A RADIAL VELOCITY AND CALCIUM TRIPLET ABUNDANCE SURVEY OF FIELD SMALL MAGELLANIC CLOUD GIANTS

Abstract

We present the results of a pilot wide-field radial velocity and metal abundance survey of red giants in 10 fields in the Small Magellanic Cloud (SMC). The targets lie at projected distances of 0.9 and 1.9 kpc from the SMC center (m − M = 18.79) to the north, east, south, and west. Two more fields are to the east at distances of 3.9 and 5.1 kpc. In this last field, we find only a few to no SMC giants, suggesting that the edge of the SMC in this direction lies approximately at 6 kpc from its center. In all eastern fields, we observe a double peak in the radial velocities of stars, with a component at the classical SMC recession velocity of ∼160 km s−1 and a high-velocity component at about 200 km s−1, similar to observations in H i. In the most distant field (3.9 kpc), the low-velocity component is at 106 km s−1. The metal abundance distribution in all fields is broad and centered at about [Fe/H] ∼−1.25, reaching to solar and possibly slightly supersolar values and down to [Fe/H] of about −2.5. In the two innermost (0.9 kpc) northern and southern fields, we observe a secondary peak at metallicities of about ∼−0.6. This may be evidence of a second episode of star formation in the center, possibly triggered by the interactions that created the Stream and Bridge.