4,053 research outputs found
Kinematics and morphology of ionized gas in Hickson Compact Group 18
We present new observations of emission in the Hickson Compact
Group 18 (HCG 18) obtained with a scanning Fabry-Perot interferometer. The
velocity field does not show motions of individual group members but, instead,
a complex common velocity field for the whole group. The gas distribution is
very asymmetric with clumps of maximum intensity coinciding with the optically
brightest knots. Comparing and HI data we conclude that HCG 18 is
not a compact group but instead a large irregular galaxy with several clumps of
star formation.Comment: Accepted for publication in Astronomical Journal (13p 6 figures
A Dynamical Study of Galaxies in the Hickson Compact Groups
In order to investigate dynamical properties of spiral galaxies in the
Hickson compact groups (HCGs), we present rotation curves of 30 galaxies in 20
HCGs. We found as follows. 1) There is not significant relation between
dynamical peculiarity and morphological peculiarity in HCG spirals. 2) There is
no significant relation between the dynamical properties and the frequency
distribution of nuclear activities in HCG spirals. 3) There are no significant
correlations between the dynamical properties of HCG spirals and any group
properties (i.e., the size, the velocity dispersion, the galaxy number density,
and the crossing time). 4) Asymmetric and peculiar rotation curves are more
frequently seen in the HCG spirals than in field spirals and in cluster ones.
However, this tendency is more obviously seen in late-type HCG spirals. These
results suggest that the dynamical properties of HCG spirals do not strongly
correlate with the morphology, the nuclear activity, and the group properties.
Our results also suggest that more frequent galaxy collisions occur in the HCGs
than in the field and in the clusters.Comment: 24 pages test (aasms4 LaTeX), 50 page tables (aasms4 LaTeX), and 16
Postscript figures, Accepted for The Astronomical Journa
Dynamics of blue compact galaxies, as revealed by their H-alpha velocity fields I. The data, velocity fields and rotation curves
Observations of six luminous blue compact galaxies (BCGs) and two star
forming companion galaxies were carried out with the CIGALE scanning
Fabry-Perot interferometer attached to the ESO 3.6m telescope on La Silla. The
observations were made in the H-alpha emission line which is prominent in BCGs.
A velocity sampling of 5 km/s and a pixel size of 0.9 arcseconds were used. In
this paper we present the observations and the data together with the velocity
fields and the derived rotation curves. In addition we provide rough estimates
of the total dynamical mass and of the ionised gas mass for each galaxy. All
galaxies display rotation, but while the companion galaxies have regular
velocity fields, those of the BCGs are complex and appear perturbed. This is
the most extensive study to date of the optical velocity fields of BCGs. The
interpretation of these results will be presented in a forthcoming paper (Paper
II).Comment: 26 pages, 14 figures. Accepted for publication in A&AS. The paper
(with figures in slightly higher resolution) and an electronic table is also
available at ftp://ftp.iap.fr/pub/from_users/ostlin/Articles/ . Replaced
version, figure captions fixe
Accurate Determination of the Mass Distribution in Spiral Galaxies: II. Testing the Shape of Dark Halos
New high resolution CFHT Fabry-Perot data, combined with published VLA 21 cm
observations are used to determine the mass distribution of NGC 3109 and IC
2574. The multi-wavelength rotation curves allow to test with confidence
different dark halo functional forms from the pseudo-isothermal sphere to some
popular halo distributions motivated by N-body simulations. It appears that
density distribution with an inner logarithmic slope <= -1 are very hard to
reconcile with rotation curves of late type spirals. Modified Newtonian
Dynamics (MOND) is also considered as a potential solution to missing mass and
tested the same way. The new higher resolution data show that MOND can
reproduce in details the rotation curve of IC 2574 but confirm its difficulty
to fit the kinematics of NGC 3109.Comment: 28 pages, accepted by AJ. New HI profile increases the compatibility
of NGC 3109 rotation curve with MON
VLT/MUSE view of the highly ionized outflow cones in the nearby starburst ESO338-IG04
The Ly line is an important diagnostic for star formation at high
redshift, but interpreting its flux and line profile is difficult because of
the resonance nature of Ly. Trends between the escape of Ly
photons and dust and properties of the interstellar medium (ISM) have been
found, but detailed comparisons between Ly emission and the properties
of the gas in local high-redshift analogs are vital for understanding the
relation between Ly emission and galaxy properties. For the first time,
we can directly infer the properties of the ionized gas at the same location
and similar spatial scales of the extended Ly halo around ESO 338-IG04.
We obtained VLT/MUSE integral field spectra. We used ionization parameter
mapping of the [SII]/[OIII] line ratio and the kinematics of H to study
the ionization state and kinematics of the ISM of ESO338-IG04. The velocity map
reveals two outflows. The entire central area of the galaxy is highly ionized
by photons leaking from the HII regions around the youngest star clusters.
Three highly ionized cones have been identified, of which one is associated
with an outflow. We propose a scenario where the outflows are created by
mechanical feedback of the older clusters, while the highly ionized gas is
caused by the hard ionizing photons emitted by the youngest clusters. A
comparison with the Ly map shows that the (approximately bipolar)
asymmetries observed in the Ly emission are consistent with the base of
the outflows detected in H. No clear correlation with the ionization
cones is found. The mechanical and ionization feedback of star clusters
significantly changes the state of the ISM by creating ionized cones and
outflows. The comparison with Ly suggests that especially the outflows
could facilitate the escape of Ly photons [Abridged].Comment: Accepted for publication in A&A Letters, 4 pages, 2 figure
On the Mailbox Problem
The Mailbox Problem was described and solved by Aguilera, Gafni, and Lamport
in their 2010 DC paper with an algorithm that uses two flag registers that
carry 14 values each. An interesting problem that they ask is whether there is
a mailbox algorithm with smaller flag values. We give a positive answer by
describing a mailbox algorithm with 6 and 4 values in the two flag registers
Chandra Observations of "The Antennae" Galaxies (NGC 4038/39)
We report the results of a deep Chandra ACIS pointing at the merging system
NGC 4038/39. We detect an extraordinarily luminous population of X-ray sources,
with luminosity well above that of XRBs in M31 and the Milky Way. If these
sources are unbeamed XRBs, our observations may point to them being 10-100Mo
black hole counterparts. We detect an X-ray bright hot ISM, with features
including bright superbubbles associated with the actively star-forming knots,
regions where hot and warm (H) ISM intermingle, and a large-scale
outflow.Comment: 7 pages, 10 figures, Accepted for publication in Ap
Development of Combined Opto-Acoustical Sensor Modules
The faint fluxes of cosmic neutrinos expected at very high energies require
large instrumented detector volumes. The necessary volumes in combination with
a sufficient shielding against background constitute forbidding and complex
environments (e.g. the deep sea) as sites for neutrino telescopes. To withstand
these environments and to assure the data quality, the sensors have to be
reliable and their operation has to be as simple as possible. A compact sensor
module design including all necessary components for data acquisition and
module calibration would simplify the detector mechanics and ensures the long
term operability of the detector. The compact design discussed here combines
optical and acoustical sensors inside one module, therefore reducing
electronics and additional external instruments for calibration purposes. In
this design the acoustical sensor is primary used for acoustic positioning of
the module. The module may also be used for acoustic particle detection and
marine science if an appropriate acoustical sensor is chosen.
First tests of this design are promising concerning the task of calibration.
To expand the field of application also towards acoustic particle detection
further improvements concerning electromagnetic shielding and adaptation of the
single components are necessary.Comment: 4 pages, 2 figures, ARENA2010 proceeding
- …