Hot corinos in NGC 1333-IRAS4B and IRAS2A

S Bottinelli,J P Williams,C Ceccarelli,B Lefloch

doi:10.1051/0004-6361:20065139

S Bottinelli, J P Williams + Show 2 more

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https://doi.org/10.1051/0004-6361:20065139

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Abstract

(Abridged) We aim to enlarge the number of known hot corinos and carry out a first comparative study with hot cores. The ultimate goal is to understand whether complex organic molecules form in the gas phase or on grain surfaces, and what the possible key parameters are. We observed millimeter rotational transitions of HCOOH, HCOOCH3, CH3OCH3, CH3CN, and C2H5CN in a sample of low-mass protostars with the IRAM-30m. Using the rotational diagram method coupled with the information about the sources' structure, we calculate the abundances of the observed molecules. To interpret these abundances, we review the proposed formation processes of the above molecules. We report the detection of HCOOCH3 and/or CH3CN towards NGC1333-IRAS4B and NGC1333-IRAS2A. We find that abundance ratios of O-bearing molecules to methanol or formaldehyde in hot corinos are comparable and about unity, and are relatively (depending on how the ratios are determined) higher than those in hot cores and in Galactic center clouds. So far, complex organic molecules were detected in all the hot corinos where they were searched for, suggesting that it is a common phase for low-mass protostars. While some evidence points to grain-surface synthesis (either in the cold or warm-up phase) of these molecules (in particular for HCOOH and HCOOCH3), the present data do not allow us to disregard gas-phase formation. More observational, laboratory, and theoretical studies are required to improve our understanding of hot corinos.

Highlights

Many aspects of the formation of solar-type stars have been elucidated and, even though the details are much debated, there exists a widely accepted framework for it
We presented the detections of methyl formate and/or methyl cyanide in the low-mass protostars IRAS4B and IRAS2A, confirming the presence of a hot corino in their inner envelope
– Hot corinos are a common phase in the formation of solartype protostars and complex organic molecules are ubiquitous in Class 0 protostars

Summary

Introduction

Many aspects of the formation of solar-type stars have been elucidated and, even though the details are much debated, there exists a widely accepted framework for it (see the volume Protostars and Planets V, for example, Ceccarelli et al 2006; Ward-Thompson et al 2006; White et al 2006). They may condense onto the grain surfaces again during the proto-planetary disk phase Perhaps they are incorporated into the planetesimals forming the building blocks of planets, or into comets and asteroids, in which case they may end up on newly formed planets as accretion proceeds. This picture is, at least partially, supported by the fact that some complex organic molecules are found both in hot corinos and in comets (e.g., methyl cyanide CH3CN, methyl formate HCOOCH3, and formic acid HCOOH; Ehrenfreund & Charnley 2000).

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