The photometric system onboard Gaia
The photometric system onboard Gaia
C. Jordi, J.M. Carrasco, F. Figueras, J. Torra,
X. Luri, E. Masana
University of Barcelona
JENAM 2004: The life of galaxies
Sept 14, 2004
(September-2004)
JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Goals of Gaia
Sept 14, 2004
JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Goals of Gaia
Sept 14, 2004
JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Goals of Gaia
Extragalactic objects: galaxies, supernovae, QSO, local group, etc
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JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Continous scan during 5 years
PHOTOMETRY
•
109 objects to Vlim~ 20 (unbiased)
•
Trigonometric parallax and annual proper motions accurate to
10µas at V=15
10% at 10 kpc
•
5-D phase space for over 109 objects
•
Radial velocity: 6-D phase space for over 300·106 objects
•
Age and chemical abundace: 2 additional dimensions
Sept 14, 2004
JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Continous scan during 5 years
•
109 objects to Vlim~ 20 (unbiased)
•
Trigonometric parallax and annual proper motions accurate to
10µas at V=15
10% at 10•All
kpcobjects to Vlim ~ 20
to cover a wide type of objects (even
•
5-D phase space for over 109 objects
unknown objects)
•
Radial velocity: 6-D phase space for over 300·106 objects
•
Age and chemical abundace: 2 additional dimensions
Sept 14, 2004
JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Continous scan during 5 years
•
109 objects to Vlim~ 20 (unbiased)
•
Trigonometric parallax and annual proper motions accurate to
10µas at V=15
10% at 10 kpc
Extension to galactic areas with systematic variation in atmospheric
and interstellar
abundances
•
5-D phase
space fornot
overinvestigated
109 objects at present
•
Radial velocity: 6-D phase space for over 300·106 objects
•
Age and chemical abundace: 2 additional dimensions
Sept 14, 2004
JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Continous scan during 5 years
•
109 objects to Vlim~ 20 (unbiased)
•
Trigonometric parallax and annual proper motions accurate to
10µas at V=15
10% at 10 kpc
Current photometric systems designed for specific types of objects
New photometric
system
•
5-D phase space
for overfor
109Gaia
objectsrequirements
•
Radial velocity: 6-D phase space for over 300·106 objects
•
Age and chemical abundace: 2 additional dimensions
Sept 14, 2004
JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Instrument description
• Two ASTRO telescopes
• One SPECTRO telescope
See poster by Carrasco et al
Sept 14, 2004
JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
ASTRO focal plane
Detection
Chromaticity
Astrophysics
AF1: Confirmation
AF1-AF11:
Astrometry
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JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
SPECTRO focal plane
Detection
Max. 16 bands (one of them: RVS)
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JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Gaia Photometry bands
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JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
G magnitude (white light)
• very broad band
• Glim~ 20
~ 300-1050 nm
Vlim~ 20-25
• the best S/N for variability detection
• small B.C.
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The photometric system onboard Gaia
• 82 observations
• 11 CCDs per obs.
V~20 equivalent to
Hipparcos V~9
Cepheids
LMC: 13.5 < V < 16.5
M31: 19.5 < V < 22.5
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JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Broad Band System: BBP
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The photometric system onboard Gaia
L. Lindegren
Current baseline: 5 bands
Under investigation
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The photometric system onboard Gaia
Medium Band System: MBP
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The photometric system onboard Gaia
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H2M
H3M
0.8
0.6
0.4
C. Bailer-Jones
0.2
Transmission
0
3F
0.8
CCD−Blue
CCD−Red
0.6
Univ. Barcelona
0.4 + Obs. Geneve
0.2
0
X2M
0.8
0.6
V. Vansevicius0.4et al
RVS
0.2
0
Sept 14, 2004
400
600
800
Wavelength (nm)
JENAM 2004:The life of galaxies
1000
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The photometric system onboard Gaia
1
H2M
H3M
0.8
0.6
0.4
C. Bailer-Jones
0.2
Transmission
0
3F
0.8
CCD−Blue
CCD−Red
0.6
Univ. Barcelona
0.4 + Obs. Geneve
0.2
Current baseline: 12 bands
0
X2M
0.8
0.6
V. Vansevicius0.4et al
RVS
0.2
0
Sept 14, 2004
400
600
800
Wavelength (nm)
JENAM 2004:The life of galaxies
1000
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The photometric system onboard Gaia
Continuum
MgH+Mgb
Balmer jump
Metallicity
Sept 14, 2004
JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Continuum
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JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
TiO
C RVS
Hα
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The photometric system onboard Gaia
Photometry performances
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JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Several steps ...
