Roberto Galván-Madrid

Context . Massive stars form in the densest part of molecular clouds and strongly influence their surroundings through radiative and mechanical feedback. The effects of such feedback on dense gas structures at sub-parsec scales, however, remain to be better constrained by observations. Aims . We aim to investigate how feedback from a newly formed massive star affects the physical properties of dense cores embedded in a neighboring filamentary molecular cloud. Methods . We analyzed the ALMA Band 6 observations of the filamentary source IRAS 18530+0215 (I18530), including 1.3 mm dust continuum, molecular line emission from DCN, N ₂ D ⁺ , and ¹³ CS, as well as complementary VLA K-band continuum and NH ₃ metastable line observations. The dynamical state of the ultracompact (UC) H II region was investigated through energy and pressure estimates. Dense cores traced by the line emission were identified using the astrodendro algorithm, and their temperatures, masses, velocity dispersions, and virial parameters were derived from molecular line fitting and continuum emission. We further examined how the physical and kinematic properties of the dense cores vary under the influence of feedback from the H II region. Results . The H II region has a radius of ∼0.1 pc and exhibits an expansion velocity of ∼2.5 km s ⁻¹ , corresponding to a shell dynamical age of ∼0.06 Myr. The DCN and ¹³ CS cores are primarily distributed in the vicinity of the H II region, whereas N ₂ D ⁺ cores are preferentially found at larger distances. Overall, the temperatures and velocity dispersions of the dense cores show clear decreasing trends with increasing projected distance from the H II region. The virial parameters increase with projected distance within the inner ∼0.3 pc but decline sharply beyond this scale, while the core masses show no significant variation with distance. Strong star formation signatures are found at projected distances of ∼0.2 pc from the H II region, whereas more distant regions still host quiescent, cold dense cores at earlier evolutionary stages. Conclusions . Our results suggest that the compact H II region is currently trapped or choked within a scale of ∼0.1 pc. Its feedback extends to at least ∼0.3 pc and is unlikely to significantly disrupt the entire filamentary structure on short timescales. Within the affected region, the feedback enhances the velocity dispersions, gas temperatures, and virial parameters of the dense cores, with no evidence that it promotes the formation of more massive dense cores.

Aims. The gravoturbulent fragmentation of the interstellar medium is expected to create a hierarchical cascade of cloud structures, crossing the scales from core to disk. We aim to predict how the currently observed top-heavy core mass function (CMF) in the massive protocluster W43-MM1 evolves due to core subfragmentation. Methods. We used the getsf algorithm to extract sources in five ALMA images of W43-MM1 at 3 mm, with a spatial resolution ranging from 14 kau to 270 au. Then, we applied FAMILY , a graph-theory-based analysis tool, to create and characterize networks of nested sources in W43-MM1. We compared the hierarchical fragmentation cascade of W43-MM1 to those measured in the NGC 2264 protocluster and in synthetic images of an Orion-like protocluster simulated by magneto-hydrodynamical calculations. Results. Assuming self-similarity, we measured a small fractality index of F _3D = 1.19 ± 0.10 in W43-MM1, which means that, on average, a cloud structure fragments into only 1.19 fragments each time the physical scale decreases by a factor of two. In line with values measured above the core scale in the NGC 2264 and synthetic protoclusters, the W43-MM1 fractality index increases by about 30% at larger scales. We also estimate an imbalanced mass partition between siblings, with two-thirds of the mass of siblings at a given scale belonging to the dominant sibling. The mass transfer efficiency, computed from one physical scale to another, is high and corresponds to a core formation efficiency (CFE) from 2400 au cores to 200 au seeds of ∼16%. Conclusions. Based on the fractality and efficiency values measured in W43-MM1, the gravoturbulent model by Thomasson predicts that its fragmentation below ∼14 kau is not driven by turbulence but by gravity. Using these parameters and the measured mass partition, we demonstrate that the seed mass function, from which the initial mass function (IMF) emerges, has a high-mass end that remains top-heavy. Therefore, based on our current assumptions, core subfragmentation in W43-MM1, and perhaps more broadly in massive Galactic protoclusters, plays a minimal role in shaping the high-mass slope of the IMF.

