arXiv subjects

P. Caselli

Publications and source records attributed to P. Caselli.

At least 37 records · Page 2Linked to original sources

arXiv2025

First results from ALPPS: a sub-Alfvénic streamer in SVS13A

We present the first results from the ALMA Perseus Polarization Survey (ALPPS), focusing on the magnetic field in the SVS13A circumbinary disk. The dataset includes full-Stokes dust continuum observations at $\sim0\farcs3$ and 870 $μ$m, as well as molecular line emission from C$^{17}$O$(J=3 \rightarrow 2)$ at $\sim0\farcs3$, C$^{18}$O$(J=2 \rightarrow 1)$ at $\sim0\farcs2$, and DCN$(J=3 \rightarrow 2)$ at $\sim0\farcs1$ angular resolution. Our observations resolve both a previously identified dust spiral and an infalling streamer, capturing their spatial and kinematic structures. The streamer is traced from scales $>300$ au down to the circumbinary disk. Using alignment measure (AM) maps and histograms that compare the orientations of the plane-of-sky magnetic field with local intensity and velocity gradients, we find that the AM distribution peaks at a value of 1. This AM peak strongly suggests alignment between the field and the dust total intensity emission, as well as between the field and the gas velocity, which in turn suggests grain alignment by magnetic fields. From our data, we derive a magnetic field strength, B$_{\mathrm{pos}} \sim 1.1 \pm 0.6$\, mG, and a kinetic to magnetic energy ratio of $0.5 \pm 0.4$, suggesting magnetic dominance. We also produced a map of the Alfvénic Mach number, finding $\mathcal{M}_{\rm A} < 1$ along the streamer, consistent with sub-Alfvénic infalling motions. Therefore, the field is likely facilitating the inflow of material from the envelope onto the disk by constraining movement across the field lines. This represents the first detection of a magnetically sub-Alfvénic infalling streamer in a protostellar system.

astro-ph.GA↗

arXiv2025

Constraints on the Orbit of the Young Substellar Companion GQ Lup B from High-Resolution Spectroscopy and VLTI/GRAVITY Astrometry

Understanding the orbits of giant planets is critical for testing planet formation models, particularly at wide separations greater than 10 au where traditional core accretion becomes inefficient. However, constraining orbits at these separations has been challenging because of sparse orbital coverage and degeneracies in the orbital parameters. We use existing high-resolution spectroscopic measurements from CRIRES+ (R ~ 100000), astrometric data from SPHERE, NACO, and ALMA, and new high-precision GRAVITY astrometry to refine the orbit of GQ Lup B, a ~30 M_J companion at ~100 au, in a system that also hosts a circumstellar disk and a wide companion, GQ Lup C. Including radial velocity data significantly improves orbital constraints by breaking the degeneracy between inclination and eccentricity that affects astrometry-only fits for long-period companions. This work is among the first to combine high-precision astrometry with the companion's relative radial velocity to achieve improved orbital constraints. The eccentricity is refined from e = 0.47 (+0.14, -0.16) with GRAVITY alone to e = 0.35 (+0.10, -0.09) when RVs and GRAVITY data are combined. The orbit is misaligned by 63 (+6, -14) deg relative to the circumstellar disk and 52 (+19, -24) deg relative to the host star spin axis, and is more consistent (34 (+6, -13) deg) with the inclination of the wide tertiary companion GQ Lup C disk. These results support a formation scenario for GQ Lup B consistent with cloud fragmentation and highlight the power of combining companion RV constraints with interferometric astrometry to probe the dynamics and formation of wide-orbit substellar companions.

