ARlogo Annu. Rev. Astron. Astrophys. 1998. 36: 435-506
Copyright © 1998 by Annual Reviews. All rights reserved

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9. CONCLUSIONS

I hope that I have been able to convey the rich detail, the surprises, and the broad relevance of modern research on Local Group dwarfs. Nevertheless, this review only scratches the surface of this active field. Table 8 provides a census of various specific types of objects (variable stars; young, intermediate-age, and old ISM; and stellar population tracers) that can and have been used to study these systems in greater detail. Keep in mind that these dwarfs offer our best opportunities to study how stellar evolution proceeds in chemically young environments; they offer our best window into the nature of DM in what may be the smallest natural size scales of this material; and they may help us understand if and how dwarfs help form larger galaxies via mergers. Many targets useful to attack these problems can be found in Table 8. We still have plenty of work to do with these nearby dwarfs to address these issues as well as the many others raised in this review.

Table 8. Summary of the contents of Local Group dwarf galaxies

Galaxya NRRb NCephc NMirad NACe Ref.f NOBAg NWRh NHIIi NDustj Ref.k NAGBl NPNm NGCn Ref.o

WLMo 15 64 21 37 10 2 1 2, 18, 32, 98
NGC 55 13 95 14+ 5 55, 94, 96
IC 10 5–9 61, 97 16 144 34, 51, 76 1 98
NGC 147 32 60, 99 0 100 Yes 5 3 23, 28, 32, 101
And III Yes? 5
NGC 185 151 59 1 2 42, 100, 102 Yes 5 9 16, 23, 32, 49
NGC 205p,q 30 12 ~9 58 Yes? 12 92 7+ 28 12 16, 32, 47, 56,
 92, 93
M32 0 0 103–105 Yes 30 0 16, 26, 32, 72,
 73, 144
And I 4+ 91 Yes 5, 6
Sculptorp 226+ 1 11? 43, 52, 66, 82, 140 8 0 8, 9, 106–108,
 143
LGS 3 0 37, 109 Yes 46
IC 1613 15 77+ 13, 92, 110, 111 20 1 77 11 7, 31, 35, 54, 112 15 1 0 18, 32, 40, 71,
 113
And II
Phoenix 60? 69 Yes 114
Fornaxr,s 400+ 1 30 1 52, 70, 75, 136 82 1 5 10, 32, 106, 115,
 116, 143
EGB 0427+63 25 37
Carinap 69 9 43, 50, 52, 74, 83 9 8, 9, 143
Leo A 5? 38, 39 6–10 109, 117, 118 Yes 2–4 98, 117, 120
Sextans B 36 7 1 6 13, 53, 63 12 118, 121 0 98
NGC 3109 29 13, 14, 22, 65, 80 18 39 Yes 12, 14, 29 Yes 7 0–10 22, 57, 98, 122
Antlia 1 Yes? 78, 124 Yes 78, 123, 124
Leo Ip Yes? 15 19, 50, 52, 85, 125 19 8–10, 48, 143
Sextans A 10 13, 53, 62, 126 1+ 25 4, 33, 109, 127 Yes 1 98, 129
Sextans 36 1 6 50 0 143
Leo IIp 152 4 21, 50, 52, 81 8 8–10, 20, 45,
 130, 143
GR 8 1? 5? 67 0 32 36, 132 Yes 0 96, 133
Ursa Minort 82 7 32, 52 1 9, 10
Dracop 280+ 5+ 52, 85, 134, 139 3–4 9, 10
Sagittarius 313+ 4 1, 84, 135 4+ 2 4 41, 84, 87–90
SagDIG 3 118 Yes 137
NGC 6822o,u 13 13, 25, 44 16 4 157 11 7, 17, 30, 68, 131 40 8+ 1 18, 24, 32, 138
DDO 210 0 69 Yes? 1 27
IC 5152 Yes? 69
Tucana Yes 3? 15, 142 No? 15, 141, 142
UKS2323-326
Pegasus 7–10 38 1 3 Yes 1 3, 98

