Molecular Gas in Debris Disks around Young A-type Stars

Attila Moór, Michel Curé, Agnes Kóspál, Péter Abrahám, Timea Csengeri, Carlos Eiroa, Diah Gunawan, Thomas Henning, A. Meredith Hughes, Attila Juhász, Nicole Pawellek, Mark Wyatt

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33 Citations (Scopus)

Abstract

According to the current paradigm of circumstellar disk evolution, gas-rich primordial disks evolve into gas-poor debris disks that are composed of second-generation dust. To explore the transition between these phases, we searched for 12CO, 13CO, and C18O emission in seven dust-rich debris disks around young A-type stars, using the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 6. We discovered molecular gas in three debris disks. In all of these disks, the 12CO line was optically thick, highlighting the importance of less abundant molecules in reliable mass estimates. By supplementing our target list with literature data, we compiled a volume-limited sample of dust-rich debris disks around young A-type stars within 150 pc. We obtained a CO detection rate of 11/16 above a 12CO J = 2-1 line luminosity threshold of ∼1.4 ×104 Jy km s-1pc2 in the sample. This high incidence implies that the presence of CO gas in the bright debris disks around young A-type stars is more likely the rule than the exception. Interestingly, dust-rich debris disks around young FG-type stars exhibit, with the same detectability threshold as A-type stars, a significantly lower gas incidence. While the transition from the protoplanetary phase to the debris phase is associated with a drop in the dust content, our results exhibit a large spread in the CO mass in our debris sample, with peak values that are comparable to those in the protoplanetary Herbig Ae disks. In the particularly CO-rich debris systems, the gas may have a primordial origin, which is a characteristic of a hybrid disk.

Original languageEnglish
Article number123
JournalAstrophysical Journal
Volume849
Issue number2
DOIs
Publication statusPublished - Nov 10 2017

Keywords

  • circumstellar matter
  • infrared: stars
  • stars: individual (HD 121191, HD 121617, HD 131488)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Moór, A., Curé, M., Kóspál, A., Abrahám, P., Csengeri, T., Eiroa, C., Gunawan, D., Henning, T., Hughes, A. M., Juhász, A., Pawellek, N., & Wyatt, M. (2017). Molecular Gas in Debris Disks around Young A-type Stars. Astrophysical Journal, 849(2), [123]. https://doi.org/10.3847/1538-4357/aa8e4e