astro-ph.EP↗

arXiv2025

CO Depletion in Infrared Dark Clouds

Infrared Dark Clouds (IRDCs) are cold, dense structures representative of the initial conditions of star formation. Many studies of IRDCs employ CO to investigate cloud dynamics. However, CO can be highly depleted from the gas phase in IRDCs, impacting its fidelity as tracer. CO depletion is also of great interest in astrochemistry, since CO ice in dust grain mantles provides the raw material for forming complex organic molecules. We study CO depletion toward four IRDCs to investigate how it correlates with volume density and dust temperature, calculated from Herschel images. We use 13CO(1-0) and (2-1) maps to measure CO depletion factor, $f_D$, across IRDCs G23.46-00.53, G24.49-00.70, G24.94-00.15, and G25.16-00.28. We also consider a normalized CO depletion factor, f_D', which takes a value of unity, i.e., no depletion, in the outer, lower density, warmer regions. We then investigate the dependence of f_D and f_D' on gas density, $n_H$ and dust temperature, $T_{dust}$. We find CO depletion rises as density increases, reaching maximum values of f_D'$\sim$10 in regions with $n_H>3\times10^5\:{cm}^{-3}$, although with significant scatter at a given density. We find a tighter, less scattered relation of f_D' with temperature, rising rapidly for temperatures <18 K. We propose a functional form $f_D^\prime = \:{exp}(T_0/[T_{dust}-T_1])$ with $T_0\simeq4\:$K and $T_1\simeq12\:$K to reproduce this behaviour. We conclude that CO is heavily depleted from the gas phase in cold, dense regions of IRDCs. Thus CO depletion can lead to underestimation of total cloud masses based on CO line fluxes by factors up to 5. These results indicate a dominant role for thermal desorption in setting near equilibrium abundances of gas phase CO in IRDCs, providing important constraints for both astrochemical models and the chemodynamical history of gas during the early stages of star formation.

astro-ph.GA↗

arXiv2025

Hunting pre-stellar cores with APEX: overview

[Abridged] $Context.$ Pre-stellar cores are centrally concentrated starless cores on the verge of star formation and they represent the initial conditions for star and planet formation. Pre-stellar cores host an active organic chemistry and isotopic fractionation, kept stored into thick icy mantles, which can be inherited by the future protoplanetary disks and planetesimals. So far, only a few have been studied in detail, with special attention being paid to L1544 in the Taurus Molecular Cloud. $Aims.$ The aim is to identify nearby ($<$200 pc) pre-stellar cores in an unbiased way, to build a sample that can then be studied in detail. $Methods.$ We first used the Herschel Gould Belt Survey archival data, selecting all those starless cores with central H$_2$ number densities higher than or equal to 3$\times$10$^5$ cm$^{-3}$, the density of L1544 within the Herschel beam. The selected 40 (out of 1746) cores have then been observed in N$_2$H$^+$(3-2) and N$_2$D$^+$(4-3) using the APEX antenna. $Results.$ A total of 17 bona-fide (i.e., with a deuterium fraction larger than 10%) pre-stellar cores have been identified. Other 16 objects can also be considered pre-stellar, as they are dynamically evolved starless cores, but their deuterium fraction is relatively low ($<$10%). The remaining 7 objects have been found associated with very young stellar objects. $Conclusions.$ Dust continuum emission, together with spectroscopic observations of N$_2$H$^+$(3-2) and N$_2$D$^+$(4-3), is a powerful tool to identify pre-stellar cores in molecular clouds. Detailed modeling of the physical structure of the objects is now required for reconstructing the chemical composition as a function of radius. This work has provided a statistically significant sample of 33 pre-stellar cores, a crucial step in the understanding of the process of star and planet formation.

astro-ph.GA↗

arXiv2025

High sensitivity molecular line observations towards the L1544 pre-stellar core challenge current models

