369 research outputs found
Probing the kinematics of early-type galaxy halos using planetary nebulae
We present first results of a study of the halo kinematics for a sample of
early type galaxies using planetary nebulae (PNe) as kinematical tracers. PNe
allow to extend up to several effective radii (Re) the information from
absorption line kinematics (confined to within 1 or 2 Re), providing valuable
information and constraints for merger simulations and galaxy formation models.
We find that the specific angular momentum per unit mass has a more complex
radial dependence when the halo region is taken into account and that the halo
velocity dispersion is related to the total galaxy luminosity, isophotal shape,
and number of PNe per unit of luminosityComment: 4 pages, 3 figures. refereed proceeding of the "Galactic and Stellar
Dynamics 2008" conference, Ed. C.M. Boily. To be published in AN, year: 2008,
vol: 329, Issue: 9-10, pages: 912-91
Stepwise acquisition of vocal combinatorial capacity in songbirds and human infants
Human language, as well as birdsong, relies on the ability to arrange vocal elements in novel sequences. However, little is known about the ontogenetic origin of this capacity. We tracked the development of vocal combinatorial capacity in three species of vocal learners, combining an experimental approach in zebra finches with an analysis of natural development of vocal transitions in Bengalese finches and pre-lingual human infants and found a common, stepwise pattern of acquiring vocal transitions across species. In our first study, juvenile zebra finches were trained to perform one song and then the training target was altered, prompting the birds to swap syllable order, or insert a new syllable into a string. All birds solved these permutation tasks in a series of steps, gradually approximating the target sequence by acquiring novel pair-wise syllable transitions, sometimes too slowly to fully accomplish the task. Similarly, in the more complex songs of Bengalese finches, branching points and bidirectional transitions in song-syntax were acquired in a stepwise manner, starting from a more restrictive set of vocal transitions. The babbling of pre-lingual human infants revealed a similar developmental pattern: instead of a single developmental shift from reduplicated to variegated babbling (i.e., from repetitive to diverse sequences), we observed multiple shifts, where each novel syllable type slowly acquired a diversity of pair-wise transitions, asynchronously over development. Collectively, these results point to a common generative process that is conserved across species, suggesting that the long-noted gap between perceptual versus motor combinatorial capabilities in human infants1 may arise from the challenges in constructing new pair-wise transitions
Kinematic properties of early-type galaxy haloes using planetary nebulae
We present new planetary nebulae (PNe) positions, radial velocities, and
magnitudes for 6 early-type galaxies obtained with the Planetary Nebulae
Spectrograph, their two-dimensional velocity and velocity dispersion fields. We
extend this study to include an additional 10 early-type galaxies with PNe
radial velocity measurements available from the literature, to obtain a broader
description of the outer-halo kinematics in early-type galaxies. These data
extend the information derived from stellar kinematics to typically up to ~8
Re. The combination of photometry, stellar and PNe kinematics shows: i) good
agreement between the PNe number density and the stellar surface brightness in
the region where the two data sets overlap; ii) good agreement between PNe and
stellar kinematics; iii) that the mean rms velocity profiles fall into two
groups: with of the galaxies characterized by slowly decreasing profiles and
the remainder having steeply falling profiles; iv) a larger variety of velocity
dispersion profiles; v) that twists and misalignments in the velocity fields
are more frequent at large radii, including some fast rotators; vi) that outer
haloes are characterised by more complex radial profiles of the specific
angular momentum-related lambda_R parameter than observed within 1Re; vii) that
many objects are more rotationally dominated at large radii than in their
central parts; and viii) that the halo kinematics are correlated with other
galaxy properties, such as total luminosity, isophotal shape, total stellar
mass, V/sigma, and alpha parameter, with a clear separation between fast and
slow rotators.Comment: 36 pages, 21 figures, revised version for MNRA
The PN.S Elliptical Galaxy Survey: the dark matter in NGC 4494
We present new Planetary Nebula Spectrograph observations of the ordinary
elliptical galaxy NGC 4494, resulting in positions and velocities of 255 PNe
out to 7 effective radii (25 kpc). We also present new wide-field surface
photometry from MMT/Megacam, and long-slit stellar kinematics from VLT/FORS2.
