Abstract Details
| Name: PRAKASH SURYAKANT GAIKWAD Affiliation: NATIONAL CENTRE FOR RADIO ASTROPHYSICS Conference ID: ASI2015_479 Title : Signatures of Helium reionization in Quasar Absorption Spectra Authors and Co-Authors : Tirthankar Roy Choudhury (NCRA), R. Srianand (IUCAA), Vikram Khaire (IUCAA) Abstract Type : Poster Abstract Category : General Relativity and Cosmology Abstract : At present it is believed that the reionization of singly-ionized helium (HeII) occurred around redshifts $z \sim 3$ because of the rise in quasar population. This alters the thermal state of the intergalactic medium (IGM), in particular it leads to a rise in the temperature. Thus the study of thermal evolution of IGM can provide useful insight about its ionization state. Because of reionization of HeII, the mean temperature $T_0$ and the equation of state $\gamma$ of the IGM is expected to change considerably. It is expected that one can understand these effects by studying the thermal broadening of absorption lines in the Ly$\alpha$ forest of quasar absorption spectra. In this talk we present the constraints on $T_0$ and $\gamma$ using simulations of Ly$\alpha$ forest and comparing with high resolution observations of quasar absorption spectra. The method for putting constraints is based on wavelet analysis of Ly-$\alpha$ forest transmitted flux and optical depths. The probability distribution function of wavelet power is used as calibrator between observed and simulated spectra. We have verified our method by applying it on simulated test spectra ($T_0$ and $\gamma$ are known). The method is then applied on observed spectra for different redshift bins so that the redshift evolution of $T_0$ can be constrained. We find that the constraints can be improved if one uses optical depth reconstructed from HI Ly-$\alpha$ forest instead of HI Ly-$\alpha$ transmitted flux. We have studied how the constraints depend on systematics such as noise, number of spectra, cosmic variance, metal line contamination etc. |