The increased sensitivity and spectral resolution of observed spectra towards the pre-stellar core L1544 are challenging the current physical and chemical models. With the aim of further constraining the structure of L1544 as well as assessing the completeness of chemical networks, we turn to radiative transfer modelling of observed molecular lines towards this source. We obtained high-sensitivity and high-spectral resolution observations of HCO+ (J = 1 - 0), CS (J = 2 - 1), C34S (J = 2 - 1), H2CO (J ,Ka,Kc = 2,1,2 - 1,1,1), c-C3H2 (J,Ka,Kc = 2,1,2 - 1,0,1), SO (N,J = 2,3 - 1,2) and 34SO (N,J = 2,3 - 1,2) with the IRAM 30m telescope towards the dust peak of L1544. A non-Local Thermodynamic Equilibrium radiative transfer code is coupled to the Markov Chain Monte Carlo method to model the observations. We find that with just one transition for each isotope, the modelling cannot find a global minimum that fits the observations. The derived fractional abundance profiles are compared to those computed with chemical models. The observed transitions trace gas components with distinct dynamics at different distances along the radius of the core. Moreover, the results evidence a poor reproduction of sulphur chemistry by chemical modelling and stresses the need to include a more consistent S-depletion process to accurately reproduce the S-chemistry towards dense cores.

astro-ph.GA↗

arXiv2025

Broadband spectroscopy of astrophysical ice analogues: III. Scattering properties and porosity of CO and CO$_2$ ices

$Context.$ The quantification of the terahertz (THz) and IR optical properties of astrophysical ice analogs, which have different molecular compositions, phases, and structural properties, is required to model both the continuum emission by the dust grains covered with thick icy mantles and the radiative transfer in the dense cold regions of the interstellar medium. $Aims.$ We developed a model to define a relationship between the THz$-$IR response and the ice porosity. It includes the reduced effective optical properties of porous ices and the additional wave extinction due to scattering on pores. The model is applied to analyze the measured THz$-$IR response of CO and CO$_2$ laboratory ices and to estimate their scattering properties and porosity. $Methods.$ Our model combines the Bruggeman effective medium theory, the Lorentz-Mie and Rayleigh scattering theories, and the radiative transfer theory to analyze the measured THz$-$IR optical properties of laboratory ices. $Results.$ We apply this model to show that the electromagnetic-wave scattering in studied laboratory ices occurs mainly in the Rayleigh regime at frequencies below 32 THz. We conclude that pores of different shapes and dimensions can be approximated by spheres of effective radius. By comparing the measured broadband response of our laboratory ices with those of reportedly compact ices from earlier studies, we quantify the scattering properties of our CO and CO$_2$ ice samples. Their porosity is shown to be as high as 15% and 22%, respectively. Underestimating the ice porosity in the data analysis leads to a proportional relative underestimate of the THz$-$IR optical constants. $Conclusions.$ The scattering properties and porosity of ices have to be quantified along with their THz$-$IR response in order to adequately interpret astrophysical observations.

astro-ph.IM↗

arXiv2025

Cosmic-ray ionisation rate in low-mass cores: the role of the environment

Context: Cosmic rays drive several key processes for the chemistry and dynamical evolution of star-forming regions. Their effect is quantified mainly by means of the cosmic-ray ionisation rate $ζ_2$. Aims: We aim to obtain a sample of $ζ_2$ measurements in 20 low-mass starless cores embedded in different parental clouds, to assess the average level of ionisation in this kind of sources and to investigate the role of the environment in this context. The warmest clouds in our sample are Ophiuchus and Corona Australis, where star formation activity is higher than in the Taurus cloud and the other isolated cores we targeted. Methods: We compute $ζ_2$ using an analytical method based on the {column density} of ortho-$\rm H_2D^+$, the CO abundance, and the deuteration level of HCO$^+$. To estimate these quantities, we analysed new, high-sensitivity molecular line observations obtained with the Atacama Pathfinder EXperiment (APEX) single-dish telescope and archival continuum data from Herschel. Results: We report $ζ_2$ estimates in 17 cores in our sample and provide upper limits on the three remaining sources. The values span almost two orders of magnitude, from $1.3 \times 10^{-18}\, \rm s^{-1}$ to $8.5 \times 10^{-17}\, \rm s^{-1}$. Conclusions: We find no significant correlation between $ζ_2$ and the core's column densities $N\rm (H_2)$. On the contrary, we find a positive correlation between $ζ_2$ and the cores' temperature, estimated via Herschel data: cores embedded in warmer environments present higher ionisation levels. The warmest clouds in our sample are Ophiuchus and Corona Australis, where star formation activity is higher than in the other clouds we targeted. The higher ionisation rates in these regions support the scenario that low-mass protostars in the vicinity of our targeted cores contribute to the re-acceleration of local cosmic rays.