1. Definition of scientific targets for Gaia performances evaluation for the
quantitative description of chemical & dynamical evolution of the Galaxy
2. Galaxy model + 3D interestellar absorption model
Collaboration with J. Knude (Copenhagen Obs)
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The photometric system onboard Gaia
Several steps ...
∼ 6500 stars
Halo: [Fe/H] = -4.0, -3.0, -2.0, -1.5, -1.0
[α/Fe] = +0.2, +0.4
Bulge: [Fe/H] = -1.0, -0.5, +0.0, +0.5
[α/Fe] = +0.0, +0.4
Thick: [Fe/H] = -1.0, -0.5, +0.0
[α/Fe] = +0.2
Thin: [Fe/H] = -1.0, -0.5, +0.0, +0.5
[α/Fe] = -0.2, +0.0
Sept 14, 2004
JENAM 2004:The life of galaxies
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The photometric system onboard Gaia
Several steps ...
1. Definition of scientific targets for Gaia performances evaluation for the
quantitative description of chemical & dynamical evolution of the Galaxy
2. Galaxy model + 3D interestellar absorption model
Collaboration with J. Knude (Copenhagen Obs)
3. Simulated photometry (G, BBP, MBP) using BaSeL2.2 and NextGen
new release spectral libraries (a minimum photometric error of 0.003
mag have been assumed)
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The photometric system onboard Gaia
Sky background:
Interstellar absorption:
• AV, 3D model
• RV, A(λ) = AV · [A(λ) /
AV]
• zodiacal light (ecliptic
coordinates)
V = 22.5 mag/arcsec2, (G2 V)
• LMC, M31, nebulae, ...
Photo-electrons/s per band/CCD:
F = ∫ SED(λ)·10(- 0.4Aλ) ·Band(λ)·QE(λ)·T(λ)·S
dλ
B = ∫ Sky(λ)·Band(λ)·QE(λ)·T(λ)·S dλ
Modelling the object (spectra)
•"normal" star: Teff, log g,
[M/H], [α/Fe], [C/Fe], ...
• Peculiar stars, Solar System
objects, galaxies, QSO, ...
• Multiplicity
UB- Photometry
simulator
(http://gaia.am.ub.es/PWG/)
Magnitude zero point:
• Vega= Kurucz: Teff=9550K, log
g=3.95, [M/H]=-0.5
• Brightness (G, V)
• Doppler shift
Instrument model (ASTRO,
SPECTRO):
• Main mirror size, TDI
• Optical transmittance (λ)
• Vignetting
• PSF (λ)
• QE of CCD (+ number of CCDs)
• RON
• Filter transmission curves (λ)
• Sample and window sizes
Sept 14, 2004
Number of observations:
• Celestial coordinates +
Scanning law Æ Nobs end-ofmission
JENAM 2004:The life of galaxies
Magnitude error:
• synthetic aperture: Høg et al
(1999)
• PSF fitting
• calibration (+20%
contingency)
• per observation (variable stars)
• end-of-mission
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The photometric system onboard Gaia
Several steps ...
