Dwarf Galaxies in Local Group Environments

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Dwarf Galaxies in (Local) Group Environments

• Marla Geha
• Carnegie Observatories (OCIW)

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Dwarf Galaxy Flavors
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Local Group Dwarf Galaxies
Log (M/LV) Total
MV

• 38 Local Group dwarfs

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Local Group Dwarf Galaxies
Log (M/LV) Total
MV
5

• Local Group

38 dwarf galaxies
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The Dwarf Satellite Problem
Too many small halos in low galaxy density
environments.

• Bullock, Kravtsov Weinberg (2000)

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The Dwarf Satellite Problem (cont.)
Radial distribution of CMD satellites less
compact.

• Kravtsov, Gnedin Klypin (2004)

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Low mass DM halos exist, but...
Low mass DM halos dont exist because...
- Warm or interacting dark matter.
(Spergel Steinhardt 2000) - Truncated
primordial power spectrum or n1.
(Bullock Zentner 2003)
- Only halos which accrete gas before
reionization are luminous.
(Bullock et al. 2000) - Dwarf actually live in
big halos (vobs vDM). (Stoehr et al.
2003, but Kazantzidis et al. 2004
disagree) - Luminous small halos used to be
more massive. (Kravtsov, Gnedin Klypin
2004)
... but inconsistent w/constraints from lensing
substucture?
Need comparisons to other environments similar to
MW!
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Spatial Distribution of Nearby SDSS Groups
Groups with 4 to 10 members Mr lt -17.2 between
0.01lt z lt 0.03.
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The Sloan and Las Campanas Kinematics and
Environment Redshift Survey
M. Blanton, A. Berlind (NYU)

• Goal
• Establish group membership for galaxies down to
  Mr lt -15
• in large sample of low density
• groups.

SDSS r-band image 45 1Mpc _at_ 5000km/s
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The Sloan and Las Campanas Kinematics and
Environment Redshift Survey
M. Blanton, A. Berlind (NYU)

• Goal
• Establish group membership for galaxies down to
  Mr lt -15
• in large sample of low density
• groups.

SDSS r-band image 45 1Mpc _at_ 5000km/s
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SDSS Group Catalog

• Group catalog by A. Berlind. Galaxy members down
  to
• Mr lt -17.2.
• Follow-up for groups with
• 4 members.

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SDSS Group Catalog

• Group catalog by A. Berlind. Galaxy members down
  to
• Mr lt -17.2.

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Local Group
Groups with 4 to 10 members Mr lt -17.2 between
0.01lt z lt 0.03.

• Expect 7 additional
• dwarfs in 1 sq deg
• for group _at_ 5000 km/s

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Preliminary Results
Color distribution
Multislit spectroscopy Las Campanas
100inch WFCCD (FOV 25x18) Target
selection mr 19.5 (g-r) lt
1.0 February 2004 10 groups observed
56 dwarf members found 10 observing
efficiency

• (g - r)

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Radial Distribution of Satellites
MW satellites
slacker sources
LG satellites
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Stay tuned for more results from SLaCKERS...

• Ç??

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Build-up of Galactic Halos?

• Johnston Bullock

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Evidence for Interactions in M31

• Ferguson et al. (2002)

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Evidence for Interactions in M31

• Ferguson et al. (2002)

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Evidence for Interactions in M31
Mconnachie et al. (2004)

• Ferguson et al. (2002)
• Ferguson et al. (2002)
• McConnachie et al. (2004)
• Ferguson et al. (2002)
• Ferguson et al. (2002)
• Ferguson et al. (2002)
• Ferguson et al. (2002)

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A Dwarf Galaxy in the Local Group NGC 205

• NGC 205 is a dE satellite of
• M31. Provides detailed view
• of a disrupting satellite.

Constrain interaction via kinematics of
individual stars.
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NGC 205 Observations
P. Guhathakuta, G. Laughlin (UCSC)

• Integrated light spectra cannont probe beyond
  effective radius
• Targeted individual RGB stars

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NGC 205 CMD

• Keck/DEIMOS observations
• Radial velocities for 731 RGB stars.
• Ca II triplet region.

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Keck/DEIMOS Observations
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NGC 205 Major-axis Velocity Profile
Inner rotation 15 km s-1
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NGC 205 Major-axis Velocity Profile
Inner rotation 15 km s-1
Velocity turns over beyond 2.5 r_eff.
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(No Transcript)
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Orbital Simulations

• Restricted three-body models
• Mass ratio 201
• Fit to photometry and velocity data
• Bound orbits only
• Genetic algorithm

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Orbital Simulations
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Orbital Simulations
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Orbital Simulations
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Preliminary Results
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Summary
NGC 205 -- Confirm inner rotation velocity
of 15 km/s. -- Tidally disturbed region has
velocities opposite that of main body.
-- Constraints on orbit of NGC 205.
SLaCKERS -- Survey of dwarf galaxy population
(Mv lt -15) in low density SDSS
groups.