Unveiling the correlation between the UV 2175 Å dust attenuation bump, PAH emission, and gas-phase metallicity at cosmic noon
The UV 2175 Å attenuation bump is one of the most prominent yet poorly understood features of galaxy attenuation curves. Its main candidate carrier is polycyclic aromatic hydrocarbon (PAH) molecules, which are more prevalent in high-metallicity environments. We present the first systematic study of the relationship between PAH abundance and the UV bump in 49 galaxies at cosmic noon (1.5 < z < 2.7), examining its dependence on stellar mass, star formation rate (SFR), and V-band optical depth. For 19 galaxies, we also investigate gas-phase metallicity using oxygen abundances. We measure the bump amplitude from VLT/MUSE spectroscopy and derive galaxy properties, including the PAH-to-dust mass fraction $q_{\rm PAH}$, through spectral energy distribution fitting with Prospector, combining JWST/NIRCam and JWST/MIRI photometry. Oxygen abundances are derived from strong-line diagnostics using Keck/MOSFIRE and JWST/NIRSpec data. We find a positive correlation between bump amplitude $E_{\rm bump}$ and $q_{\rm PAH}$ (Spearman $ρ= 0.60$). UV bumps are rarely detected at low $q_{\rm PAH}$, supporting PAHs as their primary carriers. Both $E_{\rm bump}$ and $q_{\rm PAH}$ correlate with stellar mass, oxygen abundance, and optical depth, and anticorrelate with specific SFR, suggesting that PAHs and the UV bump are suppressed in low-metallicity, dust-poor, and/or intensely star-forming environments. This is consistent with PAH destruction in environments with limited dust shielding and/or strong radiation fields. A principal component analysis of $E_{\rm bump}$, $q_{\rm PAH}$, optical depth, specific SFR, and oxygen abundance explains 97% of the variance, suggesting that previously reported correlations with stellar mass reflect an underlying dependence on metallicity. Finally, variations in dust geometry may explain the wide range of bump amplitudes (0-0.5 mag) at high $q_{\rm PAH}$.