The Inner Milky Way Structure with VVV. Marina Rejkuba ESO, Germany

Transcription

1 The Inner Milky Way Structure with VVV Marina Rejkuba ESO, Germany

2 Overview Red Clump stars as distance indicators Dependence on age and metallicity Tracing the bar with RC stars in VVV Inner bar flafening and the bar orientagon The structure behind the bar Based on work published in: Gonzalez, O., et al., 2011, A&A 534, A3 Gonzalez, O., et al., 2011, A&A LeF 534, L14

3 V Catelan 2009 B- V

4 our four target galaxies. The relatively large number of clump stars found in our four fields in Fornax (see Table lowed us to derive their mean K-band magnitudes indially for each field in this galaxy. We did this by selecting stars with K-band magnitudes in the range from 18.3 to mag and J!K colors in the range from 0.3 to 0.85 mag function (1) to the histograms of the K and J magnitudes of red clump stars from the combined data are displayed in Figure 2. The corresponding results of hki = & and hji = & were finally adopted as the mean K- and J-band apparent magnitudes of red clump stars in the Fornax dwarf galaxy. Red Clump in nearby galaxies in near- IR Gonzalez et al.: bulge reddening maps and metallicity gradients VVV Gle b278 3 Fig. 2. J,H and Ks magnitudes differences between VVV catalogs and 2MASS for stars. Dashed horizontal lines show the mean difference between both catalogs in the range denoted by the solid vertical lines Gonzalez t atile l. 2b Fig. 3. Final observed (J-Ks,Ks) CMD forethe once calibrated and completed with 2MASS photometry. range 13>Kvvv >12 for all three bands were used as zero points to be applied to the magnitudes in the VVV catalogs in order to obtain photometry fully consistent with 2MASS. The Data magpietrzynski, ieren UFornax. dalski 2have 003 g. 1. K, J!K near-infrared color-magnitude diagrams for the LMC, G SMC, Carina,& and been combined from the different fields nitude range used for the calibration is based on the fact that ved in each galaxy (see Table 1). 2MASS photometry is very accurate for our purpose down to a magnitude of K2mass 13 and therefore this range ensures that

5 Distance determinagon: recipe 1. ExGncGon correcgon select the reddening law Nishiyama et al. 2009: A K = * [(J- Ks) 0 (J- Ks)] Mean intrinsic color for RC in Baade s Window (J- Ks) 0 = Make a luminosity funcgon and fit it with a 2 nd order polynomial (underlying RGB) + a Gaussian (RC) N(K s0 ) = a + bk s0 + ck 2 s 0 + N RC σ RC 2π exp 3. The peak of the Gaussian is the m(rc) 4. Distance modulus: (m M) 0,target = m RC Κ M RC Κ A Κ [ (K RC s0 K s0 ) 2 2σ 2 RC The results of the Gaussian fits for each RC are lis M Κ RC RC zero point ΔM Κ RC populagon correcgon with respect to populagon used to establish the zero point M λ RC ]

6 Red Clump magnitude variagon as a funcgon of longitude at b=+1, - 1 deg Stars are closer to us at posigve longitude Tile b313 l=-9.3 Tile b317 l=-3.4 Tile b341 l=-9.3 Tile b345 l=-3.4 Tile b320 l=+1.0 Tile b348 l=+1.0 Tile b322 l=+3.9 Tile b350 l=+3.9 Tile b326 l=+9.7 Tile b354 l=+9.7 Gonzalez et al. 2011, A&A LeF

7 K- band RC magnitude Alves 2000; Alves et al MASS & CIO + Hipparcos (Solar Neighb.) Grocholski & Sarajedini 2002 WIYN Open clusters Pietrzynski et al LMC, SMC, Fornax, Carina (Araucaria project) Salaris & Girardi 2002 populagon effects (theoregcal) Percival & Salaris 2003 populagon effects (empirical + models) Laney et al SAAO + Hipparcos (Solar Neighbourhood) Oscar s Bulge metallicity map Percival & Salaris 2003 b l M K = (solar metallicity, 10 Gyr old isochrone: Pietrinferni et al. 2004)

8 From RC distances to structure Gonzalez et al. 2011, A&A LeF

9 Inner bar flafening Model: MarGnez- Valpuesta & Gerhard 2011 Gerhard & MarGnez- Valpuesta 2012

10 And below the plane At b=- 5, ~750 pc below the plane the bar flafens much less Gerhard & MarGnez- Valpuesta 2012 Gonzalez et al. 2012, submifed

11 K=14 Second clump Tile b313 l=-9.3 Tile b341 l=-9.3 Tile b317 l=-3.4 Tile b345 l=-3.4 Tile b320 l=+1.0 Tile b348 l=+1.0 Tile b322 l=+3.9 Tile b350 l=+3.9 Tile b326 l=+9.7 Tile b354 l=+9.7 Y (kpc) K= kpc 3 kpc 2 kpc 1 kpc K=13 K=12.5 K=12 K=11 X (kpc) K=11.5

12 SGll some head scratching l=+10 l= Tile: b255 l = 8, b=- 6.5 Second clump ~2.5 kpc behind the bar and ~ 1kpc below the plane! l=+1 l= Ks l=- 4 l= Residual Ks

13 Summary VVV depth and resolugon provides ideal dataset for inner Bulge structure studies RC, eclipsing binaries, RR Lyr à tracing different components? Complexity: patchy exgncgon (BEAM calculator) Mix of populagons bar/bulge, thin disk and spiral arms, thick disk? Comparison with models