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Star Formation Histories of the LEGUS Dwarf Galaxies. III. The Nonbursty Nature of 23 Star-forming Dwarf Galaxies

Cignoni, M. and Sacchi, E. and Tosi, M. and Aloisi, A. and Cook, D. O. and Calzetti, D. and Lee, J. C. and Sabbi, E. and Thilker, D. A. and Adamo, A. and Dale, D. A. and Elmegreen, B. G. and Gallagher, J. S., III and Grebel, E. K. and Johnson, K. E. and Messa, M. and Smith, L. J. and Ubeda, L. (2019) Star Formation Histories of the LEGUS Dwarf Galaxies. III. The Nonbursty Nature of 23 Star-forming Dwarf Galaxies. Astrophysical Journal, 887 (2). Art. No. 112. ISSN 1538-4357.

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We derive the recent star formation histories (SFHs) of 23 active dwarf galaxies using Hubble Space Telescope observations from the Legacy Extragalactic UV Survey. We apply a color–magnitude diagram (CMD) fitting technique using two independent sets of stellar models, PARSEC-COLIBRI and MIST. Despite the nonnegligible recent activity, none of the 23 star-forming dwarfs show enhancements in the last 100 Myr larger than three times the 100 Myr average. The unweighted mean of the individual SFHs in the last 100 Myr is also consistent with a rather constant activity, irrespective of the atomic gas fraction. We confirm previous results that for dwarf galaxies, the CMD-based average star formation rates (SFRs) are generally higher than the FUV-based SFRs. For half of the sample, the 60 Myr average CMD-based SFR is more than two times the FUV SFR. In contrast, we find remarkable agreement between the 10 Myr average CMD-based SFR and the Hα-based SFR. Finally, using core helium-burning stars of intermediate mass, we study the pattern of star formation spatial progression over the past 60 Myr and speculate on the possible triggers and connections of the star formation activity with the environment in which these galaxies live. Approximately half of our galaxies show spatial progression of star formation in the last 60 Myr and/or very recent diffuse and off-center activity compared to RGB stars.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Cignoni, M.0000-0001-6291-6813
Sacchi, E.0000-0001-5618-0109
Tosi, M.0000-0002-0986-4759
Aloisi, A.0000-0003-4137-882X
Cook, D. O.0000-0002-6877-7655
Calzetti, D.0000-0002-5189-8004
Lee, J. C.0000-0002-2278-9407
Sabbi, E.0000-0003-2954-7643
Thilker, D. A.0000-0002-8528-7340
Adamo, A.0000-0002-8192-8091
Dale, D. A.0000-0002-5782-9093
Elmegreen, B. G.0000-0002-1723-6330
Gallagher, J. S., III0000-0001-8608-0408
Grebel, E. K.0000-0002-1891-3794
Johnson, K. E.0000-0001-8348-2671
Messa, M.0000-0003-1427-2456
Smith, L. J.0000-0002-0806-168X
Additional Information:© 2019 The American Astronomical Society. Received 2019 August 6; revised 2019 October 28; accepted 2019 November 1; published 2019 December 16. M.C. and M.T. kindly acknowledge partial funding from INAF PRIN-SKA-2017, program, and INAF Main Stream SSH, program
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Istituto Nazionale di Astrofisica (INAF)PRIN-SKA-2017
Istituto Nazionale di Astrofisica (INAF)
Istituto Nazionale di Astrofisica (INAF)
Subject Keywords:Dwarf irregular galaxies; Dwarf galaxies; Star formation; Blue loop; Massive stars; Interacting galaxies; Stellar evolutionary models
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Dwarf irregular galaxies (417); Dwarf galaxies (416); Star formation (1569); Blue loop (167); Massive stars (732); Interacting galaxies (802); Stellar evolutionary models (2046)
Record Number:CaltechAUTHORS:20200131-123803370
Persistent URL:
Official Citation:M. Cignoni et al 2019 ApJ 887 112
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101034
Deposited By: Tony Diaz
Deposited On:31 Jan 2020 20:45
Last Modified:31 Jan 2020 20:45

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