GALAXIA – synthetic Galaxy model and its application to Kepler

GALAXIA – synthetic Galaxy model and its application to Kepler

Joss Bland-Hawthorn

Sanjib Sharma

KASC 6 Meeting

Sydney, June 2013

Joss Bland-Hawthorn

Sanjib Sharma

KASC 6 Meeting

Sydney, June 2013

A publicly available fast code: http://galaxia.sourceforge.net

ContextContextFar-field cosmologists have a "concordance model" for cleaning and comparing redshift surveys (W(α,δ); completeness; sampling; bias…)

In the near field, we are far from a chemically and dynamically consistent Galactic model. But a framework for comparing surveys, analytic and N-body models is essential.

To test a hypothesis, we must understand:

1.Our selection function2.Consequences of our selection function3.Uncertainties from statistical realizations

M. IrelandFriday talk

A publicly available fast code: http://galaxia.sourceforge.net

In the good old days, it was easy to present complex codes

In the good old days, it was easy to present complex codes

Sampling Analytical Model(Von Neumann rejection sampling)

Sampling Analytical Model(Von Neumann rejection sampling)

Adaptive Mesh (Barnes Hut Tree)Adaptive Mesh (Barnes Hut Tree)

Galaxia is efficient overarbitrarily large solid angles

Galaxia summaryGalaxia summary

• Analytical model for disc system + bulge + warp– Robin et al 2003 (Besancon model)

• Stellar halo simulated using N-body simulations– Bullock & Johnston 2005

• Padova Isochrones – m >0.15 , Marigo et al 2008, Bertilli et al 1994– 0.07<m<0.15 Chabrier et al 2000

• 3D extinction model – double exponential disc with warp and flare, hR=4.4 kpc, hz=0.088 kpc

– E(B-V) at infinity match Schlegel et al 1998 or

– 0.54 mag/kpc in solar neighborhood

• Analytical model for disc system + bulge + warp– Robin et al 2003 (Besancon model)

• Stellar halo simulated using N-body simulations– Bullock & Johnston 2005

• Padova Isochrones – m >0.15 , Marigo et al 2008, Bertilli et al 1994– 0.07<m<0.15 Chabrier et al 2000

• 3D extinction model – double exponential disc with warp and flare, hR=4.4 kpc, hz=0.088 kpc

– E(B-V) at infinity match Schlegel et al 1998 or

– 0.54 mag/kpc in solar neighborhood

HipparcosHipparcos• V<8, r<100 pc

• Difference in total number of stars, due to binarity (27%)

• V<8, r<100 pc

• Difference in total number of stars, due to binarity (27%)

MCMC fittingMCMC fitting Now we want extract new insight from a given survey.

Given a model (e.g. Galaxia), we can fit a large set of fundamental parameters to explain the observations.

We need new optimized MCMC methods to fit N model parameters with M missing data variables (marginalization) to 250,000 RAVE and 5000 GCS stars.

In the example that follows, we want to fine tune Galaxy kinematic parameters and test Gaussian DF vs. more theoretically sound DFs (e.g. Shu 1969).

Now we want extract new insight from a given survey.

Given a model (e.g. Galaxia), we can fit a large set of fundamental parameters to explain the observations.

We need new optimized MCMC methods to fit N model parameters with M missing data variables (marginalization) to 250,000 RAVE and 5000 GCS stars.

In the example that follows, we want to fine tune Galaxy kinematic parameters and test Gaussian DF vs. more theoretically sound DFs (e.g. Shu 1969).

DustDisk

Disk warp

Shu 1969

DF & asymmetric drift

GCS-SHU

RAVE-SHU

G. Ricker, Friday talk:

FGK dwarfs: V=4.5-13.5M dwarfs: I < 13

All sky: 2,500,000 targetsLaunch: 2018

GalaxiaGalaxia

A consistent framework is essential to progress

Results for the Kepler sample in the next talk

Powerful N-body phase space sampling and comparison not shown. In an era of Gaia, we can start to separate Galactic stars from “extragalactic stars.”

A consistent framework is essential to progress

Results for the Kepler sample in the next talk

Powerful N-body phase space sampling and comparison not shown. In an era of Gaia, we can start to separate Galactic stars from “extragalactic stars.”