Evolution of Cold Circumstellar Dust around Solar-type Stars

We present submillimeter (Caltech Submillimeter Observatory 350 μm) and millimeter (Swedish-ESO Submillimetre Telescope [SEST] 1.2 mm, Owens Valley Radio Observatory [OVRO] 3 mm) photometry for 127 solar-type stars from the Formation and Evolution of Planetary Systems Spitzer Legacy program that have masses between ∼0.5 and 2.0 M_⊙ and ages from ∼3 Myr to 3 Gyr. Continuum emission was detected toward four stars with a signal-to-noise ratio ≥ 3: the classical T Tauri stars RX J1842.9-3532, RX J1852.3-3700, and PDS 66 with SEST, and the debris-disk system HD 107146 with OVRO. RX J1842.9-3532 and RX J1852.3-3700 are located in projection near the R CrA molecular cloud, with estimated ages of ∼10 Myr (Neuhäuser et al.), whereas PDS 66 is a probable member of the ∼20 Myr old Lower Centaurus-Crux subgroup of the Scorpius-Centaurus OB association (Mamajek et al.). The continuum emission toward these three sources is unresolved at the 24'' SEST resolution and likely originates from circumstellar accretion disks, each with estimated dust masses of ∼5 × 10^-5 M_⊙. Analysis of the visibility data toward HD 107146 (age ∼ 80–200 Myr) indicates that the 3 mm continuum emission is centered on the star within the astrometric uncertainties and resolved with a Gaussian-fit FWHM size of (65 ± 14) × (42 ± 13), or 185 AU × 120 AU. The results from our continuum survey are combined with published observations to quantify the evolution of dust mass with time by comparing the mass distributions for samples with different stellar ages. The frequency distribution of circumstellar dust masses around solar-type stars in the Taurus molecular cloud (age ∼ 2 Myr) is distinguished from that around 3–10 Myr and 10–30 Myr old stars at a significance level of ∼1.5 and ∼3 σ, respectively. These results suggest a decrease in the mass of dust contained in small dust grains and/or changes in the grain properties by stellar ages of 10–30 Myr, consistent with previous conclusions. Further observations are needed to determine if the evolution in the amount of cold dust occurs on even shorter timescales.