GBT25A-023

The GBT survey for 22 GHz H2O Gigamasers from High-z Compton-thick Quasars

Abstract

Accurate distance measurements of high redshift galaxies have been recognized in recent years as an essential cosmological probe that can potentially break degeneracies between models that resolve the Hubble tension, the discrepancy in the Hubble constants between direct measurements and predictions based on the early-universe probes of cosmology. In order to identify maser systems that allow for measuring accurate distances to the high-z galaxies, we aim to conduct a pilot survey
that uses the ``filler" time to explore the capability of the GBT to achieve deep, sensitive spectra at the C-band and the X-band toward high-z sources that could produce luminous 22 GHz H2O gigamaser emissions. Detection of such maser systems would open a new avenue for direct, geometric distance measurements of high-z galaxies independent of distance ladders based on the well-established H2O megamaser technique. To optimize the detection rates, we target 12 robustly-identified Compton-thick quasars within the redshift range of 1 < z < 4. To achieve ~>5 sigma detections of the maser emissions from our targets, we request the total project time of 70 hours with GBT. The majority of our sources can be observed within the undersubscribed LST ranges at the C-band and X-band.

Investigators

Name	Institution
Cheng-Yu Kuo *	Virginia, University of; National Sun Yat-sen University
Jim Braatz	National Radio Astronomy Observatory
Yu Hung	National Sun Yat-sen University
Li-Ling Wei	National Sun Yat-sen University
Dominic Pesce	Virginia, University of; Smithsonian Astrophysical Observatory
Chris Henkel	Max-Planck-Institut für Radioastronomie
Chentao Yang	Chalmers University of Technology
Violette Impellizzeri	National Radio Astronomy Observatory; Leiden, University of; Joint ALMA Observatory
Liz Humphreys	Center for Astrophysics | Harvard & Smithsonian; European Southern Observatory

* indicates the PI