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1. PRODIGE – envelope to disk with NOEMA: III. The origin of complex organic molecule emission in SVS13A

   https://doi.org/10.1051/0004-6361/202449417  

   Hsieh, T-H; Pineda, J E; Segura-Cox, D M; Caselli, P; Valdivia-Mena, M T; Gieser, C; Maureira, M J; Lopez-Sepulcre, A; Bouscasse, L; Neri, R; et al (June 2024, Astronomy & Astrophysics)

   Context.Complex organic molecules (COMs) have been found toward low-mass protostars, but the origins of the COM emission are still unclear. It can be associated with, for example, hot corinos, outflows, and/or accretion shock and disk atmospheres. Aims.We aim to disentangle the origin of the COM emission toward the chemically rich protobinary system SVS13A using six O-bearing COMs. Methods.We conducted NOrthern Extended Millimeter Array observations toward SVS13A as part of the PROtostars & DIsks: Global Evolution (PRODIGE) program. Our previous DCN observations reveal a possible infalling streamer, which may affect the chemistry of the central protobinary by inducing accretion outbursts and/or shocked gas. We further analyzed six O-bearing COMs: CH₃OH, aGg’- (CH₂OH)₂, C₂H₅OH, CH₂(OH)CHO, CH₃CHO, and CH₃OCHO. Although the COM emission is not spatially resolved, we constrained the source sizes to ≲0.3–0.4 arcsec (90–120 au) by conducting uv-domain Gaussian fitting. Interestingly, the high-spectral-resolution data reveal complex line profiles with multiple peaks; although the line emission is likely dominated by the secondary, VLA4A, atV_LSR= 7.36 km s⁻¹, the numbers of peaks (~2–5), the velocities, and the linewidths of these six O-bearing COMs are different. The local thermodynamic equilibrium (LTE) fitting unveils differences in excitation temperatures and emitting areas among these COMs. We further conducted multiple-velocity-component LTE fitting to decompose the line emission into different kinematic components. As a result, the emission of these COMs is decomposed into up to six velocity components from the LTE modeling. The physical conditions (temperature, column density, and source size) of these components from each COM are obtained, and Markov chain Monte Carlo sampling was performed to test the fitting results. Results.We find a variety in excitation temperatures (100–500 K) and source sizes (D~ 10–70 au) from these kinematic components from different COMs. The emission of each COM can trace several components, and different COMs most likely trace different regions. Conclusions.Given this complex structure, we suggest that the central region is inhomogeneous and unlikely to be heated by only protostellar radiation. We conclude that accretion shocks induced by the large-scale infalling streamer likely exist and contribute to the complexity of the COM emission. This underlines the importance of high-spectral-resolution data when analyzing COM emission in protostars and deriving relative COM abundances. 

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2. Digging into the Interior of Hot Cores with ALMA (DIHCA). II. Exploring the Inner Binary (Multiple) System Embedded in G335 MM1 ALMA1

   https://doi.org/10.3847/1538-4357/ac5bd8  

   Olguin, Fernando A.; Sanhueza, Patricio; Ginsburg, Adam; Chen, Huei-Ru Vivien; Zhang, Qizhou; Li, Shanghuo; Lu, Xing; Sakai, Takeshi (April 2022, The Astrophysical Journal)

   Abstract We observed the high-mass protostellar core G335.579–0.272 ALMA1 at ∼200 au (0.″05) resolution with the Atacama Large Millimeter/submillimeter Array (ALMA) at 226 GHz (with a mass sensitivity of 5 σ = 0.2 M ⊙ at 10 K). We discovered that at least a binary system is forming inside this region, with an additional nearby bow-like structure (≲1000 au) that could add an additional member to the stellar system. These three sources are located at the center of the gravitational potential well of the ALMA1 region and the larger MM1 cluster. The emission from CH 3 OH (and many other tracers) is extended (>1000 au), revealing a common envelope toward the binary system. We use CH 2 CHCN line emission to estimate an inclination angle of the rotation axis of 26° with respect to the line of sight based on geometric assumptions and derive a kinematic mass of the primary source (protostar+disk) of 3.0 M ⊙ within a radius of 230 au. Using SiO emission, we find that the primary source drives the large-scale outflow revealed by previous observations. Precession of the binary system likely produces a change in orientation between the outflow at small scales observed here and large scales observed in previous works. The bow structure may have originated from the entrainment of matter into the envelope due to the widening or precession of the outflow, or, alternatively, an accretion streamer dominated by the gravity of the central sources. An additional third source, forming due to instabilities in the streamer, cannot be ruled out as a temperature gradient is needed to produce the observed absorption spectra. 

