• His slides are attached!

ZTF Ia Phone-con: 2021-Apr-14

Meeting Agenda:

1. SNe of the week [Joel J]

2. Measuring fsigma8 from ZTF [Bastien C, Julian B]

3. The Plan for ZTF DR2 [Mat S / Mickael R]

4. AOB / Close

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Participants (20):

• Ariel, Bastien, Benjamin, Dominique, Estelle, Fabrice, Jacco, Jakob, Joel, Julian, Mat, Mattia, Maxime, Melissa, Mickael, Suhail, Young-Log, Philippe, Valery, Nicolas

Notes:

Transients of the Week:

• Plenty to choose from. Mat highlights:
• ZTF21aaqytjr: Nearby - 14Mpc (z=0.0033)
• ZTF21aarqkes: 40Mpc (z=0.0093). Are we getting NIR of these?
• ZTF21aaufvpg: 1st detected at -15 days
• ZTF21aapehpx: Early time bump, now confirmed as a Ia. Also detected early in i-band. Presence of Na in the spectrum. Get a NOT spectrum!
• ZTF21aaplnxw: Over-luminous: SuperCH? The Trinity group are looking at this.
• ZTF21aaqwjlz: In a cluster environment, but hostless. This one is fun

Bastien on measuring fisgma8:

• Working on simulations of what we should see. Using ZTF_SIM (from Eric B)
• Combining pec_vel predictions + SNCosmo + the actual observing conditions to predict how well we can meaure pec_vel
  • Including sigma_int = 0.1
• Early results (200 SNe) suggest that we recover the velocities well without sigma_int; they are washed out a lot when it's included
  • Need to quantify this though
• Going to expand the analysis: simulate ZTF1+ZTF2 (5000 SNe)
  • Increase coordination with the simsurvey team: the observing strategy is already in place
  • Also incorporate ztfquery: this provides all information about actual observing conditions
  • Mat: maybe also consider other models of sigma_int? i.e. C11 over G10?

Julian on the theory: going from velocities to fσ8:

• Measurements of growth of structure allow us to directly test GR. This is particularly important at low-z where predictions diverge.
• Only accessible to SN: there isn't enough volume to do it with LSS surveys (Graziani 2020)
  • To do this we need accurate pec_vel measurements:
• Multiple ways to measure it: he's using a maximum likelihood method (Howlett+ 2017, Ma, Li, He 2015, Johnson, Blake, Koda)
  • Also Comparisons between velocity and density field (Graziani 2019) and the momentum power-spectrum (Howlett 2019).
  • The input to this is the catalogue of velocities
  • The models of the density power-spectrum differ at large scales: this is due to 2nd order clustering.
  • simulations imply that the uncertainties are underestimated, possibly due to the smoothing scale (currently 40Mpc). This is, of course, a balance.
  • Early results suggest that we recover the input: woop! Including intrinsic dispersion washes things out, but we still recover the input!
  • From multiple realisations (of 6400 SNe), the scatter is ~0.05.
• The key is to find accurate unbiased measurements.
  • Need to include photometrically typed events and think about spectroscopic completeness.
  • This is a group-wide effort: Jakob to talk to us about existing work done through Ampel next week :).
• His slides are attached :).

Mat and Mickael on DR2:

• The plan is to organise the 'first 1000 SN' from ZTF. This is probably everything up to the end of ZTFY1.
  • Will include events with a SNID_z.
  • Mat is looking at light-curve properties (along with Mickael), redshifts and host properties.
  • Mickael is looking at spectral properties.
  • Hoping that the group will dive in and use it as a base sample for complementary analyses
• Ariel: don't forget selection: this is clearly going to be important at z>0.06.
  • Mat: YES. Lets hear from Jakob next week and then maybe the simsurvey team :).

Closing Remarks:

• Sign up for a talk!