arXiv subjects

Ziming Peng

Publications and source records attributed to Ziming Peng.

3 recordsLinked to original sources

arXiv2026

Re-evaluating the resolved mass-metallicity relation with a self-consistent metallicity calibration

Aims. The mass-metallicity relation (MZR) is essential for understanding the chemical evolution of galaxies. Whether the star formation rate (SFR) plays a role in setting the metallicity has long been debated. Using various metallicity calibrations can result in different conclusions for this fundamental yet unresolved issue. Methods. We apply a self-consistent metallicity calibration based on photoionization models to re-evaluate the resolved and integrated MZR. We utilize the integral field unit data from SDSS-IV/MaNGA, with $\sim 3.5\times10^6$ spaxels and $\sim$ 4550 galaxies. We compare our preferred metallicity calibration with several strong-line calibrations in the literature and direct method metallicity. We analyze the metallicity residual of MZR to evaluate the effects of SFR and apply the partial correlation coefficient to quantify the effects. Results. The metallicity calibration we used shows the best consistency with the direct method. We provide 3 equations for resolved MZR, and verify that local SFR does not show significant correlation with metallicity. Considering the integrated properties, (s)SFR do not present correlation with the metallicity residuals. The results suggest that an equilibrium of inflow and outflow is favored, and the mass-metallicity relation does not have a secondary dependence on SFR.

astro-ph.GA↗

arXiv2026

Surprising increase of electron temperature in metal-rich star-forming region

The electron temperature is a crucial parameter for the determination of the gas-phase metallicity of galaxies. Low electron temperature is expected for metal-rich galaxies, theoretically. We report the discovery that temperature, as measured through auroral-to-strong line ratios of O$^+$, trends in reverse directions at 12+log(O/H) $\geq$ 8.7. This trend remains consistent regardless of the emission line fitting method employed and is not attributable to contamination or dust attenuation correction. Notably, this phenomenon is not observed in other low-ionization ions, such as S$^+$ and N$^+$, which also probe electron temperature. The results are verified in two independent datasets. We analyze the potential cause for the high [OII] auroral-to-strong line ratios at high metallicities, finding that no specific reason could account for that. This finding challenges the fundamental principles of the direct $T_e$ method for metallicity measurement, warranting further investigation into its physical interpretation.

astro-ph.GA↗

arXiv2025

SDSS-IV MaNGA: Data-Model Discrepancy in Temperature-sensitive Line Ratios for Star-forming Galaxies

Gas-phase metallicity is a fundamental parameter that helps constrain the star-forming history and chemical evolution of a galaxy. Measuring electron temperature through auroral-to-strong line ratios is a direct approach to deriving metallicity. However, there is a longstanding discrepancy between metallicity measured through the direct method and that based on the photoionization models. This paper aims to verify and understand the discrepancies. We bin ~ 1.5 million spaxels from SDSS-IV MaNGA according to metallicity and ionization parameters derived from theoretical strong-line calibrations. We stack the spectra of spaxels within each bin and measure the flux of strong lines and faint auroral lines. Auroral lines for [OII], [SII], [OIII], and [SIII] are detected in the stacked spectra of most bins, and the [NII] auroral line is detected in fewer bins. We apply an empirical method to correct dust attenuation, which makes more realistic corrections for low ionization lines. We derive electron temperatures for these five ionic species and measure the oxygen and sulfur abundances using the direct method. We present the resulting abundance measurements and compare them with those model-calibrated strong-line abundances. The chemical abundances measured with the direct method are lower than those derived from the photoionization model, with a median of 0.09 dex. This discrepancy is smaller compared to the results based on other metallicity calibrations previously reported. However, we notice that the direct method could not account for the variation in ionization parameters, indicating that the precise calibration of metallicity using the direct method has yet to be fully realized. We report significant discrepancies between data and the photoionization model, which illustrates that the one-dimensional photoionization model is incapable of representing the complexity of real situations.

astro-ph.GA↗