The origin of dwarf galaxies, cold dark matter, and biased galaxy formation

“In this respect, the smallest dwarf galaxies present the ideal test case, because they can be expected to be the most susceptible to the effects of SN feedback due to their shallow potential wells (Larson 1974; Dekel & Silk 1986).”

“Indeed, these galactic outflows are observed in almost every star-forming galaxy (SFG) (Veilleux et al. 2005, for a review) and are likely to enrich the intergalactic medium (e.g., Dekel & Silk 1986; Aguirre et al. 2001; Oppenheimer & Davé 2006).”

“CDM models predict a large population of low-mass halos inside the voids (Dekel & Silk 1986; Hoffman et al. 1992).”

“Systematically lower md values for low mass galaxies are a plausible signature of more efficient supernova feedback in shallow gravitational potential wells (Dekel & Silk 1986) or in galaxies that lack a confining envelope of shock-heated gas Keres et al. (2004).”

“…& Efstathiou 1996; Bullock, Kravtsov, & Weinberg 2000; Benson et al. 2002; Somerville 2002; Okamoto, Gao, & Theuns 2008; Okamoto & Frenk 2009; Koposov et al. 2009) and in larger subhaloes through energetic supernovae (SNe) feedback (e.g., Dekel & Silk 1986; Dekel & Woo 2003; Governato et al. 2007).”

“We adopt β = 2.0 and Vout = 110 km s−1 in our calculations (Dekel & Silk 1986).”

“This is a consequence of the ansatz (Dekel & Silk 1986) for cold dark matter dominated haloes that provides the basis for feedback in all semianalytical galaxy-formation modelling until now.”

“Thus, feedback mechanisms at early times have historically been invoked to prevent overcooling with moderate success (Dekel & Silk 1986; Sommer-Larsen et al. 1999; Thacker & Couchman 2000, 2001; Sommer-Larsen et al. 2003; Robertson et al. 2004; Okamoto et al. 2005; D’Onghia et al. 2006; Kereš et…”

“…galaxy formation and evolution have variously predicted that the voids contain “failed galaxies” identified as diffuse dwarfs and Malin 1-type giants (Dekel & Silk 1986, Hoffman, Silk, & Wyse 1992), or galaxies with the same morphological mix as higher-density regions outside clusters (Balland,…”

“The lower mass, and hence likely fainter, elliptical galaxies have lower escape speeds and suffer enhanced loss of metal-rich supernova ejecta (e.g., Dekel & Silk 1986).”

“Dwarf galaxies could be formed through the same physical process formation of giant galaxies; i.e., gravitational collapse of protogalactic gas clouds (Dekel & Silk 1986; White & Frenk 1991; Frenk et al. 1996; Kauffmann, Nusser & Steinmetz 1997).”

“The main mechanisms so far proposed include an energy feedback from supernovae that prevents the collapse of a forming galaxy (Dekel & Silk 1986; Lacey & Silk 1991) and a photoionization by ultraviolet background radiation that keeps the gas hot and unable to collapse (Dekel & Rees 1987; Efstathiou…”

“If dEs do indeed follow a shallower scaling relation α, then ∇ eϒ should increase again at low M∗ (cf. Dekel & Silk 1986), with a minimum occurring at log M ∗/(h−1 Mo) ∼ 10.2.”

“A detailed analysis of their internal structure may provide important clues about the formation, structure, and evolution of normal galaxies (Einasto et al. 1974 ; Gerola, Carnevali, & Salpeter 1983 ; Lin & Faber 1983 ; Dekel & Silk 1986 ; Babul & Ferguson 1996 ; Kepner, Babul, & Spergel 1997).”

“The hypothetical role of metal-enriched galactic winds has been discussed extensively (Mathews & Baker 1971; Dekel & Silk 1986; Vader 1987; De Young & Gallagher 1990).”

“…energy and kinetic energy generated in D-type I-front play a key role in star formation in low-mass halos, which are easily affected due to their shallow potential well (e.g. Dekel & Silk 1986; Haehnelt 1995; Bromm & Loeb 2003; Whalen et al. 2004; Kitayama et al. 2004; Kitayama & Yoshida 2005).”

