1. Probing Halos with PNe: Mass and Angular Momentum in Early-Type Galaxies
Aaron J. Romanowsky
Collaborators:
N. Douglas, N. Napolitano (Kapteyn), K. Kuijken (Leiden)
M. Merrifield, H. Merrett (Nottingham)
M. Arnaboldi (Torino), O. Gerhard (Basel)
M. Capaccioli (Capodimonte), K. Freeman (RSAA)
E. O’Sullivan (CfA), D. Forbes (Swinburne)
T. Ponman, S. Raychaudhury (Birmingham)
T. Richtler, D. Geisler, M. Gómez (Concepción)
S. Zepf, G. Bergond (Michigan St), R. Sharples (Durham)
M. Hilker, Y. Schuberth (Bonn), L. Infante (PUC)
M. Kissler-Patig (ESO), K. Rhode (Wesleyan)
PNe
X-ray
GCs

2. Probes of early-type galaxy haloes
Apparent inconsistency with galaxy formation theory:
PN dynamics show low DM content in L* Es
But some other observations don‘t support this: weak lensing, satellite dynamics, most strong lenses show much higher DM content
better statistics with larger PN galaxy sample
check independent mass probes (GCs, Xrays) if consistent and reliable, can combine for much stronger constraints on mass, orbit distributions

3. PN.S: primary mission targets
NGC 4636
N4564
N4564
N4339
N4339
N4551
Cluster
N4374
Population 1 (disky/faint)
Population 2 (boxy/bright)
N4494
N4494
N3377
N4742
N3379
N3379
N4278
N5576
Group

4. NGC 3379: Dispersion profile
long-slit data
(Statler & Smecker-Hane 1999)
197 PNe
Isotropic Jeans models:
singular isothermal halo
constant-M/L Hernquist model

5. NGC 3379: orbit models
Orbit stacking/fitting method fully includes uncertainty in orbital anisotropy variations:
cumulative M/L at 5 Reff : = 7.1  0.6
cf. models of stellar pop M/L: = 4 - 9
face-on S0 rather than round elliptical?
disklike kinematics not seen in inner parts (Statler 2001)
see also independent tracers (GCs, HI, Xrays)

6. Probing E haloes with X-rays
Chandra, XMM-Newton: large area, high ang resolution
find T(r), remove point sources, check equilibrium
important to not select on LX (bias in mass results!)
NGC 4365
NGC 4382
Chandra ACIS-S (Sivakoff, Sarazin & Irwin 2003)

7. Probing E haloes w/ globular clusters
GCs as dynamical tracers:
bright: V = in Virgo Cluster
GC systems more spatially extended than stellar light
new spectrographs (wide-field, multi-object): UT2+FLAMES, UT3+VIMOS, Baade+IMACS, Gemini+GMOS, Keck+DEIMOS
probe formational histories of halos: GC formation scenarios generically predict metal-rich GCs have same metallicities, kinematics as halo stars

8. NGC 3379 : circular velocity profile
X-rays from
Chandra+ACIS
(O’Sullivan et al.)
PNe
34 GCs from UT2+FLAMES/GIRAFFE (Bergond et al.)
consistent w/
22 GCs from
Gemini+GMOS
(Beasley et al.)
const M/L

9. NGC 3379: circular velocity profile
HI measurement
of mass of N N3384:
(M/L) B,vir = 27  5 (Schneider 1991)
PNe

10. Probes of early-type galaxy haloes
NGC 1399 (Ikebe et al. 1996; Jones et al. 1997; Paolillo et al. 2002; Napolitano et al. 2002; Richtler et al 2004)
NGC 3379
NGC 4472 (Schindler et al. 1999; Kronawitter et al. 2002)
NGC 4486 (Romanowsky & Kochanek 2001; Matsushita et al. 2002)
NGC 4636 (Matsushita et al. 1998; Kronawitter et al. 2000; Loewenstein & Mushotzky 2002; Schuberth et al. 2004)
NGC 5128 (Peng, Ford & Freeman 2004)
PN, GC, X-ray mass measurements so far generally consistent

