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A. Caratti o Garatti

Publications and source records attributed to A. Caratti o Garatti.

At least 19 recordsLinked to original sources
arXiv2026

Mapping of interstellar ices with JWST in protostellar envelopes: Spatial variations of $^{13}$CO$_2$, $^{12}$CO$_2$, CO, OCN$^-$ and H$_2$O ice

The composition of planets and their atmospheres is largely determined by the formation environment of the planet. This environment is pre-determined during early stages when the protostar is still forming. Charting the structure of protostellar envelopes is therefore crucial for understanding how the chemistry is linked to the physical processes occurring in stellar nurseries. We use JWST NIRSpec IFU observations to extract spectra at every pixel in the IFU and map the distribution of $^{13}$CO$_2$,$^{12}$CO$_2$, CO, OCN$^-$ and H$_2$O ice. The 13CO2 ice feature, a known thermal tracer, is also used to identify high-temperature regions where the ices are thermally processed. The findings show that the distribution of ices in both L1527 and IRAS 20126+4104 is not uniform, with both envelopes showing localized temperature zones and substructures. In L1527, CO$_2$ ice segregation and OCN$^-$ enhancement with respect to CO$_2$ are observed in the warm central disk region close to the protostar. In IRAS 20126+4104, the warm temperature zones are observed mostly towards the shocked region in the NW outflow where dense material is interacting with the precessing jet as well as close to the central source. The CO$_2$ ice is segregated at these locations and we observe sublimation of CO ice. In addition, crystalline H$_2$O ice is detected at a few locations in the envelope. In both low mass and high mass protostar the findings indicate that the distribution of ices and their structure are linked to the temperature structure of the envelopes. The envelope of IRAS 20126 shows a more complex structure, where interacting material results in localized regions of high temperatures and denser regions that harbor cooler ices. L1527 in contrast appears to be a more structured system with heated warm ices observed mostly towards the central disk regions.

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arXiv2026

Impact of accretion variability on the CO emission of a disk around a very-low-mass star with JWST

Studying the structure of very-low-mass stars ($M_\star<0.2M_\odot$) protoplanetary disk is crucial to understand the formation of Earth-like planets. In this paper, we characterize the innermost regions of the disk around a known very-low-mass star, 2MASS J16053215-1933159 (J1605 hereafter), by analyzing new JWST/NIRSpec observations taken in 2024, 2 years after a first observation with JWST/MIRI. We find that between the two epochs (2022 \& 2024), the CO flux is reduced by a factor $\sim 3$, the flux of the HI 10-6 line seen by both NIRSpec and MIRI is reduced by a factor $\sim13$, and the total continuum density flux is reduced by $\sim 15 \%$. The accretion rate derived from individual HI lines is consistent with a decrease of a factor $\sim13$ in 2 years. After correcting the spectrum from the CO absorption present in J1605 stellar photosphere, we find that the decrease of the disk's CO emission is consistent with a CO gas of same column density and temperature at each epoch, but originating from a smaller emitting area when the accretion rate is low. While warm hydrocarbons ($\simeq 500~$K) are detected with MIRI-MRS with extremely high column densities of $\rm C_2H_2$, no hydrocarbons features are seen with NIRSpec. We propose that non-LTE effects quench the near-IR emission of hydrocarbons in the warm reservoir. The variation of the accretion luminosity of J1605 correlates with the variation of its fundamental CO luminosity in a similar way as in T-Tauri stars, supporting the idea that very-low-mass stars could be seen as scaled-down versions of T-Tauri stars. The detection of the emission of the fundamental band of CO in disks around cold objects is challenging because of the presence of CO absorption in their photosphere. Future observations (e.g., with ELT/METIS) looking for such emission will require robust ways to constrain the photosphere emission.

