Paurush Punyasheel

Visted the Cosmic Dawn Center housed at Technical University of Denmark, while working on my Masters' thesis. Actively took part in workshops, guest lectures and daily activities of the DAWN DTU team.

We use the First Light And Reionisation Epoch Simulations (FLARES) to study the evolution of the rest-frame ultraviolet (UV) and far-infrared (FIR) sizes for a statistical sample of massive (≳ 10^9M⊙) high redshift galaxies (z ∈ [5, 10]). Galaxies are post-processed using the skirt radiative transfer code, to self-consistently obtain the full spectral energy distribution and surface brightness distribution. We create mock observations of the galaxies for the Near Infrared Camera (NIRCam) to study the rest-frame UV (1500 Å) morphology. We also generate mock rest-frame FIR (50 μm) photometry and mock ALMA 158 μm (0.01′′ − 0.03′′ and ≈0.3′′ angular resolution) observations to study the dust-continuum sizes. We find the effect of dust on observed sizes reduces with increasing wavelength fromthe UV to optical (∼ 0.6 times the UV at 0.4μm), with no evolution in FIR sizes. Observed sizes vary within 0.4−1.2 times the intrinsicsizes at different signal to noise ratios (SNR = 5-20) across redshifts. The effect of PSF and noise makes bright structures prominent, whereas fainter regions blend with noise, leading to an underestimation (factor of 0.4 − 0.8) of sizes at SNR=5. At SNR=15-20, the underestimation reduces (factor of 0.6 − 0.9) at z = 5 − 8 but due to PSF, at z = 9 − 10, bright cores are dominant, resulting inan overestimation (factor of 1.0-1.2) of sizes. For ALMA, low (≈0.3′′) resolution sizes are effected by noise which acts as extended emission. The size evolution in UV broadly agrees with current observational samples and other simulations. This work is one of the first to analyse the panchromatic sizes of a statistically significant sample of simulated high-redshift galaxies, complementing agrowing body of research highlighting the importance of conducting an equivalent comparison between observed galaxies and their simulated counterparts in the early Universe.

Using the First Light And Reionisation Epoch Simulations (FLARES), we compare the morphological properties for a statistical sample of massive ($\gtrsim10^{9}$M$_{\odot}$) high redshift galaxies ($z \in [5,10]$) in the ultraviolet (UV) and infrared (IR) spectrum. We post-process the sample of galaxies using the SKIRT radiative transfer code, to obtain the full spectral energy distribution and surface brightness distribution. We create mock observations of the galaxies for the Near Infrared Camera (NIRCam) to study the rest-frame UV (1500 \AA) morphology. We also generate mock rest-frame FIR (50 \um) photometry and mock ALMA 158 \um\ ($\approx$$0.3''$ angular resolution) observations to study the dust-continuum of the galaxies. Nearly 5\% of the galaxies have an offset of $\geq 2$ kpc between their IR and UV observed centers. The centers are defined as the point on which asymmetry is minimised for the brightest source in an image. This offset seems independent of luminosities in UV and IR as well as dust properties of the galaxies and rather correlates very well with clumpiness. We fit Sérsic profiles to our UV observations and extract clumps in the Sérsic residual images. These clumps are bright and have a high signal to noise ratio. Number of clumps in a galaxy correlates very well with the specific Star Formation Rate (sSFR). Clumpiness in these galaxies shows no dependence on the environment.

Worked on my thesis at the Cosmic Dawn Center housed at Technical University of Denmark, using forward modeled ultra high redshift galaxies in hydrodynamical simulation (FLARES). Post processed the galaxies using SKIRT radiative transfer code to mock NIRCAM \& ALMA observations. Studied the size and structure evolution of galaxies in a high redshift universe with cosmic time. Observational Sizes have a substantial inaccuracy compared to actual sizes. Further studied the nature and abundances of dust by comparing the IR and UV continuum. Also investigated the environmental effects on the morphological and spatial properties of the galaxies.

Worked on image analysis on the data provided by PanSTARRS Observatory at University of Hawaii in a citizen scientist effort. Used Astrometrica, a scientific grade astrometric data reduction tool for CCD images, to analyze moving objects in the observations, and identify possible asteroids with one successful preliminary discovery.

Worked on a CubeSat (EINSAT) at my university, which aims to be deployed to low-earth orbit and monitor stars to detect exoplanet transits by precision photometry. Focused on developing and simulating photometric reduction procedures, and computing standards to cope with low downlink rates.