The Progenitors of Dwarf Spheroidal Galaxies

By E. Grebel, J. Gallagher III, Daniel Harbeck. 2002

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The gas-deficient dwarf spheroidal (dSph) galaxies present an evolutionary puzzle that we explore in 40 early-type and late-type dwarfs in the Local Group and nearby field. Although dSph's experienced star formation over extended time spans in their youths, today all but one are completely free of detectable interstellar material, even in the Fornax dSph, where stars formed in the last 100 Myr. Combining photometric and spectroscopic stellar metallicity estimates for red giant branches with high-sensitivity H I 21 cm line data from the literature, we show that the well-established offset in luminosity-metallicity relationships for dSph's and dwarf irregular (dIrr) galaxies exists also when confining the comparison to their old stellar populations: dSph's have higher mean stellar metallicities for a fixed optical luminosity. Evidently star formation in younger dSph's was more vigorous than in the youthful dIrr's, leading to more efficient enrichment. Dwarf galaxies, whose locus in the luminosity-metallicity diagram is consistent with that of dSph's, even when baryonic luminosities are considered, are the "transition-type dwarfs" Phoenix, DDO 210, LGS 3, Antlia, and KKR 25. These dwarfs have mixed dIrr/dSph morphologies, low stellar masses, low angular momentum, and H I contents of at most a few 106 M⊙. Unlike dIrr's many transition-type dwarfs would closely resemble dSph's if their gas were removed, as required to become a dSph; they are likely dSph progenitors. As gas removal is the key factor for such a transition, we consider the empirical evidence in favor and against various gas removal processes. We suggest that internal gas removal mechanisms are inadequate and favor ram-pressure stripping to clean the bulk of interstellar matter from galaxies to make dSph's. A combination of initial conditions and environment seems to support the formation of dSph's: nearby dSph's appear to form from small galaxies with active early star formation, whose evolution halts due to externally induced gas loss. Transition-type dwarfs, then, are dSph's that kept their interstellar medium and therefore should replace dSph's in isolated locations where stripping is ineffective.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/70487057b372e271c0a7e5e4e27311027a264c94

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Citations in the corpus

THE DUAL ORIGIN OF STELLAR HALOS (2009, background): “Figure 3 shows the luminosity function of the satellites in MW1med and MW1thermal, as well as the observed luminosity function of Milky Way dwarfs, from Grebel et al. (2003).”
A REVISED PARALLEL-SEQUENCE MORPHOLOGICAL CLASSIFICATION OF GALAXIES: STRUCTURE AND FORMATION OF S0 AND SPHEROIDAL GALAXIES (2011, background): “…observations and theoretical developments both suggest that ram-pressure stripping is more effective than we have thought (Mori & Burkert 2000; Quilis et al. 2000; Grebel et al. 2003; Roediger & Hensler 2005; Tonnesen et al. 2007, 2008, 2009, 2010; Boselli et al. 2008; van Gorkom & Kenney 2011).”
Mass loss from dwarf spheroidal galaxies: the origins of shallow dark matter cores and exponential surface brightness profiles (2004, background): “Many mechanisms have been proposed to drive gas mass loss from dwarf galaxies, including ram pressure stripping (Einasto et al. 1974; Grebel et al. 2003), supernovae explosions (Larson 1974; Dekel & Silk 1986; Efstathiou 2000; Dekel & Woo 2003); photoevaporation (Quinn, Katz & Efstathiou 1996;…”
Complexity on Small Scales: The Metallicity Distribution of the Carina Dwarf Spheroidal Galaxy (2005, background): “This offset suggests that star formation in young dSphs was more vigorous than in young dIrrs (Grebel et al. 2003).”
The Great disk of Milky Way satellites and cosmological sub-structures (2004, background): “The different chemical enrichment and star-formation histories of the various dwarves (e.g. Ikuta & Arimoto 2002; Grebel et al. 2003) may in this case be a result of their different initial masses, which will have been significantly larger than their present-day baryonic masses (Kroupa 1997) and…”
THE STAR FORMATION HISTORIES OF LOCAL GROUP DWARF GALAXIES. I. HUBBLE SPACE TELESCOPE/WIDE FIELD PLANETARY CAMERA 2 OBSERVATIONS (2014, background): “This conclusion would appear to support claims that dwarfs with present day morphologies did not share a similar progenitor, as suggested in Grebel et al. (2003).”
The Tumultuous Lives of Galactic Dwarfs and the Missing Satellites Problem (2004, methodology): “For the observed galaxies, we combined dwarf spheroidal, transition type, and dwarf elliptical galaxies in one broad class of spheroidal systems, using Table 1 of Grebel et al. (2003).”
Strong Emission Line H II Galaxies in the Sloan Digital Sky Survey. I. Catalog of DR1 Objects with Oxygen Abundances from Te Measurements (2004, background): “These can be related to both the global properties of galaxies (e.g., Dalcanton et al. 1997; Grebel et al. 2003) and the membership of galaxies in various elements of large-scale structure (e.g., Popescu et al. 1996; Grogin & Geller 2000; Pustilnik et al. 2002b; Vilchez & Iglesias-Páramo 2003; Lee…”
The Origin of Dwarf Ellipticals in the Virgo Cluster (2008, background): “This luminosity difference for the same metallicity corresponds well to that observed by Grebel et al. (2003) between the star forming and quiescent dwarf galaxy populations.”
Scaling relations and the fundamental line of the local group dwarf galaxies (2008, background): “…(2000); (2) Baggett et al. (1998); (3) Caldwell (1999); (4) Corbelli & Salucci (2000); (5) Côté et al. (1999); (6) Engargiola et al. (2003); (7) Grebel et al. (2003); (8) Grebel & Guhathakurta (1999); (9) Hopp et al. (1999); (10) Jacobsson (1970); (11) Larsen et al. (2000); (12) Lee et al.…”
The importance of tides for the Local Group dwarf spheroidals (2005, background): “Since the dSph galaxies lie, in general, closer to their host galaxy (there are notable exceptions - see e.g. Grebel et al. 2003) it has often been argued that the tidal field of the host galaxy has an important role to play in the formation and evolution of these galaxies.”
THE ACS NEARBY GALAXY SURVEY TREASURY. VIII. THE GLOBAL STAR FORMATION HISTORIES OF 60 DWARF GALAXIES IN THE LOCAL VOLUME (2011, background): “…the amplitude of the difference is significantly smaller than typical models, which assume that dSphs are dominated by ancient stellar populations and dIs are consistent with constant SF over their 18 Weisz et al. lifetimes (e.g., Binggeli 1994; Skillman & Bender 1995; Grebel et al. 2003).”
Virgo Cluster Early-Type Dwarf Galaxies with the Sloan Digital Sky Survey. II. Early-Type Dwarfs with Central Star Formation (2006, background): “Similarly, Grebel et al. (2003) argued for Local Group dwarfs that the so-called dIrr/dSph transition types are plausible progenitors of dSphs, while dIrrs themselves seem less likely.”
THE UNIVERSAL STELLAR MASS–STELLAR METALLICITY RELATION FOR DWARF GALAXIES (2013, background): “This relation for dSphs is consistent with the MZR determined from photometric metallicities of stars in more massive dEs (Grebel et al. 2003; Woo et al. 2008).”