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

Howk, J. C.; Ribaudo, Joseph; Lehner, N.; Prochaska, J. Xavier; Chen, Hsiao‐Wen

doi:10.1111/j.1365-2966.2009.14805.x

Cited by 45 publications

(56 citation statements)

References 121 publications

(358 reference statements)

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“…However, it is difficult to compare our works directly since they use the Haardt & Madau (2012) (HM12) ionizing background. Previous works have shown that harder spectrum of ionizing photons from the HM12 background is due to a lower escape frac-tion of radiation from galaxies compared to the HM05 background, which leads to higher metallicity estimates and an anti-correlation between N(H I) and metallicity (Howk et al 2009;Werk et al 2014;Wotta et al 2016Wotta et al , 2019Chen et al 2017;Zahedy et al 2019;Pointon et al 2019a).…”

Section: Fig 5-same As Left Panel Ofmentioning

confidence: 99%

The Relationship between Galaxy ISM and Circumgalactic Gas Metallicities

Kacprzak

Pointon

Nielsen

et al. 2019

ApJ

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We present ISM and CGM metallicities for 25 absorption systems associated with isolated star-forming galaxies ( z = 0.28) with 9.4≤log(M * /M ⊙ )≤10.9 and with absorption detected within 200 kpc. Galaxy ISM metallicities were measured using Hα/[N II] emission lines from Keck/ESI spectra. CGM single-phase lowionization metallicities were modeled using MCMC and Cloudy analysis of absorption from HST/COS and Keck/HIRES or VLT/UVES quasar spectra. We find that the star-forming galaxy ISM metallicities follow the observed stellar mass metallicity relation (1σ scatter 0.19 dex). CGM metallicity shows no dependence with stellar mass and exhibits a scatter of ∼2 dex. All CGM metallicities are lower than the galaxy ISM metallicities and are offset by log(dZ) = −1.17 ± 0.11. There is no obvious metallicity gradient as a function of impact parameter or virial radius (< 2.3σ significance). There is no relationship between the relative CGM-galaxy metallicity and azimuthal angle. We find the mean metallicity differences along the major and minor axes are −1.13±0.18 and −1.23±0.11, respectively. Regardless of whether we examine our sample by low/high inclination or low/high impact parameter, or low/high N(H I), we do not find any significant relationship with relative CGM-galaxy metallicity and azimuthal angle. We find that 10/15 low column density systems (logN(H I)< 17.2) reside along the galaxy major axis while high column density systems (logN(H I)≥ 17.2) reside along the minor axis. This suggest N(H I) could be a useful indicator of accretion/outflows. We conclude that CGM is not well mixed, given the range of galaxy-CGM metallicities, and that metallicity at low redshift might not be a good tracer of CGM processes. On the-other-hand, we should replace integrated line-of-sight, single phase, metallicities with multi-phase, cloud-cloud metallicities, which could be more indicative of the physical processes within the CGM.

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Section: Fig 5-same As Left Panel Ofmentioning

confidence: 99%

The Relationship between Galaxy ISM and Circumgalactic Gas Metallicities

Kacprzak

Pointon

Nielsen

et al. 2019

ApJ

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“…This question has been addressed by numerous studies using both observational and theoretical arguments (Heckman et al 2002;Fox et al 2007;Thom & Chen 2008;Tripp et al 2008;Howk et al 2009;Oppenheimer & Davé 2009;Savage et al 2010Savage et al , 2011aSavage et al ,b, 2012Savage et al , 2014Narayanan et al 2010aNarayanan et al ,b, 2011Narayanan et al , 2012Fox 2011;Bordoloi et al 2016;Gutcke et al 2016;Oppenheimer et al 2016;Fielding et al 2016). In this work we assume O vi originates in the lowestdensity phase of the photoionized hierarchical structure (Figs.…”

