High-resolution LAsMA ¹²CO and ¹³CO observation of the G305 giant molecular cloud complex

Abstract

Context. Understanding the effect of feedback, interaction of young massive stars with their parental giant molecular clouds, is of central importance for studies of the interstellar medium and star formation. Aims. We observed the G305 star-forming complex in the J = 3–2 lines of 12CO and 13CO to investigate how molecular gas surrounding the central stellar clusters is being impacted by feedback. Methods. The Atacama Pathfinder EXperiment (APEX) telescope’s Large APEX sub-Millimeter Array (LAsMA) multibeam receiver was used to observe the region. Excitation temperatures and column density maps were produced. Combining our data with data from the structure, excitation, and dynamics of the inner Galactic interstellar medium survey resulted in a 13CO J = 3−2∕2−1 excitation map. To verify whether feedback from stellar clusters is responsible for exciting the gas, the distribution of CO excitation was compared with that of 8 μm emission imaged with Spitzer, which is dominated by UV-excited emission from polycyclic aromatic hydrocarbons. Line centroid velocities, as well as stacked line profiles were examined to investigate the effect of feedback on the gas dynamics. Results. Line profiles along radially outward directions demonstrate that the excitation temperature and 13CO J = 3−2∕2−1 ratio increase steeply by factors of ~2–3 at the edge of the denser gas traced by 13CO that faces the hot stars at the center of the complex and steadily decreases away from it. The column density also increases at the leading edge, but it does not always decrease steadily outward. Regions with a higher 8 μm flux have higher median excitation temperatures, column densities, and 13CO J = 3−2∕2−1 ratio. The centroid velocity probability distribution function of the region shows exponential wings, indicative of turbulence driven by strong stellar winds. Stacked spectra in regions with stronger feedback have higher skewness and narrower peaks with pronounced wings compared to regions with weaker feedback. Conclusions. Feedback from the stellar cluster in G305 has demonstrable effects on the excitation as well as on the dynamics of the giant molecular cloud.

High-resolution APEX/LAsMA 12CO and 13CO (3–2) observation of the G333 giant molecular cloud complex

“…The 7 pixel Large APEX sub-Millimeter Array (LAsMA) receiver was used to observe the J = 3 − 2 transitions of 12 CO (ν rest ∼ 345.796 GHz) and 13 CO (ν rest ∼ 330.588 GHz) simultaneously in the upper and lower sideband, respectively. More details about the receiver are given in Mazumdar et al (2021). The local oscillator frequency was set at 338.190 GHz in order to avoid contamination of the 13 CO (3−2) lines due to bright 12 CO (3−2) emission from the image band.…”

“…Apart from the atmospheric attenuation, this also corrects for rear spillover, blockage, scattering and ohmic losses. A beam efficiency value η mb = 0.71 (Mazumdar et al 2021) was used to convert intensities from T * A to the main beam brightness temperature T mb . The final noise levels of the 12 CO (3-2) and 13 CO (3-2) data cubes are ∼0.32 K and ∼0.46 K, respectively.…”

High-resolution APEX/LAsMA 12CO and 13CO (3–2) observation of the G333 giant molecular cloud complex

“…The final data cubes have a velocity resolution of 0.25 km s −1 , an angular resolution of 19.5 ′′ , and a pixel size of 6 ′′ . A beam efficiency value η mb = 0.71 (Mazumdar et al 2021a) was used to convert intensities from the T * A scale to main beam brightness temperatures, T mb .…”

Dependence of Molecular Cloud Samples on Angular Resolution, Sensitivity, and Algorithms

“…Molecular clouds (see Heyer & Dame 2015 for a review) are usually observed in three-dimensional position-position-velocity (PPV) space or two-dimensional dust continuum emission (e.g., Bot et al 2007;Könyves et al 2015;Arzoumanian et al 2019). PPV data provide valuable information about properties of molecular clouds and activities in them, such as densities (e.g., Kauffmann et al 2017;Evans et al 2021), temperatures (e.g., Wang et al 2019;Mazumdar et al 2021), and molecular outflows (e.g., Snell et al 1980;Zhang et al 2001Zhang et al , 2020Yang et al 2018Yang et al , 2022, as well as large-scale structures of the Milky Way (e.g., Dame et al 2001;Sun et al 2015;Du et al 2017). Missing one dimension of position, PPV data are incomplete compared with position-position-position (PPP) data and are unable to distinguish molecular clouds in crowded regions, such as the first Galactic quadrant, and velocity degenerated directions, such as the Galactic anticenter.…”