Do planetary nebulae indicate a lack of dark matter in elliptical galaxies?

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

Do planetary nebulae indicate Do planetary nebulae indicate a a lack of dark matterlack of dark matter in elliptical galaxies?in elliptical galaxies?

with

Avishai DEKEL (HU, Jerusalem), Felix STOEHR (IAP, Paris),TJ COX (Harvard), Greg NOVAK & Joel PRIMACK (UC Santa Cruz)Nature, accepted, astro-ph/0501622

Are PNe in ellipticals Are PNe in ellipticals youngyoung??

and

Ewa ŁOKAS (CAMK, Warsaw)MNRAS, submitted, astro-ph/0405491

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

Planetary Nebulae: Tracers at 1-3RPlanetary Nebulae: Tracers at 1-3Reffeff

N3379

[OIII]

5007 A

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

PN velocity dispersions are lowPN velocity dispersions are low

Mendez et al. 01

N4697

Romanowsky et al. 03

DM

DM

DM

no DM

no DM

no DM

are Ellipticals naked?

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

critical density Universe

universal M/L=387

log L/Lsun

log

(M/L

)/(M/L

sun)

Marinoni & Hudson 02

Predicted & observed M/LPredicted & observed M/L

Romanowsky et al 033

M/L = 33?

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

1) Do ellipticals have normal 1) Do ellipticals have normal contents of dark matter?contents of dark matter?

ellipticals thought to be formed by mergers, mainly of spirals Toomre 77

Mamon 92, 00; Helsdon & Ponman 03Springel et al. 01; Lanzoni et al. 05

spirals have dark matter halos Sofue & Rubin 02

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

Simulations of Simulations of major mergers of spiral galaxiesmajor mergers of spiral galaxies embedded in dark matter halos embedded in dark matter halos

Cox 04, PhD thesis

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

Velocity dispersionsVelocity dispersions

no DM (R03)

with DM (R03)

DM

all starsyoung stars

Dekel et al 05

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

2) What causes this discrepancy2) What causes this discrepancybetween between

kinematical & dynamical modelling?kinematical & dynamical modelling?

kinematical modelling no dark matter

dynamical modelling normal dark matter

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

Dekel et al. 05, Nature in press

€

d νσ r2

( )

dr+ 2β

rνσ r

2 = −νGM

r2= −ν

v circ2

rJeans eq.

€

ρtracer ∝ r−α

ρ total ∝ r−η ⇒ σ r ∝ vcirc ∝ r

1−η / 2

Power-law solutions to Jeans Power-law solutions to Jeans equationsequations

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

= tracer density slope

= dark matter density slope

realistic outer slopes: + > 5

or los

Power-law solutions to Jeans equations Power-law solutions to Jeans equations (2)(2)

velocity anisotropy tracer density slope

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

@ 5 Re

@ 2 Re

isotropic NFW

anisotropic Navarro

+04isotropic Navarro

+04

€

los(5Re )∝ Υ(rvir )[ ]1/ 8

Mamon & Łokas 05b, MNRAS subm

€

Υ(rvir )∝ σ los(5Re )[ ]8

Velocity dispersion vs Velocity dispersion vs anisotropy & dark halo modelanisotropy & dark halo model

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

Mamon & Łokas 05b, MNRAS submitted

Effects on M/L at virial radiusEffects on M/L at virial radius

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

3D profiles from merger simulations3D profiles from merger simulations

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

€

MJeans(r) =r vr

2

Gα + γ − 2β( )

€

γ=−d ln v r

2

d ln r

out of equilibrium!

mass underestimatedby ≈ 40%

Out of Jeans equilibrium?Out of Jeans equilibrium?

non-stationarity?

non-sphericity

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

Effects of Effects of triaxialitytriaxiality

face-onedge-on

edge-onface-on

What M/Ls were found by Romanowsky et al. 03?

Published M/L

Mamon & Łokas 05b, MNRAS submitted

fbary > b/ m

best

conc

entra

tion

para

met

ers

3) Are observed PNe in ellipticals

young?

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

Young stars have lower velocity Young stars have lower velocity dispersionsdispersions

no DM (R03)

with DM (R03)

DM

all starsyoung stars

Dekel et al 05

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

4th order (h4th order (h44) moments) moments

intermediate radii

out

er

rad

ii

= all stars = young stars

young stars have large |h4| as PNe in galaxies appear to

Gary Mamon, 2 July 2005, PNe as astronomical tools, Gdansk

PNe vs old globular clustersPNe vs old globular clusters

GCs have much higher outer velocity dispersions!Bergond, Zepf et al. 05

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

but GC < stars

GCs

Côté et al. 01

stars

M87

PN luminosity function

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

NGC 4697

Mendez et al. 01

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Marigo et al. 04

young ( 0.8 Gyr) PNe

Possible solutions for young bright PNe in ellipticals

One solution: blue stragglers Ciardullo et al. 05

very low recent star formation in ellipticals

universal PNLF (Es & SMC) Ciardullo et al. 89

young PNe?

} no recentmajor mergers

sufficient bright PN formation with low enough star formation?

Alternative: • gas-rich dark dwarfs fall onto ellipticals, • tidal compression

smooth accretionstar formation universal rate

Conclusions

Merger simulations of spirals embedded in DM yield remnants that reproduce low PN vel. dispersions

consistent with CDM scenario

Spherical kinematical modelling is not fully adequate

Kinematics of young stars in merger remnants

Low velocity dispersion produced by:radial anisotropy steep tracer density viewing oblate ellipticals face-on

(weakly) favors young PNe accretion?