Sharif Digital Repository

The luminosity gap between the two brightest galaxies of the galaxy groups and clusters is a statistics criteria for studying the time of the formation of these gravitational systems. So far, the luminosity gap of galaxy systems is studied in local universe (z~0). This parameter is a good criteria to understand the structure formation models. In this project we investigate the evolution of luminosity gap statistic in high redshift universe (z~0.4). The evolution of luminosity with redshift is a proper tool for investigating the evolution of galaxies in different environments during the time  

Fossil galaxy groups, famed to have undisturbed inter-galactic gas due to lack of recent group scale mergers, are energetically and morphologically ideal environments to study the IGM heating. In this article, we study the role of active galactic nuclei in heating the IGM in a sample of five fossil galaxy groups by employing their GMRT observations at 610 MHz and 1.4 GHz. We find that only two of the dominant galaxies in fossil groups are associated with the radio lobes. We evaluate the PdV work of the radio lobes and their corresponding heating power and compare to the X-ray emission loss within cooling radius. Our results show that the power due to mechanical heating is not sufficiently... 

During the past decades, structural parameters are used as a tool for studying the formation and evolution of galaxies. Sersic parameter is one of these parameterswhich also known as shape parameter. Sometimes, measuring such parameters depend on the observed wavelength. So far, this dependence has been rarely attended. In this thesis we are trying to know how and why these parameters depend on the wavelength  

We study the fundamental and the photometric plane of a sample of 50 dwarf galaxies within the core of Coma cluster observed with DEIMOS on Keck II down to R-band luminosity of -15 Magnitudes. The Calcium triplet lines in the wavelength range between 7500 to 10,000 ˚A, allow us to obtain the velocity dispersion for the sample galaxies with high precision. We also performed a comprehensive error analysis to better estimate the uncertainties of this key observable. We also carried out a galaxy structure modeling using the ACS I-band images for a larger sample. We found larger velocity dispersions for fainter dwarfs than what expected from mass-luminosity trends of brighter Coma galaxies. In... 

Functional design of coating system for the primary mirror of the Iranian National Observatory (INO) is done. This telescope has a 3.4 m primary mirror in diameter, made of Zerodur from Schott. Although similar coating systems are in use since years ago, this is the first attempt to design a system for such a large surface case in Iran. Systematic approach led us first to clarify and identifying the design requirements. Lower limit of 80% for reflectance on all wavelength range from 325-1000 nm, thickness of 100 nm with un-uniformity of 5 nm, adhesion enough to pass the selotape test and surface roughness of less than 8 nm. Study of the available methods for coating and selection of the best... 

We present a new high signal to noise ratio spectroscopic survey of the Northern hemisphere to probe the Local Bubble and its surroundings using the 5780Å and 5797Å Diffuse Interstellar Bands (DIBs). We have observed 432 sightlines to a distance of 200 pc over a duration of 3 years. In this study, for both inside and outside the Local Bubble, we establish the 5780and 5797correlations with Na i, Ca iiand E(B-V). The correlations show that among all neutral and ionized atoms, the Na ihas more similarity with 5780and Ca iihas strong correlation with 5797, which suggest that the ionization level of 5797is more than 5780. We study the 5780correlation with 5797, which shows a tight correlation...