arXiv subjects

P. D. Klaassen

Publications and source records attributed to P. D. Klaassen.

At least 19 recordsLinked to original sources

arXiv2026

A High Velocity SiO Jet from S255N SMA3

We present ALMA Band 6 observations of the compact source SMA3 in the S255IR region, analysing both SiO (J = 5-4, 6-5) and CS (J = 5-4) emission to characterise the structure and kinematics of its outflow. The data reveal a highly collimated bipolar jet traced by SiO, reaching line-of-sight velocities of up to $\pm$60 km s$^{-1}$ and de-projected velocities of $\pm$~80 km s$^{-1}$, with a collimation ratio of ~4.7 over a spatial extent of ~5800 au. The inferred dynamical age is 343 yr. Position-velocity diagrams exhibit a continuous velocity structure with triangular morphology, consistent with a steady disk wind rather than an episodic or X-wind-driven flow. Excitation analysis yields a characteristic SiO temperature of ~42 K, and we derive the jet mass, momentum, and kinetic energy which are indicative of a dense, mass-loaded molecular outflow. The emission shows clear chemical and kinematic differentiation: SiO traces the high-velocity jet spine, while CS is observed at lower velocities close to the protostar, and only reaches high velocities at larger distances. Despite forming within a clustered high-mass star-forming region, the jet exhibits a high degree of symmetry, collimation, and dynamical coherence more commonly associated with protostars forming in isolation or less crowded star-forming regions. This demonstrates that well-ordered, narrowly collimated, disk-driven jets can be launched and maintained even in the dense, competitive environments characteristic of high-mass star formation.

astro-ph.GA↗

arXiv2026

Spectroscopic surveys with the SKA probing the ionized and molecular Milky Way

Radio spectroscopic surveys provide us with a comprehensive picture of the Milky Way across many physical and chemical regimes. Spectral lines primarily probe the multi-phase gaseous interstellar medium (ISM) from its ionized to atomic and molecular phases, and constrain both local and galaxy-scale kinematics and structure through Doppler shifts. By investigating the physical and chemical properties and distribution of the ISM, the processes driving star formation and galaxy evolution can be studied in detail. This motivates line surveys of our Galaxy that allow us to use the range of physical conditions found in the Milky Way as a template for understanding star formation in extragalactic environments. In this chapter, we describe the science enabled by the spectroscopy of small molecules and radio recombination lines of atoms toward a range of Galactic environments with the SKA. We address questions concerning the processes that dictate the formation of molecular clouds (OH, CH), the properties of warm, ionized gas and the potential of HII regions in understanding the structure of the Galaxy (radio recombination lines), and the impact of CO-dark molecular gas across various density regimes on star formation and galaxy evolution (OH, H2CO). We propose a survey that includes the inner and outer Galaxy disk, characterized by a broad range of densities, temperatures, and metallicities. Deep, wide-field observations of small molecules will be uniquely accessible with SKA, providing key insights on the condition of interstellar medium in galaxies and its impact on star formation.

astro-ph.GA↗

arXiv2026

Protostellar Outflows at the EarliesT Stages (POETS). IX. Magnetohydrodynamic disk winds traced by SO and SO$_2$ in luminous protostars

We investigate two massive young stellar objects (YSOs), IRAS21078+5211 and G035.02+0.35, where evidence for magnetohydrodynamic (MHD) disk winds (DWs) has been obtained at scales of 10-100 au through measurements of the 22GHz water maser velocity distribution within the Protostellar Outflows at the EarliesT Stages (POETS) survey. We employ IRAM Northern Extended Millimeter Array and archival Atacama Large Millimeter Array observations of IRAS21078+5211 and G035.02+0.35, respectively, to study kinematics and physical conditions of the corresponding protostellar winds on scales of 100-1000 au using the same molecular tracers. In IRAS21078+5211, the emissions of several molecules, particularly SO, SO2, CH3CN and CH3OH, are distributed along the axis of the radio jet, and present a LSR velocity (Vlsr) gradient transversal to the jet axis. Position-velocity (PV) plots of the SO lines show patterns consistent with Keplerian rotation. The SO2 emission comes from high velocity gas flowing close to the jet axis, while CH3CN and CH3OH present larger radial extension than the S-bearing species. In G035.02+0.35, the same molecules are instead distributed along the major axis of the rotating disk, and their Vlsr gradients consistently trace the disk rotation. The corresponding PV plots present Keplerian profiles. SO is the only molecular species whose emission extends well outside the disk. In both YSOs, the spatial and velocity distributions of SO are consistent with a rotating wind magneto-centrifugally launched from the YSO disk. The comparison with models of molecule formation and excitation in shocks indicates that the different radial extension of the molecular species observed in the protostellar wind of IRAS21078+5211, as well as the lack of molecules, except SO, in the G035.02+0.35's wind, can be explained in terms of a radially extended MHD DW, rather than a compact X-wind.

