Contraction of dark matter galactic halos due to baryonic infall

“Other authors studied adiabatic contraction of DM haloes [270,271]5, that conversely produces a steepening of the density profiles.”

“The baryons, which are condensed in the center, influence the shape of DM halo gravitationally, increasing the central DM density [137, 138].”

“A simple treatment of this phenomenon can be given by assuming the so-called ‘‘ adiabatic approximation ’’ (Blumenthal et al. 1986; see alsoMo,Mao, &White 1998).”

“During central gaseous collapses in halos, the gravitational potential in the inner ∼50 pc becomes baryon dom- inated where the baryon density is greater than the DM density, leading to a contraction of the DM inner halo (Blumenthal et al. 1986; Gnedin et al. 2004).”

“They assume that UCDs are hyper-massive star clusters, i.e. that their stellar population formed 17Adiabatic contraction (Blumenthal et al. 1986) in UCDs may however alleviate this problem but unlikely sufficiently so (Murray 2009).”

“The response of the dark matter profile to the presence of these cooling baryons is often modeled via adiabatic contraction (AC) (see, e.g., Blumenthal et al. 1986; Gnedin et al. 2004).”

“Under a rather restrictive set of assumptions, the adiabatic theorem leads to the following simple relation: Mbaryon(r)þMdm r ¼ Mhalo(ri)ri ð18Þ (Young 1980; Blumenthal et al. 1986; Flores et al. 1993).”

“We treat this adiabatic contraction of the dark halo following the procedure in Blumenthal et al. (1986) and Flores et al. (1993).”

“th N-body simulations using an NFW profile Xue et al. (2008) find MR<60 kpc = 4.0 ±0.7 ·1011M⊙, (5) which corresponds to Mtot = 1.0+0.3 −0.2 · 10 12 M ⊙. To get this total mass adiabatic contraction(Blumenthal et al. 1986) was allowed in whichcase the concentrationparameterwas takenas a freeparameter in the fit. This…”

“…based on the initial angular momentum of the gas and the halo profile, assuming that angular momentum is conserved and that the self-gravity of the collapsing baryons causes contraction of the matter in the inner part of the halo (Blumenthal et al. 1986; Flores et al. 1993; Mo, Mao & White 1998).”

“This effect is known as adiabatic contraction (AC, Blumenthal et al. 1986, Gnedin et al. 2004, Gnedin 2005, Sellwood & McGaugh 2005) and has been studied with analytic models and simulations.”

“This process is typically modeled assuming adiabatic contraction (AC) of the DM particle orbits (e.g., Blumenthal et al. 1986; Gnedin et al. 2004).”

“…based on the initial angular momentum of the gas and the halo profile, assuming that angular momentum is conserved and that the self-gravity of the collapsing baryons causes contraction of the matter in the inner part of the halo (Blumenthal et al. 1986; Flores et al. 1993; Mo, Mao & White 1998).”

“In the context of adiabatic contraction (AC) models (see, e.g., Blumenthal et al. 1986; Mo, Mao, & White 1998), the initial slope ( i) of the dark matter halo, i.e., before baryons assembled in the dark matter potential well, is in general expected to be shallower than the observed dark matter…”

“…has become broadly accepted in recent years that baryonic processes can alter the distributions of dark matter within halos, potentially steepening (Blumenthal et al. 1986; Gnedin & Zhao 2002; Gnedin et al. 2011) or flattening (Navarro et al. 1996; Read & Gilmore 2005; Mashchenko et al.…”

“Despite its simplicity, and the crude approximation on which it is based, early N-body work (e.g., Barnes & White, 1984; Blumenthal et al., 1986; Jesseit et al., 2002) found reasonable agreement between eq.”

“2It should be noted that the inferences from the shape of the HI warp are based on kinematic distance estimates that are known to be severely biased by up to a factor of two (Reid et al. 2014). as formulated by Blumenthal et al. (1986).”

“as argued on theoretical grounds [61] and observed in simulations (e.”

