Investigating the Origin of Observed Central Dips in Radial Metallicity Profiles

Abstract

Radial metallicity trends provide a key indicator of physical processes such as star formation and radial gas migration within a galaxy. Large IFU surveys allow for detailed studies of these radial variations, with recent observations detecting central dips in the metallicity, which may trace the impact of various evolutionary processes. However, the origin of these dips has not been conclusively determined, with suggestions that they may be diagnostic dependent. In this paper, we use the SDSS-IV MaNGA survey to investigate whether the observed dips represent genuine decreases in the central metallicity, or if they could be an artefact of the diagnostic used. Using a sub-sample of 758 local star-forming galaxies at low inclinations, we investigate in detail the impact of using different strong line diagnostics on the shapes of the returned profiles, and the prevalence of dips. We find no clear evidence of the dips being caused by changing values of the ionisation parameter within galaxies. To investigate physical causes, we explore both global and spatially-resolved parameters, finding that galaxies exhibiting central dips in the O3N2 metallicity profile have on average lower H$\alpha$EW values out to $R/R_\rm{e} \sim 1.5$, and higher values of D${}_N$(4000) in the central regions. We additionally find a higher prevalence of dips in galaxies with high stellar mass, and lower values of global specific star formation rate, suggesting a possible link to central quenching. Nevertheless, these results are dependent on the diagnostic used, suggesting caution should be taken when interpreting observed features in galaxy metallicity gradients.

Accepted for publication in MNRAS. 23 pages; 21 figures

References in corpus (35)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• The Host Galaxies and Classification of Active Galactic Nuclei
• Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache Point Observatory
• The MUSE second-generation VLT instrument
• PyNeb: a new tool for analyzing emission lines. I. Code description and validation of results
• Understanding Galaxy Evolution through Emission Lines
• The MaNGA Integral Field Unit Fiber Feed System for the Sloan 2.5 m Telescope
• The Data Reduction Pipeline for the SDSS-IV MaNGA IFU Galaxy Survey
• The SDSS-IV MaNGA Sample: Design, Optimization, and Usage Considerations
• SDSS-IV MaNGA IFS Galaxy Survey --- Survey Design, Execution, and Initial Data Quality
• New fully empirical calibrations of strong-line metallicity indicators in star forming galaxies
• SDSS-IV MaNGA: The Impact of Diffuse Ionized Gas on Emission-line Ratios, Interpretation of Diagnostic Diagrams, and Gas Metallicity Measurements
• Metallicity gradients in local field star-forming galaxies: Insights on inflows, outflows, and the coevolution of gas, stars and metals
• Star formation is boosted (and quenched) from the inside out: radial star formation profiles from MaNGA
• Diffuse ionized gas in galaxies across the Hubble sequence at the CALIFA resolution
• The Oxygen Abundances of Luminous and Ultraluminous Infrared Galaxies
• L-GALAXIES 2020: Spatially resolved cold gas phases, star formation and chemical enrichment in galactic discs
• The MUSE Atlas of Disks (MAD): Resolving Star Formation Rates and Gas Metallicities on < 100pc Scales
• P-MaNGA: Emission Lines Properties - Gas Ionisation and Chemical Abundances from Prototype Observations
• Biases in metallicity measurements from global galaxy spectra: the effects of flux-weighting and diffuse ionized gas contamination
• The Effects of Diffuse Ionized Gas and Spatial Resolution on Metallicity Gradients: TYPHOON Two-Dimensional Spectrophotometry of M83
• The radial abundance gradient of oxygen towards the Galactic anticentre
• The chemical evolution of local star forming galaxies: Radial profiles of ISM metallicity, gas mass, and stellar mass and constraints on galactic accretion and winds
• L-GALAXIES 2020: The evolution of radial metallicity profiles and global metallicities in disc galaxies
• Metallicity gradients in small and nearby spiral galaxies
• Incidence, scaling relations and physical conditions of ionised gas outflows in MaNGA
• Carbon, nitrogen and oxygen abundance gradients in M101 and M31
• SDSS-IV MaNGA: Variations in the N/O -- O/H relation bias metallicity gradient measurements
• GASP and MaNGA surveys shed light on the enigma of the gas metallicity gradients in disk galaxies
• Bar effect on gas-phase abundance gradients. II. Luminosity-dependent flattening
• Quantifying the effects of spatial resolution and noise on galaxy metallicity gradients
• A re-assessment of strong line metallicity conversions in the machine learning era
• Resolving the stellar components of the massive multiple system Herschel 36 with AMBER/VLTI
• Inside-out growth or inside-out quenching? clues from colour gradients of local galaxies
• The importance of the diffuse ionized gas for interpreting galaxy spectra

Cited by in corpus (3)

• Calibration-based abundances in the interstellar gas of galaxies from slit and IFU spectra
• Narrow absorption lines from intervening material in supernovae. II. Galaxy properties
• The ALPINE-CRISTAL-JWST Survey: Gas-phase abundance gradients of main sequence star-forming galaxies and their kinematics at $4<z<6$