Detection of Exocometary CO within the 440Myr Old Fomalhaut Belt: A Similar CO+ CO2 Ice Abundance in Exocomets and Solar System Comets
MacGregor, Meredith A.
Wyatt, Mark C.
Kennedy, Grant M.
Hughes, A. M.
Fitzgerald, Michael P.
Graham, J. R.
Holland, W. S.
Su, Kate Y. L.
AffiliationUniv Arizona, Steward Observ
stars: individual (Fomalhaut A)
submillimeter: planetary systems
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PublisherIOP PUBLISHING LTD
CitationDetection of Exocometary CO within the 440Myr Old Fomalhaut Belt: A Similar CO+ CO2 Ice Abundance in Exocomets and Solar System Comets 2017, 842 (1):9 The Astrophysical Journal
JournalThe Astrophysical Journal
Rights© 2017. 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.
AbstractRecent Atacama Large Millimeter/submillimeter Array observations present mounting evidence for the presence of exocometary gas released within Kuiper Belt analogs around nearby main-sequence stars. This represents a unique opportunity to study their ice reservoir at the younger ages when volatile delivery to planets is most likely to occur. We here present the detection of CO J=2-1 emission colocated with dust emission from the cometary belt in the 440 Myr old Fomalhaut system. Through spectrospatial filtering, we achieve a 5.4s detection and determine that the ring's sky-projected rotation axis matches that of the star. The CO mass derived (0.65-42) x10(-7) M-circle plus is the lowest of any circumstellar disk detected to date and must be of exocometary origin. Using a steady-state model, we estimate the CO+ CO2 mass fraction of exocomets around Fomalhaut to be between 4.6% and 76%, consistent with solar system comets and the two other belts known to host exocometary gas. This is the first indication of a similarity in cometary compositions across planetary systems that may be linked to their formation scenario and is consistent with direct interstellar medium inheritance. In addition, we find tentative evidence that(49 +/- 27)% of the detected flux originates from a region near the eccentric belt's pericenter. If confirmed, the latter may be explained through a recent impact event or CO pericenter glow due to exocometary release within a steady-state collisional cascade. In the latter scenario, we show how the azimuthal dependence of the CO release rate leads to asymmetries in gas observations of eccentric exocometary belts.
VersionFinal published version