Low-amplitude clustering in low-redshift 21-cm intensity maps cross-correlated with 2dF galaxy densities. Issue 3 (9th February 2018)

• Record Type: Journal Article
• Authors: Anderson, C J; Luciw, N J; Li, Y -C; Kuo, C Y; Yadav, J; Masui, K W; Chang, T-C; Chen, X; Oppermann, N; Liao, Y-W; Pen, U-L; Price, D C; Staveley-Smith, L; Switzer, E R; Timbie, P T; Wolz, L
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 476:Issue 3(2018)
• Page Start: 3382
• Page End: 3392
• Publication Date: 2018-02-09
• Subjects: line: identification -- galaxies: evolution -- large-scale structure of Universe; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty346
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We report results from 21-cm intensity maps acquired from the Parkes radio telescope and cross-correlated with galaxy maps from the 2dF galaxy survey. The data span the redshift range 0.057 < z < 0.098 and cover approximately 1300 deg 2 over two long fields. Cross-correlation is detected at a significance of 5.7 σ. The amplitude of the cross-power spectrum is low relative to the expected dark matter power spectrum, assuming a neutral hydrogen (H i ) bias and mass density equal to measurements from the ALFALFA survey. The decrement is pronounced and statistically significant at small scales. At k ∼ 1.5 h Mpc −1, the cross-power spectrum is more than a factor of 6 lower than expected, with a significance of 15.3 σ. This decrement indicates a lack of clustering of neutral hydrogen (H i ), a small correlation coefficient between optical galaxies and H i, or some combination of the two. Separating 2dF into red and blue galaxies, we find that red galaxies are much more weakly correlated with H i on k ∼ 1.5 h Mpc −1 scales, suggesting that H i is more associated with blue star-forming galaxies and tends to avoid red galaxies.