Abstract
We present a systematic study of the diffuse ionized gas (DIG) in M83 and its effects on the measurement of metallicity gradients at varying resolution scales. Using spectrophotometric data ...cubes of M83 obtained at the 2.5m duPont telescope at Las Campanas Observatory as part of the TYPHOON programme, we separate the H ii regions from the DIG using the S ii/H α ratio, HIIphot (H ii-finding algorithm), and the H α surface brightness. We find that the contribution to the overall H α luminosity is approximately equal for the H ii and DIG regions. The data is then rebinned to simulate low-resolution observations at varying resolution scales from 41 pc up to 1005 pc. Metallicity gradients are measured using five different metallicity diagnostics at each resolution. We find that all metallicity diagnostics used are affected by the inclusion of DIG to varying degrees. We discuss the reasons why the metallicity gradients are significantly affected by DIG using the H ii dominance and emission line ratio radial profiles. We find that applying the S ii/H α cut will provide a closer estimate of the true metallicity gradient up to a resolution of 1005 pc for all metallicity diagnostics used in this study.
Conversions between gas-phase metallicities in MaNGA Scudder, Jillian M.; Ellison, Sara L.; El Meddah El Idrissi, Loubna ...
Monthly notices of the Royal Astronomical Society,
08/2021, Letnik:
507, Številka:
2
Journal Article
Recenzirano
We present polynomial conversions between each of 11 different strong line gas-phase metallicity calibrations, each based on ~1.1 million star-forming spaxels in the public Sloan Digital Sky Survey ...(SDSS) Data Release 15 (DR15) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. For this sample, which is ~20 times larger than previous works, we present fifth-order polynomial fits for each of 110 possible calibration conversions, for both Small Magellanic Cloud-type and Milky Way-type dust corrections. The typical 2σ scatter around our polynomial fits is 0.1 dex; we present the range over which the metallicities are valid. Conversions between metallicities which rely on the same set of line ratios, or a heavily shared set of emission lines, have reduced scatter in their conversions relative to those conversions with little overlap in required emission lines. Calibration conversions with less consistent sets of emission lines also have increased galaxy-to-galaxy variability, and this variability can account for up to 35 percent of the total scatter. We also compare our conversions to previous work with the single fibre SDSS DR7 spectra along with higher spatial resolution data from the TYPHOON Integral Field Spectroscopy survey, resulting in comparison samples with spatial resolutions from several kpc down to ~100 pc. Our metallicity conversions, obtained with the large sample of MaNGA, are robust against the influence of diffuse ionized gas, redshift, effective radius, and spatial blurring, and are therefore consistent across both integrated spectra and the high-resolution integral field spectroscopy data.
The spatial distribution of oxygen in the interstellar medium of galaxies is the key to understanding how efficiently metals that are synthesized in massive stars can be redistributed across a ...galaxy. We present here a case study in the nearby spiral galaxy NGC 1365 using 3D optical data obtained in the TYPHOON Program. We find systematic azimuthal variations of the H ii region oxygen abundance imprinted on a negative radial gradient. The 0.2 dex azimuthal variations occur over a wide radial range of 0.3-0.7 R25 and peak at the two spiral arms in NGC 1365. We show that the azimuthal variations can be explained by two physical processes: gas undergoes localized, sub-kiloparsec-scale self-enrichment when orbiting in the inter-arm region, and experiences efficient, kiloparsec-scale mixing-induced dilution when spiral density waves pass through. We construct a simple chemical evolution model to quantitatively test this picture and find that our toy model can reproduce the observations. This result suggests that the observed abundance variations in NGC 1365 are a snapshot of the dynamical local enrichment of oxygen modulated by spiral-driven, periodic mixing and dilution.
Conversions between gas-phase metallicities in MaNGA Scudder, Jillian M; Ellison, Sara L; El Meddah El Idrissi, Loubna ...
Monthly notices of the Royal Astronomical Society,
10/2021, Letnik:
507, Številka:
2
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
We present polynomial conversions between each of 11 different strong line gas-phase metallicity calibrations, each based on ∼1.1 million star-forming spaxels in the public Sloan Digital Sky ...Survey (SDSS) Data Release 15 (DR15) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. For this sample, which is ∼20 times larger than previous works, we present fifth-order polynomial fits for each of 110 possible calibration conversions, for both Small Magellanic Cloud-type and Milky Way-type dust corrections. The typical 2σ scatter around our polynomial fits is 0.1 dex; we present the range over which the metallicities are valid. Conversions between metallicities which rely on the same set of line ratios, or a heavily shared set of emission lines, have reduced scatter in their conversions relative to those conversions with little overlap in required emission lines. Calibration conversions with less consistent sets of emission lines also have increased galaxy-to-galaxy variability, and this variability can account for up to 35 per cent of the total scatter. We also compare our conversions to previous work with the single fibre SDSS DR7 spectra along with higher spatial resolution data from the TYPHOON Integral Field Spectroscopy survey, resulting in comparison samples with spatial resolutions from several kpc down to ∼100 pc. Our metallicity conversions, obtained with the large sample of MaNGA, are robust against the influence of diffuse ionized gas, redshift, effective radius, and spatial blurring, and are therefore consistent across both integrated spectra and the high-resolution integral field spectroscopy data.
