Over the last two years, the research fellow, Dr. Marion Wienen, conducted an innovative programme and produced the first map of the Milky Way’s Perseus spiral arm in the Outer Galaxy from the perspective of an external observer at a fixed spatial resolution. This together with an extracted, uniform GMC sample will be extremely valuable for future comparison of Galactic and extragalactic GMCs. The first sub-aim of this objective was the identification of the Perseus spiral arm in the outer Galaxy. Precise radial velocities of masers from the BeSSeL survey (Reid et al. 2014, ApJ, 783, 130) were combined with the highest angular resolution 12CO observations of the outer Galaxy provided by Dr. Chris Brunt from the University of Exeter to calibrate the arm’s distance-velocity structure. (see attached figure). The fellow gained expertise in various coordinate transformation techniques to convert to an internal reference frame of the arm for the processed spiral arm data cube.
MW implemented the convolution of 12CO data to the same spatial resolution along the Perseus arm and regridded those onto a constant linear scale map (see attached figure). A whole processing pipeline of the extremely large 3D spectral line data cubes was created together with tools that enabled consistency checks of intermediate results. This part was essential to lay the groundwork for the whole project and all further analysis. The scientific work is described in a research paper that is almost ready for publication.
To extract clouds form the remapped 12CO data cube MW collaborated with the author of the widely used and influential cloud finding algorithm SCIMES, Dr. Dario Colombo. The advancement of the technical capability of the code to the particular 12CO data set was motivated by this fellowship and its development to process, for the first time, such a large area of molecular line emission as examined within this project. This objective made use of MW’s experience in developing scripts to exploit large data sets to search for correlations between the cloud properties such as their gas mass, radius, luminosity or virial mass. A research article reporting the cloud extraction and the resulting catalogue is currently in preparation and will be submitted in the near future.
In addition to the aforementioned papers an overview of the project together with links to the remapped 12CO data cube and cloud catalogue are illustrated on a project webpage (
https://milkywaytools.eu/perseus/(öffnet in neuem Fenster)). These results will shortly be made publicly available through the “Open Research Exeter (ORE)” repository as soon as the paper will be accepted. MW had the chance to discuss specific results of her research with other colleagues of the Astrophysics group such as Dr. Chris Brunt, Dr. Clare Dobbs and Prof. Tim Naylor. The fellow could contribute to an alternative method of the distance-velocity calibration that uses star counts from Gaia by providing her processed 12CO data set as a large test field. The results of this project were also disseminated at several national and international conferences among the galactic and extragalactic community. The presentations gave MW the opportunity to get in contact with researchers who are interested to use the remapped data cubes of the Perseus arm as a tool to create a link between research in our and nearby galaxies.