astro-ph.SR↗

arXiv2026

ALMAGAL IX. The chemical complexity of AG318.9477-00.1960: A line-identification template for ALMAGAL

We present a detailed molecular line analysis of one of the most chemically rich cores in the ALMAGAL sample, the high-mass core~9 in the AG318.9477-00.1960 clump (AG318-c9), located at a heliocentric distance of \sim 10.4\,\rm kpc. We further assessed whether the emission of selected COMs, that is, ethylene glycol ((CH_2OH)_2; EG), glycolaldehyde (CH_2(OH)CHO; GA), and methyl formate (CH_3OCHO; MF), can be used to trace the innermost regions of hot molecular cores (HMCs). We analysed ALMA Band~6 observations (\sim 217-221GHz). Spectral line identification and local thermodynamic equilibrium modelling were performed using the software MADCUBA. We derived the physical parameters, including the column density (N), excitation temperature (Tex), velocity, line width, and molecular abundances relative to H_2, for all detected species. The chemical inventory of AG318-c9 was compared with that of the HMC G31.41+0.31 (G31). In addition, we performed a pixel-by-pixel analysis of EG, GA, and MF to generate spatially resolved N and Tex maps and corresponding radial profiles.

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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

ALMAGAL VI. The spatial distribution of dense cores during the evolution of cluster-forming massive clump

High-mass stars and star clusters form from the fragmentation of massive dense clumps driven by gravity, turbulence, and magnetic fields. The ALMAGAL project observed $\sim1000$ clumps at $\sim$1000\,au resolution, enabling a statistically significant characterization of this process across a large range of clump physical parameters and evolutionary stages. In this work, we investigated the spatial distribution of dense cores in the 514 massive, potentially cluster-forming, clumps hosting at least 4 cores, to trace fragmentation's initial conditions and early evolution. We used quantitative descriptors, evaluated against the clump bolometric luminosity-to-mass ratio as an indicator of evolution. Core separations were measured with the minimum spanning tree method (MST) and compared with the Jeans gravitational fragmentation theory. We used the $Q$ parameter and the mass segregation ratio, $Λ_{MSR}$, to evaluate whether cores have specific arrangements or differences depending on their masses. ALMAGAL cores are usually arranged in elliptical groups with an axis ratio $e\sim2.2$, but $e\geq$5 is also observed. A single characteristic core separation per clump is found in $\sim76$% of cases, but signatures of multiple fragmentation lengths not rare. Typical core separations are compatible with the clump-averaged thermal Jeans length, $λ^{th}_{J}$, though a population, typical of low-fragmented/young clumps, has wider separations with $l\approx3\timesλ^{th}_{J}$. The core separation decreases on average from $l\sim22000$ au in younger systems to $l\sim7000$ au in more evolved ones. Cores are typically distributed in fractal-type subclusters, with centrally concentrated patterns appearing only at later stages, but without a progressive evolutionary transition. Finally, mass segregation is found in 110 systems, with its occurrence increasing with evolution.

