Star Formation Histories of the LEGUS Spiral Galaxies. I. The Flocculent Spiral NGC 7793

Creators: Sacchi, E.; Cignoni, M.; Aloisi, A.; Tosi, M.; Adamo, A.; Dale, D. A.; Elmegreen, B. G.; Elmegreen, D. M.; Calzetti, D.; Gouliermis, D. A.; Grasha, K.; Smith, L. J.; Wofford, A.; Lee, J. C.; Sabbi, E.; Ubeda, L.

Abstract

We present a detailed study of the flocculent spiral galaxy NGC 7793, part of the Sculptor group. By analyzing the resolved stellar populations of the galaxy, located at a distance of ~3.7 Mpc, we infer for the first time its radial star formation history (SFH) from Hubble Space Telescope photometry, thanks to both archival and new data from the Legacy ExtraGalactic UV Survey. We determine an average star formation rate (SFR) for the galaxy portion covered by our F555W and F814W data of 0.23 ± 0.02 M⊙ yr^(−1) over the whole Hubble time, corresponding to a total stellar mass of (3.09 ± 0.33) × 10^9 M⊙, in agreement with previous determinations. Thanks to the new data extending to the F336W band, we are able to analyze the youngest stellar populations with a higher time resolution. Most importantly, we recover the resolved SFH in different radial regions of the galaxy; this shows an indication of a growing trend of the present-to-past SFR ratio, increasing from internal to more external regions, supporting previous findings of the inside-out growth of the galaxy.

Additional Information

© 2019 The American Astronomical Society. Received 2019 February 15; revised 2019 April 17; accepted 2019 April 28; published 2019 June 6. 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 Program 13364 (PI D. Calzetti). Support for this program was provided by NASA through grants from the Space Telescope Science Institute. M.C. and M.T. acknowledge funding from the INAF PRIN-SKA 2017 program 1.05.01.88.04. A.A. acknowledges the support of the Swedish Research Council, Vetenskapsrådet and the Swedish National Space Agency (SNSA).

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