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| META TOPICPARENT |
name="SNeIa" |
Simulation of SNe Observation for Survey Strategy Observations
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> | All simulation results presented on this page have been obtained assuming a survey rate of 3760 square degrees/hour and 8 hour nights. A simple weather model has been implemented where the probability of observing during a given night is based on historical weather data. |
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Discovery rates
We have based all our discovery rates using the assumption that 15000 square degrees will be covered over a 3-day period in the g and r bands (the MSIP survey), using a fixed schedule. A discovery is defined as two points detected on the rise with S/N > 5, separated by a day or more but within a week. The histogram below shows the number of discoveries in one year of operation, using these assumptions. |
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The Ia sample will be complete out to z~0.1 (based on iPTF, Papadogiannakis et al., in prep.). |
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< | I-band requirements
The SN Ia i-band requirements originate from: 1) lightcurves in at least three filters are necessary for SN Ia distances; 2) SN Ia physics science based on measuring the characteristics of the second peak (time and peak flux) visible at filters redder than the R-band; 3) Detection of the second peak is a unique feature of SNe Ia, and can be used to photometrically type the full sample after the survey complete, which is necessary for detailed and unbiased SN rates studies above the spectroscopic threshold of z=0.1. |
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> | i-band requirements
The SN Ia i-band requirements originate from: 1) lightcurves in at least three filters are necessary for SN Ia distances; 2) SN Ia physics science based on measuring the characteristics of the second peak (time and peak flux) visible at filters redder than the R-band; 3) Detection of the second peak is a unique feature of SNe Ia, and can be used for photometric typing of the full sample, which is necessary for detailed and unbiased SN rates studies above the spectroscopic threshold of z=0.1. |
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SN Ia cosmology |
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< | The primary goal of the ZTF SN Ia survey is to provide a low-z legacy sample for future cosmology analyses. To reach this goal, we require lightcurves of 2000 SNe Ia in at least three bands, as described in the white paper, where the lightcurve of each SN in the sample needs to be measured with a statistical precision that is at the level or better than the intrinsic uncertainty of SNe Ia. For ZTF the limitiation will be the effective cadence of the I-band survey. To estimate the properties of the I-band peak we need at least four data points within -10 < p < +15 days with respect to time of maximum, with at least one point before and one point after maximum. Based on simulation we conclude that this criteria will be reached for 77-88%, 62-82%, 42-70% or 13-18% of the discovered SN Ia sample at z<0.1 for a 4,5,6 and 9 day cadence respectively. The range corresponds to the expected uncertainty due to the weather conditions. The simulations have been carried out assuming weather conditions for 2013 and 2016. The full histogram is shown below. |
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> | The primary goal of the ZTF SN Ia survey is to provide a low-z legacy sample for future cosmology analyses. To reach this goal, we require lightcurves of 2000 SNe Ia in at least three bands, as described in the white paper, where the lightcurve of each SN in the sample needs to be measured with a statistical precision that is at the level or better than the intrinsic uncertainty of SNe Ia. For ZTF, the limitiation will be given by the effective cadence of the i-band survey. To estimate the properties of the i-band peak we need at least four data points within -10 < p < +15 days with respect to time of maximum, with at least one point before and one point after maximum. Based on simulations we conclude that this criteria will be reached for 80-90%, 60-80%, 40-70% or 10-18% of the discovered SN Ia sample at z<0.1 for a 4, 5, 6 and 9 day cadences respectively. The range corresponds to the expected uncertainty due to the weather conditions. The simulations have been carried out based on the weather conditions for 2011 and 2014. The full histogram for 2014 is shown below. |
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< | SN Ia physics with the I-band
The time and characteristic of the second peak is both correlated with the Ni mass of the SN Ia, and provides a promising path for improving standardization of SNe Ia for cosmology. In order to obtain an unbiased measurement of the second peak, it is not enough to sample only the peak itself but also to capture the minimum between the two peaks. In order to do this we require at least 6 datapoints between 10 < p < 50 which will be reached for 68-82%, 44-66%, 26-48% or 11-15% of the discovered SN Ia sample at z<0.1 for a 4,5,6 and 9 day cadence respectively. |
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> | SN Ia physics with the i-band
The time and characteristic of the second peak is both correlated with the Ni mass of the SN Ia, and provides a promising path for improving standardization of SNe Ia for cosmology. In order to obtain an unbiased measurement of the second peak, it is not enough to sample only the peak itself but also to capture the minimum between the two peaks. In order to do this we require at least 6 datapoints between 10 < p < 50 which will be reached for 70-80%, 45-65%, 25-50% or 10-15% of the discovered SN Ia sample at z<0.1 for a 4, 5, 6 and 9 day cadence respectively. |
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< | Post-survey typing using the I-band
The presence of the second peak can be used for photometrically typing using the full lightcurves of all SNe, since this a feature unique to SNe Ia. This will allow us to measure SN Ia rates, both in an absolute sense and environment dependencies, for the full sample, i.e. we are not limited to the spectroscopically confirmed sample at z < 0.1. The requirement for securing the existence of a second peak are less strict than above, and 4 data points are enough between 10 < p < 50 days which will be reached for xx-XX, yy-YY, zz-ZZ of the discovered SN Ia sample at z<0.1 for a 4,5,6 and 9 day cadence respectively. |
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> | Post-survey typing using the i-band
The presence of the second peak can be used for photometric typing using the full lightcurves of all SNe, since this a feature unique to SNe Ia. This will allow us to measure SN Ia rates, both in an absolute sense and environment dependencies, for the full sample, i.e. we are not limited to the spectroscopic confirmed sample at z < 0.1. The requirement for securing the existence of a second peak are less strict than above, and 4 data points are enough between 10 < p < 50 days which will be reached for 85-95%, 80-90%, 70-80%, 30-55% of the discovered SN Ia sample at z<0.1 for a 4, 5, 6 and 9 day cadence respectively. |
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Live candidate typing
Candidate selection will be carried out based on photometric typing based on the presumed host galaxy photometric redshift and the lightcurve during the rise. We are currently development an algorithm for this. Using the same simulations as above we can constrain the contamination in the current implementation of our z < 0.1 sample to 25% of SNe with z > 0.1 . This can be compared to using photo-z only (from Pan-STARRS data) which gives 50%. |
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