astro-ph.GA↗

arXiv2025

Low-velocity large-scale shocks in the infrared dark cloud G035.39-00.33: bubble-driven cloud-cloud collisions

Low-velocity large-scale shocks impacting on the ISM may efficiently shape molecular clouds and trigger star formation within them. These shocks, both driven by galactic bubbles and/or cloud-cloud collisions, leave specific signatures in the gas morphology and kinematics. Observational studies of such signatures are crucial to investigate if and how shocks affect the clouds formation process and trigger their future star formation. We have analysed the shocked and dense gas tracers SiO(2-1) and H13CO+(1-0) emission toward the IRDC G035.39-00.33, using new, larger-scale maps obtained with the 30m telescope at the Instituto de Radioastronomìa Millimétrica. We find that the dense gas is organised into a northern and a southern filament having different velocities and tilted orientation with respect to each other. The two filaments are spatially separated yet connected by a faint bridge feature also seen in a position-velocity diagram extracted across the cloud. This bridge-feature, typical of cloud-cloud collisions, also coincides with a very spectrally narrow SiO-traced emission. The northern filament is suggested to be interacting with the nearby supernova remnant G035.6-0.4. Toward the southern filament, we also report the presence of a parsec-scale, spectrally narrow SiO emission likely driven by the interaction between this filament and a nearby expanding shell. The shell is visible in the 1.3 GHz and 610 MHz continuum images and our preliminary analysis suggests it may be the relic of a supernova remnant. We conclude that the two filaments represent the densest part of two colliding clouds, pushed toward each other by nearby Supernova Remnants. We speculate that this cloud-cloud collision driven by stellar feedback may have assembled the infrared dark cloud. We also evaluate the possibility that star formation may have been triggered within G035.39-00.33 by the collision.

astro-ph.GA↗

arXiv2025

Chemical segregation analysed with unsupervised clustering

Molecular emission is a powerful tool for studying the physical and chemical structures of dense cores. The distribution and abundance of different molecules provide information on the chemical composition and physical properties in these cores. We study the chemical segregation of three molecules (c-C$_3$H$_2$, CH$_3$OH, CH$_3$CCH) in the starless cores B68 and L1521E, and the prestellar core L1544. We applied the density-based clustering algorithms DBSCAN and HDBSCAN to identify chemical and physical structures within these cores. To enable cross-core comparisons, the input samples were characterised based on their physical environment, discarding the 2D spatial information. The clustering analysis showed significant chemical differentiation across the cores, successfully reproducing the known molecular segregation of c-C$_3$H$_2$ and CH$_3$OH in all three cores. Furthermore, it identifies a segregation between c-C$_3$H$_2$ and CH$_3$CCH, which is not apparent from the emission maps. Key features driving the clustering are integrated intensity, velocity offset, H$_2$ column density, and H$_2$ column density gradient. Different environmental conditions are reflected in the variations in the feature relevance across the cores. This study shows that density-based clustering provides valuable insights into chemical and physical structures of starless cores. It demonstrates that already small datasets of two or three molecules can yield meaningful results. This new approach revealed similarities in the clustering patterns of CH$_3$OH and CH$_3$CCH relative to c-C$_3$H$_2$, suggesting that c-C$_3$H$_2$ traces regions of lower density than to the other two molecules. This allowed for insight into the CH$_3$CCH peak in L1544, which appears to trace a landing point of chemically fresh gas that is accreted to the core, highlighting the impact of accretion processes on molecular distributions.