“In particular, the cooling and infall of baryons could – by a mechanism known as adiabatic contraction – lead to a steepening of the inner DM profile [84–86].”

“We include the effects of baryonic dissipation via the adiabatic contraction model of Blumenthal et al. (1986).”

“…to radiative dissipation from the baryons that depends on the mass of stars formed in the galaxy (e.g., the adiabatic contraction, or AC, models of Blumenthal et al. 1986; Gnedin et al. 2004, hereafter B86 and G04) or dynamical friction may counterbalance this effect (Abadi et al. 2009) and could…”

“We define Vrms as the one-dimensional velocity dispersion of the cluster, and assume that the angular momentum of the inflowing gas is negligible, such that the adiabatic invariant MVrmsRh of the star cluster is preserved, while M increases as the result of accretion (Blumenthal et al. 1986).”

“5 and σs, which is expected to be affected by baryon dissipation and the response of the dark halo to it (e.g., Blumenthal et al. 1986), neither of which are completely understood.”

“If the central accumulation of the baryons occurs on a longer time scale than the local dynamical time, the dissipationless dark matter halo will contract obeying adiabatic invariance (Blumenthal et al. 1986).”

“Since it is commonly assumed that the addition of a 1 2 baryonic component would cause the dark matter to adiabatically contract (Blumenthal et al. 1986) thereby exacerbating the observed discrepancy, the complications caused by the baryonic component are usually dismissed.”

“[23, 24] assumed shells of DM to contract due to the presence of the central galaxy while conserving angular momentum, i.”

“We have done this using the usual assumptions (Blumenthal et al. 1986; Flores et al. 1993); the system is treated as being spherically symmetric.”

“…based on the initial angular momentum of the gas and the halo profile, assuming that angular momentum is conserved and that the self-gravity of the collapsing baryons causes contraction of the matter in the inner part of the halo (Blumenthal et al. 1986; Flores et al. 1993; Mo et al. 1998).”

“The DM adiabatic compression induced by gaseous baryonic infall was used by Blumenthal et al. (1986), Flores et al. (1993), and Mo et al. (1998) to describe the effects on the DM distribution of baryon settling in virialized DM halos.”

“This process is dubbed ‘adiabatic contraction’ (e.g. Blumenthal et al. 1986, Gnedin et al. 2004).”

“The classic halo response model of Blumenthal et al. (1986), which assumes an adiabatic contraction of the radial mass profile, is now thought to overpredict the response (e.g. Gnedin et al. 2004, 2010; Abadi et al. 2010).”

“The effect of gas cooling on the dark halo has been interpreted in terms of adiabatic contraction (AC) of the particle orbits (Blumenthal et al. 1986; Gnedin et al. 2004), meaning that individual orbits are compressed inwards, while conserving the adiabatic invariant I = rM(<r).”

“This adiabatic contraction effect was worked out analytically in [370] and its description has since been refined [371, 372].”

“…based on the initial angular momentum of the gas and the halo profile, assuming that angular momentum is conserved and that the self-gravity of the collapsing baryons causes contraction of the matter in the inner part of the halo (Blumenthal et al. 1986; Flores et al. 1993; Mo, Mao & White 1998).”

“This process can be described as adiabatic contraction (Blumenthal et al. 1986; Flores et al. 1993; Dalcanton et al. 1997), which we discuss at length in §3.1.”

“It is well established that baryonic physics alters the particulars of DM haloes and subhalo populations (e.g. Blumenthal et al. 1986; Tissera & Dominguez-Tenreiro 1998; Libeskind et al. 2010; Romano-Dı́az et al. 2010; di Cintio et al. 2011; Schewtschenko & Macciò 2011; Zemp et al. 2012), there…”

“…radius residuals imposes strong constraints on the contribution of disk gravity to the rotation speed; disk gravity should cause more compact galaxies to rotate faster, and the impact of the disk on the inner halo profile (Blumenthal et al. 1986; Gnedin et al. 2004) should amplify this effect.”

