1,034 research outputs found
A SINFONI view of Galaxy Centers: Morphology and Kinematics of five Nuclear Star Formation Rings
We present near-infrared (H- and K-band) integral-field observations of the
circumnuclear star formation rings in five nearby spiral galaxies. The data,
obtained at the Very Large Telescope with the SINFONI spectrograph, are used to
construct maps of various emission lines that reveal the individual star
forming regions ("hot spots") delineating the rings. We derive the
morphological parameters of the rings, and construct velocity fields of the
stars and the emission line gas. We propose a qualitative, but robust,
diagnostic for relative hot spot ages based on the intensity ratios of the
emission lines Brackett gamma, HeI, and [FeII]. Application of this diagnostic
to the data presented here provides tentative support for a scenario in which
star formation in the rings is triggered predominantly at two well-defined
regions close to, and downstream from, the intersection of dust lanes along the
bar with the inner Lindblad resonance.Comment: 45 pages incl. 4 tables and 12 (mostly color) figures. Accepted for
publication in AJ. A version with full resolution figures can be obtained at
ftp://ftp.rssd.esa.int/pub/tboeker/SINFONI/ms.pd
Spectral Analysis of Correlated One-Dimensional Systems with Impurities
An averaging procedure is proposed to account for spectral features of
correlated one-dimensional systems in the presence of non-magnetic impurities.
The dynamical spin structure factor for a corresponding random ensemble of
Heisenberg chain segments is calculated by exact numerical diagonalization. It
is shown that a few-pole approximation is sufficient to describe the numerical
results. A similar analysis is proposed for the discussion of experimental
spectra, such as obtained by inelastic neutron scattering measurements on
Zn-doped CuO chains. By examination of the disorder-induced pseudo-gap, the
loss of spectral weight, and the discrete peak structures due to
smallest-cluster contributions, the underlying impurity distribution function
can be determined.Comment: RevTex, 4 pages with 4 eps figure
The Central Region in M100: Observations and Modeling
We present new high-resolution observations of the center of the late-type
spiral M100 (NGC 4321) supplemented by 3D numerical modeling of stellar and gas
dynamics, including star formation (SF). NIR imaging has revealed a stellar
bar, previously inferred from optical and 21 cm observations, and an
ovally-shaped ring-like structure in the plane of the disk. The K isophotes
become progressively elongated and skewed to the position angle of the bar
(outside and inside the `ring') forming an inner bar-like region. The galaxy
exhibits a circumnuclear starburst in the inner part of the K `ring'. Two
maxima of the K emission have been observed to lie symmetrically with respect
to the nucleus and equidistant from it slightly leading the stellar bar. We
interpret the twists in the K isophotes as being indicative of the presence of
a double inner Lindblad resonance (ILR) and test this hypothesis by modeling
the gas flow in a self-consistent gas + stars disk embedded in a halo, with an
overall NGC4321-like mass distribution. We have reproduced the basic morphology
of the region (the bar, the large scale trailing shocks, two symmetric K peaks
corresponding to gas compression maxima which lie at the caustic formed by the
interaction of a pair of trailing and leading shocks in the vicinity of the
inner ILR, both peaks being sites of SF, and two additional zones of SF
corresponding to the gas compression maxima, referred usually as `twin peaks').Comment: 31 pages, postscript, compressed, uuencoded. 21 figures available in
postscript, compressed form by anonymous ftp from
ftp://asta.pa.uky.edu/shlosman/main100 , mget *.ps.Z. To appear in Ap.
The central region of M83: Massive star formation, kinematics, and the location and origin of the nucleus
We report new near-IR integral field spectroscopy of the central starburst
region of the barred spiral galaxy M83 obtained with CIRPASS on Gemini-S, which
we analyse in conjunction with GHaFaS Fabry-Perot data, an AAT IRIS2 Ks-band
image, and near- and mid-IR imaging from the Hubble and Spitzer space
telescopes. The bulk of the current star formation activity is hidden from
optical view by dust extinction, but is seen in the near- and mid-IR to the
north of the nucleus. This region is being fed by inflow of gas through the bar
of M83, traced by the prominent dust lane entering into the circumnuclear
region from the north. An analysis of stellar ages confirms that the youngest
stars are indeed in the northwest. A gradual age gradient, with older stars
further to the south, characterises the well-known star-forming arc in the
central region of M83. Detailed analyses of the Pa beta ionised gas kinematics
and near-IR imaging confirm that the kinematic centre coincides with the
photometric centre of M83, and that these are offset significantly, by about 3
arcsec or 60 pc, from the visible nucleus of the galaxy. We discuss two
possible options, the first of which postulates that the kinematic and
photometric centre traces a galaxy nucleus hidden by a substantial amount of
dust extinction, in the range A_V=3-10 mag. By combining this information with
kinematic results and using arguments from the literature, we conclude that
such a scenario is, however, unlikely, as is the existence of other "hidden"
nuclei in M83. We thus concur with recent authors and favour a second option,
in which the nucleus of the galaxy is offset from its kinematic and photometric
centre. This is presumably a result of some past interaction, possibly related
to the event which lies at the origin of the disturbance of the outer disk of
the galaxy. (Abridged)Comment: MNRAS, in press; 16 pages latex, 15 figure
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