automated analysis: sdss, boss, giraffeiac.es/congreso/itn-gaia2013/media/allendeprieto3.pdf · •...
TRANSCRIPT
Automated analysis: SDSS, BOSS, GIRAFFE
• Tests with MILES spectra (R~2000) from the INT (Sanchez Blazquez et al. 2006)
• The same code (FERRE)• Fitting data calibrated in flux and continuum-
normalized
Software
• Gaussian LSF (fiber, wavelength)• Quadratic interpolation of fluxes• Normalization by blocks• Successful tests performed on MILES library
Fittings to MILES spectra
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Continuum on
MILES parameters (Cenarro et al. 2009)
ThisWork
[Fe/H] Teff logg
Distributions of residuals
Continuum off
[Fe/H] Teff logg
MILES parameters (Cenarro et al. 2009)
ThisWork
Distributions of residuals
Recent trends in spectroscopic studies• 3D model atmospheres: a beginning• full NLTE: good progress for hot stars, but …• Data archival: survey projects going on with
massive archives that become public (low-res: SDSS, SEGUE, GALEX) (high-res: Elodie, S4N)
• Analysis automation: a beginning• Breaking the Z barrier
The Desirable future• 3D model atmospheres• full NLTE• A pending observational test for solar-type stars:
center-to-limb variation of the solar spectrum• Data archival: VOs (including both observations
and models)• Stronger efforts to measure/compute atomic data• Stronger efforts to use the newly available
atomic data• Full analysis automation• R – an ignored variable?
Carlos Allende PrietoIAC
Galactic Surveys
Other projects and analysis strategies
Overview
• eBOSS, BigBOSS (DESI), HETDEX, WEAVE, 4MOST
• Data mashup: astrometry, photometry, spectroscopy
• Observing Galaxy simulations• Discovery and followup of interesting
targets: HVS, UMPS, CEMPS, RCrBs…
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SDSS• BOSS (2009-2014): redshifts for 1.5 million
LRG to z=0.7 • eBOSS (2014-2020): extension to larger
redshifts using emission-line galaxies
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Kitt Peak 4-m (Mayall) at Kitt Peak, Arizona USA today...
Capable of • holding heavy corrector• 3 deg. field
Dec. 6, 2011 David Schlegel P1 Science Overview
10 spectrographs
Mayall with BigBOSS
Huge Volume of universe with 3-degree field5000 robotic fiber positioners10 spectrographs15 million spectra!
Key of BB Instrument: 5000 Spectra per pointing via Robot Positioners
• 5000 positioners put fiber at target position
positioner
Spectrograph
fibers
Focal Plane filled with positioners
focal surface
HET
HETDEX
DEX stars simulation from Besançon model
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spectra
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DEX stars analysis (KM stars)
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DEX stars analysis (FG stars)
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WEAVE
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WEAVE
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4MOST
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Data flow CCDs single exposure flow• BigBOSS 10x(1+4) 0.6 GB 0.0005
GB/s• HETDEX 75x2 0.8 GB 0.002
GB/s • Gaia 100 (2 GB) (0.1
GB/s)• LSST 200 6 GB 0.3
GB/s
LSST will take 30 TB/night and 100 PB in 10 years
Big data and the cloud• Trends are changing in observational
astronomy• Hand by hand, instrument development and
computing are creating a new generation of machines geared to speed up discovery
• The biggest telescopes are, at least partially, not following that trend
Big data and the cloud• Supercomputing is widely embraced for
modeling and interpreting the data (plain good-old physics)
• Virtual observatories are developing quickly to ensure the legacy value of the data
• High-throughput computing widely adopted for large-scale projects, but only modest use of ‘cloud’ services (e.g. HETDEX)
Data mashup• Typical use of data is concentrating on a
specialized data set• This must change now with projects such as
Gaia• Analysis requires combining appropriately
different types of data• Bayesian statistics offers the framework to a
combined analysis of astrometry, photometry and spectroscopy
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Observing simulations
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Observing simulations
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Rahimi et al. 2012
Observing simulations
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Discovery and follow-up of interesting targets• HVS• LMWD• CEMPS• RCrBs• UMPS
Image from J. Norris
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Structure of the halo• Monolithic collapse
and intensive accretion
• A dual halo split in rotation and [Fe/H]?
• Only place in the Galaxy where full orbits and chemistsry are preserved: ideal for stellar archaelogyJohnston & Bullock simulations
Chemical evolution• Big bang
nucleosynthesis• Stellar
nucleosynthesis: hydrostatic equilibrium, AGB
• Explosive nucleosynthesis• ISM spallation
• Also destruction…
Early Chemical Evolution
• Fast enrichment • Extremely few
stars expected (and found) at [Fe/H] < -4
• Large scatter in abundances at [Fe/H]<4
Big Bang Nucleosynthesis
Figure from Edward L. Wright
• Chemical abundances of the oldest stars constrain our model of the universe.
• Large discrepancy between CMB and stellar Li abundances
R-process is universal
Sneden et al. 2003
• Oldest stars provide pure information on single SN events
• Nucleosynthesis patterns then and now seem to match in cases
• The fraction of carbon-rich stars increases at low [Fe/H]
Abundance ratios
Chiappini et al. 2011Frebel 2010
Mg/Fe
Ca/Fe
Ti/Fe
Y/Ba
Only two stars currently known at [Fe/H]<-5!!
Discovery space• Preston/Shectman/Beer
s
• Hamburg-ESO survey (Christlieb+)
• SDSS (Yong et al. 2012, Bonifacio et al. 2012)
Apache Point ObservatoryNew Mexico, USA
BOSS spectra • More resolution
• More spectral coverage
• More sensitivity
• Deeeper into the halo
• Privileged access to IAC
• >100,000 spectra in hand!
BOSS analysis• SEGUE obtained >300,000 stellar spectraBetween 2008-2010• SEGUE’s pipelinecan be used to comparewith results from BOSS• New analysis for BOSS spectra represents asignificant improvement
Discovery process1. Skim through BOSS database to pick the
best candidates to have [Fe/H]<-42. Follow those up with higher quality: 4.2m
WHT/ISIS, 10m GTC/OSIRIS3. Investigate those that pass all the filters:
8m ESO/VLT, 10m GTC/OSIRIS, 10m HET/HRS (maybe HORUS)
GTC
HORUS
HORUS-P
HORUS-P
Led-ThAr hollow-cathode lamp
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Summary• Astrometry: Hipparcos, UCAC3 , Gaia• Photometry: 2MASS, UKIDSS, VHS, SDSS ,
PanSTARS, GALEX, WISE, LSST• Spectroscopy: Various SDSS low-resolution
surveys, LAMOST, ARGOS, APOGEE, RAVE, Gaia-ESO, GALAH, DESI, HETDEX, WEAVE, 4MOST, MOONS
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Summary II• Data indigestion?• Stress should be placed on automated
analysis• And on a rigurous analysis of combined data
(Bayesian framework)• Parametric models, increasingly
sophisticated, to become a workhorse. Are they Ready?
• Data can be directly used to determine distribution functions across the Galaxy to be directly compared with numerical simulations of all kinds to be directly compared
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Conclusions• We are living a golden era for the study of the
Milky Way• Gaia flies at the end of the year, first catalog
probably out around 2016 and final catalog around 2020
• Now is the time to get ready to use Gaia’s data, and in particular to squeeze the information content in the combination of Gaia plus the other spectroscopic surveys
• Now is the time to sharpen our tools for automatic analysis and model-based interpretation
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