Solar-metallicity gas in the extended halo of a galaxy at <i>z</i> ∼ 0.12

Pradeep, Jayadev; Sankar, Sriram; Umasree, T. M.; Narayanan, A.; Khaire, Vikram; Gebhardt, Matthew; Sameer,; Charlton, Jane C.

doi:10.1093/mnras/staa184

Cited by 6 publications

(3 citation statements)

References 159 publications

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“…For example, we would typically optimize on Mg for the low-ionization gas, and on C for high-ionization gas. In some intervening absorbers, O , because of its comparatively high ionization potential (∼ 114 eV), arises in gas with T > 10 5 K where the ionization is governed by collisions between energetic free electrons and metal ions (Pradeep et al 2020). We model the gas phase traced by O to be under collisional ionization equilibrium (CIE).…”

Section: Methodsmentioning

confidence: 99%

Cloud-by-cloud, multiphase, Bayesian modelling: application to four weak, low-ionization absorbers

Sameer

Charlton

Norris

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present a new method aimed at improving the efficiency of component by component ionization modelling of intervening quasar absorption-line systems. We carry out cloud-by-cloud, multiphase modelling making use of cloudy and Bayesian methods to extract physical properties from an ensemble of absorption profiles. Here, as a demonstration of method, we focus on four weak, low-ionization absorbers at low redshift, because they are multiphase but relatively simple to constrain. We place errors on the inferred metallicities and ionization parameters for individual clouds, and show that the values differ from component to component across the absorption profile. Our method requires user input on the number of phases and relies on an optimized transition for each phase, one observed with high resolution and signal-to-noise ratio. The measured Doppler parameter of the optimized transition provides a constraint on the Doppler parameter of H i, thus providing leverage in metallicity measurements even when hydrogen lines are saturated. We present several tests of our methodology, demonstrating that we can recover the input parameters from simulated profiles. We also consider how our model results are affected by which radiative transitions are covered by observations (for example, how many H i transitions) and by uncertainties in the b parameters of optimized transitions. We discuss the successes and limitations of the method, and consider its potential for large statistical studies. This improved methodology will help to establish direct connections between the diverse properties derived from characterizing the absorbers and the multiple physical processes at play in the circumgalactic medium.

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Section: Methodsmentioning

confidence: 99%

Cloud-by-cloud, multiphase, Bayesian modelling: application to four weak, low-ionization absorbers

Sameer

Charlton

Norris

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…Previous studies of C and Si absorbers with associated C suggest a photoionized two-phase structure with the low-ions coming from a dense and compact region (𝑛 H 10 −3 cm −3 , ∼ parsec), and the high ions traced by C coming from a more diffuse and extended region (𝑛 H < 10 −3 cm −3 , ∼ few hundred pc to kpc (e.g. Rigby et al 2002;Ding et al 2003;Pradeep et al 2020). Such a scenario could be true for some of the absorbers in our sample as well.…”

Section: Ionization Modellingmentioning

confidence: 97%

The COS-legacy survey of C IV absorbers: properties and origins of the intervening systems

Manuwal,

Narayanan,

Udhwani

et al. 2021

Preprint

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We present here results from a survey of intervening C absorbers at 𝑧 < 0.16 conducted using 223 sightlines from the Hubble Spectroscopic Legacy Archive. Most systems (83%) out of the total sample of 69 have simple kinematics with 1 or 2 C components. In the 22 C systems with well constrained H column densities, the temperatures from the 𝑏-values imply predominantly photoionized plasma (𝑇 ≤ 10 5 K) and non-thermal dynamics. These systems also have solar or higher metallicities. We obtain a C line density of 𝑑N /𝑑𝑋 = 5.1±1.0 for log[𝑁 (C ) (cm −2 )] ≥ 12.9, and Ω C = (8.01±1.62) ×10 −8 for 12.9 ≤ log[𝑁 (C ) (cm −2 )] ≤ 15.0. The C bearing diffuse gas in the 𝑧 < 0.16 Universe has a metallicity of (2.07 ± 0.43) × 10 −3 Z , an order of magnitude more than the metal abundances in the IGM at high redshifts (𝑧 5), and consistent with the slow build-up of metals in the diffuse circum/intergalactic space with cosmic time. For 𝑧 < 0.015 (complete above 𝐿 > 0.01𝐿 ★ ), the Sloan Digital Sky Survey provides a tentative evidence of declining covering fraction for strong C (𝑁 > 10 13.5 cm −2 ) with 𝜌 (impact parameter) and 𝜌/𝑅 vir . However, the increase at high separations suggests that strong systems are not necessarily coincident with such galaxies. We also find that strong C absorption at 𝑧 < 0.051 is not coincident with galaxy over-dense regions complete for 𝐿 > 0.13𝐿 ★ .

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“…The multiphase properties are many a times brought out by the diversity of metal lines featured in spectroscopic observations. For example, the presence of a diffuse warm (T 10 5 K) component to the CGM is known through absorption from high ions such as O VI and Ne VIII, whereas concurrent detections of lower ionization species such as C II and Si II reveals much cooler T 10 4 K CGM gas phases in the same environment (Savage et al 2011, Pachat et al 2017, Narayanan et al 2018, Pradeep et al 2020. The scale height of these low and high ions also serve to define a boundary to the chemically enriched CGM within the dark matter envelope of galaxies (Liang & Chen 2014, Liang et al 2016, (See also Project AMIGA - Lehner et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Physical Conditions of Five O VI Absorption Systems Towards PG $1522+101$

Sankar,

Narayanan,

Savage

et al. 2020

Preprint

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We present the analysis of five O VI absorbers identified across a redshift path of z ∼ (0.6 − 1.3) towards the background quasar PG 1522 + 101 with information on five consecutive ionization stages of oxygen from O II to O VI. The combined HST and Keck spectra cover UV, redshifted EUV, and optical transitions from a multitude of ions spanning ionization energies in the range of ∼ (13 − 300) eV. Low ionization (C II, O II, Si II, Mg II) and very high ionization species (Ne VIII, Mg X) are non-detections in all the absorbers. Three of the absorbers have coverage of He I, in one of which it is a > 3σ detection. The kinematic structures of these absorbers are extracted from C IV detected in HI RE S spectra. The farthest absorber in our sample also contains the detections of Ne V and Ne VI. Assuming co-spatial absorbing components, the ionization models show the medium to be multiphased with smallscale density-temperature inhomogeneities that are sometimes kinematically unresolved. In two of the absorbers, there is an explicit indication of the presence of a warm gas phase (T 10 5 K) traced by O VI. In the remaining absorbers, the column densities of the ions are consistent with a non-uniform photoionized medium. The sub-solar [C/O] relative abundances inferred for the absorbers point at enrichment from massive Type II supernovae. Despite metal enrichment, the inferred wide range for [O/H] ∼ [−2.1, +0.2] amongst the absorbers along with their anti-correlation with the observed H I suggest poor small-scale mixing of metals with hydrogen in the regions surrounding galaxies and the IGM.

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Solar-metallicity gas in the extended halo of a galaxy at z ∼ 0.12

Cited by 6 publications

References 159 publications

Cloud-by-cloud, multiphase, Bayesian modelling: application to four weak, low-ionization absorbers

Cloud-by-cloud, multiphase, Bayesian modelling: application to four weak, low-ionization absorbers

The COS-legacy survey of C IV absorbers: properties and origins of the intervening systems

Physical Conditions of Five O VI Absorption Systems Towards PG $1522+101$

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