arXiv subjects

G. Perotti

Publications and source records attributed to G. Perotti.

At least 19 recordsLinked to original sources

arXiv2026

MINDS survey of silicates in T Tauri disks: Correlation between dust and gas

Context. Silicates are key constituents of planet-forming disks and major building blocks of rocky planets. Mid-infrared spectral features of micron-sized silicate grains trace grain growth, mineralogy, and disk chemistry. Aims. We characterized the dust mineralogy in T Tauri disks using James Webb Space Telescope (JWST)/Mid-Infrared Instrument (MIRI) observations and investigated the connections between the dust and molecular gas compositions. Methods. We analyzed JWST/MIRI spectra of 26 disks from the MIRI mid-Infrared Disk Survey (MINDS). Using our DustComp spectral decomposition tool, we inferred the mass fractions of individual dust species. The fits included Mg$_2$SiO$_4$ (forsterite), MgSiO$_3$ (enstatite), and SiO$_2$ (silica), together with amorphous silicates of corresponding stoichiometry. Results. Mg-rich (and Fe-poor) silicates reproduce the data well, with residuals typically within $\pm3\%$. Grain size distributions are skewed toward sizes larger than $2\mu$m, indicating significant growth. The average dust composition is dominated by Mg$_2$SiO$_4$-stoichiometry grains ($\sim60\%$), followed by MgSiO$_3$ ($\sim30\%$) and SiO$_2$ ($\sim10\%$). Crystalline mass fractions are typically in the $5$-$24\%$ range, with a mean of $14\%$. Annealed silica is robustly detected in nine objects, with cristobalite as the main polymorph. We found a correlation between dust and molecular gas composition: disks with strong annealed silica features show stronger CO$_2$ emission, while forsterite-rich disks display stronger H$_2$O emission. Disks with annealed silica features may also have elevated gas-phase C/O ratios. Conclusions. The observed dust-gas correlation may provide the first indication that the molecular gas composition regulates the availability of dust species in the inner disk.

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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

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

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 $\mu$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$\mu$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.

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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].

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arXiv2024

Ice inventory towards the protostar Ced 110 IRS4 observed with the James Webb Space Telescope. Results from the ERS Ice Age program

This work focuses on the ice features toward the binary protostellar system Ced 110 IRS 4A and 4B, and observed with JWST as part of the Early Release Science Ice Age collaboration. We aim to explore the JWST observations of the binary protostellar system Ced~110~IRS4A and IRS4B to unveil and quantify the ice inventories toward these sources. We compare the ice abundances with those found for the same molecular cloud. The analysis is performed by fitting or comparing laboratory infrared spectra of ices to the observations. Spectral fits are carried out with the ENIIGMA fitting tool that searches for the best fit. For Ced~110~IRS4B, we detected the major ice species H$_2$O, CO, CO$_2$ and NH$_3$. All species are found in a mixture except for CO and CO$_2$, which have both mixed and pure ice components. In the case of Ced~110~IRS4A, we detected the same major species as in Ced~110~IRS4B, as well as the following minor species CH$_4$, SO$_2$, CH$_3$OH, OCN$^-$, NH$_4^+$ and HCOOH. Tentative detection of N$_2$O ice (7.75~$\mu$m), forsterite dust (11.2~$\mu$m) and CH$_3^+$ gas emission (7.18~$\mu$m) in the primary source are also presented. Compared with the two lines of sight toward background stars in the Chameleon I molecular cloud, the protostar has similar ice abundances, except in the case of the ions that are higher in IRS4A. The clearest differences are the absence of the 7.2 and 7.4~$\mu$m absorption features due to HCOO$^-$ and icy complex organic molecules in IRS4A and evidence of thermal processing in both IRS4A and IRS4B as probed by the CO$_2$ ice features. We conclude that the binary protostellar system Ced~110~IRS4A and IRS4B has a large inventory of icy species. The similar ice abundances in comparison to the starless regions in the same molecular cloud suggest that the chemical conditions of the protostar were set at earlier stages in the molecular cloud.

