Chemical Evolution in VeLLOs

TL;DR

This paper investigates the chemical evolution of Very Low Luminosity Objects (VeLLOs) using episodic accretion models, highlighting how their unique thermal histories influence molecular chemistry and proposing CO2 ice as a thermal process tracer.

Contribution

It introduces a chemical evolution model for VeLLOs considering episodic accretion, revealing distinct molecular relations and identifying CO2 ice as a key thermal history indicator.

Findings

CO and N2H+ relations differ from other cores.

CO2 ice feature at 15.2 micron traces thermal history.

Chemical evolution is significantly affected by episodic accretion.

Abstract

A new type of object called "Very Low Luminosity Objects (VeLLOs)" has been discovered by the Spitzer Space Telescope. VeLLOs might be substellar objects forming by accretion. However, some VeLLOs are associated with strong outflows, indicating the previous existence of massive accretion. The thermal history, which significantly affects the chemistry, between substellar objects with a continuous low accretion rate and objects in a quiescent phase after massive accretion (outburst) must be greatly different. In this study, the chemical evolution has been calculated in an episodic accretion model to show that CO and N2H+ have a relation different from starless cores or Class 0/I objects. Furthermore, the CO2 ice feature at 15.2 micron will be a good tracer of the thermal process in VeLLOs.