Synthetic photometry of OB star clusters with stochastically sampled IMFs: analysis of models and HST observations - Sorbonne Université Access content directly
Journal Articles Monthly Notices of the Royal Astronomical Society Year : 2021

Synthetic photometry of OB star clusters with stochastically sampled IMFs: analysis of models and HST observations

Aida Wofford
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  • PersonId : 1140868
Alba Vidal-García
  • Function : Author
Stephen Hannon
Janice Lee
Daniel Dale
Matteo Messa
Kathryn Grasha
David Cook

Abstract

We present a pilot library of synthetic NUV, U, B, V, and I photometry of star clusters with stochastically sampled IMFs and ionized gas for initial masses, M i = 10 3 , 10 4 , and 10 5 M ; t = 1, 3, 4, and 8 Myr; Z = 0.014 and Z = 0.002; and log(U S) =-2 and-3. We compare the library with predictions from deterministic models and observations of isolated low-mass (< 10 4 M) star clusters with co-spatial compact H ii regions. The clusters are located in NGC 7793, one of the nearest galaxies observed as part of the HST LEGUS and Hα-LEGUS surveys. 1) For model magnitudes that only account for the stars: a) the residual |deterministic mag-median stochastic mag| can be ≥ 0.5 mag, even for M i = 10 5 M ; and b) the largest spread in stochastic magnitudes occurs when Wolf-Rayet stars are present. 2) For M i = 10 5 M : a) the median stochastic mag with gas can be >1.0 mag more luminous than the median stochastic magnitude without gas; and b) nebular emission lines can contribute with > 50% and > 30% to the total emission in the V and I bands, respectively. 3) Age-dating OB-star clusters via deterministic tracks in the U-B vs. V-I plane is highly uncertain at Z = 0.014 for M i ∼ 10 3 M and Z = 0.002 for M i ∼ 10 3 − 10 5 M. 4) For low-mass clusters, the V-band extinction derived with stochastic models significantly depends on the value of log(U S). 5) The youngest clusters tend to have higher extinction. 6) The majority of clusters have multi-peaked age PDFs. 7) Finally, we discuss the importance of characterising the true variance in the number of stars per mass bin in nature.
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Dates and versions

hal-03556874 , version 1 (04-02-2022)

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Rogelio Orozco-Duarte, Aida Wofford, Alba Vidal-García, Gustavo Bruzual, Stephane Charlot, et al.. Synthetic photometry of OB star clusters with stochastically sampled IMFs: analysis of models and HST observations. Monthly Notices of the Royal Astronomical Society, 2021, 509 (1), pp.522-549. ⟨10.1093/mnras/stab2988⟩. ⟨hal-03556874⟩
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