First Hot Corino detected around an Isolated Intermediate-Mass Protostar: Cep\,E-mm

TL;DR

This study reports the first detection of a hot corino around an isolated intermediate-mass protostar, CepE-mm, revealing complex organic molecules and binary structure, and comparing its chemistry with other protostars.

Contribution

It provides the first observational evidence of a hot corino around an isolated intermediate-mass protostar and characterizes its chemical and structural properties.

Findings

Detection of bright complex organic molecules in CepE-mm

Identification of a binary protostellar system with a hot corino

Chemical properties similar to low-mass hot corinos

Abstract

Intermediate-mass (IM) protostars provide a bridge between the low- and high-mass protostars. Despite their relevance, little is known about their chemical diversity. We want to investigate the molecular richness towards the envelope of IM protostars and to compare their properties with other sources. We have selected the isolated IM Class 0 protostar CepE-mm to carry out an unbiased molecular survey with the IRAM 30m telescope between 72 and 350 GHz with an angular resolution lying in the range 7-34". These data were complemented with NOEMA observations of the spectral bands 85.9 - 89.6 GHz and 216.8 - 220.4 GHz at an angular resolution of 2.3 and 1.4", respectively. 30m spectra show bright emission of O- and N-bearing COMs. We identify three components in the spectral signature: an extremely broad line component associated with the outflowing gas, a narrow line component associated with the cold envelope, and a broad line component tracing the hot corino. NOEMA observations reveal CepE-mm as a binary protostellar system CepE-A and B, separated by 1.7". CepE-A dominates the core continuum emission and powers the high-velocity jet associated with HH377. Our interferometric maps show that COMs arises from a region of 0.7" size around CepE-A. Rotational temperatures were found to lie in the range 20-40 K with column densities ranging from a few 10^15 cm-2 for O-bearing species, down to a few 10^14 cm-2 for N-bearing species. Molecular abundances are similar to those measured towards other low- and intermediate-mass protostars. High-mass hot cores are significantly less abundant in methanol and N-bearing species are more abundant by 3 orders of magnitude.CepE-mm reveals itself as a binary protostellar system with a strong chemical differentiation. The brightest component of the binary is associated with a hot corino. Its properties are similar to those of low-mass hot corinos.