Bibcode
Aparicio, A.; Garcia-Pelayo, J. M.; Moles, M.; Melnick, J.
Bibliographical reference
Astronomy and Astrophysics Supplement Series (ISSN 0365-0138), vol. 71, no. 2, Nov. 1987, p. 297-338. Research supported by the Consejo Superior de Investigaciones Cientificas and Universidad de Chile.
Advertised on:
11
1987
Citations
37
Refereed citations
34
Description
CCD UBV photometry of 2279 stars in Sextans A is presented. Differences
with the photometric scales of Sandage and Carlson (1985) and Hoessel et
al. (1983) are discussed; recalibration of the Sandage and Carlson data
for Cepheids in Sextans A results in a smaller value for the distance
modulus, μ = 25.6. A similar value for the distance modulus is
obtained from the colour-colour diagram. Colour-colour and
colour-magnitude diagrams for the whole galaxy and, for different parts,
are presented indicating a general star formation activity throughout
Sextans A. The contribution of stars brighter than Mpg = -3
to the total blue light of the galaxy amounts to 25%, a much higher
value than is found for other dwarf irregular galaxies in the Local
Group. The integrated birthrate per unit mass of massive stars for the
galaxy is found to be much higher than in the Magellanic Clouds,
suggesting that the rate in Sextans A was probably smaller in the past.
Different slopes for high mass and low mass IMF parts are needed to
account for its low surface brightness. The formation of massive stars
seems to be favoured for systems of decreasing mass or, given the
relation between total mass and metal content, for galaxies of
decreasing metallicity.