rhhd.net

Research

1) Studying the Ultra-faint Ultraviolet Galaxies at z=2 behind the lensing cluster Abell 1689

                                           Why z=2 ?

This plot from Bouwens et al. 2013 shows the star formation history up to very high redshifts (z=10.8) , the orange contour shows the dust-corrected star formation rate density.

The global starformation rate density of the universe shows a peak between 1.5 < z < 3.This era in cosmic time has been studied widely especially after Madau 1998 paper  who discussed about this issue clearly for the first time. Here you can see a nice plot of star formation history which is taken from Bouwens et al. 2013 paper.Obtaining a complete census of star formation at all epochs especially at  this important era (1.5<z<3) is one of the primary goals of observational cosmology these days.

  • Therefore my first research project was about studying the star forming galaxies at z=2.

                            Why faint galaxies?

The population of faint ultraviolet galaxies may contribute significantly to the global star formation density and the ionizing background at z>2 (See e.g, Nestor et al. 2011). This result proves the importance of these feeble objects in maintaining the ionizing emissivity especially at the peak of star formation activity.
In addition to the crucial role of the faint galaxies at lower redshifts, it is believed that low luminosity galaxies at z>7 are likely the primary sources of ionizing photons that caused the reionization of the intergalactic medium \citep{kuhlen et al. 2012 , Robertson et al. 2013}. Studying an analogous population at lower redshifts (z~2) provides a clearer picture of ultra-faint populations at high redshifts.

  • Therefore we have targeted the faint star-forming galaxies at z=2 .We selected these  galaxies by identifying the Lyman break in their spectral energy distribution (SED).
                    Why Gravitational Lensing?

These faint galaxies are mostly beyond our current detection limits. One way to efficiently detect these feeble objects is to use foreground massive  systems (e.g, clusters) as gravitational lenses to magnify the flux of the background objects.

Abell 1689, This image is composite of optical and infrared data.

  • Therefore we targeted the background galaxies behind Abell 1689 cluster. One of the main reasons that we choose the massive cluster is because it has the most constrained mass model.
For more information and the results of this project see :

 

 

 

 

 

 

2) Study of the Lyman continuum Escape Fraction of Faint Galaxies at the Peak Star Formation Rate Era.

3) Study of the Dwarf Galaxies behind the "Frontier Fields" lensing clusters