Evolution of Cold Circumstellar Dust around Solar-type Stars

Abstract

We present submillimeter (CSO 350um) and millimeter (SEST 1.2 mm, OVRO 3 mm) photometry for 125 solar-type stars from the FEPS Spitzer Legacy program that have masses between ~0.5 and 2.0 Msun 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. RXJ1842.9-3532 and RXJ1852.3-3700 are located in projection nearby the R CrA molecular cloud with estimated ages of ~10 Myr, while PDS66 is a probable member of the 20 Myr old Lower Centaurus-Crux subgroup of the Sco-Cen OB association. 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 ~5x10**-5 Msun. Analysis of the visibility data toward HD107146 (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 (6.5'' +/- 1.4'') x (4.2''+/-1.3''), or 185 AUx120 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 ~1,5sigma and 3sigma 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. (abridged)Comment: 37 pages, 8 figures, accepted for publication in the Astronomical Journa