37 research outputs found
Newly discovered halos and outer features around southern planetary nebulae
We have used the SuperCOSMOS H-alpha Survey to look for faint outer
structures such as halos, ansae and jets around known planetary nebulae across
4000 square degrees of the southern Milky Way. Our search will contribute to a
more accurate census of these features in the Galactic PN population. Candidate
common-envelope PNe have also been identified on the basis of their
microstructures. We also intend to determine more reliable distances for these
PNe, which should allow a much better statistical basis for the post-AGB total
mass budget. Our survey offers fresh scope to address this important issue.Comment: 2 pages, 1 figure. To be published in Planetary Nebulae: an Eye to
the Future, Proceedings of IAU Symposium 283, held in Puerto de la Cruz,
Tenerife, Spain, July 25-29 201
Radio Planetary Nebulae in the Small Magellanic Cloud
We present ten new radio continuum (RC) detections at catalogued planetary
nebula (PN) positions in the Small Magellanic Cloud (SMC): SMPS6, LIN 41, LIN
142, SMP S13, SMP S14, SMP S16, J18, SMP S18, SMP S19 and SMP S22.
Additionally, six SMC radio PNe previously detected, LIN 45, SMP S11, SMPS17,
LIN321, LIN339 and SMPS24 are also investigated (re-observed) here making up a
population of 16 radio detections of catalogued PNe in the SMC. These 16 radio
detections represent ~15 % of the total catalogued PN population in the SMC. We
show that six of these objects have characteristics that suggest that they are
PN mimics: LIN 41, LIN 45, SMP S11, LIN 142, LIN 321 and LIN 339. We also
present our results for the surface brightness - PN radius relation
({\Sigma}-D) of the SMC radio PN population. These are consistent with previous
SMC and LMC PN measurements of the ({\Sigma}-D) relation.Comment: Accepted for publication in Astrophysics and Space Scienc
Radio Planetary Nebulae in the Magellanic Clouds
We present preliminary results of our deep Australia Telescope Compact Array
(ATCA) radio-continuum survey of the Magellanic Clouds Planetary Nebulae.Comment: 2 pages 1 figure, to appear in Planetary Nebulae an Eye to the Future
Proceedings IAU Symposium No. 28
First release of the IPHAS catalogue of new extended planetary nebulae
Date of Acceptance: 30/06/2014We present the first results of our search for new, extended planetary nebulae (PNe) based on careful, systematic, visual scrutiny of the imaging data from the Isaac Newton Telescope Photometric Ha Survey of the Northern Galactic plane (IPHAS). The newly uncovered PNe will help to improve the census of this important population of Galactic objects that serve as key windows into the late-stage evolution of low- to intermediate-mass stars. They will also facilitate study of the faint end of the ensemble Galactic PN luminosity function. The sensitivity and coverage of IPHAS allows PNe to be found in regions of greater extinction in the Galactic plane and/or those PNe in a more advanced evolutionary state and at larger distances compared to the general Galactic PN population. Using a set of newly revised optical diagnostic diagrams in combination with access to a powerful, new, multiwavelength imaging data base, we have identified 159 true, likely and possible PNe for this first catalogue release. The ability of IPHAS to unveil PNe at low Galactic latitudes and towards the Galactic Anticentre, compared to previous surveys, makes this survey an ideal tool to contribute to the improvement of our knowledge of the whole Galactic PN population.Peer reviewe
Multi-wavelength study of a new Galactic SNR G332.5-5.6
We present compelling evidence for confirmation of a Galactic supernova
remnant (SNR) candidate, G332.5-5.6, based initially on identification of new,
filamentary, optical emission line nebulosity seen in the arcsecond resolution
images from the AAO/UKST HAlpha survey. The extant radio observations and X-ray
data which we have independently re-reduced, together with new optical
spectroscopy of the large-scale fragmented nebulosity, confirms the
identification. Optical spectra, taken across five different, widely separated
nebula regions of the remnant as seen on the HAlpha images, show average ratios
of [NII]/HAlpha =2.42, [SII]/HAlpha = 2.10, and [SII] 6717/6731 = 1.23, as well
as strong [OI] 6300, 6364A and [OII] 3727A emission. These ratios are firmly
within those typical of SNRs. Here, we also present the radio-continuum
detection of the SNR at 20/13cm from observations with the Australia Telescope
Compact Array (ATCA). Radio emission is also seen at 4850 MHz, in the PMN
survey (Griffith and Wright 1993) and at 843 MHz from the SUMSS survey (Bock,
