A SCUBA-2 850 micron survey of circumstellar disks in the λ Orionis cluster
- Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr., Honolulu, HI 96822 (United States)
We present results from an 850 μm survey of the ∼5 Myr old λ Orionis star-forming region. We used the SCUBA-2 camera on the James Clerk Maxwell Telescope to survey a ∼0.°5-diameter circular region containing 36 (out of 59) cluster members with infrared excesses indicative of circumstellar disks. We detected only one object at >3σ significance, the Herbig Ae star HD 245185, with a flux density of ∼74 mJy beam{sup −1} corresponding to a dust mass of ∼150 M{sub ⊕}. Stacking the individually undetected sources did not produce a significant mean signal but gives an upper limit on the average dust mass for λ Orionis disks of ∼3 M{sub ⊕}. Our follow-up observations of HD 245185 with the Submillimeter Array found weak CO 2–1 line emission with an integrated flux of ∼170 mJy km s{sup −1} but no {sup 13}CO or C{sup 18}O isotopologue emission at 30 mJy km s{sup −1} sensitivity, suggesting a gas mass of ≲1 M{sub Jup}. The implied gas-to-dust ratio is thus ≳50 times lower than the canonical interstellar medium value, setting HD 245185 apart from other Herbig Ae disks of similar age, which have been found to be gas rich; as HD 245185 also shows signs of accretion, we may be catching it in the final phases of disk clearing. Our study of the λ Orionis cluster places quantitative constraints on planet formation timescales, indicating that at ∼5 Myr the average disk no longer has sufficient dust and gas to form giant planets and perhaps even super-Earths; the bulk material has been mostly dispersed or is locked in pebbles/planetesimals larger than a few mm in size.
- OSTI ID:
- 22883009
- Journal Information:
- Astrophysical Journal, Vol. 806, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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