The COS Absorption Survey of Baryon Harbors (CASBaH): Warm–Hot Circumgalactic Gas Reservoirs Traced by Ne VIII Absorption
AuthorBurchett, Joseph N.
Tripp, Todd M.
Prochaska, J. Xavier
Werk, Jessica K.
Howk, J. Christopher
Willmer, Christopher N. A.
Meiring, Joseph D.
Bowen, David V.
Peeples, Molly S.
Jenkins, Edward B.
O’Meara, John M.
AffiliationUniv Arizona, Steward Observ
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationJoseph N. Burchett et al 2019 ApJL 877 L20
JournalASTROPHYSICAL JOURNAL LETTERS
Rights© 2019. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractWe survey the highly ionized circumgalactic media (CGM) of 29 blindly selected galaxies at 0.49 < z(gal) < 1.44 based on high signal-to-noise ratio ultraviolet spectra of z greater than or similar to 1 quasi-stellar objects and the galaxy database from the COS Absorption Survey of Baryon Harbors (CASBaH). We detect the Ne VIII doublet in nine of the galaxies, and for gas with N(Ne VIII) > 10(13.3) cm(-2) (>10(13.5) cm(-2)), we derive a Ne VIII covering fraction f(c) = 75(-25)(+15)% (44(-20)(+22)%) within impact parameters rho <= 200 kpc of M-* =10(9.)(5-11.5)M(circle dot) galaxies and f(c) = 70(-22)(+16)% (f(c) = 42 (+20)(-17)%) within rho <= 1.5 virial radii. We estimate the mass in Ne VIII-traced gas to be M-gas (Ne VIII) >= 10(9.5)M(circle dot) (Z/Z(circle dot))(-1), or 6%-20% of the expected baryonic mass if the Ne VIII absorbers have solar metallicity. Ionizing Ne VII to Ne VIII requires 207 eV, and photons with this energy are scarce in the CGM. However, for the median halo mass and redshift of our sample, the virial temperature is close to the peak temperature for the Ne VIII ion, and the Ne VIII-bearing gas is plausibly collisionally ionized near this temperature. Moreover, we find that photoionized Ne VIII requires cool and low-density clouds that would be highly underpressured (by approximately two orders of magnitude) relative to the putative, ambient virialized medium, complicating scenarios where such clouds could survive. Thus, more complex (e.g., nonequilibrium) models may be required; this first statistical sample of Ne VIII absorber/galaxy systems will provide stringent constraints for future CGM studies.
VersionFinal published version
SponsorsNASA programs from the Space Telescope Science Institute [HST-GO-11741, HST-GO-13846, HST-AR-14299]; NASA [ATP 80NSSC18K1016, NAS5-26555]