Simulations of the Gaia final catalogue: expectation of the distance estimation E. Masana, Y. Isasi, R. Borrachero, X. Luri Universitat de Barcelona GAIA DPAC - CU2
Introduction Gaia DPAC (Data Processing and Analysis Consortium) has developed 3 data generators to simulate the data provided by the mission: Gaia Simulator GaiaSimu library Universe Model Intrument Model Common Tools GASS GIBIS GOG Simulated telemetry Simulated images Simulated MDB data
Gog: Gaia Object Generator Gog is a tool designed to simulate catalogue data and main database data (including mission final data) for the Gaia satellite Gog uses a model of the Gaia instruments to generate the data: - Optical model (PSFs, transmitivity, ) - Focal plane model (CCDs, electronics, ) - Instrumental errors (radiation damage, read-out-noise, ) - Calibration errors -
Gog: Gaia Object Generator Parallax final accuracy: m: contingency margin g π = 1.47 / sin ξ a geometrical factor (ξ solar aspect angle) σ η : centroid error (function of G) σ cal : calibration error N eff : number of elementary CCD transits N transits : number of field of view transits
Gog: Gaia Object Generator Example of parallax final accuracy (mas)
Gog: Gaia Object Generator Photometry final accuracy: m: contingency margin σ pj : single CCD transit photometry error (function of G) σ cal : calibration error N eff : number of elementary CCD transits
Gog: Gaia Object Generator Example of photometry final accuracy:
The Universe Model All the data generated by Gog is based on an Universe Model that provides the astronomical sources to be observed by Gaia (position, velocity, magnitude and physical parameters) It has different components: Stars in the Milky Way, including multiple systems and variables Based on Besançon Galaxy Model (Robin et al. 2003) + 3D extinction model (Drimmel 2002) several populations: thin/thick disk, spheroid and bulge LMC/SMC Extragalactic objects (QSO, unresolved galaxies) Solar System Objects Exoplanets
The Universe Model The Universe Model Solar System Our Galaxy Extragalactic objects Sun, Earth, Moon Planets and satellites Minor bodies (not for observation) Asteroids Comets Kuiper belt Other components Zodiacal light Solar wind Etc. Field stars Normal Multiple systems Variable stars Stellar clusters Open clusters Globular clusters OB associations Stellar streams Extended objects Planetary nebula HII regions Reflection nebula Other components Galactic diffuse light Unresolved background stars Extrasolar planets Galaxies with resolved structure Galaxies with unresolved structure QSO Field stars Stellar clusters Surface brightness Supernovae Surface brightness Supernovae Other components Diffuse extragalactic light (List)
The Universe Model Sky density distribution: Milky Way stars + LMC + SMC (G<20)
The Universe Model Sky density distribution:thin Disk (G<20)
The Universe Model Sky density distribution: Thick Disk (G<20)
The Universe Model Sky density distribution: Spheroid (G<20)
The Universe Model Sky density distribution: Bulge (G<20)
Milky Way(G<20) The Universe Model Spatial distribution: Galactic XY plane
Milky Way(G<20) The Universe Model Spatial distribution: Galactic XZ plane
The Universe Model Milky Way HR diagram (G<20)
- σπ/π distribution - All the stars Astrometry: Error distribution 0.0 0.25 0.50
- σπ/π distribution - All the stars Astrometry: Error distribution σπ/π ~ 0.6% 0.0 0.05 0.10
Astrometry: Error distribution - σπ/π distribution - Cepheids 300 0 0.0 0.25 0.50
Astrometry: Error distribution - σπ/π distribution - Cepheids 500 0 0.0 0.05 0.10
Large Magellanic Cloud - Based on catalogues of stars known to be part of the LMC with their characteristics obtained from surveys. 7 500 000 stars. - Mean distance fixed to 48 Kpc (π = 20.8 µas) - Depth along the line of sight = 3 Kpc (Sakai et al. 2000); - Simulated using a Gaussian distribution around the mean distance. - σdist = 0.75 Kpc 3 Kpc 48-2σ 48 48+2σ
Large Magellanic Cloud Simulated distances distribution N (relative fraction)
Large Magellanic Cloud σπ distribution in µas (GAIA simulated final data) - σπ/π ~ 1300% N (relative fraction) σπ/π ~ 1300%
Large Magellanic Cloud Observed parallax distribution (GAIA simulated data) Mean parallax ~ 20.8 µas σπ/π = 0.5% N (relative fraction)
Summary - Gog is a tool that allows to obtain catalogue data and main database data (including mission final data) for the Gaia satellite, including errors. - It can be used to study the accuracy of the final photometry and distance determination for any subset of stars (stellar populations, LMC, SMC, individual stars, L-P Cepheids relation, ) - Work is on going to improve the error models. - We plan to generate a full statistical analysis of the expected contents of the Gaia catalogue based on Gog simulations.