# Discovery of a distant molecular cloud in the extreme outer Galaxy with the Nobeyama 45-m telescope

## TL;DR

This paper reports the discovery of the most distant molecular cloud in the Galaxy, located in the extreme outer Galaxy, using the Nobeyama 45-m telescope, expanding our understanding of molecular clouds at the Galaxy's edge.

## Contribution

It presents the first identification and characterization of a molecular cloud at the largest kinematic distance in the Galaxy, utilizing CO observations and Galactic parameters from Reid et al.

## Key findings

- Located at 21 kpc heliocentric distance
- Cloud size approximately 4 pc by 3 pc
- Mass estimated at 250 solar masses

## Abstract

We report the discovery of the molecular cloud whose kinematic distance is the largest in the Galaxy at the present moment, named G213.042$+$0.003, at $l =$ 213.042$^\circ$ and $b =$ 0.003$^\circ$ in the $^{12}$CO($J =$ 1-0) line using the Nobeyama 45-m telescope and a multi-beam receiver BEARS. This molecular cloud is located at the heliocentric distance of 21$_{-7}^{+12}$ kpc and Galactocentric distance of 29$_{-7}^{+12}$ kpc, which are estimated as the kinematic distances with the Galactic parameters obtained by Reid et al. (2014, ApJ, 783, 130). Its major and minor diameters and line width were measured to be 4.0$_{-1.3}^{+2.3}$ pc, 3.0$_{-1.0}^{+1.7}$ pc, and 1.5 km s$^{-1}$, respectively. The cloud mass was estimated to be 2.5$_{-1.4}^{+3.7}$ $\times$ 10$^2$ $M_\odot$ using the CO-to-H$_2$ conversion factor of 5.6 $\times$ 10$^{20}$ cm$^{-2}$ (K km s$^{-1}$)$^{-1}$ obtained in far outer Galaxy.