On the Root Cause of the Host “Mass Step” in the Hubble Residuals of Type Ia Supernovae

Chul Chung, Suk Jin Yoon, Seunghyun Park, Seunghyeon An, Junhyuk Son, Hyejeon Cho, Young Wook Lee

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

It is well established that the Hubble residuals of Type Ia supernovae (SNe Ia) show the luminosity step with respect to their host galaxy stellar masses. This “mass step” is taken as an additional correction factor for the SN Ia luminosity standardization. Here we investigate the root cause of the mass step and propose that the bimodal nature of the host age distribution is responsible for the step. In particular, by using the empirical nonlinear mass-to-age relation of local galaxies, we convert the mass function of SN Ia hosts to their age distribution. We find that the age distribution shows clear bimodality: a younger (<6 Gyr) group with lower mass (∼109.5 M Sun) and an older (> 6 Gyr) group with higher mass (∼1010.5 M Sun). On the Hubble residual versus host-mass plane, the two groups create the mass step at ∼1010 M Sun. This leads us to conclude that the host galaxy mass step can be attributed to the bimodal age distribution in relation to a nonlinear relation between galaxy mass and age. We suggest that the mass step is another manifestation of the old “red sequence” and the young “blue cloud” observed in the galactic color-magnitude diagram.

Original languageEnglish
Article number94
JournalAstrophysical Journal
Volume959
Issue number2
DOIs
Publication statusPublished - 2023 Dec 1

Bibliographical note

Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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