Matrà, L, MacGregor, MA, Kalas, P et al. (13 more authors) (2017) Detection of Exocometary CO within the 440 Myr Old Fomalhaut Belt: A Similar CO+CO 2 Ice Abundance in Exocomets and Solar System Comets. The Astrophysical Journal, 842 (1). 9. ISSN 0004-637X
Abstract
Recent 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 5.4σ detection and determine that the ring's sky-projected rotation axis matches that of the star. The CO mass derived ($(0.65\mbox{--}42)\times {10}^{-7}\,{M}_{\oplus }$) 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 $(49\pm 27)$% 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.
Metadata
Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2017. The American Astronomical Society. All rights reserved. Reproduced in accordance with the publisher's self-archiving policy. |
Keywords: | circumstellar matter; comets: general; molecular processes; planetary systems; stars: individual (Fomalhaut A) ; submillimeter: planetary systems |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Astrophysics (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 27 Feb 2018 14:38 |
Last Modified: | 27 Feb 2018 14:38 |
Status: | Published |
Publisher: | American Astronomical Society |
Identification Number: | https://doi.org/10.3847/1538-4357/aa71b4 |
Related URLs: |