# Molecular complexity in the interstellar medium

## TL;DR

This paper discusses advances in detecting complex organic molecules in the interstellar medium, highlighting the role of laboratory, theoretical, and observational progress, especially with ALMA and NOEMA, exemplified by the ReMoCA survey.

## Contribution

It introduces the ReMoCA spectral line survey and reviews recent developments in understanding molecular complexity in the ISM using new observational tools.

## Key findings

- Detection of increasingly complex molecules in the ISM.
- High-resolution ALMA observations reduce spectral confusion.
- Identification of molecules with complex structures.

## Abstract

The search for complex organic molecules in the interstellar medium (ISM) has revealed species of ever greater complexity. This search relies on the progress made in the laboratory to characterize their rotational spectra. Our understanding of the processes that lead to molecular complexity in the ISM builds on numerical simulations that use chemical networks fed by laboratory and theoretical studies. The advent of ALMA and NOEMA has opened a new door to explore molecular complexity in the ISM. Their high angular resolution reduces the spectral confusion of star-forming cores and their increased sensitivity allows the detection of low-abundance molecules that could not be probed before. The complexity of the recently-detected molecules manifests itself not only in terms of number of atoms but also in their molecular structure. We discuss these developments and report on ReMoCA, a new spectral line survey performed with ALMA toward the high-mass star-forming region Sgr B2(N).