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

“Resolutions to this problem generally involve the “missing baryons” either residing in a massive, hot halo (e.g. Maller & Bullock 2004; Fukugita & Peebles 2006) or being ejected completely from the system (e.g. Dekel & Silk 1986; Oppenheimer & Davé 2006).”

“…di†erent stages in the same evolutionary chain, with dIrrÏs either evolving through gas loss into dEÏs (e.g., Lin & Faber 1983 ; Kormendy 1985 ; Dekel & Silk 1986 ; Patterson & Thuan 1996) or evolving into BCDs as they undergo a starburst (e.g., Searle et al. 1973 ; Wirth & Gallagher 1983 ;…”

“Finally, feedback from supernova– generated winds is thought to be an essential part of shaping the mass–metallicity relation (Dekel & Silk 1986; Cole 1991), causing a downturn in the relative enrichment at low stellar masses by ejecting metals into the intergalactic medium (IGM).”

“The fact that galaxies in low-mass halos form stars very inefficiently is likely due to energy injection from supernovae (Dekel & Silk 1986).”

“Theory predicts that gas removal by supernova-driven winds should be more effective in lower mass systems, leading to a consequent suppression of the SFR and a low SFE (e.g. Dekel & Silk 1986; Efstathiou 2000).”

“In such galaxies, gas and metals are barely removed from the galaxies (e.g.Dekel & Silk 1986).”

“Within the well-accepted framework of hierarchical collapse, today’s dwarf galaxies are con- sidered to be the non-merged remnants of small-scale primordial density fluctuations in the early Universe (White & Rees 1978, Dekel & Silk 1986, Ikeuchi & Norman 1987).”

“This mechanism has been discussed extensively (e.g., Dekel & Silk 1986; De Young & Gallagher 1990).”

“Are the dwarfs observed today the leftover building blocks of large galaxies (White & Rees 1978, Dekel & Silk 1986)?”

“This might be because stellar feedback is considered to be less effective in massive SFGs as it does not inject enough energy (Dekel & Silk 1986).”

“Radiation and winds from young stars and supernovae, often globally referred to as stellar feedback, are an important ingredient in the formation of dwarf galaxies (e.g., Dekel & Silk 1986; Navarro et al. 1996; Mashchenko et al. 2006; Pontzen & Governato 2014).”

“…following standard definitions as tcool = 3kTμmp/2Λρ and tdyn = √ 3π/6Gρ, respectively. velocity also agrees with the theoretical expectations from Dekel & Silk (1986), who concluded that, only for systems with Vcir larger than ∼100 km s−1 are the cooling times of the diffuse and hot gas…”

“…(L-Z) relation is established through galactic winds – induced by supernova explosions – removing the interstellar medium (ISM) before it has been totally converted into stars (see the seminal work of Larson 1974; and also Tinsley & Larson 1979, Dekel & Silk 1986, Lynden-Bell 1992, among others).”

“Some have argued for supernovadriven (Couchman & Rees 1986, Dekel & Silk 1986) or ‘miniquasar’-driven (Haiman, Madau & Loeb 1999) winds.”

“…dwarf galaxies has led to the idea that, because of their rather shallow gravitational potential, supernova products and even the whole of the ISM may be easily ejected from the host dwarf systems, causing the contamination of the intracluster medium (Dekel & Silk 1986 ; De Young & Heckman 1994).”

“Therefore, a model for studying the enrichment of the ICM should take into account the contribution from the lowmass population of galaxies in the cluster (Dekel & Silk 1986).”

“…for some time (Silk 1977), but many di†erent have beenAnsa tze invoked as the suppressing mechanism, including supernova energy that ejects gas (Dekel & Silk 1986), reheating of the intergalactic medium that suppresses gas infall (Blanchard, Valls-Gabaud, & Mamon 1992 ; Bullock, Kravtsov, &…”

“(White & Rees 1978; Dekel & Silk 1986; White & Frenk 1991).”

“They are a major source of iron (e.g.,Matteucci & Greggio 1986; Tsujimoto et al. 1995; Thielemann et al. 1996) and inject energy into the interstellar medium (e.g.,Dekel & Silk 1986; Scannapieco et al. 2006).”

“Theoretical work has long shown that supernovae in lowmass galaxies should produce energetic outflows that heat and enrich their environments (Larson 1974; Dekel & Silk 1986; Vader 1986).”

“Simulations have shown that supernova feedback can halt star formation in dwarf galaxies by driving out gas (e.g. Dekel & Silk 1986; Stinson et al. 2007; Gonz´alez-Samaniego et al. 2014), however this ejected gas can cool and re-accrete, resulting in bursty star formation histories in isolated…”

“…Madau et al. 2001; Scannapieco et al. 2002; Cen et al. 2005) and are thought to play a crucial role in shaping the massmetallicity relation of galaxies (e.g. Larson 1974; Dekel & Silk 1986; Arimoto & Yoshii 1987; Gibson 1997; Kawata & Gibson 2003), and in heating the IGM (Ikeuchi & Ostriker 1986).”

