The book of cheese

Thom, Charles; Fisk, W. W.

doi:10.5962/bhl.title.40405

Cited by 21 publications

(34 citation statements)

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“…The observations reveal a multiphase, highly ionized and metalenriched CGM around present-day galaxies (also see Thom & Chen 2008b;Savage, Lehner & Narayanan 2011a;Savage et al 2011b;Wakker et al 2012). The high degree of enrichment demands that a large mass of gas (and metals) is transported from galaxies and/or their progenitors to the CGM.…”

Section: Introductionmentioning

confidence: 86%

magicc haloes: confronting simulations with observations of the circumgalactic medium at z=0

Stinson

Prochaska²,

Hennawi

et al. 2012

Monthly Notices of the Royal Astronomical Society

145

147

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We explore the circumgalactic medium (CGM) of two simulated star‐forming galaxies with luminosities L ≈ 0.1 and 1 L⋆ generated using the smooth particle hydrodynamic code gasoline. These simulations are part of the Making Galaxies In a Cosmological Context (magicc) program in which the stellar feedback is tuned to match the stellar mass–halo mass relationship. For comparison, each galaxy was also simulated using a ‘lower feedback’ (LF) model which has strength comparable to other implementations in the literature. The ‘magicc feedback’ (MF) model has a higher incidence of massive stars and an approximately two times higher energy input per supernova. Apart from the low‐mass halo using LF, each galaxy exhibits a metal‐enriched CGM that extends to approximately the virial radius. A significant fraction of this gas has been heated in supernova explosions in the disc and subsequently ejected into the CGM where it is predicted to give rise to substantial O vi absorption. The simulations do not yet address the question of what happens to the O vi when the galaxies stop forming stars. Our models also predict a reservoir of cool H i clouds that show strong Lyα absorption to several hundred kpc. Comparing these models to recent surveys with the Hubble Space Telescope, we find that only the MF models have sufficient O vi and H i gas in the CGM to reproduce the observed distributions. In separate analyses, these same MF models also show better agreement with other galaxy observables (e.g. rotation curves, surface brightness profiles and H i gas distribution). We infer that the CGM is the dominant reservoir of baryons for galaxy haloes.

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Section: Introductionmentioning

confidence: 86%

magicc haloes: confronting simulations with observations of the circumgalactic medium at z=0

Stinson

Prochaska²,

Hennawi

et al. 2012

Monthly Notices of the Royal Astronomical Society

145

147

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“…This is generally the case in all alignment statistics considered here, which indicates that the species are tracing the same underlying gas. This contrasts with, for instance, low-z O VI-H I alignment fractions which are markedly larger at higher δv (Thom & Chen 2008;Tripp et al 2008), because O VI traces physically distinct gas from the Lyα forest ).…”

Section: Aligned Absorber Ratiosmentioning

confidence: 95%

Tracing the re-ionization-epoch intergalactic medium with metal absorption lines

Oppenheimer¹,

Davé²,

Finlator³

2009

Monthly Notices of the Royal Astronomical Society

104

152

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Intergalactic medium (IGM) metal absorption lines observed in z≳ 6 spectra offer the opportunity to probe early feedback processes, the nature of enriching sources and the topology of re‐ionization. We run high‐resolution cosmological simulations including galactic outflows to study the observability and physical properties of five ions (C ii, C iv, O i, Si ii, Si iv) in absorption between z= 8 and 5. We apply three cases for ionization conditions: fully neutral, fully re‐ionized and a patchy model based on the flux from the nearest galaxy. We find that our simulations can broadly fit available z∼ 5–6 IGM metal‐line data, although all observations cannot be accommodated with a single ionization condition. Variations in O i absorbers among sight lines seen by Becker et al. suggest significant neutral IGM patches down to z∼ 6. Strong C iv absorbers at z∼ 6 may be the result of ionization by the galaxy responsible for that enrichment, although the identification of the neighbouring galaxy will have to wait to confirm this. Our outflows have typical speeds of ∼200 km s−1 and mass loading factors of ∼6. Such high mass loading is critical for enriching the IGM to the observed levels while sufficiently curtailing early star formation to match the observed rest‐frame ultraviolet luminosity function. The volume filling factor of metals increases during this epoch, but only reaches ∼1 per cent for Z > 10−3 Z⊙ by z= 5. Detectable absorbers generally trace inhomogeneously distributed metals residing outside of galactic haloes. C iv is an ideal tracer of IGM metals at z∼ 5–6, with dropping global ionization fractions to either higher or lower redshifts. This results in a strongly increasing global C iv mass density from z= 8 to 5, in contrast to its relative constancy from z= 5 to 2. Our simulations do not support widespread early IGM enrichment from e.g. Population III stars, as this would overpredict the numbers of weak C iv absorbers in the latest data. High‐z absorbers arise from metals mostly on their first outward journey, at distances 5–50 physical kpc, and often exhibit broad profiles (δv > 200 km s−1) as a result of outflowing peculiar velocities in the strongest systems. The galaxies responsible for early IGM enrichment have typical stellar masses of 107.0‐8.5 M⊙, and star formation rates ≲1 M⊙ yr−1. Future facilities will be able to study the high‐z galaxy–absorber connection in detail, revealing a wealth of information about feedback processes in the re‐ionization epoch.