“, riMi = rfMf , where Mi and Mf are the initial (dark-matter-only) and final (dark-matter-baryon) enclosed mass [29, 30].”

“It is argued that the baryons in the disk will tend to contract the halo while it is forming (e.g., Blumenthal et al. 1986; Gnedin et al. 2004).”

“The adiabatic parameter considered in the first generation of adiabatic contraction models for collapsing haloes (Blumenthal et al. 1986) was the product of radius with the mass internal to this radius, M(< r)r. Gnedin et al. (2004), henceforth G04, found that such a simple scheme, only strictly…”

“The cause of the small scale enhancement is the additional cooling pro- duced by the presence of baryons, which leads to an adiabatic contraction of the matter distribution at these scales (Blumenthal et al. 1986).”

“We follow Blumenthal et al. (1986) and Flores et al. (1993) and assume that the halo responds adiabatically to the slow assembly of the baryonic matter in disk and bulge, and that it remains spherical (see also Dalcanton et al. 1997 and Mo et al. 1998).”

“To model this effect it is common to use adiabatic invariants or some small modification of them [7, 8, 9, 10, 11, 12, 13, 14, 15, 16].”

“There is long history of studies relying on spin parameter distributions derived from dissipationless simulations to predict disk sizes and bulge properties in galaxies (e.g., Fall & Efstathiou 1980; Blumenthal et al. 1986; Mo et al. 1998; Bullock et al. 2001).”

“The dark matter halo has a total mass ofMvir = 1012 M⊙, a scale radiusrs = 26.47 kpc, and is initially adiabatically contracted to model its response to the formation of a stellar disc in its central region (Blumenthal et al. 1986; Mo et al. 1998).”

“Another possibility is that a process like adiabatic contraction has raised the central halo density (e.g., Blumenthal et al. 1986).”

“Note that our approach, and the exposition here, are closely based on the formalism presented in Blumenthal et al. (1986), Flores et al. (1993), and Mo et al. (1998, MMW98).”

“We attribute this to the domination of the mass budget by the stellar component which pulls DM along with it through adiabatic contraction (Blumenthal et al. 1986).”

“…Halo Models In order to connect these models to theoretical expectations, we must relate the halo parameters to estimates from simulation and account for the changes in the dark matter distribution produced by the baryonic component known as ‘‘adiabatic compression’’ (Blumenthal et al. 1986).”

“…stars, and that the remaining matter (the dark matter mass fraction) is adiabatically compressed by the stellar matter following 2 See the Appendix for an explanation of why this is still justified for the Sersic profile fits that we use. c© 0000 RAS, MNRAS 000, 000–000 Blumenthal et al. (1986).”

“The formalism often used to model this collapse is known as the adiabatic-compression or circular-orbit approximation (see e.g. Faber 1981; Blumenthal et al. 1986).”

“This result is in qualitative agreement with many theoretical studies of the evolution of spheroidal galaxies (Blumenthal et al. 1986; Gnedin et al. 2004; Gustafsson et al. 2006; Abadi et al. 2010; Duffy et al. 2010).”

“Adiabatic contraction (Blumenthal et al. 1986; Gnedin et al. 2004a) would lead to a steepening of the central DM density profile at scales of a few kpc and below.”

“The broad isothermal region obtained by this prescription is illustrated in Figure 4. We note that adiabatic contraction [12, 13 , 14] modifies the NFW profile, leading to more centrally concentrated profile of dark matter.”

“Initially, we see an increase in the central DM due to adiabatic contraction (Blumenthal et al. 1986; Gnedin et al. 2004) for all the galaxies with a peak central DM mass reached at z ∼ 3.”

“Therefore, we first subtracted from the observed dark matter profile, ρDM,Krou, the expected effect of baryon contraction by assuming the adiabatic approximation (i.e. by inverting the equations of Blumenthal et al. 1986).”

