Abstract Details

Affiliation: ARIES, NAINITAL
Conference ID: ASI2017_570
Title : First observational measurement of magnetic field strengths in ISM of early- type galaxies
Authors and Co-Authors : Amitesh Omar ARIES, Nainital
Abstract Type : Oral
Abstract Category : Extragalactic astronomy
Abstract : The magnetic field strengths are constrained observationally for the first time in the inter stellar medium (ISM) of early-type galaxies (elliptical and lenticular; ETGs) using 1.4 GHz radio continuum. A large number of blue ETGs were detected in the Sloan Digital Sky Survey (SDSS), based on their optical colors. We used the sample of blue ETGs in which the emissions are primarily due to star-forming activities without any significant contribution from active galactic nuclei. We found a remarkable correlation between the radio emission and the far-infrared emission in star-forming ETGs, similar to star-forming late-type (spiral and irregular) galaxies. The positive radio-far infrared correlation in ETGs implied that the radio emission is primarily from the synchrotron process, which allowed us to estimate magnetic field strengths assuming equipartition between cosmic rays and magnetic field energy densities. The average magnetic field strength in the ISM of ETGs is estimated as ∼ 10μG, which is similar to the large-scale magnetic fields in spiral galaxies. It is proposed that magnetic fields are amplified in occasional star-bursts and subsequently regularized and sustained over long periods in ETGs in some dynamical components such as rings.