Sprecher/in: Shivam Burman (Indian Institute of Technology)

Titel: Unveiling Galactic Magnetism: Probing Radial Profile of Galactic Magnetic Fields with Background Quasars

Zusammenfassung: Understanding magnetic fields in distant galaxies is key to exploring how these galaxies evolve and interact with their surroundings. By utilising the rotation measure (RM) of background quasars, we have developed a radial profile of the magnetic field in a typical high-redshift galaxy. We used Mg II absorption systems to identify these intervening galaxies, applying redshift matching criteria where spectroscopic redshifts must lie within 3𝜎 of photometric redshifts, followed by visual inspections. This approach resulted in a sample of 59 quasar-galaxy pairs. The quasar sightlines probe a range of impact parameters (D) up to 160 kpc, covering the circumgalactic medium (CGM) of a typical Milky Way-type galaxy. By analysing the residual rotation measure (RRM) after removing the galactic RM contribution, we estimated the excess RRM dispersion, which we translated into magnetic field strengths assuming a typical electron density. Our findings indicate that magnetic fields are stronger closer to the galaxy’s disk, averaging ~2.39 μG within 50 kpc, and gradually decreasing to ~1.67 μG beyond 50 kpc. These results align well with simulation-based predictions and provide insights into how magnetic fields behave not only in dense galactic regions but also in their more diffuse outskirts. The SKA’s unprecedented sensitivity, wide frequency coverage, and high angular resolution will allow us to vastly increase the number of background quasar sightlines, significantly improving the statistical power of RM-based studies of magnetic fields in high-redshift galaxies. Detecting fainter polarised sources will enable a more detailed characterisation of CGM and intergalactic magnetic fields, revealing their evolution over cosmic time.

Anmerkung: The speaker is around for the day of the talk only.

• Datum:
  23. Juni 2025, 14:00 – 15:00
  
  
• Ort:

  AIP; Kirch-Haus, Konferenzraum

  
  
• Kontakt:
  Lutz Wisotzki
  lwisotzki@aip.de