Galaxy-induced transformation of dark matter haloes: Transformations of CDM haloes

“We adopt cosmological parameters consistent with the combined analysis of the 2dfGRS (Colless et al., 2001) and the first-year WMAP data (Spergel et al., 2003): a present day value of the Hubble constant of H0 = 70 km/s/Mpc; a scalefree initial density perturbation spectrum with no tilt and…”

“The DMO mass profile is shown by the thick red solid curve and, as expected, it is well approximated by the NFW (Navarro et al., 1996b, 1997) formula (thin solid line).”

“The DMO mass profile is shown by the thick red solid curve and, as expected, it is well approximated by the NFW (Navarro et al., 1996b, 1997) formula (thin solid line).”

“Each dot in this panel correspond to an NFW halo with concentration drawn at random from the mass-concentration relation (including scatter) derived by Neto et al. (2007) from the Millennium Simulation (Springel et al., 2005).”

“…formation have adopted this formulation in order to link the (observed) dynamical properties of luminous galaxies to the (predicted) properties of the dark halos that surround them (see, e.g., Mo et al., 1998; Cole et al., 2000; Dutton et al., 2005; Croton et al., 2006; Somerville et al., 2008).”

“The virial density contrast, ∆vir(z) is given by ∆vir(z) = 18π 2 + 82f(z) − 39f(z)2, where f(z) = [Ω0(1 + z)3/(Ω0(1 + z)3 + ΩΛ))] − 1 and Ω0 = ΩCDM + Ωb(Bryan & Norman, 1998).”

“We adopt cosmological parameters consistent with the combined analysis of the 2dfGRS (Colless et al., 2001) and the first-year WMAP data (Spergel et al., 2003): a present day value of the Hubble constant of H0 = 70 km/s/Mpc; a scalefree initial density perturbation spectrum with no tilt and…”

“…formation have adopted this formulation in order to link the (observed) dynamical properties of luminous galaxies to the (predicted) properties of the dark halos that surround them (see, e.g., Mo et al., 1998; Cole et al., 2000; Dutton et al., 2005; Croton et al., 2006; Somerville et al., 2008).”

“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.”

“Despite their chaotic assembly, the spherically-averaged mass profile of CDM halos is nearly “universal”, and can be approximated fairly accurately, regardless of halo mass or redshift, by scaling a simple formula (see, e.g., Navarro et al., 1996b, 1997, 2004, 2008).”

“Successful models require that the rotation speed of disks be of the order of the virial velocity of the halos they inhabit (see, e.g., Somerville & Primack, 1999; Croton et al., 2006).”

“This re-simulation technique follows standard practice, as described, for example, by Power et al. (2003).”

“According to Duffy et al. (2008), this is approximately the change in average concentration when modifying the cosmological parameters from the values we adopt here (which are consistent with the first-year analysis of the WMAP satellite data) to those favoured by the latest 5-year WMAP data…”

“• The halo contraction in our simulations is also less pronounced than found in earlier numerical work (see, e.g., Gnedin et al., 2004), and suggest that the response of a halo does not depend on the final mass and radial distribution of baryons in the central galaxy, but also on the mode of their…”

“CDM halos are distinctly triaxial systems supported by anisotropic velocity dispersion tensors (Frenk et al., 1988; Jing & Suto, 2002; Allgood et al., 2006; Hayashi et al., 2007; Bett et al., 2007), a result that reflects the highly aspherical nature of gravitationally-amplified density…”

“Each dot in this panel correspond to an NFW halo with concentration drawn at random from the mass-concentration relation (including scatter) derived by Neto et al. (2007) from the Millennium Simulation (Springel et al., 2005).”

“The possibility that the virial velocity of the Milky Way is significantly lower than 220 km/s has indeed been advocated by a number of recent observational studies (Smith et al., 2007; Sales et al., 2007; Xue et al., 2008).”

“All our simulations were performed using GASOLINE, a parallel N-body/SPH code described in detail by Wadsley et al. (2004). c© 2008 RAS, MNRAS 000, 000–000”

“The DMO mass profile is shown by the thick red solid curve and, as expected, it is well approximated by the NFW (Navarro et al., 1996b, 1997) formula (thin solid line).”

“The possibility that the virial velocity of the Milky Way is significantly lower than 220 km/s has indeed been advocated by a number of recent observational studies (Smith et al., 2007; Sales et al., 2007; Xue et al., 2008).”