The spatial and kinematical distributions of the PNe agree with the field stars
in the region of overlap. The mean rotation is relatively low, with a possible
kinematic axis twist outside 1 Re. The velocity dispersion profile declines
with radius, though not very steeply, down to ~70 km/s at the last data point.
We have constructed spherical dynamical models of the system, including Jeans
analyses with multi-component LCDM-motivated galaxies as well as logarithmic
potentials. These models include special attention to orbital anisotropy, which
we constrain using fourth-order velocity moments. Given several different sets
of modelling methods and assumptions, we find consistent results for the mass
profile within the radial range constrained by the data. Some dark matter (DM)
is required by the data; our best-fit solution has a radially anisotropic
stellar halo, a plausible stellar mass-to-light ratio, and a DM halo with an
unexpectedly low central density. We find that this result does not
substantially change with a flattened axisymmetric model.
Taken together with other results for galaxy halo masses, we find suggestions
for a puzzling pattern wherein most intermediate-luminosity galaxies have very
low concentration halos, while some high-mass ellipticals have very high
concentrations. We discuss some possible implications of these results for DM
and galaxy formation.Comment: 29 pages, 17 figures. MNRAS, accepte
Diffuse light and galaxy interactions in the core of nearby clusters
The kinematics of the diffuse light in the densest regions of the nearby
clusters can be unmasked using the planetary nebulae (PNs) as probes of the
stellar motions. The position-velocity diagrams around the brightest cluster
galaxies (BCGs) identify the relative contributions from the outer halos and
the intracluster light (ICL), defined as the light radiated by the stars
floating in the cluster potential. The kinematics of the ICL can then be used
to asses the dynamical status of the nearby cluster cores and to infer their
formation histories. The cores of the Virgo and Coma are observed to be far
from equilibrium, with mergers currently on-going, while the ICL properties in
the Fornax and Hydra clusters show the presence of sub-components being
accreted in their cores, but superposed to an otherwise relaxed population of
stars. Finally the comparison of the observed ICL properties with those
predicted from Lambda-CDM simulations indicates a qualitative agreement and
provides insights on the ICL formation. Both observations and simulations
indicate that BCG halos and ICL are physically distinct components, with the
``hotter" ICL dominating at large radial distances from the BCGs halos as the
latter become progressively fainter.Comment: 14 pages, 5 figures. Invited review to appear in the proceedings of
"Galaxies and their masks" eds. Block, D.L., Freeman, K.C. and Puerari, I.,
2010, Springer (New York
SILAGEM DE CASCA DE MANDIOCA EM SUBSTITUIÇÃO A SILAGEM DA PLANTA INTEIRA DE MILHO NA ALIMENTAÇÃO DE CORDEIROS - BIOMETRIA IN VIVO
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A deep kinematic survey of planetary nebulae in the Andromeda Galaxy using the Planetary Nebula Spectrograph
We present a catalogue of positions, magnitudes and velocities for 3300
emission-line objects found by the Planetary Nebula Spectrograph in a survey of
the Andromeda Galaxy, M31. Of these objects, 2615 are found likely to be
planetary nebulae (PNe) associated with M31. Initial results from this survey
include: the likely non-existence of Andromeda VIII; a universal PN luminosity
function, with the exception of a small amount of obscuration, and a small
offset in normalization between bulge and disk components; very faint
kinematically-selected photometry implying no cut-off in the disk to beyond 4
scalelengths and no halo population in excess of the bulge out to 10 effective
bulge radii; disk kinematics that show significant dispersion and asymmetric
drift out to large radii, consistent with a warm flaring disk; and no sign of
any variation in kinematics with PN luminosity, suggesting that PNe arise from
a fairly uniform population of old stars.Comment: Accepted by MNRAS. 23 pages, 37 figures. A full resolution version is
available at http://www.astro.rug.nl/~pns/pns_pub.htm
CORTES COMERCIAIS DA CARCAÇA DE CORDEIROS ALIMENTADOS COM DIFERENTES NÍVEIS DE SILAGEM DE CASCA DE MANDIOCA
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