THE DISK IMAGING SURVEY OF CHEMISTRY WITH SMA. I. TAURUS PROTOPLANETARY DISK DATA

Abstract

Chemistry plays an important role in the structure and evolution of\nprotoplanetary disks, with implications for the composition of comets and\nplanets. This is the first of a series of papers based on data from DISCS, a\nSubmillimeter Array survey of the chemical composition of protoplanetary disks.\nThe six Taurus sources in the program (DM Tau, AA Tau, LkCa 15, GM Aur, CQ Tau\nand MWC 480) range in stellar spectral type from M1 to A4 and offer an\nopportunity to test the effects of stellar luminosity on the disk chemistry.\nThe disks were observed in 10 different lines at ~3" resolution and an rms of\n~100 mJy beam-1 at ~0.5 km s-1. The four brightest lines are CO 2-1, HCO+ 3-2,\nCN 2_3-1_2 and HCN 3-2 and these are detected toward all sources (except for\nHCN toward CQ Tau). The weaker lines of CN 2_2-1_1, DCO+ 3-2, N2H+ 3-2, H2CO\n3_03-2_02 and 4_14-3_13 are detected toward two to three disks each, and DCN\n3-2 only toward LkCa 15. CH3OH 4_21-3_12 and c-C3H2 are not detected. There is\nno obvious difference between the T Tauri and Herbig Ae sources with regard to\nCN and HCN intensities. In contrast, DCO+, DCN, N2H+ and H2CO are detected only\ntoward the T Tauri stars, suggesting that the disks around Herbig Ae stars lack\ncold regions for long enough timescales to allow for efficient deuterium\nchemistry, CO freeze-out, and grain chemistry.\n