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arXiv2024

Infrared Spectra of Solid-State Ethanolamine: Laboratory Data in Support of JWST Observations

Ethanolamine (NH$_2$CH$_2$CH$_2$OH, EA) has been identified in the gas phase of the ISM within molecular clouds. Although EA has not been directly observed in the molecular ice phase, a solid state formation mechanism has been proposed. However, the current literature lacks an estimation of the infrared band strengths of EA ices. We conducted an experimental investigation of solid EA ice at low temperatures to ascertain its infrared band strengths, phase transition temperature, and multilayer binding energy. The commonly used laser interferometry method was not applied. Infrared band strengths were determined using three distinct methods. The obtained lab spectrum of EA was compared with the publicly available MIRI MRS James Webb Space Telescope observations toward a low mass protostar. The phase transition temperature for EA ice falls within the range of 175 to 185 K. Among the discussed methods, the simple pressure gauge method provides a reasonable estimate of band strength. We derive a band strength value of about $1\times10^{-17}$ cm molecule$^{-1}$ for the NH$_2$ bending mode in the EA molecules. Additionally, temperature-programmed desorption analysis yielded a multilayer desorption energy of 0.61$\pm$0.01 eV. By comparing the laboratory data documented in this study with the JWST spectrum of the low mass protostar IRAS 2A, an upper-limit for the EA ice abundances was derived.

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arXiv2024

JOYS+: link between ice and gas of complex organic molecules. Comparing JWST and ALMA data of two low-mass protostars

A rich inventory of complex organic molecules (COMs) has been observed in high abundances in the gas phase toward Class 0 protostars. These molecules are suggested to be formed in ices and sublimate in the warm inner envelope close to the protostar. However, only the most abundant COM, methanol (CH3OH), has been firmly detected in ices before the era of James Webb Space Telescope (JWST). Now it is possible to detect the interstellar ices of other COMs and constrain their ice column densities quantitatively. We aim to determine the column densities of several oxygen-bearing COMs (O-COMs) in both gas and ice for two low-mass protostellar sources, NGC 1333 IRAS 2A and B1-c, as case studies in our JWST Observations of Young protoStars (JOYS+) program. By comparing the column density ratios w.r.t. CH3OH between both phases measured in the same sources, we can probe into the evolution of COMs from ice to gas in the early stages of star formation. We are able to fit the fingerprints range of COM ices between 6.8 and 8.8 um in the JWST/MIRI-MRS spectra of B1-c using similar components as recently used for IRAS 2A. We claim detection of CH4, OCN-, HCOO-, HCOOH, CH3CHO, C2H5OH, CH3OCH3, CH3OCHO, and CH3COCH3 in B1-c, and upper limits are estimated for SO2, CH3COOH, and CH3CN. The comparison of O-COM ratios w.r.t CH3OH between ice and gas shows two different cases. 1) the column density ratios of CH3OCHO and CH3OCH3 match well between the two phases, which may be attributed to a direct inheritance from ice to gas or strong chemical links with CH3OH. 2) the ice ratios of CH3CHO and C2H5OH w.r.t. CH3OH are higher than the gas ratios by 1-2 orders of magnitudes. This difference can be explained by the gas-phase reprocessing following sublimation, or different spatial distributions of COMs in the envelope.

