Status of the ESSENCE project

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Status of the ESSENCE project

• Bruno Leibundgut(ESO)
• mostly work by Gajus Miknaitis, Nick Suntzeff,
  Chris Smith and Stéphane Blondin

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SN Projects
SN Factory Carnegie SN Project
ESSENCE CFHT Legacy Survey
Higher-z SN Search (GOODS)
SNAP
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High-Z Team Results
230 SNe 0.3 lt z lt 1.2
(OM,O?) (0.3,0.7), (0.3,0.0), (1.0,0.0)
Tonry et al (2003), Barris et al (2004)
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Riess et al. 2004
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The new challenge

• So far ? had been assumed to be a constant, i.e.
  time-independent, in most analyses.
• Not necessarily true for all proposed forms of
  dark energy.
• Equation of state parameter ? can substitute
  for the cosmological constant.

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The equation of state parameter ?

• General luminosity distance
• with and
• ?M 0 (matter)
• ?R ? (radiation)
• ?? -1 (cosmological constant)
• Note ? assumed to be constant!

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SN Ia and 2dF constraints
2dF ? M h 0.2 0.03
KP h 0.72 0.08
Tonry et al. 2003
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Nature of the dark energy
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ESSENCE

• Equation of State SupErNovae trace Cosmic
  Expansion.
• In 2001, the High-Z SN Team morphed into
  Higher-Z (Riess et al.) and ESSENCE (Stubbs,
  Suntzeff et al.)
• Five year mission to measure ? to 10 accuracy

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ESSENCE Survey Team
Bruno Leibundgut --- European Southern
Observatory Weidong D. Li --- Univ of
California, Berkeley Thomas Matheson ---
Harvard-Smithsonian CfA Jose Luis Prieto
CTIO/NOAO Gajus Miknaitis --- Univ of
Washington Armin Rest --- Univ of
Washington/CTIO Adam G. Riess --- Space
Telescope Science Institute Brian P.
Schmidt --- Mt. Stromlo Siding Springs
Observatories Chris Smith --- CTIO/NOAO
Jesper Sollerman --- Stockholm Observatory
Jason Spyromilio --- European Southern
Observatory Christopher Stubbs --- Univ of
Washington Nicholas B. Suntzeff ---
CTIO/NOAO Michael Wood-Vasey ---
Harvard-Smithsonian CfA John L. Tonry ---
Univ of Hawaii
Claudio Aguilera --- CTIO/NOAO Brian
Barris --- Univ of Hawaii Andy Becker ---
Bell Labs/Univ. of Washington Stephan
Blondin Univ Munich Peter Challis ---
Harvard-Smithsonian CfA Ryan Chornock ---
Harvard-Smithsonian CfA Alejandro
Clocchiatti --- Univ Catolica de Chile
Ricardo Covarrubias --- Univ of Washington
Alex V. Filippenko --- Univ of Ca, Berkeley
Ryan Foley --- Univ. of Ca, Berkeley Peter
M. Garnavich --- Notre Dame University
Stephen Holland --- Notre Dame University
Saurabh Jha --- Harvard-Smithsonian CfA
Robert Kirshner --- Harvard-Smithsonian CfA
Kevin Krisciunas --- LCO CTIO/NOAO
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Essence Survey Goal ?
Monte Carlo of
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A joint analysis, including results from
Supernovae, CMB, and large scale
structure should allow us to determine equation
of state parameter ? to 10.
L
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The signal we are looking for
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The Experiment

• CTIO 4m with Mosaic imager
• 150 half nights over 5 yrs
• 3 lunations, every other night, avoiding full
  moon
• Broadband RIV filters
• 32 fields, 0.36 arc-deg per field
• 13 sq-deg search
• 200s R, 400 I, V when needed
• Limits at S/N7 - 23.5 (R), 23.0 (I)
• Remote observing from La Serena

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ESSENCE survey implementation

• NOAO Survey on CTIO 4m, MOSAIC
• Same frame subtraction pipeline as SuperMacho
  project, scheduled in other halves of
  SuperMacho nights
• 200 supernovae with 0.25 lt z lt 0.75
• 2 sets of 16 fields, ?t4 days, 12 sq-deg total
• Goal is to determine a distance modulus in each
  bin (of ?z 0.1) to 2 (statistical)
• 3 photometry at peak SN brightness

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Preliminary Steps - MSCpipe

• Common software for Supermacho and ESSENCE
• Recognizes images, zeros and flats
• Crosstalk correction with IRAF executables
• Mosaic image WCS registration with IRAF
  msccmatch, to UCAC2 catalog, typical rms of 0.05
  arcsec
• Chopping into amplifiers for parallel processing.

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Followed by SN search

• Automatic detection of variable sources
• Check for proper motions (asteroids)
• Visual inspection of each object (e.g. location
  within galaxy) and check of the variability
  history of each candidate
• Use colour criterion to further select SN Ia
  candidates

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Discoveries are announced immediately on our web
site.
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Astrometry, magnitudes, and finding charts are
published to the web.
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SNe from Oct 2003
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Beyond the searches

• light curves
• photometric zero-points
• extinction
• light curve shape corrections
• classifications
• spectroscopy
• K-corrections
• Remember We need 3 accuracy of peak brightness!

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follow-up observations

• z gt 0.5 SNe sent to HST
• spectroscopy for classifications from Keck, VLT,
  Magellan, MMT, Gemini, Mt. Hopkins
• photometric calibrations from 1.5m and 0.9m at
  CTIO
• limited photometric follow-up at WIYN and Gemini

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ESSENCE spectroscopy - an overview

• spectroscopy is vital
• ? one axis on Hubble Diagram
• (2) we now have decent spectra
• e.g. from VLT 2003 campaign

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Progress to date

• Finished second year out of five

2002 Ia 15 II 6 other 8
2003 Ia 37 II 4 other 13
Total (2 yr) Ia 52 II 10 other 21
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Conclusions (I)

• After two years ESSENCE is on track for its goal
  of 200 SNe Ia in five years
• first year severely affected by inclement
  atmospheric conditions ? 15 SNe Ia
• second year regular ? 37 SNe Ia
• better discrimination against other variable
  objects in the second year
• Spectroscopy is still the bottle neck
• several good light curves without a SN spectrum
  (potentially could get redshift from galaxy)

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Conclusions (II)

• Detailed analysis of photometry only starting
• photometric zero points (Vega!)
• colour terms (depends on individual CCDs in the
  camera)
• total efficiency of optical train (telescope and
  camera)
• important for colours, extinction,
  K-corrections, light curve shapes and peak
  brightness