Luminous and Dark Matter in Nearby Spiral Galaxies

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Luminous and Dark Matterin Nearby Spiral Galaxies
Roelof S. de Jong (STScI)
Susan Kassin (OSU) Eric Bell (MPIA) Stephane
Courteau (UBC)
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Overview

• Mass-to-light ratios of stellar populations
• Comparing dynamical and stellar population masses
• Rotation curve models
• Angular momentum

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Galaxy evolution models
Bell de Jong 2001
Closed box model
Mass dependent formation epoch model
Mass dependent formation epoch model with star
bursts
Even in K mass-to-light ratio varies by factor of
2
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Color-ML for hierarchical galaxy model

• Most galaxy formation models show a strong
  correlation between color and M/L

• Dust reddening has similar effect on M/L as
  populations

Cole et al. (2000) models
An optical color of a stellar population is a
good M/L indicator
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Different Initial Mass Functions

• The slope of the color-M/L relation is
  independent of models and IMFs used

• The normalization of the relation depends on the
  IMF used, i.e. the amount of low mass stars

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Maximum disk constraints

• The color-M/L relation must be normalized below
  all maximum disk values

• Salpeter IMF

• A Salpeter IMF is too massive

Salpeter light

• Bell de Jong (2001) adopt Salpeter 0.15 dex
  lower

data Verheijen (1997)
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Comparing dynamical and stellar pop M/L

• Constrain color-M/L relation offset relative to
  maximum disk normailzation Bell de Jong (2001)
• Assumptions made
• IMFs are universal
• Stellar population models accurate in relative
  sense
• HST Key project distance scale
• No selective loss of stellar populations
• Simple dust corrections

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Galactic Globular Clusters King model M/L

• King core M/L very low for SSP models
• Mass segregation (and Dark Matter?) cause radial
  M/L gradient

McLaughlin (2000)
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Galactic Globular Clusters Virial model M/L

• Virial (global) mass estimates agree better, but
  large scatter

Pryor Meylan (1993)
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Extra-Galactic Globular Clusters

• Errors on extra-galactic clusters even larger
• M33 cluster especially low

Martini Ho (2002)
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Elliptical Galaxies

• Stellar population modeling of line indices
• Schwarzschild kinematic modeling
• Slow rotators may have 30 dark matter within
  Reff (or different IMF)

Cappellari et al. (2005)
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Velocity dispersion disk galaxies

• Edge-on galaxies dynamical mass modeling from
  velocity dispersions

Bell de Jong (2001)
Baryonic TF from dynamical modeling
Kregel, van der Kruit Freeman (2005)
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Minimum Disk Rotation Curves
0.0 dex
-0.1 dex
-0.3 dex
Kassin de Jong (2005)

• Declining rotation curves of early type disk
  galaxies require concentrated mass

• Hard to interpret errorbars for tight constraint

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Bar Streaming Motions

• Gas shock across bar depends critically on M/L

Salpeter
Bell de Jong
Bell de Jong 0.1 dex
Weiner et al. (2003)
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Summary M/L comparisons

• Distance uncertainties still critical
• Especially for methods based on a few galaxies

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Rotation Curve Samples

• Broad range in properties
• Multi-band surface photometry
• Verheijen (1999) Ursa Major (BVRK, HI)
• Courteau sample (BVRH, Ha)
• OSU sample (BVRJHK, Ha, HI)
• Sloan DR1 (ugriz, Ha)
• Classical RC galaxies (UBVRJK, HI, Ha)
• More than 100 good RC galaxies

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Broad Range in Properties
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Rotation Curve Decompositions

• Use colors to derive M/L profile

• Calculate stellar mass profile

• Add the contribution from the gas

• Calculate rotation curves

B-K

• Subtraction gives dark matter rotation curve

I-K
B-R
Main advantage M/L scaling law between galaxies
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Average Dark Matter Rotation Curves
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Characteristic baryonic/dark profile
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Baryon/total mass

• ?(r) V 2 (r )/Vtot 2( r )
• ?1 gt rotation accounted for by baryons alone
• ?0 gt rotation accounted for by dark matter
  alone
• ?0.5 gt equal contribution from baryons and dark
  matter

• V,max gt 250 km/s thin solid line
• 201 lt V,max 250 dotted line
• 120 lt V,max 201 dashed line
• V,max 120 thick solid line

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Fitting NFW Dark Matter Halos

• Adiabatic contraction using known baryon
  distribution

• Central rotation curve in general over-predicted

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NFW Parameters and Expectations
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Conclusions

• There are measurable constraints on stellar M/L
  ratios
• The color-M/L relation should probably be
  normalized 0.1 dex lower than Bell de Jong
  (2001)
• Adiabatic contracted NFW profiles also
  over-predict rotation curves in HSB galaxies

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Minimum Disk Rotation Curves

• UGC9133

UGC9133
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Average Dark Matter Rotation Curves
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NFW Parameters Poorly Constrained
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The HI-Dark Matter Connection

• HI cannot consistently be scaled to produce dark
  matter

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Specific Angular Momentum Predictions
Models Bullock et al. (2001)

• Baryons are often assumed to keep specific
  angular momentum distribution during collapse

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Specific Angular Momentum
Models Bullock et al. (2001)
Similar results as Van den Bosch et al. (2001)
had for dwarfs
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Todo List

• Constrain zeropoint color-M/L relation
• Get Ha velocity fields for sizeable sample
• Complete the classical rotation curve sample
• Explore adiabatic contraction on small scales

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Future work Stellar Velocity Dispersions

• An isothermal disk yields

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Todo List

• Constrain zeropoint color-M/L relation
• Get Ha velocity fields for sizeable sample
• Complete the classical rotation curve sample
• Explore adiabatic contraction on small scales