Kinetic SZ effect from galaxy cluster rotation&
Another relativistic correction to the SZE
JC, Gert Hütsi and Rashid Sunyaev
accepted by A&A, 2005, astro-ph/0409058
Max-Planck-Institut für Astrophysik
Jens Chluba and Karl Mannheim
A&A 396, 419-428 (2002)
Universitäts-Sternwarte Göttingen
Kinetic SZ effect from
galaxy cluster rotation
Large & smalle scale motion of the ICM
SZ effect and Alma workshop - Orsay - April 2005 - Jens Chluba - MPA-Garching
• Mergers in the cosmological context
should excite large & small scale motion of the ICM ! (off-axis mergers)
• Coma Cluster (XMM)
(Schuecker et al., 2004) turbulent motions on scales ~20-145 kpc (core radius 420 kpc) turbulence on larger scalesis possible!
• Turbulent cascades• from large small scales• viscosity• plasma instabilities• magnetic fields• transition between k-SZ & th-SZ
Schuecker et al., 2004
Large & smalle scale motion of the ICM (2)
• Hydrodynamic simulations by Norman & Bryan 1999 turbulent velocities ~ 25-60% of virial velocity minor mergers maintain the level of turbulence also found „ordered“ circulation, which is likely due to a off-axis merger
• X-ray spectral lines for Centaurus cluster (Dupke & Bregman 2001)
bulk velocities of the order of ~1000 km/s likely due to a previous off-axis merger
• Several recent hydrodynamic simulations (Nagai et al. 2003; Torman, Moscardini & Yoshida 2004; Diaferio, Borgani, Moscardini et al. 2005)
bulk velocities v ~ few 100 km/s
SZ effect and Alma workshop - Orsay - April 2005 - Jens Chluba - MPA-Garching
Toy-model for large scale motion of the ICM
• Initial stage after (major) merger one large scale eddie simple assumption: solid body rotation line of sight velocity constant
• Gas follows isothermal -model line of sight integral analytical
• spectral dependence like k-SZ• dipolar signature (inclination)• extrema at y ~ few rc
• core ~ 10-5 to few 10-4
T ~ 0.1 - few 10 µK
)sin( 1
ccore r
y
e
ex
I
Ix
x
=0.75, =90°, Rmax= 10 rc
SZ effect and Alma workshop - Orsay - April 2005 - Jens Chluba - MPA-Garching
Multi-frequency observations of the SZE
• Main signals th-SZ and k-SZ
• RJ part of the CMB spectrum th-SZ dominant
• close to cross-over frequency k-SZ + rk-SZ
• shift of the maximum: y ~ fraction of the core radius optimistic: y ~ few arcsec even more optimistic: y up to arcmin (no k-SZ)
• Comparison of SZ image at different frequencies• This probably also happens for two merging lumps
• linear polarization many orders smaller (few nK or a fraction of µK level) sensitive to the transverse velocity optimistic: on the level of a few % relative to the k-SZ polarization k-SZ + rk-SZ tilt of the planes of polarization by a few degree frequency-independent (in principle separable from e.g. multiple scattering for rich clusters...)
SZ effect and Alma workshop - Orsay - April 2005 - Jens Chluba - MPA-Garching
Another relativistic correction to the SZE....
SZ effect from clusters of galaxies
• Relativistic temperatures & peculiar motions (Rephaeli, 1995;
Challinor & Lasenby 1998; Sazonov & Sunyaev, 1998; Itoh et al., 1998) corrections to the lowest order signals especially important at high frequencies 10-20% deviations possiblility to measure the electron temperature only with the CMB (strong frequency dependence)
• non-thermal SZ
• Motion of the Solar System ! (Chluba, Hütsi &
Sunyaev, 2004) • has been neglected so far• SZ effect: imprint in the CMB rest frame• Doppler boosting & aberration• Lorentz boosted y-distortion correction similar to
the first order temperature correction to the k-SZ
• easy to take into account!
SZ effect and Alma workshop - Orsay - April 2005 - Jens Chluba - MPA-Garching
Motion-induced Change of SZ Brightness
• Example kTe= 5.1 keV, c = 10-3 and o = 1.241 10-3
• strong frequency and spatial dependence• can reach the level of 10% of the k-SZ at high frequencies (e.g.14% at 400 GHz)
• RJ- limits: motion-induced correction to th-SZ: T/T=-2 y o
SZ effect and Alma workshop - Orsay - April 2005 - Jens Chluba - MPA-Garching
• simple analytic model for k-SZ from cluster rotation• dipolar signature on few 10 arcsec angular scales close to center• T ~ 0.1 - few 10 µK• comparing multi-fequency morphology may be useful• combined with polarization very useful to constraint motions of ICM• turbulent motions interesting contribution to th-SZ (transition)
• motion-induced correction to the th-SZ similar to the first order temperature correction to the k-SZ
• strong spectral & spacial dependence• reaches the 10% level of the k-SZ• easy to take into account !!!• Dipolar asymmetry of the cluster number counts (1% level)
Conclusions