97 research outputs found
Kinematics and dynamics of the M51-type galaxy pair NGC 3893/96 (KPG 302)
We study the kinematics and dynamics of the M51-type interacting galaxy pair
KPG 302 (NGC 3893/96). We analyse the distribution of the dark matter (DM) halo
of the main galaxy in order to explore possible differences between DM halos of
"isolated" galaxies and those of galaxies belonging to a pair. The velocity
field of each galaxy was obtained using scanning Fabry-Perot interferometry. A
two-dimensional kinematic and dynamical analysis of each galaxy and the pair as
a whole is done emphasizing the contribution of circular and non-circular
velocities. Non-circular motions can be traced on the rotation curves of each
galaxy allowing us to differentiate between motions associated to particular
features and motions that reflect the global mass distribution of the galaxy.
For the main galaxy of the pair, NGC 3893, optical kinematic information is
complemented with HI observations from the literature to build a
multi-wavelength rotation curve. We try to fit this curve with a
mass-distribution model using different DM halos. We find that the
multi-wavelength rotation curve of NGC 3893, "cleaned" from the effect of
non-circular motions, cannot be fitted neither by a pseudo-isothermal nor by a
NFW DM halo.Comment: Accepted for publication in A&A. 11 pages, 9 figures and 2 table
Galaxy evolution in groups. NGC 3447/NGC 3447A: the odd couple in LGG 225
Local Group Analogs (LGA) are galaxy associations dominated by few bright
Spirals, reminiscent of the LG. The NGC3447/NGC3447A system, member of the LGG
225 group, a nearby LGA, is considered a physical pair: an intermediate
luminosity late type spiral, NGC3447, and an irregular companion, NGC3447A,
linked by a faint filament of matter. A ring-like structure in the NGC3447
outskirts is emphasised by UV observations. This work aims to contribute to the
understanding of galaxy evolution in low density environments, favourable
habitat to highly effective encounters. We performed a multi-wavelength
analysis of the surface photometry of this system to derive spectral energy
distribution and structural properties using UV and optical images. We also
characterised the velocity field of the pair using new kinematic observations.
All these data are used to constrain smooth particle hydrodynamic simulations
with chemo-photometric implementation to shed light on the evolution of this
system. Luminosity profiles are all consistent with the presence of a disc
extending and including NGC3447A. The overall velocity field does not emphasise
any significant rotation pattern, rather a small velocity gradient between
NGC3447 and NGC3447A. Our simulation, detached from a large grid explored to
best-fit the global properties of the system, suggests that this arises from an
encounter between two halos of equal mass. NGC3447 and NGC3447A belong to the
same halo, NGC3447A being a substructure of the same disk as NGC3447. The halo
gravitational instability, enhanced by the encounter, fuels a long lived
instability in this dark matter dominated disk, driving its morphology. This
system may warn about a new class of "false pairs" and the potential danger of
a misunderstanding of such objects in pair surveys that could produce a severe
underestimate of the total mass of the system. (abridged)Comment: 14 pages, 10 figures, A&A accepte
Kinematics of Herbig-Haro Objects and Jets in the Orion Nebula
We have surveyed the inner 5' of the Orion Nebula by means of Halpha and
[NII] Fabry-Perot imaging spectroscopy to present a kinematical study of the
Herbig-Haro objects in the nebula. The objects studied in this work are HH 202,
203, 204, 529, 269 and other associated features. For HH 202 we find new
features that, because of their high velocities (up to 100 km/seg) indicate the
presence of an outflow that probably is a HH flow not catalogued previously. HH
202 could be only a part of this larger outflow. Large internal motions are
found in the fainter regions of HH 203-204, as well as evidence of transverse
density gradients that could account for the asymmetry in the brightness
distribution of HH 204. We report for the first time a high blueshifted
velocity (-118 km/seg) associated with HH 204, and show that the apex of HH 204
is indeed the zone of maximum velocity, in agreement with bow shock models. We
also studied the radial velocity field of HH 269 finding features associated
with the HH object. From our studies, we find kinematic evidence that suggests
that HH 203-204 and HH 202 are part of a big (aprox. 0.55 pc) bipolar HH
outflow.Comment: 24 pages, 10 figures (in three jpg files). To be Published in
Astronomical Journa
Unveiling the Kinematics and Dynamics of Ionized Gas in the Nearby Irregular Galaxy NGC 4449
A detailed kinematic analysis of ionized gas in the nearby irregular galaxy
NGC 4449 is presented. Observations are conducted in the spectral lines of
Halpha and [SII]. Our scanning Fabry--Perot interferometric observations are
presented from both a global as well as a local perspective. We have analysed
the global velocity field, the spatially extended diffuse gaseous component
(DIG), the HII region populations, and, furthermore, have determined the
rotation curve based on the heliocentric radial velocities of the global Halpha
spatial distribution. Our results for NGC 4449 show that the optical velocity
field has a decreasing value in radial velocity along the optical bar from NE
to SW. The DIG component that permeates the entire galaxy was analysed (up to a
limiting surface brightness of ~ 3.165x10^-5 ergs cm$^-2 s^-1 steradian^-1). We
find that the diffuse gas component presents peculiar kinematical features such
as abrupt velocity gradients and highly supersonic velocity dispersions
(sigma~4 times the values of the nearest HII regions) but that its kinematical
and dynamical influence is important on both global and local scales. The
optical rotation curve of this nearby irregular shows that the NE sector
rotates like a solid body (V_rot~40 km s^-1 at R=2 kpc). For the SW side, our
results are not conclusive; the behavior of the gas at those locations is
chaotic. We conclude that the origin of such complex kinematics and dynamics is
undoubtedly related to the aftermath of an interaction experienced by this
galaxy in the past (abridged).Comment: AJ accepted, December issue, 33 pages, 13 figure
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