“This “halo contraction” is also found in other studies (e.g., Blumenthal et al. 1986; Gnedin et al. 2004, 2011).”

“Such high values of Vopt/V200 are naturally explained by the combined effects of baryons adding to the optical circular velocity directly, and indirectly by inducing contraction of the dark matter halo (Blumenthal et al. 1986).”

“The effect of baryons on the structure of haloes has been studied extensively, both using analytical models (e.g. Blumenthal et al. 1986; Sellwood & McGaugh 2005) and in numerical simulations (e.g. Abadi et al. 2010; Duffy et al. 2010; Bryan et al. 2012).”

“Thus, halos appeared denser in hydrodynamic simulations than in dark-matter-only simulations [366, 367].”

“…of the dark matter particle orbits implies R[Mb(R) + Mh(R)] = RiMi(ri) = RiMh,i(R) 1 − F (11) which can be solved iteratively for the final dark matter mass distribution Mh(R), given the initial total mass distribution Mh,i(Ri) and the final baryon mass distribution Mb(R) (Blumenthal et al. 1986).”

“7 do not take the impact of the baryon collapse on the halo shape into account, which tends to increase αint over the values determined from collisionless simulations (Blumenthal et al. 1986; Flores et al. 1993; Gnedin et al. 2004).”

“However, allowing for adiabatic contraction (e.g., Blumenthal et al. 1986; Gnedin et al. 2004) of the dark matter profile in most cases degrades the fits, suggesting a more complex interplay between the baryons and the dark matter (e.g., Loeb & Peebles 2003; El-Zant et al. 2004; Dutton et al. 2006).”

“The density profile of galaxy haloes will be modified by the baryons cooling in the halo (e.g. Blumenthal et al. 1986; Jesseit et al. 2002; Gnedin et al. 2004; Abadi et al. 2009; Duffy et al. 2010).”

“One way galaxy formation can affect dark matter is by boosting central dark matter densities as a result of baryons clustering at the centre of the halo (Blumenthal et al. 1986).”

“Since galaxies form at the centers of dark matter halos (White & Rees 1978; Blumenthal et al. 1986; Dubinski 1994; Mo et al. 1998), the dynamics of infalling satellite halos will also influence the evolution of the accompanying galaxy populations.”

“Adiabatic contraction conserves both the mass and the angular momentum of the cold baryons and dark matter particles (Blumenthal et al., 1986; Kochanek & White, 2001).”

“We note that the Widrow & Dubinski (2005) method for building disk galaxies does not explicitly take into account the adiabatic contraction of the halo in response to the slow accumulation of the baryons (e.g., Blumenthal et al. 1986).”

“After z ∼ 1, contraction of the potential due to continued accumulation of baryons at high density (e.g. Blumenthal et al. 1986) actually drives stars to migrate inwards, partially undoing outward migration at earlier times.”

“Throughout we assume that the disk is infinitesimally thin, and each time step we use the adiabatic invariant formalism of Blumenthal et al. (1986) and Flores et al. (1993) to compute the gravitational contraction of the dark matter induced by the baryons settling in the disk.”

“It is shown that adiabatic compression (e.g., Blumenthal et al. 1986) yields nearly flat rotation curves for a range of initial halo concentrations and cooled baryon fractions (see also Kochanek & White 2001 and Kochanek 2003), but typical CDM halos (e.g., Bullock et al. 2001) appear to be too…”

“Blumenthal et al. (1986) and Flores et al. (1993) investigated how adiabatic contraction of dark matter haloes impacts on the rotation curves of disk galaxies.”

“…Manrique et al. 2003) argue that the central density profile is linked to the merging history of dark matter substructure, and baryons have been invoked both to flatten (e.g. El-Zant, Shlosman & Hoffman 2001; El-Zant et al. 2003) and to steepen (Blumenthal et al. 1986) the dark matter profile.”

“The models include a dark matter halo initially with the NFW density profile modified by the standard adiabatic contraction (Blumenthal et al. 1986).”