High-S/N Quasar Observations with HST/COS: Deep Fields for Spectroscopy
Abstract
Hubble is still in prime observing condition for making transformative discoveries in UV astronomy. In this white paper we describe the science case for a deep (S/N>30) UV spectroscopic survey with HST/COS targeting approximately 20 QSOs at 0.5<z<1.5 at good resolution (20 km/s). This survey would capitalize on our current UV capability, produce a legacy dataset enabling community science in many areas of galactic and extragalactic research, and pioneer a path for future UV science with the Habitable Worlds Observatory. Such high-S/N spectra are largely missing from the MAST archives, and would be analogous to the deep Hubble imaging fields (HDF, UDF, Frontier Fields) that have been enormously successful and far-reaching in their science impact. This legacy dataset would enable frontier science programs in several areas, including (1) studies of the CGM and IGM at unparalleled sensitivity, covering a wide range of UV metal lines and reaching very low H I column densities of log N=12.6 and low metallicities near [Z/H]=-2, enabling precision studies of the chemical abundances, ionization, temperature, and baryon and metal budgets of the CGM and IGM; (2) diffuse gas in the Milky Way and Local Group, including high-velocity clouds and gas streams from satellite mergers; (3) AGN outflows, which would be probed in the rest-frame extreme ultraviolet (EUV), covering continuum-generation mechanisms and diagnostics of gas in accretion-disk outflows.
Comments: White Paper responding to the STScI request for community input: "Building a Roadmap for Hubble science into the 2030s"
Cite
@article{arxiv.2605.29949,
title = {High-S/N Quasar Observations with HST/COS: Deep Fields for Spectroscopy},
author = {Andrew J. Fox and Jerry Kriss and Philipp Richter and J. Michael Shull and Frances Cashman and Sapna Mishra and Annelia Anderson and Nahum Arav and Ramona Augustin and Kathleen Barger and Michelle Berg and Rongmon Bordoloi and Sanchayeeta Borthakur and Joseph Burchett and Jane Charlton and Hsiao-Wen Chen and Christopher Churchill and Ryan Cooke and Annalisa de Cia and Gisella de Rosa and Romeel Davé and Yakov Faerman and Travis Fischer and David French and Farhan Hasan and Svea Hernandez and Cameron Hummels and Sean Johnson and Glenn Kacprzak and Vikram Khaire and Doyeon Avery Kim and Brad Koplitz and Varsha Kulkarni and Nicolas Lehner and Matilde Mingozzi and Talawanda Monroe and Sowgat Muzahid and Benjamin Oppenheimer and Molly Peeples and Céline Péroux and Patrick Petitjean and Andreea Petric and Max Pettini and Zhijie Qu and Kate Rowlands and Ravi Sankrit and Debopam Som and Raghunathan Srianand and Nicolas Tejos and Jason Tumlinson and Bart Wakker and Jessica Werk},
journal= {arXiv preprint arXiv:2605.29949},
year = {2026}
}