Strategies to identify strongly lensed type Ia supernovae in Rubin LSST

PRJ 502 MS Thesis Presentation
April 15, 2024

Prajakta Mane
MS19054

Supervisors:
Prof. Surhud More, Dr. Anupreeta More
IUCAA, Pune

Local Supervisor:
Prof. Jasjeet Singh Bagla

Why strongly lensed: Time delay cosmography

\frac{D_d D_s}{D_{ds}} = \frac{1}{H_0} f(z_s, z_l, \Omega_m, \Omega_\Lambda )
\Delta t = \frac{D_d D_s}{cD_{ds}}(1+z_l)\Delta\tau \text{+ constant}

accurate time delays, surface mass distribution and redshift of lens

Hubble constant with strong lensing time delays

well-constrained Hubble Constant

Hubble constant constraints from 6 lensed quasars, Wong et al., 2019

Time delay cosmography:

\frac{D_d D_s}{D_{ds}} = \frac{1}{H_0} f(z_s, z_l, \Omega_m, \Omega_\Lambda )

accurate time delays, surface mass distribution and redshift of lens

Hubble constant with strong lensing time delays

well-constrained Hubble Constant

Why SNe Ia

  • well-studied light curves -> more accurate time delay measurements

  • transient source -> improved constraints on the lens galaxy model

  • standard candle nature -> help overcome degeneracies

Current lensed supernova sample

H_0 = 75.4^{+8.1}_{−5.5}
H_0 = 66.6^{+4.1}_{-3.3}

PRJ 501: Recap

Quimby et al., 2014

PRJ 502

DIA Results

Template Image

Science Image

Difference Image

Template Image

Science Image

Yellow circles of radius 1": injected lensed SNe

DIA Results

Template Image

Science Image

Difference Image

Yellow circles of radius 1": injected lensed SNe

Red circles of radius 2": diaSources

\text{unresolved quads}
\text{resolved doubles}
\text{unresolved}\\\text{doubles}

DIA Results

Template Image

Science Image

Difference Image

Yellow circles of radius 1": injected lensed SNe

Red circles of radius 2": diaSources

DIA Results

Quad system

Template Image

Science Image

Difference Image

Yellow circles of radius 1": injected lensed SNe

Red circles of radius 2": diaSources

DIA Results

double system

  • Total recovery fraction ~70%​​
  • Slightly higher for quads
  • Decreases significantly for the y-band
Injected Detected % recovery
Total 74k 51.5k 70
Doubles 70k 48.3k 70
Quads 4.1k 3.2k 78
g 310 260 83
r 5.4k 4.7k 86
i 14k 11k 80
z 21k 16k 76
y 34k 20k 58

Lens system level analysis:

Is there a diaSource within the radius of 3" from each lens center in each epoch?

Analysis of DIA results

Difference imaging analysis

Recovery fraction variation with injected unresolved magnitude for each band

  • Recovery fraction decreases for fainter systems -> cutoff brightness.
  • Cutoff brightness varies across bands.

Lens system level analysis

band g r i z y
single-epoch depth 26.4 26.3 26.0 25.6 24.6

Yasuda et al., 2019

Difference imaging analysis

Total EUR Total ER
Total DUR 99.42 93.40
Total DR 0.56 6.60

Individual image level analysis:

How many unique diaSources were found corresponding to each lens system?

A single diaSource for entire system: Pipeline could not resolve the system (DUR): ~49k

Two or more diaSources for a system: Pipeline could resolve the system (DR): 1285

band median seeing(")
g 0.74
r 0.62
i 0.64
z 0.59
y 0.74
  • Pipeline could overall resolve 6.6% systems that had max separation greater than the median seeing of the corresponding band.
  • This 'resolved fraction' was higher for the i, r, and z bands.
\theta_{max}

< median seeing: expected to be unresolved (EUR)

\theta_{max}

> median seeing: expected to be resolved (ER)

Aihara et al., 2017

Difference imaging analysis

Resolved fraction with respect to median seeing of each band

Individual image level analysis:

Doubles

Quads

vertical dashed line: median seeing

Summary

  • Employed difference imaging pipeline recovers ~70% of the injected data of lensed SNe Ia.
  • The recovery fraction decreases for fainter injected systems. It is slightly higher for quads and decreases significantly for the HSC y-band.
  • The resolved fraction is weakly correlated with the angular separation of system for the doubles.

Color-magnitude analysis

Quimby et al. 2014

         : Unlensed SNIa

         : Unlensed core collapse

         : Lensed SNIa
         : Lensed core collapse

 

The redder supernovae for given i-band magnitude are more likely to be lensed SNeIa when studied for unresolved photometry on rising phase of light curve.

The black bold curve separates the lensed SNeIa from unlensed both on the rising and the falling edge of light curve for z < 2.4

Contamination from unlensed SNe is neglegible.

Contamination from CC SNe

Color-magnitude analysis

Contamination from unlensed SNe is neglegible.

Contamination from CC SNe

Color-magnitude analysis

Primary contaminants are lensed SNe Ib and Ic.

Summary of results

  • Employed difference imaging pipeline recovers ~70% of the injected data of lensed SNe Ia.
  • The recovery fraction decreases for fainter injected systems. It is slightly higher for quads and decreases significantly for the HSC y-band.
  • The resolved fraction is weakly correlated with the angular separation of system for the doubles.
  • Colour-magnitude effectively selects lensed SNe Ia for simulated and observed (un-)lensed SNe Ia till redshift 2.4, both on rising and falling edge. Contamination from unlensed CC SNe is low. Primary contaminants are lensed CC SNe Ib and Ic.

Thank you!

Ongoing work

  • Combine detections across epochs and study trends.
  • Study extended DIA sources to check if extendedness can be used as a marker for a lensed system.
  • Incorporate LSST cadence.

Extra slides

Extra slides

Extra slides

The criteria hold well for the observed unlensed and lensed SNeIa.

Extra slides

Extra slides

Difference imaging analysis

Resolved fraction with respect to median seeing of each band

\theta_{max} < \text{median seeing}
\text{Pipeline could not resolve}
\theta_{max} > \text{median seeing}
\text{Pipeline could not resolve}

Individual image level analysis:

Difference imaging analysis

Resolved fraction with respect to median seeing of each band

\theta_{max} > \text{median seeing}
\text{Pipeline could resolve}
\theta_{max} > \text{median seeing}
\text{Pipeline could resolve: only doubles}

some trend

Individual image level analysis

Difference imaging analysis

Resolved fraction with respect to median seeing of each band

\theta_{max} > \text{median seeing}
\text{Pipeline could resolve}
\theta_{max} > \text{median seeing}
\text{Pipeline could resolve: only quads}

no trend

Individual image level analysis

Comaparison of unlensed CC SNe CMDs from low and high redshift

PRJ 501: Recap

Quimby et al. 2014

PRJ 502

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