Large and Sadler 1999). We estimate an angular diameter of ~30 arcmin and
obtain an average radio spectral index of alpha = -0.6 +- 0.1 which indicates
the non-thermal nature of G332.5-5.6. Fresh analysis of existing ROSAT X-ray
data in the vicinity also confirms the existence of the SNR. The distance to
G332.5-5.6 has been independently estimated by Reynoso and Green (2007) as 3.4
kpc based on measurements of the HI lambda21 cm line seen in absorption against
the continuum emission. Our cruder estimates via assumptions on the height of
the dust layer (3.1 kpc) and using the Sigma-D relation (4 kpc) are in good
agreement.Comment: 14 pages, 18 figures. Accepted for publishing in the MNRA
Multi-frequency Study of the LMC Supernova Remnant (SNR) B0513-692 and New SNR Candidate J051327-6911
We present a new multi-wavelength study of supernova remnant (SNR) B0513-692
in the Large Magellanic Cloud (LMC). The remnant also has a strong, superposed,
essentially unresolved, but unrelated radio source at its north-western edge,
J051324-691049. This is identified as a likely compact HII region based on
related optical imaging and spectroscopy. We use the Australia Telescope
Compact Array (ATCA) at 4790 and 8640 MHz to determine the large scale
morphology, spectral index and polarization characteristics of B0513-692 for
the first time. We detect a strongly polarized region (49%) in the remnant's
southern edge. Interestingly we also detect a small (~40 arcsec) moderately
bright, but distinct optical, circular shell in our Halpha imagery which is
adjacent to the compact HII region and just within the borders of the NE edge
of B0513-692. We suggest this is a separate new SNR candidate based on its
apparently distinct character in terms of optical morphology in 3 imaged
emission lines and indicative SNR optical spectroscopy (including enhanced
optical [SII] emission relative to Halpha).Comment: 12 page
Murchison Widefield Array and XMM-Newton observations of the Galactic supernova remnant G5.9+3.1
In this paper we discuss the radio continuum and X-ray properties of the
so-far poorly studied Galactic supernova remnant (SNR) G5.9+3.1. We present the
radio spectral energy distribution (SED) of the Galactic SNR G5.9+3.1 obtained
with the Murchison Widefield Array (MWA). Combining these new observations with
the surveys at other radio continuum frequencies, we discuss the integrated
radio continuum spectrum of this particular remnant. We have also analyzed an
archival XMM-Newton observation, which represents the first detection of X-ray
emission from this remnant. The SNR SED is very well explained by a simple
power-law relation. The synchrotron radio spectral index of G5.9+3.1, is
estimated to be 0.420.03 and the integrated flux density at 1GHz to be
around 2.7Jy. Furthermore, we propose that the identified point radio source,
located centrally inside the SNR shell, is most probably a compact remnant of
the supernova explosion. The shell-like X-ray morphology of G5.9+3.1 as
revealed by XMM-Newton broadly matches the spatial distribution of the radio
emission, where the radio-bright eastern and western rims are also readily
detected in the X-ray while the radio-weak northern and southern rims are weak
or absent in the X-ray. Extracted MOS1+MOS2+PN spectra from the whole SNR as
well as the north, east, and west rims of the SNR are fit successfully with an
optically thin thermal plasma model in collisional ionization equilibrium with
a column density N_H~0.80x cm and fitted temperatures spanning
the range kT~0.14-0.23keV for all of the regions. The derived electron number
densities n_e for the whole SNR and the rims are also roughly comparable
(ranging from ~ cm to ~ cm, where f
is the volume filling factor). We also estimate the swept-up mass of the X-ray
emitting plasma associated with G5.9+3.1 to be ~.Comment: Accepted for publication in A&
XMMU J0541.8-6659, a new supernova remnant in the Large Magellanic Cloud
The high sensitivity of the XMM-Newton instrumentation offers the opportunity
to study faint and extended sources in the Milky Way and nearby galaxies such
as the Large Magellanic Cloud (LMC) in detail. The ROSAT PSPC survey of the LMC
has revealed more than 700 X-ray sources, among which there are 46 supernova
remnants (SNRs) and candidates. We have observed the field around one of the
most promising SNR candidates in the ROSAT PSPC catalogue, labelled [HP99] 456
with XMM-Newton, to determine its nature. We investigated the XMM-Newton data
along with new radio-continuum, near infrared and optical data. In particular,
spectral and morphological studies of the X-ray and radio data were performed.