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arXiv2026

Ten years since the NGC 6334I-MM1 accretion outburst: the impact on its environment

Ten years on, flaring continues in masers associated with NGC 6334I-MM1. Methanol and hydroxyl masers are nearing quiescent values, but water features remain elevated. Several more 1.665 GHz hydroxyl masers, notably, that flared during the accretion event in NGC 6334I-MM1, are identified and presented. Some hydroxyl masers appear to have been active prior to the 2015 event. Possible explanations are discussed. The radial infrared expansion speed during the accretion event is estimated to be ~1.8 AU/d. However, the expansion speed along the North-South outflow is about ten times faster (~18 AU/d). The maser flaring activity illuminated clumpy structure in NGC 6334I-MM1. Quasi-periodicity is reported after the 2015 accretion event in the total integrated 12.2 GHz methanol emission, predominantly in $v_{12.2}=[-12.0,-9.9]$ \kms, after the accretion event in NGC 6334I-MM1. It is not certain if the periodic masers are located in NGC 6334I-MM1, -MM2, or -MM3. The magnetic field, measured from the Zeeman splitting of two ground state hydroxyl lines, undergoes changes before and after the flare.

astro-ph.GA↗
arXiv2026

JWST/MIRI Detection of Molecular H$_2$ Winds from an Edge-on Class II Source HV Tau C

The evolution of protoplanetary disks is regulated by accretion onto the central star and mass loss through jets and winds. While atomic and ionized outflows are commonly observed, molecular winds in evolved Class II disks remain rarely detected. We characterize the spatial, thermal, kinematic, and dynamical properties of molecular hydrogen (H$_2$) emission from the nearly edge-on Class II disk HV Tau C and assess the impact of its molecular wind. We also constrain accretion using H I recombination lines detected in the same mid-infrared spectrum. Using JWST/MIRI-MRS data from the MINDS Cycle 1 GTO program, we analyze spatially resolved pure-rotational H$_2$ emission. Rotational and position-velocity diagrams constrain excitation and kinematics, from which we estimate wind properties. We detect extended H$_2$ emission tracing a wide-angled, biconical molecular wind extending beyond the near-infrared scattered-light disk, ALMA 887 $μ$m dust continuum, and compact $^{12}$CO ($J=3$-$2$) gas disk. The H$_2$ rotational diagram requires warm ($\sim$600K) and hot ($\sim$2000K) components, similar to those in younger protostars. The gas shows outward motions of a few tens of km s$^{-1}$ and dynamical timescales of tens to hundreds of years. The inferred mass-loss rate is $\sim10^{-8}$ M$_\odot$ yr$^{-1}$, while accretion rates derived from H I lines are $10^{-10}$-$10^{-8}$ M$_\odot$ yr$^{-1}$. The accretion rate may be underestimated because of the edge-on geometry. Our results show that wide-angled molecular H$_2$ winds can persist into the Class II phase, with outflow rates comparable to some protostellar systems, suggesting that such winds may remain important for angular momentum removal, disk evolution, and dispersal. (Abstract modified; see the paper for the full version.)

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arXiv2026

SHARP -- A spectrograph proposal to fully exploit ELT capabilities and look beyond JWST

The Extremely Large Telescopes (ELTs), with their large apertures and cutting-edge Multi-Conjugate Adaptive Optics (MCAO) systems, promise to deliver data that is both sharper and deeper than even the James Webb Space Telescope (JWST) across large fields. SHARP is a concept study for a near-IR (0.95-2.45 $μ$m) spectrograph specifically designed to fully exploit the collecting area and angular resolution capabilities of the upcoming ESO's ELT. The instrument concept is driven by the goal of tackling the most important questions in astrophysics and cosmology, from exploring primordial galaxies to studying the formation of young stellar object and planetary systems in the nearby dust-enshrouded regions, bridging the gap between the local and the distant Universe. This requires versatility to accommodate diverse observational needs. SHARP is composed of two main units: NEXUS, a Multi-Object Spectrograph (MOS) optimized for detecting the faintest sources, and VESPER, a multi-object Integral Field Unit (multi-IFU) designed for brighter ones. This article provides an overview of the scientific design drivers, the solutions developed to meet them, and the resulting optical design that achieves the required performance.

