padua: 1604 → 2004 – supernovae as cosmological lighthouses snls – the supernova legacy survey...

Padua: 1604 Padua: 1604 →→ 2004 – Supernovae as cosmological lighthouses 2004 – Supernovae as cosmological lighthouses

SNLS – The SuperNova Legacy SNLS – The SuperNova Legacy SurveySurvey

Mark Sullivan Mark Sullivan (University of Toronto)(University of Toronto)

on behalf of the SNLS on behalf of the SNLS collaborationcollaboration

http://cfht.hawaii.edu/SNLS/


The 5-year CFHT Legacy Survey… in 10 The 5-year CFHT Legacy Survey… in 10 minutesminutes

Utilises Utilises Megacam, Megacam, a 36CCD/1 sq deg a 36CCD/1 sq deg imagerimager

Deep/SNLS component has:Deep/SNLS component has:202 nights over 5 years202 nights over 5 years

Repeat observations over four fieldsRepeat observations over four fields

5 epochs per field per month (10 visits/month)5 epochs per field per month (10 visits/month)

g’r’i’z’ observed on each epoch (tweaked to g’r’i’z’ observed on each epoch (tweaked to allow for moon)allow for moon)

Hence rest-frame Hence rest-frame UBVRUBVR sampled every 3-4 sampled every 3-4 days in the SN rest-framedays in the SN rest-frame

Field NameField Name Other Other data/surveysdata/surveys

D1 D1

(02:26,-04)(02:26,-04)VIMOS, SWIRE, GALEX, VIMOS, SWIRE, GALEX,

XMM DeepXMM Deep

D2D2

(10:00,+02)(10:00,+02)COSMOS/ACS, VIMOS, COSMOS/ACS, VIMOS,

SIRTF, GALEX, XMM etc.SIRTF, GALEX, XMM etc.

D3D3

(14:19,+53)(14:19,+53)Groth Strip – ACS, DEEP-II, Groth Strip – ACS, DEEP-II,

GALEX etc.GALEX etc.

D4D4

(22:15,-18)(22:15,-18)XMM DeepXMM Deep


Primary science goalsPrimary science goals

Primary goal: Use SNe Ia to determine “w”Primary goal: Use SNe Ia to determine “w”Many other talks for details on how SNe Ia can help Many other talks for details on how SNe Ia can help to constrain wto constrain wSNLS Goal: 1000 SNe Ia (across all redshifts)SNLS Goal: 1000 SNe Ia (across all redshifts)Calibration goal: 1-2% photometric accuracyCalibration goal: 1-2% photometric accuracy

SNLS provides many consistency checks SNLS provides many consistency checks on the use of SNe Ia, e.g.on the use of SNe Ia, e.g.

SN colour evolution – multi-colour consistency SN colour evolution – multi-colour consistency checkcheckDetailed studies of spectral evolution (e.g. talk by Detailed studies of spectral evolution (e.g. talk by P. Nugent + VLT/Gemini spectra)P. Nugent + VLT/Gemini spectra)Collaboration with Carnegie to construct rest-frame Collaboration with Carnegie to construct rest-frame I-band Hubble diagram (minimise dust extinction)I-band Hubble diagram (minimise dust extinction)


Secondary goals – other SN scienceSecondary goals – other SN science

Type Ia/II SN ratesType Ia/II SN rates co-moving SF density (z), SNe Ia progenitor co-moving SF density (z), SNe Ia progenitor information information

SNe IIP as standard candles via expansion vel.SNe IIP as standard candles via expansion vel.Independent confirmation of accelerating Universe?Independent confirmation of accelerating Universe?