“The shallow gravitational wells of the small haloes cannot hold onto their gas if the halo virial temperature is below Tvir ∼ 10 4 K (Dekel & Silk 1986, Shapiro et al. 2004, Iliev, Shapiro, & Raga 2005), while for larger haloes (104K ∼< Tvir ∼< 10 5 K) the gas accretion rate decreases, and the…”

“From a cosmological point of view, dwarfs would be the first galaxies ever formed, from which bigger structures would have formed via mergers (Blumenthal et al. 1985; Dekel & Silk 1986; Navarro, Frenk & White 1995; Moore et al. 1998).”

“They have been theoretically predicted to suppress and quench star formation (e.g. Dekel & Silk 1986, Barai et al. 2013, Muratov et al. 2015, Keller et al. 2016, Krumholz et al. 2017, Su et al. 2017), potentially enrich the intergalactic medium (IGM) (Oppenheimer et al. 2010), and may lead to the…”

“…can drive metal-enriched material out of the galactic plane, thus affecting the mass-metallicity relation between galaxies, the metallicity-radius relation within galaxies, and the enrichment of intracluster medium (e.g., Dekel & Silk 1986; Heckman, Lehnert, & Armus 1993 and references therein).”

“It has been argued (Dekel & Silk 1986; Arimoto & Yoshii 1987) that this results from the relative depth of the potential wells.”

“This required high efficiency of energy loading poses a severe challenge for the standard SN feedback scenario (e.g. Dekel & Silk 1986; White & Zaritsky 1992).”

“Many recent studies have shown the important role of dwarf galaxies in understanding how galaxies form and evolve in general (e.g. Dekel & Silk 1986, Ferguson & Binggeli 1994, Walter et al. 2007, Tolstoy et al. 2009).”

“…that a burst of star formation can disrupt and potentially blow out gas from the centre of a dwarf galaxy, inhibiting further star formation (e.g., Dekel & Silk 1986; Mac Low & Ferrara 1999), although it is not the only possible explanation for what is seen (cf. ram pressure stripping scenarios…”

“Low-metallicity galaxies may have been the first sites of star formation in the early universe (White & Rees 1978; Dekel & Silk 1986).”

“This corresponds to the case discussed in Dekel & Silk (1986).”

“…media are invoked to explain such properties as the galaxy stellar mass function (e.g., Bower et al. 2012), mass-metallicity relation (e.g., Dekel & Silk 1986; Tremonti et al. 2004), and chemical enrichment of the circumgalactic and intergalactic medium (CGM and IGM, e.g., Cowie et al.…”

“…(AGNs) produce photoionizing radiation, jets, and winds that can modulate star formation in the host galaxy and accretion by the SMBH (Fabian 2012; Gaspari & Sadowski 2017) via feedback processes, which must be considered in addition to those seen in rapid starbursts (Dekel & Silk 1986; Silk 1997).”

“However, it disfavors models that prevent star formation in low-mass galaxies through significant baryonic mass loss (Dekel & Silk 1986; Cole et al. 2000;Mori & Burkert 2000; Bullock et al. 2000; Benson et al. 2003; Dekel & Woo 2003; Tremonti et al. 2004; Croton et al. 2006).”

“This limit is an important parameter in modeling dwarf galaxy evolution in particular (Dekel & Silk 1986), as it constrains the amount of energy and matter produced during the evolution of a given stellar population.”

“Dwarf starburst galaxies can therefore play an important role in enriching their surroundings with heavy elements produced during starburst episodes (Dekel & Silk 1986; Ferrara & Tolstoy 2000).”

“Internal physical processes like supernova feedback (Dekel & Silk, 1986) or the dynamical response to gas loss (Yoshii & Arimoto, 1987) have a stronger impact on dwarf galaxies than on giants, making dwarfs valuable test objects for galaxy formation models (Janz & Lisker, 2008, 2009).”

“The standard explanation for this correlation being self-enrichment in the presence of galactic winds which are limited by gravitational potential gradients (Dekel & Silk 1986), Djorgovski & Meylan (1994) conclude that globular clusters cannot be self-enriched systems.”

“Many studies favor supernova driven winds for the inability of a low-mass galaxy to retain its newly synthesized heavy elements, resulting in a lower effective yield with decreasing mass (e.g., Dekel & Silk 1986).”

“…explosion energy of just a few supernovae SNe) many authors speculated that a high SF rate in a DG would create a galactic wind and thus produce a transition from a dwarf irregular (dIrr) to a dwarf spheroidal (dSph) or dwarf elliptical (dE; see, e.g., Larson 1974; Vader 1986; Dekel & Silk 1986).”

