My CV is available here for download in PDF.

Dr. Nithyanandan Thyagarajan

Arizona State University, School of Earth and Space Exploration, Tempe, AZ 85287, USA
E-mail: t_nithyanandan@asu.edu
Phone: +1 (480) 727-2567

Education

2004-2011
PhD in Astronomy, Columbia University, New York, NY, USA
Thesis Advisor: Prof. David J. Helfand
My PhD Thesis for download.
2006-2007
M.Phil. in Astronomy, Columbia University, New York, NY, USA
2004-2006
M.A. in Astronomy, Columbia University, New York, NY, USA
2000-2004
Bachelor of Technology in Electrical Engineering, Indian Institute of Technology – Madras, India

 

Employment

Sep 2013 – Present
Post-doctoral Research Associate
May 2011 – Jul 2013
Post-doctoral Fellow
Collaborations: Murchison Widefield Array (MWA)

 

Fellowships and Awards

  • 2011-2013:  Pancharatnam Fellow – Raman Research Institute, Bangalore, India
  • 2006-2011:  Graduate Research Fellow – Columbia University, New York, NY USA
  • 2004-2006: Faculty Fellow – Columbia University, New York, NY USA
  • 1998-2004: National Talent Search Scholar, India

 

Research Experience

2015 – Present
  • Generic and Efficient E-field Parallel Imaging Correlator (EPIC)
Collaborators: Prof. Judd Bowman (ASU), Prof. Miguel F. Morales (UW) & Adam Beardsley (ASU).
A software tool that implements a generic direct imaging algorithm, namely Modular Optimal Fast Fourier (MOFF) imaging, which is a generic and efficient alternative to conventional correlator (FX/XF) and imaging techniques currently in use in radio interferometry. Data processing including calibration and imaging use antenna-based electric fields without the need for cross-correlating antenna pairs to produce visibilities. It also relaxes the constraints that antennas have to be placed on a uniform grid for direct imaging and that the antennas must be identical. EPIC has a promising future for next-generation radio telescopes that have a dense, large-N antenna array layout such as HERA, LWA and SKA. An immediate-term science driver is the real-time search for radio transients. Work is underway to realize a GPU-based implementation of EPIC for HERA-19.
  • Forecast of EoR HI signal and foregrounds for HERA
Collaborators: Prof. Judd Bowman & HERA Collaboration.
Using high precision simulations, characterizing chromaticity of the antenna beam and its performance, forecasting detection sensitivity and best windows in observing parameters for EoR HI observations using the Hydrogen Epoch of Reionization Array (HERA), a top ranked project in the Astro2010 Decadal survey. Parameters such as foreground mitigation through instrument design aspects such as antenna aperture design and data analysis aspects such as baseline-based flagging methods and direction-dependent foreground removal strategies will be considered in identifying the best observing strategy for HERA.
2013 – 2015
  • Confirming predicted wide-field instrument and foreground signatures in EoR observations
Collaborators: Prof. Judd Bowman (ASU), Daniel Jacobs (ASU) & MWA Collaboration.
First and high-significance confirmation (using MWA data) of the pitchfork signature characteristic of foregrounds in EoR observations with wide-field instruments predicted earlier thus emphasizing the need for clever aperture designs with desirable antenna power patterns that suppress instrument sensitivity near the horizon for future instruments such as HERA and SKA.
  • Prediction of characteristic EoR foreground signatures observed by radio interferometers
Collaborators: Prof. Judd Bowman (ASU), Daniel Jacobs (ASU) & MWA Collaboration.
First detailed simulations of EoR signal and foregrounds as observed through radio interferometer arrays helped discover that wide-field instruments imprint a characteristic pitchfork signature in the power spectrum “wedge” – a signature which critically affects EoR signal sensitivity in important k-modes. Contamination from the pitchfork feature can be controlled by careful design of antenna apertures that suppress power pattern near the horizon and by using a sky model and baseline-based flagging technique. Simulations are publicly available for the radio astronomy community.
2011 – 2013
  • Statistical Foreground Modeling and EoR Sensitivity for the MWA
Collaborators: Prof. Ravi Subrahmanyan (RRI), Prof. Udayashankar (RRI) & MWA Collaboration.
Understanding fundamental limitations to EoR detection in HI power spectrum – classical source
confusion, sidelobe confusion, and thermal noise – thereby estimating sensitivity of radio instru-
ments such as MWA in EoR experiments with implications for observing strategies.
  • GMRT and PTF follow-up of VLA FIRST transients
Collaborators: Prof. K. S. Dwarakanath (RRI) & Prof. Shri Kulkarni (Caltech)
Follow-up of ≳ 1600 variables and transients from the FIRST survey with the Palomar Transient Factory in the optical bands and 20 carefully chosen bright transients at low radio frequencies with the GMRT thereby characterizing the dynamic radio sky.
2007 – 2011
  • Radio variables & transients from the VLA FIRST survey
Collaborators: Prof. David J. Helfand (Columbia University), Prof. Richard L. White (STScI) & Prof. Robert H. Becker (UC Davis)
One of the biggest searches for radio variables and transients at mJy levels using the FIRST survey, constructing statistics of the variable/transient radio sky and probing unexplored regions of parameter-space in discovering new types of variable and transient objects.
2005 – 2007
  • Angular size-redshift analysis from VLA FIRST data using FR-II sources
Advisor: Prof. David J. Helfand, Columbia University.
Verified that FR-II quasars behave as standard rods without intrinsic redshift evolution by assuming the currently accepted cosmological parameters and by using a combination of FIRST images and SDSS spectroscopic and photometric redshifts thereby creating the largest and homogeneous database of radio selected FR-II quasars.
  • Angular correlation of radio sources in the FIRST survey
Advisor: Prof. David J. Helfand, Columbia University.
Studied the angular correlation of radio sources down to mJy levels and using higher order statistics to study the radio clustering properties of the universe with optical magnitudes available from SDSS.
2004 – 2005
  • HI in the Perseus cluster using WSRT
Advisor: Prof. Jacqueline van Gorkom, Columbia University.
Investigated HI in selected galaxies sampling the inner and outer regions of the Perseus cluster using the data with the new WSRT back-end and also studying the two HI absorptions at the center of the cluster which are not very well understood.
2003
  • Understanding the performance of NNLS algorithm in synthesis imaging
Advisors: Prof. Rajaram Nityananda, NCRA, Pune, India & Prof. Harishankar Ramachandran, IIT, Madras, India.
Experimented with the Non-Negative Least Squares algorithm assessing its performance and efficiency and compared to the CLEAN algorithm.
2002
  • Gravitational Waves in the linearized theory of gravity
Advisor: Prof. Bala R. Iyer, RRI, Bangalore, India.
Performed simulations of test particles under the influence of gravitational waves in the linearized
theory of gravity.

