the metal-poor halo of the andromeda spiral galaxy jason kalirai (university of california at santa...
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![Page 1: The Metal-Poor Halo of the Andromeda Spiral Galaxy Jason Kalirai (University of California at Santa Cruz) Hubble Fellows Symposium, Baltimore MD April](https://reader038.vdocuments.mx/reader038/viewer/2022110210/56649e705503460f94b6df35/html5/thumbnails/1.jpg)
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
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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
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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:
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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
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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
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The Metal-Poor Halo of the Andromeda Spiral Galaxy
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
![Page 7: The Metal-Poor Halo of the Andromeda Spiral Galaxy Jason Kalirai (University of California at Santa Cruz) Hubble Fellows Symposium, Baltimore MD April](https://reader038.vdocuments.mx/reader038/viewer/2022110210/56649e705503460f94b6df35/html5/thumbnails/7.jpg)
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
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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
![Page 9: The Metal-Poor Halo of the Andromeda Spiral Galaxy Jason Kalirai (University of California at Santa Cruz) Hubble Fellows Symposium, Baltimore MD April](https://reader038.vdocuments.mx/reader038/viewer/2022110210/56649e705503460f94b6df35/html5/thumbnails/9.jpg)
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
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Outer Halo of Outer Halo of M31M31
160 kpc
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
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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
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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
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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
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The Metal-Poor Halo of the Andromeda Spiral Galaxy
Kalirai et al. (2006, ApJ, submitted)
Metallicity
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
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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)
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The Metal-Poor Halo of the Andromeda Spiral GalaxyChemical Composition
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
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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
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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!
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The Metal-Poor Halo of the Andromeda Spiral Galaxy
Hubble Fellows Symposium, Baltimore MD
April. 20th, 2006
![Page 20: The Metal-Poor Halo of the Andromeda Spiral Galaxy Jason Kalirai (University of California at Santa Cruz) Hubble Fellows Symposium, Baltimore MD April](https://reader038.vdocuments.mx/reader038/viewer/2022110210/56649e705503460f94b6df35/html5/thumbnails/20.jpg)
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
![Page 21: The Metal-Poor Halo of the Andromeda Spiral Galaxy Jason Kalirai (University of California at Santa Cruz) Hubble Fellows Symposium, Baltimore MD April](https://reader038.vdocuments.mx/reader038/viewer/2022110210/56649e705503460f94b6df35/html5/thumbnails/21.jpg)
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
![Page 22: The Metal-Poor Halo of the Andromeda Spiral Galaxy Jason Kalirai (University of California at Santa Cruz) Hubble Fellows Symposium, Baltimore MD April](https://reader038.vdocuments.mx/reader038/viewer/2022110210/56649e705503460f94b6df35/html5/thumbnails/22.jpg)
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
![Page 23: The Metal-Poor Halo of the Andromeda Spiral Galaxy Jason Kalirai (University of California at Santa Cruz) Hubble Fellows Symposium, Baltimore MD April](https://reader038.vdocuments.mx/reader038/viewer/2022110210/56649e705503460f94b6df35/html5/thumbnails/23.jpg)
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
![Page 24: The Metal-Poor Halo of the Andromeda Spiral Galaxy Jason Kalirai (University of California at Santa Cruz) Hubble Fellows Symposium, Baltimore MD April](https://reader038.vdocuments.mx/reader038/viewer/2022110210/56649e705503460f94b6df35/html5/thumbnails/24.jpg)
The Metal-Poor Halo of the Andromeda Spiral Galaxy
Kalirai et al. (2006, ApJ, submitted) Hubble Fellows Symposium, Baltimore
MDApril. 20th, 2006
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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