Quenched Cold Accretion of a Large-scale Metal-poor Filament due to Virial Shocking in the Halo of a Massive z = 0.7 Galaxy

Creators: Churchill, Christopher W.; Kacprzak, Glenn G.; Steidel, Charles C.; Spitler, Lee R.; Holtzman, Jon; Nielsen, Nikole M.; Trujillo-Gomez, Sebastian

Abstract

Using HST/COS/STIS and HIRES/Keck high-resolution spectra, we have studied a remarkable H I absorbing complex at z = 0.672 toward the quasar Q1317+277. The H I absorption has a velocity spread of Δv = 1600 km s^(–1), comprises 21 Voigt profile components, and resides at an impact parameter of D = 58 kpc from a bright, high-mass (log M_(vir)/M_☉ ≃ 13.7) elliptical galaxy that is deduced to have a 6 Gyr old, solar metallicity stellar population. Ionization models suggest the majority of the structure is cold gas surrounding a shock-heated cloud that is kinematically adjacent to a multi-phase group of clouds with detected C III, C IV, and O VI absorption, suggestive of a conductive interface near the shock. The deduced metallicities are consistent with the moderate in situ enrichment relative to the levels observed in the z ~ 3 Lyα forest. We interpret the H I complex as a metal-poor filamentary structure being shock heated as it accretes into the halo of the galaxy. The data support the scenario of an early formation period (z > 4) in which the galaxy was presumably fed by cold-mode gas accretion that was later quenched via virial shocking by the hot halo such that, by intermediate redshift, the cold filamentary accreting gas is continuing to be disrupted by shock heating. Thus, continued filamentary accretion is being mixed into the hot halo, indicating that the star formation of the galaxy will likely remain quenched. To date, the galaxy and the H I absorption complex provide some of the most compelling observational data supporting the theoretical picture in which accretion is virial shocked in the hot coronal halos of high-mass galaxies.

Additional Information

© 2012 American Astronomical Society. Received 2012 April 17; accepted 2012 August 16; published 2012 November 6. The anonymous referee is gratefully acknowledged for helpful comments to clarify points, and for carefully reading this manuscript. We thank Daniel Ceverino for several stimulating and informative discussions during his visit to New Mexico State University and for helpful comments on an early draft of this paper, Kyle Stewart for several informative email exchanges with regard to halo abundance matching methods, and Avishai Dekel for helpful comments on cold streams penetrating the virialized shock-heated medium in massive halos. This research was primarily support through grant HST-GO-11667.01-A provided by NASA via the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA) under NASA contract NAS 5-26555. C.W.C. thanks G.G.K., and Michael T. Murphy, and Swinburne Faculty Research Grants for providing funding for a visit to Swinburne University of Technology. Some observations are obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium (ARC). Additional data were obtained at Kitt Peak National Optical Astronomy Observatory, which is operated by AURA under cooperative agreement with the National Science Foundation. Some data presented herein were obtained at the W. M. Keck observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. This research has also made use of the SIMBAD database, operated at Centre de Données, Strasbourg, France. Facilities: HST (WFPC2, STIS, COS), Keck:I (HIRES, LRIS), ARC (3.5-m Telescope), Mayall (IRIM)

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