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arXiv2026

JOYS+ analyses of OCN$^-$, N$_2$O, NO, and complex cyanides in ices -- Thermal processing results in modest enhancement of OCN$^-$ ice

Nitrogen-bearing molecules are more difficult to observe than oxygen-bearing ones, mainly due to the lower abundance of nitrogen in the interstellar medium. Therefore, the formation pathways of many of these species is still under debate. Studies prior to the launch of the JWST did not have the sensitivity to observe ices toward the youngest and most deeply embedded Class 0 objects. Here we will focus on OCN$^-$, CH$_3$CN, C$_2$H$_5$CN, NO, and N$_2$O in ices to better understand their formation. We use the data from the JOYS+ program to study 8 Class 0 and 11 Class I objects with JWST. We firmly detect OCN$^-$ in ices for all these objects, tentatively detect CH$_3$CN, C$_2$H$_5$CN, and N$_2$O toward three sources, and find upper limits on the NO abundance in ices. The OCN$^-$/CO$_2$ ratios are found to be larger by a factor of ~2-3 for the objects that have a visible CO$_2$ double peak (a sign of ice thermal processing) pointing to the moderate effect of temperature on OCN$^-$ production. Relation of H$_2$O, CO$_2$, and OCN$^-$ with $A_{\rm V}$ indicates that OCN$^-$ may tentatively form at a later stage than H$_2$O and CO$_2$. We find that the ratios of CH$_3$CN, C$_2$H$_5$CN, and N$_2$O with respect to OCN$^-$ are relatively constant within one order of magnitude across our objects, likely suggesting that they have similar ice environments. The upper limit abundances of NO are ~1 order of magnitude lower than what was previously predicted in ices of a mature protoplanetary disk. This indicates that the detected gas-phase NO in that disk may be a product of another molecule (e.g. N$_2$O) in the ices. We conclude that OCN$^-$ can get enhanced at higher temperatures by only a factor of ~2-3 and thus OCN$^-$ detection alone does not imply ice heating. Large-sample studies of OCN$^-$ toward pre-stellar cores will be useful to further confirm the formation timeline of this molecule.

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arXiv2026

JOYS$+$: A JWST/MIRI survey of the evolution of H$_2$ winds and jets from low-mass protostars

Protostellar outflows display wide-angle winds and collimated jets, the magnetocentrifugal launching of which enables accretion onto the protostar. The majority of the outflow mass is likely ejected or entrained molecular H$_2$, which can now be studied in unprecedented detail with JWST. Using JWST MIRI/MRS observations towards 13 single and 20 multiple Class 0 and I protostars, we investigate the nature and evolution of the H$_2$ wind and jet morphology, mass outflow rate, and velocity and temperature structure. We construct line flux and velocity maps of the H$_2$ S(1) and S(7) lines as well as the sub-mm CO traced by ALMA. Low-$J$ ($J\le4$) H$_2$ transitions trace extended wide-angle, low-velocity (0-20 km s$^{-1}$) winds within the contours of the low-velocity ($< 30$ km s$^{-1}$) sub-mm CO emission, while high-$J$ ($J >5$) transitions are associated with shocks and knots. In Class 0 sources with a known high-velocity ($> 30$ km s$^{-1}$) molecular CO or SiO jet, higher H$_2$ velocities are found along the jet axis. The opening angle of the wind traced by the H$_2$ S(1) line broadens from $\sim20^\circ$ to $\sim90^\circ$ through the Class 0 to Class I stage. Near the base of each blue-shifted outflow lobe, we extract representative spectra, where rotation diagram fitting of the H$_2$ lines is combined with the outflow width and H$_2$ line velocity to measure the mass-loss rates. The rotation diagrams show a warm $\sim 600$ K, component with two orders of magnitude more mass than the hot, 1500-3000 K component. The H$_2$ outflow mass-loss rates decline by two orders of magnitude from the Class 0 to Class II stage and are correlated with bolometric luminosity. The declining warm H$_2$ mass loss rates and increasing opening angles from the Class 0 to I stages, and the absence of H$_2$ jets in the Class I sources, are consistent with the predictions of MHD disk wind models.

