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Age Dependence of Mid-infrared Emission around Young Star Clusters

Lin, Zesen and Calzetti, Daniela and Kong, Xu and Adamo, A. and Cignoni, M. and Cook, D. O. and Dale, D. A. and Grasha, K. and Grebel, E. K. and Messa, M. and Sacchi, E. and Smith, L. J. (2020) Age Dependence of Mid-infrared Emission around Young Star Clusters. Astrophysical Journal, 896 (1). Art. No. 16. ISSN 1538-4357. doi:10.3847/1538-4357/ab9106.

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Using the star cluster catalogs from the Hubble Space Telescope program Legacy Extragalactic UV survey (LEGUS) and 8 μm images from the IRAC camera on the Spitzer Space Telescope for five galaxies within 5 Mpc, we investigate how the 8 μm dust luminosity correlates with the stellar age on the 30–50 pc scale of star-forming regions. We construct a sample of 97 regions centered at local peaks of 8 μm emission, each containing one or more young star cluster candidates from the LEGUS catalogs. We find a tight anticorrelation with a Pearson correlation coefficient of r = −0.84 ± 0.05 between the mass-normalized dust-only 8 μm luminosity and the age of stellar clusters younger than 1 Gyr; the 8 μm luminosity decreases with increasing age of the stellar population. Simple assumptions on a combination of stellar and dust emission models reproduce the observed trend. We also explore how the scatter of the observed trend depends on assumptions of stellar metallicity, polycyclic aromatic hydrocarbon (PAH) abundance, fraction of stellar light absorbed by dust, and instantaneous versus continuous star formation models. We find that variations in stellar metallicity have little effect on the scatter, while PAH abundance and the fraction of dust-absorbed light bracket the full range of the data. We also find that the trend is better explained by continuous star formation, rather than instantaneous burst models. We ascribe this result to the presence of multiple star clusters with different ages in many of the regions. Upper limits of the dust-only 8 μm emission as a function of age are provided.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Lin, Zesen0000-0001-8078-3428
Calzetti, Daniela0000-0002-5189-8004
Kong, Xu0000-0002-7660-2273
Adamo, A.0000-0002-8192-8091
Cignoni, M.0000-0001-6291-6813
Cook, D. O.0000-0002-6877-7655
Dale, D. A.0000-0002-5782-9093
Grasha, K.0000-0002-3247-5321
Grebel, E. K.0000-0002-1891-3794
Messa, M.0000-0003-1427-2456
Sacchi, E.0000-0001-5618-0109
Smith, L. J.0000-0002-0806-168X
Additional Information:© 2020 The American Astronomical Society. Received 2019 December 23; revised 2020 May 1; accepted 2020 May 5; published 2020 June 9. The authors would like to thank B. T. Draine for helpful discussions. This work is supported by the National Key R&D Program of China (2017YFA0402600) and the National Natural Science Foundation of China (NSFC, Nos. 11421303, 11433005, and 11973038). Z.L. gratefully acknowledges support from the China Scholarship Council (No. 201806340211). Software: APLpy (Robitaille & Bressert 2012), Astropy (Astropy Collaboration et al. 2013, 2018), IPython (Pérez & Granger 2007), IRAF (Tody 1986, 1993), Matplotlib (Hunter 2007), MPFIT (Markwardt 2009), Numpy (Oliphant 2006), Photutils (Bradley et al. 2019), Starburst99 (Leitherer et al. 1999; Vázquez & Leitherer 2005).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
National Program on Key Research and Development Project2017YFA0402600
National Natural Science Foundation of China11421303
National Natural Science Foundation of China11433005
National Natural Science Foundation of China11973038
China Scholarship Council201806340211
Subject Keywords:Interstellar medium ; Star formation ; Young star clusters ; Infrared sources ; Polycyclic aromatic hydrocarbons ; Stellar ages
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Interstellar medium (847); Star formation (1569); Young star clusters (1833); Infrared sources (793); Polycyclic aromatic hydrocarbons (1280); Stellar ages (1581)
Record Number:CaltechAUTHORS:20200710-130233427
Persistent URL:
Official Citation:Zesen Lin et al 2020 ApJ 896 16
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104330
Deposited By: Tony Diaz
Deposited On:10 Jul 2020 22:39
Last Modified:16 Nov 2021 18:30

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