“…especially from supernovae, is assumed to impact the low end of the observational stellar luminosity function, by influencing star formation (e.g. Dekel & Silk 1986; Mac Low & Klessen 2004; McKee & Ostriker 2007) driving turbulence (e.g. Joung & Mac Low 2006; Agertz et al. 2009; Tamburro et al.…”

“…energy back into the surrounding gas, reheating it to suppress further star formation, before radiative cooling of this heated gas is able to kick-start star formation once again (e.g. Larson 1974; Dekel & Silk 1986; Katz, Weinberg & Hernquist 1996; Somerville & Primack 1999; Cole et al. 2000).”

“For example, the peaks-bias paradigm of galaxy formation in a Ñat, cold dark matter universe (Dekel & Silk 1986, Ho†man, Silk, & Wyse 1992) predicts that the voids should be populated with ““ failed galaxies,ÏÏ identiÐed as di†use dwarfs, and that the 3 p massive galaxies in voids should have…”

“Galactic winds help limit the efficiency with which galaxies turn gas into stars by expelling material from the ISM and by halting gas inflow into galaxies (e.g., Dekel & Silk 1986; Springel & Hernquist 2003; Faucher-Giguère et al. 2011).”

“Additions to the theory, such as supernovae driven winds (Dekel and Silk, 1986) or the influence of a reheated intergalactic medium (Efstathiou, 1992) have been used to suppress dwarf galaxy formation globally.”

“…1994; Friedli & Benz 1993, 1995) or triggered by superwind shocks created by a combination of supernovae and winds from massive stars (e.g., De Young 1978; Dekel & Silk 1986; Mathews 1989; Heckman et al. 1990), but at high redshift, galaxy mergers and interactions should be the most common cause.”

“The importance of mass loss in determining the mass-metallicity relation in dwarf galaxies has already been ascertained (Dekel & Silk 1986).”

“…to the kinetic energy injected by supernova ejecta and by stellar winds into the ISM), in low mass galaxies residing in less massive dark matter halos, because it is easier for gas to escape from their shallower gravitational wells (Dekel & Silk 1986; Springel & Hernquist 2003; Davé et al. 2011b).”

“Therefore, it is likely to be a critically important factor driving the evolution of low mass galaxies (e.g., Dekel & Silk 1986; Mac Low & Ferrara 1999; Ferrara & Tolstoy 2000; Salvadori et al. 2008) like the Carina dSph, with Mtot = 6.1 ± 2.3 × 106 M within the half radius 241 ± 23 kpc (Walker et…”

“This can be most easily understood in terms that are consistent with Figure 14, if most of the metal enrichment of the Ly forest is due to dwarf galaxies (Dekel & Silk 1986; Mac Low & Ferrara 1999; Madau et al. 2001), where gas retainment is more difficult and thus metal recycling is limited.”

“Such feedback mechanisms may have strong influence on the evolution of dwarf galaxies (Dekel & Silk 1986; Marconi, Matteucci & Tosi 1994), although the exact details of the process are still uncertain and depend on the nature/geometry of the galaxy (De Young & Heckman 1994; Mac Low & Ferrara 1999).”

“…1992; Thoul & Weinberg 1996; Somerville 2002; Gnedin 2000; Hoeft et al. 2006), feedback from supernova explosions (e.g., White & Rees 1978; Dekel & Silk 1986) and active galactic nuclei (AGNs; e.g., Tabor & Binney 1993; Ciotti & Ostriker 1997; Hopkins et al. 2006, and references therein;…”

“The maximum outflow condition thus implies thatmwind = (vSN/vcirc)2m̃stars (Dekel & Silk 1986), wherev2SN is a proportionality constant, the value of which is to be determined by fitting the galaxy mass function and is physically related to the supernova energy that goes into wind kinetic energy.”

“…hierarchical clustering scenarios for galaxy formation, such as cold dark matter- dominated cosmologies (White & Rees 1978; Blumenthal et al. 1984; Dekel & Silk 1986), dwarf galaxies should have formed prior to the epoch of giant galaxy formation and would be the building blocks of larger…”

“Perhaps haloes were able to form a few stars initially, but the baryonic components of all haloes below some critical mass were subsequently destroyed by supernova feedback (e.g. Larson 1974; Dekel & Silk 1986; Ferrara & Tolstoy 2000).”

“G A ] object but in which internal processes, like star-formation and feedback, caused some to retain more gas than others (Dekel & Silk 1986; de Rijcke et al. 2005).”

“…the effects of supernova feedback in suppressing accretion on to the central black hole at lower masses pre-compaction, especially once the halo potential well becomes deeper than the critical value for supernova feedback (V > 100 km s−1; Dekel & Silk 1986), corresponding to Mvir ∼ 10 12 M⊙.”

