Cepheid Metallicity in the Leavitt Law (C-MetaLL) survey: IX. Metallicity dependence of Period-Wesenheit relations based on a homogeneous spectroscopic sample
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| Main Authors: | , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| author | Ripepi, V. Trentin, E. Catanzaro, G. Marconi, M. Bhardwaj, A. Clementini, G. Cusano, F. De Somma, G. Molinaro, R. Sicignano, T. Storm, J. |
| author_facet | Ripepi, V. Trentin, E. Catanzaro, G. Marconi, M. Bhardwaj, A. Clementini, G. Cusano, F. De Somma, G. Molinaro, R. Sicignano, T. Storm, J. |
| contents | The C-MetaLL project has provided homogeneous spectroscopic abundances of 290 Classical Cepheids (DCEPs) for which we have the intensity-averaged magnitudes in multiple optical and near-infrared (NIR) bands, periods, pulsation modes, and Gaia parallaxes. Our goal is to derive updated period-Wesenheit-metallicity (PWZ) relations using the largest and most homogeneous metallicity sample ever used for such analyses, covering a range of $-1.3<$[Fe/H]$<+0.3$ dex. We computed several optical and NIR Wesenheit magnitudes using 275 DCEPs with reliable parallaxes, by applying a robust photometric parallax technique, which simultaneously fits all parameters -- including the global Gaia parallax counter-correction -- and handles outliers without data rejection. We find a stronger metallicity dependence ($γ\approx -0.5$ mag/dex in optical, $-0.4$ mag/dex in NIR) than recent literature reports. Gaia parallax zero-point conter-corrections ($ε$) vary smoothly across bands, with an average value of $\sim$10 $μ$as, aligning with previous determinations. Applying our PWZ relations to LMC Cepheids yields distances generally consistent within $1σ$ with geometric estimates. The choice of reddening law has a negligible impact, while using only fundamental-mode pulsators significantly increases the uncertainties. Including $α$-element corrections increases $|γ|$ and reduces $ε$. However, we find statistically consistent $γ$ values with the literature, particularly for the key Wesenheit magnitude in the HST bands, by restricting the sample to the brighter (i.e. closer) objects, or by including only pulsators with $-0.7<$[Fe/H]$<$0.2 dex. Our results hint at a large $γ$ or a non-linear dependence on metallicity of DCEP luminosities at the metal-poor end, which is difficult to quantify with the precision of parallaxes of the present dataset. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2508_17447 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Cepheid Metallicity in the Leavitt Law (C-MetaLL) survey: IX. Metallicity dependence of Period-Wesenheit relations based on a homogeneous spectroscopic sample Ripepi, V. Trentin, E. Catanzaro, G. Marconi, M. Bhardwaj, A. Clementini, G. Cusano, F. De Somma, G. Molinaro, R. Sicignano, T. Storm, J. Solar and Stellar Astrophysics Astrophysics of Galaxies The C-MetaLL project has provided homogeneous spectroscopic abundances of 290 Classical Cepheids (DCEPs) for which we have the intensity-averaged magnitudes in multiple optical and near-infrared (NIR) bands, periods, pulsation modes, and Gaia parallaxes. Our goal is to derive updated period-Wesenheit-metallicity (PWZ) relations using the largest and most homogeneous metallicity sample ever used for such analyses, covering a range of $-1.3<$[Fe/H]$<+0.3$ dex. We computed several optical and NIR Wesenheit magnitudes using 275 DCEPs with reliable parallaxes, by applying a robust photometric parallax technique, which simultaneously fits all parameters -- including the global Gaia parallax counter-correction -- and handles outliers without data rejection. We find a stronger metallicity dependence ($γ\approx -0.5$ mag/dex in optical, $-0.4$ mag/dex in NIR) than recent literature reports. Gaia parallax zero-point conter-corrections ($ε$) vary smoothly across bands, with an average value of $\sim$10 $μ$as, aligning with previous determinations. Applying our PWZ relations to LMC Cepheids yields distances generally consistent within $1σ$ with geometric estimates. The choice of reddening law has a negligible impact, while using only fundamental-mode pulsators significantly increases the uncertainties. Including $α$-element corrections increases $|γ|$ and reduces $ε$. However, we find statistically consistent $γ$ values with the literature, particularly for the key Wesenheit magnitude in the HST bands, by restricting the sample to the brighter (i.e. closer) objects, or by including only pulsators with $-0.7<$[Fe/H]$<$0.2 dex. Our results hint at a large $γ$ or a non-linear dependence on metallicity of DCEP luminosities at the metal-poor end, which is difficult to quantify with the precision of parallaxes of the present dataset. |
| title | Cepheid Metallicity in the Leavitt Law (C-MetaLL) survey: IX. Metallicity dependence of Period-Wesenheit relations based on a homogeneous spectroscopic sample |
| topic | Solar and Stellar Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2508.17447 |