1. Probing Magnetized Turbulence in the Fermi Bubbles
Kelsey Lund
Advisor: Dr. Christopher Hales
10 September, 2016

2. Meet the Fermi Bubbles:
Discovered by Large Area Telescope (LAT) on Fermi Satellite in 2010
Su, M., Slatyer, T.R., & Finkbeiner, D.P. 2010, ApJ
Initial map made from 1.6 year dataset
Finkbeiner et al, 2010

3. ~40°
~50°
Fermi Bubbles
Milky Way Disk
Sun

4. Across the spectrum: ROSAT 1.5 keV WMAP K-Band
S-PASS 2.3 GHz Polarized Intensity
WMAP 23 GHz Polarized Intensity
Snowden et al.1995, ApJ
Dobler 2012, ApJ
Carretti et al, 2013, Nature

5. Origin? Active galactic nucleus activity Star formation activity
Evidence of hard spectrum gamma-ray jet-like structure
Short but bright quasar phase ~6 Myr ago
Known nuclear star forming region
Narrow “waist” (~100 pc) near GC
Bipolar radio bubbles, x-ray cavities in extragalactic sources associated with AGN activity.
Magnetic energy of 4-9 x 1052 erg, outflow speeds of ~1000 km s-1
Injection rate ~ erg s-1
- Cosmic ray population necessary to produce gamma-ray signal?
Bland-Hawthorn et al, 2013, ApJ
Su et al, 2012, ApJ
Zubovas et al, 2011,MNRASL
Carretti et al, 2013, Nature
Crocker et al, 2011, PRL
Lacki, 2014, MNRASL
Image: Durham University, 2014

6. From There to Here with Faraday Rotation…
Fermi Bubble RM

7. From There to Here with Faraday Rotation…
Intrinsic RM
IGM RM
Local/ISM RM
Cluster Medium RM
Ionospheric RM
Fermi Bubble RM

9. Target Selection Taken from NRAO VLA Sky Survey (NVSS) catalogue
Better noise constraints: 0.45 mJy beam-1  0.25 mJy beam-1
Wider bandwidth  More accurate rotation measures
- Target faint polarized sources without RM
Condon et al1998, AJ
Taylor et al, 2009, ApJ

10. Where to look?
ANTARES Collaboration, 2013, European Physical Journal

11. The Observation: VLA observation on 6 May, 2016:
511 extragalactic sources, individual pointings
20° x 7° strip along eastern edge of Northern bubble
4 hours
CnB configuration [~15” beam size]
1-2 GHz (L-Band)
8 spectral windows, 64 channels each
2 MHz channel width

12. Data Reduction Manually reduced data from scratch
Included ionospheric calibration on CASA stable build
Imaging and analysis in CASA 4.6.0
Batch processing on cluster
Rotation measure synthesis (Brentjens & de Bruyn, 2005)
Compilation of results into catalogue

13. Results Using NVSS Data
Galactic Longitude (deg)
Galactic Longitude (deg)

14. Preliminary Results: Current Status

15. Science with the Fermi Bubbles
Energetics Shock strengths, constraints on Mach number and Alfvén velocity
Strong shock indicative of AGN?
Contributions to models of galaxy evolution
magnetic pressure >> dominates the thermal gas pressure

16. Future work Identify analysis issue and obtain catalog
Use catalog to map out variance as a function of spatial position
Rerun analysis without TEC correction, verify CASA performance
Perform simulation of ne and magnetic power spectra
Contribute useful data to literature
NOAO, 2004
ESO, 2009

17. NAC Experience

18. Appendix A: Radio Emission of the Fermi Bubbles
Carretti et al, 2013, Nature

19. Appendix B: Gamma-Ray Jets in the Milky Way
Su , M., Finkbeiner, D.P. 2012, ApJ, 753:61

20. Appendix C: The Faraday Sky
Bottom one is reconstructed galactic sky, while upper one is entire NVSS from Taylor.
Taylor et al, 2009, ApJ
Oppermann, N. et al, 2011, A&A

21. Appendix D: Rotation Measure Synthesis