Determining the H i content of galaxies via intensity mapping cross-correlations. Issue 3 (9th June 2017)

• Record Type: Journal Article
• Authors: Wolz, L.; Blake, C.; Wyithe, J. S. B.
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 470:Issue 3(2017)
• Page Start: 3220
• Page End: 3226
• Publication Date: 2017-06-09
• Subjects: galaxies: evolution -- large-scale structure of Universe -- radio lines: galaxies; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stx1388
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We propose an innovative method for measuring the neutral hydrogen (H i ) content of an optically selected spectroscopic sample of galaxies through cross-correlation with H i intensity mapping measurements. We show that the H i -galaxy cross-power spectrum contains an additive shot noise term that scales with the average H i brightness temperature of the optically selected galaxies, allowing constraints to be placed on the average H i mass per galaxy. This approach can estimate the H i content of populations too faint to directly observe through their 21-cm emission over a wide range of redshifts. This cross-correlation, as a function of optical luminosity or colour, can be used to derive H i -scaling relations. We demonstrate that this signal will be detectable by cross-correlating upcoming Australian Square Kilometre Array Pathfinder observations with existing optically selected samples. We also use semi-analytic simulations to verify that the H i mass can be successfully recovered by our technique in the range $M_{\rm H\, {\small I}} > 10^8 \, \mathrm{M}_{\odot }$, in a manner independent of the underlying power spectrum shape. We conclude that this method is a powerful tool to study galaxy evolution, which only requires a single intensity mapping data set to infer complementary H i gas information from existing optical and infrared observations.