Browsing by Author "Brout, D"

Now showing 1 - 11 of 11
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    Binning is Sinning (Supernova Version): The Impact of Self-Calibration in Cosmological Analyses with Type Ia Supernovae
    Brout, D; Hinton, SR; Scolnic, D
    Recent cosmological analyses (e.g., JLA, Pantheon) of Type Ia Supernova (SNIa) have propagated systematic uncertainties into a covariance matrix and either binned or smoothed the systematic vectors in redshift space. We demonstrate that systematic error budgets of these analyses can be improved by a factor of $\sim1.5\times$ with the use of unbinned and unsmoothed covariance matrices. To understand this, we employ a separate approach that simultaneously fits for cosmological parameters and additional self-calibrating scale parameters that constrain the size of each systematic. We show that the covariance-matrix approach and scale-parameter approach yield equivalent results, implying that in both cases the data can self-calibrate certain systematic uncertainties, but that this ability is hindered when information is binned or smoothed in redshift space. We review the top systematic uncertainties in current analyses and find that the reduction of systematic uncertainties in the unbinned case depends on whether a systematic is consistent with varying the cosmological model and whether or not the systematic can be described by additional correlations between SN properties and luminosity. Furthermore, we show that the power of self-calibration increases with the size of the dataset, which presents a tremendous opportunity for upcoming analyses of photometrically classified samples, like those of Legacy Survey of Space and Time (LSST) and the Nancy Grace Roman Telescope (NGRST). However, to take advantage of self-calibration in large, photometrically-classified samples, we must first address the issue that binning is required in currently-used photometric methodologies.
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    Cosmological model insensitivity of local $H_0$ from the Cepheid distance ladder
    Dhawan, S; Brout, D; Scolnic, D; Goobar, A; Riess, AG; Miranda, V
    The observed tension ($\sim 9\%$ difference) between the local distance ladder measurement of the Hubble constant, $H_0$, and its value inferred from the cosmic microwave background (CMB) could hint at new, exotic, cosmological physics. We test the impact of the assumption about the expansion history of the universe ($0.01
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    Dark Energy Survey Year 1 Results: Cosmological Constraints from Cluster Abundances and Weak Lensing
    Abbott, TMC; Aguena, M; Alarcon, A; Allam, S; Allen, S; Annis, J; Avila, S; Bacon, D; Bechtol, K; Bermeo, A; Bernstein, GM; Bertin, E; Bhargava, S; Bocquet, S; Brooks, D; Brout, D; Buckley-Geer, E; Burke, DL; Carnero Rosell, A; Carrasco Kind, M; Carretero, J; Castander, FJ; Cawthon, R; Chang, C; Chen, X; Choi, A; Costanzi, M; Crocce, M; da Costa, LN; Davis, TM; De Vicente, J; DeRose, J; Desai, S; Diehl, HT; Dietrich, JP; Dodelson, S; Doel, P; Drlica-Wagner, A; Eckert, K; Eifler, TF; Elvin-Poole, J; Estrada, J; Everett, S; Evrard, AE; Farahi, A; Ferrero, I; Flaugher, B; Fosalba, P; Frieman, J; García-Bellido, J; Gatti, M; Gaztanaga, E; Gerdes, DW; Giannantonio, T; Giles, P; Grandis, S; Gruen, D; Gruendl, RA; Gschwend, J; Gutierrez, G; Hartley, WG; Hinton, SR; Hollowood, DL; Honscheid, K; Hoyle, B; Huterer, D; James, DJ; Jarvis, M; Jeltema, T; Johnson, MWG; Johnson, MD; Kent, S; Krause, E; Kron, R; Kuehn, K; Kuropatkin, N; Lahav, O; Li, TS; Lidman, C; Lima, M; Lin, H; MacCrann, N; Maia, MAG; Mantz, A; Marshall, JL; Martini, P; Mayers, J; Melchior, P; Mena-Fernández, J; Menanteau, F; Miquel, R; Mohr, JJ; Nichol, RC; Nord, B; Ogando, RLC; Palmese, A; Paz-Chinchón, F; Plazas, AA; Prat, J; Rau, MM; Romer, AK; Roodman, A; Rooney, P; Rozo, E; Rykoff, ES; Sako, M; Samuroff, S; Sánchez, C; Sanchez, E; Saro, A; Scarpine, V; Schubnell, M; Scolnic, D; Serrano, S; Sevilla-Noarbe, I; Sheldon, E; Smith, J Allyn; Smith, M; Suchyta, E; Swanson, MEC; Tarle, G; Thomas, D; To, C; Troxel, MA; Tucker, DL; Varga, TN; von der Linden, A; Walker, AR; Wechsler, RH; Weller, J; Wilkinson, RD; Wu, H; Yanny, B; Zhang, Y; Zhang, Z; Zuntz, J; Collaboration, DES
