Revealing a detailed mass distribution of a high-density core MC27/L1521F in Taurus with ALMA

TL;DR

This study uses high-resolution ALMA observations to map the detailed mass distribution and internal structure of the dense core MC27/L1521F in Taurus, revealing substructures and a flatter density profile in the inner regions.

Contribution

It provides the first detailed, multi-scale column density map of MC27/L1521F, uncovering substructures and a unique radial density profile in a very early star formation stage core.

Findings

Inner core has a flatter density profile (~r^{-0.4}) compared to outer regions (~r^{-1.0})

Substructures are present in dust and molecular emissions within the core

Protostellar source MMS-1 is unresolved and lacks associated gas emission

Abstract

We present the results of ALMA observations of dust continuum emission and molecular rotational lines toward a dense core MC27 (aka L1521F) in Taurus, which is considered to be at a very early stage of star formation. The detailed column density distribution on size scales from a few tens AU to ~10,000 AU scale are revealed by combining the ALMA (12 m array + 7 m array) data with the published/unpublished single-dish data. The high angular resolution observations at 0.87 mm with a synthesized beam size of ~0."74 x 0."32 reveal that a protostellar source, MMS-1, is not spatially resolved and lacks associated gas emission, while a starless high-density core, MMS-2, has substructures both in dust and molecular emission. The averaged radial column density distribution of the inner part of MC27/L1521F (r $\lesssim$ 3000 AU) is N(H2) ~r$^{-0.4}$, clearly flatter than that of the outer part, ~r$^{-1.0}$. The complex velocity/spatial structure obtained with previous ALMA observations is located inside the inner flatter region, which may reflect the dynamical status of the dense core.