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Leo A.-This dwarf Irr galaxy is a possible member of the Local Group. We did not find any X-ray emission from this galaxy. Leo A provides a stark contrast to the other galaxies in this sample. The color-magnitude data are from Tolstoy et al. (1998). The smallest, most isolated galaxy in the sample, the CMD of Leo A shows the unusual feature of a dominant blue supergiant branch, evidence for strong recent star formation. Leo A's giant branch lies to the blue of IC 1613's, indicating its lower metallicity (and/or age). The blue, vertically extended RC in Leo A suggests that this galaxy is dominated by an ~1 Gyr population. Deep WIYN and Multiple Mirror Telescope images of Leo A have failed to reveal an extended Baade's sheet population of red giants that would be indicative of significant early star formation (A. Saha 1998, private communication; Tolstoy et al. 1998). The low metallicity and high gas fraction of Leo A are all consistent with a galaxy that has not had a major star formation episode until quite recently. Leo A is even more isolated than IC 1613 (its nearest neighbors are the Leo I and Leo II dwarf spheroidals, more than 450 kpc away), and it must stand as a counterexample to the Tucana dwarf, a purely old system (Da Costa 1998), in evolutionary studies of small, isolated galaxies. Leo A. Demers et al. (1984) (photographic photometry). The estimates of V(5) obtained from the color-magnitude diagrams of Hoessel (1986) and Sandage (1986) are the same. LeoA. Sandage (1986) (Cepheids); Sandage (1986) (nos. 90, 30, 52), (nos. 65, 64, 39). Not all of the bright stars were photometered by Demers et al. (1984). ImV PH-95-S Jan 3/4, 1952 103aO + WG2 15 min The dwarf galaxy Leo A (RA_50_ = 9^h^ 57.55^m^, Dec_50_ = +30^deg^ 59.2') was discovered by Zwicky (1942) in one of the first surveys done with the Palomar 18-inch Schmidt beginning in 1936. Photometry of the stellar content (Sandage 1986b) shows that the brightest blue stars begin to resolve at B = 19 and the brightest red supergiants at V = 19. Leo A is one of the faintest dwarfs of type Im in or near the Local Group. If the distance modulus is m - M = 26 (Sandage 1986b), its absolute magnitude is M_B_ = -13. Leo A has a redshift relative to the centroid of the Local Group of v_o = -32 km/s (Sandage 1986a). It is, therefore, a Local Group member near the zero velocity surface that separates the Local Group from the cosmological expansion field. It is evident from the velocity and distance data that the kinematic radius of the Local Group in the direction of Leo A extends to a distance of about 1.6 Mpc from the Sun. Leo A = DDO 69 This dwarf irregular galaxy is listed as a local Group member by Kraan-Korteweg & Tammann (1979). However, Demers et al. (1984) obtain (m - M)_0_ = 26.8+/-0.4, corresponding to a distance of 2.3+/-0.4 Mpc. A slightly smaller, but very uncertain, distance modulus (m - M)_0_ = 26+/-1 has been advocated by Sandage (1986a). The position of Leo A in the V_sun_ versus cos{theta} plot is consistent with membership in the local Group. = DDO 069 Dwarf Leo A system. DDO 69, A0956 in RC1 Ir I (Holmberg) Ir V (DDO) = Leo A = Leo III. Possible member of Local Group. = Zwicky Object in Leo = Leo A Photograph: Sci. Monthly, 51, 400, 1940. Applied Mech., Th. Von Karman Anniv. Vol., p.137, Plate I, 1941. Magnitude and Distance: Mt. Wilson Report, 20, 1939-1940. |