the metal-poor halo of the andromeda spiral galaxy jason kalirai (university of california at santa...
TRANSCRIPT
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Jason Kalirai (University of California at Santa Cruz)
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The M31 Team:
UCSC - Raja Guhathakurta, Karrie Gilbert & Carynn Luine
U. Virginia - Steve Majewski, Jamie Ostheimer, & Ricky Patterson
UCLA - Michael Rich & David Reitzel
UC Berkeley - Michael Cooper
Carnegie Obs. - Marla Geha
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Outline:
1.) Recap The disparity between M31’s halo and the Milky Way halo. Predictions from simulations of galaxy formation.
2.) A New Synergistic SurveyDeep, wide field imaging.Keck/DEIMOS spectroscopy.Ultra-deep HST/ACS imaging.
3.) First ResultsClean detection of M31 RGB stars at R > 150 kpc (Gilbert et al. 2006).Surface Brightness: Bulge vs halo of M31 (Guhathakurta et al. 2006).
4.) Metallicity Distribution FunctionsBulge vs Halo[/Fe]
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral GalaxyBackground - Milky Way vs M31
Properties of Milky Way Halo: Age - old, 12 Gyr Chemical composition - metal poor, [Fe/H] = -1.5 Surface brightness profile - power law, R-2
Properties of M31 Halo: Age - both intermediate age and old populations, 6-12 Gyr Chemical composition - metal rich, [Fe/H] = -0.5 Surface brightness profile - de Vaucouleurs, R1/4
Brown et al. (2003)
Durrell, Harris, & Pritchet (2004)Durrell, Harris, & Pritchet (2001)Bellazzini et al. (2003)
Pritchet & van den Bergh (1994)
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
Bulge:
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Simulations of Halo Formation
Bullock & Johnston (2004)
Predictions:
1.) Substructure in halo. 2.) Chemically distinct outer halo.
Observational Requirements:
1.) Spatial coverage. 2.) Chemical distribution. 3.) Ages.
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral Galaxy
M31 Data Sets
Deep, Wide-Field Imaging: 1.) CFHT / MegaCam 2.) Kitt Peak / Mosaic DDO51 3.) Subaru / SuprimeCam
Spectroscopy: 1.) Keck / DEIMOS (also LRIS) 2.) Gemini / GMOS
Ultra-Deep, High Resolution Imaging: 1.) HST / ACS (also WFPC2)
Faint RGB LF, HB[Fe/H]phot
Sub-structure (starcount maps)
Kinematics[Fe/H]spec
Elimination of foreground dwarfs
AgesHB morphology
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral GalaxyM31 Data Sets
Spectroscopy: 1.) Keck / DEIMOS (also LRIS) 2.) Gemini / GMOS
Kinematics[Fe/H]spec
Elimination of foreground dwarfs
Kalirai et al. (2006, ApJ, submitted) Hubble Fellows Symposium, Baltimore
MDApril. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral Galaxy
M31 star-count map (Ferguson et al. 2002)
Kalirai et al. (2006, ApJ, submitted)
M31 Data Sets
Spectroscopy: 1.) Keck / DEIMOS (also LRIS) 2.) Gemini / GMOS
Kinematics[Fe/H]spec
Elimination of foreground dwarfs
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral GalaxyIsolating a clean sample of M31 RGB stars
Use probability distribution functions based on 5 photometric/spectroscopic diagnostics to eliminate foreground Milky Way dwarfs.
1.) Radial Velocity 2.)DDO51 photometry 3.) Na I equivalent width 4.) Position in the CMD 5.) [Fe/H]phot vs [Fe/H]spec
Gilbert et al. (2006, in prep.)
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
Outer Halo of Outer Halo of M31M31
160 kpc
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral GalaxySurface Brightness
Star-counts in outer fields (R > 60 kpc) well above extrapolation of R1/4 inner spheroid.Best fit: power law R-2.3 halo.
Guhathakurta et al. (2006, Nature, submitted) Hubble Fellows Symposium, Baltimore
MDApril. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Kalirai et al. (2006, ApJ, submitted)
Chemical Composition
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Kalirai et al. (2006, ApJ, submitted)
Chemical Composition
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Kalirai et al. (2006, ApJ, submitted)
Metallicity
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Kalirai et al. (2006, ApJ, in prep.)
Metallicity
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
Kalirai et al. (2006, ApJ, submitted)
The Metal-Poor Halo of the Andromeda Spiral GalaxyChemical Composition
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Conclusions
Discovered M31 RGB stars at R = 12-160 kpc using Keck/DEIMOS.
Surface brightness of stars with R > 30 kpc follows an R-2 power law profile: distinct from inner spheroid.
Chemical abundance of outer halo is distinct from inner spheroid. R < 20 kpc [Fe/H] = -0.47 0.03 ( = 0.39) R ~ 30 kpc [Fe/H] = -0.94 0.06 ( = 0.60) R > 60 kpc [Fe/H] = -1.26 0.10 ( = 0.72)
[Fe/H]spec = -1.24 0.12 ( = 0.85) [Fe/H]phot = -1.48 0.11 ( = 0.73) [/Fe] = +0.3
Future observations - improve statistics in halo and characterize shape.
M31 Image from GALEXM31 Image from GALEX Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral Galaxy
M31 Image from GALEXM31 Image from GALEXFeb. 7th, 2006 Local Group Cosmology, Aspen CO
Actual Size of M31!
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral GalaxyM31 Data Sets
Deep, Wide-Field Imaging: 1.) CFHT / MegaCam 2.) Kitt Peak / Mosaic DDO51 3.) Subaru / SuprimeCam
Faint RGB LF, HB[Fe/H]phot
Sub-structure (starcount maps)
M31 star-count map (Ferguson et al. 2002)Hubble Fellows Symposium, Baltimore
MDApril. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral GalaxyM31 Data Sets
Deep, Wide-Field Imaging: 1.) CFHT / MegaCam 2.) Kitt Peak / Mosaic DDO51 3.) Subaru / SuprimeCam
Faint RGB LF, HB[Fe/H]phot
Sub-structure (starcount maps)
M31 star-count map (Ferguson et al. 2002)Kalirai et al. 2006, in prepHubble Fellows Symposium, Baltimore
MDApril. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral GalaxyM31 Data Sets
Deep, Wide-Field Imaging: 1.) CFHT / MegaCam 2.) Kitt Peak / Mosaic DDO51 3.) Subaru / SuprimeCam
Faint RGB LF, HB[Fe/H]phot
Sub-structure (starcount maps)
M31 star-count map (Ferguson et al. 2002)Hubble Fellows Symposium, Baltimore
MDApril. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral GalaxyM31 Data Sets
Ultra-Deep, High Resolution Imaging: 1.) HST / ACS (also WFPC2)
AgesHB morphology
Brown et al. (2003) Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Kalirai et al. (2006, ApJ, submitted) Hubble Fellows Symposium, Baltimore
MDApril. 20th, 2006
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Simulations of Halo Formation
Mouhcine et al. (2006)
Predictions:
1.) Substructure in halo.
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006