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arXiv2024

A JWST/MIRI analysis of the ice distribution and PAH emission in the protoplanetary disk HH 48 NE

Ice-coated dust grains provide the main reservoir of volatiles that play an important role in planet formation processes and may become incorporated into planetary atmospheres. However, due to observational challenges, the ice abundance distribution in protoplanetary disks is not well constrained. We present JWST/MIRI observations of the edge-on disk HH 48 NE carried out as part of the IRS program Ice Age. We detect CO$_2$, NH$_3$, H$_2$O and tentatively CH$_4$ and NH$_4^+$. Radiative transfer models suggest that ice absorption features are produced predominantly in the 50-100 au region of the disk. The CO$_2$ feature at 15 micron probes a region closer to the midplane (z/r = 0.1-0.15) than the corresponding feature at 4.3 micron (z/r = 0.2-0.6), but all observations trace regions significantly above the midplane reservoirs where we expect the bulk of the ice mass to be located. Ices must reach a high scale height (z/r ~ 0.6; corresponding to modeled dust extinction Av ~ 0.1), in order to be consistent with the observed vertical distribution of the peak ice optical depths. The weakness of the CO$_2$ feature at 15 micron relative to the 4.3 micron feature and the red emission wing of the 4.3 micron CO$_2$ feature are both consistent with ices being located at high elevation in the disk. The retrieved NH$_3$ abundance and the upper limit on the CH$_3$OH abundance relative to H$_2$O are significantly lower than those in the interstellar medium (ISM), but consistent with cometary observations. Full wavelength coverage is required to properly study the abundance distribution of ices in disks. To explain the presence of ices at high disk altitudes, we propose two possible scenarios: a disk wind that entrains sufficient amounts of dust, thus blocking part of the stellar UV radiation, or vertical mixing that cycles enough ices into the upper disk layers to balance ice photodesorption.

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arXiv2024

Planet Formation and Disk Chemistry: Dust and Gas Evolution during Planet Formation

Over the past decade, progress in observational capabilities, combined with theoretical advancements, have transformed our comprehension of the physics and chemistry during planet formation. Despite these important steps forward, open questions persist on the chemical and physical evolution of solids in their journey from the collapsing molecular cores to disks and planetary bodies. This chapter is a repository of such burning questions. It has the ambition to identify the most promising avenues for future research based on current observational and modeling opportunities.

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arXiv2024

Abundant hydrocarbons in the disk around a very-low-mass star

Very low-mass stars (those <0.3 solar masses) host orbiting terrestrial planets more frequently than other types of stars, but the compositions of those planets are largely unknown. We use mid-infrared spectroscopy with the James Webb Space Telescope to investigate the chemical composition of the planet-forming disk around ISO-ChaI 147, a 0.11 solar-mass star. The inner disk has a carbon-rich chemistry: we identify emission from 13 carbon-bearing molecules including ethane and benzene. We derive large column densities of hydrocarbons indicating that we probe deep into the disk. The high carbon to oxygen ratio we infer indicates radial transport of material within the disk, which we predict would affect the bulk composition of any planets forming in the disk.

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arXiv2024

MINDS: JWST/NIRCam imaging of the protoplanetary disk PDS 70

Context. Two protoplanets have recently been discovered within the PDS 70 protoplanetary disk. JWST/NIRCam offers a unique opportunity to characterize them and their birth environment at wavelengths difficult to access from the ground. Aims. We aim to image the circumstellar environment of PDS 70 at 1.87 $\mu$m and 4.83 $\mu$m, assess the presence of Pa-$\alpha$ emission due to accretion onto the protoplanets, and probe any IR excess indicative of heated circumplanetary material. Methods. We obtain non-coronagraphic JWST/NIRCam images of PDS 70 within the MINDS (MIRI mid-INfrared Disk Survey) program. We leverage the Vortex Image Processing (VIP) package for data reduction, and develop dedicated routines for optimal stellar PSF subtraction, unbiased imaging of the disk, and protoplanet flux measurement in this type of dataset. A radiative transfer model of the disk is used to disentangle the contributions from the disk and the protoplanets. Results. We re-detect both protoplanets and identify extended emission after subtracting a disk model, including a large-scale spiral-like feature. We interpret its signal in the direct vicinity of planet c as tracing the accretion stream feeding its circumplanetary disk, while the outer part of the feature may rather reflect asymmetric illumination of the outer disk. We also report a bright signal consistent with a previously proposed protoplanet candidate enshrouded in dust, near the 1:2:4 mean-motion resonance with planets b and c. The 1.87 $\mu$m flux of planet b is consistent with atmospheric model predictions, but not that of planet c. We discuss potential origins for this discrepancy, including significant Pa-$\alpha$ line emission. The 4.83 $\mu$m fluxes of planets b and c suggest enshrouding dust or heated CO emission from their circumplanetary environment.

