Tirthankar Roy Choudhury

Associate Professor G
Email: tirth [at] ncra.tifr.res.in
Phone: +91 - 20 - 25719270
Extn: 9270
Office: F236
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Savitribai Phule Pune University Campus,
Pune 411 007
Maharashtra, INDIA

Main Research Areas: Reionization, Intergalactic Medium, Dark Energy.



Tirthankar Roy Choudhury did his B.Sc. and M.Sc. from Visva Bharati University, Santiniketan, India. Following this, he joined IUCAA for his Ph.D., during which he worked on aspects of cosmological structure formation and dark energy. After completing his Ph.D. in 2003, he went for a couple of postdoctoral fellowships at SISSA (Trieste, Italy) and Institute of Astronomy (Cambridge, UK). He returned to India in 2008 as a faculty member at the Harish-Chandra Research Institute, Allahabad. In 2012 he moved to NCRA and has been there since. For further information, please take a look at his resume [http://www.ncra.tifr.res.in:8081/~tirth/resume_web.html].

Research description:

My research interests lie in various aspects of theoretical astrophysics and cosmology, in particular, reionization, intergalactic medium, neutral hydrogen at high redshifts and dark energy. At present, I devote most of my time studying a cosmological process called "reionization"
In the framework of the hot big bang model, our Universe is expected to become almost neutral around 400,000 years after the big bang. On the other hand, we know from observations of quasar absorption spectra that the same Universe has become highly ionized by the time it is one Gigayear old. This implies that the Universe must have been "reionized" sometime in between. As per our current understanding, the reionization of the Universe is driven by radiation from first luminous sources (galaxies/stars). Studying reionization will thus tell us how the first stars formed and how different they were from stars we see around us. In addition, reionization is extremely important for studying cosmology in general as the details of it affects determination of cosmological parameters from observations. For more details on what I work on, please take a look at my research page [http://www.ncra.tifr.res.in:8081/~tirth/research.html].

Selected publications:

1: Constraining thawing dark energy using galaxy cluster number counts (N. Chandrachani Devi, T. Roy Choudhury, & Anjan A. Sen 2013, MNRAS, 432, 1513)

2: Joint quasar-cosmic microwave background constraints on reionization history (S. Mitra, T. Roy Choudhury & A. Ferrara 2012, MNRAS, 419, 1480)

3. Inside-out or outside-in: the topology of reionization in the photon-starved regime suggested by Lyα forest data (T. Roy Choudhury et al. 2009, MNRAS, 394, 960)

4: Searching for the reionization sources (T. Roy Choudhury & A. Ferrara 2007, MNRAS, 380, L6)

5: Constraining the reionization history with QSO absorption spectra (S. Gallerani, T. Roy Choudhury & A. Ferrara 2006, MNRAS, 370, 1401)

6: Updating reionization scenarios after recent data (T. Roy Choudhury & A. Ferrara 2006, MNRAS, 371, L55)

7: Experimental constraints on self-consistent reionization models (T. Roy Choudhury & A. Ferrara 2005, MNRAS, 361, 577)

8: Cosmological parameters from supernova observations: A critical comparison of three data sets ( T. Roy Choudhury & T. Padmanabhan 2005, A&A, 429, 807)

9: A theoretician's analysis of the supernova data and the limitations in determining the nature of dark energy (T. Padmanabhan & T. Roy Choudhury 2003, MNRAS, 344, 823)

10: Can the clustered dark matter and the smooth dark energy arise from the same scalar field? (T. Padmanabhan & T. Roy Choudhury 2002, Phys. Rev. D, 66, 1301)