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Farhad Zadeh

Professor

PhD, Columbia University
Curriculum Vitae

Teaching and Public Outreach
Public Lectures on the Web
Recent Work in the News

Professional Interests

  • Cosmic Rays and Magnetic Fields in the Nucleus of the Galaxy
  • The Galactic Center Supermassive Black Hole and its Environment
  • Star Formation in Extreme Environments
  • Interacting Supernova Remnants

Key Research Contributions

Magnetized Radio Filaments in the Galactic Center

Farhad Yusef‑Zadeh is widely recognized for the discovery and characterization of the magnetized radio filaments permeating the central region of the Milky Way. His work revealed that these long, narrow structures trace strong, ordered magnetic fields and represent one of the most striking signatures of nonthermal activity in the Galactic Center. Subsequent surveys—including recent MeerKAT observations—have expanded and confirmed the significance of these filaments, deepening understanding of the region’s magnetic topology and energetic history.

Multi‑Wavelength Studies of Sagittarius A*

He has led extensive campaigns to monitor flares and variability from the Galaxy’s supermassive black hole, Sagittarius A*. By integrating radio, infrared, and X‑ray data from major observatories, such as James Web Space Telescope, ALma. VLA, and NuSTAR), his research has helped clarify the mechanisms behind particle acceleration, magnetic reconnection, and accretion‑flow instabilities near the event horizon.

Cosmic Rays and Energetic Feedback in the Galactic Nucleus

Yusef‑Zadeh’s work has highlighted the crucial role of cosmic rays in shaping the physical state of the Galactic Center’s interstellar medium. His studies have shown that elevated cosmic‑ray ionization rates influence the chemistry, heating, and large‑scale energetics of the region, providing insight into how feedback from massive stars and black hole activity affects the nuclear environment.

Star Formation Under Extreme Tidal Forces

His research has contributed significantly to understanding star formation in the immediate vicinity of a supermassive black hole, an environment traditionally believed to suppress cloud collapse. Observations of young stars near Sgr A* have motivated theoretical refinements on how stars can form and evolve within intense tidal and magnetic fields.

 

Teaching and Public Outreach

A Brief Journey Through the Invisible Universe (ASTRON 106)

Class description

This is a descriptive course using simple mathematics concentrating on some of the most exciting concepts in astrophysics. Describe cool objects in the universe that cannot be viewed or understood in the visible spectrum of radiation.

“Light is the Visible reminder of invisible light” T.S. Elliot

Learning about the history of radio astronomy, including how radio telescopes work appreciates the sense of belonging created by the wider context of physics and astronomy, and the possibilities of identifying carbon-based organic life elsewhere in our galaxy feeling small but being part of a structure bigger than myself: Fundamental to our survival.

Roughly, two chapters per week plus some chapters from the Invisible Universe which covers Radio astronomy. X-ray astronomy topics are from my own notes and will be discussed in class when appropriate

Two on-line exams (midterm and final) will be given in class

     30%, 40% of the final grade, 25% assignments and 5% class discussion. Class attendance and participation are important

Textbooks:

1) Notes by Felix Lockman (provided)

2) Required paperback book:

                The Invisible Universe Why There's More to Reality than Meets the Eye

Author: M. Bothwell, Oneworld Publications

Reading should be done before class. We discuss each chapter of the textbooks in class.

