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!