First Cosmology Results using Type Ia Supernovae from the Dark Energy Survey: The Effect of Host Galaxy Properties on Supernova Luminosity
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First Cosmology Results using Type Ia Supernovae from the Dark Energy Survey: The Effect of Host Galaxy Properties on Supernova Luminosity

  • Author(s): Smith, M
  • Sullivan, M
  • Wiseman, P
  • Kessler, R
  • Scolnic, D
  • Brout, D
  • D'Andrea, CB
  • Davis, TM
  • Foley, RJ
  • Frohmaier, C
  • Galbany, L
  • Gupta, RR
  • Gutiérrez, CP
  • Hinton, SR
  • Kelsey, L
  • Lidman, C
  • Macaulay, E
  • Möller, A
  • Nichol, RC
  • Nugent, P
  • Palmese, A
  • Pursiainen, M
  • Sako, M
  • Thomas, RC
  • Tucker, BE
  • Carollo, D
  • Lewis, GF
  • Sommer, NE
  • Abbott, TMC
  • Aguena, M
  • Allam, S
  • Avila, S
  • Bertin, E
  • Bhargava, S
  • Brooks, D
  • Buckley-Geer, E
  • Burke, DL
  • Rosell, A Carnero
  • Kind, M Carrasco
  • Costanzi, M
  • Costa, LN da
  • Vicente, J De
  • Desai, S
  • Diehl, HT
  • Doel, P
  • Eifler, TF
  • Everett, S
  • Flaugher, B
  • Fosalba, P
  • Frieman, J
  • García-Bellido, J
  • Gaztanaga, E
  • Glazebrook, K
  • Gruen, D
  • Gruendl, RA
  • Gschwend, J
  • Gutierrez, G
  • Hartley, WG
  • Hollowood, DL
  • Honscheid, K
  • James, DJ
  • Krause, E
  • Kuehn, K
  • Kuropatkin, N
  • Lima, M
  • MacCrann, N
  • Maia, MAG
  • Marshall, JL
  • Martini, P
  • Melchior, P
  • Menanteau, F
  • Miquel, R
  • Paz-Chinchón, F
  • Plazas, AA
  • Romer, AK
  • Roodman, A
  • Rykoff, ES
  • Sanchez, E
  • Scarpine, V
  • Schubnell, M
  • Serrano, S
  • Sevilla-Noarbe, I
  • Suchyta, E
  • Swanson, MEC
  • Tarle, G
  • Thomas, D
  • Tucker, DL
  • Varga, TN
  • Walker, AR
  • Collaboration, The Dark Energy Survey
  • et al.
Abstract

We present improved photometric measurements for the host galaxies of 206 spectroscopically confirmed type Ia supernovae discovered by the Dark Energy Survey Supernova Program (DES-SN) and used in the first DES-SN cosmological analysis. Fitting spectral energy distributions to the $griz$ photometric measurements of the DES-SN host galaxies, we derive stellar masses and star-formation rates. For the DES-SN sample, when considering a 5D ($z$, $x_1$, $c$, $\alpha$, $\beta$) bias correction, we find evidence of a Hubble residual `mass step', where SNe Ia in high mass galaxies ($>10^{10} \textrm{M}_{\odot}$) are intrinsically more luminous (after correction) than their low mass counterparts by $\gamma=0.040\pm0.019$mag. This value is larger by $0.031$mag than the value found in the first DES-SN cosmological analysis. This difference is due to a combination of updated photometric measurements and improved star formation histories and is not from host-galaxy misidentification. When using a 1D (redshift-only) bias correction the inferred mass step is larger, with $\gamma=0.066\pm0.020$mag. The 1D-5D $\gamma$ difference for DES-SN is $0.026\pm0.009$mag. We show that this difference is due to a strong correlation between host galaxy stellar mass and the $x_1$ component of the 5D distance-bias correction. To better understand this effect, we include an intrinsic correlation between light-curve width and stellar mass in simulated SN Ia samples. We show that a 5D fit recovers $\gamma$ with $-9$mmag bias compared to a $+2$mmag bias for a 1D fit. This difference can explain part of the discrepancy seen in the data. Improvements in modeling correlations between galaxy properties and SN is necessary to determine the implications for $\gamma$ and ensure unbiased precision estimates of the dark energy equation-of-state as we enter the era of LSST.

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