Rubén Fedriani

Massive stars play a critical role in the evolution of galaxies, but their formation remains poorly understood. One challenge is accurate measurement of the physical properties of massive protostars, such as current stellar mass, envelope mass, outflow cavity properties, and system orientation. Spectral energy distribution (SED) fitting is widely used to test models against observations. The far-infrared SED traces cold dust in envelopes, while the near- and mid-infrared (MIR) probes emission from outflow cavities and/or the inner envelope. However, SED fitting has degeneracies limiting its ability to yield accurate measurements of protostellar properties. Here, we develop image profile (IMPRO) fitting as a method to improve the characterization of protostars. We use brightness distributions from multiwavelength MIR images of massive protostars taken by SOFIA/FORCAST as part of the SOFIA Massive Star Formation (SOMA) survey to constrain protostellar properties by comparing them to a grid of radiative transfer models. We develop a fitting pipeline to extract information along the outflow axis, which is then combined with the SED fitting to yield improved constraints on protostellar properties. We apply the IMPRO fitting method to the nearby massive protostar Cepheus A, finding that its properties become more tightly constrained compared to SED fitting, especially in the inclination of the source. However, for the more distant G35.20–0.74N, we find that the spatial resolution of SOFIA/FORCAST limits the utility of this combined fitting pipeline. However, higher-resolution MIR observations, e.g., with JWST, are expected to greatly expand the applicability of this fitting technique to protostars across the Galaxy.

Context. The physical conditions within the innermost few tens of astronomical units of high-mass protostars ( M _* > 8 M _⊙ ) remain largely unexplored. At these scales, ionised emission can trace photoionised gas, accretion disks, or the base of protostellar jets. Aims. We search for ionised emission in the form of radio recombination lines (RRLs) in high-mass star-forming regions. Methods. We used archival data from the Atacama Millimeter/submillimeter Array (ALMA) interferometer in band 6 (∼1.3 mm) with a resolution of θ _beam ∼ 53 mas × 42 mas to examine the high-mass protostar IRAS 18162−2048, the driving source of the Herbig-Haro (HH) objects HH80-81. Results. We detect, for the first time in this protostar, the thermal emission of the RRL H30 α (rest frequency = 231.90093 GHz). The ionised emission is spatially unresolved in our observations, but we estimate an emitting region of ≲50 au at the source distance of 1.4 kpc. The H30 α line profile is broad and spectrally resolved with a local standard of rest velocity of ∼ − 14 km s ⁻¹ (i.e. ∼ − 26 km s ⁻¹ blueshifted with respect to the systemic velocity of the cloud) and a full width at half maximum of ∼82 km s ⁻¹ . These observations suggest that the H30 α line is tracing outflowing blueshifted material in the well-known radio jet from this object. This detection opens the possibility of detailed studies of the kinematics and physical properties of ionised jets.

We present results from Karl G. Jansky Very Large Array radio-continuum observations of 12 intermediate-mass (IM) protostars, as part of the SOFIA Massive Star Formation Survey. Using these observations, we studied their morphology, multiplicity, and radio spectral energy distributions (SEDs). Across our target regions, we resolve multiple compact sources and report eight new detections, four of which are entirely new and four that have counterparts at other wavelengths, but are detected here for the first time at radio frequencies. Based on radio morphologies and spectral indices, we assess the nature of the detected sources, highlighting seven that display jetlike structures and spectral indices consistent with ionized jets. Combining our results with the SOMA Radio I and II results, we expand the overall sample to 29 protostars, covering a bolometric luminosity range from L _bol ∼ 10 ² to 10 ⁶ L _⊙ . These sources help define a potential evolutionary sequence in the radio versus bolometric luminosity diagram. IM protostars have radio luminosities that are lower than expected from a simple power-law extrapolation from low-mass protostars. However, this result is consistent with theoretical expectations from protostellar evolution models, which show low levels of photoionization and reduced shock ionization emission due to expanded stellar radii during this phase. Overall our expanded SOMA Radio sample provides new constraints on theoretical models of massive protostellar evolution, especially the connection to ionized gas structures.

We present an Atacama Large Millimeter/submillimeter Array 1.3 mm dust continuum study of the dense core mass function (CMF) in Sh2-284, a low-metallicity outer Galaxy star-forming complex with Z ∼ 1/3–1/2 Z _⊙ . The observations cover six far-infrared bright subregions at ∼0 . ″ 65 (3000 au) resolution. We identify a total of 91 candidate dense cores and define a robust catalog of 68 cores with Gaussian fitting. The high-mass CMF above 2.5 M _⊙ is well described by a Salpeter-like slope, with a fiducial forward-modeled value of α = 1.2 2 − 0.22 + 0.24 for d N / d log M ∝ M − α . Together with existing constraints on the initial mass function (IMF) of Sh2-284, the Salpeter-like CMF is consistent with a resemblance between the CMF and IMF shapes in the outer Galaxy environments, suggesting that moderately low metallicity alone does not strongly reshape the high-mass CMF/IMF slope.

We present data from the ALMA Central Molecular Zone Exploration Survey (ACES) Large Program, which provides broad spectral-line and 3 mm continuum coverage of the Central Molecular Zone (CMZ) at a spatial resolution of 0.1 pc. The survey delivers homogeneous, wide-field mosaics that enable direct comparisons of the physical and chemical conditions across diverse environments in the Galactic centre. In this data release paper, we present the CS($2-1$), SO(2$_{3}-1_{2}$), CH$_3$CHO($5_{1,4}-4_{1,3}$), HC$_3$N($11-10$), and H40$\alpha$ lines observed simultaneously within two broad spectral windows. These lines reveal pronounced spatial and chemical variations across the CMZ, tracing distinct components of molecular gas, shock-affected regions, and ionized structures. The high angular resolution and multi-line capability of the ACES data set make it a powerful resource for future studies of gas dynamics, star formation activity, and the physical connection between the CMZ and Sgr A*.