Tensor perturbations during Inflation:
With Dr. L. Sriramkumar*, I developed a python code to numerically estimate the evolution of tensor perturbations during inflation and to estimate the power spectrum of tensor power spectrum at super-Hubble scales. We studied the power spectrum of tensor perturbations during two models of inflation, namely power law inflation and inflation driven by small field potential model. Given two different forms of the potential driving inflation, we solved the background equations to solve for the evolution of the scalar field driving inflation. Using this solution, we estimate the value of tensor perturbations. A detailed report that discusses the numerical methods can be found here.
*Dept. of Physics, Indian Institute of Technology Madras, Chennai, India.
Constructing a Tully-Fisher (TF) relationship for SAMI galaxies:
With Prof. Jeremy Mould*, I reduced and analyzed integral field spectra of galaxies observed by the SAMI instrument on the AAT. We combed through the spectrum looking for H alpha emission lines and `extracted their corresponding line widths. Instead of using the HI line widths, as is conventionally done, we used the H alpha line widths to construct the TF reln. We used the SDSS r, i & z magnitudes and galactic inclinations from NED/IPAC.
During our work, we discovered double-horned H alpha emission peaks. This double horned profile is usually observed in the HI galactic emission line profile, in galaxies with large rotation velocities.
This work was presented at "The role of Hydrogen in the evolution galaxies" conference as a poster.
The process of line finding and extraction was initially done one galaxy-at-a-time but it has now been automated using a python script. Further analysis & visualization was also done using python.
*Center for Astrophysics & Supercomputing, Swinburne University of Technology, Melbourne, Australia.
Observing the Pulsar PSR B1749-28:
As part of the POS* program, I observed the pulsar PSR B1749-28 using the ORT at the frequency 326.5 MHz with a bandwidth of 16 Mhz. I reduced the data using the SIGPROC package and studied the period, strength and the dispersion measure of the pulsar. They were measured to within an error of 5%. My presentation at the end of the school can be found here
Going beyond the usual measurements, I studied the frequency response of the telescope to the calibrator. Ideally, this is a homogenous function and any deviation from homogenity should be accounted for while data reduction. This inhomogenity can creep into the measurement of strength the pulsar and lead to errors. Upon enquiry, I was informed that this problem was infact being corrected in the current update cycle.
I also attended talks on pulsar science during the observation cycle.
* Pulsar Observatory for Students, organized by NCRA-TIFR at the Ooty Radio Telescope (ORT).
Color-Redshift relation for Quasars from the SDSS :
Under the guidance of Prof. Anand Narayanan*, I studied Quasars and their spectral properties. I constructed color-color and color-redshift plots for 146,659 quasars from the SDSS DR9. The color-redshift relation follows roughly the same trend as that from Richards et al. (2001) on the "Colors of Quasars from the 2625 SDSS", albiet larger variance thanks to the bigger data set. A mean color-redshift relation was inferred and a simulated color-redshift relation was constructed using the composite quasar spectrum from Vandenberk et al. (2001).
Vertical features can be noticed in the color-redshift plots which upon further enquiry turned out to be M type stars. This was spectrally confirmed. Such false positives are known to creep through the automated pipeline and for a pure quasar sample, one should use Paris et al. (2014).
I queried the SDSS DR9 for quasar data using SQLquery and data analysis & visualisation was done using python.
* Dept. of Earth & Space Sciences, Indian Institute for Space science & Technology, Trivandrum.
Polarimetric study of Stock 8 :
During the ATSOA*, as part of a team of 4, I reduced and analyzed polarimetric data of the star forming region Stock 8 in the constellation Auriga. The observations were made using the ARIES Imaging Polarimeter (AImPol) instrument on the Sampurnanand telescope, ARIES.
We inferred the average size of the dust grains in the region and the orientation of the magnetic field.
Data reduction was done using IRAF routines, analysis & visualation were done using IDL. Our presentation made at the end of school can be found here
* ARIES Training School in Observation Astronomy, Aryabhatta Research Institute for observational sciencES, Nainital, India.
IIST Astronomy & Astrophysics School :
Over the course of 10 days, we were introduced to various theoretical aspects of Astronomy, ranging from Star formation & Evolution, Galactic & extragalactic astronomy and techniques of observational astronomy such as astrometry, photometry, spectroscopy, polarimetry and interferometry.