Abstract Details
| Name: Sharmila Ghosh Affiliation: Senior Research Fellow Conference ID: ASI2017_514 Title : A multiwavelength approach to the evolution of cold gas from quasar absorption lines Authors and Co-Authors : Dr. Mina Ray Assistant Professor Abstract Type : Poster Abstract Category : Extragalactic astronomy Abstract : One of the key questions in modern astrophysics is to understand how the star formation in galaxies proceeds and leads to the present-day Universe. Quasars (quasi-stellar radio sources) are the most energetic and distant members of the objects known as active galactic nuclei (AGN). As Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, their spectra contain very broad emission lines hence they are suitable to study a multiwavelength approach to the evolution of cold gas from quasar absorption lines. In recent years, radio and optical observations of the local Universe have established a strong relationship between the star formation rate and the properties of the cold atomic and molecular gas in galaxies. Although the overall star-formation history of the Universe is known to very high redshifts, very little is known about the evolution of cold gas beyond the local Universe. An unbiased census of the cold gas in normal galaxies, irrespective of their physical properties such as morphology and mass, is required to understand the physical processes that control the evolution of the star formation history of the Universe. Even we are interested to unravel the evolution of cold gas in galaxies through the quasar absorption line technique. Specifically, at radio wavelengths for the first most sensitive search of cold gas absorption lines using South Africa’s Square Kilometer Array (SKA) precursor, the MeerKAT radio telescope, starting in 2016. Mapping HI emissions with a radio telescope is a technique used for determining the structure of spiral galaxies. HI regions effectively absorb photons that are energetic enough to ionize hydrogen, which requires energy of 13.6 electron volts. Importance and main focus of the study is to carry out the blind search of HI 21-cm and OH absorption lines through the MeerKAT Absorption Line Survey (MALS). The hydrogen line 21 cm or HI line refers to the electromagnetic radiation spectral line that is created by the transition of electron between two lower energy states of hydrogen atoms. Neutral hydrogen could produce radiation at a frequency of 1420.4 MHz due to two closely spaced energy levels in the ground state of the hydrogen atom. The electromagnetic radiation is at the precise frequency of 1420 MHZ, which is equivalent to the vacuum wavelength of 21 cm in free space. This wavelength falls within the microwave radio region of the electromagnetic spectrum, and observed frequently in radio astronomy because those radio waves can penetrate the large clouds of interstellar cosmic dust that are opaque to visible light. |