Host galaxy studies (SNLS fields have a Host galaxy studies (SNLS fields have a wealth of wealth of HSTHST imaging + ugriz deep host imaging + ugriz deep host photometry)photometry)

In summary: a wealth of exciting SN scienceIn summary: a wealth of exciting SN science


How it worksHow it works

Data reduced in real-time by ElixirData reduced in real-time by Elixir

Two independent search pipelinesTwo independent search pipelines

PSF-match the “reference” and “epoch” imagesPSF-match the “reference” and “epoch” images

Subtract…Subtract…

… … and search the difference imagesand search the difference images

Real candidate

PSFmatch errors from saturated

objects easily rejected


DetectionsDetections

~90% agreement between the two pipelines to ~90% agreement between the two pipelines to i’=24.5i’=24.5

As of May 2004, the database contains (over 4 fields):As of May 2004, the database contains (over 4 fields):222 AGN candidates222 AGN candidates

328 SN candidates (of all flavours…)328 SN candidates (of all flavours…)

282 “repeatedly varying” stellar objects282 “repeatedly varying” stellar objects

Even with ~120 hours/semester of 8-10m Even with ~120 hours/semester of 8-10m spectroscopic time, we cannot hope to follow all spectroscopic time, we cannot hope to follow all these candidatesthese candidates

However – we have a wealth of real-time photometric However – we have a wealth of real-time photometric information – unprecedented when compared to information – unprecedented when compared to

previous surveysprevious surveys


Photometric pre-screeningPhotometric pre-screening

So, we use a SN photo-z technique to So, we use a SN photo-z technique to identify our priority candidatesidentify our priority candidates

Performs a least-squares fit to 2-3 epochs of data Performs a least-squares fit to 2-3 epochs of data over (over (phasephase,,redshiftredshift,,stretchstretch,reddening) to a Ia ,reddening) to a Ia spectral templatespectral template

Non-SNe Ia screened out (colour e.g. g’-r’, rise-Non-SNe Ia screened out (colour e.g. g’-r’, rise-time..)time..)

(conservative cuts)(conservative cuts)

Identifies priority candidates for follow-up – Identifies priority candidates for follow-up – especially valuable in poor weather conditionsespecially valuable in poor weather conditions


Photometric-redshift analysisPhotometric-redshift analysis

(all spectroscopic redshifts from March May 2004)


Current statusCurrent status

Survey “proper” commenced Aug 1, 2003Survey “proper” commenced Aug 1, 2003(pre-survey March (pre-survey March July 2003) July 2003)

Atrocious winter on Mauna Kea, some technical Atrocious winter on Mauna Kea, some technical issuesissues

All observing is queue-scheduled – big advantage All observing is queue-scheduled – big advantage in poor weather conditionsin poor weather conditions

New priority agreements – SNLS has priority on New priority agreements – SNLS has priority on time-critical nightstime-critical nights


Current status – typical light-curvesCurrent status – typical light-curves

Typical time-sampling from early

(pre-survey and start of survey) SN

discoveries

(this shows real-time Elixir photometry only)


How many SNe will there be?How many SNe will there be?

Cumulative number of supernovae (to end April 2004)



Cumulative number of supernovae to survey end



Cumulative number of supernovae – with photometric typing and a host

redshift


Current status – N(Current status – N(zz))

Current spectroscopic N(z)

(includes SNe from September 2003 April 2004)

~70 SNe Ia from an 8 month period



Total predicted number of detected SNe (detection efficiency calculated by J. Guy)



Total predicted number of spectroscopically followed SNe

Distribution appears

as expected to z=0.6


Predicted cosmological constraintsPredicted cosmological constraints

Constraints on w expected after 5 years based on current survey

progress

(Red indicates constraints using ΩM

determination from CFHTLS “wide” )


Want to know more?Want to know more?

Check out these websites for all the Check out these websites for all the details:details:

Project overview, collaboration members, Project overview, collaboration members, publications:publications:

http://cfht.hawaii.edu/SNLS/http://cfht.hawaii.edu/SNLS/

Candidate database, real-time candidate lists:Candidate database, real-time candidate lists:

http://legacy.astro.utoronto.ca/http://legacy.astro.utoronto.ca/

Also: see posters by A. Howell and S. BasaAlso: see posters by A. Howell and S. Basa

padua: 1604 → 2004 – supernovae as cosmological lighthouses snls – the supernova legacy survey...

Documents

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