Sunil Simha

ERC 553, A&A, University of Chicago

8023, CIERA, Northwestern University

About Me

I am an observational astronomer fascinated by the diffuse plasma within dark matter halos and the filaments of the cosmic web. My primary research instrument of choice is Fast Radio Bursts (FRBs)—millisecond-duration transient radio events that act as precision cosmological probes. As radio light traverses the universe, it gets dispersed by ionized gas along its path. The dispersion measure (DM) of an FRB provides precise estimates of the total column of diffuse gas it has travelled through, making FRBs invaluable tools for mapping the baryonic constituent of our universe.

My research interests center on Fast Radio Bursts (FRBs) as probes of the circumgalactic and intergalactic media (CGM and IGM), with a focus on understanding the distribution and properties of ionized matter at cosmic scales.

Current Position

Since September 2024, I have been a Brinson Postdoctoral Fellow at the University of Chicago and Northwestern University, conducting research on cosmology and astrophysics.

Education

University of California, Santa Cruz

Ph.D. in Astronomy and Astrophysics (2018 – June 2024)

Santa Cruz, California, USA

Indian Institute of Technology Madras

BS-MS in Physics (2013 – 2018)

Chennai, Tamil Nadu, India

selected publications

FRB 20250316A: A Brilliant and Nearby One-off Fast Radio Burst Localized to 13 pc Precision

CHIME/FRB Collaboration, Thomas C. Abbott, Daniel Amouyal, and 83 more authors

\apjl, Aug 2025

DOI Bib

@article{CHIME/FRBCollaboration2025,
  author = {{CHIME/FRB Collaboration} and {Abbott}, Thomas C. and {Amouyal}, Daniel and {Andersen}, Bridget C. and {Andrew}, Shion E. and {Bandura}, Kevin and {Bhardwaj}, Mohit and {Bhopi}, Kalyani and {Bhusare}, Yash and {Brar}, Charanjot and {Cai}, Alice and {Cassanelli}, Tomas and {Chatterjee}, Shami and {Cliche}, Jean-Fran{\c{c}}ois and {Cook}, Amanda M. and {Curtin}, Alice P. and {Davies-Velie}, Evan and {Dobbs}, Matt and {Dong}, Fengqiu Adam and {Dong}, Yuxin and {Eadie}, Gwendolyn and {Eftekhari}, Tarraneh and {Fong}, Wen-Fai and {Fonseca}, Emmanuel and {Gaensler}, B.~M. and {Gusinskaia}, Nina and {Hessels}, Jason W.~T. and {Hewitt}, Dant{\'e} M. and {Huang}, Jeff and {Jain}, Naman and {Joseph}, Ronniy. C. and {Kahinga}, Lordrick and {Kaspi}, Victoria M. and {Khan}, Afrasiyab (Afrokk) and {Kharel}, Bikash and {Lanman}, Adam E. and {L'Argent}, Magnus and {Lazda}, Mattias and {Leung}, Calvin and {Main}, Robert and {Mas-Ribas}, Lluis and {Masui}, Kiyoshi W. and {McGregor}, Kyle and {McKinven}, Ryan and {Mena-Parra}, Juan and {Michilli}, Daniele and {Mulyk}, Nicole and {Ng}, Mason and {Nimmo}, Kenzie and {Pandhi}, Ayush and {Patil}, Swarali Shivraj and {Pearlman}, Aaron B. and {Pen}, Ue-Li and {Pleunis}, Ziggy and {Prochaska}, J. Xavier and {Rafiei-Ravandi}, Masoud and {Ransom}, Scott M. and {Sachdeva}, Gurman and {Sammons}, Mawson W. and {Sand}, Ketan R. and {Scholz}, Paul and {Shah}, Vishwangi and {Shin}, Kaitlyn and {Siegel}, Seth R. and {Simha}, Sunil and {Smith}, Kendrick and {Stairs}, Ingrid and {Stenning}, David C. and {Wang}, Haochen and {Boles}, Thomas and {Cognard}, Isma{\"e}l and {Dijkema}, Tammo Jan and {Filippenko}, Alexei V. and {Gawro{\'n}ski}, Marcin P. and {Herrmann}, Wolfgang and {Kilpatrick}, Charles D. and {Kirsten}, Franz and {Knabel}, Shawn and {Ould-Boukattine}, Omar S. and {Paugnat}, Hadrien and {Puchalska}, Weronika and {Sheu}, William and {Suresh}, Aswin and {Tohuvavohu}, Aaron and {Treu}, Tommaso and {Zheng}, Weikang},
  journal = {\apjl},
  title = {{FRB 20250316A: A Brilliant and Nearby One-off Fast Radio Burst Localized to 13 pc Precision}},
  year = {2025},
  month = aug,
  number = {2},
  pages = {L48},
  volume = {989},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System},
  adsurl = {https://ui.adsabs.harvard.edu/abs/2025ApJ...989L..48C},
  archiveprefix = {arXiv},
  doi = {10.3847/2041-8213/adf62f},
  eid = {L48},
  eprint = {2506.19006},
  keywords = {Radio bursts, Transient detection, Supernova remnants, Interstellar medium, Compact objects, Star forming regions, 1339, 1957, 1667, 847, 288, 1565, High Energy Astrophysical Phenomena},
  primaryclass = {astro-ph.HE}
}

