FINGERPRINTS OF GALACTIC LOOP I ON THE COSMIC MICROWAVE
BACKGROUND
Hao Liu @ Bielefeld, 2014
Co-author: Subir Sarkar & philip merch
The radio loops by SNR• Loops and spurs: The angular power spectrum of the Galactic
synchrotron background (Philipp & Subir, arxiv:1304.1078)– Shell by old supernova remnants– Only 4 are visible in radio maps
Loop I emission in multi-frequency domains
Haslam 408 MHZ
Loop I emission in multi-frequency domains
WMAP K-band Pol P
Loop I emission in multi-frequency domains
Planck 857 GHZ
Loop I emission in multi-frequency domains
ROSAT low energy
Loop I emission in multi-frequency domains
ROSAT high energy
Points of interest
• Existence– There be.– More?
• Be in the background?– A problem of foreground removal– CMB intensity or polarization? Or both?
• Mechanism– The wide frequency range– Polarization– Magnetic dust?
Fingerprints of Galactic Loop I on the Cosmic Microwave Background, Hao Liu et al.
arXiv:1404.1899, submitted to APJL
Finding the fingerprints of the Loops
• Average temperature (23 uK, 1%)
• Skewness (-0.68, 3%)
• Clustering (Corr(T,G) = -0.22, 0.036%.)
How it escapes the foreground subtracting procedure?
• The should be no loop (so this is not cosmic).
• Why it survives?
• Example: ILC
A, coeffs from ext-gal region
(the WMAP scheme)
B, coeffs from Loop I A-B
A - B
Other foreground subtracting Methods
• Only roughly– Low multipoles – A large region is “same”– High multipoles – can be different
• Loop signal: low-l
• There should be a way…
Bicep 2?• We haven’t done enough work to judge
Bicep2. This is only a suggestion.
• Wolleben, M. 2007, Astrophys.J., 664, 349
• More work need to be done to check this foreground
Thanks!