The Baryon Induced Transformation of CDM Halos Mario

The Baryon Induced Transformation of CDM Halos Mario G. Abadi Universidad Nacional de Córdoba, CONICET Argentina In collaboration with Julio Navarro and the Canadian Computational Cosmology Collaboration (C 4), University of Victoria, Canada LENAC Latin-american Workshop October 29 to November 1 Guaruja Brazil

How dark matter halos are transformed by baryons? Profile (Theory vs Simulations) Shape (Sphericity vs Triaxiality) Orientation (Halo vs Disk)

Introduction

Profile: Theory Blumenthal et al. (1986) Contraction of a dark matter halo in response to condensation of baryons in its center. The cooling of gas in the centers of dark matter halos is expected to lead to a more concentrated dark matter distribution. The response of dark matter to the condensation of baryons is usually calculated using the standard model of adiabatic contraction

Adiabatic contraction Spherically simetric dark matter halo with circular orbits Conservation of the adiabatic invariant M(r)r I=Integral of q dp = Integral of p dq If p is the circular velocity, then dq=r dtheta I=Integral of v r dtheta using v^2=GM/r I=Int(GM/r)^(1/2) r dtheta = (GM/r)^(1/2) Int(dtheta)/2 pi=(GM/r)^(1/2) I=GMr=r^2 v^2

Profile: Simulations Gnedin et al (2004) High-resolution cosmological simulations which include gas dynamics, radiative cooling, and star formation Particle orbits in the halos are highly eccentric Dissipation of gas indeed increases the density of dark matter and steepens its radial profile in the inner regions of halos compared to the case without cooling Simple modification of the assumed invariant from M(r)r to M(r_av)r, where r and r_av are the current and orbitaveraged particle positions

Profile: Simulations Abadi et al. (2006) The adiabatic contraction model C 4 Numerical simulations Simulations of 13 galactic dark matter halos With and without gas High and low resolution One halo also at super high and super low resolution

Profile: Simulations Abadi et al. (2006) The abadiatic contraction model C 4 Numerical simulations Simulations of 13 galactic dark matter halos With and without gas High and low resolution One halo also at super high and super low resolution

Dark matter halo: with and without gas

Circular Velocity Profile Circular velocity and density profiles are increased by the presence of the baryons Different models give different dark matter profiles in the inner parts

Contracted dark matter halos Polinomial fit to infer contracted dark matter profiles from non-contracted dark matter + gas profiles

Inverse model ● Total mass of the disk Mdisk ● Contribution of the exponential disk to the total velocity ● Vdisk^2(r)=2 G Mdisk/Rdisk x^2 (I 0(x) K 0(x)-I 1(x) K 1(x)) ● where x=r/2/Rdisk ● Contribution of the (contracted) dark matter halo to the total velocity Vdark^2=Vrot^2 -Vdisk^2 ● Invert the model in order to obtain the circular velocity of the noncontracted (i. e. without gas) dark matter (only) halo at r=2. 2 Rdisk ● Assuming the shape of the dark matter halo (i. e. a concentration parameter “c” for the NFW fit), you have the non-contracted dark matter halo density profile and its Vvirial and Vmaximum

Application to the Milky Way Mdisk=6. 0 x 10^10 solar masses Rdisk=3. 5 kpc Vrot(2. 2 Rdisk)=220 km/sec Mvir=1. 9, 1. 0 and 0. 3 10^12 solar masses Mvir > Mdisk/f_b=0. 4 10^12 solar masses Ours: Vmax=188, Vvir=156 km/s Gnedin: Vmax=155, Vvir=129 km/s Standard: Vmax=107, Vvir= 89 km/s

Application Semianalytic models

Application to other galaxies ● Main observables for galaxies: x-band surface brightness profile (photometry) and rotation curve (kinematic) ● Obtain x-band scalelength Rdisk of and exponential disk, rotational velocity Vrot(r=2. 2 Rdisk) and also x-band total luminosity L ● Assume a stellar mass-to-light ratio M/L (REM: depends on the color index) ● It is possible to obtain the disk total mass Mdisk ● Go back 3 slides: “Inverse model” ● Compare Vrot vs Vmax

Luminosities and Scalelenghts ● Courteau (1996, 1997) 306 galaxies with luminosities and scalelengths in Kent-Thuan-Gunn system r-band. Also luminosities in Johnson B-band from RC 3 taken from NED ● r=R+0. 94 (Jorgensen 1994) ● Courteau et al (2000) only 36 galaxies with absolute magnitudes and scalelenghts in "Landolt" (is interchangeable with Johnson) I-band SDSS colors (g-r) and (g-i) ● i=I+0. 62 and g=V+0. 49 (Courteau et al 2006) ● M-Msun=-2. 5 Log(L/Lsun)

Mass-to-light ratio guesstimation from Bell & de Jong (2001) ● ● Compute R=r-0. 354 (Jorgensen 1994), then compute B-R, then. M/LR=a. R+b. R(B-R) Compute i=I+0. 62, then g=i+(g-i), then V=g-0. 49, then (V-I), then M/LI=a. I+b. I (V-I)

Mass-to-light ratio guesstimation from Bell et al (2003) ● M/Li=ai+bi(g-r) and/or M/Li=ai+bi(g-i)

The baryonic Tully-Fisher relation ● ● B-R colors (white dots) g-i colors (green dots)

The baryonic Tully-Fisher relation ● ● B-R colors (white dots) g-r colors (green dots)

The baryonic Tully-Fisher relation ● ● B-R colors (white dots) V-I colors (green dots)

Application to UGC 5794 Mdisk=7. 4 x 10^9 solar masses Rdisk=2. 5 kpc Vrot(2. 2 Rdisk)=128 km/sec Mvir=1. 9, 1. 8 and 1. 6 10^12 solar masses Mvir > Mdisk/f_b=5. 4 10^10 solar masses

Vrot vs Vmax: Galaxies “with” disk ● ● Vrot = Vmax corresponds to semianalytic models that simultaneously reproduce both the Tully-Fisher and the luminosity function There are differences between the 3 models

Vrot vs Vmax: Galaxies “without” disk ● ● Vrot = Vmax corresponds to semianalytic models that simultaneously reproduce both the Tully-Fisher and the luminosity function There are no differences between the 3 models

Conclusions ● ● ● A new model for the contraction of dark matter halos Previous models (probably? ) overestimate the amount of contraction (Bower & Benson: reason for small disk in semianalytic models? ) Nice rotation curve for the Milky Way Agreement with semianalytic models Pending: application to other galaxies with more or less reliable M/L ratios