astro-ph.SR↗
arXiv2026

JOYS: Linking the molecular ice and gas-phase composition towards the high-mass hot core IRAS 18089-1732

Context. The formation and destruction of molecules in the interstellar medium is a complex interplay between gas-phase reactions as well as processes on grain surfaces and within icy mantles. For many decades, the gas-phase composition of the cold material towards star-forming regions could be well characterized using (sub)mm facilities. Prior to the launch of the James Webb Space Telescope (JWST), ice species other than the main constituents (H2O, CO, CO2, NH3, CH4, CH3OH) were challenging to detect due to insufficient sensitivity as well as angular and/or spectral resolution. Aims. We determine molecular ice and gas-phase column densities towards the young and embedded high-mass hot core IRAS 18089-1732 within a region of 5000 au. Methods. We use spectroscopic data from 5-28 micron obtained with JWST to derive ice column densities of H2O, SO2, OCN-, CH4, HCOO-, HCOOH, CH3CHO, CH3COOH, C2H5OH, CH3OCH3, and CH3COCH3. Gas-phase column densities of a total of 38 molecules, including, O-, N-, S-, and Si-bearing species as well as less abundant isotopologues, are inferred from sensitive molecular line observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) at 3 mm wavelengths. Results. We find comparable abundances (relative to C2H5OH or CH3OH) in both phases for C2H5OH, CH3OH, and CH3OCH3. The abundances of SO2 and CH3COCH3 are higher in the gas-phase suggesting additional gas-phase formation routes. The abundance of CH3CHO is one order of magnitude higher in the ices compared to the gas-phase. The ice abundances (relative to H2O ice) towards the IRAS 18089 hot core are similar to previously studied Galactic low- and high-mass protostars. There are hints of a decreasing abundance with Galactocentric distance for OCN-, CH3OH, and CH3CHO ice. (abridged)

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arXiv2026

Unlocking accretion rate diagnostics for high-mass protostars using JWST/MIRI HI lines

While many aspects of high-mass star formation have been investigated, the accretion onto the central protostars is one of the most fundamental but less explored physical properties. JWST/MIRI offers a unique opportunity to explore tracers of accretion at less-extincted wavelengths (5 to 27 um) than those studied so far. We probe the MIRI (MRS/IFU) capability to detect and resolve atomic Hydrogen (HI) emission lines in such embedded objects, to subsequently estimate accretion luminosities (Lacc) and accretion rates (Macc) for the first time in a sample of high-mass star forming regions at different evolutionary stages. We use dereddened HI line luminosities as tracers of accretion by applying existing line-to-accretion-luminosity relations (Lacc-calibrations). As they were originally established for low-mass Class II objects, we assess their applicability on our sample prior to estimating Macc. The infrared continuum reveals, at much higher spatial resolution than before, the location of new protostars, toward which we detect a handful of HI lines. While a few lines are secure detections, many are tentative. The most commonly detected line is HI 7-6, followed by HI 8-6 and HI 6-5. Assuming that their line fluxes are dominated by accretion, we find that two of the three existing Lacc-calibrations predict excessively high Lacc that largely exceed the corresponding L_bol, and that the third Lacc-calibration still overpredicts Lacc for some sources. Considering the given uncertainties, estimated accretion rates are only tentative. This work demonstrates the great potential of JWST/MIRI to probe HI line emission originated in the innermost regions of high-mass protostars, setting the ground floor for further investigations into accretion. While this project had the ambitious goal of robustly quantifying Macc, we have shed light on what outstanding methodological challenges remain.