“CDM halos are distinctly triaxial systems supported by anisotropic velocity dispersion tensors (Frenk et al., 1988; Jing & Suto, 2002; Allgood et al., 2006; Hayashi et al., 2007; Bett et al., 2007), a result that reflects the highly aspherical nature of gravitationally-amplified density…”

“CDM halos are distinctly triaxial systems supported by anisotropic velocity dispersion tensors (Frenk et al., 1988; Jing & Suto, 2002; Allgood et al., 2006; Hayashi et al., 2007; Bett et al., 2007), a result that reflects the highly aspherical nature of gravitationally-amplified density…”

“According to Duffy et al. (2008), this is approximately the change in average concentration when modifying the cosmological parameters from the values we adopt here (which are consistent with the first-year analysis of the WMAP satellite data) to those favoured by the latest 5-year WMAP data…”

“…systems supported by anisotropic velocity dispersion tensors (Frenk et al., 1988; Jing & Suto, 2002; Allgood et al., 2006; Hayashi et al., 2007; Bett et al., 2007), a result that reflects the highly aspherical nature of gravitationally-amplified density fluctuations as they become non linear…”

“As discussed by Eke et al. (2001), most ΛCDM halos satisfy the constraints, and would be consistent with the MW if they were somehow able to avoid contraction.”

“On the other hand, Navarro & Steinmetz (2000) argue that it is unlikely that a galaxy where md << fbar may have the same specific angular momentum as the whole system, and propose that jdisk, as a fraction of jvir, should be comparable to the fraction of baryons that make up the central galaxy;…”

“This possibility has been argued before (see, e.g., El-Zant et al., 2001; Ma & BoylanKolchin, 2004; Mo & Mao, 2004), and seems to find favor in our simulations, where mergers between massive baryonic clumps are frequent and plentiful and halo contraction is less strong than reported in earlier work.”

“This was already noted in the first simulations to include, in addition to a dark matter halo, a dissipative baryonic component, such as the early work of Katz & Gunn (1991) and Katz & White (1993).”

“This was already noted in the first simulations to include, in addition to a dark matter halo, a dissipative baryonic component, such as the early work of Katz & Gunn (1991) and Katz & White (1993).”

“1991; Navarro & White, 1994; Navarro et al., 1997), this mode of assembly leads to very efficient accretion of baryons into the central galaxy and to the transfer of much of their angular momentum to the surrounding halo.”

“Recent work has also speculated that mergers may lead to halo expansion and that this would help to reconcile the properties of disk galaxies with ΛCDM halos (Dutton et al., 2007).”

“Dubinski (1994) studied this further by growing adiabatically a central mass concentration inside a triaxial dark matter halo and confirmed that the steepening of the potential leads to much rounder halo shapes.”

“Each simulation follows the evolution of a relatively small region of the Universe, excised from a 4323-particle simulation of a large 50 h−1 Mpc periodic box (Reed et al., 2003), and resimulated at much higher mass and spatial resolution.”

“In this respect, our study is similar to that of Gustafsson et al. (2006), who studied four simulations of galaxysized halos in the ΛCDM scenario.”

“…is truly needed to reconcile disk properties with ΛCDM halos, it should come as a consequence of other processes not considered here, such as feedback-driven winds that may remove substantial fraction of baryons from the central galaxy (see, e.g., Navarro et al., 1996a; Babul & Ferguson, 1996).”

“These correspond to gasdynamical simulations of galaxy formation presented by Abadi et al. (2003a,b) and Meza et al. (2003), and differ from ours mainly in their inclusion of star formation and feedback effects.”

“The possibility that the virial velocity of the Milky Way is significantly lower than 220 km/s has indeed been advocated by a number of recent observational studies (Smith et al., 2007; Sales et al., 2007; Xue et al., 2008).”

“This possibility has been argued before (see, e.g., El-Zant et al., 2001; Ma & BoylanKolchin, 2004; Mo & Mao, 2004), and seems to find favor in our simulations, where mergers between massive baryonic clumps are frequent and plentiful and halo contraction is less strong than reported in earlier work.”

“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.”

“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.”

“Barnes (1987) and Sellwood (1999) have remarked that the adiabatic contraction hypothesis might lead to substantial overestimation of the halo compression.”

“As discussed by Sellwood & McGaugh (2005) and Choi et al. (2006), such deviations are likely to depend strongly on the orbital structure of a halo, performing best when most particles have large tangential motions, but poorly in systems with radially anisotropic velocity distributions.”

“When baryons are included, the halos become more spherical and evolve toward oblate at all radii but mostly in their inner parts (e.g., Kazantzidis et al. 2004, Bailin et al. 2005, Abadi et al. 2010).”

“Remaining effects of baryons on halo potential wells (e.g., making them less triaxial; Abadi et al. 2010) are more difficult to observe, and may require higher-order statistics such as three-point functions to capture.”

“However, recent simulations suggest that this simple scheme overestimates the effect (e.g. Gnedin et al. 2004; Abadi et al. 2010).”

“At the same time, several recent studies showed that no single set of parameters of such simple models describes all objects that form in cosmological simulations equally well(Abadi et al. 2010; Gnedin et al. 2011; Gustafsson, Fairbairn & Sommer-Larsen 2006; Tisseraet al. 2010).”

“…expected from the effect of adiabatic contraction galaxies with significant in-situ star formation, i.e. more dissipation, live in more concentrated halos (Blumenthal et al. 1986; Dubinski 1994; Jesseit et al. 2002; Debattista et al. 2008; Gnedin et al. 2004; Abadi et al. 2010; Auger et al. 2010).”