N2H+ and HC3N Observations of the Orion A Cloud

TL;DR

This study maps molecular emissions in the Orion A cloud, revealing the distribution, core properties, and temperature of dense gas, with new insights into the spatial relationship of molecules and star-forming regions.

Contribution

It provides detailed molecular line observations of Orion A, identifying 34 cores, analyzing their kinematics and temperature, and comparing distributions of different molecules in star-forming regions.

Findings

N2H+ distribution closely follows dust continuum, except near Orion Nebula

34 cloud cores identified from N2H+ data

N2H+ linewidth varies across regions, indicating different dynamical states

Abstract

The ``integral-shaped filament'' of the Orion A giant molecular cloud was mapped in N2H+, and its northern end, the OMC-2/3 region was observed also in HC3N and CCS. The N2H+ distribution is similar to the dust continuum distribution, except for the central part of the Orion Nebula. The distribution of H13CO+ holds resemblance to that of dust continuum, but the N2H+ distribution looks more similar to dust continuum distribution. The N-bearing molecules, N2H+ and NH3 seem to be more intense in OMC-2, compared with the H13CO+ and CS distribution. We identified 34 cloud cores from N2H+ data. Over the Orion Nebula region, the N2H+ linewidth is large (1.1-2.1 km/s). In the OMC-2/3 region, it becomes moderate (0.5-1.3 km/s), and it is smaller (0.3-1.1 km/s) in the south of the Orion Nebula. On the other hand, the gas kinetic temperature of the quiescent cores observed in N2H+ is rather constant (~ 20 K) over the $\int$-shaped filament. We detected no CCS emission in the OMC-2/3 region. In general, N2H+ and HC3N distribution is quite similar in the OMC-2/3 region, but we observed displacement between N2H+ and HC3N over 2' scale in OMC-3, which has a chain of Class 0-I protostars (candidates).