SNe Ia in the PTF/iPTF and ZTF eras: - Lessons and prospects

SNe Ia in the PTF/iPTF and ZTF eras: - Lessons and prospects

Ariel Goobar The Oskar Klein Centre Stockholm University

+ the SNIa group@OKC: R.Amanullah, U.Feindt, R.Ferretti, L.Hangard, M.Kromer, S.Papadagionnakis, T.Petrushevska and the iPTF/ZTF collaborations

Palomar Observatory

Rapa Nui, August 2016 Ariel Goobar

P48 survey telescope

P60 classification

telescope News: SEDM

P200 Spectroscopy

From 1940’s!


P48 (Samuel Oschin Telescope)

From 2010’s!


P48 (Samuel Oschin Telescope)

7.2 deg2 operational

Typical operation: 60 s exposures + 36 s readout: Pixel size: 1”, S/N=5 for 21 mag in R and g


•  Cadence for PTF/iPTF has been changing over time/seasons •  350 identified SNe/yr, ~70% SNIa

Ia,1865

II,632

Ib/c,141 SLSN,47


PTF/iPTF in action: R-band

Raw data

processing

Reference Image

Image Subtraction

Real-Bogus (reject false

alarms)

Star/asteroid Identification

3 min

1.5 min/ image

0.5 min/ image

Local galaxy match

Load candidates

Into database

0.5 min/image

Scanning Page: human screening mainly in Israel and Stockholm

Database

COURTESY OF YI CAO & MANSI KASLIWAL

(Palomar -> Caltech -> LBL)�


Pipeline flow-chart

mag

Discovery: 50 times fainter than at peak

Early observations of SNe: §  Search for evidence of shock heating, interaction with

companion star, CSM or other sources of (added) luminosity.

§  Multi-wavelength follow-up observations to study extinction along line of sight (NIR and UV for a few, see Rahman’s talk on Saturday).

D~100 Mpc (z=0.0159)


SWIFT image

LCOGT follow-up

Time-line of follow-up of iPTF13dge


Better be fast to detect photoionization of CSM!

Rapa Nui, August 2016 Ariel Goobar Ferretti+16


R- B A N D

Cao+ in prep Papadogionnakis + in prep

4.5μm (-4.0)K (-3.5)

H (-3.0)J (-2.5)Y (-2.0)z (-2.0)i (-1.5)r (-1.0)

R (+0.0)V (+0.0)

g (+0.0)B (+0.0)

U (+0.0)

Non-detection in R (>20 mag) : iPTF detection in Halpha

Jan 13.47 Jan 15.18

: Zheng et al. 2014

Subtraction Subtraction

: Fossey et al. 2014

Mt. Abu ObservatoryLCOGTPalomar P48/P60NOT

Narrow band imaging during bright time...


SN2014J

AG+14

Something else powering the early rise?

Ariel Goobar

15

WD size + t2 excluded at 90% CL

November 2014

Bigger star? Companion? Accretion disk ? Tidal tail? Surface radioactivity?

iPTF+KELT AG+15

SN2011fe: vanilla

Ariel Goobar

16

Data from Nugent et al 2011

November 2014

AG+15

F. Zwicky (1898-1974): pioneer of transient astromomy.

The Zwicky Transient Facility


Scaling up: ZTF x15 faster! - can do all available sky every clear night

PTF/iPTF, 7.3 deg2

HSC,

1.7 deg2

ZTF, 47 deg2

1 deg

LSST, 9.6 deg2

PS1, 7 deg2

DES,

2.5 deg2

Survey start: one year from nowtelescope!Rapa Nui, August 2016 Ariel Goobar

Room for improvement (I)

PTF/iPTF: Non-optimal changes of fields, driven by other science. Only 25% of SNe have well-sample lightcurves covering both pre- and post-maximum. We should do a lot better with ZTF, as there will not be need for constant changes of fields


Cosmology accuracy improvement with PTF è ZTF

Single band iPTF/PTF Hubble diagram: large scatter!

ΔmB = AB = (Rv +1) ⋅E(B −V )

σ µ (z)∝

σ m

N≈1310

⇒σ µ

ZTF

σ µPTF ∼ 0.1

Papadogiannakis et al in prep.

Room for improvement (II)

What is the origin of the accelerated cosmic expansion?

•  Cosmological constant (Λ), consistent with existing data but is 1060-10120 times lower than the expected vacuum energy density

•  Completely new physics?

•  Combined studies of low- and high-redshift SNe provides the key for testing models for the cosmic acceleration: time-evolution

•  High-z, HST programs now; WFIRST in the future

•  ZTF: can provide critical low-z sample

Time-dependence of dark energy

Der

ivat

ive

of ti

me-

depe

nden

ce o

f dar

k en

ergy

Cosmological constant

Current measurementprecision on dark energy

Alternative models

Target precision forcombined analysis offuture experiments

(w0)

(wa)

ρDE = ρDE0 a−3(1+w);w =w0 +wa (1− a)

→ w = −1 makes ρDE constant

Adapted from AG & Leibundgut 2011

Anchoring the Hubble diagram DE FoM significantely improved with ~2000 SNe Ia @ z≤0.1

Time-dependence of dark energy

Der

ivat

ive

of ti

me-

depe

nden

ce o

f dar

k en

ergy

Cosmological constant

Current measurementprecision on dark energy

Alternative models

Target precision forcombined analysis offuture experiments

Room for improvement (III) Calibration requirements – impact of photometric bias

ZTF data alone sensitive to ”local” cosmic acceleration

Minimum 2 bands - and at least 3 to also fit Rv

Milky-Way-type dust

Fit to data yield lower Rv

ΔmB = AB = (Rv +1) ⋅E(B −V )

Prospects of also measuring average RV with gri

ZTF Ia spectroscopicsample

Monte-Carlo study using low-z reddening and Rv distributions

Prospects of also measuring average RV with gri

ZTF Ia spectroscopicsample

Propagated error from extinction uncertainties within ~1% cap

Target SNIa sample

SNIa rates: 3-4000 SNe Ia/year within FoV and redshift range of interest

n  2000 spectroscopicaly ID:ed SNe Ia in galaxies (ideally in the DESI footprint) and within PTF Hα survey.

n  Redshift range z≤ 0.1; with up to 1 mag reddening discovered >1 mag below peak.

n  High galactic latitude, E(B-V)MW < 0.1

n  P48 photometric coverage: gr + ideally i-band (1 week cadence, reddening + typing)

n  2-filter lightcurves (gr) with 3-day cadence, SNR>10 (TBD), ≥15 points. Coverage to day +40

n  High-cadence sample, single band (~2000 sq.deg), for very early discoveries

n  Multi-band + spectroscopy follow-up highly desireable (talk to us!)



Angular dependent Hubble diagram: studying matter distribution from coherent motions: challeng CDM?

Dipole vs ΛCDM prediction: ZTF in the right ballpark


Current SN results

ΛCDM

Feindt+ in prep. Will hear some more in Tamara’s talk!

Summary & Outlook

n  PTF/iPTF has been an excellent discovery machine: including early rise LCs for ~40 SNe Ia.

n  Long term follow-up for good fraction – but change of fields lead to inefficiencies.

n  ZTF even better survey for producing the low-z SNIa anchoring sample for precision cosmology to put ΛCDM to severe tests: great legacy value!

n  Survey strategy TBD (to be settled by end of year), but at least 2 filters and possibly 3 are being discussed.

n  Aiming at 1% (or better) photometric accuracy n  Welcome partners for spectroscopic and multiband follow-

up.


Thank You!


SNe Ia in the PTF/iPTF and ZTF eras: - Lessons and prospects

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