1. Definition of scientific targets for Gaia performances evaluation for
the quantitative description of chemical & dynamical evolution of the
Galaxy
2. Galaxy model + 3D interestellar absorption model
Collaboration with J. Knude (Copenhagen Obs)
3. Simulated photometry using BaSeL2.2 and NextGen new release
spectral libraries (a minimum photometric error of 0.003 mag have been
assumed)
4. G+BBP+MBP+parallax (and its error) (L.Lindegren, Lund Obs)
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The photometric system onboard Gaia
I - Perpendicular to galactic plane
0.1 0.3
0.3
0.3
Halo population:
Chemical galactocentric
distribution (G & K
giants)
AV
AGB / RGB
BHB, HB-A
FV, GV, KV, MV
GIII, KIII, RR-Lyr
AIV, FIV, GIV
AV, BV/III, OV/III
BIa, Cepheids, FIa, MIa
Disk & halo population:
Precision enough to
classify stars
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The photometric system onboard Gaia
I - Perpendicular to galactic plane
0.1 0.3
0.3
0.3
Halo population:
Chemical galactocentric
distribution (G & K
giants)
AV
AGB / RGB
BHB, HB-A
FV, GV, KV, MV
GIII, KIII, RR-Lyr
AIV, FIV, GIV
AV, BV/III, OV/III
BIa, Cepheids, FIa, MIa
RR-Lyrae (V~15.6)
σlogg ~0.07, σAv ~0.03
σMv ~0.15 mag
ƒ σ[M/H] ~ 0.1 at [M/H]=-2
ƒ σ[M/H] ~ 0.3 at [M/H]=-4
KIII at 30 kpc (V~17.5):
• σ[M/H] ~ 0.1 at [M/H]=-2
Disk & halo population:
• σ[M/H] ~ 0.3 at [M/H]=-4
Precision enough to
Outer halo &classify
halo stars
streams characterized
Sept 14, 2004
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The photometric system onboard Gaia
I - Perpendicular to galactic plane
0.1 0.3
0.3
0.3
Halo population:
Chemical galactocentric
distribution (G & K
giants)
AV
Halo
Age galact. gradient
(turn-off stars)
σage~1.5 Gyr at 2.5 kpc
σage~2.2 Gyr at 5 kpc
Chemical galact. gradient
(G & K giants)
σ[M/H] ~0.07 at 5 kpc
σ[M/H] ~0.15 at 12 kpc
σ[M/H] ~0.20 at 17 kpc
AGB / RGB
BHB, HB-A
FV, GV, KV, MV
GIII, KIII, RR-Lyr
AIV, FIV, GIV
AV, BV/III, OV/III
BIa, Cepheids, FIa, MIa
Disk & halo population:
Precision enough to
classify stars
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The photometric system onboard Gaia
II - Anticenter direction
0.3 0.7 1,4
3.5
AV
Chemical abundance
gradient
3.5
AGB / RGB
BHB, HB-A
FV, GV, KV, MV
GIII, KIII, RR-Lyr
AIV, FIV, GIV
AV, BV/III, OV/III
BIa, Cepheids, FIa, MIa
Large-scale structure
Disk & halo population:
Precision enough to
classify stars
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The photometric system onboard Gaia
III - Center direction
0.3 1
2
5
AV
8
Disk
Galactic center
Galactic anticenter
Age galact.
gradient
(turn-off stars)
σage~1.2 Gyr at 2 kpc
σage~4.7 Gyr at 3 kpc
σage~1.1 Gyr at 2 kpc
σage~2.6 Gyr at 3 kpc
Chemical
galact.
gradient
(G,K giants)
σ[M/H] ~0.05 at 2 kpc
σ[M/H] ~0.20 at 5 kpc
σ[M/H] ~0.05 at 2 kpc
σ[M/H] ~0.10 at 5 kpc
σ[M/H] ~0.15 at 8 kpc
Sept 14, 2004
JENAM 2004:The life of galaxies
AGB / RGB
BHB, HB-A
FV, GV, KV, MV
GIII, KIII, RR-Lyr
AIV, FIV, GIV
AV, BV/III, OV/III
BIa, Cepheids, FIa, MIa
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The photometric system onboard Gaia
III - Center direction
0.3 1
2
5
AV
8
Distance Scale
Cepheids: σπ/π < 10% for all observ.
σAv < 0.03 for all observ.
RR-Lyrae: σπ/π < 10%
up to 10 kpc in galactic pole direction
up to 5 kpc in the disk
σAv < 0.02 at 2kpc, 0.04 at 4 kpc.
Sept 14, 2004
JENAM 2004:The life of galaxies
AGB / RGB
BHB, HB-A
FV, GV, KV, MV
GIII, KIII, RR-Lyr
AIV, FIV, GIV
AV, BV/III, OV/III
BIa, Cepheids, FIa, MIa
σMv< 0.20
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The photometric system onboard Gaia
Conclusions & Future work
• The current photometric BBP & MBP systems baselines is
able to assure the scientific goals of the mission
• Optimization of the bands
• Investigation on [α/Fe] abundances determination
• emission line stars, peculiar stars, solar system objects,
QSOs, …
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The photometric system onboard Gaia
Teff=5500 K logg=4.0 [Fe/H]=-0.4
Teff=4500 K logg=3.0 [Fe/H]=-0.4
Filters of 80-100Å
CaII H-K, MgIb
σ[α/Fe]=0.1
giants V~17, dwarfs V~16
σ[α/Fe]=0.2
giants V~18, dwarfs V~16.5
Tautvaišienė & Edvardsson (2002)
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The photometric system onboard Gaia
Conclusions & Future work
The definitive photometric system for Gaia will be finally
decided in middle of 2005
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