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3. PRODIGE – envelope to disk with NOEMA: I. A 3000 au streamer feeding a Class I protostar

   https://doi.org/10.1051/0004-6361/202243310  

   Valdivia-Mena, M. T.; Pineda, J. E.; Segura-Cox, D. M.; Caselli, P.; Neri, R.; López-Sepulcre, A.; Cunningham, N.; Bouscasse, L.; Semenov, D.; Henning, Th.; et al (November 2022, Astronomy & Astrophysics)

   Context. In the past few years, there has been a rise in the detection of streamers, asymmetric flows of material directed toward the protostellar disk with material from outside a star’s natal core. It is unclear how they affect the process of mass accretion, in particular beyond the Class 0 phase. Aims. We investigate the gas kinematics around Per-emb-50, a Class I source in the crowded star-forming region NGC 1333. Our goal is to study how the mass infall proceeds from envelope to disk scales in this source. Methods. We use new NOEMA 1.3 mm observations, including C 18 O, H 2 CO, and SO, in the context of the PRODIGE MPG – IRAM program, to probe the core and envelope structures toward Per-emb-50. Results. We discover a streamer delivering material toward Per-emb-50 in H 2 CO and C 18 O emission. The streamer’s emission can be well described by the analytic solutions for an infalling parcel of gas along a streamline with conserved angular momentum, both in the image plane and along the line-of-sight velocities. The streamer has a mean infall rate of 1.3 × 10 −6 M ⊙ yr− 1 , five to ten times higher than the current accretion rate of the protostar. SO and SO 2 emission reveal asymmetric infall motions in the inner envelope, additional to the streamer around Per-emb-50. Furthermore, the presence of SO 2 could mark the impact zone of the infalling material. Conclusions. The streamer delivers sufficient mass to sustain the protostellar accretion rate and might produce an accretion burst, which would explain the protostar’s high luminosity with respect to other Class I sources. Our results highlight the importance of late infall for protostellar evolution: streamers might provide a significant amount of mass for stellar accretion after the Class 0 phase. 

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4. Physical conditions in the warped accretion disk of a massive star: 349 GHz ALMA observations of G023.01−00.41

   https://doi.org/10.1051/0004-6361/202040000  

   Sanna, A.; Giannetti, A.; Bonfand, M.; Moscadelli, L.; Kuiper, R.; Brand, J.; Cesaroni, R.; Caratti o Garatti, A.; Pillai, T.; Menten, K. M. (November 2021, Astronomy & Astrophysics)

   Young massive stars warm up the large amount of gas and dust that condenses in their vicinity, exciting a forest of lines from different molecular species. Their line brightness is a diagnostic tool of the gas’s physical conditions locally, which we use to set constraints on the environment where massive stars form. We made use of the Atacama Large Millimeter/submillimeter Array at frequencies near 349 GHz, with an angular resolution of 0′′.1, to observe the methyl cyanide (CH 3 CN) emission which arises from the accretion disk of a young massive star. We sample the disk midplane with twelve distinct beams, where we get an independent measure of the gas’s (and dust’s) physical conditions. The accretion disk extends above the midplane, showing a double-armed spiral morphology projected onto the plane of the sky, which we sample with ten additional beams: Along these apparent spiral features, gas undergoes velocity gradients of about 1 km s −1 per 2000 au. The gas temperature ( T ) rises symmetrically along each side of the disk, from about 98 K at 3000 au to 289 K at 250 au, following a power law with radius R −0.43 . The CH 3 CN column density ( N ) increases from 9.2 × 10 15 cm −2 to 8.7 × 10 17 cm −2 at the same radii, following a power law with radius R −1.8 . In the framework of a circular gaseous disk observed approximately edge-on, we infer an H 2 volume density in excess of 4.8 ×10 9 cm −3 at a distance of 250 au from the star. We study the disk stability against fragmentation following the methodology by Kratter et al. (2010, ApJ, 708, 1585), which is appropriate under rapid accretion, and we show that the disk is marginally prone to fragmentation along its whole extent. 

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5. First Results from ALPPS: A Sub-Alfvénic Streamer in SVS 13A

   https://doi.org/10.3847/2041-8213/ae0c04  

   Cortés, P C; Pineda, J E; Hsieh, T-H; Tobin, J J; Saha, P; Girart, J M; Le_Gouellec, V_J M; Stephens, I W; Looney, L W; Koumpia, E; et al (October 2025, The Astrophysical Journal Letters)

   Abstract We present the first results from the Atacama Large Millimeter/submillimeter Array Perseus Polarization Survey, focusing on the magnetic field in the SVS 13A circumbinary disk. The data set includes full Stokes dust continuum observations at $\sim 0\stackrel{″}{.}3$ and 870μm, as well as molecular line emission from C¹⁷O(J = 3 → 2) at $\sim 0\stackrel{″}{.}3$ , C¹⁸O(J = 2 → 1) at $\sim 0\stackrel{″}{.}2$ , and DCN(J = 3 → 2) at $\sim 0\stackrel{″}{.}1$ angular resolution. Our observations resolve both a previously identified dust spiral and an infalling streamer, capturing their spatial and kinematic structures. The streamer is traced from scales >300 au down to the circumbinary disk. Using alignment measure (AM) maps and histograms that compare the orientations of the plane-of-sky magnetic field with local intensity and velocity gradients, we find that the AM distribution peaks at a value of 1. This AM peak strongly suggests alignment between the field and the dust total intensity emission, as well as between the field and the gas velocity, which in turn suggests grain alignment by magnetic fields. From our data, we derive a magnetic field strength,B_pos ∼ 1.1 ± 0.6 mG, and a kinetic-to-magnetic energy ratio of 0.5 ± 0.4, suggesting magnetic dominance. We also produced a map of the Alfvénic Mach number, finding ${\mathcal{M}}_{\mathrm{A}}<1$ along the streamer, consistent with sub-Alfvénic infalling motions. Therefore, the field is likely facilitating the inflow of material from the envelope onto the disk by constraining movement across the field lines. This represents the first detection of a magnetically sub-Alfvénic infalling streamer in a protostellar system. 

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