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Abstract The chemical evolution in star forming regions is driven by the interplay between gas and ice mantles. Identifying the ice compositions at the early stage of star formation thus provides constraints on the chemical processes inaccessible from gas-phase characterizations. As part of the CORINOS program, spectra from the James Webb Space Telescope (JWST) Mid-Infrared Instruments Medium Resolution Spectroscopy were taken toward four Class 0 protostars: IRAS 15398-3359, Ser-emb7, L483, and B335. The spectra were processed with simultaneous fitting of a continuum and silicate absorption to produce optical depth mid-infrared spectra of the ices at 5–28μm (360–2000 cm⁻¹) toward these four sources. Simple molecules such as water (H₂O), carbon dioxide (CO₂), methanol (CH₃OH), formic acid/formate (HCOOH/HCOO⁻), ammonia/ammonium (NH₃/NH₄⁺), and formaldehyde (H₂CO) are the most abundant features in these ices, while complex organic molecules (COMs) represent a smaller contribution. Likely COMs include hydroxylamine (NH₂OH), methylamine (CH₃NH₂), and ethanol (CH₃CH₂OH). Absorption features belonging to functional groups such as –CH₃and –OH suggest that additional COMs are present, but these cannot be unambiguously assigned due to overlapping bands. Formation pathways toward these COMs utilizing radical–radical combination reactions based on laboratory simulation experiments is presented. By extension, COMs predicted by these reactions, but absent from the spectra, are discussed. The results provide insight into the chemical environment of these ices and also highlight the critical need for caution and sufficient evidence in order to confidently identify COMs in ice. 

Abstract As part of the ALMA Large Program “Early Planet Formation in Embedded Disks,”¹²CO (2–1) was observed towards 19 nearby low-mass protostars. Of these objects, 15 sources are found to show molecular outflow emission. Based on their morphological and kinematical structures, the CO outflows are classified into three types: a wind-driven shell, where ambient material is swept up by a wide-angle wind from the star, a bow shock, and a slow disk wind, which is a conical or parabolic flow with onion-like velocity structure. We categorize 11 outflows as a slow disk wind, 7 as a wind-driven shell, and 1 as a bow shock. Four of these outflows were found to show signs of both slow disk wind and wind-driven shell characteristics. Five objects show misalignment between the red- and blueshifted outflows. Seven objects show significant misalignment between the outflow axis (either or both of the red- and blueshifted outflows) and the minor axis of the dust continuum emission around the protostar. For the objects showing wind-driven shell emission, we compare simple parametrized models with the observations to derive physical properties of the observed shells, such as their dynamical ages. This shows evidence of a time variability in the outflows, such as changes in their direction. In some objects, large differences are seen between the properties of the red- and blueshifted outflows, possibly indicating differences in the properties of the ambient medium with which the outflow interacts. 

Context.Recent studies indicate that the formation of planets in protoplanetary disks begins early in the embedded Class 0/I phases of protostellar evolution. The physical and chemical makeup of the embedded phase can provide valuable insights into the process of star and planet formation. Aims.This study aims to provide a thorough overview of the various morphologies for molecular emissions observed on disk scales (≲100 au) toward nearby embedded sources. Methods.We present high angular resolution (0_⋅^′′1, ~ 15 au) molecular line emissions for¹²CO,¹³CO, C¹⁸O, SO, SiO, DCN, CH₃OH, H₂CO, andc–C₃H₂toward 19 nearby protostellar sources in the context of the Atacama Large Millimeter/submillimeter Array (ALMA) Large Program “Early Planet Formation in Embedded Disks (eDisk).” Results.Emissions in¹²CO are seen toward all sources and primarily trace outflowing materials. A few sources also show high-velocity jets in SiO emission and high-velocity channel maps of¹²CO. The¹³CO and C¹⁸O emissions are well-known tracers of high-density regions and trace the inner envelope and disk regions with clear signs of rotation seen at continuum scales. The large-scale emissions of¹³CO also delineate the outflow cavity walls where the outflowing and infalling materials interact with each other, and exposure to UV radiation leads to the formation of hydrocarbons such asc–C₃H₂. Both DCN and CH₃OH, when detected, show compact emissions from the inner envelope and disk regions that peak at the position of the protostar. The CH₃OH emissions are contained within the region of DCN emissions, which suggests that CH₃OH traces the hot core regions. Likewise, a few sources, also display emissions in CH₃OH toward the outflow. Both SO and H₂CO show complex morphology among the sources, suggesting that they are formed through multiple processes in protostellar systems. 