    We perform a joint analysis of the counts and weak lensing signal of redMaPPer clusters selected from the Dark Energy Survey (DES) Year 1 dataset. Our analysis uses the same shear and source photometric redshifts estimates as were used in the DES combined probes analysis. Our analysis results in surprisingly low values for $S_8 =\sigma_8(\Omega_{\rm m}/0.3)^{0.5}= 0.65\pm 0.04$, driven by a low matter density parameter, $\Omega_{\rm m}=0.179^{+0.031}_{-0.038}$, with $\sigma_8-\Omega_{\rm m}$ posteriors in $2.4\sigma$ tension with the DES Y1 3x2pt results, and in $5.6\sigma$ with the Planck CMB analysis. These results include the impact of post-unblinding changes to the analysis, which did not improve the level of consistency with other data sets compared to the results obtained at the unblinding. The fact that multiple cosmological probes (supernovae, baryon acoustic oscillations, cosmic shear, galaxy clustering and CMB anisotropies), and other galaxy cluster analyses all favor significantly higher matter densities suggests the presence of systematic errors in the data or an incomplete modeling of the relevant physics. Cross checks with X-ray and microwave data, as well as independent constraints on the observable--mass relation from SZ selected clusters, suggest that the discrepancy resides in our modeling of the weak lensing signal rather than the cluster abundance. Repeating our analysis using a higher richness threshold ($\lambda \ge 30$) significantly reduces the tension with other probes, and points to one or more richness-dependent effects not captured by our model.
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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
    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; Swann, E; Thomas, RC; Tucker, BE; Vincenzi, M; 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, AC; Kind, MC; Costanzi, M; da Costa, LN; de Vicente, J; 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
    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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    Optical follow-up of gravitational wave triggers with DECam during the first two LIGO/VIRGO observing runs
    Herner, K; Annis, J; Brout, D; Soares-Santos, M; Kessler, R; Sako, M; Butler, R; Doctor, Z; Palmese, A; Allam, S; Tucker, DL; Sobreira, F; Yanny, B; Diehl, HT; Frieman, J; Glaeser, N; Garcia, A; Sherman, NF; Bechtol, K; Berger, E; Chen, HY; Conselice, CJ; Cook, E; Cowperthwaite, PS; Davis, TM; Drlica-Wagner, A; Farr, B; Finley, D; Foley, RJ; Garcia-Bellido, J; Gill, MSS; Gruendl, RA; Holz, DE; Kuropatkin, N; Lin, H; Marriner, J; Marshall, JL; Matheson, T; Neilsen, E; Paz-Chinchón, F; Sauseda, M; Scolnic, D; Williams, PKG; Avila, S; Bertin, E; Buckley-Geer, E; Burke, DL; Rosell, AC; Carrasco-Kind, M; Carretero, J; da Costa, LN; De Vicente, J; Desai, S; Doel, P; Eifler, TF; Everett, S; Fosalba, P; Gaztanaga, E; Gerdes, DW; Gschwend, J; Gutierrez, G; Hartley, WG; Hollowood, DL; Honscheid, K; James, DJ; Krause, E; Kuehn, K; Lahav, O; Li, TS; Lima, M; Maia, MAG; March, M; Menanteau, F; Miquel, R; Plazas, AA; Sanchez, E; Scarpine, V; Schubnell, M; Serrano, S; Sevilla-Noarbe, I; Smith, M; Suchyta, E; Tarle, G; Wester, W; Zhang, Y
    Gravitational wave (GW) events detectable by LIGO and Virgo have several possible progenitors, including black hole mergers, neutron star mergers, black hole--neutron star mergers, supernovae, and cosmic string cusps. A subset of GW events are expected to produce electromagnetic (EM) emission that, once detected, will provide complementary information about their astrophysical context. To that end, the LIGO--Virgo Collaboration (LVC) sends GW candidate alerts to the astronomical community so that searches for their EM counterparts can be pursued. The DESGW group, consisting of members of the Dark Energy Survey (DES), the LVC, and other members of the astronomical community, uses the Dark Energy Camera (DECam) to perform a search and discovery program for optical signatures of LVC GW events. DESGW aims to use a sample of GW events as standard sirens for cosmology. Due to the short decay timescale of the expected EM counterparts and the need to quickly eliminate survey areas with no counterpart candidates, it is critical to complete the initial analysis of each night's images as quickly as possible. We discuss our search area determination, imaging pipeline, and candidate selection processes. We review results from the DESGW program during the first two LIGO--Virgo observing campaigns and introduce other science applications that our pipeline enables.
