413 research outputs found
Physical Structure and Nature of Supernova Remnants in M101
Supernova remnant (SNR) candidates in the giant spiral galaxy M101 have been
previously identified from ground-based H-alpha and [SII] images. We have used
archival Hubble Space Telescope (HST) H-alpha and broad-band images as well as
stellar photometry of 55 SNR candidates to examine their physical structure,
interstellar environment, and underlying stellar population. We have also
obtained high-dispersion echelle spectra to search for shocked high-velocity
gas in 18 SNR candidates, and identified X-ray counterparts to SNR candidates
using data from archival observations made by the Chandra X-ray Observatory.
Twenty-one of these 55 SNR candidates studied have X-ray counterparts, although
one of them is a known ultra-luminous X-ray source. The multi-wavelength
information has been used to assess the nature of each SNR candidate. We find
that within this limited sample, ~16% are likely remnants of Type Ia SNe and
~45% are remnants of core-collapse SNe. In addition, about ~36% are large
candidates which we suggest are either superbubbles or OB/HII complexes.
Existing radio observations are not sensitive enough to detect the non-thermal
emission from these SNR candidates. Several radio sources are coincident with
X-ray sources, but they are associated with either giant HII regions in M101 or
background galaxies. The archival HST H-alpha images do not cover the entire
galaxy and thus prevents a complete study of M101. Furthermore, the lack of HST
[SII] images precludes searches for small SNR candidates which could not be
identified by ground-based observations. Such high-resolution images are needed
in order to obtain a complete census of SNRs in M101 for a comprehensive
investigation of the distribution, population, and rates of SNe in this galaxy.Comment: 37 pages, 4 Tables, 7 Figures, accepted for publication in the
Astronomical Journa
The Physical Parameters of the Micro-quasar S26 in the Sculptor Group Galaxy NGC 7793
NGC 7793 - S26 is an extended source (350 pc 185 pc) previously
studied in the radio, optical and x-ray domains. It has been identified as a
micro-quasar which has inflated a super bubble. We used Integral Field Spectra
from the Wide Field Spectrograph on the ANU 2.3 m telescope to analyse spectra
between 3600--7000 \AA. This allowed us to derive fluxes and line ratios for
selected nebular lines. Applying radiative shock model diagnostics, we estimate
shock velocities, densities, radiative ages and pressures across the object. We
show that S26 is just entering its radiative phase, and that the northern and
western regions are dominated by partially-radiative shocks due to a lower
density ISM in these directions. We determine a velocity of expansion along the
jet of 330 km s, and a velocity of expansion of the bubble in the minor
axis direction of 132 km s. We determine the age of the structure to be
yr, and the jet energy flux to be erg
s The jet appears to be collimated within deg, and to undergo
very little precession. If the relativistic , then some 4
M of relativistic matter has already been processed through the jet.
We conclude that the central object in S26 is probably a Black Hole with a mass
typical of the ultra-luminous X-ray source population which is currently
consuming a fairly massive companion through Roche Lobe accretion.Comment: Accepted for publication in MNRAS; 12 pages, 7 figures and 3 table
A multi-wavelength study of Supernova Remnants in six nearby galaxies. I: Detection of new X-ray selected Supernova Remnants with Chandra
We present results from a study of the Supernova Remnant (SNR) population in
a sample of six nearby galaxies (NGC 2403, NGC 3077, NGC 4214, NGC 4449, NGC
4395 and NGC 5204) based on Chandra archival data. We have detected 244
discrete X-ray sources down to a limiting flux of 10^{-15} erg/s. We identify
37 X-ray selected thermal SNRs based on their X-ray colors or spectra, 30 of
which are new discoveries. In many cases the X-ray classification is confirmed
based on counterparts with SNRs identified in other wavelengths. Three of the
galaxies in our sample (NGC 4214, NGC 4395 and NGC 5204) are studied for the
first time, resulting in the discovery of 13 thermal SNRs. We discuss the
properties (luminosity, temperature, density) of the X-ray detected SNRs in the
galaxies of our sample in order to address their dependence on their
environment. We find that X-ray selected SNRs in irregular galaxies appear to
be more luminous than those in spirals. We attribute this to the lower
metalicities and therefore more massive progenitor stars of irregular galaxies
or the higher local densities of the ISM. We also discuss the X-ray selected
SNR populations in the context of the Star Formation Rate of their host
galaxies. A comparison of the numbers of observed luminous X-ray selected SNRs
with those expected based on the luminosity functions of X-ray SNRs in the MCs
and M33 suggest different luminosity distributions between the SNRs in spiral
and irregular galaxies with the latter tending to have flatter distributions.Comment: 56 pages, 14 figures, 26 tables. Accepted for publication in Ap