Context . Although there has been significant progress, the physical properties and potential fragmentation of accretion disks around high-mass protostars remain poorly constrained. Aims . We characterize at high angular resolution one of the most nearby (~700 pc) high-mass accretion disk candidates, CepA HW2. Methods . Using the new long-baseline array configuration (~1700 m) of the Northern Extended Millimeter Array (NOEMA), we study CepA HW2 with a resolution of ≤0.2″ or ≤100 au at 1.3 mm in dust continuum and spectral line emission. Results . The millimeter continuum emission resolves the central disk candidate into several substructures. Conducting a Toomre Q stability analysis based on CH ₃ CN and continuum data, and a comparison to 3D radiation hydrodynamic simulations shows that the data are consistent with an almost edge-on disk whereby the observed substructures may represent fragments within the disk. The CO and SiO spectral line data confirm a second bipolar outflow (in addition to the well-known jet) emanating from the central peak position. This indicates that this central peak should host at least a binary if not even a higher-order multiple system. The usually assumed dense gas tracer CH ₃ CN also shows contributions from the outflows, which complicates further kinematic analysis of the disk. Conclusions . The high-resolution outflow-disk data of CepA reveal a multiply fragmented disk that drives several outflows. These observations reinforce the picture of high-mass star formation in which multiplicity and fragmentation can happen on the smallest spatial scales related to the inner accretion disks.

We characterize kinematic processes in the G012.80 protocluster. We primarily focused on the N_2H+$(1-0) emission to trace the dense and cold gas. Additionally, we used complementary lines such as DCN(3-2), H41α, C^18O(2-1), and SiO(5-4), as well as continuum maps. We performed a N_2H^+ hyperfine spectral line fitting to analyze multiple velocity components and extract spectral parameters. We estimated velocity gradients, column densities, and line-mass profiles for the two main filaments in G012, which we named R1 and R2. The line-mass profiles follow łambda(ω),=,5660,M_⊙,pc^-1(ω/pc)^0.30 for R1 and łambda(ω),=,6943,M_⊙,pc^-1(ω/pc)^0.20 for R2. This is much larger than profiles of typical low-mass filaments. R1 and R2 show disparate position-velocity (PV) features. R1 exhibits a transverse velocity gradient of 10.4,km,s^-1,pc^-1 and a few dense cores. This velocity gradient is interpreted with a simple rotation toy model when combined with the line-mass profile, and it corresponds to a rotational timescale of ∼,0.1,Myr. In contrast, R2 exhibits compact velocity structures (ΔV < 2,km,s^-1), likely due to collapse, as evidenced by the comparatively large number of massive cores and protostellar outflows. R2 is forming prestellar and protostellar cores at a rate of ∼ 55.3,M_⊙,Myr^-1, with an efficiency similar to the Orion integral shaped filament (ISF). The R1 filament, in contrast, lacks protostellar cores and only contains a few prestellar cores, resulting in an estimated star formation rate of ∼ -1 , which is lower by more than an order of magnitude than that of R2. Combining gas kinematics, core incidence, and the line-mass profiles, we suggest that R1 is younger and still rotates, while R2 has evolved to collapse with a higher star formation rate. G012 thus hosts filaments at different evolutionary stages.

