Using cosmological simulations and synthetic absorption spectra to assess the accuracy of observationally derived CGM metallicities

Abstract

We used adaptive mesh refinement hydrodynamic cosmological simulations of a $z=1$ Milky Way-type galaxy and a $z=0$ Dwarf galaxy and generated synthetic quasar absorption-line spectra of their circumgalactic medium (CGM). Our goal is to assess whether standard observational spectroscopic analysis methods accurately reproduce intrinsic column densities, metallicities [Si/H], and hydrogen densities $n_H$, in simulated absorption-line systems. Without knowledge of the intrinsic simulated properties (blind study), we analysed synthetic COS and HIRES spectra with fixed $S/N=30$ to determine the column densities, metallicity, and $n_H$, using Voigt profile fitting combined with Markov-Chain Monte-Carlo single-phase {\sc Cloudy} modelling techniques. To quantify the intrinsic simulated absorbing gas properties, we objectively determined which gas cells along a line of sight (LOS) contribute to detected absorption in the spectra and adopt the unweighted geometric mean of these gas cell properties. For this pilot study, we performed this experiment for five LOS in the Milky-Way galaxy and five LOS in the Dwarf galaxy. We found an average agreement between the "observed" and intrinsic metallicity overestimated within $0.8\sigma$ or $0.2$ dex for the "Milky-Way"' CGM and overestimated within $1.4\sigma$ or $0.2$ dex for the Dwarf galaxy CGM. We found that the spectroscopically-derived $n_H$ are underestimated within $0.8\sigma$ or $0.4$ dex of the intrinsic $n_H$ for the "Milky-Way" CGM and overestimated within $0.3\sigma$ or $0.3$ dex for the Dwarf galaxy CGM. The overall agreement suggests that, for single-phase ionisation modelling of systems where there is substantial spread in gas properties, global metallicity measurements from quasar absorption line studies are capturing the average metallicity and ionisation parameters in a given astrophysical environment.

arXiv commentSubmitted to MNRAS on August 6th, 2021. Accepted for publication on October 4th, 2021

References in corpus (51)

• The chemical composition of the Sun
• The Origin of the Mass--Metallicity Relation: Insights from 53,000 Star-Forming Galaxies in the SDSS
• How Do Galaxies Get Their Gas?
• The Average Star Formation Histories of Galaxies in Dark Matter Halos from z=0-8
• The Circumgalactic Medium
• First Results from the TNG50 Simulation: Galactic outflows driven by supernovae and black hole feedback
• Galaxies in a simulated $\Lambda$CDM Universe I: cold mode and hot cores
• Adaptive Refinement Tree - a new high-resolution N-body code for cosmological simulations
• Compaction and Quenching of High-z Galaxies in Cosmological Simulations: Blue and Red Nuggets
• Mass, Metal, and Energy Feedback in Cosmological Simulations
• The Cosmic Origins Spectrograph
• Resolving the Structure of Cold Dark Matter Halos II
• The 2013 Release of Cloudy
• Galaxy Evolution in Cosmological Simulations With Outflows I: Stellar Masses and Star Formation Rates
• MUFASA: Galaxy Formation Simulations With Meshless Hydrodynamics
• The role of stellar feedback in the formation of galaxies
• High-redshift clumpy discs and bulges in cosmological simulations
• The COS-Halos Survey: Metallicities in the Low-Redshift Circumgalactic Medium
• Characterizing the Circumgalactic Medium of Nearby Galaxies with HST/COS and HST/STIS Absorption-Line Spectroscopy
• On the Origin of the Global Schmidt Law of Star Formation
• Figuring Out Gas & Galaxies in Enzo (FOGGIE). I. Resolving Simulated Circumgalactic Absorption at 2 < z < 2.5
• Cosmological simulations of the circumgalactic medium with 1 kpc resolution: enhanced HI column densities
• The Bimodal Metallicity Distribution of the Cool Circumgalactic Medium at z<1
• Tracing Outflows and Accretion: A Bimodal Azimuthal Dependence of MgII Absorption
• Radiative feedback and the low efficiency of galaxy formation in low-mass haloes at high redshift
• The Impact of Enhanced Halo Resolution on the Simulated Circumgalactic Medium
• The Population of Weak Mg II Absorbers I. A Survey of 26 QSO HIRES/Keck Spectra
• Characterizing Circumgalactic Gas around Massive Ellipticals at z~0.4 - II. Physical Properties and Elemental Abundances
• Chemical Cartography with APOGEE: Multi-element abundance ratios
• The Nature and Origin of Low-Redshift O VI Absorbers
• Metal-enriched, sub-kiloparsec gas clumps in the circumgalactic medium of a faint z = 2.5 galaxy
• Galactic and Circumgalactic OVI and its Impact on the Cosmological Metal and Baryon Budgets at 2<z<3.5
• Low and High Ionization Absorption Properties of Mg II Absorption-Selected Galaxies at Intermediate Redshifts. II. Taxonomy, Kinematics, and Galaxies
• Predictions for the Angular Dependence of Gas Mass Flow Rate and Metallicity in the Circumgalactic Medium
• Detection of Ne VIII in the Low-Redshift Warm-Hot IGM
• SDSS IV MaNGA - An archaeological view of the Cosmic Star Formation History
• Low-mass galaxy assembly in simulations: regulation of early star formation by radiation from massive stars
• Direct Insights into Observational Absorption Line Analysis Methods of the Circumgalactic Medium Using Cosmological Simulations
• Relationship between the Metallicity of the Circumgalactic Medium and Galaxy Orientation
• The Cosmic Ultraviolet Baryon Survey (CUBS) -- III. Physical properties and elemental abundances of Lyman limit systems at $z<1$
• The COS Absorption Survey of Baryon Harbors: Unveiling the Physical Conditions of Circumgalactic Gas through Multiphase Bayesian Ionization Modeling
• Quenched Cold Accretion of a Large Scale Metal-Poor Filament due to Virial Shocking in the Halo of a Massive z=0.7 Galaxy
• The Multi-phase Absorption Systems Toward PG 1206+459
• The Minimum Halo Mass for Star Formation at z = 6 - 8
• Cloud-by-cloud, multiphase, Bayesian modeling: Application to four weak, low ionization absorbers
• Velocities of warm galactic outflows from synthetic Hα observations of star-forming galaxies
• Understanding the strong intervening OVI absorber at z${}_{abs}$ ~0.93 towards PG1206+459
• OVI Traces Photoionized Streams With Collisionally Ionized Boundaries in Cosmological Simulations of $z\sim 1$ Massive Galaxies
• Observing the circumgalactic medium of simulated galaxies through synthetic absorption spectra
• MgII Absorbers in High Resolution Quasar Spectra. I. Voigt Profile Models
• Ionization Modeling Astrophysical Gaseous Structures. I. The Optically Thin Regime

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• KODIAQ-Z: Metals and Baryons in the Cool Intergalactic and Circumgalactic Gas at 2.2<z<3.6
• A Complex Multiphase DLA Associated with a Compact Group at z=2.431 Traces Accretion, Outflows, and Tidal Streams
• Role of ionizing background on the statistics of metal absorbers in hydrodynamical simulations
• Role of ionizing background on the non-thermal broadening inferred for the aligned absorbers