Abstract Sulfur dioxide (SO₂) ice has been tentatively detected in protostellar envelopes, but its reliability as a solid-state sulfur reservoir remains unclear. We present new measurements of SO₂ice from 6.8–8.5μm toward four Class 0 protostars observed with JWST’s Mid-Infrared (MIRI) Medium Resolution Spectrometer, as part of the COMs ORigin Investigated by the Next-generation Observatory in Space (CORINOS) program. The sample spans a luminosity range from 1L_⊙(B335, IRAS 15398–3359) to 10L_⊙(L483, Ser-emb 7). To assess continuum placement uncertainty in absorption spectra, we apply randomized polynomial fits over the restricted region. We fit laboratory spectra from the Leiden Ice Database for Astrochemistry using the open-source Python library Omnifit. We detect the 7.7μm CH₄band in all sources and find its column density robust to baseline choice, providing a reference for evaluating the weaker SO₂feature on its blue shoulder and quantifying baseline-related uncertainty. Three SO₂laboratory ices were tested: pure SO₂ice yields 0.3%–1.2% of volatile sulfur may be locked in SO₂ice (lower and upper limits); CH₃OH:SO₂ice gives 0.02%–0.18%, but with lower quality fitting. The best-fitting H₂O:SO₂ice yields 0.2%–0.9%, which we consider the most realistic. These ranges define plausible bounds on SO₂ice abundances in our sample. We find evidence for SO₂in Ser-emb 7, L483, and IRAS 15398–3359, but emphasize the noisy spectrum of B335 prevents a definitive detection. Comparing SO₂ice abundances across the different environments, we assess how conditions influence the role of SO₂as a potential sulfur reservoir and implications for the longstanding “missing sulfur” problem. 

Abstract We present James Webb Space Telescope (JWST) Near Infrared Camera observations of the massive star-forming molecular cloud Sagittarius C (Sgr C) in the Central Molecular Zone (CMZ). In conjunction with ancillary mid-IR and far-IR data, we characterize the two most massive protostars in Sgr C via spectral energy distribution (SED) fitting, estimating that they each have current masses ofm_*∼ 20M_⊙and surrounding envelope masses of ∼100M_⊙. We report a census of lower-mass protostars in Sgr C via a search for infrared counterparts to millimeter continuum dust cores found with the Atacama Large Millimeter/submillimeter Array (ALMA). We identify 88 molecular hydrogen outflow knot candidates originating from outflows from protostars in Sgr C, the first such unambiguous detections in the infrared in the CMZ. About a quarter of these are associated with flows from the two massive protostars in Sgr C; these extend for over 1 pc and are associated with outflows detected in ALMA SiO line data. An additional ∼40 features likely trace shocks in outflows powered by lower-mass protostars throughout the cloud. We report the discovery of a new star-forming region hosting two prominent bow shocks and several other line-emitting features driven by at least two protostars. We infer that one of these is forming a high-mass star given an SED-derived mass ofm_*∼ 9M_⊙and associated massive (∼90M_⊙) millimeter core and water maser. Finally, we identify a population of miscellaneous molecular hydrogen objects that do not appear to be associated with protostellar outflows. 

Aims.Edge-on discs offer a unique opportunity to probe radial and vertical dust and gas distributions in the protoplanetary phase. This study aims to investigate the distribution of micron-sized dust particles in the Flying Saucer in Rho Ophiuchi by leveraging the unique observational conditions of a bright infrared background that enables the edge-on disc to be seen in both silhouette and scattered light at specific wavelengths. Methods.We used NIRSpec IFU observations from the JWST Edge-on Disc Ice program (JEDIce) of the Flying Saucer serendipitously observed against a Polycyclic Aromatic Hydrocarbons-emitting background to constrain the dust distribution and grain sizes via radiative transfer modelling. Results.The observation of the Flying Saucer in silhouette at 3.29 μm reveals that the midplane radial extent of small dust grains is ∼235 au, i.e. larger than the large-grain disc extent previously determined to be 190 au from millimetre data. The scattered light observed in emission probes micron-sized icy grains at large vertical distances above the midplane. The vertical extent of the disc silhouette is similar at visible, near-IR, and mid-IR wavelengths, corroborating the conclusion that dust settling is inefficient for grains as large as tens of microns, both vertically and radially. 

Context. Evidence that the chemical characteristics around low- and high-mass protostars are similar has been found: notably, a variety of carbon-chain species and complex organic molecules (COMs) form around both types. On the other hand, the chemical compositions around intermediate-mass (IM) protostars (2M_⊙<m_*< 8M_⊙) have not been studied with large samples. In particular, it is unclear the extent to which carbon-chain species form around them. Aims. We aim to obtain the chemical compositions of a sample of IM protostars, focusing particularly on carbon-chain species. We also aim to derive the rotational temperatures of HC₅N to confirm whether carbon-chain species are formed in the warm gas around these stars. Methods. We conducted Q-band (31.5–50 GHz) line survey observations toward 11 mainly IM protostars with the Yebes 40 m radio telescope. The target protostars were selected from a subsample of the source list of the SOFIA Massive Star Formation project. Assuming local thermodynamic equilibrium, we derived the column densities of the detected molecules and the rotational temperatures of HC₅N and CH₃OH. Results. Nine carbon-chain species (HC₃N, HC₅N, C₃H, C₄Hlinear-H₂CCC,cyclic-C₃H₂, CCS, C₃S, and CH₃CCH), three COMs (CH₃OH, CH₃CHO, and CH₃CN), H₂CCO, HNCO, and four simple sulfur-bearing species (¹³CS, C³⁴S, HCS⁺, and H₂CS) are detected. The rotational temperatures of HC₅N are derived to be ~20–30 K in three IM protostars (Cepheus E, HH288, and IRAS 20293+3952). The rotational temperatures of CH₃OH are derived in five IM sources and found to be similar to those of HC₅N. Conclusions. The rotational temperatures of HC₅N around the three IM protostars are very similar to those around low- and high-mass protostars. These results indicate that carbon-chain molecules are formed in lukewarm gas (~20–30 K) around IM protostars via the warm carbon-chain chemistry process. Thus, carbon-chain formation occurs ubiquitously in the warm gas around protostars across a wide range of stellar masses. Carbon-chain molecules and COMs coexist around most of the target IM protostars, which is similar to the situation for low- and high-mass protostars. In summary, the chemical characteristics around protostars are the same in the low-, intermediate- and high-mass regimes. 

