ALMA Observations of the Asymmetric Dust Disk around DM Tau

Abstract

We report an analysis of the dust disk around DM Tau, newly observed with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm. The ALMA observations with high sensitivity (8.4 μJy beam^-1) and high angular resolution (35 mas, 5.1 au) detect two asymmetries on the ring at r ∼ 20 au. They could be two vortices in early evolution, the destruction of a large-scale vortex, or double continuum emission peaks with different dust sizes. We also found millimeter emissions with ∼50 μJy (a lower-limit dust mass of 0.3 M_Moon) inside the 3 au ring. To characterize these emissions, we modeled the spectral energy distribution (SED) of DM Tau using a Monte Carlo radiative transfer code. We found that an additional ring at r = 1 au could explain both the DM Tau SED and the central point source. The disk midplane temperature at the 1 au ring calculated in our modeling is less than the typical water sublimation temperature of 150 K, prompting the possibility of forming small icy planets there.