The Parkes 2.4 GHz Survey of the southern Galactic Plane
What is the survey?
The data presented herein comprise a deep, polarimetric survey along the Galactic Plane between 238° <l< 5°, covering latitudes out to b = ± 5° (greater than this over some longitudes). The survey was observed using the 64-m Parkes radio telescope, and images Stokes parameters I (total-power), Q and U (which relate to the linearly polarised emission) of the radio continuum emission at a frequency of 2.4 GHz.The survey has produced images of both the polarised-intensity and total-power continuum emission along the southern Galactic Plane. The resolution of these images is approximately 10.4 arcmin. The characteristics of the survey are detailed in the Table below. This is the most sensitive survey to date of the southern Milky Way at this frequency and shows many new and interesting features - especially on scale-sizes of the order of 1°.
| Centre frequency | 2.417 GHz |
| Bandwidth | 145 MHz |
| System temperature | 35 K |
| Telescope beamwidth | (8.40 × 8.93) ± 0.08 arcmin |
| Final survey resolution | (10.23 × 10.62) ± 0.07 arcmin |
| Image gridding | 4 × 4 arcmin |
| Nominal total-power rms noise | 17 mJy per beam area |
| ...in blocks 1 and 4 | 11 mJy per beam area |
| Nominal Stokes-Q and U rms noise | 7.5 mJy per beam area |
| ...in blocks 1 and 4 | 4.5 mJy per beam area |
| Longitude coverage | 5° > l > 238° |
| Nominal latitude coverage | b = ± 5° |
The image below show areas covered by the survey. The black areas have the nominal rms noise (as specified in the table above), whilst the herringbone sections have a slightly lower rms noise (again, see above). 
The survey is capable of detecting extended structures (with angular diameters of order 30 arcmin and larger) down to a total-power surface brightness of the order of 3000 Jy per steradian in unconfused areas.
The combination of lower system temperatures and increased receiver stability has led to these substantial increases in sensitivity. Comparing these results with earlier maps of the southern Plane, such as the 2700 MHz work of the late 1960's and early 1970's, shows that the rms noise of this survey is an order of magnitude better than these early maps. Indeed, we find the rms noise of our total-power results to be only slightly higher than the confusion noise predicted for the images.
In addition to the polarimetric results obtained from this survey, the most significant improvements of the current work over earlier total-power surveys of the southern Plane are:
- Greatly improved sensitivity. The rms noise is an order of magnitude less than that of the old Parkes 2700 MHz survey.
- Latitude coverage out to b = ± 5° previous high resolution surveys have covered only |b|
- The ability to image structure with scale-sizes of several degrees.
Who's involved?
This work was undertaken by Roy Duncan as part of a jointly supervised PhD project, between the Australia Telescope National Facility in Sydney (supervisors: Raymond Haynes and Ron Stewart), and The University Of Queensland Physics Department in Brisbane (supervisor: Keith Jones). This was the first jointly-supervised PhD project undertaken between the ATNF and any institution in Queensland.
Detailed information
More detailed information on the survey can be found in published papers within the literature. The standard references for the survey are:Duncan A.R., Stewart R.T., Haynes R.F., Jones K.L., 1995, MNRAS, 277, 36 (ADS entry)
Duncan A.R., Haynes R.T., Jones K.L., Stewart R.T., 1997, MNRAS, 291, 279 (ADS entry)
These relate to the total-power and linearly-polarised results, respectively.
Accessing the survey data
Data from the survey may be accessed from the ATNF in Australia, or from Roy Duncan's homepage at The University of Queensland in Brisbane, Australia. Additionally, the data should soon be available through the MPIfR's survey sampler.
Multiwavelength Milky Way
These data have also been combined with existing observations at 2.7 GHz, from the Effelsberg radio telescope (operated by the Max-Planck-Institut für Radioastronomie in Germany), of the rest of the Galactic Plane. The results are excellent, and have been placed on NASA's Multiwavelength Milky Way page and poster.You might notice pieces of the survey in other places, too. For example, the blue image from the survey which appears at the top of this page has been used to form the large "buttons" on the left of the ATNF home page.
Roy Duncan (duncan@atnf.csiro.au) Last updated: 10th August, 1999