Abstract We present ∼8–40μm SOFIA-FORCAST images of seven regions of “clustered” star formation as part of the SOFIA Massive Star Formation Survey. We identify a total of 34 protostar candidates and build their spectral energy distributions (SEDs). We fit these SEDs with a grid of radiative transfer models based on the turbulent core accretion (TCA) theory to derive key protostellar properties, including initial core mass,M_c, clump environment mass surface density, Σ_cl, and current protostellar mass,m_*. We also carry out empirical graybody (GB) estimation of Σ_cl, which allows a case of restricted SED fitting within the TCA model grid. We also release version 2.0 of the open-source Python packagesedcreator, which is designed to automate the aperture photometry and SED building and fitting process for sources in clustered environments, where flux contamination from close neighbors typically complicates the process. Using these updated methods, SED fitting yields values ofM_c∼ 30–200M_⊙, Σ_cl,SED∼ 0.1–3 g cm⁻², andm_*∼ 4–50M_⊙. The GB fitting yields smaller values of Σ_cl,GB≲ 1 g cm⁻². From these results, we do not find evidence for a critical Σ_clneeded to form massive (≳8M_⊙) stars. However, we do find tentative evidence for a dearth of the most massive (m_*≳ 30M_⊙) protostars in the clustered regions, suggesting a potential impact of environment on the stellar initial mass function. 

Abstract We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the binary Class 0 protostellar system BHR 71 IRS1 and IRS2 as part of the Early Planet Formation in Embedded Disks (eDisk) ALMA Large Program. We describe the¹²CO (J= 2–1),¹³CO (J= 2–1), C¹⁸O (J= 2–1), H₂CO (J= 3_2,1–2_2,0), and SiO (J= 5–4) molecular lines along with the 1.3 mm continuum at high spatial resolution (∼0.″08 or ∼5 au). Dust continuum emission is detected toward BHR 71 IRS1 and IRS2, with a central compact component and extended continuum emission. The compact components are smooth and show no sign of substructures such as spirals, rings, or gaps. However, there is a brightness asymmetry along the minor axis of the presumed disk in IRS1, possibly indicative of an inclined geometrically and optically thick disk-like component. Using a position–velocity diagram analysis of the C¹⁸O line, clear Keplerian motions were not detected toward either source. If Keplerian rotationally supported disks are present, they are likely deeply embedded in their envelope. However, we can set upper limits of the central protostellar mass of 0.46M_⊙and 0.26M_⊙for BHR 71 IRS1 and BHR 71 IRS2, respectively. Outflows traced by¹²CO and SiO are detected in both sources. The outflows can be divided into two components, a wide-angle outflow and a jet. In IRS1, the jet exhibits a double helical structure, reflecting the removal of angular momentum from the system. In IRS2, the jet is very collimated and shows a chain of knots, suggesting episodic accretion events. 

Abstract We report high-resolution 1.3 mm continuum and molecular line observations of the massive protostar G28.20-0.05 with Atacama Large Millimeter/submillimeter Array. The continuum image reveals a ring-like structure with 2000 au radius, similar to morphology seen in archival 1.3 cm Very Large Array observations. Based on its spectral index and associated H30αemission, this structure mainly traces ionized gas. However, there is evidence for ∼30M_⊙of dusty gas near the main millimeter continuum peak on one side of the ring, as well as in adjacent regions within 3000 au. A virial analysis on scales of ∼2000 au from hot core line emission yields a dynamical mass of ∼80M_⊙. A strong velocity gradient in the H30αemission is evidence for a rotating, ionized disk wind, which drives a larger-scale molecular outflow. An infrared spectral energy distribution (SED) analysis indicates a current protostellar mass ofm_*∼ 40M_⊙forming from a core with initial massM_c∼ 300M_⊙in a clump with mass surface density of Σ_cl∼ 0.8 g cm⁻². Thus the SED and other properties of the system can be understood in the context of core accretion models. A structure-finding analysis on the larger-scale continuum image indicates G28.20-0.05 is forming in a relatively isolated environment, with no other concentrated sources, i.e., protostellar cores, above ∼1M_⊙found from ∼0.1 to 0.4 pc around the source. This implies that a massive star can form in relative isolation, and the dearth of other protostellar companions within the ∼1 pc environs is a strong constraint on massive star formation theories that predict the presence of a surrounding protocluster.