“Such feedback has long been recognized as a primary mechanism through which galaxies regulate their star formation (e.g. White & Rees 1978; Dekel & Silk 1986; White & Frenk 1991; Hopkins et al. 2012; Somerville & Davé 2015).”

“The suppression of star formation in feedback models relative to the no wind case is actually larger at larger masses, counterintuitive to the notion that feedback preferentially affects small galaxies (Dekel & Silk 1986); this reflects the hierarchichal assembly of large galaxies from smaller ones.”

“The assumption of no major star formation events after the current burst is consistent with energetic arguments that any remaining gas would be blown away in supernova-driven galactic winds (Dekel & Silk 1986; Guzmán et al. 1996).”

“G A ] 1 3 energy input from (several) supernovae (SNe) (Dekel & Silk 1986; Efstathiou 2000; Creasey et al. 2013; Martizzi et al. 2016; Girichidis et al. 2016a).”

“…stars (≈10 per cent, e.g. Fukugita, Hogan & Peebles 1998), the flattening of the faint-end slope of the luminosity function (e.g. White & Rees 1978; Dekel & Silk 1986; Benson et al. 2003), the formation of exponential discs ⋆ E-mail: s.r.mcalpine@durham.ac.uk (e.g. Binney, Gerhard & Silk 2001;…”

“…intracluster medium with metals, the occurrence of metallicity gradients within individual galaxies (e.g. Heckman et al. 2000), the properties of dwarf galaxies (Dekel & Silk 1986) and even to provide a reservoir of hot gas for re-accretion by galaxies at lower redshifts (Oppenheimer et al. 2010).”

“…says that star formation at the threshold density can regu- late or stop itself in a disk (see, e.g., Franco & Shore 1984) or dwarf galaxy (see, e.g., Dekel & Silk 1986), where the gaseous velocity dispersion is low, km s~1, but itagas D 7cannot regulate or stop itself in a young galactic bulge or…”

“…thought to be the dominant factor producing the variety of dSph SFHs. Differences in the level of tidal distortion, mechanical feedback and gas infall experienced by each system are cited, however the precise nature of these local effects is uncertain (e.g. Dekel & Silk 1986; Mayer et al. 2006).”

“However, LSBs are not exclusively low mass (see Table 1), and supernova winds are not expected to be effective at ejecting baryons from systems with Vflat & 100 km s−1 (e.g., Dekel & Silk 1986).”

“(15) On the other hand if the outflow is driven by kinetic energy from supernovae and stellar winds (Chevalier & Clegg 1985; Dekel & Silk 1986; Silk & Rees 1998; Murray et al. 2005), the mass loading factor is described by λenergy = 2 effηSNESN v2w = ( 1000 km s−1 vw )2 (16) where ESN = 10 51erg is…”

“In their model, feedback from star formation is the main driver for the decrease of the star forma- tion efficiency in low-mass galaxies (e.g., Dekel & Silk 1986; Bower et al. 2012; Hopkins et al. 2012), consistent with the decreasing in log(M∗/Mhalo) for star-forming galaxies below the pivot mass…”

“As shown by Dekel & Silk (1986) and White & Frenk (1991), the total amount of energy released by supernovae can be significantly larger than the binding energy of the gas in low-mass haloes.”

“The first of these explores the idea that the dwarfs’ luminosity is monotonically related to their current mass (e.g. Dekel & Silk 1986).”

“As Dekel & Silk (1986) conclude, “The dwarfs (including the so-called ‘irregulars’) are actually the common, typical galaxies, while the ‘normal’ galaxies are the special cases.””

“…would be very unlikely to form quasars, because even a small fraction of their baryons turning into stars should provide sufficient energy (via ionization, stellar winds, or supernovae) to expel the remaining gas from the shallow potential well (e.g., Couchman & Rees 1986; Dekel & Silk 1986).”

“…might be dwarf galaxies that formed in isolation or at least in a lessdense environment and progressively fall into the cluster potential causing a gradual decrease in the star forming efficiency until it is halted (e.g. Dekel & Silk 1986; Mac Low & Ferrara 1999; Sawala et al. 2010; Mayer 2010).”

“…(<1 Gyr) of the star formation, and several authors believe that the ISM of these systems may be completely removed by violent SNe explosions (Dekel & Silk 1986; Mori et al. 1997; Murakami & Babul 1999; Mori, Ferrara & Madau 2002; Hensler, Theis & Gallagher 2004; Mori, Umemura & Ferrara…”

“…of star formation in more massive galaxies (e.g. Ferreras & Silk 2001), to a younger age for less massive galaxies (e.g. Boissier et al. 2001), to a more important mass loss reducing the effective yield in less massive galaxies (e.g. Dekel & Silk 1986) or to some combination of these factors.”