astro-ph.GA↗

arXiv2025

Fine-tuning the complex organic molecule formation: sulfur and CO ice as regulators of surface chemistry

Grain-surface chemistry plays a crucial role in the formation of molecules of astrobiological interest, including H$_{2}$S and complex organic molecules (COMs). They are commonly observed in the gas phase toward star-forming regions, but their detection in ices remains limited. Combining gas-phase observations with chemical modeling is therefore essential for advancing our understanding of their chemistry. In this paper we investigate the factors that promote or hinder molecular complexity combining gas-phase observations of CH$_{3}$OH, H$_{2}$S, OCS, N$_{2}$H$^{+}$, and C$^{18}$O with chemical modeling in two dense cores: Barnard-1b and IC348. We observed millimeter emission lines of CH$_{3}$OH, H$_{2}$S, OCS, N$_{2}$H$^{+}$, and C$^{18}$O along strips using the IRAM 30m and Yebes 40m telescopes. We used the gas-grain chemical model \texttt{Nautilus} to reproduce the observed abundance profiles adjusting parameters such as initial sulfur abundances and binding energies. H$_{2}$S, N$_{2}$H$^{+}$ and C$^{18}$O gas-phase abundances vary up to one order of magnitude towards the extinction peak. CH$_{3}$OH abundance remains quite uniform. These abundances can only be reproduced assuming a decreasing sulfur budget, which lowers H$_{2}$S and enhances CH$_{3}$OH abundances. Decreasing binding energies, which are expected in CO-rich apolar ices, are also required. The sulfur depletion required by H$_2$S is generally higher than that required by CH$_3$OH, suggesting unknown sulfur sinks. These findings highlight the intricate relationship between sulfur chemistry and COM formation, driven by the competition between sulfur and CO for hydrogen atoms. Our study emphasizes that the growth of CO ice and the progressive sequestration of hydrogen atoms by sulfur are critical in determining whether chemical complexity can develop, providing key insights into the early stages of star and planet formation.

astro-ph.GA↗

arXiv2025

ANTIHEROES-PRODIGE: Quantifying the connection from envelope to disk with the IRAM 30m telescope and NOEMA I. Attack of the streamers: L1448N's fight for order in the chaos

Star formation is a hierarchical process ranging from molecular clouds down to individual protostars. In particular how infalling asymmetric structures, called streamers, delivering new material onto protostellar systems, are connected to the surrounding envelope is not understood. We investigate the connection between the cloud material at 10000 au scales down to 300 au scales towards L1448N in the Perseus star-forming region hosting three young Class 0/I protostellar systems. Sensitive molecular line observations taken with the IRAM 30m telescope and NOEMA at 1.4 mm are used to study the kinematic properties in the region traced by the molecular lines. Several infalling streamers are associated with the protostellar systems, some of them traced by C18O and DCN, while one of them is bright in SO and SO2. The kinematic properties of the former streamers are consistent with the velocities observed at large envelope scales of 10000 au, while the latter case show different kinematics. The masses and infall rates of the streamers are 0.01 Msun and 0.01-0.1 Msun and 10^-6 Msun/yr and 5-18x10^-6 Msun/yr for IRS3A and IRS3C, respectively. The envelope mass in the L1448N region is ~16Msun, thus the mass of a single streamer is low compared to the envelope mass (<1%). However, compared to the estimated mass of the protostellar systems a single streamer could deliver up to 1% and 8-17% of mass towards IRS3A (M*~1.2 Msun) and IRS3C (M*~1 Msun), respectively. The rotational signatures of structures in L1448N are all connected - from the large-scale envelope, infalling streamers, down to the rotation of all three disks. Two of the three Class 0/I protostellar systems are still fed by this surrounding material, which can be associated to the remnant envelope. However, we also find a streamer that is bright in SO and SO2 towards IRS3C that could be connected to a nearby sulfur reservoir.

