ALMA-IMF. XIV. Free–Free Templates Derived from H41α and Ionized Gas Content in 15 Massive Protoclusters

Abstract 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.

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Publication Details

Journal
The Astrophysical Journal Supplement Series
Published
2024-09-01
DOI
https://doi.org/10.3847/1538-4365/ad61e6
Citations
7
Primary Topic
Astrophysics and Star Formation Studies
Type
article
Field-Weighted Citation Impact
2.32

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article

ALMA-IMF. XIV. Free–Free Templates Derived from H41α and Ionized Gas Content in 15 Massive Protoclusters

M. Bonfand, Patricio Sanhueza, N. Cunningham, T. Nony et al.
7 citations
The Astrophysical Journal Supplement Series
Astrophysics and Star Formation Studies
2.32
article

ALMA-IMF. XIV. Free–Free Templates Derived from H41α and Ionized Gas Content in 15 Massive Protoclusters

M. Bonfand, Patricio Sanhueza, N. Cunningham, T. Nony, Tapas Baug, A. P. M. Towner, Roberto Galván-Madrid, P. Dell’Ova, A. Koley, Adam Ginsburg, D. Díaz-González, M. Armante, F. Motte, T. Csengeri, F. Wyrowski, Manuel Fernández-López, Rudy Rivera-Soto, F. Louvet, Amelia M. Stutz, K. M. Menten, S. Bontemps, R. H. Álvarez-Gutiérrez, A. P. Whitworth, A. Gusdorf, Hongli Liu, J. Salinas, Jonathan Braine, Leonardo Bronfman
article en
7 citations

Abstract

Abstract 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.

The Astrophysical Journal Supplement SeriesVol. 274(1)
University of Arizona (US), Consejo Nacional de Investigaciones Científicas y Técnicas (AR), University of Concepción (CL), Yunnan University (CN), National Institutes of Natural Sciences (JP), École Normale Supérieure - PSL (FR), University of Florida (US), Laboratoire d'Astrophysique de Bordeaux (FR), SKA Observatory (GB), Institut de Planétologie et d'Astrophysique de Grenoble (FR), Laboratoire de Physique de l'Ecole Normale Supérieure (FR), Instituto Argentino de Radioastronomía (AR), Max Planck Institute for Radio Astronomy (DE), National Astronomical Observatory of Japan (JP), University of Virginia (US), University of Chile (CL), S.N. Bose National Centre for Basic Sciences (IN), Cardiff University (GB), Universidad Nacional Autónoma de México (MX)
National Science Foundation, Consejo Nacional de Ciencia y Tecnología, Agencia Nacional de Investigación y Desarrollo, Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México
Openalex Percentile: Top 12%
Astrophysics and Star Formation Studies
2.32
DOIOpen Access PDFOpenAlex
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