11. Combined dispersion profiles
NGC 821,
NGC 3379,
NGC 4494,
NGC 4697 (Méndez et al. 2001):
p(R) declining with R
Isotropic singular isothermal halo
Isotropic constant-M/L Hernquist model

12. X-ray studies of low-luminosity Es
All four low-DM galaxies have low LX
Low LX consistent with
low DM content
(O’Sullivan &
Ponman 2004)
total LX
NGC 4697
NGC 3379
Need larger sample size to ensure we weren’t unlucky
with LX selection
NGC 821
soft LX

13. Explanations
Population of ordinary ellipticals with low DM content
cf. NGC 5128: (M/L)B ~ 18 at Rvir (Peng, Ford & Freeman 2004)
face-on S0s ?
unlikely
stripped DM halos ?
unpredicted
MOdified Newtonian Dynamics ?
inconsistent
low (M/L)* or steep (M/L)* gradient ?
implausible
low concentration halos ?
arguable

14. Stellar population gradients
If stars younger and/or metal-poor in halo:
(M/L)* lower, allows more DM contribution to (M/L)dyn
NGC Mg2 , Fe line strength gradients
(Davies, Sadler & Peletier 1993):
[Fe/H] / log10 r ~ (typical for ellipticals)
Within 5 Reff : 10% lower M*, 40% higher MDM
For MDM=M* at 5 Reff, need [Fe/H] / log10 r ~ -1.4
NGC RGB CMD from HST+NICMOS
(Gregg et al. 2004):
mean halo abundance ~ Solar, no change w/ radius
mean age ~ 8-15 Gyr, no evidence for < 5 Gyr pop

15. Low concentrations / central DM content
PN results for N3379
CDM + early gas outflow, WDM, SIDM, TCDM, RDM, DDM, SADM, FDM...?
vs CDM predictions
(Bullock et al. 2001)
c200 too low unless
star formation
efficiency > 100%
Low halo densities:
LSBs
fundamental plane of
ellipticals (Borriello,
Salucci & Danese 2003)
strong gravitational lenses
(Rusin, Kochanek & Keeton 2003)

16. Angular momentum Dissipationless mergers transfer angular momentum
to outer parts
(Weil & Hernquist 1996;
Bendo & Barnes 2000)
v / ~ 1
for R > 2 Reff
NGC 5128
Elliptical PN results
(NGCs 821, 3379, 4472, 4486, 4494)
 no evidence of merger-induced spin-up

17. Angular momentum Observed discrepancy between spirals and E centres
Simulated E/S0s
(Sommer-Larsen
et al. 2003;
Meza et al. 2003;
Wright et al. 2004) M
E observations
at large R

18. M87: Angular momentum GCs show v / ~ 0.7,  ~ 0.2 (  /support )
in outer parts
(Kissler-Patig &
Gebhardt 1998)
PNe:
v / ~ 0.2,
 ~ 0.05
cf. CDM sims:
 ~ 0.05
(Bullock et al. 2001)

19. NGC 5128: Angular momentum PNe have stronger rotation than GCs
(Peng, Ford & Freeman 2004)

20. NGC 4472: Angular momentum Several cases where GCs
rotation weaker / stronger /
similar to PNe
Expected correlation between
stars, metal-rich GCs
not generally seen!
87 velocities
to ~10 Reff with UT2+FLAMES/
GIRAFFE;
Bergond et al.
GCs rotation
axis twists
by 180°
PNe have
similar (low) rotation to
GCs

21. Summary Multiple lines of evidence for low DM in NGC 3379
Independent mass tracers generally consistent
Pop of L* ellipticals with low DM content
E halo stars rotate much slower than spirals
GC rotation not correlated with stars