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arXiv2024

JOYS: MIRI/MRS spectroscopy of gas-phase molecules from the high-mass star-forming region IRAS 23385+6053

Space-based mid-IR spectroscopy provides tracers of warm gas in star-forming regions that are inaccessible from the ground. Past mid-IR spectra of bright high-mass protostars in the hot-core phase typically showed strong absorption features from molecules such as CO$_2$, C$_2$H$_2$, and HCN. However, little is known about their fainter counterparts at earlier stages. We thus aim to characterize the gas-phase molecular features in JWST MIRI/MRS observations of the young high-mass star-forming region IRAS 23385+6053. Spectra were extracted from two mid-IR sources and three H$_2$ bright outflow knots in the MIRI/MRS field of view. Rich molecular spectra with emission from CO, H$_2$, HD, H$_2$O, C$_2$H$_2$, HCN, CO$_2$, and OH are detected towards the two mid-IR sources. However, only CO and OH are seen towards the brightest H$_2$ knots, suggesting that the majority of the observed species are associated with disks or hot core regions rather than outflows. Simple Local thermodynamic equilibrium (LTE) slab models were used to fit the observed molecular features. The LTE model fits to $^{12}$CO$_{2}$, C$_{2}$H$_{2}$, and HCN emission suggest warm $120-200$ K emission arising from a disk surface around one or both protostars. Weak $\sim500$ K H$_2$O emission at $\sim$ 6-7 $\mu$m is detected towards one mid-IR source, whereas $250-1050$ K H$_2$O absorption is found in the other. The H$_2$O absorption may occur in the disk atmosphere due to strong accretion-heating of the midplane, or in a disk wind viewed at an ideal angle for absorption. CO emission may originate in the hot inner disk or outflow shocks. OH emission is likely excited in a non-LTE manner through water photodissociation or chemical formation. The observations are consistent with disks having already formed in the young IRAS 23385+6053 system, but further observations are needed to disentangle the effects of geometry and evolution.

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arXiv2023

JWST Observations of Young protoStars (JOYS+): Detection of icy complex organic molecules and ions. I. CH$_4$, SO$_2$, HCOO$^-$, OCN$^-$, H$_2$CO, HCOOH, CH$_3$CH$_2$OH, CH$_3$CHO, CH$_3$OCHO, CH$_3$COOH

Complex organic molecules (COMs) detected in the gas phase are thought to be mostly formed on icy grains, but no unambiguous detection of icy COMs larger than CH3OH has been reported so far. Exploring this matter in more detail has become possible with the JWST the critical 5-10 $\mu$m range. In the JOYS+ program, more than 30 protostars are being observed with the MIRI/MRS. This study explores the COMs ice signatures in the low and high-mass protostar, IRAS 2A and IRAS 23385, respectively. We fit continuum and silicate subtracted observational data with IR laboratory ice spectra. We use the ENIIGMA fitting tool to find the best fit between the lab data and the observations and to performs statistical analysis of the solutions. We report the best fits for the spectral ranges between 6.8 and 8.6 $\mu$m in IRAS 2A and IRAS 23385, originating from simple molecules, COMs, and negative ions. The strongest feature in this range (7.7 $\mu$m) is dominated by CH4 and has contributions of SO2 and OCN-. Our results indicate that the 7.2 and 7.4 $\mu$m bands are mostly dominated by HCOO-. We find statistically robust detections of COMs based on multiple bands, most notably CH3CHO, CH3CH2OH, and CH3OCHO. The likely detection of CH3COOH is also reported. The ice column density ratios between CH3CH2OH and CH3CHO of IRAS 2A and IRAS 23385, suggests that these COMs are formed on icy grains. Finally, the derived ice abundances for IRAS 2A correlate well with those in comet 67P/GC within a factor of 5. Based on the MIRI/MRS data, we conclude that COMs are present in interstellar ices, thus providing additional proof for a solid-state origin of these species in star-forming regions. The good correlation between the ice abundances in comet 67P and IRAS 2A is in line with the idea that cometary COMs can be inherited from the early protostellar phases.