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arXiv2026

The GRAVITY young stellar object survey -- XV. The star-disk interaction region of the T Tauri star DO Tau

Protoplanetary disks around young Sun-like stars are the cradles of the vast majority of detected exoplanets. Probing these disks at multiple spatial scales is key to uncovering how planets form. We aim to spatially and spectrally resolve the inner disk and star-disk interaction region of the M0.3 T Tauri star DO Tau by combining two complementary techniques. We used high-resolution near-infrared spectra from CFHT/SPIRou to constrain the magnetospheric star-disk interaction process and optical long-baseline interferometry with ESO VLTI/GRAVITY to determine the sizes of the K-band continuum and Br$γ$ line emitting regions. From the SPIRou spectra, we confirmed that this ~0.5 M$_\odot$ star is a strong accretor. The HI and HeI lines exhibit strong variability on a daily timescale, consistent with the burster classification of DO Tau derived from its K2 light curve. We derived an upper limit of 0.35 on the ratio between the magnetospheric truncation radius and the disk corotation radius, indicative of an ordered unstable accretion regime. The size of the Br$γ$ line emitting region obtained from GRAVITY is much smaller than the K-band continuum emitting region. This compact Br$γ$ emission region ($R_{Brγ} \sim$ 0.011 au) suggests that most of the line flux originates from the magnetospheric accretion region and/or from an inner wind close to the magnetosphere-disk interface. The inclination we derived for the inner disk (45-55°) differs from that of the outer disk inferred from the ALMA continuum (30°). This points toward a misalignment or warp of the outer disk that may originate from the suspected past encounter with the neighboring HV Tau system.

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arXiv2026

Diverse stages of star formation in the IRAS 18162-2048 region. Emergence of UV Feedback

Methods: We obtained adaptive optics-assisted integral field spectroscopy in the near-infrared (IR) $K$ band ($1.93-2.47 \mathrm{μm}$) with VLT/SINFONI, complemented by VLA X and C bands (3$-$6 cm) and ALMA band 3 ($\sim$3.3 mm) observations. Results: The near-IR continuum reveals two infrared sources, IRS 2 and IRS 7, while the main protostellar core IRAS 18162-2048 remains undetected up to $2.47 \mathrm{μm}$. IRS 7 shows a peculiar Hydrogen Recombination Line Br$γ$ profile with a narrow emission component superimposed on a broad absorption feature, consistent with a B2/B3 zero-age main-sequence star. Extended H$_2$ emission exhibits a `sawtooth' pattern in the excitation diagram, characteristic of UV radiation in a PDR rather than shock excitation. The radiative transfer model Cloudy reproduces the H$_2$ ro-vibrational populations for $T_\mathrm{gas}=600$ K and $n_\mathrm{H}=7.9\times10^3 \mathrm{cm^{-3}}$. VLA X and C bands observations reveal a compact radio source previously reported as a stationary condensation (SC) and coincident with IRS 7. For the first time, we detect IRS 7/SC in mm wavelengths. The spectral index in the 3$-$6 cm and 3.3 mm regime is consistent with optically thin free-free emission. Conclusions: Our near-IR and radio observations reveal that IRS 7/SC is a B2/B3 ZAMS star that has begun to photoionise its environment, giving rise to an extended PDR and a compact \ion{H}{ii} region. The coexistence of this source with the deeply embedded protostar IRAS 18162-2048 and other bubble-like structures in the field, suggests a multigenerational star-forming environment. Future \textit{James Webb Space Telescope} observations targeting the H$_2$ pure rotational lines ($3-28 \mathrm{μm}$) and other HRLs less affected by extinction will be essential to characterise the cooler molecular and ionised gas to fully disclose the formation history of the region.