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arXiv2025

ALMAGAL V. Relations between the core populations and the parent clump physical properties

Context. The fragmentation of massive molecular clumps into smaller, potentially star-forming cores plays a key role in the processes of high-mass star formation. The ALMAGAL project offers high-resolution data to investigate these processes across various evolutionary stages in the Galactic plane. Aims. This study aims at correlating the fragmentation properties of massive clumps, obtained from ALMA observations, with their global physical parameters (e.g., mass, surface density, and temperature) and evolutionary indicators (such as luminosity-to-mass ratio and bolometric temperature) obtained from Herschel observations. It seeks to assess whether the cores evolve in number and mass in tandem with their host clumps, and to determine the possible factors influencing the formation of massive cores (M > 24M_\odot). Methods. We analyzed the masses of 6348 fragments, estimated from 1.4 mm continuum data for 1007 ALMAGAL clumps. Leveraging this unprecedentedly large data set, we evaluated statistical relationships between clump parameters, estimated over about 0.1 pc scales, and fragment properties, corresponding to scales of a few 1000 au, while accounting for potential biases related to distance and observational resolution. Our results were further compared with predictions from numerical simulations. Results. The fragmentation level correlates preferentially with clump surface density, supporting a scenario of density-driven fragmentation, whereas it does not show any clear dependence on total clump mass. Both the mass of the most massive core and the core formation efficiency show a broad range and increase on average by an order of magnitude in the intervals spanned by evolutionary indicators such as clump dust temperature and the luminosity-to-mass ratio. This suggests that core growth continues throughout the clump evolution, favoring clump-fed over core-fed theoretical scenarios.

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arXiv2025

Expanding the Ice Inventory of NGC 1333 IRAS 2A with INDRA using JWST Observations: Tracing Organic Refractories and Beyond

In the era of JWST, with its unprecedented sensitivity and spectral resolution, infrared spectral surveys have revealed a rich inventory of ices, including complex organic molecules (COMs), in young stellar objects (YSOs). However, robust methods to decompose and quantify these absorption features particularly across broad spectral ranges, are still under investigation. We present INDRA (Ice-fitting with NNLS-based Decomposition and Retrieval Algorithm), a fully Python-based tool that performs continuum and silicate removal, global ice fitting using Weighted Non-Negative Least Squares (NNLS), and estimates column densities and statistical significance. We apply INDRA to NGC 1333 IRAS 2A, a target from the JWST Observations of Young protoStars (JOYS+) program previously studied using local fitting. We derive optical depths via polynomial continuum subtraction and remove silicate absorption using a synthetic model, isolating ice features for global MIRI fitting. Our results are consistent with previous local fits, confirming simple species and COMs, and expand the inventory by identifying additional absorption features from CO2 and NH4+. We also propose the presence of organic refractories contributing up to 9.6% in the spectral region of 5-8 microns among the various ice components, whose inclusion significantly improves the global spectral fitting. These broad absorption features, extending across 5.5-11 microns, are likely produced by large, complex molecules containing carbonyl (C=O), hydroxyl (O-H), amine (N-H), and C-H bending modes. Our expanded inventory, now incorporating these organic residues, offers new insights into the chemical evolution of ices in star-forming regions and highlights the importance of global spectral fitting in constraining ice compositions.

astro-ph.GA↗

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

ALMAGAL I. The ALMA evolutionary study of high-mass protocluster formation in the Galaxy. Presentation of the survey and early results

Fundamental questions about the physics responsible for fragmenting molecular parsec-scale clumps into cores of ~1000 au are still open, that only a statistically significant investigation with ALMA is able to address: what are the dominant agents that determine the core demographics, mass, and spatial distribution as a function of the physical properties of the hosting clumps, their evolutionary stage and the different Galactic environments in which they reside? To what extent extent is fragmentation driven by clumps dynamics or mass transport in filaments? With ALMAGAL we observed the 1.38 mm continuum and lines toward more than 1000 dense clumps in our Galaxy, with M>500M_sun, surface density > 0.1 g/cm2 and d<7.5 kpc. The ACA and two 12-m array setups were used to deliver a minimum resolution of ~1000 au over the entire sample distance range. The sample covers all evolutionary stages from infrared dark clouds (IRDCs) to HII regions from the tip of the Galactic bar to the outskirts of the Galaxy. The spectral setup includes several molecular lines to trace the multiscale physics and dynamics of gas, notably CH3CN, H2CO, SiO, CH3OH, DCN, HC3N, SO etc. We present an initial overview of the observations and the early science product and results, with a first characterization of the morphological properties of the continuum emission. We use "perimeter-versus-area" and convex hull-versus-area metrics to classify the different morphologies. More extended and morphologically complex shapes are found toward clumps that are relatively more evolved and have higher surface densities.