Week 1
Light: Electromagnetic radiation
Thermal radio emission: The planets

Week 2
The Birth of Radio and X-ray Astronomy and the discovery of nonthermal radiation
Tour of the radio universe

Week 3:
Radio and X-ray telescopes and how they work
Radio Interferometry

Week 4:
Hydrogen and the structure of galaxies
Dark Matter

Week 5: 
Pulsars and clocks

Week 6:
Pulsars and gravity

Week 7:
The Big Bang: the oldest radio waves, Cosmology

Week 8:
Astrochemistry, SETI

Week 9
Black Holes, the center of our Galaxy

Basics of Radio Astronomy (ASTRON 305/405)

Class description:

Radio astronomy is the study of natural radio emission from celestial objects at frequencies outside FM and GPS frequencies. The radio band is very broad, spanning between 10^7 to 10^12 Hz, whereas our eyes are only sensitive between red and blue, a factor of two. This course covers how radio waves are received or transmitted by radio telescopes and discuss how different these techniques are at other wavelengths. We will explore the realm of the invisible sky using radio antennas and interferometers, and describe numerous discoveries made over the last 90 years (e.g., pulsars, quasars, cosmic, microwave background radiation, organic molecules).

Radio astrophysics has played a big role in almost every aspect of astronomy and astrophysics from the study of cosmic rays, synchrotron radiation, pulsars, Cosmic microwave background radiation, density fluctuations of the 3K background to star formation, protoplanetary disks, rotation period of mercury and surface temperature of Venus. It is a field that is unique when compared to other fields of astronomy.  This is because of the low quantum noise and the ability of preserving both the phase and amplitude of incoming signals as a function of time.  This advantage allows radio astronomers to build interferometers with applications to atom interferometers to search gravitational waves or Dark Matter particles.

The course is based on a textbook by Jim Condon and Scott Ransom. This textbook covers material radio astrophysics and mpre thermodynamics than electromagnetism; Kirchhoff’s law appears more in this textbook than Maxwell's equations.

Learning Objectives:
History of radio astronomy; Antenna theory, interferometry and aperture synthesis; Radio waves and the emission mechanisms at radio wavelengths. Basic physics principles relevant to radio astronomy.

Teaching Method:
80-min lectures on Tuesdays and solving problems related to Tuesday's lectures on Thursdays.

Zoom Discussion at 5PM on Mondays.

Evaluation Method:
Final (35%), weekly homework assignments (55%), class participation and attendance (10%)

Class Materials (Required):
Essential Radio Astronomy; by J. Condon and S. Ransom Princeton University Press, ISBN 978-0-691-13779-7. This textbook can be viewed online for free. Professor Zadeh will also provide some additional notes.

Topics that will be covered:
  • Introduction
  • Atmospheric windows
  • Astronomy in the Radio Window
  • What is special about Long Wavelengths and Low frequencies
  • The discovery of cosmic radio noise
  • Tour of the radio universe
  • Brightness vs Flux density
  • Radiation transfer through the earth's atmosphere and the discovery of the 3K CMB
  • Planck function focusing on:
    • RJ approximation 
    • 1D Nyquist  approximation
    • Larmor radiation: from an electron, from a short dipole antenna, from 1/2-wave dipole, from 1/4 wave dipole, from 1-D reflecting antenna, from 2-D reflecting antenna
    • Power gain vs aperture size of a reflecting antenna
    • Reciprocity theory
    • The Fourier Transform: illuminated aperture vs the beam pattern
    • Radiometer theorem
    • Sampling theorem
    • Young's  2-slit experiment
    • atmom interferometers
    • 2-element interferometry
    • Application of Bremsstrahlung and  synchrotron radiation to radio galaxies

Imaging in Astronomy (ASTRON 130)

This new service course for non-majors draws upon real-world examples from my own research interests to illustrate how image analysis is used to extract information in astronomy. One of the objectives of this course is to communicate that astronomical images obtained in different wavelength bands can be used as a vehicle to gain a better understanding of the physical laws. This course is designed for undergraduate non-science majors interested in learning astronomy through the manipulation of astronomical images of celestial objects. The IT group developed nine web-based homework assignments which are given to students once a week during the quarter. These assignments are as follows:

  1. Jupiter
  2. The Milky Way Galaxy
  3. The Interstellar Extinction
  4. The Evolution of Stars: HR Diagram
  5. Jets from Protostars
  6. The Expansion of Supernova
  7. Masers: Signposts of Cosmic Collision
  8. Motion of Stars around a massive Black Hole
  9. Radio Filaments at the Core of the Galaxy
  10. The Sun
  11. Trifid Nebula

Imaging and Imagining Space

A collaboration between Farhad Zadeh and Pamela Bannos, who is a photographer and who teaches at NU, resulted in an exhibition at the Block Gallery. The IT department developed a website in collaboration with us. To learn more about astronomical images visit http://spaceimages.northwestern.edu.

