The spatial distribution of neutral hydrogen as traced by low HI mass galaxies

Han Seek Kim, J. Stuart B. Wyithe, C.M. Baugh, C. d. P. Lagos , C. Power, Jaehong Park

Research output: Contribution to journalArticle

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Abstract

The formation and evolution of galaxies with low neutral atomic hydrogen (H I) masses, MHI < 108 h-2 M, are affected by host dark matter halo mass and photoionization feedback from the UV background after the end of reionization. We study how the physical processes governing the formation of galaxies with low HI mass are imprinted on the distribution of neutral hydrogen in the Universe using the hierarchical galaxy formation model, GALFORM. We calculate the effect on the correlation function of changing the HI mass detection threshold at redshifts 0 ≤ z ≤ 0.5. We parametrize the clustering as ξ (r) = (r/r0) and we find that including galaxies with MHI < 108 h-2 M increases the clustering amplitude r0 and slope γ compared to samples of higher HI masses. This is due to these galaxies with low HI masses typically being hosted by haloes with masses greater than 1012 h-1 M, and is in contrast to optically selected surveys for which the inclusion of faint, blue galaxies lowers the clustering amplitude. We show the HI mass function for different host dark matter halo masses and galaxy types (central or satellite) to interpret the values of r0 and γ of the clustering of HIselected galaxies. We also predict the contribution of low HI mass galaxies to the 21 cm intensity mapping signal. We calculate that a dark matter halo mass resolution better than ~1010 h-1 M at redshifts higher than 0.5 is required in order to predict converged 21 cm brightness temperature fluctuations.

Original languageEnglish
Pages (from-to)111-122
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Volume465
Issue number1
DOIs
Publication statusPublished - 11 Feb 2017

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spatial distribution
hydrogen
galaxies
halos
dark matter
brightness temperature
galactic evolution
photoionization
universe
inclusions
slopes
thresholds

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Kim, Han Seek ; Wyithe, J. Stuart B. ; Baugh, C.M. ; Lagos , C. d. P. ; Power, C. ; Park, Jaehong. / The spatial distribution of neutral hydrogen as traced by low HI mass galaxies. In: Monthly Notices of the Royal Astronomical Society. 2017 ; Vol. 465, No. 1. pp. 111-122.
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The spatial distribution of neutral hydrogen as traced by low HI mass galaxies. / Kim, Han Seek; Wyithe, J. Stuart B.; Baugh, C.M.; Lagos , C. d. P.; Power, C.; Park, Jaehong.

In: Monthly Notices of the Royal Astronomical Society, Vol. 465, No. 1, 11.02.2017, p. 111-122.

Research output: Contribution to journalArticle

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T1 - The spatial distribution of neutral hydrogen as traced by low HI mass galaxies

AU - Kim, Han Seek

AU - Wyithe, J. Stuart B.

AU - Baugh, C.M.

AU - Lagos , C. d. P.

AU - Power, C.

AU - Park, Jaehong

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N2 - The formation and evolution of galaxies with low neutral atomic hydrogen (H I) masses, MHI < 108 h-2 M⊙, are affected by host dark matter halo mass and photoionization feedback from the UV background after the end of reionization. We study how the physical processes governing the formation of galaxies with low HI mass are imprinted on the distribution of neutral hydrogen in the Universe using the hierarchical galaxy formation model, GALFORM. We calculate the effect on the correlation function of changing the HI mass detection threshold at redshifts 0 ≤ z ≤ 0.5. We parametrize the clustering as ξ (r) = (r/r0)-γ and we find that including galaxies with MHI < 108 h-2 M⊙ increases the clustering amplitude r0 and slope γ compared to samples of higher HI masses. This is due to these galaxies with low HI masses typically being hosted by haloes with masses greater than 1012 h-1 M⊙, and is in contrast to optically selected surveys for which the inclusion of faint, blue galaxies lowers the clustering amplitude. We show the HI mass function for different host dark matter halo masses and galaxy types (central or satellite) to interpret the values of r0 and γ of the clustering of HIselected galaxies. We also predict the contribution of low HI mass galaxies to the 21 cm intensity mapping signal. We calculate that a dark matter halo mass resolution better than ~1010 h-1 M⊙ at redshifts higher than 0.5 is required in order to predict converged 21 cm brightness temperature fluctuations.

AB - The formation and evolution of galaxies with low neutral atomic hydrogen (H I) masses, MHI < 108 h-2 M⊙, are affected by host dark matter halo mass and photoionization feedback from the UV background after the end of reionization. We study how the physical processes governing the formation of galaxies with low HI mass are imprinted on the distribution of neutral hydrogen in the Universe using the hierarchical galaxy formation model, GALFORM. We calculate the effect on the correlation function of changing the HI mass detection threshold at redshifts 0 ≤ z ≤ 0.5. We parametrize the clustering as ξ (r) = (r/r0)-γ and we find that including galaxies with MHI < 108 h-2 M⊙ increases the clustering amplitude r0 and slope γ compared to samples of higher HI masses. This is due to these galaxies with low HI masses typically being hosted by haloes with masses greater than 1012 h-1 M⊙, and is in contrast to optically selected surveys for which the inclusion of faint, blue galaxies lowers the clustering amplitude. We show the HI mass function for different host dark matter halo masses and galaxy types (central or satellite) to interpret the values of r0 and γ of the clustering of HIselected galaxies. We also predict the contribution of low HI mass galaxies to the 21 cm intensity mapping signal. We calculate that a dark matter halo mass resolution better than ~1010 h-1 M⊙ at redshifts higher than 0.5 is required in order to predict converged 21 cm brightness temperature fluctuations.

KW - Galaxies: abundances

KW - Galaxies: formation

KW - Large-scale structure of Universe

KW - Radio lines: galaxies

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JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

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