EWOCS-III: JWST observations of the supermassive star cluster Westerlund 1

Context . The typically large distances, extinction, and crowding of Galactic supermassive star clusters (stellar clusters more massive than 10 4 M ⊙ ) have so far hampered the identification of their very low mass members, required to extend our understanding of star and planet formation, and early stellar evolution, to the extremely energetic star-forming environment typical of starbursts. This situation has now evolved thanks to the James Webb Space Telescope (JWST), and its unmatched resolution and sensitivity in the infrared. Aims . In this paper, the third of the series of the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS), we present JWST/NIRCam and JWST/MIRI observations of the supermassive star cluster Westerlund 1. These observations are specifically designed to unveil the cluster members down to the brown dwarf mass regime, and to allow us to select and study the protoplane-tary disks in the cluster and to study the mutual feedback between the cluster members and the surrounding environment. Methods . Westerlund 1 was observed as part of JWST GO-1905 for 23.6 hours. The data have been reduced using the JWST calibration pipeline, together with specific tools necessary to remove artifacts, such as the 1 / f random noise in NIRCam images. Source identification and photometry were performed with DOLPHOT . Results . The MIRI images show a plethora of different features. Diffuse nebular emission is observed around the cluster, which is typically composed of myriads of droplet-like features pointing toward the cluster center or the group of massive stars surrounding the Wolf–Rayet star W72/A. A long pillar is also observed in the northwest. The MIRI images also show resolved shells and outflows surrounding the M-type supergiants W20, W26, W75, and W237, the sgB[e] star W9 and the yellow hypergiant W4. Some of these shells have been observed before at other wavelengths, but never with the level of detail provided by JWST. The color-magnitude diagrams built using the NIRCam photometry show a clear cluster sequence, which is marked in its upper part by the 1828 NIRCam stars with X-ray counterparts. NIRCam observations using the F115W filter have reached the 23.8 mag limit with 50% completeness (roughly corresponding to a 0.06 M0 brown dwarf).

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Journal
Astronomy and Astrophysics
Published
2024-11-15
DOI
https://doi.org/10.1051/0004-6361/202452150
Citations
7
Primary Topic
Stellar, planetary, and galactic studies
Type
article
Field-Weighted Citation Impact
2.32

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article

EWOCS-III: JWST observations of the supermassive star cluster Westerlund 1

C. Argiroffi, K. Mužić, Tamara Rom, M. G. Guarcello et al.
7 citations
Astronomy and Astrophysics
Stellar, planetary, and galactic studies
2.32
article

EWOCS-III: JWST observations of the supermassive star cluster Westerlund 1

C. Argiroffi, K. Mužić, Tamara Rom, M. G. Guarcello, Elena Sabbi, A. Ginsburg, M. Andersen, Peter Zeidler, E. Moraux, Mario Gennaro, B. W. Ritchie, K. Anastasopoulou, R. Bonito, F. Damiani, Joseph L. Hora, Andrew J. Winter, J. J. Drake, F. Najarro, Joshua B. Lovell, L. Prisinzano, V. Almendros-Abad, Massimo Robberto, E. K. Grebel, I. Negueruela, A. Bayo, N. J. Wright, Noel D. Richardson, S. Sciortino, Kristina Monsch, Juan Rafael Martínez-Galarza, G. Umana, D. Capela
article en
7 citations

Abstract

Context . The typically large distances, extinction, and crowding of Galactic supermassive star clusters (stellar clusters more massive than 10 4 M ⊙ ) have so far hampered the identification of their very low mass members, required to extend our understanding of star and planet formation, and early stellar evolution, to the extremely energetic star-forming environment typical of starbursts. This situation has now evolved thanks to the James Webb Space Telescope (JWST), and its unmatched resolution and sensitivity in the infrared. Aims . In this paper, the third of the series of the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS), we present JWST/NIRCam and JWST/MIRI observations of the supermassive star cluster Westerlund 1. These observations are specifically designed to unveil the cluster members down to the brown dwarf mass regime, and to allow us to select and study the protoplane-tary disks in the cluster and to study the mutual feedback between the cluster members and the surrounding environment. Methods . Westerlund 1 was observed as part of JWST GO-1905 for 23.6 hours. The data have been reduced using the JWST calibration pipeline, together with specific tools necessary to remove artifacts, such as the 1 / f random noise in NIRCam images. Source identification and photometry were performed with DOLPHOT . Results . The MIRI images show a plethora of different features. Diffuse nebular emission is observed around the cluster, which is typically composed of myriads of droplet-like features pointing toward the cluster center or the group of massive stars surrounding the Wolf–Rayet star W72/A. A long pillar is also observed in the northwest. The MIRI images also show resolved shells and outflows surrounding the M-type supergiants W20, W26, W75, and W237, the sgB[e] star W9 and the yellow hypergiant W4. Some of these shells have been observed before at other wavelengths, but never with the level of detail provided by JWST. The color-magnitude diagrams built using the NIRCam photometry show a clear cluster sequence, which is marked in its upper part by the 1828 NIRCam stars with X-ray counterparts. NIRCam observations using the F115W filter have reached the 23.8 mag limit with 50% completeness (roughly corresponding to a 0.06 M0 brown dwarf).

Astronomy and AstrophysicsVol. 693
Lockheed Martin (United States) (US), Centre National de la Recherche Scientifique (FR), Space Telescope Science Institute (US), University of Alicante (ES), European Southern Observatory (DE), University of Arizona (US), University of Lisbon (PT), Université Côte d'Azur (FR), The Open University (GB), Heidelberg University (DE), University of Florida (US), Institute of Astrophysics and Space Sciences (PT), Gemini North Observatory (US), Gemini South Observatory (CL), Osservatorio Astrofisico di Catania (IT), Center for Astrophysics Harvard & Smithsonian (US), Observatoire de la Côte d’Azur (FR), Osservatorio Astronomico di Palermo (IT), Centro de Astrobiología (ES), Keele University (GB), Embry–Riddle Aeronautical University (US), Université Grenoble Alpes (FR), University of Palermo (IT), University of Split (HR)
National Science Foundation, Smithsonian Institution, National Aeronautics and Space Administration, Space Telescope Science Institute, Ministerio de Ciencia, Innovación y Universidades, European Commission, Deutsche Forschungsgemeinschaft, Generalitat Valenciana, Istituto Nazionale di Astrofisica, Horizon 2020 Framework Programme, Fundação para a Ciência e a Tecnologia, European Regional Development Fund, Agencia Estatal de Investigación
Life below water
Openalex Percentile: Top 12%
Stellar, planetary, and galactic studies
2.32
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