Download Exploring and Exploiting Elliptical Galaxy Halos

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)
PNe
M. Arnaboldi (Torino), O. Gerhard (Basel)
M. Capaccioli (Capodimonte), K. Freeman (RSAA)
E. O’Sullivan (CfA), D. Forbes (Swinburne)
X-ray
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)
GCs
M. Kissler-Patig (ESO), K. Rhode (Wesleyan)
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
PN.S: primary mission targets
N4552
NGC 4636
N4564 N4339
N4551
Cluster
Population 1 (disky/faint)
N4494 N3377
N4374
Population 2 (boxy/bright)
N4742
N3379
Group
N4278
N5576
NGC 3379: Dispersion profile
long-slit data
(Statler & SmeckerHane 1999)
197 PNe
Isotropic Jeans
models:
singular
isothermal halo
constant-M/L
Hernquist model
NGC 3379: orbit models
Orbit stacking/fitting method fully includes
uncertainty in orbital anisotropy variations:
• cumulative M/L at 5 Reff :
• cf. models of stellar pop M/L:
= 7.1  0.6
=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)
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)
Probing E haloes w/ globular clusters
GCs as dynamical tracers:
• bright: V = 21-25 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,
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
NGC 3379: circular velocity profile
HI measurement
of mass of
N3379 +
N3384:
(M/L) B,vir = 27  5
(Schneider 1991)
PNe
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
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
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)
NGC 4697
total LX
NGC 3379
Need larger sample
size to ensure we
weren’t unlucky
with L selection
NGC 821
soft LX
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
Stellar population gradients
If stars younger and/or metal-poor in halo:
(M/L)* lower, allows more DM contribution to (M/L)dyn
NGC 3379 Mg2 , Fe line strength gradients
(Davies, Sadler & Peletier 1993):
[Fe/H] / log10 r ~ -0.3
(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 3379 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
Low concentrations / central DM content
PN results for N3379
vs CDM predictions
(Bullock et al. 2001)
CDM + early gas outflow,
WDM, SIDM, TCDM, RDM,
DDM, SADM, FDM...?
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)
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
Observed
discrepancy
between spirals
and E centres
Angular momentum
Simulated E/S0s
(Sommer-Larsen
et al. 2003;
Meza et al. 2003;
Wright et al. 2004)
E observations
at large R
M
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)
NGC 5128: Angular momentum
PNe have stronger rotation than GCs
(Peng, Ford & Freeman 2004)
NGC 4472: Angular momentum
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
 Several cases where GCs
rotation weaker / stronger /
similar to PNe
 Expected correlation between
stars, metal-rich GCs
not generally seen!
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