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    SALT3: An Improved Type Ia Supernova Model for Measuring Cosmic Distances
    Kenworthy, WD; Jones, DO; Dai, M; Kessler, R; Scolnic, D; Brout, D; Siebert, MR; Pierel, JDR; Dettman, KG; Dimitriadis, G; Foley, RJ; Jha, SW; Pan, Y-C; Riess, A; Rodney, S; Rojas-Bravo, C
    A spectral-energy distribution (SED) model for Type Ia supernovae (SNe Ia) is a critical tool for measuring precise and accurate distances across a large redshift range and constraining cosmological parameters. We present an improved model framework, SALT3, which has several advantages over current models including the leading SALT2 model (SALT2.4). While SALT3 has a similar philosophy, it differs from SALT2 by having improved estimation of uncertainties, better separation of color and light-curve stretch, and a publicly available training code. We present the application of our training method on a cross-calibrated compilation of 1083 SNe with 1207 spectra. Our compilation is $2.5\times$ larger than the SALT2 training sample and has greatly reduced calibration uncertainties. The resulting trained SALT3.K21 model has an extended wavelength range $2000$-$11000$ angstroms (1800 angstroms redder) and reduced uncertainties compared to SALT2, enabling accurate use of low-$z$ $I$ and $iz$ photometric bands. Including these previously discarded bands, SALT3.K21 reduces the Hubble scatter of the low-z Foundation and CfA3 samples by 15% and 10%, respectively. To check for potential systematic uncertainties we compare distances of low ($0.01
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    Supernova Host Galaxies in the Dark Energy Survey: I. Deep Coadds, Photometry, and Stellar Masses
    Wiseman, P; Smith, M; Childress, M; Kelsey, L; Möller, A; Gupta, RR; Swann, E; Angus, CR; Brout, D; Davis, TM; Foley, RJ; Frohmaier, C; Galbany, L; Gutiérrez, CP; Inserra, C; Kessler, R; Lewis, GF; Lidman, C; Macaulay, E; Nichol, RC; Pursiainen, M; Sako, M; Scolnic, D; Sommer, NE; Sullivan, M; Tucker, BE; Abbott, TMC; Aguena, M; Allam, S; Avila, S; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, DL; Rosell, AC; Carollo, D; Kind, MC; da Costa, LN; de Vicente, J; Desai, S; Diehl, HT; Doel, P; Eifler, TF; Everett, S; Fosalba, P; Frieman, J; García-Bellido, J; Gaztanaga, E; Gerdes, DW; Gill, MSS; Glazebrook, K; Gruendl, RA; Gschwend, J; Hartley, WG; Hinton, SR; Hollowood, DL; Honscheid, K; James, DJ; Kuehn, K; Kuropatkin, N; Lima, M; Maia, MAG; March, M; Martini, P; Melchior, P; Menanteau, F; Miquel, R; Ogando, RLC; Paz-Chinchón, F; Plazas, AA; Romer, AK; Roodman, A; Sanchez, E; Scarpine, V; Serrano, S; Suchyta, E; Swanson, MEC; Tarle, G; Thomas, D; Tucker, DL; Varga, TN; Walker, AR; Wilkinson, RD
    The five-year Dark Energy Survey supernova programme (DES-SN) is one of the largest and deepest transient surveys to date in terms of volume and number of supernovae. Identifying and characterising the host galaxies of transients plays a key role in their classification, the study of their formation mechanisms, and the cosmological analyses. To derive accurate host galaxy properties, we create depth-optimised coadds using single-epoch DES-SN images that are selected based on sky and atmospheric conditions. For each of the five DES-SN seasons, a separate coadd is made from the other 4 seasons such that each SN has a corresponding deep coadd with no contaminating