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arXiv2026

JOYS: JWST MIRI/MRS spectra of the inner 500 au region of the L1527 IRS bipolar outflow

This study characterized the physical and kinematic properties within the innermost 500 au region of the L1527 bipolar outflow, a class 0/I low-mass protostar using JWST MIRI/MRS spectroscopy across 5-28 micron at 0.2-1.0 arcsec resolution. We identified emission lines from molecular and ionized species and analyzed their spatial morphology using line-integrated intensity maps. We derived gas temperatures and column densities through excitation diagram analysis of H2 rotational lines and compared results with shock models. The observations reveal extended molecular hydrogen emission tracing the bipolar outflow, with the H2 gas temperatures distributed into warm (~550 K) and hot (~2500 K) components, likely originating from moderate-velocity J-type shocks and some UV irradiation. We detect forbidden atomic and ionized emission lines of [Ni ii], [Ar ii], [Ne ii], [Ne iii], [S i], and [Fe ii] showing spatially extended morphology. Double-peaked emission profiles were seen in [Ar ii], [Ne iii], and [Fe ii], in the eastern region, suggesting that the high velocity component traces a fast, highly ionized jet. A radial velocity map derived from [Ne ii] emission shows the eastern region to be redshifted and the western region blueshifted, contrary to earlier interpretations. The analysis of the MIRI/MRS observations reveals molecular, atomic, and ionized emission lines in this low-mass protostar connected with active outflow signatures. The most striking feature discovered is the presence of a poorly collimated high-velocity ionized jet, embedded within a broader wide-angle molecular outflow likely driven by a disk wind. The coexistence of these components supports a stratified outflow structure and suggests that L1527 exhibits unique jet-launching characteristics atypical of its early evolutionary stage.

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arXiv2025

The Outbursting YSOs Catalogue (OYCAT)

YSOs can display unpredictable and high-amplitude rises in brightness that can last from a few months to possibly over 100 years. These types of outbursts are explained by large changes in the mass accretion rate from the disk onto the central star. The outbursts support to a model of star formation (episodic accretion) where stars would spend most of their lifetimes accreting at low rates, and gain most of their mass through these short-lived accretion outbursts. The universality of episodic accretion, as well as its potential impact on stellar and planetary formation are still under debate. Improvement on the statistics of the members of the eruptive class is needed to better understand the episodic accretion phenomenon and its universality across different mass regimes and environments. In this paper we collect published information on the spectroscopic and photometric characteristics of 174 YSOs confirmed to belong to the eruptive variable class. We classify these objects into five different sub-classes (we find 49 FUor, 20 FUor-like, 16 EX Lupi-type, 81 Peculiar/V1647 Ori-like/MNors and 8 Periodic YSOs). The classification follows what has been done previously in the literature, and it is not an attempt to redefine these classes. In addition, we present a list of 18 embedded, and 6 massive YSOs, as additional categories of eruptive variable YSOs. Due to the complexity and/or faintness of these systems, it is hard to place them into the original classification scheme of this class of variable YSOs. Finally, we present a separate list of 355 candidate eruptive variable YSOs, which either lack spectroscopic information or the available spectroscopic data is not sufficient for an unambiguous classification. The online catalogue of confirmed and candidate eruptive YSOs will be maintained and updated in the future to serve as an important reference for the star formation community.

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arXiv2025

MINDS: Detection of an inner gas disk caused by evaporating bodies around HD 172555

