Reassessing the ZTF Volume-Limited Type Ia Supernova Sample and Its Implications for Continuous, Dust-Dependent Models of Intrinsic Scatter
Yukei S. Murakami, Daniel Scolnic
arXiv:2505.04686v1 Announce Type: new
Abstract: The ZTF DR2 includes light curves of 3628 Type Ia supernovae (SNe Ia), making it the largest low-redshift SNe Ia sample available. One central question for analyses of SNe Ia is whether the remaining diversity of standardized luminosities arises in part from an intrinsic or extrinsic effect; characterized by the color-independent bimodality in progenitor population or color- and host- dependent diversity in dust extinction, respectively. In the initial analyses of the volume-limited subset (z 3$sigma$ significance; 3. data’s preference of a model that accounts for color-dependency over a simple `step’ model at $sim$ 3$sigma$; 4. the strongest evidence to date (3.5$sigma$) that the relationship between SN color, host-galaxy properties, and luminosity is continuous rather than characterized by a discrete step. Accounting for 3 and 4 with our new model, Host2D, yields a 4.0$sigma$ improvement over the mass-step model. We trace the difference in reported findings to the fitting and analysis methods, in particular the model complexity allowed for the color-luminosity relation, rather than a difference in the sample itself.arXiv:2505.04686v1 Announce Type: new
Abstract: The ZTF DR2 includes light curves of 3628 Type Ia supernovae (SNe Ia), making it the largest low-redshift SNe Ia sample available. One central question for analyses of SNe Ia is whether the remaining diversity of standardized luminosities arises in part from an intrinsic or extrinsic effect; characterized by the color-independent bimodality in progenitor population or color- and host- dependent diversity in dust extinction, respectively. In the initial analyses of the volume-limited subset (z 3$sigma$ significance; 3. data’s preference of a model that accounts for color-dependency over a simple `step’ model at $sim$ 3$sigma$; 4. the strongest evidence to date (3.5$sigma$) that the relationship between SN color, host-galaxy properties, and luminosity is continuous rather than characterized by a discrete step. Accounting for 3 and 4 with our new model, Host2D, yields a 4.0$sigma$ improvement over the mass-step model. We trace the difference in reported findings to the fitting and analysis methods, in particular the model complexity allowed for the color-luminosity relation, rather than a difference in the sample itself.