Galactic Warp in the overdensity of the Canis Major (CMa) Region

1. Galactic Warp in the overdensity of the Canis Major (CMa) Region Martín López-Corredoira Instituto de Astrofísica de Canarias (Tenerife, Spain) Based on the paper accepted in MNRAS: astro-ph/0604239 IAC; 2006, June 20th

2. Stellar warp(+flare) in the Milky Way López-Corredoira et al. (2002): zw=CwRεwsin (Φ-Φw) – (15 pc) (valid for R<13 kpc) zw: height of disc over plane b=0 Cw: amplitude of the warp=1.2e-3 pc εw: exponent of the warp=5.25±0.50 Φw: galactocentric azimuth of warp line of nodes=-5o ± 5o R: galactocentric distance (kpc) Φ: galactocentric azimuth 2MASS data

3. All-sky 2MASS data Cabrera-Lavers (2005)

4. Gas warp in the Milky Way HI densities (Voskes 1999)

5. Gas warp maximum height: (Voskes 1999) Northern warp Φw=+5o Southern warp

6. Bump Bellazzini et al. (2006) López-Corredoira (2006) Extrapolation of southern warp for 13<R<16 kpc: constant height

7. Overdensity of red clump stars Bellazzini et al. (2006): 5o<|b|<15o López-Corredoira (2006) lmax=244o Φw=+5o lmax=248o Φw=-5o lmax=270o Model from López-Corredoira et al. (2002)

8. Color-magnitude diagram / depth WARP MODEL (López-Corredoira 2006): FWHM=2.2 mag (2.4 mag. including intrinsic broadening and latitude dispersion) CMa data: Martínez-Delgado et al. (2005): FWHM=1.6 mag FWHM[ρ(r)] ~ 4 kpc

9. Blue Plume: B5-A5 stars with <100 Myr in the Norma-Cygnus or Perseus spiral arms Blue plume Carraro et al. (2005): open squares  open clusters filled triangles  BP population Moitinho et al. (2006): open cluster NGC 2362, l=238.2o, b=-5.5o

10. Metallicity of CMa -0.4<[Fe/H]<-0.7 (Bellazzini et al. 2006) (as expected in the outer disc, at R=13 kpc)

11. Velocity of CMa stars - Radial velocities: distribution explained in terms of the Galactic rotation (Momany et al. 2006). • Tangential velocities perpendicular to the disc: * The selected stars might be contamination not associated with CMa (Momany et al. 2006) [blue plume]. * The expected warp signature is compatible with the negative vertical velocity (Momany et al. 2006) [7σ came from errors in distance determination of Hipparcos OB stars in Drimmel et al. (2000)]. • Unknown warp velocities: * They depend on the model of warp formation. * Asymmetries in the warp. Dinescu et al. (2005)

12. Conclusions: • Warp+flare can explain the excess of stars in the CMa region. • The depth of the CMa is roughly the expected one for the warped+flared Galaxy. • The Color-Magnitude diagram of CMa is explainable in terms of Galactic stars. • The metallicity and velocity of CMa stars is not incompatible with what is known from our Galaxy.