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2025

1. Dixon, M., Mould, J., Lidman, C., Taylor, E., Flynn, C., Duffy, A., Galbany, L., Scolnic, D., Davis, T., Moller, A., Kelsey, L., Lee, J., Wiseman, P., Vincenzi, M., Shah, P., Aguena, M., Allam, S., Alves, O., Bacon, D., Bocquet, S., Brooks, D., Burke, D., Rosell, A., Carollo, D., Carretero, J., Conselice, C., da Costa, L., Pereira, M., Diehl, H., Doel, P., Everett, S., Ferrero, I., Flaugher, B., Frieman, J., Garcia-Bellido, J., Gatti, M., Gaztanaga, E., Giannini, G., Gruen, D., Gruendl, R., Gutierrez, G., Herner, K., Hinton, S., Hollowood, D., Honscheid, K., James, D., Kuehn, K., Lima, M., Marshall, J., Mena-Fernandez, J., Menanteau, F., Miquel, R., Myles, J., Nichol, R., Ogando, R., Palmese, A., Pieres, A., Malagon, A., Samuroff, S., Sanchez, E., Sanchez Cid, D., Sevilla-Noarbe, I., Smith, M., Sobreira, F., Suchyta, E., Swanson, M., Tarle, G., To, C., Tucker, B., Tucker, D., Vikram, V., Walker, A., Weaverdyck, N., 2025, MNRAS, 538, 782, Calibrating the absolute magnitude of type Ia supernovae in nearby galaxies using [O II] and implications for H₀
   Abstract

   The present state of cosmology is facing a crisis where there is a fundamental disagreement in measurements of the Hubble constant ($H_{0}$), with significant tension between the early and late Universe methods. Type Ia supernovae (SNe Ia) are important to measuring $H_{0}$ through the astronomical distance ladder. However, there remains potential to better standardize SN Ia light curves by using known dependencies on host galaxy properties after the standard light curve width and colour corrections have been applied to the peak SN Ia luminosities. To explore this, we use the 5-yr photometrically identified SNe Ia sample obtained by the Dark Energy Survey, along with host galaxy spectra obtained by the Australian Dark Energy Survey. Using host galaxy spectroscopy, we find a significant trend with the equivalent width (EW) of the [O II] $\lambda \lambda$ 3727, 29 doublet, a proxy for specific star formation rate, and Hubble residuals. We find that the correlation with [O II] EW is a powerful alternative to the commonly used mass step after initial light-curve corrections. Applying this [O II] EW correction to 20 SNe Ia in calibrator galaxies observed with WiFeS, we examined the impact on SN Ia absolute magnitudes and $H_{0}$. Our [O II] EW corrections result in $H_{0}$ values ranging between 73.04 and 73.51 $\mathrm{km \, s^{-1} \, Mpc^{-1}}$, with a combined statistical and systematic uncertainty of $\sim 1.31 \, \mathrm{km \, s^{-1} \, Mpc^{-1}}$. However, even with this additional correction, the impact of host galaxy properties in standardizing SNe Ia appears limited in reducing the current tension ($\sim 5\sigma$) with the cosmic microwave background result for $H_{0}$.

2. Golden-Marx, J., Zhang, Y., Ogando, R., Yanny, B., da Silva Pereira, M., Hilton, M., Aguena, M., Allam, S., Andrade-Oliveira, F., Bacon, D., Brooks, D., Carnero Rosell, A., Carretero, J., Cheng, T., da Costa, L., De Vicente, J., Desai, S., Doel, P., Everett, S., Ferrero, I., Frieman, J., Garcia-Bellido, J., Gatti, M., Giannini, G., Gruen, D., Gruendl, R., Gutierrez, G., Hinton, S., Hollowood, D., Honscheid, K., James, D., Kuehn, K., Lee, S., Mena-Fernandez, J., Menanteau, F., Miquel, R., Mohr, J., Palmese, A., Pieres, A., Plazas Malagon, A., Samuroff, S., Sanchez, E., Schubnell, M., Sevilla-Noarbe, I., Smith, M., Suchyta, E., Tarle, G., Vikram, V., Walker, A., Weaverdyck, N., Wiseman, P., 2025, MNRAS, 538, 622, The hierarchical growth of bright central galaxies and intracluster light as traced by the magnitude gap
   Abstract

   Using a sample of 2800 galaxy clusters identified in the Dark Energy Survey across the redshift range $0.20 \lt z \lt 0.60$, we characterize the hierarchical assembly of bright central galaxies (BCGs) and the surrounding intracluster light (ICL). To quantify hierarchical formation we use the stellar mass-halo mass (SMHM) relation, comparing the halo mass, estimated via the mass-richness relation, to the stellar mass within the BCG + ICL system. Moreover, we incorporate the magnitude gap (M14), the difference in brightness between the BCG (measured within 30 kpc) and fourth brightest cluster member galaxy within 0.5 $R_{200,c}$, as a third parameter in this linear relation. The inclusion of M14, which traces BCG hierarchical growth, increases the slope and decreases the intrinsic scatter, highlighting that it is a latent variable within the BCG + ICL SMHM relation. Moreover, the correlation with M14 decreases at large radii. However, the stellar light within the BCG + ICL transition region (30 -80 kpc) most strongly correlates with halo mass and has a statistically significant correlation with M14. Since the transition region and M14 are independent measurements, the transition region may grow due to the BCG's hierarchical formation. Additionally, as M14 and ICL result from hierarchical growth, we use a stacked sample and find that clusters with large M14 values are characterized by larger ICL and BCG + ICL fractions, which illustrates that the merger processes that build the BCG stellar mass also grow the ICL. Furthermore, this may suggest that M14 combined with the ICL fraction can identify dynamically relaxed clusters.

2 publications and 8 citations in 2025.

2 publications and 8 citations total.