FLIMFLAM DR1: The First Constraints on the Cosmic Baryon Distribution from Eight Fast Radio Burst Sight Lines

Ilya S. Khrykin, Metin Ata, Khee-Gan Lee, and 15 more authors

\apj, Oct 2024

DOI Bib

@article{Khrykin2024,
  author = {{Khrykin}, Ilya S. and {Ata}, Metin and {Lee}, Khee-Gan and {Simha}, Sunil and {Huang}, Yuxin and {Prochaska}, J. Xavier and {Tejos}, Nicolas and {Bannister}, Keith W. and {Cooke}, Jeff and {Day}, Cherie K. and {Deller}, Adam and {Glowacki}, Marcin and {Gordon}, Alexa C. and {James}, Clancy W. and {Marnoch}, Lachlan and {Shannon}, Ryan. M. and {Zhang}, Jielai and {Bernales-Cortes}, Lucas},
  journal = {\apj},
  title = {{FLIMFLAM DR1: The First Constraints on the Cosmic Baryon Distribution from Eight Fast Radio Burst Sight Lines}},
  year = {2024},
  month = oct,
  number = {2},
  pages = {151},
  volume = {973},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System},
  adsurl = {https://ui.adsabs.harvard.edu/abs/2024ApJ...973..151K},
  archiveprefix = {arXiv},
  doi = {10.3847/1538-4357/ad6567},
  eid = {151},
  eprint = {2402.00505},
  keywords = {Missing mass, Intergalactic gas, Circumgalactic medium, Cosmic web, Redshift surveys, 1068, 812, 1879, 330, 1378, Astrophysics of Galaxies, Cosmology and Nongalactic Astrophysics},
  primaryclass = {astro-ph.GA}
}

Searching for the Sources of Excess Extragalactic Dispersion of FRBs

Sunil Simha, Khee-Gan Lee, J. Xavier Prochaska, and 11 more authors

\apj, Sep 2023

DOI Bib

@article{Simha2023,
  author = {{Simha}, Sunil and {Lee}, Khee-Gan and {Prochaska}, J. Xavier and {Khrykin}, Ilya S. and {Huang}, Yuxin and {Tejos}, Nicolas and {Marnoch}, Lachlan and {Ata}, Metin and {Bernales}, Lucas and {Bhandari}, Shivani and {Cooke}, Jeff and {Deller}, Adam T. and {Ryder}, Stuart D. and {Zhang}, Jielai},
  journal = {\apj},
  title = {{Searching for the Sources of Excess Extragalactic Dispersion of FRBs}},
  year = {2023},
  month = sep,
  number = {1},
  pages = {71},
  volume = {954},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System},
  adsurl = {https://ui.adsabs.harvard.edu/abs/2023ApJ...954...71S},
  archiveprefix = {arXiv},
  doi = {10.3847/1538-4357/ace324},
  eid = {71},
  eprint = {2303.07387},
  keywords = {Galaxy dark matter halos, Galaxy evolution, Intergalactic medium, Radio transient sources, 1880, 594, 813, 2008, Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics},
  primaryclass = {astro-ph.GA}
}

Dissecting the Local Environment of FRB 190608 in the Spiral Arm of its Host Galaxy

Jay S. Chittidi, Sunil Simha, Alexandra Mannings, and 15 more authors

\apj, Dec 2021

DOI Bib

@article{Chittidi2021,
  author = {{Chittidi}, Jay S. and {Simha}, Sunil and {Mannings}, Alexandra and {Prochaska}, J. Xavier and {Ryder}, Stuart D. and {Rafelski}, Marc and {Neeleman}, Marcel and {Macquart}, Jean-Pierre and {Tejos}, Nicolas and {Jorgenson}, Regina A. and {Day}, Cherie K. and {Marnoch}, Lachlan and {Bhandari}, Shivani and {Deller}, Adam T. and {Qiu}, Hao and {Bannister}, Keith W. and {Shannon}, Ryan M. and {Heintz}, Kasper E.},
  journal = {\apj},
  title = {{Dissecting the Local Environment of FRB 190608 in the Spiral Arm of its Host Galaxy}},
  year = {2021},
  month = dec,
  number = {2},
  pages = {173},
  volume = {922},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System},
  adsurl = {https://ui.adsabs.harvard.edu/abs/2021ApJ...922..173C},
  archiveprefix = {arXiv},
  doi = {10.3847/1538-4357/ac2818},
  eid = {173},
  eprint = {2005.13158},
  keywords = {1560, 2008, 1339, 1569, 602, Astrophysics - Astrophysics of Galaxies},
  primaryclass = {astro-ph.GA}
}

Estimating the Contribution of Foreground Halos to the FRB 180924 Dispersion Measure

