Abstract Details

Name: Sachin P C
Affiliation: Indian Institute of Space Science and Technology
Conference ID: ASI2017_1146
Title : Detection of Two Intervening Ne VIII Absorbers Probing Warm-Hot Gas at z > 0
Authors and Co-Authors : Anand Narayanan, Indian Institute of Space Science & Technology, Thiruvananthapuram Blair D. Savage, The University of Wisconsin-Madison, USA Vikram Khaire, National Centre for Radio Astrophysics, Pune Sowgat Muzahid, The Pennsylvania State University, United States Bart P. Wakker, The University of Wisconsin-Madison, USA
Abstract Type : Oral
Abstract Category : Extragalactic astronomy
Abstract : Physical conditions of IGM in the early universe is dominated by the radiations from the luminous source such as galaxies and AGN. During the formation of structures, significant changes occurred in the ionisation conditions and phase structures of CGM/IGM gas. The low redshift baryonic surveys suggest that a large fraction of these baryons are missing in their most common reservoir such as Lyman alpha forest, cold matter etc. Cosmological hydrodynamic simulations of structure formation agree with this predicts a significant fraction of baryons within temperature 10^5 - 10^6 K which produce only a broad but shallow absorption(BLA). The absorp- tions lines from the highly ionised metal lines such as Ne viii, O VI, Mg X detected in the distant QSO spectra is the proven method to study this region. In this work, we report on the detection of two intervening Ne viii absorbers at z > 0 in the HST/COS spectrum of high redshift quasars. Both the absorbers include higher ionisa- tion lines of O VI, Ne VIII, intermediate lines of C III, N IV, O IV and S IV, but only one of the system has lower ions ( C II ) detected. A pure photoionization modelling can explain the observed line ratios in the first absorber (with lower ions) except for Ne VIII where the Ne VIII is likely coming from a completely different warm-hot phase of the IGM. In the second absorber (without lower ions), all the lines detected and their ratios are consistent with a single phase hybrid ionisation scenario at temperature T ~ 10^5 K. From the SDSS survey, we detected several galaxies within the vicinity of these absorbers. One of the absorbers detected is within the virial radii of the nearest galaxy could be the gas in the halo of the galaxy whereas the second absorber does not show any galaxy association could be the gas in the circumgalactic region or may be associated with galaxies within the limit of SDSS detection.