A statistical measurement of the H I spin temperature in DLAs at cosmological distances
Evolution of the cosmic star formation rate (SFR) and molecular gas mass density is expected to be matched by a similarly strong evolution of the fraction of atomic hydrogen (H I) in the cold neutral medium (CNM). We use results from a recent commissioning survey for intervening 21-cm absorbers with...
| Main Author: | |
|---|---|
| Format: | Journal article |
| Language: | English |
| Published: |
Oxford University Press
2021
|
| _version_ | 1797081875313852416 |
|---|---|
| author | Allison, JR |
| author_facet | Allison, JR |
| author_sort | Allison, JR |
| collection | OXFORD |
| description | Evolution of the cosmic star formation rate (SFR) and molecular gas mass density is expected to be matched by a similarly strong evolution of the fraction of atomic hydrogen (H I) in the cold neutral medium (CNM). We use results from a recent commissioning survey for intervening 21-cm absorbers with the Australian Square Kilometre Array Pathfinder (ASKAP) to construct a Bayesian statistical model of the NH I-weighted harmonic mean spin temperature (Ts) at redshifts between z = 0.37 and 1.0. We find that Ts ≤ 274 K with 95 per cent probability, suggesting that at these redshifts the typical H I gas in galaxies at equivalent DLA column densities may be colder than the Milky Way interstellar medium (Ts, MW ∼ 300 K). This result is consistent with an evolving CNM fraction that mirrors the molecular gas towards the SFR peak at z ∼ 2. We expect that future surveys for H I 21-cm absorption with the current SKA pathfinder telescopes will provide constraints on the CNM fraction that are an order of magnitude greater than presented here.
|
| first_indexed | 2024-03-07T01:20:14Z |
| format | Journal article |
| id | oxford-uuid:900f2ff8-d694-4a87-b530-311cdc29ddcf |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T01:20:14Z |
| publishDate | 2021 |
| publisher | Oxford University Press |
| record_format | dspace |
| spelling | oxford-uuid:900f2ff8-d694-4a87-b530-311cdc29ddcf2022-03-26T23:08:57ZA statistical measurement of the H I spin temperature in DLAs at cosmological distancesJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:900f2ff8-d694-4a87-b530-311cdc29ddcfEnglishSymplectic ElementsOxford University Press2021Allison, JREvolution of the cosmic star formation rate (SFR) and molecular gas mass density is expected to be matched by a similarly strong evolution of the fraction of atomic hydrogen (H I) in the cold neutral medium (CNM). We use results from a recent commissioning survey for intervening 21-cm absorbers with the Australian Square Kilometre Array Pathfinder (ASKAP) to construct a Bayesian statistical model of the NH I-weighted harmonic mean spin temperature (Ts) at redshifts between z = 0.37 and 1.0. We find that Ts ≤ 274 K with 95 per cent probability, suggesting that at these redshifts the typical H I gas in galaxies at equivalent DLA column densities may be colder than the Milky Way interstellar medium (Ts, MW ∼ 300 K). This result is consistent with an evolving CNM fraction that mirrors the molecular gas towards the SFR peak at z ∼ 2. We expect that future surveys for H I 21-cm absorption with the current SKA pathfinder telescopes will provide constraints on the CNM fraction that are an order of magnitude greater than presented here. |
| spellingShingle | Allison, JR A statistical measurement of the H I spin temperature in DLAs at cosmological distances |
| title | A statistical measurement of the H I spin temperature in DLAs at cosmological distances |
| title_full | A statistical measurement of the H I spin temperature in DLAs at cosmological distances |
| title_fullStr | A statistical measurement of the H I spin temperature in DLAs at cosmological distances |
| title_full_unstemmed | A statistical measurement of the H I spin temperature in DLAs at cosmological distances |
| title_short | A statistical measurement of the H I spin temperature in DLAs at cosmological distances |
| title_sort | statistical measurement of the h i spin temperature in dlas at cosmological distances |
| work_keys_str_mv | AT allisonjr astatisticalmeasurementofthehispintemperatureindlasatcosmologicaldistances AT allisonjr statisticalmeasurementofthehispintemperatureindlasatcosmologicaldistances |