Section: 3mentioning

confidence: 99%

A Universal Density Structure for Circumgalactic Gas

Stern

Hennawi

Prochaska

et al. 2016

ApJ

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130

157

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We develop a new method to constrain the physical conditions in the cool (∼ 10 4 K) circumgalactic medium (CGM) from measurements of ionic column densities, by assuming that the cool CGM spans a large range of gas densities and that small high-density clouds are hierarchically embedded in large low-density clouds. The new method combines the information available from different sightlines during the photoionization modeling, thus yielding tighter constraints on CGM properties compared to traditional methods which model each sightline individually. Applying this new technique to the COS-Halos survey of low-redshift ∼ L * galaxies, we find that we can reproduce all observed ion columns in all 44 galaxies in the sample, from the low-ions to O vi, with a single universal density structure for the cool CGM. The gas densities span the range 50 ρ/ρ b 5 × 10 5 (ρ b is the cosmic mean), while the physical size of individual clouds scales as ∼ ρ −1 , from ≈ 35 kpc of the low density O vi clouds to ≈ 6 pc of the highest density low-ion clouds. The deduced cloud sizes are too small for this density structure to be driven by self-gravity, thus its physical origin is unclear. The implied cool CGM mass within the virial radius is (1.3 ± 0.4) × 10 10 M (∼1% of the halo mass), distributed rather uniformly over the four decades in density. The mean cool gas density profile scales as R −1.0±0.3 , where R is the distance from the galaxy center. We construct a 3D model of the cool CGM based on our results, which we argue provides a benchmark for the CGM structure in hydrodynamic simulations. Our results can be tested by measuring the coherence scales of different ions.

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“…The analysis of observed metal‐line systems often yields inconclusive answers, with complex absorbers suggesting multiphase gas components (e.g. Prochaska et al 2004; Savage et al 2005; Danforth et al 2006; Cooksey et al 2008; Howk et al 2009; Narayanan, Wakker & Savage 2009). The higher signal‐to‐noise ratio (S/N) provided by the COS will be critical for disentangling these effects.…”

Section: Introductionmentioning

confidence: 99%

The intergalactic medium over the last 10 billion years - II. Metal-line absorption and physical conditions

Oppenheimer¹,

Davé²,

Katz³

et al. 2011

Monthly Notices of the Royal Astronomical Society

130

205

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We investigate the metallicity evolution and metal content of the intergalactic medium (IGM) and galactic halo gas from z= 2 to 0 using 110‐million‐particle cosmological hydrodynamic simulations. We focus on the detectability and physical properties of ultraviolet resonance metal‐line absorbers observable with Hubble’s Cosmic Origins Spectrograph (COS). We confirm that galactic superwind outflows are required to enrich the IGM to observed levels down to z= 0 using three wind prescriptions contrasted to a no‐wind simulation. Our favoured momentum‐conserved wind prescription deposits metals closer to galaxies owing to its moderate energy input, while the more energetic constant wind model enriches the warm‐hot IGM 6.4 times more. Despite these significant differences, all wind models produce metal‐line statistics within a factor of 2 of existing observations. This is because , , and absorbers primarily arise from T < 105 K, photoionized gas that is enriched to similar levels in the three feedback schemes. absorbers trace the diffuse phase with , which is enriched to ∼1/50 Z⊙ at z= 0, although the absorbers themselves usually exceed 0.3 Z⊙ and arise from inhomogeneously distributed, unmixed winds. Turbulent broadening is required to match the observed equivalent width and column density statistics for . and absorbers trace primarily T∼ 104 K gas inside haloes (), although there appear to be too many absorbers relative to observations. We predict the COS will observe a population of photoionized absorbers tracing T < 105 K, gas with equivalent widths of 10–20 mÅ. and are rarely detected in COS signal‐to‐noise ratio 30 simulated sight‐lines (dn/dz≪ 1), although simulated detections trace halo gas at T= 106–107 K. In general, the IGM is enriched in an outside‐in manner, where wind‐blown metals released at higher redshift reach lower overdensities, resulting in higher ionization species tracing lower density, older metals. At z= 0, 90 per cent of baryons outside galaxies are enriched to , but 65 per cent of unbound baryons in the IGM have and contain only 4 per cent of all metals, a large decline from 20 per cent at z= 2, because metals from early winds often re‐accrete on to galaxies while later winds are less likely to escape their haloes. We emphasize that our results are sensitive to how metal mixing is treated in the simulations, and argue that the lack of mixing in our scheme may be the largest difference from other similar publications.

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

Cited by 45 publications

References 121 publications

The Relationship between Galaxy ISM and Circumgalactic Gas Metallicities

The Relationship between Galaxy ISM and Circumgalactic Gas Metallicities

A Universal Density Structure for Circumgalactic Gas

The intergalactic medium over the last 10 billion years - II. Metal-line absorption and physical conditions

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

Cited by 45 publications

References 121 publications

The Relationship between Galaxy ISM and Circumgalactic Gas Metallicities

The Relationship between Galaxy ISM and Circumgalactic Gas Metallicities

A Universal Density Structure for Circumgalactic Gas

The intergalactic medium over the last 10 billion years - II. Metal-line absorption and physical conditions

Contact Info

Product

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