295 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
On the relevance of the Tremaine-Weinberg method applied to H-alpha velocity field.Pattern speeds determination in M100 (NGC 4321)
The relevance of the Tremaine-Weinberg (TW) method is tested to measure the
bar, spiral and inner structure pattern speeds using a gaseous velocity field.
The TW method is applied to various simulated barred galaxies in order to
demonstrate its validity in seven different configurations, including star
formation or/and dark matter halo. The reliability of the different physical
processes involved and of the various observational parameters are also tested.
The simulations show that the TW method could be applied to the gaseous
velocity fields to get a good estimate of the bar pattern speed, under the
condition that regions of shocks are avoided and measurements are confined to
regions where the gaseous bar is well formed. We successfully apply the TW
method to the \ha velocity field of the Virgo Cluster Galaxy M100 (NGC 4321)
and derive pattern speeds of 55+/-5 km/s/kpc for the nuclear structure, 30+/-2
km/s/kpc for the bar and 20+/-1 km/s/kpc for the spiral pattern, in full
agreement with published determinations using the same method or alternative
ones.Comment: 29 pages, 8 figures, accepted for publication in ApJ. To obtain a
higher resolution version, visit to
http://www.astro.umontreal.ca/fantomm/bhabar
Physiological and Social Stress on Cognitive Performance
Humans are highly social creatures and this provides us with a number of benefits, such as protection and support, but it also brings new avenues for stress from social sources. Basic and translational neuroendocrine research has yielded a rich set of findings and a general understanding of how acute and chronic stress can result in reduced health, earlier aging, and earlier death. Although stress can be indexed by level of cortisol, the major stress hormone in humans, many interrelated physiological systems are involved in a stress response, including the cardio and vascular systems. Research toward greater understanding of stress buffering mechanisms holds value for improved human health in the face of entrenched social stressors.
In particular, acute and chronic stress have consistently been found to impair cognitive performance, Many adults in high stress environments also face a changing social landscape during college years: changes in living partners, less control over noise, sleep, exercise, and nutrition. In this pilot investigation, we are interested in measuring the influences of acute stress on cognitive performance and whether social support, a factor that is modifiable, would be protective on the multi-systems relationships between stress and cognition.
Broadly, we found (1) that higher levels of cortisol measured in saliva was associated with a faster return to resting levels of salivary cortisol (a measure of flexible, adaptive functioning of the central HPA stress system) after the stressor is removed and may also be associated with lower cortisol in the initial response to the stressor. In parallel, we found (2) that higher levels of cortisol were associated with impaired cognitive performance after the stress task, (3) finally, we found that those reporting high social support showed faster recovery to baseline in the cardiovascular systems and greater social support produced some buffering of stress response on their post-stress cognitive performance
An Evolutionary Sequence of Expanding Hydrogen Shells in Galaxy Discs
Large HI shells, with diameters of hundreds of pc and expansion velocities of
10-20kms-1 are well observed features of local gas rich galaxies. These shells
could well be predicted as a result of the impact of OB associations on the
ISM, but doubt has been cast on this scenario by the apparent absence of OB
stars close to the centres of a large fraction of these shells in recent
observations of the SMC. Using Fabry-Perot scanned Halpha emission line mapping
of nearby galaxy discs we have detected, in all the HII regions where the
observations yield sufficient angular resolution and S:N ratio, dominant Halpha
shells with radii a few tens of pc, expanding at velocities of 50-100kms-1. We
have applied a simple dynamically consistent framework in which we can
extrapolate the properties of the observed Halpha shells to a few 10^7yr after
the formation of the OB stars. The framework includes the dynamical inputs of
both winds and SNe on the surrounding ISM. The results give quantitative
statistical support to the hypothesis that the Halpha emitting shells are
generic progenitors of the HI shells. During the time taken for an expanding
shell to reach the size of a typical HI shell, the OB association may well lose
its most luminous stars so the absence of such stars near the centres of many
of the HI shells is well explained in this scenario.Comment: 8 pages, 4 figures, accepted for publication in Astronomy and
Astrophysic
H-alpha Kinematics of the SINGS Nearby Galaxies Survey. I
This is the first part of an Halpha kinematics follow-up survey of the SINGS
sample. The data for 28 galaxies are presented. The observations were done on
three different telescopes with FaNTOmM, an integral field photon counting
spectrometer, installed in the respective focal reducer of each telescope. The
data reduction was done through a newly built pipeline with the aim of
producing the most homogenous data set possible. Adaptive spatial binning was
applied to the data cubes in order to get a constant signal-to-noise ratio
across the field of view. Radial velocity and monochromatic maps were generated
using a new algorithm and the kinematical parameters were derived using
tilted-ring models.Comment: 47 pages, 37 figures, accepted for publication in MNRAS. All
high-res. figures are available at
http://www.astro.umontreal.ca/fantomm/sings . An high-res. version of the
article is available at http://www.astro.umontreal.ca/~odaigle/SINGS.pd
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
Deep H{\alpha} Observations of NGC 253: a Very Extended and Possibly Declining Rotation Curve?
This study presents a deep H{\alpha} kinematical analysis of the Sculptor
Group galaxy NGC253. The Fabry-Perot data were taken with the 36-cm Marseille
Telescope in La Silla, Chile, using an EMCCD detector. Typical emission
measures of ~0.1 cm^-6 pc are reached. The observations allow the detection of
the Diffuse Ionized Gas component through [N II] emission at very large radii
of 11.5', 12.8' and 19.0', on the receding side of the galaxy. No H{\alpha}
emission is observed at radii larger than the neutral component (11.5'). The
very extended rotation curve confirms previous results and shows signs of a
significant decline, on the order of 30 per cent vmax . Using the rotation
data, mass models are constructed with and without the outer [N II] data
points, and similar results are found. The declining part of the rotation curve
is very well modeled, and seems to be truly declining.Comment: Accepted for publication in MNRAS. 16 pages, 10 figures, 4 table
GHASP : An Halpha kinematic survey of spiral and irregular galaxies - VI. New Halpha data cubes for 108 galaxies
We present the Fabry-Perot observations obtained for a new set of 108
galaxies that completes the GHASP survey (Gassendi HAlpha survey of SPirals).
The GHASP survey consists of 3D Ha data cubes for 203 spiral and irregular
galaxies, covering a large range in morphological types and absolute
magnitudes, for kinematics analysis. The GHASP sample is by now the largest
sample of Fabry-Perot data ever published. We have derived Ha data cubes from
which are computed Ha maps, radial velocity fields as well as residual velocity
fields, position-velocity diagrams, rotation curves and the kinematical
parameters for almost all galaxies. Original improvements in the determination
of the kinematical parameters, rotation curves and their uncertainties have
been implemented in the reduction procedure. This new method is based on the
whole 2D velocity field and on the power spectrum of the residual velocity
fieldrather than the classical method using successive crowns in the velocity
field. Among the results, we point out that morphological position angles have
systematically higher uncertainties than kinematical ones, especially for
galaxies with low inclination. Morphological inclination of galaxies having no
robust determination of their morphological position angle cannot be
constrained correctly. Galaxies with high inclination show a better agreement
between their kinematical inclination and their morphological inclination
computed assuming a thin disk. The consistency of the velocity amplitude of our
rotation curves have been checked using the Tully-Fisher relationship. Our data
are in good agreement with previous determinations found in the literature.
Nevertheless, galaxies with low inclination have statistically higher
velocities than expected and fast rotators are less luminous than expected.Comment: accepted in MNRAS for publication, 60 pages, 25 figures, usues
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