Year: 2026
Type: preprint
Abstract: For over two decades, Na I D ($λ\lambda5891.58, 5897.56$ Å) absorption has been the primary optical tracer of cool, neutral gas in galaxies. In contrast, Ca II H&K ($λλ$3934.78, 3969.59 Å), which traces both neutral and ionized gas, has been comparatively unexplored. Here, we present a comparative study of the Na I D and Ca II H&K interstellar absorption lines using spatially resolved MaNGA IFU spectroscopy of 140 red geyser galaxies (local quiescent systems hosting low-luminosity AGN with bisymmetric ionized outflows) and a control sample of 140 quiescent galaxies. Using Gaussian fits to the Na I D and Ca II K lines, we measure gas velocity and dispersion. We find that the Ca II reservoirs are up to ~ 6 times larger in area, twice as radially extended, and have ~ 1.7 - 1.8x broader line widths than Na I D. Furthermore, Na I D shows a direct dependence on dust reservoir size, but the correlation vanishes for Ca II. In only ~ 20% of galaxies do the Na I D detections extend beyond dust regions, but this fraction jumps to ~70% for Ca II. Using these findings, we argue that dust plays a significant role in shielding Na I D from ionizing radiation, whereas Ca II, with its higher ionization potential, is not as dependent on shielding and can more easily survive beyond regions of dust. Na I D and Ca II trace distinct gas components, and studying both together provides a more complete picture of gas flows in galaxies.
Source: arXiv (Cornell University)
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, Yale University, Vanderbilt University, University of Pennsylvania, Ohio State University, California Institute of Technology, University of Chicago, University of Washington, Johns Hopkins University, University of Notre Dame, University of Portsmouth, New Mexico State University, York University, University College London, University of Oxford, University of Sussex, Deutsche Forschungsgemeinschaft, Chinese Academy of Sciences, Ministério da Ciência, Tecnologia e Inovação, Financiadora de Estudos e Projetos, Universidad Nacional Autónoma de México, Max-Planck-Institut für Astrophysik, Max-Planck-Institut für Astronomie, University of Illinois at Urbana-Champaign, Office of Science, Jet Propulsion Laboratory, University of Colorado Boulder, Science and Technology Facilities Council, Leibniz-Gemeinschaft, High Energy Physics, Integrated Electronics Engineering Center, Binghamton University, Argonne National Laboratory, Fermilab, Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory
Awards: G1800429324, G988696487
OpenAlex ID: W7214007673