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arXiv2023

JOYS+: mid-infrared detection of gas-phase SO$_2$ emission in a low-mass protostar. The case of NGC 1333 IRAS2A: hot core or accretion shock?

JWST/MIRI has sharpened our infrared eyes toward the star formation process. This paper presents the first mid-infrared detection of gaseous SO$_2$ emission in an embedded low-mass protostellar system. MIRI-MRS observations of the low-mass protostellar binary NGC 1333 IRAS2A are presented from the JWST Observations of Young protoStars (JOYS+) program, revealing emission from the SO$_2~\nu_3$ asymmetric stretching mode at 7.35 micron. The results are compared to those derived from high-angular resolution SO$_2$ data obtained with ALMA. The SO$_2$ emission from the $\nu_3$ band is predominantly located on $\sim50-100$ au scales around the main component of the binary, IRAS2A1. A rotational temperature of $92\pm8$ K is derived from the $\nu_3$ lines. This is in good agreement with the rotational temperature derived from pure rotational lines in the vibrational ground state (i.e., $\nu=0$) with ALMA ($104\pm5$ K). However, the emission of the $\nu_3$ lines is not in LTE given that the total number of molecules predicted by a LTE model is found to be a factor $2\times10^4$ higher than what is derived for the $\nu=0$ state. This difference can be explained by a vibrational temperature that is $\sim100$ K higher than the derived rotational temperature of the $\nu=0$ state. The brightness temperature derived from the continuum around the $\nu_3$ band of SO$_2$ is $\sim180$ K, which confirms that the $\nu_3=1$ level is not collisionally populated but rather infrared pumped by scattered radiation. This is also consistent with the non-detection of the $\nu_2$ bending mode at 18-20 micron. Given the rotational temperature, the extent of the emission ($\sim100$ au in radius), and the narrow line widths in the ALMA data (3.5 km/s), the SO$_2$ in IRAS2A likely originates from ice sublimation in the central hot core around the protostar rather than from an accretion shock at the disk-envelope boundary.

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arXiv2023

JOYS: Disentangling the warm and cold material in the high-mass IRAS 23385+6053 cluster

(abridged) We study and compare the warm (>100 K) and cold (<100 K) material toward the high-mass star-forming region IRAS 23385+6053 (IRAS 23385 hereafter) combining high angular resolution observations in the mid-infrared (MIR) with the JWST Observations of Young protoStars (JOYS) project and with the NOEMA at mm wavelengths at angular resolutions of 0.2"-1". The spatial morphology of atomic and molecular species is investigated by line integrated intensity maps. The temperature and column density of different gas components is estimated using H2 transitions (warm and hot component) and a series of CH3CN transitions as well as 3 mm continuum emission (cold component). Toward the central dense core in IRAS 23385 the material consists of relatively cold gas and dust (~50 K), while multiple outflows create heated and/or shocked H2 and show enhanced temperatures (~400 K) along the outflow structures. An energetic outflow with enhanced emission knots of [Fe II] and [Ni II] hints at J-type shocks, while two other outflows have enhanced emission of only H2 and [S I] caused by C-type shocks. The latter two outflows are also more prominent in molecular line emission at mm wavelengths (e.g., SiO, SO, H2CO, and CH3OH). Even higher angular resolution data are needed to unambiguously identify the outflow driving sources given the clustered nature of IRAS 23385. While most of the forbidden fine structure transitions are blueshifted, [Ne II] and [Ne III] peak at the source velocity toward the MIR source A/mmA2 suggesting that the emission is originating from closer to the protostar.

