SPLASH: The Southern Parkes Large-Area Survey in Hydroxyl -- Data Description & Release

Abstract

We present the full data release for the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH), 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 survey covers the inner Galactic Plane, Central Molecular Zone and Galactic Centre over the range $|b|<$ 2${}^{\circ }$, 332${}^{\circ }$ $<l<$ 10${}^{\circ }$, with a small extension between 2${}^{\circ }$ $<b<$ 6${}^{\circ }$, 358${}^{\circ }$ $<l<$ 4${}^{\circ }$. SPLASH is the most sensitive large-scale survey of OH to-date, reaching a characteristic root-mean-square sensitivity of $\sim 15$ mK for an effective velocity resolution of $\sim 0.9$ km/s. 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 elsewhere. We also present radio continuum images at 1612, 1666 and 1720 MHz. Based on initial comparisons with ${}^{12}$CO(J=1-0), we find that OH rarely extends outside CO cloud boundaries in our data, but suggest that large variations in CO-to-OH brightness temperature ratios may reflect differences in the total gas column density traced by each. Column density estimation in the complex, continuum-bright Inner Galaxy is a challenge, and we demonstrate how failure to appropriately model sub-beam structure and the line-of-sight source distribution can lead to order-of-magnitude errors. Anomalous excitation of the 1612 and 1720 MHz satellite lines is ubiquitous in the inner Galaxy, but is disabled by line overlap in and around the Central Molecular Zone.

Main paper: 22 pages, 15 figures. Online-only material (appended to ArXiv PDF): 11 pages, 3 figure sets. Accepted to MNRAS. Survey data is available from: https://docs.datacentral.org.au/splash/

References in corpus (9)

• The Structure of Dark Molecular Gas in the Galaxy - I: A Pilot Survey for 18-cm OH Emission Towards $l\approx 105^{°},b\approx +1^{°}$
• The Effect of 53 micron IR Radiation on 18 cm OH Megamaser Emission
• Accurate OH maser positions from the SPLASH pilot region
• Multiplicity of nuclear dust lanes and dust lane shocks in the Milky Way bar
• Accurate OH Maser Positions From The SPLASH Survey III: The Final 96 Square Degrees
• Towards a three-dimensional distribution of the molecular clouds in the Galactic Centre
• The Effect of Far-infrared Radiation on the Hyperfine Anomaly of the OH 18 cm Transition
• MAGMO: Polarimetry of 1720-MHz OH Masers towards Southern Star Forming Regions
• OH as an Alternate Tracer for Molecular Gas: Quantity and Structure of Molecular Gas in W5

Cited by in corpus (2)

• Searching for nascent planetary nebulae: OHPNe candidates in the SPLASH survey
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