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We use the H41 α recombination line to create templates of the millimeter free–free emission in the ALMA-IMF continuum maps, which allows us to separate it from dust emission. This method complements spectral-index information and extrapolation from centimeter-wavelength maps. We use the derived maps to estimate the properties of up to 34 H ii regions across the ALMA-IMF protoclusters. The hydrogen ionizing photon rate Q _0 and spectral types follow the evolutionary trend proposed by Motte et al. The youngest protoclusters lack detectable ionized gas, followed by protoclusters with increasing numbers of OB stars. The total Q _0 increases from ∼10 ^45 s ^−1 to >10 ^49 s ^−1 . We used the adjacent He41 α line to measure the relative number abundances of helium, finding values consistent with the Galactic interstellar medium, although a few outliers are discussed. A search for sites of maser amplification of the H41 α line returned negative results. We looked for possible correlations between the electron densities, emission measures, and Q _0 with H ii region size D . The latter is the best correlated, with Q _0 ∝ D ^2.49 ± 0.18 . This favors interpretations in which smaller ultracompact H ii regions are not necessarily the less dynamically evolved versions of larger ones but rather are ionized by less massive stars. Moderate correlations were found between the dynamical width Δ V _dyn with D and Q _0 . Δ V _dyn increases from about 1 to 2 times the ionized-gas sound speed. Finally, an outlier H ii region south of W43-MM2 is discussed. We suggest that this source could harbor an embedded stellar or disk wind.

We present the combination of ALMA-IMF and single-dish continuum images from the MUSTANG-2 Galactic Plane Survey (MGPS90) at 3 mm and the Bolocam Galactic Plane Survey (BGPS) at 1 mm. Six and 10 out of the 15 ALMA-IMF fields are combined with MGPS90 and BGPS, respectively. The combination is made via the feathering technique. We used the dendrogram algorithm throughout the combined images, and performed further analysis in the six fields with the combination in both bands (G012.80, W43-MM1, W43-MM2, W43-MM3, W51-E, W51-IRS2). In these fields, we calculated spectral index maps and used them to separate regions dominated by dust or free–free emission, and then performed further structural analysis. We report the basic physical parameters of the dust-dominated (column densities, masses) and ionized (emission measures, hydrogen ionization photon rates) structures. We also searched for multiscale relations in the dust-dominated structures across the analyzed fields, finding that the fraction of mass in dendrogram leaves (which we label leaf mass efficiency (LME)) as a function of molecular gas column density follows a similar trend: a rapid, exponential-like growth, with maximum values approaching 100% in most cases. The observed behavior of the LME with the gas column is tentatively interpreted as an indicator of large star formation activity within the ALMA-IMF protoclusters. W51-E and G012.80 stand out as cases with comparatively large and reduced potential for further star formation, respectively.

We present initial results from the K-band Focal Plane Array Examinations of Young STellar Object Natal Environments survey, a large project on the 100 m Green Bank Telescope mapping ammonia emission across 11 giant molecular clouds at distances of 0.9–3.0 kpc (Cygnus X North, Cygnus X South, M16, M17, Mon R1, Mon R2, NGC 2264, NGC 7538, Rosette, W3, and W48). This data release includes the NH3 (1,1) and (2,2) maps for each cloud, which are modeled to produce maps of kinetic temperature, centroid velocity, velocity dispersion, and ammonia column density. Median cloud kinetic temperatures range from 11.4 ± 2.2 K in the coldest cloud (Mon R1) to 23.0 ± 6.5 K in the warmest cloud (M17). Using dendrograms on the NH3 (1,1) integrated intensity maps, we identify 856 dense gas clumps across the 11 clouds. Depending on the cloud observed, 40%–100% of the clumps are aligned spatially with filaments identified in H2 column density maps derived from spectral energy distribution fitting of dust continuum emission. A virial analysis reveals that 523 of the 835 clumps (∼63%) with mass estimates are bound by gravity alone. We find no significant difference between the virial parameter distributions for clumps aligned with the dust-continuum filaments and those unaligned with filaments. In some clouds, however, hubs or ridges of dense gas with unusually high mass and low virial parameters are located within a single filament or at the intersection of multiple filaments. These hubs and ridges tend to host water maser emission, multiple 70 μm detected protostars, and have masses and radii above an empirical threshold for forming massive stars. [ABSTRACT FROM AUTHOR]

We explored the implication of the association (or lack of it) of 6.7 GHz class II methanol (CH3OH) masers with massive dense cores (MDCs) detected (within a sample of ATLASGAL selected infrared quiet massive clumps) at 0.9 mm with Atacama Large Millimeter/submillimeter array. We found 42 out of the 112 cores (37.5%) detected with the Atacama Compact Array (ACA) to be associated with 6.7 GHz CH3OH masers. The lowest mass core with CH3OH maser association is . The angular offsets of the ACA cores from the 6.7 GHz CH3OH maser peak positions range from 0.″17 to 4.″79, with a median value of 2.″19. We found a weak correlation between the 0.9 mm continuum (MDCs) peak fluxes and the peak fluxes of their associated methanol multibeam (MMB) 6.7 GHz CH3OH masers. About 90% of the cores associated with 6.7 GHz CH3OH masers have masses of >40 M⊙. The CH3OH maser containing cores are candidates for embedded high-mass protostellar objects in their earliest evolutionary stages. With our ACA 0.9 continuum data compared with the MMB 6.7 GHz CH3OH maser survey, we have constrained the cores already housing massive protostars based on their association with the radiatively pumped 6.7 GHz CH3OH masers. [ABSTRACT FROM AUTHOR]