3,022 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
2D kinematics of the edge-on spiral galaxy ESO 379-G006
We present a kinematical study of the nearly edge-on galaxy ESO 379-G006 that
shows the existence of extraplanar ionized gas. With Fabry-Perot spectroscopy
at H-alpha, we study the kinematics of ESO 379-G006 using velocity maps and
position-velocity diagrams parallel to the major and to the minor axis of the
galaxy. We build the rotation curve of the disk and discuss the role of
projection effects due to the fact of viewing this galaxy nearly edge-on. The
twisting of the isovelocities in the radial velocity field of the disk of ESO
379-G006 as well as the kinematic asymmetries found in some position-velocity
diagrams parallel to the minor axis of the galaxy suggest the existence of
deviations to circular motions in the disk that can be modeled and explained
with the inclusion of a radial inflow probably generated by a bar or by spiral
arms. We succeeded in detecting extraplanar Diffuse Ionized Gas in this galaxy.
At the same time, from the analysis of position-velocity diagrams, we found
some evidence that the extraplanar gas could lag in rotation velocity with
respect to the midplane rotation.Comment: 61 pages, 15 figures. Accepted for publication in A
The Compact Group of Galaxies HCG 31 is in an early phase of merging
We have obtained high spectral resolution (R = 45900) Fabry-Perot velocity
maps of the Hickson Compact Group HCG 31 in order to revisit the important
problem of the merger nature of the central object A+C and to derive the
internal kinematics of the candidate tidal dwarf galaxies in this group. Our
main findings are: (1) double kinematic components are present throughout the
main body of A+C, which strongly suggests that this complex is an ongoing
merger (2) regions and E, to the east and south of complex A+C, present
rotation patterns with velocity amplitudes of and they
counterrotate with respect to A+C, (3) region F, which was previously thought
to be the best example of a tidal dwarf galaxy in HCG 31, presents no rotation
and negligible internal velocity dispersion, as is also the case for region
. HCG 31 presents an undergoing merger in its center (A+C) and it is likely
that it has suffered additional perturbations due to interactions with the
nearby galaxies B, G and Q.Comment: 5 pages + figures - Accepted to ApJ Lette
Down-regulation of human topoisomerase IIα expression correlates with relative amounts of specificity factors Sp1 and Sp3 bound at proximal and distal promoter regions
<p>Abstract</p> <p>Background</p> <p>Topoisomerase IIα has been shown to be down-regulated in doxorubicin-resistant cell lines. The specificity proteins Sp1 and Sp3 have been implicated in regulation of topoisomerase IIα transcription, although the mechanism by which they regulate expression is not fully understood. Sp1 has been shown to bind specifically to both proximal and distal GC elements of the human topoisomerase IIα promoter <it>in vitro</it>, while Sp3 binds only to the distal GC element unless additional flanking sequences are included. While Sp1 is thought to be an activator of human topoisomerase IIα, the functional significance of Sp3 binding is not known. Therefore, we sought to determine the functional relationship between Sp1 and Sp3 binding to the topoisomerase IIα promoter <it>in vivo</it>. We investigated endogenous levels of Sp1, Sp3 and topoisomerase IIα as well as binding of both Sp1 and Sp3 to the GC boxes of the topoisomerase IIα promoter in breast cancer cell lines <it>in vivo </it>after short term doxorubicin exposure.</p> <p>Results</p> <p>Functional effects of Sp1 and Sp3 were studied using transient cotransfection assays using a topoisomerase IIα promoter reporter construct. The <it>in vivo </it>interactions of Sp1 and Sp3 with the GC elements of the topoisomerase IIα promoter were studied in doxorubicin-treated breast cancer cell lines using chromatin immunoprecipitation assays. Relative amounts of endogenous proteins were measured using immunoblotting. <it>In vivo </it>DNA looping mediated by proteins bound at the GC1 and GC2 elements was studied using the chromatin conformation capture assay. Both Sp1 and Sp3 bound to the GC1 and GC2 regions. Sp1 and Sp3 were transcriptional activators and repressors respectively, with Sp3 repression being dominant over Sp1-mediated activation. The GC1 and GC2 elements are linked <it>in vivo </it>to form a loop, thus bringing distal regulatory elements and their cognate transcription factors into close proximity with the transcription start site.</p> <p>Conclusion</p> <p>These observations provide a mechanistic explanation for the modulation of topoisomerase IIα and concomitant down-regulation that can be mediated by topoisomerase II poisons. Competition between Sp1 and Sp3 for the same cognate DNA would result in activation or repression depending on absolute amounts of each transcription factor in cells treated with doxorubicin.</p
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
Fabry-Perot observations of the HH 110 jet
We have obtained a Halpha position-velocity cube from Fabry-Perot
interferometric observations of the HH 110 flow. We analyze the results in
terms of anisotropic wavelet transforms, from which we derive the spatial
distribution of the knots as well as their characteristic sizes (along and
across the outflow axis). We then study the spatial behaviour of the line width
and the central radial velocity. The results are interpreted in terms of a
simple ``mean flow+turbulent eddy'' jet/wake model. We find that most of the
observed kinematics appear to be a direct result of the mean flow, on which are
superposed low amplitude (35 km/s) turbulent velocities.Comment: 27 pages, 8 Postscript figures. Astronomical Journal (accepted
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
The realization space of a certain conic line arrangement of degree 7 and a -equivalent Zariski pair
In this paper, we continue the study of the embedded topology of plane
algebraic curves. We study the realization space of conic line arrangements of
degree with certain fixed combinatorics and determine the number of
connected components. This is done by showing the existence of a Zariski pair
having these combinatorics, which we identified as a -equivalent Zariski
pair.Comment: 24 page
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