astro-ph.SR↗

arXiv2025

Direct imaging discovery of a young giant planet orbiting on Solar System scales

HD 135344 AB is a young visual binary system that is best known for the protoplanetary disk around the secondary star. The circumstellar environment of the A0-type primary star, on the other hand, is already depleted. HD 135344 A is therefore an ideal target for the exploration of recently formed giant planets because it is not obscured by dust. We searched for and characterized substellar companions to HD 135344 A down to separations of about 10 au. We observed HD 135344 A with VLT/SPHERE in the $H23$ and $K12$ bands and obtained $YJ$ and $YJH$ spectroscopy. In addition, we carried out VLTI/GRAVITY observations for the further astrometric and spectroscopic confirmation of a detected companion. We discovered a close-in young giant planet, HD 135344 Ab, with a mass of about 10 $M_\mathrm{J}$. The multi-epoch astrometry confirms the bound nature based on common parallax and common proper motion. This firmly rules out the scenario of a non-stationary background star. The semi-major axis of the planetary orbit is approximately 15-20 au, and the photometry is consistent with that of a mid L-type object. The inferred atmospheric and bulk parameters further confirm the young and planetary nature of the companion. HD 135344 Ab is one of the youngest directly imaged planets that has fully formed and orbits on Solar System scales. It is a valuable target for studying the early evolution and atmosphere of a giant planet that could have formed in the vicinity of the snowline.

astro-ph.EP↗

arXiv2025

PRODIGE VI -- Envelope to Disk with NOEMA: VI. The Missing Sulfur Problem

Determining the amount of sulfur in volatiles and refractories in the ISM remains one of the main problems in astrochemistry. The detection of H$_2$S ices, which are thought to be one of the main sulfur reservoirs, has not been achieved yet, and the only S-bearing species detected in the ices to date is OCS. PRODIGE large survey observations with NOEMA of several Class 0/I protostars in the Perseus Molecular Cloud provide a perfect opportunity to study the H$_2$S and OCS composition of the ices through the volatiles sublimated in the warm inner core (T$>$100K, n $\sim10^6$cm$^{-3}$) of these protostars. Our aim is to determine the H$_2$S/OCS ratio in the warm inner core of 24 protostars in order to study how it is affected by different factors during its evolution. We used the NOEMA millimeter observations from the PRODIGE program of H$_2$S, H$_2^{33}$S, OCS, OC$^{33}$S and OC$^{34}$S to estimate the H$_2$S and OCS column densities in the warm inner cores. We used SO and SO$_2$ data from the ALMA archive to give a rough estimate of the total sulfur abundance. We explore the chemistry of H$_2$S and OCS in the warm cores using chemical and dynamical simulations of the collapse of a dense core to form a protostar. The estimated H$_2$S/OCS ratio reveals a segregation of the sources into ``OCS-poor'' and ``OCS-rich'' protostars, where the OCS-poor protostars present higher H$_2$S/OCS ratios than the OCS-rich ones. Total sulfur abundance is always dominated by either H$_2$S or OCS, grows with evolution during the Class 0 phase up to $D_S<8$, and decreases again in the Class I. Simulations show that temperature changes in the pre-stellar phase and during the collapse can produce substantial differences in the H$_2$S and OCS abundances and in the H$_2$S/OCS ratio. Our analysis shows that the H$_2$S/OCS ratio is strongly influenced by the environment and the initial conditions of the cloud.

