When is stacking confusing? The impact of confusion on stacking in deep HI galaxy surveys

Michael G. Jones*, Martha P. Haynes, Riccardo Giovanelli, Emmanouil Papastergis

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

11 Citations (Scopus)
193 Downloads (Pure)

Abstract

We present an analytic model to predict the HI mass contributed by confused sources to a stacked spectrum in a generic HI survey. Based on the ALFALFA (Arecibo Legacy Fast ALFA) correlation function, this model is in agreement with the estimates of confusion present in stacked Parkes telescope data, and was used to predict how confusion will limit stacking in the deepest Square Kilometre Array precursor HI surveys. Stacking with LADUMA (Looking At the Distant Universe with MeerKAT) and DINGO UDEEP (Deep Investigation of Neutral Gas Origins - Ultra Deep) data will only be mildly impacted by confusion if their target synthesized beam size of 10 arcsec can be achieved. Any beam size significantly above this will result in stacks that contain a mass in confused sources that is comparable to (or greater than) that which is detectable via stacking, at all redshifts. CHILES (COSMOS HI Large Extragalactic Survey) 5 arcsec resolution is more than adequate to prevent confusion influencing stacking of its data, throughout its bandpass range. FAST (Five hundred metre Aperture Spherical Telescope) will be the most impeded by confusion, with HI surveys likely becoming heavily confused much beyond z = 0.1. The largest uncertainties in our model are the redshift evolution of the HI density of the Universe and the HI correlation function. However, we argue that the two idealized cases we adopt should bracket the true evolution, and the qualitative conclusions are unchanged regardless of the model choice. The profile shape of the signal due to confusion (in the absence of any detection) was also modelled, revealing that it can take the form of a double Gaussian with a narrow and wide component.

Original languageEnglish
Pages (from-to)1574-1583
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Volume455
Issue number2
DOIs
Publication statusPublished - 11-Jan-2016

Keywords

  • surveys
  • radio lines: galaxies
  • FAST ALPHA SURVEY
  • STAR-FORMING GALAXIES
  • MASS FUNCTION
  • FIELD GALAXIES
  • SKY SURVEY
  • I MASS
  • ALFALFA
  • TELESCOPE
  • CATALOG
  • GAS

Cite this