The X-ray images obtained in different energy bands reveal two different
structures. Below 1.0 keV the X-ray emission shows the shell-like morphology of
an SNR with a diameter of ~73 pc, one of the largest known in the LMC. For its
thermal spectrum we estimate an electron temperature of (0.49 +/- 0.12)keV
assuming non-equilibrium ionisation. The X-ray images above 1.0 keV reveal a
less extended source within the SNR emission, located ~1' west of the centre of
the SNR and coincident with bright point sources detected in radio-continuum.
This hard component has an extent of 0.9' (i.e. ~13 pc at a distance of ~50
kpc) and a non-thermal spectrum. The hard source coincides in position with the
ROSAT source [HP99] 456 and shows an indication for substructure. We firmly
identify a new SNR in the LMC with a shell-like morphology and a thermal
spectrum. Assuming the SNR to be in the Sedov phase yields an age of ~23 kyr.
We explore possible associations of the hard non-thermal emitting component
with a pulsar wind nebula (PWN) or background active galactic nuclei (AGN).Comment: 8 pages, 7 figures, accepted for publication in Astronomy and
Astrophysic
Multi-frequency study of DEM L299 in the Large Magellanic Cloud
We have studied the HII region DEM L299 in the Large Magellanic Cloud to
understand its physical characteristics and morphology in different
wavelengths. We performed a spectral analysis of archived XMM-Newton EPIC data
and studied the morphology of DEM L299 in X-ray, optical, and radio
wavelengths. We used H alpha, [SII], and [OIII] data from the Magellanic Cloud
Emission Line Survey and radio 21 cm line data from the Australia Telescope
Compact Array (ATCA) and the Parkes telescope, and radio continuum data from
ATCA and the Molonglo Synthesis Telescope. Our morphological studies imply
that, in addition to the supernova remnant SNR B0543-68.9 reported in previous
studies, a superbubble also overlaps the SNR in projection. The position of the
SNR is clearly defined through the [SII]/H alpha flux ratio image. Moreover,
the optical images show a shell-like structure that is located farther to the
north and is filled with diffuse X-ray emission, which again indicates the
superbubble. Radio 21 cm line data show a shell around both objects. Radio
continuum data show diffuse emission at the position of DEM L299, which appears
clearly distinguished from the HII region N 164 that lies south-west of it. We
determined the spectral index of SNR B0543-68.9 to be alpha=-0.34, which
indicates the dominance of thermal emission and therefore a rather mature SNR.
We determined the basic properties of the diffuse X-ray emission for the SNR,
the superbubble, and a possible blowout region of the bubble, as suggested by
the optical and X-ray data. We obtained an age of 8.9 (3.5-18.1) kyr for the
SNR and a temperature of 0.64 (0.44-1.37) keV for the hot gas inside the SNR,
and a temperature of the hot gas inside the superbubble of 0.74 (0.44-1.1) keV.
We conclude that DEM L299 consists of a superposition of SNR B0543-68.9 and a
superbubble, which we identified based on optical data.Comment: Accepted for publication in Astronomy and Astrophysics. 17 pages, 16
figure
Multi-wavelength diagnostic properties of Galactic Planetary Nebulae detected by GLIMPSE-I
We uniformly analyze 136 optically detected PNe and candidates from the
GLIMPSE-I survey in order to to develop robust, multi-wavelength,
classification criteria to augment existing diagnostics and provide pure PN
samples. PNe represent powerful astrophysical probes. They are important
dynamical tracers, key sources of ISM chemical enrichment, windows into late
stellar evolution, and potent cosmological yardsticks. But their utility
depends on separating them unequivocally from the many nebular mimics which can
strongly resemble bona fide PNe in traditional optical images and spectra. We
merge new PNe from the carefully evaluated, homogeneous MASH-I and MASH-II
surveys, which offer a wider evolutionary range of PNe than hitherto available,
with previously known PNe classified by SIMBAD. Mid-infrared (MIR) measurements
vitally complement optical data because they reveal other physical processes
and morphologies via fine-structure lines, molecular bands and dust. MIR
colour-colour planes, optical emission line ratios and radio fluxes show the
unambiguous classification of PNe to be complex, requiring all available
evidence. Statistical trends provide predictive value and we offer quantitative
MIR criteria to determine whether an emission nebula is most likely to be a PN
or one of the frequent contaminants such as compact HII regions or symbiotic
systems. Prerequisites have been optical images and spectra but MIR morphology,
colours, environment and a candidate's MIR/radio flux ratio provide a more
rigorous classification. Our ultimate goal is to recognize PNe using only MIR
and radio characteristics, enabling us to trawl for PNe effectively even in
heavily obscured regions of the Galaxy.Comment: 32 pages, 18 figures, 10 table