astro-ph.GA↗

arXiv2025

ALMAGAL II. The ALMA evolutionary study of high-mass protocluster formation in the Galaxy. ALMA data processing and pipeline

The ALMAGAL Large Program has observed 1017 high-mass star-forming regions distributed throughout the Galaxy, sampling different evolutionary stages and environmental conditions. In this work, we present the acquisition and processing of the ALMAGAL data. The main goal is to set up a robust pipeline that generates science-ready products, with a good and uniform quality across the whole sample. ALMAGAL observations were performed with the Atacama Large Millimeter/submillimeter Array (ALMA). Each field was observed in three different telescope arrays, being sensitive to spatial scales ranging from 1000 au up to 0.1 pc. The spectral setup allows sensitive imaging of the continuum emission at 219 GHz, and it covers multiple molecular spectral lines observed in four different spectral windows that span about 4 GHz in frequency coverage. We have designed a Python-based processing workflow to calibrate and image these observational data. This ALMAGAL pipeline includes an improved continuum determination, suited for line-rich sources; an automatic self-calibration process that improves the dynamical range of the final images; and the combination of data from different telescope arrays to produce science-ready, fully combined images. The fully combined products have spatial resolutions in the range 800-2000 au, and mass sensitivities in the range 0.02-0.07 Mo. We also present a first analysis of the spectral line information included in the ALMAGAL setup, and its potential for future scientific studies. As an example, specific spectral lines at 1000 au scales resolve the presence of multiple outflows in clusters and will help us to search for disk candidates around massive protostars. Moreover, the broad frequency bands provide information on the chemical richness of the different cluster members, which can be used to study the chemical evolution during the formation process of star clusters.

astro-ph.GA↗

arXiv2025

ALMAGAL III. Compact source catalog: Fragmentation statistics and physical evolution of the core population

The mechanisms behind the fragmentation of high-mass dense clumps into compact star-forming cores are fundamental topics in current astrophysical research. The ALMAGAL survey provides the opportunity to study this process at an unprecedented level of detail and statistical significance, featuring high-angular resolution $1.38$ mm ALMA observations of $1013$ massive dense clumps at various Galactic locations. These clumps cover a wide range of distances, masses, surface densities, and evolutionary stages. Here, we present the catalog of compact sources obtained with the CuTEx algorithm from continuum images of the full ALMAGAL clump sample combining ACA-$7$m and $12$m ALMA arrays, reaching a uniform high median spatial resolution of $\sim1400$ au. We discuss the fragmentation properties and the estimated physical parameters of the core population. The ALMAGAL compact source catalog includes $6348$ cores detected in $844$ clumps ($83\%$ of the total), with a number of cores per clump between $1$ and $49$ (median of $5$). The estimated core diameters are mostly within $\sim800-3000$ au (median of $1700$ au). We obtained core masses from $0.002$ to $345\,\mathrm{M_{\odot}}$. We evaluated the variation in the core mass function (CMF) with evolution as traced by the clump $L/M$, finding a clear, robust shift and change in slope among CMFs within subsamples at different stages. This finding suggests that the CMF shape is not constant throughout the star formation process, but rather it builds (and flattens) with evolution, with higher core masses reached at later stages. We found that all cores within a clump grow in mass on average with evolution, and the number of cores increases with the core masses. Our results favor a clump-fed scenario for high-mass star formation, in which cores form as low-mass seeds, and then gain mass while further fragmentation occurs in the clump.

