951 research outputs found
BhaBAR: Big Halpha kinematical sample of BARred spiral galaxies - I. Fabry-Perot Observations of 21 galaxies
The Halpha gas kinematics of twenty-one representative barred spiral galaxies
belonging to the BHaBAR sample is presented. The galaxies were observed with
FaNTOmM, a Fabry-Perot integral-field spectrometer, on three different
telescopes. The 3D data cubes were processed through a robust pipeline with the
aim of providing the most homogeneous and accurate dataset possible useful for
further analysis. The data cubes were spatially binned to a constant
signal-to-noise ratio, typically around 7. Maps of the monochromatic Halpha
emission line and of the velocity field were generated and the kinematical
parameters were derived for the whole sample using tilted-ring models. The
photometrical and kinematical parameters (position angle of the major axis,
inclination, systemic velocity and kinematical centre) are in relative good
agreement, except maybe for the later-type spirals.Comment: 34 pages, 25 figures, accepted for publication in MNRAS. To obtain a
higher resolution version, go to
ftp://ftp.astro.umontreal.ca/outgoing/olivier/bhabar.pdf or to
http://www.astro.umontreal.ca/fantomm/bhabar
HI studies of the Sculptor group galaxies. VIII. The background galaxies: NGC 24 and NGC 45
In order to complete our HI survey of galaxies in the Sculptor group area,
VLA observations of NGC 24 and NGC 45 are presented. These two galaxies of
similar magnitude M_B ~ -17.4 lie in the background of the Sculptor group and
are low surface brightness galaxies, especially NGC 45. The HI distribution and
kinematics are regular for NGC 24 while NGC 45 exhibits a kinematical twist of
its major axis. A tilted-ring model shows that the position angle of the major
axis changes by ~25 degrees. A best-fit model of their mass distribution gives
mass-to-light ratios for the stellar disk of 2.5 and 5.2 for NGC 24 and NGC 45
respectively. These values are higher than the ones expected from stellar
population synthesis models. Despite the large dark matter contribution, the
galaxy mass is still dominated by the stellar component in their very inner
regions. These high mass-to-light ratios are typical of what is seen in low
surface brightness galaxies and may indicate that, in those galaxies, disks are
far from the maximum disk case. The halo parameters derived from the best-fit
models are thus lower limits.Comment: 23 pages, 10 figures, accepted for publication in The Astronomical
Journa
Globular clusters and dwarf galaxies in Fornax - I. Kinematics in the cluster core from multi-object spectroscopy
We acquired radial velocities of a significant number of globular clusters
(GCs) on wide fields between galaxies in the nearby Fornax cluster of galaxies,
in order to derive their velocity dispersion radial profile and to probe the
dynamics of the cluster. We used FLAMES on the VLT to obtain accurate
velocities for 149 GCs, within a ~500x150 kpc strip centered on NGC 1399, the
Fornax central galaxy. These objects are at the very bright tail (M_V < -9.5)
of the GC luminosity function, overlapping the so-called ``ultra-compact
dwarfs'' magnitude range. Eight of the brightest FLAMES-confirmed members
indeed show hints of resolution in the subarcsecond pre-imaging data we used
for selecting the ~500 targets for FLAMES spectroscopy. Ignoring the GCs around
galaxies by applying 3d_25 diameter masks, we find 61 GCs of 20.0 < V < 22.2
lying in the intra-cluster (IC) medium. The velocity dispersion of the
population of ICGCs is 200 km/s at ~150 kpc from the central NGC 1399 and rises
to nearly 400 km/s at 200 kpc, a value which compares with the velocity
dispersion of the population of dwarf galaxies, thought to be infalling from
the surroundings of the cluster.Comment: To be published in A&A Letters. 4 pages, 3 figures, 3 table
Velocity measurement in the extensive [OIII] emission region 1.2{\deg} south-east of M31
The discovery of a broad, 1.5 long filamentary [OIII] 5007
emission 1.2 south-east of the M31 nucleus has recently been
reported. More than 100 hours of exposures of a wide field (3.48) have allowed this pioneering detection based on 30 \AA\
narrow-band filters and several small refractors equipped with large cameras.
We report a first velocity measurement in this extensive [OIII] emission line
region. We used the low-resolution spectrograph MISTRAL (R 750), a
facility of the Haute-Provence Observatory 193 cm telescope. The velocity
measurement is based on the H, [NII], [SII] and [OIII] lines. The best
solution to fit the spectrum indicates that the H and [OIII] emissions
are at the same heliocentric line-of-sight velocity of -964 km s.
This was measured within an area of 250 arcsec selected on a bright
knot along the long filament of 1.5, together with a [OIII]5007
surface brightness of 4.22.1 10 erg s cm
arcsec. This agrees moderately well with the previous measurement. We
also estimated the H/[NII] line ratio as 1.1. The radial
velocities at which the H and [OIII] lines were detected seem to show
that these hydrogen and oxygen atoms belong to the same layer, but we cannot
exclude that another weaker [OIII] line, belonging to another structure, that
is, at another velocity, is below our detection threshold. Different scenarios
have been considered to explain this filamentary structure...Comment: 8 pages, 5 figures, A&A letters, Accepte
The catalog of radial velocity standard stars for the Gaia RVS: status and progress of the observations
A new full-sky catalog of Radial Velocity standard stars is being built for
the determination of the Radial Velocity Zero Point of the RVS on board of
Gaia. After a careful selection of 1420 candidates matching well defined
criteria, we are now observing all of them to verify that they are stable
enough over several years to be qualified as reference stars. We present the
status of this long-term observing programme on three spectrographs : SOPHIE,
NARVAL and CORALIE, complemented by the ELODIE and HARPS archives. Because each
instrument has its own zero-point, we observe intensively IAU RV standards and
asteroids to homogenize the radial velocity measurements. We can already
estimate that ~8% of the candidates have to be rejected because of variations
larger than the requested level of 300 m/s.Comment: Proceedings of SF2A2010, S. Boissier, M. Heydari-Malayeri, R. Samadi
and D. Valls-Gabaud (eds), 3 pages, 2 figure
Global well-posedness for a Smoluchowski equation coupled with Navier-Stokes equations in 2D
We prove global existence for a nonlinear Smoluchowski equation (a nonlinear
Fokker-Planck equation) coupled with Navier-Stokes equations in two dimensions.
The proof uses a deteriorating regularity estimate and the tensorial structure
of the main nonlinear terms
Improved 3D Fabry-Perot Data Reduction Techniques
Improved data reduction techniques for 3D data cubes obtained from
Fabry-Perot integral field spectroscopy are presented. They provide accurate
sky emission subtraction and adaptive spatial binning and smoothing. They help
avoiding the effect analogous to the beam smearing, seen in HI radio data, when
strong smoothing is applied to 3D data in order to get the most extended signal
coverage. The data reduction techniques presented in this paper allow one to
get the best of both worlds: high spatial resolution in high signal-to-noise
regions and large spatial coverage in low signal-to-noise regions.Comment: 10 pages, 9 figures, accepted for publication in MNRA
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