A Caltech Library Service

Star Formation Histories of the LEGUS Dwarf Galaxies. II. Spatially Resolved Star Formation History of the Magellanic Irregular NGC 4449

Sacchi, E. and Cignoni, M. and Aloisi, A. and Tosi, M. and Calzetti, D. and Lee, J. C. and Adamo, A. and Annibali, F. and Dale, D. A. and Elmegreen, B. G. and Gouliermis, D. A. and Grasha, K. and Grebel, E. K. and Hunter, D. A. and Sabbi, E. and Smith, L. J. and Thilker, D. A. and Ubeda, L. and Whitmore, B C. (2018) Star Formation Histories of the LEGUS Dwarf Galaxies. II. Spatially Resolved Star Formation History of the Magellanic Irregular NGC 4449. Astrophysical Journal, 857 (1). Art. No. 63. ISSN 1538-4357. doi:10.3847/1538-4357/aab844.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Accepted Version
See Usage Policy.


Use this Persistent URL to link to this item:


We present a detailed study of the Magellanic irregular galaxy NGC 4449 based on both archival and new photometric data from the Legacy Extragalactic UV Survey, obtained with the Hubble Space Telescope Advanced Camera for Surveys and Wide Field Camera 3. Thanks to its proximity (D = 3.82 ± 0.27 Mpc), we reach stars 3 mag fainter than the tip of the red giant branch in the F814W filter. The recovered star formation history (SFH) spans the whole Hubble time, but due to the age–metallicity degeneracy of the red giant branch stars, it is robust only over the lookback time reached by our photometry, i.e., ~3 Gyr. The most recent peak of star formation (SF) is around 10 Myr ago. The average surface density SF rate over the whole galaxy lifetime is 0.01 M⊙ yr^(−1) kpc^(−2). From our study, it emerges that NGC 4449 has experienced a fairly continuous SF regime in the last 1 Gyr, with peaks and dips whose SF rates differ only by a factor of a few. The very complex and disturbed morphology of NGC 4449 makes it an interesting galaxy for studies of the relationship between interactions and starbursts, and our detailed and spatially resolved analysis of its SFH does indeed provide some hints on the connection between these two phenomena in this peculiar dwarf galaxy.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Sacchi, E.0000-0001-5618-0109
Cignoni, M.0000-0001-6291-6813
Aloisi, A.0000-0003-4137-882X
Tosi, M.0000-0002-0986-4759
Calzetti, D.0000-0002-5189-8004
Lee, J. C.0000-0002-2278-9407
Adamo, A.0000-0002-8192-8091
Annibali, F.0000-0003-3758-4516
Dale, D. A.0000-0002-5782-9093
Elmegreen, B. G.0000-0002-1723-6330
Gouliermis, D. A.0000-0002-2763-0075
Grasha, K.0000-0002-3247-5321
Grebel, E. K.0000-0002-1891-3794
Hunter, D. A.0000-0002-3322-9798
Sabbi, E.0000-0003-2954-7643
Smith, L. J.0000-0002-0806-168X
Thilker, D. A.0000-0002-8528-7340
Additional Information:© 2018 The American Astronomical Society. Received 2017 April 4; revised 2018 March 12; accepted 2018 March 18; published 2018 April 16. Based on observations obtained with the NASA/ESA Hubble Space Telescope at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA contract NAS 5-26555. These data are associated with the HST GO programs 10585 (PI: A. Aloisi) and 13364 (PI: D. Calzetti). Support for these programs was provided by NASA through grants from the Space Telescope Science Institute. E > S> is supported by INAF through a Ph.D. grant at the University of Bologna. D.A.G. kindly acknowledges financial support by the German Research Foundation (DFG) through program GO 1659/3-2. The authors profoundly thank Kristen McQuinn for the data provided and the useful discussions about this work.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASANAS 5-26555
Space Telescope Science InstituteUNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)GO 1659/3-2
Subject Keywords:galaxies: dwarf – galaxies: evolution – galaxies: individual (NGC 4449) – galaxies: irregular – galaxies: starburst – galaxies: star formation
Issue or Number:1
Record Number:CaltechAUTHORS:20180412-144611074
Persistent URL:
Official Citation:E. Sacchi et al 2018 ApJ 857 63
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85794
Deposited By: George Porter
Deposited On:12 Apr 2018 22:00
Last Modified:15 Nov 2021 20:32

Repository Staff Only: item control page