Outer Galaxy High Resolution Survey

Survey Description

Coverage of OGHReS.
In a nutshell
Co-PIs Carsten König (MPIfR, Germany)
James Urquhart (Uni of Kent, UK)
First science Dario Colombo (MPIfR, Germany)
Telescope APEX, Chile
Instruments PI230, nFLASH230
Main lines 12CO(2-1), 13CO(2-1), C18O(2-1)
Other lines SiO, DCO+, CH2O, CH3OH
Coverage 180° ≤ ℓ ≤ 280°
Resolution 27'' (~2 pc at 10-15 kpc)
Sensitivity 0.4K @ 0.5km/s
Time ~1300 hr (total)

OGHReS (Outer Galaxy High Resolution Survey) is a large scale (100 deg2) molecular line APEX legacy survey of the outer Galaxy (see green shaded region in the figure to the right). The main aims of the survey are to investigate star formation in the outer Galaxy and constrain the large scale structure and dynamics of the Milky Way.

OGHReS is designed to be the outer Galaxy counterpart to the SEDIGISM survey that was targeting the inner Milky Way, and therefore covers similar molecular transitions. The main target lines are the 12CO(2-1), 13CO(2-1) and C18O(2-1) transitions. Therefore, they are well suited to trace the moderately dense (n ~ 103 cm-3) molecular gas in the Galactic ISM. The data also cover transitions from other molecules (SiO, DCO+, CH2O, CH3OH), typically found in higher density regions, and can be used to probe their physical conditions.

With an angular resolution of 27'' and a 1-sigma sensitivity usually below 0.5 K at 0.25 km s-1 velocity resolution, this survey provides the most detailed view of interstellar matter in the southern outer Galaxy over a wide range of scales, from individual star-forming clumps to giant molecular clouds and complexes. This survey will therefore fill a gap of high resolution CO surveys of the Milky Way in the coverage between ℓ = 190° and 280° at unprecedented resolution and sensitivity, and thus provide the most complete and detailed picture of the distribution of molecular gas in the southern Galaxy to date.

Data is being aquired since 2018 with the APEX telescope, and being processed with the GILDAS software and a custom Python based pipeline. So far more than half the survey is completed and work is under way for the first data release.

We aim to complete the survey by the end of 2022 and will provide public access to the processed survey data and auxiliary data products here in the future.

Sensitivity comparison between OGHReS and SEDIGISM.
Comparison of the 13CO noise variation of SEDIGISM (grey) to our data (green).
Comparison of our data obtained with a beam width of 27'' (left, G259-1.50 12CO(2-1) field) to the same region from the Dame et al. 2001 data at 80 resolution (right).

Project Resources

Survey Data Products and Publications

  • Access to the OGHReS database and data products will be made available here in the future.

Reference and Acknowledgments

A detailed description of the OGHReS survey and overview of the results will be given in the upcomming paper "OGHReS - The Outer Galaxy High Resolution Survey", König et al. (in prep).

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