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arXiv2023

A JWST inventory of protoplanetary disk ices: The edge-on protoplanetary disk HH 48 NE, seen with the Ice Age ERS program

Ices are the main carriers of volatiles in protoplanetary disks and are crucial to our understanding of the chemistry that ultimately sets the organic composition of planets. The ERS program Ice Age on the JWST follows the ice evolution through all stages of star and planet formation. JWST/NIRSpec observations of the edge-on Class II protoplanetary disk HH~48~NE reveal spatially resolved absorption features of the major ice components H$_2$O, CO$_2$, CO, and multiple weaker signatures from less abundant ices NH$_3$, OCN$^-$, and OCS. Isotopologue $^{13}$CO$_2$ ice has been detected for the first time in a protoplanetary disk. Since multiple complex light paths contribute to the observed flux, the ice absorption features are filled in by ice-free scattered light. The $^{12}$CO$_2$/$^{13}$CO$_2$ ratio of 14 implies that the $^{12}$CO$_2$ feature is saturated, without the flux approaching 0, indicative of a very high CO$_2$ column density on the line of sight, and a corresponding abundance with respect to hydrogen that is higher than ISM values by a factor of at least a few. Observations of rare isotopologues are crucial, as we show that the $^{13}$CO$_2$ observation allows us to determine the column density of CO$_2$ to be at an order of magnitude higher than the lower limit directly inferred from the observed optical depth. Radial variations in ice abundance, e.g., snowlines, are significantly modified since all observed photons have passed through the full radial extent of the disk. CO ice is observed at perplexing heights in the disk, extending to the top of the CO-emitting gas layer. We argue that the most likely interpretation is that we observe some CO ice at high temperatures, trapped in less volatile ices like H$_2$O and CO$_2$. Future radiative transfer models will be required to constrain the implications on our current understanding of disk physics and chemistry.

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arXiv2023

Linking ice and gas in the Coronet cluster in Corona Australis

During the journey from the cloud to the disc, the chemical composition of the protostellar envelope material can be either preserved or processed to varying degrees depending on the surrounding physical environment. This works aims to constrain the interplay of solid (ice) and gaseous methanol (CH$_3$OH) in the outer regions of protostellar envelopes located in the Coronet cluster in Corona Australis (CrA), and assess the importance of irradiation by the Herbig Ae/Be star R CrA. CH$_3$OH is a prime test-case as it predominantly forms as a consequence of the solid-gas interplay (hydrogenation of condensed CO molecules onto the grain surfaces) and it plays an important role in future complex molecular processing. We present 1.3 mm Submillimeter Array (SMA) and Atacama Pathfinder Experiment (APEX) observations towards the envelopes of four low-mass protostars in the Coronet. Eighteen molecular transitions of seven species are identified. We calculate CH$_3$OH gas-to-ice ratios in this strongly irradiated cluster and compare them with ratios determined towards protostars located in less irradiated regions such as the Serpens SVS 4 cluster in Serpens Main and the Barnard 35A cloud in the $\lambda$ Orionis region. The CH$_3$OH gas-to-ice ratios in the Coronet vary by one order of magnitude (from 1.2$\times$10$^{-4}$ to 3.1$\times$10$^{-3}$) which is similar to less irradiated regions as found in previous studies. We find that the CH$_3$OH gas-to-ice ratios estimated in these three regions are remarkably similar despite the different UV radiation field intensities and formation histories. This result suggests that the overall CH$_3$OH chemistry in the outer regions of low-mass envelopes is relatively independent of variations in the physical conditions and hence that it is set during the prestellar stage.

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