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

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

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

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

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 ~1039 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

From There to Here with Faraday Rotation… Fermi Bubble RM

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

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

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

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

Data Reduction Manually reduced data from scratch Included ionospheric calibration on CASA 4.7.38 - 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

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

Preliminary Results: Current Status

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

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

NAC Experience

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

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

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

Appendix D: Rotation Measure Synthesis