ALMA observations of the archetypal "hot core" that isn't: Orion KL

• Main Authors: Orozco-Aguilera, M. T, Zapata, Luis A, Hirota, Tomoya, Qin, Sheng-Li, M, Masqué Josep
• Format: Journal Article
• Language: English
• Published: 28-08-2017
• Subjects: Physics - Astrophysics of Galaxies; Physics - Solar and Stellar Astrophysics
• DOI: 10.48550/arxiv.1708.08448

We present sensitive high angular resolution ($\sim$ 0.1$''$ -- 0.3$''$)
continuum ALMA (The Atacama Large Millimeter/Submillimeter Array) observations
of the archetypal hot core located in Orion-KL. The observations were made in
five different spectral bands (bands 3, 6, 7, 8, and 9) covering a very broad
range of frequencies (149 -- 658 GHz). Apart of the well-know millimeter
emitting objects located in this region (Orion Source I and BN), we report the
first submillimeter detection of three compact continuum sources (ALMA 1-3) in
the vicinities of the Orion-KL hot molecular core. These three continuum
objects have spectral indices between 1.47 to 1.56, and brightness temperatures
between 100 to 200 K at 658 GHz suggesting that we are seeing moderate
optically thick dust emission with possible grain growth. However, as these
objects are not associated with warm molecular gas, and some of them are
farther out from the molecular core, we thus conclude that they cannot heat the
molecular core. This result favours the hypothesis that the hot molecular core
in Orion-KL core is heated externally.