Exploiting HI intensity maps in real space: a direct search for large-scale halos and filaments

Activity: Talk or presentationPresentation at conference/workshop/seminar


Cosmological exploitation of HI intensity maps via cross-correlations with galaxy catalogs is now an established technique, which has already been applied to data sets with different sky coverages and angular resolutions. An alternative and complementary approach consists in combining these data sets in real space, by stacking HI maps on galaxy positions: the result is a potential direct detection of the average features of the targeted structures. In this talk I will present the results of such a study, which employed 21-cm maps obtained with the Parkes radio telescope (spanning ~1,300 deg^2 on the sky and the redshift range 0.06<z<0.10), and the 2dF spectroscopic catalogue, which has an excellent overlap with the maps. Assuming galaxies are tracers of nodes in the cosmic web, we stacked ~48,000 2dF galaxies on the maps and detected the integrated galactic HI contribution from very massive halos, obtaining marginal differences when considering central and satellite subsamples; we employed the resulting HI radial profiles to test analytical models for the HI content in halos. We also coherently stacked ~275,000 pairs of 2dF galaxies potentially connected by intergalactic filaments, and explored the local presence of HI in the region connecting the member galaxies; although the study did not detect the presence of filamentary HI, it placed upper limits on the local HI column density in agreement with numerical simulations and previous detections of HI in the warm-hot intergalactic medium. These results prove the feasibility of this alternative technique to further exploit 21-cm intensity mapping data.
Period16 Jul 202322 Jul 2023
Held atNortheastern University China, China