SN emission. The coadds reach limiting magnitudes of order $\sim 27$ in $g$-band, and have a much smaller magnitude uncertainty than the previous DES-SN host templates, particularly for faint objects. We present the resulting multi-band photometry of host galaxies for samples of spectroscopically confirmed type Ia (SNe Ia), core-collapse (CCSNe), and superluminous (SLSNe) as well as rapidly evolving transients (RETs) discovered by DES-SN. We derive host galaxy stellar masses and probabilistically compare stellar-mass distributions to samples from other surveys. We find that the DES spectroscopically confirmed sample of SNe Ia selects preferentially fewer high mass hosts at high redshift compared to other surveys, while at low redshift the distributions are consistent. DES CCSNe and SLSNe hosts are similar to other samples, while RET hosts are unlike the hosts of any other transients, although these differences have not been disentangled from selection effects.
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    Supernova Siblings: Assessing the Consistency of Properties of Type Ia Supernovae that Share the Same Parent Galaxies
    Scolnic, D; Smith, M; Massiah, A; Wiseman, P; Brout, D; Kessler, R; Davis, TM; Foley, RJ; Galbany, L; Hinton, SR; Hounsell, R; Kelsey, L; Lidman, C; Macaulay, E; Morgan, R; Nichol, RC; Möller, A; Popovic, B; Sako, M; Sullivan, M; Thomas, BP; Tucker, BE; Abbott, TMC; Aguena, M; Allam, S; Annis, J; Avila, S; Bechtol, K; Bertin, E; Brooks, D; Burke, DL; Rosell, AC; Carollo, D; Kind, MC; Carretero, J; Costanzi, M; Da Costa, LN; De Vicente, J; Desai, S; Diehl, HT; Doel, P; Drlica-Wagner, A; Eckert, K; Eifler, TF; Everett, S; Flaugher, B; Fosalba, P; Frieman, J; Garciá-Bellido, J; Gaztanaga, E; Gerdes, DW; Glazebrook, K; Gruen, D; Gruendl, RA; Gschwend, J; Gutierrez, G; Hartley, WG; Hollowood, DL; Honscheid, K; James, DJ; Kuehn, K; Kuropatkin, N; Lewis, GF; Li, TS; Lima, M; Maia, MAG; Marshall, JL; Menanteau, F; Miquel, R; Palmese, A; Paz-Chinchón, F; Plazas, AA; Pursiainen, M; Sanchez, E; Scarpine, V; Schubnell, M; Serrano, S; Sevilla-Noarbe, I; Sommer, NE; Suchyta, E; Swanson, MEC; Tarle, G; Varga, TN; Walker, AR; Wilkinson, R
    While many studies have shown a correlation between properties of the light curves of Type Ia SN (SNe Ia) and properties of their host galaxies, it remains unclear what is driving these correlations. We introduce a new direct method to study these correlations by analyzing `parent' galaxies that host multiple SNe Ia 'siblings'. Here, we search the Dark Energy Survey SN sample, one of the largest samples of discovered SNe, and find 8 galaxies that hosted two likely Type Ia SNe. Comparing the light-curve properties of these SNe and recovered distances from the light curves, we find no better agreement between properties of SNe in the same galaxy as any random pair of galaxies, with the exception of the SN light-curve stretch. We show at $2.8\sigma$ significance that at least 1/2 of the intrinsic scatter of SNe Ia distance modulus residuals is not from common host properties. We also discuss the robustness with which we could make this evaluation with LSST, which will find $100\times$ more pairs of galaxies, and pave a new line of study on the consistency of Type Ia supernovae in the same parent galaxies. Finally, we argue that it is unlikely some of these SNe are actually single, lensed SN with multiple images.
