Radio Search for H2CCC toward HD 183143 as a Candidate for a Diffuse Interstellar Band Carrier

TL;DR

This study conducted radio observations to test if H2CCC could be responsible for a specific diffuse interstellar band, finding it unlikely due to the low upper limit of its abundance.

Contribution

First radio search for H2CCC toward HD 183143, providing constraints on its role as a diffuse interstellar band carrier.

Findings

H2CCC was not detected at 103 GHz

Upper limit on H2CCC column density was 2.0 x 10^13 cm^-2

H2CCC's contribution to the 5450 Å DIB is less than 1/25

Abstract

To clarify the authenticity of a recently proposed identification of H2CCC (linear-C3H2) as a diffuse interstellar band carrier, we searched for the rotational transition of H2CCC at a frequency of 103 GHz toward HD 183143 using a 45-m telescope at the Nobeyama Radio Observatory. Although rms noise levels of 32 mK in the antenna temperature were achieved, detection of H2CCC was unsuccessful, producing a 3 sigma upper limit corresponding to a column density of 2.0 \times 1013 cm-2. The upper limit indicates that the contribution of H2CCC to the diffuse interstellar band at 5450 {\AA} is less than 1/25; thus, it is unlikely that the laboratory bands of the B1B1-X1A1 transition of H2CCC and the diffuse interstellar bands at 5450 {\AA} (and also 4881 {\AA}) toward HD 183143 are related.