“These effects are expected to be smaller for small-mass halos, where the baryons do not cool efficiently and can be expelled by supernova feedback (Dekel & Silk 1986).”

“This occurs via radiation pressure, stellar winds, photoionization, and supernovae (Dekel & Silk 1986; Mac Low & Ferrara 1999; Murray et al. 2011).”

“In order to reproduce the faint end of the luminosity function, the models typically invoke supernova feedback to expel gas from low mass haloes (e.g., Larson 1974; White & Rees 1978; Dekel & Silk 1986).”

“Feedback mechanisms like supernovae (SN) or galactic winds heating have been advocated in order to suppress gas cooling and star formation (Dekel & Silk 1986).”

“The conventional understanding of supernova feedback also suggests that it will be more effective in low-mass systems because gas is more easily driven out of shallow potential wells (Dekel & Silk 1986).”

“…(SNe) is an important component of understanding the interstellar medium (ISM), galactic winds, and galactic evolution (e.g. McKee & Ostriker 1977; Dekel & Silk 1986; Murray, Quataert & Thompson 2005; Jenkins & Tripp 2011; Kim, Kim & Ostriker 2011; Ostriker & Shetty 2011; Hopkins, Quataert &…”

“Once the first stars are formed, mechanisms of energy feedback into the interstellar medium have been proposed in order to regulate the subsequent star formation or even change the structure of the galaxies (Dekel & Silk 1986).”

“…such as the ISM metallicities and the mass-metallicity relation, total stellar masses, discrepancies in the galaxy luminosity function compared to expectations from cold-dark matter cosmology, and IGM enrichment (e.g., Dekel & Silk 1986; Springel & Hernquist 2003; Oppenheimer & Davé 2006).”

“osions through the evolutionary history of a galaxy can distort the distribution of dark matter in the halo due to the effect of the ejected expanding gas on the gravitational potential of the galaxy [56,57]. If dark matter halos strongly depend on the individual history of each galaxy, the assumption of universality…”

“Since the seminal work of Dekel & Silk (1986) the extent to which mass loss affects the evolution of low-mass galaxies has attracted much attention.”

“…possible evolutionary links between BCGs and other types of galaxies have been widely discussed in the litterature (see e.g. Davies and Phillips 1988; Dekel and Silk 1986; Lin and Faber 1983; Thuan 1992, Babul and Rees 1992; Papaderos et al. 1996; Bergvall et al. 1998,1999; Kunth and Östlin 2000).”

“We compute the critical halo mass for gas expulsion out of the halo by the AGN outflow, following the example of Dekel & Silk (1986) for SNe.”

“Late supernova-driven “superwinds” from massive galaxies (e.g., Aguirre et al. 2001; Adelberger et al. 2003), early outflows from dwarf galaxies (e.g., Dekel & Silk 1986; MacLow & Ferrara 1999; Madau, Ferrara, & Rees 2001; Mori, Ferrara, & Madau 2002; Scannapieco, Ferrara, & Madau 2002; Furlanetto…”

“These physical mechanisms can be broadly split into two categories; global mechanisms that affect all dwarf galaxies regardless of their location, such as supernovae feedback (Dekel & Silk 1986), and environmentally dependent mechanisms.”

“The stars formed will likely blow away most of the remaining gas by supernova explosions (Dekel & Silk 1986; Mac Low & Ferrara 1999).”

“For example, the supernova winds that some use to explain the suppression of star formation in dwarf galaxies at high redshift (Dekel & Silk 1986) has also been proposed as a possible mechanism for the truncation of metal-poor GC formation at early times (Beasley et al. 2002).”

“…if the undiscovered galactic baryons exist primarily in hot gaseous halos around normal galaxies (MB04; Fukugita & Peebles 2006; Sommer-Larsen 2006) or if they have been mostly expelled as a result of energetic blow-out (e.g., Dekel & Silk 1986; Oppenheimer & Davé 2006).”

“At the low mass end (Mh < 1012M ), stellar feedback in the form of energy and momentum injection from radiation pressure, stellar winds, and supernova explosions is believed to be responsible for the suppression of star formation (Dekel & Silk 1986; Efstathiou 2000).”