Skip to main content
SpringerLink
Log in

Weighting interferometric data for direct imaging

  • Original Article
  • Published:
Experimental Astronomy Aims and scope Submit manuscript

Abstract

The new generation interferometric arrays such as the Atacama Large Millimeter/submillimeter Array (ALMA) are composed of a large number of telescopes and their configurations are optimized for Fourier plane (a.k.a. uv-plane) coverage. As a consequence, solving for the missing information in the uv-plane is becoming less critical and the imaging algorithms can be revisited. The situation is getting similar to that encountered with single filled aperture telescopes and it is becoming possible to make images in a direct way. In this article a new weighting method is introduced to obtain “pseudo-clean” images without using prior information to solve for the Fourier transform of the source. This method is similar but not equivalent to the successive application of robust weighting and tapering at different scales. The idea is to weight the data to compensate for the imperfect distribution of natural weights in the uv-plane. The price to pay for this direct imaging technique is that the final point spread function (PSF or beam) may not follow a simple analytical shape such as a Gaussian (but this is also the case in optical astronomy) and some sensitivity is lost (but this is the case with any imaging algorithm in interferometry). Two parameters are introduced to control the trade-off between imaging quality and sensitivity, namely a threshold parameter and a coupling parameter. This method is applied to simulated ALMA observations with 16, 32 and 50 antennas. As expected this method is found to be more efficient with more antennas and for more compact configurations because the uv-plane coverage is more complete. With 50 antennas in compact configuration it is possible to reduce the amplitude of the inner sidelobes (outer sidelobes) by a factor >6 (>2) compared to natural weighting for ~10 % loss in sensitivity, leading to sidelobes lower than 1.6 % of the main lobe peak value. With 16 antennas only, the method can still be used to reduce the inner sidelobes of a compact configuration by a factor >2 for ~10 % loss in sensitivity. This method can therefore be used with the new generation interferometric arrays to efficiently produce images without relying on any assumptions about the sources. The dynamic range of the resulting images depend on the number of telescopes in the array, the source size and the acceptable level of sensitivity loss.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Fig. 12
Fig. 13
Fig. 14
Fig. 15
Fig. 16
Fig. 17
Fig. 18
Fig. 19

Similar content being viewed by others

References

  1. Boone, F.: Interferometric array design: optimizing the locations of the antenna pads. A&A 377, 368 (2001)

    Article  ADS  Google Scholar 

  2. Boone, F.: Interferometric array design: distributions of Fourier samples for imaging. A&A 386, 1160 (2002)

    Article  ADS  Google Scholar 

  3. Briggs, D.S.: The New Mexico Institute Of Mining and Technology. PhD Thesis (1995)

  4. Cornwell, T., Braun, R.: In astronomical society of the pacific conference series. In: Perley, R.A., Schwab, F.R., Bridle, A.H. (eds.) Synthesis Imaging in Radio Astronomy, vol. 6, p. 167. (1989)

  5. Högbom, J.A.: Aperture synthesis with a non-regular distribution of interferometer baselines. A&AS 15, 417 (1974)

    ADS  Google Scholar 

  6. Lannes, A., Anterrieu, É., Bouyoucef, K.: Fourier interpolation and reconstruction via Shannon-type techniques: I. regularization principle. J. Mod. Opt. 41, 1537 (1994)

    Article  MathSciNet  ADS  MATH  Google Scholar 

  7. Lannes, A., Anterrieu, E., Marechal, P.: Clean and wipe. A&AS 123, 183 (1997)

    Article  ADS  Google Scholar 

  8. Narayan, R., Nityananda, R.: Maximum entropy image restoration in astronomy. ARA&A 24, 127 (1986)

    Article  ADS  Google Scholar 

  9. Thompson, A.R., Moran, J.M., Swenson, G.W. (eds.): Interferometry and synthesis in radio astronomy, 2007. John Wiley & Sons (2007)

Download references

Acknowledgements

I thank the two anonymous referees for their insightful comments and suggestions that helped to considerably improve the quality of the paper. I am grateful to the ALMA AIVC team members and in particular to Richard Hills, Stéphane Léon-Tanne, Ruediger Kneissl, Ed Fomalont, and Eric Villard for their interest in this work and their useful remarks.

Author information

Authors and Affiliations

  1. Université de Toulouse; UPS-OMP; IRAP, Toulouse, France

    Frédéric Boone

  2. CNRS; IRAP, 9 Av. colonel Roche, BP 44346, 31028, Toulouse cedex 4, France

    Frédéric Boone

  3. LERMA, Observatoire de Paris, 61 av. de l’Observatoire, 75014, Paris, France

    Frédéric Boone

Authors
  1. Frédéric Boone
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Frédéric Boone.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Boone, F. Weighting interferometric data for direct imaging. Exp Astron 36, 77–104 (2013). https://doi.org/10.1007/s10686-012-9322-1

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s10686-012-9322-1

Keywords

Search

Navigation