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arXiv2024

ALMA detections of circumstellar disks in the giant Hii region M17. Probing the intermediate- to high-mass pre-main-sequence population

Our current understanding is that intermediate- to high-mass stars form in a way similar to low-mass stars, that is, through disk accretion. However, the physical conditions that play a role in disk formation, evolution, and the possibility of (sub)stellar companion formation, are significantly different. We search for the mm counterparts of four intermediate- to high-mass (4-10 Solar mass) young stellar objects (YSOs) in the giant Hii region M17 at a distance of 1.7 kpc. These objects expose their photospheric spectrum such that their location on the pre-main-sequence (PMS) is well established. They have a circumstellar disk that is likely remnant of the formation process. With ALMA we have detected, for the first time, these four YSOs in M17, in Band 6 and 7, as well as four other serendipitous objects. Besides the flux measurements, the source size and spectral index provide important constraints on the physical mechanism(s) producing the observed emission. We apply different models to estimate the dust and gas mass contained in the disks. All our detections are spatially unresolved, constraining the source size to <120 au, and have a spectral index in the range 0.5-2.7. The derived (upper limits on the) disk dust masses are on the order of a few Earth masses and estimations of the upper limits on the gas mass vary between $10^{-5}$ and $10^{-3}$ Solar mass. In two objects (B331 and B268) free-free emission indicates the presence of ionized material around the star. The four serendipitous detections are likely (low-mass) YSOs. We compare the derived disk masses of our M17 targets to those obtained for YSOs in low-mass star-forming regions (SFRs) and Herbig stars, as a function of stellar mass, age, luminosity, and outer disk radius. The M17 sample, though small, is both the most massive and the youngest sample, yet has the lowest mean disk mass.

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arXiv2024

Dynamical Accretion Flows -- ALMAGAL: Flows along filamentary structures in high-mass star-forming clusters

We use data from the ALMA Evolutionary Study of High Mass Protocluster Formation in the Galaxy (ALMAGAL) survey to study 100 ALMAGAL regions at $\sim$ 1 arsecond resolution located between $\sim$ 2 and 6 kpc distance. Using ALMAGAL $\sim$ 1.3mm line and continuum data we estimate flow rates onto individual cores. We focus specifically on flow rates along filamentary structures associated with these cores. Our primary analysis is centered around position velocity cuts in H$_2$CO (3$_{0,3}$ - 2$_{0,2}$) which allow us to measure the velocity fields, surrounding these cores. Combining this work with column density estimates we derive the flow rates along the extended filamentary structures associated with cores in these regions. We select a sample of 100 ALMAGAL regions covering four evolutionary stages from quiescent to protostellar, Young Stellar Objects (YSOs), and HII regions (25 each). Using dendrogram and line analysis, we identify a final sample of 182 cores in 87 regions. In this paper, we present 728 flow rates for our sample (4 per core), analysed in the context of evolutionary stage, distance from the core, and core mass. On average, for the whole sample, we derive flow rates on the order of $\sim$10$^{-4}$ M$_{sun}$yr$^{-1}$ with estimated uncertainties of $\pm$50%. We see increasing differences in the values among evolutionary stages, most notably between the less evolved (quiescent/protostellar) and more evolved (YSO/HII region) sources. We also see an increasing trend as we move further away from the centre of these cores. We also find a clear relationship between the flow rates and core masses $\sim$M$^{2/3}$ which is in line with the result expected from the tidal-lobe accretion mechanism. Overall, we see increasing trends in the relationships between the flow rate and the three investigated parameters; evolutionary stage, distance from the core, and core mass.

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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.

astro-ph.GA↗

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 $μ$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 $μ$m in IRAS 2A and IRAS 23385, originating from simple molecules, COMs, and negative ions. The strongest feature in this range (7.7 $μ$m) is dominated by CH4 and has contributions of SO2 and OCN-. Our results indicate that the 7.2 and 7.4 $μ$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.

astro-ph.SR↗

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$_2~ν_3$ 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 $ν_3$ 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 $ν_3$ lines. This is in good agreement with the rotational temperature derived from pure rotational lines in the vibrational ground state (i.e., $ν=0$) with ALMA ($104\pm5$ K). However, the emission of the $ν_3$ 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 $ν=0$ state. This difference can be explained by a vibrational temperature that is $\sim100$ K higher than the derived rotational temperature of the $ν=0$ state. The brightness temperature derived from the continuum around the $ν_3$ band of SO$_2$ is $\sim180$ K, which confirms that the $ν_3=1$ level is not collisionally populated but rather infrared pumped by scattered radiation. This is also consistent with the non-detection of the $ν_2$ 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.

astro-ph.SR↗