Mechanisms such as collisions of rocky bodies or cometary activity give rise to dusty debris disks. Debris disks trace the leftover building blocks of planets, and thus also planetary composition. HD 172555, a stellar twin of beta Pic, hosts a debris disk thought to have resulted from a giant collision. It is known for its extreme mid-infrared silica dust feature, indicating a warm population of silica-rich grains in the asteroid belt (~5 au), cold CO observed by ALMA, and small bodies evaporating as they approach close to the star. Our JWST MIRI/MRS observations now reveal emission from an inner gaseous disk (<0.5 au) that arises from the evaporation of close-in material. For the first time in a debris disk, we detect neutral atomic chlorine and sulfur, as well as ionized nickel. We recovered the neutral sulfur line in ~20-year-old Spitzer data, showing it is long-lived and stable. Ionized iron, previously seen only in beta Pic, is also detected. All lines are broadened by Keplerian rotation, pinpointing the gas location. The HD 172555 system serves as a unique laboratory to study the composition of planetesimals, asteroids, and comets beyond the Solar System. The comparison to beta Pic reveals, that the gas in HD 172555 is hotter, closer to the star, and poor in argon -- suggesting it originates from evaporating rocky bodies near the star, while beta Pic's gas may trace volatile-rich bodies from larger separations.

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arXiv2025

JWST Observations of Young protoStars (JOYS): overview of program and early results

The embedded phase is a crucial period in the development of a young star. Mid-IR observations, now possible with JWST with unprecedented sensitivity, spectral resolution and sharpness are key for probing many physical and chemical processes on sub-arcsecond scales. JOYS addresses a wide variety of questions, from protostellar accretion and the nature of primeval jets, winds and outflows, to the chemistry of gas and ice, and the characteristics of embedded disks. We introduce the program and show representative results. MIRI-MRS data of 17 low-mass and 6 high-mass protostars show a wide variety of features. Atomic line maps differ among refractory (e.g., Fe), semi-refractory (e.g., S) and volatile elements (e.g., Ne), linked to their different levels of depletion and local (shock) conditions. Nested, stratified jet structures consisting of an inner ionized core seen in [Fe II] with an outer H2 layer are commonly seen. Wide-angle winds are found in low-J H2 lines. [S I] follows the jet in the youngest protostars, but is concentrated on source when more evolved. [Ne II] reveals a mix of jet shock and photoionized emission. H I lines measure accretion, but are also associated with jets. Molecular emission (CO2, C2H2, HCN, H2O, ..) is cool compared with disks, and likely associated with hot cores. Deep ice absorption features reveal not just the major ice components but also ions (as part of salts) and complex organic molecules, with comparable abundances from low- to high-mass sources. A second detection of HDO ice in a solar-mass source is presented with HDO/H2O ~ 0.4%, providing a link with disks and comets. A deep search for solid O2 suggests it is not a significant oxygen reservoir. Only few embedded Class I disks show the same forest of water lines as Class II disks do, perhaps due to significant dust extinction of the upper layers [abridged].

astro-ph.GA↗
arXiv2025

MINDS: The very low-mass star and brown dwarf sample. Detections and trends in the inner disk gas

Planet-forming disks around brown dwarfs and very low-mass stars (VLMS) are on average less massive and are expected to undergo faster radial solid transport than their higher mass counterparts. Spitzer had detected C$_2$H$_2$, CO$_2$ and HCN around these objects. With better sensitivity and spectral resolving power, JWST recently revealed incredibly carbon-rich spectra from such disks. A study of a larger sample of objects is necessary to understand how common such carbon-rich inner disk regions are and to put constraints on their evolution. We present and analyze MIRI observations of 10 disks around VLMS from the MIRI GTO program. This sample is diverse, with the central object ranging in mass from 0.02 to 0.14 $M_{\odot}$. They are located in three star-forming regions and a moving group (1-10 Myr). We identify molecular emission in all sources and report detection rates. We compare the molecular flux ratios between different species and to dust emission strengths. We also compare the flux ratios with the stellar and disk properties. The spectra of these VLMS disks are extremely molecular rich, and we detect the 10 $μ$m silicate dust emission feature in 70% of the sample. We detect C$_2$H$_2$ and HCN in all of the sources and find larger hydrocarbons such as C$_4$H$_2$ and C$_6$H$_6$ in nearly all sources. Among O-bearing molecules, we find firm detections of CO$_2$, H$_2$O, and CO in 90%, 50%, and 20% of the sample, respectively. We find that the detection rates of organic molecules correlate with other organic molecules and anti-correlate with inorganic molecules. Hydrocarbon-rich sources show a weaker 10$μ$m dust strength as well as lower disk dust mass than the oxygen-rich sources. We find potential evidence for C/O enhancement with disk age. The observed trends are consistent with models that suggest rapid inward solid material transport and grain growth.

