We present SMA and NOEMA observations of the host galaxy of FRB 121102 in the CO 3-2 and 1-0 transitions, respectively. We do not detect emission from either transition. We set 3σ upper limits to the CO luminosity LCO<2.5×107Kkms−1pc−2 for CO 3-2 and LCO<2.3×109Kkms−1pc−2 for CO 1-0. For Milky-Way-like star formation properties, we set a 3σ upper limit on the H2 mass of 2.5×108M⊙, slightly less than the predictions for the H2 mass based on the star formation rate. The true constraint on the H2 mass may be significantly higher, however, because of the reduction in CO luminosity that is common forlow-metallicity dwarf galaxies like the FRB host galaxy. These results demonstrate the challenge of identifying the nature of FRB progenitors through study of the host galaxy molecular gas. We also place a limit of 42 μJy (3σ) on the continuum flux density of the persistent radio source at 97 GHz, consistent with a power-law extrapolation of the low frequency spectrum, which may arise from an AGN or other nonthermal source.
@article{arxiv.1804.01584,
title = {A Search for Molecular Gas in the Host Galaxy of FRB 121102},
author = {Geoffrey C. Bower and Ramprasad Rao and Melanie Krips and Natasha Maddox and Cees Bassa and Elizabeth A. K. Adams and C. J. Law and Shriharsh P. Tendulkar and Huib Jan van Langevelde and Zsolt Paragi and Bryan J. Butler and Shami Chatterjee},
journal= {arXiv preprint arXiv:1804.01584},
year = {2018}
}