astro-ph.GA↗

arXiv2025

The Effect of Weak Cosmic Ray Heating Events on the Desorption of $\rm H_2$

The typical amount of molecular hydrogen (${\rm H_2}$) in interstellar ices is not known, but significant freeze-out of ${\rm H_2}$ on dust grains is not expected. However, chemical models ubiquitously predict large amounts of $\rm H_2$ freeze-out in dense cloud conditions, and specialized treatments are needed to control the $\rm H_2$ population on grains. Here we present a numerical desorption model where the effect of weak heating events induced by cosmic rays (CRs) that heat grains to temperatures of a few tens of Kelvin at high frequencies is included, improving upon earlier desorption models that only consider strong heating events (maximum grain temperature close to 100 K) that occur at a low frequency. A temperature of a few tens of Kelvin is high enough to induce efficient desorption of $\rm H_2$, but we find that even the weak heating events do not occur often enough to lead to significant $\rm H_2$ desorption. Taking the weak heating events into account does affect the predicted abundances of other lightly-bound species, but the effect is restricted to low column densities. We make here the canonical assumption that the grains are spherical with a radius of 0.1 $μ$m. It is conceivable that in the case of a grain size distribution, weak heating events could provide a boost to $\rm H_2$ desorption coming off small grains, which are the most numerous. Further studies are still required to better quantify the role of CRs in the desorption of $\rm H_2$ and other weakly bound species.

astro-ph.GA↗

arXiv2025

CHemical Evolution in MassIve star-forming COres (CHEMICO). I. Evolution of the temperature structure

Increasing evidence shows that most stars in the Milky Way, including the Sun, are born in star-forming regions containing also high-mass stars, but due to both observational and theoretical challenges, our comprehension of their chemical evolution is far less clear than that of their low-mass counterparts. We present the project "CHemical Evolution of MassIve star-froming COres" (CHEMICO). The project aims at investigating any aspect of the chemical evolution of high-mass star-forming cores by observing representatives of the three main evolutionary categories: high-mass starless cores, high-mass protostellar objects, and ultra-compact HII regions. We carried out an unbiased spectral line survey of the entire bandwidth at 3, 2, and 1.2 mm with the 30m telescope of the Insitut de Radioastronomie millimetrique towards three targets that represent the three evolutionary stages. The number of lines and species detected increases with evolution. In this first work, we derive the temperature structure of the targets through the analysis of the carbon-bearing species C2H, c-C3H, c-C3H2, C4H, CH3CCH, HC3N, CH3CN, and HC5N. The excitation temperature, Tex, increases with evolution in each species, although not in the same way. Hydrocarbons tend to be associated with the smallest Tex values and enhancements with evolution, while cyanides are associated with the highest Tex values and enhancements. In each target, the higher the number of atoms in the molecule, the higher Tex tends to be. The temperature structure evolves from a cold, uniform envelope traced by simple hydrocarbons in the high-mass starless core stage, to a more stratified envelope in the protostellar stage (made by a hot core, a shell with intermediate Tex, and a larger cold envelope), to finally a hot core surrounded only by a cold envelope in the Ultracompact HII stage.

astro-ph.GA↗

arXiv2025

Orbit and atmosphere of HIP 99770 b through the eyes of VLTI/GRAVITY

Context: Inferring the likely formation channel of giant exoplanets and brown dwarf companions from orbital and atmospheric observables remains a formidable challenge. Further and more precise directly measured dynamical masses of these companions are required to inform and gauge formation, evolutionary, and atmospheric models. We present an updated study of HIP 99770 b based on observations conducted with VLTI/GRAVITY. Aims: Combining the new data with previous observations from the literature, we characterise HIP 99770 b to better constrain its orbit, dynamical mass, and atmospheric properties, as well as to shed light on its likely formation channel. Methods: We ran a renewed orbit fit to further constrain the dynamical mass of the companion and the orbit solution. We also analysed the GRAVITY K-band spectrum, placing it into context with literature data, and extracting magnitude, age, spectral type, bulk properties and atmospheric characteristics of HIP 99770 b. Results: We detected the companion at a radial separation of $417\,\mathrm{mas}$ from its host. The new orbit fit yields a dynamical mass of $17_{-5}^{+6}\,\mathrm{M}_\mathrm{Jup}$ and an eccentricity of $0.31_{-0.12}^{+0.06}$. We also find that additional relative astrometry epochs in the future will not enable further constraints on the dynamical mass due to the dominating relative uncertainty on the Hipparcos-Gaia proper motion anomaly. The publication of Gaia DR4 will likely ease this predicament. We find that the companion is consistent with spectral type L8 and exhibits a potential metal enrichment in its atmosphere. Conclusions: These results do not yet allow for a definite inference of the companion's formation channel. Nevertheless, the new constraints on its bulk properties and the additional GRAVITY spectrum presented here will aid future efforts to determine the formation history of HIP 99770 b.