astro-ph.EP↗
arXiv2025

Mid-infrared extinction curve for protostellar envelopes from JWST-detected embedded jet emission: the case of TMC1A

Context: Dust grains are key components of the interstellar medium and play a central role in star formation, acting as catalysts for chemical reactions and as building blocks of planets. Extinction curves are essential for characterizing dust properties, but mid-infrared (MIR) extinction remains less constrained in protostellar environments. Gas-phase line ratios from embedded protostellar jets provide a spatially resolved method for probing extinction through protostellar envelopes, complementing background starlight approaches. Aims: We aim to derive MIR extinction curves along sightlines toward a protostellar jet embedded in an envelope and assess whether they differ from those in dense molecular clouds. Methods: We analyze JWST NIRSpec IFU and MIRI MRS observations of four positions along the blue-shifted TMC1A jet. We extract observed [Fe II] line intensities and model intrinsic ratios using the Cloudy spectral synthesis code across a range of electron densities and temperatures. By comparing observed near-IR (NIR) and MIR line ratios to Cloudy predictions, we infer the relative extinction between NIR and MIR wavelengths. Results: Electron densities (ne) derived from NIR [Fe II] lines range from ~5 x 10^4 to ~5 x 10^3 cm^-3 at scales <~350 AU. MIR extinction values show stronger reddening than the empirical dark cloud curve from McClure (2009) at similar ne and temperatures (~10^3 to 10^4 K). If MIR emission arises from cooler, lower-density gas, extinction curves remain consistent with background starlight measurements. Conclusions: This method enables spatially resolved MIR extinction curves in embedded protostellar systems. Results suggest either a change in dust size distribution (e.g., from grain growth) or that MIR emission originates from cooler, less dense regions than NIR emission. (Abstract shortened for arXiv. See PDF for full version.)

astro-ph.SR↗
arXiv2025

Mid-infrared evidence for iron-rich dust in the multi-ringed inner disk of HD 144432

Context. Rocky planets form by the concentration of solid particles in the inner few au regions of planet-forming disks. Their chemical composition reflects the materials in the disk available in the solid phase at the time the planets were forming. Aims. We aim to constrain the structure and dust composition of the inner disk of the young star HD 144432, using an extensive set of infrared interferometric data taken by the Very Large Telescope Interferometer (VLTI), combining PIONIER, GRAVITY, and MATISSE observations. Methods. We introduced a new physical disk model, TGMdust, to image the interferometric data, and to fit the disk structure and dust composition. We also performed equilibrium condensation calculations with GGchem. Results. Our best-fit model has three disk zones with ring-like structures at 0.15, 1.3, and 4.1 au. Assuming that the dark regions in the disk at ~0.9 au and at ~3 au are gaps opened by planets, we estimate the masses of the putative gap-opening planets to be around a Jupiter mass. We find evidence for an optically thin emission ($τ<0.4$) from the inner two disk zones ($r<4$ au) at $λ>3\ μ$m. Our silicate compositional fits confirm radial mineralogy gradients. To identify the dust component responsible for the infrared continuum emission, we explore two cases for the dust composition, one with a silicate+iron mixture and the other with a silicate+carbon one. We find that the iron-rich model provides a better fit to the spectral energy distribution. Conclusions. We propose that in the warm inner regions ($r<5$ au) of typical planet-forming disks, most if not all carbon is in the gas phase, while iron and iron sulfide grains are major constituents of the solid mixture along with forsterite and enstatite. Our analysis demonstrates the need for detailed studies of the dust in inner disks with new mid-infrared instruments such as MATISSE and JWST/MIRI.

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