Abstract Details
| Name: Sunil Affiliation: University of Delhi Conference ID: ASI2018_921 Title : Probing magnetic field in the intervening galaxies using residual rotation measure (rrm) of the background quasars. Authors and Co-Authors : Hum Chand (ARIES, Nainital,India) T. R. Seshadri (Department of Physics and Astrophysics, University of Delhi, India) Abstract Type : Poster Abstract Category : Extragalactic astronomy Abstract : A method to probe the magnetic fields of the high-redshift galaxies using the residual rotation measure of the extragalactic sources is presented. To carry out this analysis, a large sample of 970 quasars is compiled for which we have residual rotation measure (rrm) data as well as optical spectra to check the presence/absence of the intervening Mg II absorbers. We have found that the dispersion in RRM (σ-rrm ) for 294 sightlines having Mg II intervening systems is 45.91±2.04 rad m −2 as compared to its value of 21.47±1.93 rad m −2 for the 676 sightlines without such absorbers. This lead to significant excess in the standard deviation of 40.57±2.52 rad m −2 among these two subsamples. In this work, we have also shown that subset of sightlines with two Mg II absorbers have more σ-rrm than the subset with one absorber, having values of 35.62±4.63 rad m −2 and 28.28±2.35 rad m −2 , respectively and this sigma rrm has an increasing trend for larger rest frame equivalent width (EW), having values 40.48±2.71 rad m −2 and 55.53±3.18 rad m −2 for EW <1 A and EW > 1 A , respectively. Additionally, we found a strong anti-correlation between σ rrm and fractional polarisation (p) with the Pearson correlation coefficient (Ï) of −0.78 for sightlines with Mg II absorbers which is absent for sightlines without any Mg II absorber. All these observational evidences, allows us to conclude that these intervening galaxies do have magnetic field with strength similar to that in nearby galaxies, and perhaps oriented in random directions leading to a scatter in rrm and hence also causing a reduction in the resultant fractional polarization. |