EÖTVÖS UNIVERSITY BUDAPEST

Department of Physics of Complex Systems

Photometric parallax estimation using the MILES catalog and BaSeL models

Photometric parallax estimation using the MILES catalog and BaSeL models

István CsabaiLászló DobosMárton TrencsényiNorbert PurgerGéza Herczeg

István CsabaiLászló DobosMárton TrencsényiNorbert PurgerGéza Herczeg

GYÖNGYI KEREKES

MAGPOP MEETING, MALTA

April 20, 2023

GYÖNGYI KEREKES

MAGPOP MEETING, MALTA

April 20, 2023

PHOTOMETRIC PARALLAX

• Based on different distance measurements for stars:o Trigonometric parallax (nearest stars)o Main sequence fitting (open clusters)o Cepheid variable stars (globular clusters), etc.

• Calculation of absolute magnitudes• Color-magnitude diagram• Main sequence fitting with a function

• If we know the color index of a star, we can estimate the distance.

PHOTOMETRIC PARALLAX

Problems:• We can only estimate for main sequence stars• Color indices are metallicity-dependent (especially

B, V)• We need continuous parameters• Hawley, 2002

(spectroscopic parallax)

PHOTOMETRIC PARALLAX ESTIMATIONS

Juric et al, 2005 THE MILKY WAY TOMOGRAPHY WITH SDSS

OUR CONCEPTION

MILES DATABASE

• 985 stars • Wavelength range: 3525 – 7500 Å

at 2.3 Å spectral resolution• Atmospheric data estimated using CEN01b

(Teff, log g, [Fe/H])

MILES DATABASE

Teff vs log g

Large range of atmospheric parameters: from metal-rich, cool stars to hot, metal-poor stars.

Cenarro et al, 2006

HIPPARCOS

• Trigonometric parallax• About 130.000 stars• Error: 0.7-0.9 mas for stars brighter than

9 mag

MILES – HIPPARCOS CROSSMATCH

• Based on coordinates (40 arcsec) 614 stars

• HRD[V>10]

MILES – HIPPARCOS CROSSMATCH

• CMD

BASEL MODEL

• Used for fitting: 2 735 spectra• Method: least χ2 • Spectra fitted:

χ2=0.344

χ2=3.578

χ2=11.886

SPECTRA FITTING

• Cut at χ2 = 3• Result:

562 stars

SPECTRA FITTING

SYNTHETIC MAGNITUDES

• u’, g’, r’, i’, z’ (Sloan filters)

[Fukugita et al, 1996]

SYNTHETIC MAGNITUDES

Jester et al. 2005 filter transformation equations:

g=V+0.64(B-V)-0.13

r=V-0.46(B-V)+0.11

COLOR-COLOR DIAGRAMS

g – r vs r – i for 100 000 Sloan stars (red dots) and for MILES stars (green crosses)

r – i

g –

r

SDSS stars selection:

Relative error in magnitudes < 0.04%

Magnitudes in range [14;17]

Upper CCD from Michael Richmond

COLOR-COLOR DIAGRAMS

u-g vs g-r for 100 000 Sloan stars (red dots) and for MILES stars (green crosses)

OUR ESTIMATION

• We have code for nonparametric estimation (multidimensional indexing integrated with databases)

• It was created for photometric redshift calculation and estimation of physical parameters of galaxies

• This code can be adapted for photometric parallax estimation: 5-D (4 CI & M) spaces nearest neighbour searching absolute manitude & parallax estimation

FUTURE TASKS