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Find information, examples, FAQs and extensive descriptions of the data, curated by the survey teams.

SPLASH logo.jpeg


The Southern Parkes Large-Area Survey in Hydroxyl (SPLASH) is a sensitive, unbiased, and fully sampled survey of the southern Galactic plane and Galactic Centre in all four ground-state transitions of the hydroxyl (OH) radical.

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The Southern Parkes Large-Area Survey in Hydroxyl (SPLASH; Dawson et al. 2014, 2022), is a sensitive, unbiased single-dish survey of the Southern Galactic Plane in all four ground-state transitions of the OH radical at 1612, 1665, 1667 and 1720 MHz.

The 18-cm OH lines are well-known for their maser emission, which traces a diverse range of astrophysical phenomena, from star-formation, to SNRs, to evolved stellar envelopes. However, 18-cm OH can also be used to study the extended molecular ISM, including diffuse, CO-dark H2 (e.g. Li et al. 2018, Busch et al. 2021), and the interaction zones around HII regions (Petzler, Dawson & Wardle 2020).

The SPLASH survey covers the inner Galactic Plane, Central Molecular Zone and Galactic Centre over the range |b| < 2◦, 332◦ < l < 10◦, with a small extension between 2◦ < b < 6◦, 358◦ < l < 4◦. It is the most sensitive large-scale survey of OH to-date, reaching a characteristic root-mean-square sensitivity of ∼15 mK for an effective velocity resolution of ∼0.9 km/s, and an effective spatial resolution of ~15'. Detailed survey specs can be found here.

The spectral line datacubes are optimised for the analysis of extended, quasi-thermal OH, but also contain numerous maser sources, which have been confirmed interferometrically and published separately (Qiao et al. 2016, 2018, 2020).

Survey Coverage + Max/Min Maps

Image descriptions: Left: Top-down survey coverage map. Right: Combined peak emission/absorption maps for all four transitions, showing the most extreme value of the brightness temperature at each spatial position. The sense of the emission and absorption encodes information about the physical state of the gas.

DR 1

SPLASH Data Release 1 comprises four spectral datacubes and three 2D continuum images for the full survey region.


This data release is fully described in Dawson et al. (2022).

Survey specs are summarised here.

A note of caution: spectral baseline correction for the central molecular zone (CMZ) has not been performed to the same degree of goodness as the rest of the survey. See the survey paper for further details.


SPLASH is a survey of the Southern Milky Way with the Parkes radio telescope in all four ground-state transitions of the diatomic molecule hydroxyl (OH).
Joanne Dawson
[javascript protected email address]
March 1, 2014
Latest updates view all
Data Release 1 Survey Specs March 10, 2022, 6:02 a.m. joanne.dawson