Low-Metallicity Star Formation Survey in Sh2-284 (LZ-STAR). II. The inital mass function

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Main Authors:	Andersen, M., Brizawasi, A., Cheng, Y., Tan, J. C., Fedriani, R., Armstrong, J. J., Robberto, M., Aghakhanloo, M.
Format:	Preprint
Published:	2025
Subjects:	Astrophysics of Galaxies
Online Access:	Acceder al recurso
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author	Andersen, M. Brizawasi, A. Cheng, Y. Tan, J. C. Fedriani, R. Armstrong, J. J. Robberto, M. Aghakhanloo, M.
author_facet	Andersen, M. Brizawasi, A. Cheng, Y. Tan, J. C. Fedriani, R. Armstrong, J. J. Robberto, M. Aghakhanloo, M.
contents	To fully understand the star formation process, we are compelled to study it in a variety of environments. Of particular interest are how star formation and the resulting initial mass function (IMF) vary as a function of metallicity. We have observed an embedded young cluster in Sh2-284 (hereafter S284), the HII region associated with the open cluster Dolidze 25 using JWST/NIRCam with the aim to study star formation in a metal-poor, i.e., about 1/3 of solar, environment. In particular, we aim to measure the peak of the IMF. Using JWST NIRCam photometry, we identified the embedded cluster S284-EC1 and resolved its low-mass content. By comparison with pre-main sequence evolutionary tracks we determine the mass and extinction for the individual cluster members. Extinction limited samples are created based on the distribution of extinction and the completeness of the data. For the region with a completeness of 50% or higher, we have fitted a log-normal distribution to the IMF. Adopting a fiducial age of 1 Myr of the members, the peak of the IMF is found to be at mc = 0.16+-0.02Msun, which is significantly smaller than the peak mass measured in local young clusters, such as mc = 0.26+0.11-0.07 Msun in the Orion Nebula Cluster (Gennaro & Robberto 2020), or the local Galactic disk value of mc = 0.25 Msun (Chabrier 2005). We have found evidence for IMF variation as a function of metallicity, i.e., the peak of the IMF shifts to lower masses as one goes from solar to 1/3 solar metallicity. However, we caution that the result is sensitive to the assumed age of the stellar population, i.e., with peak mass rising if an age older than 1 Myr is adopted. This study further motivates the need for expanded samples of low-metallicity regions and their content to enable more comprehensive measures of the IMF in such environments.
format	Preprint
id	arxiv_https___arxiv_org_abs_2505_12802
institution	arXiv
publishDate	2025
record_format	arxiv
spellingShingle	Low-Metallicity Star Formation Survey in Sh2-284 (LZ-STAR). II. The inital mass function Andersen, M. Brizawasi, A. Cheng, Y. Tan, J. C. Fedriani, R. Armstrong, J. J. Robberto, M. Aghakhanloo, M. Astrophysics of Galaxies To fully understand the star formation process, we are compelled to study it in a variety of environments. Of particular interest are how star formation and the resulting initial mass function (IMF) vary as a function of metallicity. We have observed an embedded young cluster in Sh2-284 (hereafter S284), the HII region associated with the open cluster Dolidze 25 using JWST/NIRCam with the aim to study star formation in a metal-poor, i.e., about 1/3 of solar, environment. In particular, we aim to measure the peak of the IMF. Using JWST NIRCam photometry, we identified the embedded cluster S284-EC1 and resolved its low-mass content. By comparison with pre-main sequence evolutionary tracks we determine the mass and extinction for the individual cluster members. Extinction limited samples are created based on the distribution of extinction and the completeness of the data. For the region with a completeness of 50% or higher, we have fitted a log-normal distribution to the IMF. Adopting a fiducial age of 1 Myr of the members, the peak of the IMF is found to be at mc = 0.16+-0.02Msun, which is significantly smaller than the peak mass measured in local young clusters, such as mc = 0.26+0.11-0.07 Msun in the Orion Nebula Cluster (Gennaro & Robberto 2020), or the local Galactic disk value of mc = 0.25 Msun (Chabrier 2005). We have found evidence for IMF variation as a function of metallicity, i.e., the peak of the IMF shifts to lower masses as one goes from solar to 1/3 solar metallicity. However, we caution that the result is sensitive to the assumed age of the stellar population, i.e., with peak mass rising if an age older than 1 Myr is adopted. This study further motivates the need for expanded samples of low-metallicity regions and their content to enable more comprehensive measures of the IMF in such environments.
title	Low-Metallicity Star Formation Survey in Sh2-284 (LZ-STAR). II. The inital mass function
topic	Astrophysics of Galaxies
url	https://arxiv.org/abs/2505.12802