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 project has observed ∼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 ± 0.007 dex kpc−1 and indicate a relatively small (0.043 ± 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 α-process or α-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 that increase the measured dispersion up to 0.11 dex.
| Original language | English (US) |
|---|---|
| Article number | 44 |
| Journal | Astrophysical Journal |
| Volume | 939 |
| Issue number | 1 |
| DOIs | |
| State | Published - Nov 1 2022 |
Bibliographical note
Funding Information:The MODS reduction pipeline was developed by Kevin Croxall with funding from NSF Grant AST-1108693. Details at http://www.astronomy.ohio-state.edu/MODS/Software/modsIDL/ . 9
Funding Information:
We thank the referee for a thorough review of the original manuscript and for useful feedback that has improved the clarity of this work. This work has been supported by NSF Grants AST-1109066 and AST-1714204. This paper uses data taken with the MODS built with funding from NSF grant AST-9987045 and the NSF Telescope System Instrumentation Program (TSIP), with additional funds from the Ohio Board of Regents and the Ohio State University Office of Research. This paper made use of the modsIDL spectral data reduction pipeline developed in part with funds provided by NSF Grant AST-1108693 and a generous gift from OSU Astronomy alumnus David G. Price through the Price Fellowship in Astronomical Instrumentation. This work was based in part on observations made with the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. The LBT Corporation partners are: the University of Arizona on behalf of the Arizona university system; the Istituto Nazionale di Astrofisica, Italy; the LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; the Ohio State University; and the Research Corporation, on behalf of the University of Notre Dame, the University of Minnesota, and the University of Virginia. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This study has made use of the GTC Archive; the GTC Archive is part of the Spanish Virtual Observatory project funded by MCIN/AEI/10.13039/501100011033 through grant PID2020-112949GB-I00
Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.