Sunil Simha, Nicolas Tejos, J. Xavier Prochaska, and 6 more authors

\apj, Nov 2021

DOI Bib

@article{Simha2021,
  author = {{Simha}, Sunil and {Tejos}, Nicolas and {Prochaska}, J. Xavier and {Lee}, Khee-Gan and {Ryder}, Stuart D. and {Cantalupo}, Sebastiano and {Bannister}, Keith W. and {Bhandari}, Shivani and {Shannon}, Ryan M.},
  journal = {\apj},
  title = {{Estimating the Contribution of Foreground Halos to the FRB 180924 Dispersion Measure}},
  year = {2021},
  month = nov,
  number = {2},
  pages = {134},
  volume = {921},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System},
  adsurl = {https://ui.adsabs.harvard.edu/abs/2021ApJ...921..134S},
  archiveprefix = {arXiv},
  doi = {10.3847/1538-4357/ac2000},
  eid = {134},
  eprint = {2108.09881},
  keywords = {Galaxy dark matter halos, Cosmology, Quasar absorption line spectroscopy, Radio transient sources, Extragalactic astronomy, 1880, 343, 1317, 2008, 506, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies},
  primaryclass = {astro-ph.CO}
}

Disentangling the Cosmic Web toward FRB 190608

Sunil Simha, Joseph N. Burchett, J. Xavier Prochaska, and 12 more authors

\apj, Oct 2020

DOI Bib

@article{Simha2020,
  author = {{Simha}, Sunil and {Burchett}, Joseph N. and {Prochaska}, J. Xavier and {Chittidi}, Jay S. and {Elek}, Oskar and {Tejos}, Nicolas and {Jorgenson}, Regina and {Bannister}, Keith W. and {Bhandari}, Shivani and {Day}, Cherie K. and {Deller}, Adam T. and {Forbes}, Angus G. and {Macquart}, Jean-Pierre and {Ryder}, Stuart D. and {Shannon}, Ryan M.},
  journal = {\apj},
  title = {{Disentangling the Cosmic Web toward FRB 190608}},
  year = {2020},
  month = oct,
  number = {2},
  pages = {134},
  volume = {901},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System},
  adsurl = {https://ui.adsabs.harvard.edu/abs/2020ApJ...901..134S},
  archiveprefix = {arXiv},
  doi = {10.3847/1538-4357/abafc3},
  eid = {134},
  eprint = {2005.13157},
  keywords = {Galaxy dark matter halos, Quasar absorption line spectroscopy, Galaxy evolution, Intergalactic medium, Radio transient sources, 1880, 1317, 594, 813, 2008, Astrophysics - Astrophysics of Galaxies},
  primaryclass = {astro-ph.GA}
}

A single fast radio burst localized to a massive galaxy at cosmological distance

K. W. Bannister, A. T. Deller, C. Phillips, and 51 more authors

Science, Aug 2019

DOI Bib

@article{Bannister2019,
  author = {{Bannister}, K.~W. and {Deller}, A.~T. and {Phillips}, C. and {Macquart}, J.-P. and {Prochaska}, J.~X. and {Tejos}, N. and {Ryder}, S.~D. and {Sadler}, E.~M. and {Shannon}, R.~M. and {Simha}, S. and {Day}, C.~K. and {McQuinn}, M. and {North-Hickey}, F.~O. and {Bhandari}, S. and {Arcus}, W.~R. and {Bennert}, V.~N. and {Burchett}, J. and {Bouwhuis}, M. and {Dodson}, R. and {Ekers}, R.~D. and {Farah}, W. and {Flynn}, C. and {James}, C.~W. and {Kerr}, M. and {Lenc}, E. and {Mahony}, E.~K. and {O'Meara}, J. and {Os{\l}owski}, S. and {Qiu}, H. and {Treu}, T. and {U}, V. and {Bateman}, T.~J. and {Bock}, D.~C.-J. and {Bolton}, R.~J. and {Brown}, A. and {Bunton}, J.~D. and {Chippendale}, A.~P. and {Cooray}, F.~R. and {Cornwell}, T. and {Gupta}, N. and {Hayman}, D.~B. and {Kesteven}, M. and {Koribalski}, B.~S. and {MacLeod}, A. and {McClure-Griffiths}, N.~M. and {Neuhold}, S. and {Norris}, R.~P. and {Pilawa}, M.~A. and {Qiao}, R.-Y. and {Reynolds}, J. and {Roxby}, D.~N. and {Shimwell}, T.~W. and {Voronkov}, M.~A. and {Wilson}, C.~D.},
  journal = {Science},
  title = {{A single fast radio burst localized to a massive galaxy at cosmological distance}},
  year = {2019},
  month = aug,
  number = {6453},
  pages = {565-570},
  volume = {365},
  adsnote = {Provided by the SAO/NASA Astrophysics Data System},
  adsurl = {https://ui.adsabs.harvard.edu/abs/2019Sci...365..565B},
  archiveprefix = {arXiv},
  doi = {10.1126/science.aaw5903},
  eprint = {1906.11476},
  keywords = {ASTRONOMY, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics},
  primaryclass = {astro-ph.HE}
}