A multiscale dynamical mass-assembly scenario, where stars form through multiscale fragmentation and hierarchical gas infall from clouds to filaments, clumps, and cores, has been proposed for high-mass star formation, but the precise observational picture of gas dynamics across these scales remains limited. We investigate the hierarchical fragmentation and multiscale gas infall within the high-mass star-forming filament IRAS 19368+2239 (hereafter, I19368) using 1.3 mm continuum mosaic observations from the Atacama Large Millimeter/submillimeter Array INFANT survey at a spatial resolution of ∼2800 au, complemented by molecular line data (e.g., NH ₃ , H _2CO ) tracing kinematics across different scales. The I19368 filament splits into two segments: a northern filament ( F _N ) and a southern filament ( F _S ). There are 15 dense cores along the filament, with 13 located in the denser F _S . Most cores are gravitationally bound and have high mass surface densities (Σ ≳ 1 g cm ⁻² ), indicating their potential to form high-mass stars. The cloud exhibits hierarchical fragmentation; the filament fragments into clumps via a cylindrical mode, and the clumps subsequently fragment into cores via a spherical Jeans mode, with both processes likely driven by turbulence. We further find a cascade of mass infall rates, decreasing from ∼6.5 × 10 ⁻⁴ M _⊙ yr ⁻¹ (cloud to filament) down to ∼(1−1.7) × 10 ⁻⁵ M _⊙ yr ⁻¹ (core to protostar), which could be driven by hierarchical gravitational collapse. Together, these results reveal a concurrent process in I19368; gravity-driven, multiscale gas infall coexists with turbulence-driven, hierarchical fragmentation, leading to high-mass star formation, supporting the multiscale, dynamical mass-assembly scenario for high-mass star formation.

A dynamic view of mass assembly is essential for understanding the formation of massive stars and clusters. However, interpreting evolutionary diagnostics from Galactic-wide surveys requires careful consideration of distance and environmental variations. The G316.8 filament provides an excellent controlled case: a 14-parsec, nearly linear structure comprising three contiguous subregions with comparable molecular gas reservoirs (each ~10 000 M _⊙ ), yet spanning a clear evolutionary sequence from a northern infrared dark cloud (young) through a central massive young stellar object (intermediate), to a southern H II region (evolved). The Linear filament and nested cluster evolution tomography (LANCET) project mapped the entire G316.8 filament with the Atacama Compact Array (ACA) at 1.3 mm, achieving 6″ (0.08 pc) resolution over 26.7 arcmin ² (17.1 pc ² ). By combining ACA 7 m data with Herschel and APEX/ArTéMiS observations, we produced high-resolution temperature and column-density maps. We quantified subregional differences using (i) dense-fragment statistics, (ii) column-density probability distribution functions (N-PDFs), and (iii) the scale-dependent structural diagnostic, the Δ-variance. From young to intermediate to evolved, the maximum fragment mass increases from 8 to 160 to 490 M _⊙ , while the dense-gas mass fraction (>0.5 g cm ⁻² ) rises from 0.4 to 2.3 to 9.6%. Along this sequence, the N-PDF develops a slightly flatter primary power-law tail and an additional, steeper secondary tail; the Δ-variance slope becomes progressively shallower. Across G316.8, the subregional differences consistently indicate a coherent evolutionary trend of massive star formation, in which gas is continuously assembled into sub-parsec dense structures. The forthcoming 12 m array observations are about to extend this dynamic picture by resolving dense core formation and probing gas kinematics and magnetic fields.

Context . High-mass star formation remains a major open problem in astrophysics, particularly regarding the transition between deeply embedded protostars and the onset of ionising radiation capable of producing photodissociation regions (PDRs) and compact H II regions. Aims . We aim to characterise the excitation and ionisation conditions of the high-mass star-forming region IRAS 18162−2048, which is where the parsec-scale jet HH80−81 lies. Methods . We obtained adaptive optics–assisted integral field spectroscopy in the near-IR K band (1.93–2.47 µm) with VLT/SINFONI, complemented by VLA X and C bands (3−6 cm) and ALMA band 3 (∼3.3 mm) observations. We analysed the continuum and line emission to derive visual extinction and excitation conditions and the kinematics of the gas of the region. Results . The near-IR continuum reveals two IR sources, IRS 2 and IRS 7, while the main protostellar core, IRAS 18162-2048, remains undetected up to 2.47 µm. IRS 7 shows a peculiar hydrogen recombination line (HRL) Br γ profile with a narrow emission component superimposed on a broad absorption feature, consistent with a B2/B3 zero-age main-sequence (ZAMS) star. Extended H ₂ emission exhibits a ‘sawtooth’ pattern in the excitation diagram, characteristic of UV radiation in a PDR rather than shock excitation. The radiative transfer model Cloudy reproduces the H ₂ ro-vibrational populations for T _gas = 600 K and n _H = 7.9 × 10 ³ cm ⁻³ . The VLA X and C bands observations reveal a compact radio source previously reported as a ‘stationary condensation’ (SC) and coincident with IRS 7. For the first time, we detect IRS 7/SC in millimetre wavelengths. The spectral index in the 3−6 cm and 3.3 mm regime is consistent with optically thin free–free emission. Conclusions . Our near-IR and radio observations reveal that IRS 7/SC is a B2/B3 ZAMS star that has begun to photo-ionise its environment, giving rise to an extended PDR and a compact H II region. The coexistence of this source with the deeply embedded protostar IRAS 18162-2048 and other bubble-like structures in the field suggests a multi-generational star-forming environment. Future James Webb Space Telescope observations targeting the H ₂ pure rotational lines (3–28 µm) and other HRLs less affected by extinction will be essential to characterising the cooler molecular and ionised gas to fully disclose the formation history of the region.

