The hot and compact emission of COMs indicates that the four FUor-like targets are hot corino-like. Spectral studies of these objects can be useful for investigating the complex organic chemistry at later evolutionary stages than the usual Class 0 stage.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"25 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745491","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":"Dust shells and dark linear structures on dust tails of historical and recent long-period comets","authors":"Fernando Moreno, Emmanuel Jehin","doi":"10.1051/0004-6361/202553986","DOIUrl":"https://doi.org/10.1051/0004-6361/202553986","url":null,"abstract":"<i>Context.<i/> Dust halos or shells, along with linear dark structures along the axes of dust tails, are commonly observed in many long- period comets near perihelion. Examples range from the recent C/2023 A3 (Tsuchinshan-ATLAS) to historical comets such as the Great Comet of 1874, C/1874 H1 (Coggia).<i>Aims.<i/> While dust halos can readily be modeled as spin-modulated activity originating from the comet nucleus, their possible connection to those dark linear features has, to our knowledge, not been investigated. The aim of this paper is to shed light on the formation of these remarkable structures by modeling a sample of six long-period comets, using similar dust physical properties and ejection parameters, to explore whether they share a common origin.<i>Methods.<i/> To model the dust features, we employed a Monte Carlo procedure to generate synthetic images. The particles ejected from the comet nucleus follow a power-law size distribution and are released into interplanetary space at speeds determined by the ratio of solar radiation pressure to solar gravity, the heliocentric distance, and, as a new feature of the code, the solar zenith angle at the emission point.<i>Results.<i/> We demonstrate that, in all the cases analyzed, the dust shells form as a result of short-term events characterized by cyclically varying ejection of very small particles from large surface areas on the rotating nucleus. These events are triggered as these areas become freshly exposed to solar radiation near perihelion due to the high obliquity of the spin axes of their nuclei. The dark linear stripes along the tail axes may arise from a specific dependence of the ejection speeds on the square root of the cosine of the zenith angle, as is predicted by hydrodynamical modeling, but their presence is also dependent on the extent of the latitude region of emission that defines the velocity vector field.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"28 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745692","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 effects of spatial scales on the in situ photometric analysis of the Chang’e-4 landing region","authors":"Yaya Gu, Jianzhong Liu, Yazhou Yang, Jian Chen, Qinghong Zeng, Zhenxing Zhao, Jingyi Zhang","doi":"10.1051/0004-6361/202453473","DOIUrl":"https://doi.org/10.1051/0004-6361/202453473","url":null,"abstract":"<i>Context.<i/> Visible and near-infrared reflectance spectroscopy is widely used to determine the surface composition and maturity of the Moon, but it may be influenced by the observation geometry. In situ observation is crucial for understanding the angular scattering behaviour of the lunar surface and can help to link laboratory measurements with orbital remote sensing. The Chang’e-4 (CE-4) rover has been exploring on the lunar surface for five years and has collected in situ spectral data covering a wide range of measurement angles.<i>Aims.<i/> Our aim is to investigate the impact of different spatial scales (from several centimetres to tens of centimetres) on the photometric analysis results of the CE-4 landing region and the phase reddening effects.<i>Methods.<i/> We constructed four sets of spectrophotometric data with different spatial scales (~2 cm, ~5.5 cm, ~10.5 cm, and ~15 cm × 21 cm) based on the spectral data acquired by the CE-4 imaging spectrometer and employed the Hapke model for photometric inversion analysis.<i>Results.<i/> For the four different spatial scales, the derived phase function parameters lie outside the ‘hockey stick’ area and the photometric roughness parameter is smaller than 10°. These parameters show clear variation trends as the spatial scale increases. The reflectance phase curves show a distinct bowl-like shape with a turning point near 90° of phase angle. The colour ratios (ratios of reflectance at two different wavelengths) manifest significant phase-angle dependence, which may affect the estimation of surface maturity. The colour ratio phase curves exhibit a distinct arch shape when involving visible bands (<745 nm), whereas it appears as a monotonically increasing pattern when both bands are in the near-infrared wavelength range (R945/R745).<i>Conclusions.<i/> Varied spatial scales have no significant effect on the phase curve shape and phase reddening effects, but do influence the photometric parameters derived using the Hapke model. This study could serve as a reference to link the discrepancies between laboratory and orbital research.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"21 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745493","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":"Projection-angle effects when “observing” a turbulent magnetized collapsing molecular cloud","authors":"A. Tritsis, S. Basu, C. Federrath","doi":"10.1051/0004-6361/202453265","DOIUrl":"https://doi.org/10.1051/0004-6361/202453265","url":null,"abstract":"<i>Context<i/>. Interstellar magnetic fields are thought to play a fundamental role in the evolution of star-forming regions. Polarized thermal dust emission serves as a key probe for understanding the structure of the plane-of-the-sky component of the magnetic field in such regions. However, inclination effects can potentially significantly influence the apparent morphology of the magnetic field and lead to erroneous conclusions regarding its dynamical importance.<i>Aims<i/>. Our aim is to investigate how projection-angle effects impact dust polarization maps and to explore new ways for accessing the inclination angle of the mean component of the magnetic field with respect to the plane of the sky.<i>Methods<i/>. We post-processed a 3D ideal magnetohydrodynamic simulation of a turbulent collapsing molecular cloud at a central density of 10<sup>5<sup/> cm<sup>−3<sup/>, when the cloud has flattened perpendicular to the mean magnetic field. We produced synthetic dust polarization measurements under various projection angles, ranging from “face-on” (i.e., viewed along the mean magnetic field direction) to “edgeon” (perpendicular to the mean magnetic field direction). Additionally, we used synthetic position-position-velocity (PPV) data cubes from the CO (<i>J<i/> = 1 → 0) transition, presented in a companion paper.<i>Results<i/>. The projected magnetic-field morphology is found to be highly affected by the projection angle with the hourglass morphology being clearly visible only for projection angles close to “edge-on”. We find that the direction of the apparent “flow” between successive velocity channels in the simulated PPV data cubes shows an increasing correlation with the synthetic dust polarization observations, as the cloud is observed closer to an “edge-on” orientation. Based on this property, we have developed a new method to probe the inclination angle of the magnetic field relative to the plane of the sky. We validated our approach by generating additional synthetic data (PPV cubes and polarization maps) at an earlier stage of the cloud’s evolution. We demonstrate an excellent quantitative agreement between the derived inclination angle and the true observational angle. We note that our method is relevant only for collapsing clouds.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"58 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143745691","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}