 a Galaxy name.
 b-e The census of known populations of variable stars: RR Lyr stars, Cepheids, Mira (long-period) variables, and Anomalous Cepheids.
 f References for variable stars: 1, Alard 1996; 2, Ables & Ables 1977; 3, Aparicio 1994; 4, Aparicio & Rodríguez-Ulloa 1992; 5, Armandroff et al 1993; 6, Mould & Kristian 1990; 7, Armandroff & Massey 1991; 8, Azzopardi et al 1985; 9, Azzopardi et al 1986; 10, Aaronson et al 1983; 11, deleted in proof; 12, Bresolin et al 1993; 13, Capaccioli et al 1992; 14, Sandage & Carlson 1988; 15, Castellani et al 1996; 16, Ciardullo et al 1989; 17, Collier & Hodge 1994; 18, Cook et al 1986; 19, Demers et al 1994a; 20, Demers & Irwin 1993; 21, Swope 1967; 22, Demers et al 1985; 23, Ford et al 1977; 24, Gallart et al 1996a; 25, Gallart et al 1996c; 26, Grillmair et al 1996; 27, Greggio et al 1993; 28, Han et al 1997; 29, Hodge 1969; 30, Hodge 1977; 31, Hodge 1978; 32, Hodge 1988; 33, Hodge et al 1994; 34, Hodge & Lee 1990; 35, Hodge et al 1990; 36, Hodge et al 1989; 37, Hodge & Miller 1995; 38, Hoessel et al 1990; 39, Hoessel et al 1994; 40, Freedman 1988a; 41, Ibata et al 1994; 42, Hodge 1963b; 43, Kaluzny et al 1995; 44, Kayser 1967; 45, Lee 1995b; 46, Lee 1995a; 47, Lee 1996; 48, Lee et al 1993a; 49, Lee et al 1993c; 50, Mateo et al 1995a; 51, Massey et al 1992; 52, Nemec et al 1988; 53, Piotto et al 1994; 54, Price et al 1990; 55, Pritchet et al 1987; 56, Richer et al 1984; 57, Richer & McCall 1992; 58, Saha et al 1992b; 59, Saha & Hoessel 1990; 60, Saha et al 1990; 61, Saha et al 1996; 62, Sandage & Carlson 1982; 63, Sandage & Carlson 1985a; 64, Sandage & Carlson 1985b; 65, Sandage & Carlson 1988; 66, Schweitzer et al 1995; 67, Tolstoy et al 1995; 68, Wilson 1992a; 69, Caldwell et al 1988; 70, Demers & Irwin 1987; 71, deleted in proof; 72, Freedman 1992; 73, Elston & Silva 1992; 74, Kuhn et al 1996; 75, Light et al 1986; 76, Massey et al 1992; 77, Saha et al 1992a; 78, Aparicio et al 1997c; 80, Musella et al 1997; 81, van Agt 1973; 82, van Agt 1978; 83, Saha et al 1986; 84, Whitelock et al 1996; 85, Hodge & Wright 1978; 86, deleted in proof; 87, Minniti & Zijlstra 1996; 88, Walsh et al 1997; 89, Da Costa & Armandroff 1995; 90, Zijlstra & Walsh 1996; 91, Da Costa et al 1996; 92, Hodge 1973; 93, Battistini et al 1987; 94, Da Costa & Graham 1982; 95, Ferguson et al 1996; 96, Liller & Alcaino 1983; 97, Wilson et al 1996; 98, Jacoby & Lesser 1981; 99, Saha & Hoessel 1987. 100, Young & Lo 1997a; 101, Hodge 1976; 102, Gallagher & Hunter 1981; 103, Ford & Jenner 1976; 104, Ford et al 1978; 105, van Dokkum & Franx 1995; 106, Richer & Westerlund 1983; 107, Hodge 1966; 108, Eskridge 1988b; 109, Hunter et al 1993; 110, Carlson & Sandage 1990; 111, Freedman 1988b; 112, Hodge 1980; 113, Lequeux et al 1987; 114, van de Rydt et al 1991; 115, Maran et al 1984; 116, Danzinger et al 1978; 117, Tolstoy 1996; 118, Strobel et al 1991; 119, Deleted in proof; 120, Tolstoy et al 1998; 121, Hodge 1974; 122, Davidge 1993; 123, Whiting et al 1997; 124, Sarajedini et al 1997; 125, Mateo et al 1998d; 126, Sakai et al 1996; 127, Hunter & Gallagher 1990; 128, Deleted in proof; 129, Dohm-Palmer et al 1997; 130, Mighell & Rich 1996; 131, Hodge et al 1988; 132, Drissen et al 1993; 133, Dohm-Palmer et al 1998; 134, Harris et al 1997. 135, Mateo et al 1995b; 136, Mateo et al 1998a; 137, Cook 1987; 138, Killen & Dufour 1982; 139, Baade & Swope 1961; 140, van Agt 1978; 141, Saviane et al 1996; 142, Lavery et al 1996; 143, Azzopardi 1994; 144, Davidge & Nieto 1992.
 g-j The census of tracers of young populations: OB associations, Wolf-Rayet stars, HII regions, and discrete dust clouds.
 k References for the young population tracers (see footnote f).
 l-m The census of known intermediate-age and old-age population tracers: asymptotic giant branch (AGB) stars, planetary nebulae, and globular clusters.
 n References for the intermediate-age and old-age tracers (see footnote f).
 o The AGB census is for stars with MI leq - 4.4.
 p The AGB stars noted are principally C stars.
 q The numbers of planetary nebulae are reported by Ciardullo et al (1989); see that paper for the original sources.
 r Approximately 21 RR Lyr stars may be associated with Fornax cluster 1 (Smith et al 1996).
 s The Cepheid is most likely a W Vir or Pop II Cepheid (Light et al 1986).
 t Additional low-luminosity CH stars are also known on or near the AGB (Aaronson et al 1983).
 u The numbers of Cepheids are reported by Capaccioli et al (1992); see that paper for the original sources.

