290 research outputs found
Discovery of optical candidate supernova remnants in Sagittarius
During an [O III] survey for planetary nebulae, we identified a region in
Sagittarius containing several candidate Supernova Remnants and obtained deep
optical narrow-band images and spectra to explore their nature. The images of
the unstudied area have been obtained in the light of Halpha+[N II], [S II] and
[O III]. The resulting mosaic covers an area of 1.4x1.0 deg^2 where filamentary
and diffuse emission was discovered, suggesting the existence of more than one
supernova remnants (SNRs) in the area. Deep long slit spectra were also taken
of eight different regions. Both the flux calibrated images and the spectra
show that the emission from the filamentary structures originates from
shock-heated gas, while the photo-ionization mechanism is responsible for the
diffuse emission. Part of the optical emission is found to be correlated with
the radio at 4850 MHz suggesting their association, while the WISE infrared
emission found in the area at 12 and 22 micron marginally correlates with the
optical. The presence of the [O III] emission line in one of the candidate SNRs
suggests shock velocities into the interstellar "clouds" between 120 and 200
km/s, while the absence in the other indicates slower shock velocities. For all
candidate remnants the [S II] 6716/6731 ratio indicates electron densities
below 240 cm^{-3}, while the Halpha emission has been measured to be between
0.6 to 41x10^{-17} erg/s/cm^2/arcsec^2. The existence of eight pulsars within
1.5deg away from the center of the candidate SNRs also supports the scenario of
many SNRs in the area as well as that the detected optical emission could be
part of a number of supernovae explosions.Comment: 15 pages, 6 figures, accepted for publication in Astronomy &
Astrophysic
Deep Halpha imagery of the Eridanus shells
A deep \ha image of interlocking filamentary arcs of nebulosity has been
obtained with a wide-field ( 30\degree diameter) narrow-band filter
camera combined with a CCD as a detector. The resultant mosaic of images,
extending to a galactic latitude of 65, has been corrected for field
distortions and had galactic coordinates superimposed on it to permit accurate
correlations with the most recent H{\sc i} (21 cm), X-ray (0.75 kev) and FIR
(IRAS 100 m) maps.
Furthermore, an upper limit of 0.13 arcsec/yr to the expansion proper motion
of the primary 25\degree long nebulous arc has been obtained by comparing a
recent \ha image obtained with the San Pedro Martir telescope of its
filamentary edge with that on a POSS E plate obtained in 1951.
It is concluded that these filamentary arcs are the superimposed images of
separate shells (driven by supernova explosions and/or stellar winds) rather
than the edges of a single `superbubble' stretching from Barnard's Arc (and the
Orion Nebula) to these high galactic latitudes. The proper motion measurement
argues against the primary \ha emitting arc being associated with the giant
radio loop (Loop 2) except in extraordinary circumstances.Comment: 9 pages, 5 figures, accepted for MNRAS publicatio
Reducing Communication Overhead and Page Faults in SDSM Platforms
Abstract. In this paper we present a new dynamic, cache coherence protocol for Software Distributed Shared Memory (SDSM) systems that adopt the scope-consistency mode
Column classification/characterisation of strong cation exchange phases for the liquid chromatographic analysis of small molecular weight bases
A simple, rapid and robust protocol for the characterisation of strong cation exchange columns for the analysis of small molecular weight bases is described. A range of ten different phases were characterised, and the resultant selectivity and retention factors analysed using Principal Component Analysis. The score plots for the first and second principal components described 83% of the variability within the dataset. Score plots highlighted the large chromatographic differences observed between the phases, the validity of which was established using a larger range of bases. All the strong cation exchange materials demonstrated a synergistic mixed mode (i.e. ion exchange and hydrophobic) retention mechanism. Principal Component Analysis also highlighted the potential difficulty in locating suitable strong cation exchange âback-upâ columns for the analysis of small molecular weight bases in that the characterised columns all displayed very different selectivities. The robustness of the protocol was confirmed by a factorial design experiment
IPR Law Protection and Enforcement and the Effect on Horizontal Productivity Spillovers from Inward FDI to Domestic Firms: A Meta-Analysis
YesWe study the role of the strength of Intellectual Property Rights (IPR) law protection and enforcement in influencing horizontal productivity spillovers from inward FDI to domestic firms in host countries. While most WTO countries adopted strong IPR legislation due to exogenous pressure resulting from the signing of the Trade-Related Aspects of IPR (TRIPS) agreement, public IPR enforcement strength continues to vary significantly between countries. We meta-analyse 49 studies and find that public IPR enforcement strength has a direct positive effect on horizontal productivity spillovers from inward FDI to domestic firms and a negative moderating effect on the relationship between IPR law protection strength and horizontal productivity spillovers from inward FDI to domestic firms
Spectroscopic Properties of QSOs Selected from Ultraluminous Infrared Galaxy Samples
We performed spectroscopic observations for a large infrared QSO sample with
a total of 25 objects. The sample was compiled from the QDOT redshift survey,
the 1 Jy ULIRGs survey and a sample obtained by a cross-correlation study of
the IRAS Point Source Catalogue with the ROSAT All Sky Survey Catalogue.