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    Synergies between Vera C. Rubin Observatory, Nancy Grace Roman Space Telescope, and Euclid Mission: Constraining Dark Energy with Type Ia Supernovae
    Rose, BM; Aldering, G; Dai, M; Deustua, S; Foley, RJ; Gangler, E; Gris, Ph; Hook, IM; Kessler, R; Narayan, G; Nugent, P; Ponder, S Perlmutte KA; Racine, B; Rubin, D; Sánchez, BO; Scolnic, DM; Wood-Vasey, WM; Brout, D; Cikota, A; Fouchez, D; Garnavich, PM; Hounsell, R; Sako, M; Tao, C; Jha, SW; Jones, DO; Strolger, L; Qu, H
    We review the needs of the supernova community for improvements in survey coordination and data sharing that would significantly boost the constraints on dark energy using samples of Type Ia supernovae from the Vera C. Rubin Observatories, the \textit{Nancy Grace Roman Space Telescope}, and the \textit{Euclid} Mission. We discuss improvements to both statistical and systematic precision that the combination of observations from these experiments will enable. For example, coordination will result in improved photometric calibration, redshift measurements, as well as supernova distances. We also discuss what teams and plans should be put in place now to start preparing for these combined data sets. Specifically, we request coordinated efforts in field selection and survey operations, photometric calibration, spectroscopic follow-up, pixel-level processing, and computing. These efforts will benefit not only experiments with Type Ia supernovae, but all time-domain studies, and cosmology with multi-messenger astrophysics.
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    The Dark Energy Survey Supernova Program: Cosmological biases from supernova photometric classification
    Vincenzi, M; Sullivan, M; Möller, A; Armstrong, P; Bassett, BA; Brout, D; Carollo, D; Carr, A; Davis, TM; Frohmaier, C; Galbany, L; Glazebrook, K; Graur, O; Kelsey, L; Kessler, R; Kovacs, E; Lewis, GF; Lidman, C; Malik, U; Nichol, RC; Popovic, B; Sako, M; Scolnic, D; Smith, M; Taylor, G; Tucker, BE; Wiseman, P; Aguena, M; Allam, S; Annis, J; Asorey, J; Bacon, D; Bertin, E; Brooks, D; Burke, DL; Rosell, A Carnero; Carretero, J; Castander, FJ; Costanzi, M; Costa, LN da; Pereira, MES; Vicente, J De; Desai, S; Diehl, HT; Doel, P; Everett, S; Ferrero, I; Flaugher, B; Fosalba, P; Frieman, J; García-Bellido, J; Gerdes, DW; Gruen, D; Gutierrez, G; Hinton, SR; Hollowood, DL; Honscheid, K; James, DJ; Kuehn, K; Kuropatkin, N; Lahav, O; Li, TS; Lima, M; Maia, MAG; Marshall, JL; Miquel, R; Morgan, R; Ogando, RLC; Palmese, A; Paz-Chinchón, F; Pieres, A; Malagón, AA Plazas; Reil, K; Roodman, A; Sanchez, E; Schubnell, M; Serrano, S; Sevilla-Noarbe, I; Suchyta, E; Tarle, G; To, C; Varga, TN; Weller, J; Wilkinson, RD
    Cosmological analyses of samples of photometrically-identified Type Ia supernovae (SNe Ia) depend on understanding the effects of 'contamination' from core-collapse and peculiar SN Ia events. We employ a rigorous analysis on state-of-the-art simulations of photometrically identified SN Ia samples and determine cosmological biases due to such 'non-Ia' contamination in the Dark Energy Survey (DES) 5-year SN sample. As part of the analysis, we test on our DES simulations the performance of SuperNNova, a photometric SN classifier based on recurrent neural networks. Depending on the choice of non-Ia SN models in both the simulated data sample and training sample, contamination ranges from 0.8-3.5 %, with the efficiency of the classification from 97.7-99.5 %. Using the Bayesian Estimation Applied to Multiple Species (BEAMS) framework and its extension 'BEAMS with Bias Correction' (BBC), we produce a redshift-binned Hubble diagram marginalised over contamination and corrected for selection effects and we use it to constrain the dark energy equation-of-state, $w$. Assuming a flat universe with Gaussian $\Omega_M$ prior of $0.311\pm0.010$, we show that biases on $w$ are $<0.008$ when using SuperNNova and accounting for a wide range of non-Ia SN models in the simulations. Systematic uncertainties associated with contamination are estimated to be at most $\sigma_{w, \mathrm{syst}}=0.004$. This compares to an expected statistical uncertainty of $\sigma_{w,\mathrm{stat}}=0.039$ for the DES-SN sample, thus showing that contamination is not a limiting uncertainty in our analysis. We also measure biases due to contamination on $w_0$ and $w_a$ (assuming a flat universe), and find these to be $<$0.009 in $w_0$ and $<$0.108 in $w_a$, hence 5 to 10 times smaller than the statistical uncertainties expected from the DES-SN sample.