Public Lectures on the Web

I have embarked on an outreach program of public lectures that has featured diverse and interesting topics with broad appeal to students and the public. These public lectures are videotaped and can be viewed on NU's department of Physics and Astronomy website here. 

The topics of these lectures are as follows:

"Music of the Spheres"
Professor Arthur Schmidt

"Copenhagen and the German Atomic Bomb Project: Bending Perception to Wish"
Professor Irving Klotz

"What's Your Sign? Astrology, Astronomy, and Pseudoscience"
Professor Michael Faison

"The History of Physics: Paul Dirac -- A Beautiful Mind in the 20th Century"
Professor Laurie Brown

"Einstein and the FBI"
Fred Jerome

"Ruby Payne-Scott (1912-1981): The First Woman Radio Astronomer"
Miller Goss, Ph.D.

"The Birth and Death of Stars"
Professor Walter Lewin

"Tsunami: The Ultimate Sea Waves, Long-range Vectors of Death and Destruction"
Professor Emile Okal

"The Changing Face of Mars"
Doug Roberts, Ph.D.

"Asteroids: Their History, their Impact on Earth and their Complex Geology"
Professor Mark S. Robinson

Recent Work in the News

Selected Publications

  • Yusef-Zadeh, F., Roberts, D. A., Bushouse, H., Wardle, M., Cotton, W., Royster, M. & van Moorsel, G.
    The Discovery of Radio Stars within 10'' of Sgr A* at 7 mm, 2014, ApJ, 792, L1--L6
  • Yusef-Zadeh, F., Royster, M., Wardle, M., Arendt, R., Bushouse, H., Lis, D. C., Pound, M. W., Roberts, D. A., Whitney, B., & Wootten, A.
    ALMA Observations of the Galactic Center: SiO Outflows and High-mass Star Formation near Sgr A*, 2013, ApJ, 767, L32--L37
  • Yusef-Zadeh, F., Hewitt, J. W., Arendt, R. G., Whitney, B., Rieke, G.,
    Wardle, M., Hinz, J. L., Stolovy, S., Lang, C. C., Burton, M. G., and
    Ramirez, S.
    Star Formation in the Central 400 pc of the Milky Way: Evidence for a Population of Massive Young Stellar Objects, 2009, ApJ, 702, 178--225
  • Yusef-Zadeh, F., Bushouse, H., Wardle, M., Heinke, C., Roberts, D. A. et al.
    Dowell, C. D., Brunthaler, A., Reid, M. J., Martin, C. L., Marrone, D. P.,
    Porquet, D., Grosso, N., Dodds-Eden, K., Bower, G. C., Wiesemeyer, H.,
    Miyazaki, A., Pal, S., Gillessen, S., Goldwurm, A., Trap, G., and Maness, H.
    Simultaneous Multi-Wavelength Observations of Sgr A* During 2007 April
    1-11, 2009, ApJ, 706, 348--375
  • Yusef-Zadeh, F., Roberts, D., Wardle, M., Heinke, C. O. &
    Bower, G. C.
    Flaring Activity of Sagittarius A* at 43 and 22 GHz: Evidence
    for Expanding Hot Plasma, 2006, ApJ, 650, 189--194
  • Yusef-Zadeh, F., Law, C. & Wardle, M.
    The Origin of X-Ray Emission from a Galactic Center Molecular Cloud: Low-Energy Cosmic-Ray Electrons, 2002, ApJ, 568, L121--L124