3 research outputs found
PROFIT: a new alternative for emission-line PROfile FITting
I briefly describe a simple routine for emission-line profiles fitting by
Gaussian curves or Gauss-Hermite series. The PROFIT (line-PROfile FITting)
routine represent a new alternative for use in fits data cubes, as those from
Integral Field Spectroscopy or Fabry-Perot Interferometry, and may be useful to
better study the emission-line flux distributions and gas kinematics in
distinct astrophysical objects, such as the central regions of galaxies and
star forming regions. The PROFIT routine is written in IDL language and is
available at http://www.ufsm.br/rogemar/software.html.
The PROFIT routine was used to fit the [Fe II]1.257um emission-line profiles
for about 1800 spectra of the inner 350 pc of the Seyfert galaxy Mrk1066
obtained with Gemini NIFS and shows that the line profiles are better
reproduced by Gauss-Hermite series than by the commonly used Gaussian curves.
The two-dimensional map of the h_3 Gauss-Hermite moment shows its highest
absolute values in regions close to the edge of the radio structure. These high
values may be originated in an biconical outflowing gas associated with the
radio jet - previously observed in the optical [O III] emission. The analysis
of this kinematic component indicates that the radio jet leaves the center of
the galaxy with the north-west side slightly oriented towards us and the
south-east side away from us, being partially hidden by the disc of the galaxy.Comment: Accepted for publication Astrophysics & Space Science - 7 pges; 4
Fig
Variation of Bar Strength with Central Velocity Dispersion in Spiral Galaxies
We investigate the variation of bar strength with central velocity dispersion
in a sample of barred spiral galaxies. The bar strength is characterized by
, the maximal tangential perturbation associated with the bar, normalized
by the mean axisymmetric force. It is derived from the galaxy potentials which
are obtained using near-infrared images of the galaxies. However, is
sensitive to bulge mass. Hence we also estimated bar strengths from the
relative Fourier intensity amplitude () of bars in near-infrared images.
The central velocity dispersions were obtained from integral field spectroscopy
observations of the velocity fields in the centers of these galaxies; it was
normalized by the rotation curve amplitude obtained from HI line width for each
galaxy. We found a correlation between bar strengths (both and )
and the normalized central velocity dispersions in our sample. This suggests
that bars weaken as their central components become kinematically hotter. This
may have important implications for the secular evolution of barred galaxies.Comment: To appear in Ap&S
Hubble Space Telescope Imaging of the Circinus Galaxy
We present an HST imaging study of the nearby (4 Mpc distant) Circinus
galaxy, which contains the nearest type 2 Seyfert nucleus and prominent
circumnuclear star formation. Images have been obtained in the
[OIII]5007, H and H v=1--0 S(1) emission lines, and in the
green (5470 \AA), red (8140 \AA) and near infrared (2.04 and 2.15 m)
continua. An image in the [Fe II] 1.644 m line has been taken
with a ground-based telescope. The [OIII] and H images reveal the
detailed structure of the complex of streamers and knots of high-excitation
gas, which extends out of the galaxy disk. The morphology some 250 pc from the
nucleus strongly suggests that the high-excitation gas is concentrated on the
surface of a hollow cone with apex close to the nucleus. Such a structure may
result through entrainment of dense gas from a circumnuclear torus in the
galaxy disk by a low density, outflowing wind or jet. Within 40 pc of the
nucleus, the high-excitation gas takes the form of a striking, filled V-shaped
structure extending in the same direction as the larger scale high-excitation
emission. This `V' can be described as an ionization cone, though a
matter-bounded structure is also possible. The implied collimation of the
ionizing photons or gaseous outflow must occur within 2 pc of the apex of the
cone, presumed to be the location of the nucleus. The H image shows a
complex structure of HII regions, including the well known starburst ring of
radius 150 - 270 pc. In addition, there is a more compact (40 pc radius),
elliptical ring of HII regions around the `ionization cone'. We argue that this
latter ring, which we call the nuclear ring, is intrinsically circular and
located in the plane of the galaxy disk. Abstract truncated.Comment: With 12 figures, to be published in the Astronomical Journal,
September 2000 issu