Statistical analyses of the optical spectra show that the vast majority of
infrared QSOs have narrow permitted emission lines (with FWHM of Hbeta less
than 4000 km/s) and more than 60% of them are luminous narrow line Seyfert 1
galaxies. Two of the infrared QSOs are also classified as low ionization BAL
QSOs. More than 70% of infrared QSOs are moderately or extremely strong Fe II
emitters. This is the highest percentage of strong Fe II emitters in all
subclasses of QSO/Seyfert 1 samples. We found that the Fe II to Hbeta, line
ratio is significantly correlated with the [OIII]5007 peak and Hbeta blueshift.
Soft X-ray weak infrared QSOs tend to have large blueshifts in permitted
emission lines and significant Fe II48,49 (5100--5400 A) residuals relative to
the Boroson & Green Fe II template. If the blueshifts in permitted lines are
caused by outflows, then they appear to be common in infrared QSOs. As the
infrared-selected QSO sample includes both luminous narrow line Seyfert 1
galaxies and low ionization BAL QSOs, it could be a useful laboratory to
investigate the evolutionary connection among these objects.Comment: 35 pages,14 figures, 4 tables, accepted for publication in A
The Asymmetric Wind in M82
We have obtained detailed imaging Fabry-Perot observations of the nearby
galaxy M82, in order to understand the physical association between the
high-velocity outflow and the starburst nucleus. The observed velocities of the
emitting gas in M82 reveal a bipolar outflow of material, originating from the
bright starburst regions in the galaxy's inner disk, but misaligned with
respect to the galaxy spin axis. The deprojected outflow velocity increases
with radius from 525 to 655 km/s. Spectral lines show double components in the
centers of the outflowing lobes, with the H-alpha line split by ~300 km/s over
a region almost a kiloparsec in size. The filaments are not simple surfaces of
revolution, nor is the emission distributed evenly over the surfaces. We model
these lobes as a composite of cylindrical and conical structures, collimated in
the inner ~500 pc but expanding at a larger opening angle of ~25 degrees beyond
that radius. We compare our kinematic model with simulations of
starburst-driven winds in which disk material surrounding the source is
entrained by the wind. The data also reveal a remarkably low [NII]/H-alpha
ratio in the region of the outflow, indicating that photoionization by the
nuclear starburst may play a significant role in the excitation of the optical
filament gas, particularly near the nucleus.Comment: 42 pages AASTeX with 16 figures; accepted for publication in ApJ;
figures reformatted for better printin
HST Observations of the Double-Peaked Emission Lines in the Seyfert Galaxy Markarian 78: Mass Outflows from a Single AGN
Previous ground based observations of the Seyfert 2 galaxy Mrk 78 revealed a
double set of emission lines, similar to those seen in several AGN from recent
surveys. Are the double lines due to two AGN with different radial velocities
in the same galaxy, or are they due to mass outflows from a single AGN?We
present a study of the outflowing ionized gas in the resolved narrow-line
region (NLR) of Mrk 78 using observations from Space Telescope Imaging
Spectrograph (STIS) and Faint Object Camera (FOC) aboard the Hubble Space
Telescope(HST) as part of an ongoing project to determine the kinematics and
geometries of active galactic nuclei (AGN) outflows. From the spectroscopic
information, we deter- mined the fundamental geometry of the outflow via our
kinematics modeling program by recreating radial velocities to fit those seen
in four different STIS slit positions. We determined that the double emission
lines seen in ground-based spectra are due to an asymmetric distribution of
outflowing gas in the NLR. By successfully fitting a model for a single AGN to
Mrk 78, we show that it is possible to explain double emission lines with
radial velocity offsets seen in AGN similar to Mrk 78 without requiring dual
supermassive black holes.Comment: 22 pages, 7 figures (2 color), accepted for publication in The
Astrophysical Journa
Evidence for an outflow from the Seyfert galaxy NGC 4051
New observations using narrow band imaging, long-slit spectroscopy and MERLIN
observations of the nuclear region of the Seyfert galaxy NGC~4051 have been
made. An edge brightened, triangular region of ionized gas extending 420 pc
from the centre of the galaxy has been detected. Long-slit spectra of this
ionised gas, taken at 1.5\arcsec\ from the core, show the \oiii\ emission line
to consist of two velocity components, both blue-shifted from the systemic
radial velocity, with velocity widths of 140\kms\ and separated by 120\kms.
This region is co-spatial with weak extended radio emission and is suggestive
of a centrally driven outflow. The \oiii\ line spectrum and image of this
region have been modelled as an outflowing conical structure at 50\degr\ to the
line of sight with a half opening angle of 23\degr .
In addition to the extended structure, high resolution MERLIN observations of
the 18-cm nuclear radio emission reveal a compact (1\arcsec) radio triple
source in PA 73. This source is coincident with the HST-imaged
emission line structure. These high resolution observations are consistent with
a more compact origin of activity (i.e. a Seyfert nucleus) than a starburst
region.Comment: latex, epsf.sty, 8 pages, 8 figures. Also available at
http://axp2.ast.man.ac.uk:8000/Preprints.htm
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