But perhaps most exciting of all is that as we stand on the threshold of detailed studies of dwarf galaxies in other groups (e.g. Côté 1995, Côté et al 1997, Caldwell et al 1998), the Local Group dwarfs will serve as a benchmark against which other systems can be compared. We know that complex star-formation histories are common in the Local Group. We know that both dIrr and early-type dwarfs contain interstellar material, which manifests itself in many different ways. We know that Local Group dwarfs are kinematically peculiar, whether dominated by DM or not. Do dwarfs in other groups behave the same way? How do they differ? How many of these tendencies are truly universal, and how many due to the specific environmental circumstances of individual groups? These questions will lead to insights that we cannot gain from studies of only the galaxies in the Local Group. It will be an exciting adventure and one that is sure to uncover as many surprises as the dwarfs of the Local Group already have.

ACKNOWLEDGEMENTS

I dedicate this paper to the memory of my father, Luis Ernesto Mateo, who taught me - and gave me the opportunity - to find my own way. I would like to thank the people who have helped materially with this paper: K Chiboucas, D Hurley-Keller, and K von Braun for carefully checking the references in most of the tables; Tina Cole for typing in hundreds of references and somehow managing to remain her cheerful self, and to A Aparicio, J Gallagher, P Hodge, and A Sandage for their comments on the original manuscript. It is also a pleasure to thank colleagues who have provided many stimulating discussions over the years that (through no fault of their own!) have led to some of the ideas in this paper: J Bregman, N Caldwell, C Carignan, C Chiosi, G Da Costa, S Demers, R Dohm-Palmer, K Freeman, C Gallart, E Grebel, P Harding, D Hunter, D Hurley-Keller, KY Lo, P Massey, H Morrison, E Olszewski, C Pryor, D Richstone, A Saha, E Skillman, and E Tolstoy. I am grateful to C Carignan for providing Figure 6 to me prior to publication. I particularly want to thank P Hodge and G Preston, both for the numerous pleasant discussions I have had with them about some of the topics in this review and for sharing their enthusiasm for astronomy. Finally, my heartfelt thanks to Nancy, Emilio, and Carmen for putting up with me while writing this review and for their encouragement through it all. Some of my research described in this paper has been supported, in part, by grants from the National Science Foundation and National Aeronautics and Space Administration.

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