astro-ph.EP↗

arXiv2025

PRODIGE - envelope to disk with NOEMA: V. Low 12C/13C ratios for CH3OH and CH3CN in hot corinos

The 12C/13C isotope ratio has been derived towards numerous cold clouds (20-50 K) and a couple protoplanetary disks and exoplanet atmospheres. However, direct measurements of this ratio in the warm gas (>100 K) around young low-mass protostars remain scarce, but are required to study its evolution during star and planet formation. We derived 12C/13C ratios from the isotopologues of the complex organic molecules (COMs) CH3OH and CH3CN in the warm gas towards seven Class 0/I protostellar systems to improve our understanding of the evolution of the 12C/13C ratios during star and planet formation. We used the data that were taken as part of the PRODIGE large program with the NOEMA at 1mm. The emission of CH3OH and CH3CN is spatially unresolved in the PRODIGE data (300au scale). Derived rotational temperatures exceed 100K, telling us that they trace the gas of the hot corino, where CH3CN probes hotter regions than CH3OH on average (290 K versus 180 K). The column density ratios between the 12C and 13C isotopologues, derived from LTE analysis, range from 4 to 30, thus, are significantly lower than the expected local ISM isotope ratio of about 68. Assuming that CH3CN and CH3OH may inherit the 12C/13C ratio from their precursor species, astrochemical models were conducted for the latter and compared with our observational results. We conclude that an enrichment in 13C in COMs at the earliest protostellar stages is likely inherited from the COMs' precursor species, whose 12C/13C ratios are set during the prestellar stage via isotopic exchange reactions. This also implies that low 12C/13C ratios observed at later evolutionary stages could at least partially be inherited. A final conclusion on 12C/13C ratios in protostellar environments requires improved observations to tackle current observational limitations and additional modelling efforts.

astro-ph.GA↗

arXiv2025

FAUST XXIV. Large dust grains in the protostellar outflow cavity walls of the Class I binary L1551 IRS5

Planet formation around young stars requires the growth of interstellar dust grains from mm-sized particles to km-sized planetesimals. Numerical simulations have shown that large ($\sim$mm-sized) grains found in the inner envelope of young protostars could be lifted from the disc via winds. However we are still lacking unambiguous evidence for large grains in protostellar winds/outflows. We investigate dust continuum emission in the envelope of the Class I binary L1551 IRS5 in the Taurus molecular cloud, aiming to identify observational signatures of grain growth, such as variations in the dust emissivity index ($β_{\rm mm}$). In this context, we present new, high-angular resolution (50 au), observations of thermal dust continuum emission at 1.3 mm and 3 mm in the envelope ($\sim$3000 au) of L1551 IRS5 , obtained as part of the ALMA-FAUST Large Program. We analyse dust emission along the cavity walls of the CO outflow, extended up to $\sim$1800 au. We find an H$_2$ volume density $>2\times10^5$ cm$^{-3}$, a dust mass of $\sim$58 M$_\oplus$, and $β_{\rm mm}$<1, implying the presence of grains $\sim$10$^3$ times larger than the typical ISM sizes. We provide the first spatially resolved observational evidence of large grains within an outflow cavity wall. Our results suggest that these grains have been transported from the inner disc to the envelope by protostellar winds and may subsequently fall back into the outer disc by gravity and/or via accretion streamers. This cycle provides longer time for grains to grow, playing a crucial role in the formation of planetesimals.

astro-ph.GA↗