 

Publicly Released Software

A generic and efficient and highly parallel antenna electric field-based correlator-cum-imaging software demonstrator for next generation radio telescopes developed in Python and publicly available on github.
A generic and highly parallel radio interferometer array simulator for modern wide-field radio telescopes using all-sky models developed in Python and publicly available on github.
General purpose modules that serve miscellaneous purposes such as signal and image processing, nearest neighbor and catalog matching, and function as dependencies for the aforementioned software packages. These modules can be found on github.

 

Programming Skills

      Python   IDL   MATLAB   C++   LATEX   MS Office

 

Publications

As one of primary authors

2015
Thyagarajan, N., Bowman, J. D., et al. To be submitted to The Astrophysical Journal.
“Forecast of Redshifted HI Signal and Foregrounds in EoR Observations Using HERA”
2015
Thyagarajan, N., Beardsley, A. P., Bowman, J. D., & Morales, M. F.
To be submitted to the Monthly Notices of the Royal Astronomical Society.
“GenericandEfficientE-field ParallelImagingCorrelatorforNext-GenerationRadioTelescopes”
2015
Beardsley, A. P., Thyagarajan, N., Morales, M. F., & Bowman, J. D.
To be submitted to the Monthly Notices of the Royal Astronomical Society.
“Calibrating Radio Arrays without Visibilities Using the E-field Parallel Imaging Calibration”
2015
Thyagarajan, N., Jacobs, D. C., Bowman, J. D., et al.
The Astrophysical Journal Letters, 807, 28
2015
Thyagarajan, N., Jacobs, D. C., Bowman, J. D., et al.  The Astrophysical Journal, 804, 14
2013
Thyagarajan, N., Udaya Shankar, N., Subrahmanyan, R., et al.
The Astrophysical Journal, 776, 6
2011
Thyagarajan, N., Helfand, D. J., White, R. L., & Becker, R. H.
The Astrophysical Journal, 742, 49

 

As collaborating author

2015
Ewall-Wice, A., Dillon, J. S., … Thyagarajan, N., et al. [65 authors]
Submitted to the Monthly Notices of the Royal Astronomical Society.
“First Limits on the 21 cm Power Spectrum during the Epoch of X-ray heating”
2015
Pober, J. C., Hazelton, B. J., … Thyagarajan, N., et al. [68 authors]
Submitted to The Astrophysical Journal
“First Limits on the 21 cm Power Spectrum during the Epoch of X-ray heating”
2015
Dillon, J. S., Neben, A. R., … Thyagarajan, N., et al. [55 authors]
Physical Review D, 91, 123011
2015
Offringa, A. R., Wayth, R. B., … Thyagarajan, N., et al. [65 authors]
Publications of the Astronomical Society of Australia, 32, 8

 

Collaborations (Present and Past)

Prof. Judd D. Bowman                          Arizona State University, Tempe, AZ, USA
Prof. Chris Carilli                                 National Radio Astronomy Observatory (NRAO), Socorro, NM, USA
Prof. Greg Taylor                                 University of New Mexico, Albuquerque, NM, USA
Prof. Miguel F. Morales                       University of Washington, Seattle, WA, USA
Prof. Ravi Subrahmanyan                    Raman Research Institute, Bangalore, India
Prof. David J. Helfand                          Columbia University, New York, NY, USA
Prof. Jacqueline van Gorkom               Columbia University, New York, NY, USA
Prof. Richard L. White                         Space Telescope Science Institute, Baltimore, MD, USA
Prof. Rajaram Nityananda                   National Centre for Radio Astrophysics, Pune, India
Prof. Robert H. Becker                         University of California, Davis, CA, USA
Prof. N. Udayashankar                         Raman Research Institute, Bangalore, India
Prof. Harishankar Ramachandran        Indian Institute of Technology – Madras, India
Prof. Bala R. Iyer                                  Raman Research Institute, Bangalore, India

