The potential of tracing the star formation history with H I 21-cm in intervening absorption systems

Curran, S. J.

doi:10.1051/0004-6361/201731666

Cited by 9 publications

(10 citation statements)

References 93 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…where τ obs dv [km s −1 ] is the observed velocity integrated optical depth of the 21-cm absorption. For the associated absorbers, the column densities are generally not available but, using the method of Curran (2017b), if we assume that the associated absorbers follow the same evolution of the cosmological mass density as the intervening absorbers, then from ΩH I = 4.0 × 10 −4 (z abs + 1) 0.60 (Crighton et al 2017) and the redshift number density of damped Lyman-α absorption systems nDLA = 0.027(z + 1) 1.682 (Rao et al 2017)…”

Section: Spin Temperaturementioning

confidence: 99%

“…4 The UV continuum in Quasi-Stellar Objects (QSOs) is seen to follow a broken power law, with a break close to λ = 1200 Å and spectral indices of α NUV ≈ −1 and α EUV ≈ −2 at λ > ∼ 1200 Å and λ < ∼ 1200 Å, respectively (see Shull et al 2012 and references therein). to an exponential gas disk, yields a scale-length of R = 2.8 kpc for QH I = 4.8 × 10 56 sec −1 , using the canonical gas temperature of 2000 K, or R = 2.1 kpc, using the T = 500 K typical of intervening systems (Curran et al 2016c;Curran 2017b). This compares to 3.15 kpc for the Milky Way (Kalberla & Kerp 2009), showing that an ionising rate of QH I = 4.8 × 10 56 sec −1 is insufficient to completely ionise the gas in a large spiral, thus not requiring a re-evaluation of the critical ionising photon rate.…”

Section: Ultra-violetmentioning

confidence: 99%

See 1 more Smart Citation

The mid-infrared properties and gas content of active galaxies over large lookback times

Curran

Duchesne

2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Upon an expansion of all of the searches for redshifted H I 21-cm absorption (0.0021 z 5.19), we update recent results regarding the detection of 21-cm in the non-local Universe. Specifically, we confirm that photo-ionisation of the gas is the mostly likely cause of the low detection rate at high redshift, in addition to finding that at z < ∼ 0.1 there may also be a decrease in the detection rate, which we suggest is due to the dilution of the absorption strength by 21-cm emission. By assuming that associated and intervening absorbers have similar cosmological mass densities, we find evidence that the spin temperature of the gas evolves with redshift, consistent with heating by ultra-violet photons. From the near-infrared (λ = 3.4, 4.6 and 12 µm) colours, we see that radio galaxies become more quasar-like in their activity with increasing redshift. We also find that the non-detection of 21-cm absorption at high redshift is not likely to be due to the selection of gas-poor ellipticals, in addition to a strong correlation between the ionising photon rate and the [3.4] − [4.6] colour, indicating that the UV photons arise from AGN activity. Like previous studies, we find a correlation between the detection of 21-cm absorption and the [4.6] − [12] colour, which is a tracer of star-forming activity. However, this only applies at the lowest redshifts (z < ∼ 0.1), the range considered by the other studies.

show abstract

Section: Spin Temperaturementioning

confidence: 99%

Section: Ultra-violetmentioning

confidence: 99%

The mid-infrared properties and gas content of active galaxies over large lookback times

Curran

Duchesne

2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…A statistical value for use in Equ. 5 may, however, be derived from the cosmological H I density (Curran, 2017b).…”

Section: Prospects With the Square Kilometre Arraymentioning

confidence: 99%

“…The other issue with avoiding optical pre-selection is the lack of a Lyman-α spectrum from which to determine the total neutral hydrogen column density. A statistical value for use in Equation (5) may, however, be derived from the cosmological H I density (Curran 2017b).…”

Section: Prospects With the Skamentioning

confidence: 99%

See 1 more Smart Citation

Evolution of the cold gas fraction and the star formation history: Prospects with current and future radio facilities

Curran

2018

Publ. Astron. Soc. Aust.

Self Cite

View full text Add to dashboard Cite

It has recently been shown that the abundance of cold neutral gas may follow a similar evolution as the star formation history. This is physically motivated, since stars form out of this component of the neutral gas and if the case, would resolve the longstanding issue that there is a clear disparity between the total abundance of neutral gas and star forming activity over the history of the Universe. Radio-band 21-cm absorption traces the cold gas and comparison with the Lyman-α absorption, which traces all of the gas, provides a measure of the cold gas fraction, or the spin temperature, Tspin. The recent study has shown that the spin temperature (degenerate with the ratio of the absorber/emitter extent) appears to be anti-correlated with the star formation density, ψ * , with 1/Tspin undergoing a similar steep evolution as ψ * over redshifts of 0 < ∼ z < ∼ 3, whereas the total neutral hydrogen exhibits little evolution. Above z ∼ 3, where ψ * shows a steep decline with redshift, there is insufficient 21-cm data to determine whether 1/Tspin continues to follow ψ * . Knowing this is paramount in ascertaining whether the cold neutral gas does trace the star formation over the Universe's history. We explore the feasibility of resolving this with 21-cm observations of the largest contemporary sample of reliable damped Lyman-α absorption systems and conclude that, while today's largest radio interferometers can reach the required sensitivity at z < ∼ 3.5, the Square Kilometre Array is required to probe to higher redshifts.

show abstract

The evolution of neutral hydrogen over the past 11 Gyr via H i 21 cm absorption

Grasha

Darling

Leroy

et al. 2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We present the results of a blind search for intervening H i 21 cm absorption toward 260 radio sources in the redshift range 0 < z < 2.74 with the Green Bank Telescope. The survey has the sensitivity to detect sub-damped Lyman-alpha (DLA) systems for H i spin temperatures Ts/f = 100 K, and despite the successful re-detection of ten known 21 cm absorbers in the sample, we detect no new absorption lines in the full survey. Sources detected in 21 cm absorption were also searched for hydroxyl (OH) 18 cm absorption and we re-detect 1667 MHz OH absorption toward PKS 1830-211. We searched for intervening H i 21 cm absorption along the line of sight in each source achieving a total redshift coverage of Δz = 88.64 (comoving absorption path of ΔX = 159.5) after removing regions affected by radio frequency interference. We compute a 95% confidence upper limit on the column density frequency distribution f(NHI) and set a statistical constraint on the spin temperature Ts in the range 100–1000 K, consistent with prior redshifted optical DLA surveys and H i 21 cm emission observations at the same redshifts. We infer a value for the cosmological mass density of neutral gas, ΩHI. Through comparison with prior ΩHI measurements, we place a statistical constraint on the mean spin temperature of Ts/f = 175 K. Our derived ΩHI values support a relative mild evolution in ΩHI over the last 11 Gyr and are consistent with other methods that measure ΩHI.

show abstract

The potential of tracing the star formation history with H I 21-cm in intervening absorption systems

Cited by 9 publications

References 93 publications

The mid-infrared properties and gas content of active galaxies over large lookback times

The mid-infrared properties and gas content of active galaxies over large lookback times

Evolution of the cold gas fraction and the star formation history: Prospects with current and future radio facilities

The evolution of neutral hydrogen over the past 11 Gyr via H i 21 cm absorption

Contact Info

Product

Resources

About