Il ruolo della spettroscopia a grande campo per Gaia

B. Bucciarelli - INAF/Osservatorio Astronomico di Torino S. Randich - INAF /Osservatorio Astrofisico di Arcetri

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Gaia: Scientific Organisation

Gaia Science Team (GST): 8 members + ESA Project Scientist (T. Prusti)

Scientific community organised in Data Processing and Analysis Consortium (DPAC) ~ 391 scientists from ESA member States

Data distribution policy: final catalogue ~ 2019–20 intermediate catalogues as appropriate science alerts data released immediately no proprietary data rights

Strong involvement of Italian community:

•GST: S. Randich (Arcetri)•DPACE: R. Drimmel , Deputy (Torino)•DPAC: 63 scientists (as of July 08) CU3 deputy: M. Lattanzi (TO) CU5 Man. Team: C. Cacciari (BO)

Italian Participation in DPAC

Through ASI contract

INAF Institutes: OABo, OACt, OANa, OAPd, OARm, OATe, OATo (+ OATs)

Involvement in all main CUs.

Providing over 30 FTEs for more than 60 collaborators (second only to France)

Organization:

Lead Scientist (“Resp. Scient.”) M.G. Lattanzi

Coordination Group: Cacciari, Drimmel, A. Lanzafame, Pulone, Ripepi, Sarasso (project controller), Vallenari

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GAIA vs. Hipparcos

Hipparcos GAIA

Completeness ~ 9 G=20 (V=20-22)

Magnitude limit 12.4 ~ 1 mag fainter than compl.

N. sources 1.2 105 ~ 1.5 109

quasars 0 1 million

galaxies 0 10 million

Astrometric accuracy () (**) ~ 1 mas < 7 μas at V≤10

12-25 μas at V=15

(*) 100-300 μas at V=20

Photometry 2 bands low-res spectra 330-1050 nm

Radial velocities none 1-10 km/s to V=16-17

Target selection input catalogue real-time onboard selection

(*) ~ 0.5 mas accuracy from ACS/WFC (FoV 202x202 square arcsec) on well exposed images (Anderson & King 2006) (**) Proper motion accuracy 20% better

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Distances () as a function of V (Mv)

()/ Mv V d(pc)

< 0.1% 0 7 250 5 12 250 ~ 105 10 15 100 15 17 25

< 1% -5 7 2500 0 12 2500~ 107 5 15 1000 10 17 250 15 20 100

< 10% -5 12 25000 0 15 10000 ≥ 108 5 17 2500 10 20 1000

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Gaia products: photometry (V < 20)

Integrated: white-light (G-band, 330-1050 nm) from the Astrometric Field BP-band & RP-band BP- RP colour Dispersed:

Blue (BP, 330-680 nm) & Red (RP, 640-1050 nm) low resolution spectra

Main sequence stars from O5 to M6: G=15, AV=0.0 (Straizys et al. 2006)

dispersion 4-32 nm/px

dispersion 7-15 nm/px

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Spectrophotometry

RMS internal uncertainties at V = 15

Teff 1 – 5 % for a wide range of Teff log g 0.1 – 0.4 dex, < 0.1 dex for hot stars (SpT ≤ A) [Fe/H] < 0.2 dex for cool stars (SpT > F) down to -2.0 dex Av 0.05-0.1 mag for hot stars

► complete characterisation of stellar populations

Courtesy Coryn Bailer-Jones, C. Cacciari

Stellar astrophysical parameters (APs)

from BP/RP low res SEDs

via pattern recognition

calibration: input physics & synthetic spectra

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Radial Velocity Measurement Concept (2/2)

Radial velocities to 1-10 km/s for all sources down to V < 16–17

► radial velocitiy, rotation, chemistry► more detailed APs for V < 14

Field of view RVS spectrograph CCD detectors

Figures courtesy David Katz, C. cacciari

•Integral field spectrograph•Multi-epoch scan

•R=11,500•λ interval: 8470-8740 A

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GAIA science products: census of …

Stellar pops in the Galaxy

(based on the Besançon Galaxy model - Robin et al. 2003, 2004)

Disk: 9.0 x 108

Thick disk: 4.3 x 108

Spheroid: 2.1 x 107

Bulge: 1.7 x 108

Special objects in the Galaxy

Solar System bodies (~ 105)

extra-solar planets (~ 2 x 104 ) binaries & rare stellar types (fast evolutionary phases)

WDs (~ 2 x 105), BDs (~ 5 x 104)

Outside the Galaxy

brightest stars in nearby (LG) galaxies

supernovae and burst sources (~2x104)

galaxies (~ 107)

redshifts

QSOs (~ 106 )

gravitational lensing events: < 100 photometric; a few 102 astrometric

Fundamental Physics

to ~ 5x10-7 (10-4 - 10-5 present)

Why wide-field multi-object spectroscopy?

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1. RV for objects fainter than V=16-17: complement of Gaia core mission: critical!Discussion within GST

2. - More accurate abundance and AP; - Comprehensive characterization of targets in the Kepler and CoRoT fields

Requirements

1. R=R(Gaia) ideal, but R=5,000-8,000 ok

2. R > 20,000

CoRoT and Kepler Missions

• Ultra high-precision photometers observing pre-defined fields in the northern hemisphere

• Output: light curves for a few thousands objects in the magnitude range V~12-15 (transiting planets, eclipsing binaries, intrisically variable sources, etc).

• High-quality spectral coverage will complete the dataset for a comprehensive study of these targets