 

Conferences and Talks

Jan. 2017
National Radio Science Meeting (URSI), Boulder, CO, USA
Enabling Detection of the Epoch of Reionization With Next-generation Radio Instruments
Dec. 2016
MWA Project Meeting, California Institute of Technology (Caltech), Pasadena, CA, USA
To be decided.
Dec. 2016
Science at Low Frequencies III, California Institute of Technology (Caltech), Pasadena, CA, USA
To be decided.
Oct. 2016
HERA Collaboration Meeting, MIT, Cambridge, MA, USA
To be decided.
Oct. 2016
CALIM 2016, National Radio Astronomy Observatory (NRAO), Socorro, NM, USA
Jul. 2016
University of Edinburgh Seminar, University of Edinburgh, Edinburgh, UK
Jun. 2016
Invited Talk, 21cm Cosmology Workshop, University of Cambridge, Cambridge, UK
Jun. 2016
Imperial College Seminar, London, UK
Jun. 2016
Oxford University Seminar, Oxford, UK
Mar. 2016
The Reionization Epoch: New Insights and Future Prospects, Aspen, CO, USA
Jan. 2016
Invited Colloquium, National Radio Astronomy Observatory, Socorro, NM, USA
Jan. 2016
National Radio Astronomy Observatory Seminar, Socorro, NM, USA
Jan. 2016
URSI National Radio Science Meeting, Univ. of Colorado – Boulder, CO, USA
Dec. 2015
Canadian SKA Meeting, Univ. of Toronto, Toronto, Canada
Dec. 2015
MWA Project Meeting, Univ. of Toronto, Toronto, Canada
Dec. 2015
Science at Low Frequencies II, Albuquerque, NM, USA
Oct. 2015
Seminar, University of Washington, Seattle, WA, USA
Oct. 2015
Seminar, University of California, Los Angeles, CA, USA
Oct. 2015
Preparing for the 21-cm Cosmology Revolution, University of California, Irvine, CA, USA
Jun. 2015
Conference on Reionization – A Multi-Wavelength Approach, Kruger Park, South Africa
Mar. 2015
Seminar at National Optical Astronomy Observatory, Tucson, AZ, USA
Jan. 2015
American Astronomical Society Meeting, Seattle, WA, USA
Dec. 2014
Meeting on Early Science from Low-frequency Radio Telescopes, Tempe, AZ, USA
Dec. 2014
MWA EoR (USA) Project Meeting, Tempe, AZ, USA
Nov. 2014
HERA Kickoff Meeting, University of California, Berkeley, CA, USA
Oct. 2014
Columbia University Seminar, New York, NY, USA
Jul. 2014
Raman Research Institute Seminar, Bangalore, India
Jun. 2014
MWA EoR (USA) Project Meeting, University of California, Berkeley, USA
Aug. 2012
Joint Indo-South Africa Workshop on Astronomy, Cape Town, South Africa
Study of Foregrounds and Limitations to EoR Detection
Jun. 2012
MWA Project Meeting, Bangalore, India
Apr. 2012
National Centre for Radio Astrophysics Seminar, Pune, India
Feb. 2012
Curtin University Seminar, Perth, Australia
Jul. 2011
Raman Research Institute Seminar, Bangalore, India
Variables and Transients in the VLA FIRST Survey
Dec. 2008
Low Frequency Radio Universe, NCRA, Pune, India
A Comprehensive Search for Variables and Transients in the VLA FIRST Survey
Jun. 2006

Summer Synthesis Imaging Workshop, Albuquerque, NM, USA

Jun. 2005

Wide Field Imaging, Dwingeloo, The Netherlands

Jun. 2003

Visiting Summer Research Programme, NCRA, Pune, India

Jun. 2003

Synthesis Imaging school, NCRA, Pune, India

Jun. 2002

Visiting Summer Research Programme, RRI, Bangalore, India

 

Public Outreach

2013 – Present:   ASU Earth & Space Open House, ASU, Tempe, AZ, USA
2011 – 2013:      Global Jet Watch project, Raman Research Institute, Bangalore, India
2004 – 2011:      Columbia University Public Outreach, Columbia University, New York, NY, USA

 

Teaching

Fall 2007:       TA for the course Introduction to Astrophysics I.
Spring 2007:   Instructor for lab course  Beyond the Solar system
Fall 2006:        Instructor for lab course Earth, moon and planets
Spring 2006:   Instructor for lab course Beyond the Solar system
Fall 2005:        Instructor for lab course  Earth, moon and planets
Spring 2005:   TA for lab course Beyond the Solar system
Fall 2004:        TA for lab course Earth, moon and planets
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