“…galactic outflows would be more efficient at expelling metal-enriched gas in low-mass galaxies than in massive ones (e.g. Larson 1974; Dekel & Silk 1986; Tremonti et al. 2004; De Lucia et al. 2004a; Kobayashi, Springel & White 2007; Finlator & Davé 2008; Arimoto & Yoshii 1987).”

“…mechanisms of energy feedback into the interstellar medium are proposed in order to regulate the subsequent star formation or even to change the structure of the galaxy (Dekel & Silk 1986), a scenario supported by several observational evidences (e.g. de Rijcke et al. 2005, and references therein).”

“Future technical improvements in the observations of the GC and of the Milky Way dwarf galaxies may open the possibility of using the method proposed here to investigate the nature of DM.”

“However, if accreted satellites have no luminous stellar component (White & Rees (1978) Dekel & Silk (1986)) their presence could be hidden in stellar density maps.”

“On the largest scales, dwarfs have been invoked as a test of possible biasing between the distribution of dark matter and that of bright galaxies (e.g., Dekel & Silk 1986) and as possible sites of extremely high mass-to-light ratios (e.g., Lake, Schommer, & van Gorkom 1990).”

“It is believed that below the critical mass ( M ∼ 10 12 M ⊙ ), the SNe feedback dominates the feedback whereas, the black hole feedback takes over at higher masses (Silk 1977; Dekel & Silk 1986; Silk & Mamon 2012).”

“The highly simplified physical explanation is that at low masses, supernova energy is sufficient to unbind a sizeable fraction of the gas (Dekel & Silk 1986), but at high masses, additional contributions from momentum input are necessary (Murray et al. 2010; Hopkins et al. 2012).”

“Several authors suggested that the ISM of dSph systems could be entirely removed by SNe explosions (Dekel & Silk (1986); Hensler et al. (2004); Mori et al. (2002, 2004, 1997); Murakami & Babul (1999); Lanfranchi & Matteucci (2004); Mac Low & Ferrara (1999)).”

“The most widely used feedback is SN-driven outflows (Dekel & Silk 1986; Larson 1974), and such flows are detected in many observations at low and high redshifts (e.g., Martin 1999; Strickland et al. 2000; Rupke et al. 2005; Steidel et al. 2010; Newman et al. 2012).”

“…at early epochs that suppresses further globular cluster and star formation (Beasley et al. 2002; Santos 2003; Bekki 2005; Moore et al. 2005), supernova feedback and mass loss via winds (Durrell et al. 1996; Dekel & Silk 1986) and cold accretion flows (Keres et al. 2005; Dekel & Birnboim 2005).”

“Any systematic concentration of gas in the immediate vicinity of star formation raises the possibility that enriched outÑows from dwarf galaxies may be less likely than previously believed (Dekel & Silk 1986).”

“…has revealed asymmetric and redward shifted Ly-alpha emission relative to metal absorption lines, which is claimed to imply this galaxy is suffering an outflow of metal enriched gas (Franx et al. 1997), similar to local dwarf starburst galaxies (Dekel & Silk 1986, Heckman, Armus & Miley 1990).”

“It is widely recognized that baryonic feedback (FB) processes play vital roles in the formation and evolution of galaxies in the ΛCDM universe (e.g., Larson 1974; Blumenthal et al. 1984; Dekel & Silk 1986).”

“We recover the classical result from early galaxy formation models of overcooling of baryons into the center of the dark matter halo and the overabundant production of stars (White & Rees 1978; Dekel & Silk 1986; White & Frenk 1991).”

“These typically involve the prevention of gas falling into small dark matter halos (Efstathiou 1992), the removal of gas via supernova winds from the first generation of stars (Dekel and Silk 1986) or the ‘squelching’ of dwarf galaxy formation by ionising photons (Tully et al. 2002).”

“There is also a theoretical expectation that similar winds may have occurred in high-redshift dwarf galaxies, because the small binding energies of these systems would allow a wind to escape fairly easily (Dekel & Silk 1986; Madau et al. 2001; Bromm et al. 2003; Furlanetto & Loeb 2003).”

“Much recent attention has been paid to understanding the gas evolution and first generations of stars within such systems (e.g., Dekel & Silk 1986; Katz et al. 1996; Quinn et al. 1986; Tegmark et al. 1997; Weinberg et al. 1997; Mac Low & Ferrara 1999; SommerLarsen et al. 1999, 2003; Fragile et al.…”

“Many mechanisms have been proposed for driving galactic winds, including hot flow heated and driven by supernova explosions (Larson 1974; Dekel & Silk 1986; Chevalier & Clegg 1985; Strickland & Heckman 2009), radiation pressure by absorption in spectral lines or the continuum absorption and…”