DISK IMAGING SURVEY OF CHEMISTRY WITH SMA. II. SOUTHERN SKY PROTOPLANETARY DISK DATA AND FULL SAMPLE STATISTICS

Abstract

This is the second in a series of papers based on data from DISCS, a\nSubmillimeter Array observing program aimed at spatially and spectrally\nresolving the chemical composition of 12 protoplanetary disks. We present data\non six Southern sky sources - IM Lup, SAO 206462 (HD 135344b), HD 142527, AS\n209, AS 205 and V4046 Sgr - which complement the six sources in the Taurus star\nforming region reported previously. CO 2-1 and HCO+ 3-2 emission are detected\nand resolved in all disks and show velocity patterns consistent with Keplerian\nrotation. Where detected, the emission from DCO+ 3-2, N2H+ 3-2, H2CO 3-2 and\n4-3,HCN 3-2 and CN 2-1 are also generally spatially resolved. The detection\nrates are highest toward the M and K stars, while the F star SAO 206462 has\nonly weak CN and HCN emission, and H2CO alone is detected toward HD 142527.\nThese findings together with the statistics from the previous Taurus disks,\nsupport the hypothesis that high detection rates of many small molecules depend\non the presence of a cold and protected disk midplane, which is less common\naround F and A stars compared to M and K stars. Disk-averaged variations in the\nproposed radiation tracer CN/HCN are found to be small, despite two orders of\nmagnitude range of spectral types and accretion rates. In contrast, the\nresolved images suggest that the CN/HCN emission ratio varies with disk radius\nin at least two of the systems. There are no clear observational differences in\nthe disk chemistry between the classical/full T Tauri disks and transitional\ndisks. Furthermore, the observed line emission does not depend on measured\naccretion luminosities or the number of infrared lines detected, which suggests\nthat the chemistry outside of 100 AU is not coupled to the physical processes\nthat drive the chemistry in the innermost few AU.\n