Dr. Steve Curran (University of New South Wales)

A Systematic Search for Highly Redshifted Radio Absorption Lines - Dr. Steve Curran Colloquium

ATNF Marsfield Lecture Theatre

Abstract

I shall discuss my current research of searching for HI 21-cm, OH
18-cm and millimetre absorption lines at high redshift. Such lines
have many applications in the study of the early Universe, from
galactic formation and evolution to the measurement of variations in
the fundamental constants of Nature. I will briefly discuss the
latter, although the emphasis shall be on the interesting
observational results obtained thus far:

1. Targetting searches towards damped Lyman-alpha absorption systems
(DLAs) occulting compact radio continua may increase the 21-cm
detection rate, in spite of apparently high spin temperatures at
high redshift.

2. However, molecular transitions (particularly at millimetre
wavelengths) are expected to remain undetected in DLAs, although
targetting reddened objects may yield more of the elusive
redshifted molecular absorbers.

I shall crudely quantify this and show how this implies (if you
believe it!) that the SKA will be required to have any hope of
detecting molecular absorption in a z=0.1 radio galaxy in which we
have recently detected 21-cm absorption with the ATCA.