CHAOS VII: A Large-Scale Direct Abundance Study in M33

Abstract

The dispersion in chemical abundances provides a very strong constraint on the processes that drive the chemical enrichment of galaxies. Due to its proximity, the spiral galaxy M33 has been the focus of numerous chemical abundance surveys to study the chemical enrichment and dispersion in abundances over large spatial scales. The CHemical Abundances Of Spirals (CHAOS) project has observed $\sim$100 H II regions in M33 with the Large Binocular Telescope (LBT), producing the largest homogeneous sample of electron temperatures (T${}_e$) and direct abundances in this galaxy. Our LBT observations produce a robust oxygen abundance gradient of $-$0.037 $\pm$ 0.007 dex/kpc and indicate a relatively small (0.043 $\pm$ 0.015 dex) intrinsic dispersion in oxygen abundance relative to this gradient. The dispersions in N/H and N/O are similarly small and the abundances of Ne, S, Cl, and Ar relative to O are consistent with the solar ratio as expected for $\alpha$-process or $\alpha$-process-dependent elements. Taken together, the ISM in M33 is chemically well-mixed and homogeneously enriched from inside-out with no evidence of significant abundance variations at a given radius in the galaxy. Our results are compared to those of the numerous studies in the literature, and we discuss possible contaminating sources that can inflate abundance dispersion measurements. Importantly, if abundances are derived from a single T${}_e$ measurement and T${}_e$-T${}_e$ relationships are relied on for inferring the temperature in the unmeasured ionization zone, this can lead to systematic biases which increase the measured dispersion up to 0.11 dex.

52 pages, 13 figures, accepted for publication in The Astrophysical Journal

References in corpus (26)

• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• PyNeb: a new tool for analyzing emission lines. I. Code description and validation of results
• A Survey of Local Group Galaxies Currently Forming Stars. I. UBVRI Photometry of Stars in M31 and M33
• New fully empirical calibrations of strong-line metallicity indicators in star forming galaxies
• A z=0 Multi-wavelength Galaxy Synthesis I: A WISE and GALEX Atlas of Local Galaxies
• Techniques and Review of Absolute Flux Calibration from the Ultraviolet to the Mid-Infrared
• Keck HIRES Spectroscopy of Extragalactic HII Regions: C and O Abundances from Recombination Lines
• CHAOS I: Direct Chemical Abundances for HII Regions in NGC 628
• On the abundance discrepancy problem in HII regions
• A Survey of Local Group Galaxies Currently Forming Stars: III. A Search for Luminous Blue Variables and Other H-alpha Emission-Lined Stars
• The M33 Metallicity Project: Resolving the Abundance Gradient Discrepancies in M33
• The metallicity gradient of M 33: chemical abundances of HII regions
• The Tully-Fisher relation for S0 galaxies
• The Galactic radial abundance gradients of C, N, O, Ne, S, Cl and Ar from deep spectra of H II regions
• Dynamical signatures of a LCDM-halo and the distribution of the baryons in M33
• Gradients of chemical abundances in the Milky Way from HII regions: distances derived from Gaia EDR3 parallaxes and temperature inhomogeneities
• Luminous and Variable Stars in M31 and M33. II. Luminous Blue Variables, Candidate LBVs, Fe II Emission Line Stars, and Other Supergiants
• Ionization correction factors and dust depletion patterns in giant HII regions
• On the Determination of N and O Abundances in Low Metallicity Systems
• On the radial abundance gradients of nitrogen and oxygen in the inner Galactic disc
• Carbon, nitrogen and oxygen abundance gradients in M101 and M31
• The Te[N II]-Te[O III] temperature relation in H II regions and the reliability of strong-line methods
• Toward an internally consistent astronomical distance scale
• Photoionized Herbig-Haro objects in the Orion Nebula through deep high-spectral resolution spectroscopy III: HH514
• CHAOS V: Recombination Line Carbon Abundances in M101
• Spectroscopic Study of M33 with LAMOST survey. I. Chemical gradients from nebulae

Cited by in corpus (1)

• A First Look at the Abundance Pattern -- O/H, C/O, and Ne/O -- in $z>7$ Galaxies with JWST/NIRSpec