119 research outputs found
Detection of Carbon Monoxide within the Magellanic Bridge
The Mopra 22m and SEST 15m telescopes have been used to detect and partially
map a region of 12CO(1-0) line emission within the Magellanic Bridge, a region
lying between the Large and Small Magellanic Clouds. The emission appears to be
embedded in a cloud of neutral hydrogen, and is in the vicinity of an IRAS
source. The CO emission region is found to have a 60um/100um flux density ratio
typical for 12CO(1-0) detections within the SMC, although it has a
significantly lower 12CO brightness and velocity width. These suggest that the
observed region is of a low metallicity, supporting earlier findings that the
Magellanic Bridge is not as evolved as the SMC and Magellanic Stream, which are
themselves of a lower metallicity than the Galaxy. Our observations, along with
empirical models based on SMC observations, indicate that the radius of the
detected CO region has an upper limit of ~16 pc. This detection is, to our
knowledge, the first detection of CO emission from the Magellanic Bridge and is
the only direct evidence of star formation through molecular cloud collapse in
this region.Comment: 8 pages, 6 Figures. LaTeX. Accepted for publication by MNRA
Multifibre spectroscopy of the supernova remnant candidate RCW 114
RCW 114 is a filamentary nebula of about 250 arcmin diameter. Based on its large diameter-to-filament-width ratio, the expansion velocity, distance and size of the shell, it has been suggested that RCW 114 is a supernova remnant in its momentum-conserving phase. Confirmation of this identification is important, as the large angular size and extensive optical emission of this object will allow for detailed study to improve our knowledge of supernova remnants and their interaction with the interstellar medium.
We have used the FLAIR instrument on the UK Schmidt Telescope to obtain optical spectra of several filaments in RCW 114. These confirm that the emission is being produced by the interaction of the shock wave of a supernova remnant with the surrounding interstellar medium. We also obtained narrow-band Hα+[N ii] and [S ii] images to examine the spatial variation in ionization structure
The 3-Dimensional Structure of HH 32 from GMOS IFU Spetroscopy
We present new high resolution spectroscopic observations of the Herbig-Haro
object HH 32 from System Verification observations made with the GMOS IFU at
Gemini North Observatory. The 3D spectral data covers a 8''.7 x 5''.85 spatial
field and 4820 - 7040 Angstrom spectral region centered on the HH~32 A knot
complex. We show the position-dependent line profiles and radial velocity
channel maps of the Halpha line, as well as line ratio velocity channel maps of
[OIII]5007/Halpha, [OI]6300/Halpha, [NII]6583/Halpha, [SII](6716+6730)/Halpha
and [SII]6716/6730. We find that the line emission and the line ratios vary
significantly on spatial scales of ~1'' and over velocities of ~50 km/s. A
``3/2-D'' bow shock model is qualitatively successful at reproducing the
general features of the radial velocity channel maps, but it does not show the
same complexity as the data and it fails to reproduce the line ratios in our
high spatial resolution maps. The observations of HH 32 A show two or three
superimposed bow shocks with separations of ~3'', which we interpret as
evidence of a line of sight superposition of two or three working surfaces
located along the redshifted body of the HH 32 outflow.Comment: Accepted for Publication in the Astronomical Journal (January 2004
Enigma of ultraluminous X-ray sources may be resolved by 3D-spectroscopy (MPFS data)
The ultraluminous X-ray sources (ULXs) were isolated in external galaxies for
the last 5 years. Their X-ray luminosities exceed 100-10000 times those of
brightest Milky Way black hole binaries and they are extremely variable. There
are two models for the ULXs, the best black hole candidates. 1. They are
supercritical accretion disks around a stellar mass black hole like that in
SS433, observed close to the disk axes. 2. They are Intermediate Mass Black
Holes (of 100-10000 solar masses). Critical observations which may throw light
upon the ULXs nature come from observations of nebulae around the ULXs. We
present results of 3D-spectroscopy of nebulae around several ULXs located in
galaxies at 3-6 Mpc distances. We found that the nebulae to be powered by their
central black holes. The nebulae are shocked and dynamically perturbed probably
by jets. The nebulae are compared with SS433 nebula (W50).Comment: Proceedings of the ESO and Euro3D Workshop "Science Perspectives for
3D Spectroscopy", Garching (Germany), October 10-14, 2005. M. Kissler-Patig,
M.M. Roth and J.R. Walsh (eds.
Jet-Induced Nucleosynthesis in Misaligned Microquasars
The jet axes and the orbital planes of microquasar systems are usually
assumed to be approximately perpendicular, eventhough this is not currently an
observational requirement. On the contrary, in one of the few systems where the
relative orientations are well-constrained, V4641Sgr, the jet axis is known to
lie not more than ~36 degrees from the binary plane. Such a jet, lying close to
the binary plane, and traveling at a significant fraction of the speed of light
may periodically impact the secondary star initiating nuclear reactions on its
surface. The integrated yield of such nuclear reactions over the age of the
binary system (less the radiative mass loss) will detectably alter the
elemental abundances of the companion star. This scenario may explain the
anomalously high Li enhancements (roughly ~20-200 times the sun's photospheric
value; or, equivalently, 0.1-1 times the average solar system value) seen in
the companions of some black-hole X-ray binary systems. (Such enhancements are
puzzling since Li nuclei are exceedingly fragile - being easily destroyed in
the interiors of stars - and Li would be expected to be depleted rather than
enhanced there.) Gamma-ray line signatures of the proposed process could
include the 2.22 MeV neutron capture line as well as the 0.478 MeV 7Li*
de-excitation line, both of which may be discernable with the INTEGRAL
satellite if produced in an optically thin region during a large outburst. For
very energetic jets, a relatively narrow neutral pion gamma-decay signature at
67.5 MeV could also be measurable with the GLAST satellite. We argue that about
10-20% of all microquasar systems ought to be sufficiently misaligned as to be
undergoing the proposed jet-secondary impacts.Comment: ApJ, accepted. Includes referee's suggestions and some minor
clarifications over previous versio
The Eastern Filament of W50
We present new spectral (FPI and long-slit) data on the Eastern optical
filament of the well known radionebula W50 associated with SS433. We find that
on sub-parsec scales different emission lines are emitted by different regions
with evidently different physical conditions. Kinematical properties of the
ionized gas show evidence for moderately high (V ~ 100 km/s) supersonic
motions. [OIII]5007 emission is found to be multi-component and differs from
lower-excitation [SII]6717 line both in spatial and kinematical properties.
Indirect evidence for very low characteristic densities of the gas (n ~
0.1cm^{-3}) is found. We propose radiative (possibly incomplete) shock waves in
low-density, moderately high metallicity gas as the most probable candidate for
the power source of the optical filament. Apparent nitrogen over-abundance is
better understood if the location of W50 in the Galaxy is taken into account.Comment: accepted to Astronomische Nachrichten; 9 pages, 4 figures, 2 table
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