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“…Intervening O VI absorption-line systems are quite common at low redshifts, with dN/dz ≈ 10-20 for W r 30 mÅ (Danforth & Shull 2008;Tripp et al 2008;Thom & Chen 2008a) depending on the criteria used to select the O VI systems. Thus, they probe a significant baryon reservoir no matter their origin.…”

Section: The Whim and Low-z O VI Systemsmentioning

confidence: 99%

“…The level of metal enrichment then suggests the sphere of influence over which galaxies affect the IGM, and it is an important consideration when using metal lines to calculate the baryon density of low-z IGM absorbers since in this case b ∝ Z −1 (e.g. Danforth & Shull 2008;Tripp et al 2008;Thom & Chen 2008a).…”

Section: Abundances and Ionization Mechanisms In The Low-z Igmmentioning

confidence: 99%

“…Tripp and collaborators first identified a number of O VI absorption-line systems at very low redshift (z < 0.3) with the Far Ultraviolet Spectroscopic Explorer (FUSE) and the STIS on board the Hubble Space Telescope (HST); though their statistical sample was small, these observations suggested a large number density of O VI absorbers at low z (Tripp, Savage & Jenkins 2000;. Recent surveys of O VI absorption at low redshift using a complete sample of STIS observations continue to find a very large population of absorbers (Tripp et al 2008; Thom & Chen 2008a;Danforth & Shull 2008). The number density of intervening O VI absorbers per unit redshift is dN O VI /dz ≈ 10-20 for equivalent widths W r (λ1031) > 30 mÅ, perhaps increasing to dN O VI /dz ∼ 40 for W r (λ1031) > 10 mÅ (Danforth & Shull 2008).…”

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confidence: 99%

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Strong z ∼ 0.5 O vi absorption towards PKS 0405−123: implications for ionization and metallicity of the Cosmic Web^★

Howk¹,

Ribaudo²,

Lehner³

et al. 2009

Monthly Notices of the Royal Astronomical Society

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We present observations of the intervening O vi absorption‐line system at zabs= 0.495 096 towards the quasi‐stellar object (QSO) PKS 0405−123 (zem= 0.5726) obtained with the Far Ultraviolet Spectroscopic Explorer and Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. In addition to strong O vi, with , and moderate H i, with , this absorber shows absorption from C iii, N iv, O iv and O v, with upper limits for another seven ions. The large number of available ions allows us to test ionization models usually adopted with far fewer constraints. We find that the observed ionic column densities cannot be matched by single‐temperature collisional ionization models, in or out of equilibrium. Photoionization models can match all of the observed column densities, including O vi. If one assumes photoionization by an ultraviolet (UV) background dominated by QSOs, the metallicity of the gas is [O/H]≈−0.15, while if one assumes a model for the UV background with contributions from ionizing photons escaping from galaxies the metallicity is [O/H]≈−0.62. Both give [N/O]∼−0.6 and [C/H]∼−0.2 to ∼−0.1, though a solar C/O ratio is not ruled out. The choice of ionizing spectrum is poorly constrained and leads to systematic abundance uncertainties of ≈0.5 dex, despite the wide range of available ions. Multiphase models with a contribution from both photoionized gas (at T∼ 104 K) and collisionally ionized gas [at T∼ (1−3) × 105 K] can also match the observations for either assumed UV background giving very similar metallicities. We do not detect Ne viii or Mg x absorption. The limit on Ne viii/O vi< 0.21 (3σ) is the lowest yet observed. Thus, this absorber shows no firm evidence of the ‘warm‐hot intergalactic medium’ at T∼ (0.5–3) × 106 K thought to contain a significant fraction of the baryons at low redshift. The O vi in this system is not necessarily a reliable tracer of the warm‐hot intergalactic medium given the ambiguity in its origins. We present limits on the total column of warm‐hot gas in this absorber as a function of temperature. This system would be unlikely to provide detectable X‐ray absorption in the ions O vii or O viii even if it resided in front of the brighter X‐ray sources in the sky.

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The book of cheese

Cited by 21 publications

References 0 publications

magicc haloes: confronting simulations with observations of the circumgalactic medium at z=0

magicc haloes: confronting simulations with observations of the circumgalactic medium at z=0

Tracing the re-ionization-epoch intergalactic medium with metal absorption lines

Strong z ∼ 0.5 O vi absorption towards PKS 0405−123: implications for ionization and metallicity of the Cosmic Web^★

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The book of cheese

Cited by 21 publications

References 0 publications

magicc haloes: confronting simulations with observations of the circumgalactic medium at z=0

magicc haloes: confronting simulations with observations of the circumgalactic medium at z=0

Tracing the re-ionization-epoch intergalactic medium with metal absorption lines

Strong z ∼ 0.5 O vi absorption towards PKS 0405−123: implications for ionization and metallicity of the Cosmic Web★

Contact Info

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Strong z ∼ 0.5 O vi absorption towards PKS 0405−123: implications for ionization and metallicity of the Cosmic Web^★