MPE OPINAS Dynamics
The study of kinematic properties, angular momentum and amount
of dark matter in the halos of earlytype galaxies (ETGs) is limited by
the rapid fall-off of the stellar surface brightness. This difficulty
can be overcome by using radial velocities of Planetary Nebulae (PNe),
which can be obtained much further out than traditional absorption-line
kinematics, given their bright [OIII] emission lines. The use of PNe
allowed us to measure for the very first time two-dimensional velocity
and velocity dispersion fields out to ~6-9 effective radii in nearby
1. Planetary nebula kinematics in NGC 1316: a young Sombrero
|Figure 1. Spatial distribution of the PNs tha were found in the NGC 1316 observations.
The north-east is rotating away from the observer while the south-west is moving
towards us relative to the mean. North is up and East is left.
||Figure 2. Jeans model with no dark matter compared with the velocity dispersion profile of NGC 1316.
The disagreement between the model and the observations in the outer part underlines
the importance of dark matter in the dynamics of NGC 1316
An exceptionally large sample of PN velocities makes
it possible to explore in detail the kinematics of the Fornax
Brightest Cluster Galaxy, NGC 1316, a merger remnant.
The two-dimensional velocity field shows dynamically-important
rotation that rises in the outer parts, possibly due to the outward
transfer of angular momentum during the merger. We use spherical,
non-rotating, constant-anisotropy Jeans models were to analyze the kinematic
data. These indicate a high dark matter content, particularly in the
outer parts. NGC 1316 represents, then, a transition phase from a
major-merger event to a bulge-dominated galaxy.
2. Kinematics and Angulare Momentum in the Outer Halos of Early Type Galaxies
|Figure 1. DSS
image of NGC 4474 with PNe data superimposed. Crosses represent the
position of each PNe; colors indicate the mean value of the
two-dimensional velocity field reconstructed from the PNe data.
Iso-velocity contours are also shown. The field of view is 11'x11',
North is up, East is left.
||Figure 2. Radial
profile of the angular momentum proxy LR. Red and blue profiles are
taken from the SAURON sample (Emsellem et al. 2007) and represent slow
rotators (galaxies with LR < 0.1) and fast rotators (LR > 0.1),
respectively. Black profiles are computed using PNe radial velocity
the past years we conducted an observational campain with the Planetary
Nebulae Spectrograph (Douglas et al. 2002) aimed to measure the radial
velocities of PNe in the halos of ETGs (see Figure 1). In our first
official data release (Coccato et al. 2009) we combined absorption line
data and PNe radial velocity measurements in 16 ETGs. Our analysis
showed that: i) PNe are good tracers of the mean stellar population
kinematics, as their kinematics and number density agrees with the
stellar absorption line kinematics and surface brightness; ii) outer
halos have more complex radial profiles of the lR parameter (a proxy
for the angular momentum, Emsellem et al. 2007) than observed within 1
Re. Interestingly, in the halo, some fast rotators have declining lR
radial profiles, almost reaching the slow rotator regime, while some
slow rotators have slowly increasing lR profiles, which reach the fast
rotator regime (see Figure 2); iii) the velocity dispersion profiles
fall into two groups, with part of the galaxies characterized by slowly
decreasing profiles and the remainder having steeply falling profiles;
iv) the halo kinematics are correlated with other galaxy properties,
such as luminosity, shape, total stellar mass, V/s, and number of PNe
per unit luminosity, with a clear distinction between fast and slow
Coccato, L., Gerhard, O., Arnaboldi, M., Das, P., Douglas, N. G.,
Kuijken, K., et al. 2009, MNRAS, 394, 1249.
Kinematic properties of early-type galaxy haloes using
Coccato, L., Gerhard, O., Arnaboldi, M., Das, P., Douglas, N.
G., Kuijken, K., et al. 2008, AN, 329, 912.
Probing the kinematics of early-type galaxy halos using
Noordermeer, E., Merrifield, M. R., Coccato, L., Arnaboldi, M.,
Capaccioli, M., Douglas, N. G., et al. 2008, MNRAS, 384, 943.
Testing the nature of S0 galaxies using planetary nebula
kinematics in NGC 1023
Douglas, N. G., Napolitano, N. R., Romanowsky, A. J., Coccato, L.,
Kuijken, K., Merrifield, M. R., et al. 2007, ApJ, 664, 257.
The PN.S Elliptical Galaxy Survey: Data Reduction, Planetary Nebula
Catalog, and Basic Dynamics for NGC 3379
Merrett, H. R., Merrifield, M. R., Douglas, N. G., Kuijken, K.,
Romanowsky, A. J., Napolitano, N. R., et al. 2006, MNRAS, 369, 120.
A deep kinematic survey of planetary nebulae in the
Andromeda galaxy using the Planetary Nebula Spectrograph