Ly-α and Mg II as Probes of Galaxies and Their Environment

Barnes, Luke A.; Garel, Thibault; Kacprzak, Glenn G.

doi:10.1086/679178

Cited by 30 publications

(28 citation statements)

References 596 publications

(807 reference statements)

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“…Whereas, molecular gas, which is often considered a tracer for star-formation, is detected at mm/sub-mm wavelengths (Emonts et al 2015). The neutral hydrogen component of the CGM can be parametrised by tracing Lyα emission and absorption when H i cannot be directly detected via the 21 cm line (e.g., Barnes et al 2014).…”

Section: Introductionmentioning

confidence: 99%

MUSE unravels the ionisation and origin of metal-enriched absorbers in the gas halo of a z = 2.92 radio galaxy

Kolwa

Vernet

Breuck

et al. 2019

A&A

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We have used the Multi-Unit Spectroscopic Explorer (MUSE) to study the circumgalactic medium (CGM) of a z = 2.92 radio galaxy, MRC 0943-242 by parametrising its emitting and absorbing gas. In both Lyα λ1216 and He ii λ1640 lines, we observe emission with velocity shifts of ∆ −1000 km s −1 from the systemic redshift of the galaxy. These blueshifted components represent kinematically perturbed gas that is aligned with the radio axis, which we interpret as jet-driven outflows. Three of the four known Lyα absorbers are detected at the same velocity as C iv λλ1548, 1551 and N v λλ1239, 1243 absorbers, proving that the gas is metal enriched more so than previously thought. At the velocity of a strong Lyα absorber with an H i column of N H i /cm −2 = 10 19.2 and velocity shift of ∆ −400 km s −1 , we also detect Si ii λ1260 and Si ii λ1527 absorption, which suggests that the absorbing gas is ionisation bounded. With the added sensitivity of this MUSE observation, we are more capable of adding constraints to absorber column densities and consequently determining what powers their ionisation. To do this, we obtain photoionisation grid models in cloudy which show that AGN radiation is capable of ionising the gas and producing the observed column densities in a gas of metallicity of Z/Z 0.01 with a nitrogen abundance a factor of 10 greater than that of hydrogen. This metal-enriched absorbing gas, which is also spatially extended over a projected distance of r 60 kpc, is likely to have undergone chemical enrichment through stellar winds that have swept up metals from the interstellar-medium and deposited them in the outer regions of the galaxy's halo.

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Section: Introductionmentioning

confidence: 99%

MUSE unravels the ionisation and origin of metal-enriched absorbers in the gas halo of a z = 2.92 radio galaxy

Kolwa

Vernet

Breuck

et al. 2019

A&A

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“…Recently, instruments such as MUSE (Bacon et al 2010) reveal the ubiquity of Lyα emission throughout the observable space. In particular, Lyα is used to study our galactic neighborhood (Hayes 2015), galaxies at the peak of cosmic star formation (Barnes et al 2014), and the later stages of reionization (Dijkstra 2014).…”

Section: Introductionmentioning

confidence: 99%

Resonant line transfer in a fog: using Lyman-alpha to probe tiny structures in atomic gas

Grönke

Dijkstra

McCourt

et al. 2017

A&A

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Motivated by observational and theoretical work which both suggest very small scale ( 1 pc) structure in the circumgalactic medium of galaxies and in other environments, we study Lyman-α (Lyα) radiative transfer in an extremely clumpy medium with many "clouds" of neutral gas along the line of sight. While previous studies have typically considered radiative transfer through sightlines intercepting 10 clumps, we explore the limit of a very large number of clumps per sightline (up to fc ∼ 1000). Our main finding is that, for covering factors greater than some critical threshold, a multiphase medium behaves similar to a homogeneous medium in terms of the emergent Lyα spectrum. The value of this threshold depends on both the clump column density and on the movement of the clumps. We estimate this threshold analytically and compare our findings to radiative transfer simulations with a range of covering factors, clump column densities, radii, and motions. Our results suggest that (i) the success in fitting observed Lyα spectra using homogeneous "shell models" (and the corresponding failure of multiphase models) hints towards the presence of very small-scale structure in neutral gas, in agreement within a number of other observations; and (ii) the recurrent problems of reproducing realistic line profiles from hydrodynamical simulations may be due to their inability to resolve small-scale structure, which causes simulations to underestimate the effective covering factor of neutral gas clouds.

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“…Under pressure equilibrium, the neutral gas naturally segregates into two distinct temperature phases: a cold (T ∼ 100 K) neutral medium (CNM) and a warm (T ∼ 10 3 − 10 4 K) neutral medium (WNM) as characterised locally in the canonical two-phase model (e.g., Field et al 1969;Wolfire et al 1995). In the distant Universe, the neutral gas phase is most readily accessible through observations of damped Lyα absorbers (DLAs; Wolfe et al 1986; Barnes et al 2014), which make up the class of the highest column density Lyα absorbers defined as having N H i > 2×10 20 cm −2 . However, as the presence and strength of Lyα absorption does not depend on temperature, the Lyα line alone does not constrain the relative contribution of CNM and WNM in DLAs.…”

Section: Introductionmentioning

confidence: 99%

Dissecting cold gas in a high-redshift galaxy using a lensed background quasar

Krogager

Noterdaeme

O’Meara

et al. 2018

A&A

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We present a study of cold gas absorption from a damped Lyman-α absorber (DLA) at redshift z abs = 1.946 towards two lensed images of the quasar J144254.78+405535.5 at redshift zqso = 2.590. The physical separation of the two lines of sight at the absorber redshift is d abs = 0.7 kpc based on our lens model. We observe absorption lines from neutral carbon and H2 along both lines of sight indicating that cold gas is present on scales larger than d abs . We measure column densities of H i to be log N (H i) = 20.27 ± 0.02 and 20.34 ± 0.05 and of H2 to be log N (H2) = 19.7 ± 0.1 and 19.9 ± 0.2. The metallicity inferred from sulphur is consistent with Solar metallicity for both sightlines: [S/H]A = 0.0 ± 0.1 and [S/H]B = −0.1 ± 0.1. Based on the excitation of low rotational levels of H2, we constrain the temperature of the cold gas phase to be T = 109 ± 20 and T = 89 ± 25 K for the two lines of sight. From the relative excitation of fine-structure levels of C i, we constrain the hydrogen volumetric densities in the range of 40 − 110 cm −3 . Based on the ratio of observed column density and volumetric density, we infer the average individual 'cloud' size along the line of sight to be l ≈ 0.1 pc. Using the transverse line-of-sight separation of 0.7 kpc together with the individual cloud size, we are able to put an upper limit to the volume filling factor of cold gas of f vol < 0.2 %. Nonetheless, the projected covering fraction of cold gas must be large (close to unity) over scales of a few kpc in order to explain the presence of cold gas in both lines of sight. Compared to the typical extent of DLAs (∼ 10 − 30 kpc), this is consistent with the relative incidence rate of C i absorbers and DLAs.

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Ly-α and Mg II as Probes of Galaxies and Their Environment

Cited by 30 publications

References 596 publications

MUSE unravels the ionisation and origin of metal-enriched absorbers in the gas halo of a z = 2.92 radio galaxy

MUSE unravels the ionisation and origin of metal-enriched absorbers in the gas halo of a z = 2.92 radio galaxy

Resonant line transfer in a fog: using Lyman-alpha to probe tiny structures in atomic gas

Dissecting cold gas in a high-redshift galaxy using a lensed background quasar

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