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The Recent Star Formation in Sextans A

Van Dyk, Schuyler D. and Puche, Daniel and Wong, Tony (1998) The Recent Star Formation in Sextans A. Astronomical Journal, 116 (5). pp. 2341-2362. ISSN 0004-6256. doi:10.1086/300584.

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We investigate the relationship between the spatial distributions of stellar populations and of neutral and ionized gas in the Local Group dwarf irregular galaxy Sextans A. This galaxy is currently experiencing a burst of localized star formation, the trigger of which is unknown. We have resolved various populations of stars via deep UBV(RI)_C imaging over an area with diameter ~5farcm3. We have compared our photometry with theoretical isochrones appropriate for Sextans A, in order to determine the ages of these populations. We have mapped out the history of star formation, most accurately for times ≾ 100 Myr. We find that star formation in Sextans A is correlated both in time and space, especially for the most recent (≾ 12 Myr) times. The youngest stars in the galaxy are forming primarily along the inner edge of the large H I shell. Somewhat older populations, ≾ 50 Myr, are found inward of the youngest stars. Progressively older star formation, from ~50–100 Myr, appears to have some spatially coherent structure and is more centrally concentrated. The oldest stars we can accurately sample appear to have approximately a uniform spatial distribution, which extends beyond a surface brightness of μ_B ≃ 25.9 mag arcsec^(-2) (or, a radius r ≃ 2farcm3). Although other processes are also possible, our data provide support for a mechanism of supernova-driven expansion of the neutral gas, resulting in cold-gas pileup and compression along the H I shell and sequential star formation in recent times.

Item Type:Article
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URLURL TypeDescription Paper
Van Dyk, Schuyler D.0000-0001-9038-9950
Additional Information:© 1998. The American Astronomical Society. Received 5 February 1998; revised 1998 July 8. We are grateful to Ralph Young Shuping for his photometric calibration observations of Sextans A at the KPNO 0.9 m telescope, to NOAO director Sydney Wolff for scheduling these observations, and Dave Summers for his assistance at the KPNO 2.1 m telescope. We thank Maggie Graham and Dave Westpfahl for making their total H I map available to us. S. V. D. is grateful for assistance provided by Alex Filippenko and also to the UCLA Division of Astronomy and Astrophysics. We thank Jean Turner, Tammy Smecker-Hane, Dave Westpfahl, and Dave Meier for helpful discussions. We also thank the referee for very helpful comments and suggestions. This research was supported by a grant from NASA administered by the American Astronomical Society.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
American Astronomical SocietyUNSPECIFIED
Subject Keywords:galaxies: dwarf; galaxies: evolution; galaxies: individual (Sextans A DDO 75) ; galaxies: photometry; galaxies: stellar content; Local Group
Issue or Number:5
Record Number:CaltechAUTHORS:20170408-171215119
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Official Citation:Schuyler D. Van Dyk et al 1998 AJ 116 2341
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76303
Deposited By: 1Science Import
Deposited On:12 Mar 2018 22:41
Last Modified:15 Nov 2021 16:58

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