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    The Dark Energy Survey Supernova Program: Modelling selection efficiency and observed core collapse supernova contamination
    Vincenzi, M; Sullivan, M; Graur, O; Brout, D; Davis, TM; Frohmaier, C; Galbany, L; Gutiérrez, CP; Hinton, SR; Hounsell, R; Kelsey, L; Kessler, R; Kovacs, E; Kuhlmann, S; Lasker, J; Lidman, C; Möller, A; Nichol, RC; Sako, M; Scolnic, D; Smith, M; Swann, E; Wiseman, P; Asorey, J; Lewis, GF; Sharp, R; Tucker, BE; Aguena, M; Allam, S; Avila, S; Bertin, E; Brooks, D; Burke, DL; Rosell, AC; Kind, MC; Carretero, J; Castander, FJ; Choi, A; Costanzi, M; Da Costa, LN; Pereira, MES; De Vicente, J; Desai, S; Diehl, HT; Doel, P; Everett, S; Ferrero, I; Fosalba, P; Frieman, J; Garciá-Bellido, J; Gaztanaga, E; Gerdes, DW; Gruen, D; Gruendl, RA; Gutierrez, G; Hollowood, DL; Honscheid, K; Hoyle, B; James, DJ; Kuehn, K; Kuropatkin, N; Maia, MAG; Martini, P; Menanteau, F; Miquel, R; Morgan, R; Palmese, A; Paz-Chinchón, F; Plazas, AA; Romer, AK; Sanchez, E; Scarpine, V; Serrano, S; Sevilla-Noarbe, I; Soares-Santos, M; Suchyta, E; Tarle, G; Thomas, D; To, C; Varga, TN; Walker, AR; Wilkinson, RD
    The analysis of current and future cosmological surveys of type Ia supernovae (SNe Ia) at high-redshift depends on the accurate photometric classification of the SN events detected. Generating realistic simulations of photometric SN surveys constitutes an essential step for training and testing photometric classification algorithms, and for correcting biases introduced by selection effects and contamination arising from core collapse SNe in the photometric SN Ia samples. We use published SN time-series spectrophotometric templates, rates, luminosity functions and empirical relationships between SNe and their host galaxies to construct a framework for simulating photometric SN surveys. We present this framework in the context of the Dark Energy Survey (DES) 5-year photometric SN sample, comparing our simulations of DES with the observed DES transient populations. We demonstrate excellent agreement in many distributions, including Hubble residuals, between our simulations and data. We estimate the core collapse fraction expected in the DES SN sample after selection requirements are applied and before photometric classification. After testing different modelling choices and astrophysical assumptions underlying our simulation, we find that the predicted contamination varies from 5.8 to 9.3 per cent, with an average of 7.0 per cent and r.m.s. of 1.1 per cent. Our simulations are the first to reproduce the observed photometric SN and host galaxy properties in high-redshift surveys without fine-tuning the input parameters. The simulation methods presented here will be a critical component of the cosmology analysis of the DES photometric SN Ia sample: correcting for biases arising from contamination, and evaluating the associated systematic uncertainty.