We present observations of the W51A region, including the massive protoclusters W51-E and W51-IRS2, with JWST in 10 NIRCam and 5 MIRI filters. In this work, we highlight the most novel features apparent in these images and compare them with other multiwavelength images. The broad view of the NIRCam/MIRI images of the W51A region shows that areas dominated by warm dust and ionized gas are distinct from those dominated by polycyclic aromatic hydrocarbons. The high angular resolution of the JWST images resolves dust filaments in high contrast, revealing geometrically converging features feeding W51-E and a cavity around W51-IRS2. This picture adds support to the hypothesis that feedback from W51-IRS2 is suppressing further gas infall onto the protocluster, while by contrast, gas is still accreting onto W51-E. Comparing the NIRCam and MIRI images to Atacama Large Millimeter/submillimeter Array (ALMA) data, we find 24 sources detected by both JWST and ALMA, accounting for only ∼10% of the ALMA sources; the rest are too embedded or too cool to be detected by JWST. A knot of [Fe ii ] and H ₂ emission north of W51-IRS2, previously detected in ground-based images, reveals peculiarly bright and compact peaks detected in all JWST bands. The knot is likely the most energetic example of a protostellar jet driven by a massive star impacting dense interstellar medium. The new images provide a complementary view to the previous long-wavelength perspective on this 4 × 8 pc area of one of the most active star-forming regions in our Galaxy, revealing new mysteries to be further explored.

We study the kinematics of condensations in 30 fields forming high-mass stars with the Atacama Large Millimeter/submillimeter Array at a high resolution of ∼ 0 . ″ 08 on average (∼230 au). The presence of disks is important for feeding high-mass stars without feedback halting growth as their masses increase. In the search for velocity gradients resembling rotation that can reveal the presence of disks, we analyze the emission of gas tracers in 49 objects using CH ₃ OH, CH ₃ CN, and tentative detections of HNCO and cis-HCOOH. Most of the velocity distributions show velocity gradients indicative of rotation. We reveal a total of 32 disk candidates, the largest sample to date that has been uniformly analyzed at a few hundred astronomical unit scales in the high-mass regime. Their position–velocity maps are generally asymmetric with one side brighter than the opposite. We successfully fit a power law to the position–velocity maps of the disk candidates and find indices between −0.5 (Keplerian rotation) and −1 (rotation under specific angular momentum conservation) with a median of −0.7. Under Keplerian rotation assumption, we estimate central masses, uncorrected for inclination, ranging between 7 and 45 M _⊙ . Excluding outliers, the disk candidates are relatively more compact (M _⊙ ) than previous results at coarser angular resolution. We calculate an average Toomre- Q parameter and find that most are gravitationally unstable (median of 0.5). We conclude that these observations offer the first opportunity to separate the disk and envelope components of hot cores on a statistically significant sample, and confirm that anisotropic collapse plays a role in feeding high-mass (proto)stars.