2026ApJ..1000...80H

We present optical and near-infrared (NIR) spectroscopic observations of the nearby Type II supernova SN 2024ggi ranging from 250 to 581 days after the explosion. Comparing the evolution of the [O I] at 6300, 6363 Å doublet normalized to the continuum with spectral models from the literature, we estimate a progenitor star zero-age main-sequence mass (M_ZAMS) of ≈14 M_⊙. This value is consistent with M_ZAMS reported in the literature from independent methodologies. The nebular spectra are used to study the structure of the inner ejecta. The broad Hα line has a full width at half-maximum of ≃3900 km s^–1, with small deviations from a symmetric Gaussian profile centred at zero velocity that persist until the penultimate spectrum obtained 459 days after explosion, and the [O I] doublet is blueshifted by ≈-940 km s^–1. In the NIR, the nebular spectra reveal double-peaked emission features of [Mg I] and [Fe II] lines between +250 and +319 days, suggesting a bipolar distribution of intermediate-mass and iron-peak elements in the line of sight. Such a double-peaked feature in these NIR lines has not been previously reported. No corresponding asymmetries are observed in the hydrogen lines, indicating that the asymmetry is confined to intermediate-mass and iron-peak elements in the innermost ejecta. Additionally, we detect first-overtone carbon monoxide emission at 2.3 μm between 250 and 319 days and a blueshift in the emission lines of Hα, [O I], [Mg I], and [Fe II] first observed in the +581 days optical spectrum, consistent with dust formation in the ejecta.