ABSTRACT
We measure the gas-phase metallicity gradients of 248 galaxies selected from Data Release 2 of the SAMI Galaxy Survey. We demonstrate that there are large systematic discrepancies between ...the metallicity gradients derived using common strong emission line metallicity diagnostics. We determine which pairs of diagnostics have Spearman’s rank coefficients greater than 0.6 and provide linear conversions to allow the accurate comparison of metallicity gradients derived using different strong emission line diagnostics. For galaxies within the mass range 8.5 < log (M/M⊙) < 11.0, we find discrepancies of up to 0.11 dex/Re between seven popular diagnostics in the metallicity gradient–mass relation. We find a suggestion of a break in the metallicity gradient–mass relation, where the slope shifts from negative to positive, occurs between 9.5 < log (M/M⊙) < 10.5 for the seven chosen diagnostics. Applying our conversions to the metallicity gradient–mass relation, we reduce the maximum dispersion from 0.11 dex/Re to 0.02 dex/Re. These conversions provide the most accurate method of converting metallicity gradients when key emission lines are unavailable. We find that diagnostics that share common sets of emission line ratios agree best, and that diagnostics calibrated through the electron temperature provide more consistent results compared to those calibrated through photoionization models.
The gas-phase metallicity is one of the most fundamental properties of a galaxy. Measuring the gas-phase metallicity distribution allows us to gauge the age of the gas and hence how the galaxy has ...formed over time. By combining the gas-phase metallicity with galaxy evolution simulations, we can gain insight into dynamical processes which may have affected its formation process in the past. In this thesis, we use spatially resolved spectra from the SAMI galaxy survey and TYPHOON survey to explore the gas-phase metallicity of galaxies as a function of stellar mass, environment and star-formation rate. We also investigate the systematic errors and reliability of measuring gas-phase metallicity through popular strong emission line diagnostics. In the second chapter of this thesis, we present gas-phase metallicity and ionization parameter maps of 25 star-forming face-on spiral galaxies from the SAMI galaxy survey. We measure the metallicity gradients of each galaxy and find a weak mass dependence of the metallicity gradients ranging from -0.20 to -0.03 dex/Re. No significant trends were found in the ionization parameter distribution with the ionization parameter typically ranging between 7.0 < log(q) < 7.8. Ionization parameter variations of this magnitude may lead to systematic deviations of up to 0.3 dex when using the O3N2 metallicity diagnostic. It is known that metallicity gradients are significantly flattened when undergoing merger activities. This is due to the mixing of gas through tidal forces as well as inflows of pristine gas. In the third chapter, we compare the metallicity gradients of galaxies in isolated environments to those in denser environments and find no significant trends with any of the three environment density metrics tested (fifth nearest neighbour, number of galaxies within a cylinder and the average Gaussian ellipsoid density parameter). In the fourth chapter, we discuss the reliability of measuring gas-phase metallicity using strong emission line diagnostics and analyse the large systematic differences between them. Using 13 popular strong emission line diagnostics, we provide a method for converting metallicity gradients derived from different metallicity diagnostics, allowing for the comparison of metallicity gradients between different galaxy surveys and redshift ranges. In the fifth chapter, we use the highly spatially-resolved TYPHOON data of M83 to explore the consequences of determining metallicity gradients from relatively low spatially-resolved data. We find that the emission of the diffuse ionized gas (DIG) significantly flattens metallicity gradients measured using the R23 and N2O2 metallicity diagnostics, has a small flattening effect on the N2Hα and O3N2 metallicity diagnostics and significantly steepens the N2S2Hα metallicity diagnostic at the kiloparsec resolution of typical multiplexing surveys. The works within this thesis aim to inform the readers of the caveats and precautions that need to be taken when measuring the gas-phase metallicity. We hope that these articles provide an initial framework, off which improvements can be made to the way we measure and interpret the gas-phase metallicity distribution.
We present polynomial conversions between each of 11 different strong line gas-phase metallicity calibrations, each based on \(\sim\) 1.1 million star-forming spaxels in the public Sloan Digital Sky ...Survey (SDSS) Data Release 15 (DR15) Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. For this sample, which is \(\sim\) 20 times larger than previous works, we present 5th order polynomial fits for each of 110 possible calibration conversions, for both Small Magellanic Cloud (SMC)-type and Milky Way (MW)-type dust corrections. The typical \(2\sigma\) scatter around our polynomial fits is 0.1 dex; we present the range over which the metallicities are valid. Conversions between metallicities which rely on the same set of line ratios, or a heavily shared set of emission lines, have reduced scatter in their conversions relative to those conversions with little overlap in required emission lines. Calibration conversions with less consistent sets of emission lines also have increased galaxy-to-galaxy variability, and this variability can account for up to 35% of the total scatter. We also compare our conversions to previous work with the single fibre SDSS DR7 spectra along with higher spatial resolution data from the TYPHOON Integral Field Spectroscopy survey, resulting in comparison samples with spatial resolutions from several kpc down to \(\sim\)100 pc. Our metallicity conversions, obtained with the large sample of MaNGA, are robust against the influence of diffuse ionized gas, redshift, effective radius and spatial blurring, and are therefore consistent across both integrated spectra and the high resolution integral field spectroscopy data.
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