Revealing the nature of central emission nebulae in the dwarf galaxy NGC 185
In this paper we present new optical observations of the galaxy NGC 185
intended to reveal the status of supernova remnants (SNRs) in this dwarf
companion of the Andromeda galaxy. Previously, it was reported that this galaxy
hosts one SNR. Our deep photometric study with the 2m telescope at Rozhen
National Astronomical Observatory using narrow-band H and [SII] filters
revealed complex structure of the interstellar medium in the center of the
galaxy. To confirm the classification and to study the kinematics of the
detected nebulae, we carried out spectroscopic observations using the SCORPIO
multi-mode spectrograph at the 6m telescope at the Special Astrophysical
Observatory of the Russian Academy of Science, both in low- and high-resolution
modes. We also searched the archival X-ray and radio data for counterparts of
the candidate SNRs identified by our optical observations. Our observations
imply the presence of one more SNR, one possible HII region previously
cataloged as part of an SNR, and the presence of an additional source of shock
ionization in one low-brightness PN. We detected enhanced [SII]/H_alpha and
[NII]/H_alpha line ratios, as well as relatively high (up to 90 km s)
expansion velocities of the two observed nebulae, motivating their
classification as SNRs (with diameters of 45 pc and 50 pc), confirmed by both
photometric and spectral observations. The estimated electron density of
emission nebulae is 30 - 200 cm. Archival XMM-Newton observations
indicate the presence of an extended, low-brightness, soft source in projection
of one of the optical SNRs, whereas the archival VLA radio image shows weak,
unresolved emission in the center of NGC 185.Comment: 15 pages, 14 figures, accepted for publication in A&
A two-zone model for the emission from RX J1713.7-3946
We study the acceleration and radiation of charged particles in the shock
waves of supernova remnants using a recent version of the "box model".
According to this, particles are accelerated in an energy-dependent region
around the shock by the first order Fermi mechanism and lose energy through
radiation. The particle distribution function is obtained from a spatially
averaged kinetic equation that treats the energy losses self-consistently.
There exists also a second population that consists of those particles that
escape behind the shock where they also radiate. The energy distribution of
this population is calculated in a similar manner. The application of the model
to the supernova remnant RX J1713.7-3946, which was recently confirmed as a TeV
source by H.E.S.S., shows that the X-ray emission can be attributed to electron
synchrotron radiation while in gamma-rays there are contributions from both
electrons and protons, with protons playing the dominant role. Additionally,
there are strong indications that particles diffuse in turbulence that has a
Kolmogorov spectrum.Comment: 6 pages, 2 figures, accepted by Astronomy and Astrophysic
VMXR: a EUD Environment for Virtual Merchandizing in XR
This paper presents the current development state of VMXR, a Proof of Concept (PoC) environment allowing people without programming experience to create and configure product showcases in a Virtual and eXtended reality setting. The aim of the PoC is to identify proper metaphors and workflows for supporting showcase designers in creating interactions with the virtual product representation or enhancing the physical environment through additional information and media
X-ray emission from the Sculptor galaxy NGC 300
We report here the results of a full analysis of all the ROSAT PSPC spectral
imaging observations and all the ROSAT HRI high resolution imaging observations
of the very nearby (D=2.1 Mpc) Sculptor galaxy, NGC 300. Many point sources are
detected within the field, several of them showing evidence for variability,
and we present full source lists detailing their X-ray properties, and attempt
to classify them on the basis of their temporal, spectral and multi-wavelength
characteristics. A black hole X-ray binary candidate, a supersoft source and
several supernova remnants and HII regions are detected in X-rays, as is
unresolved, possibly diffuse emission, accounting for perhaps 20% of the total
NGC 300 X-ray (0.1-2.4 keV) luminosity (5.8 10e38 erg/s). We compare the X-ray
source luminosity distribution of NGC 300 with that of other nearby galaxies,
and we also compare NGC 300 with its Sculptor neighbours, concluding that it is
a quite an unremarkable system, showing no unusual X-ray (or other
multi-wavelength) properties. It may be one of the best examples of a
completely typical normal quiescent late-type spiral galaxy.Comment: 12 pages, latex file, 7 compressed postscript figures, to appear in
A&
Optical observations of the nearby galaxy IC342 with narrow band [SII] and H filters. I
We present observations of the portion of the nearby spiral galaxy IC342
using narrow band [SII] and H filters. These observations were carried
out in November 2011 with the 2m RCC telescope at Rozhen National Astronomical
Observatory in Bulgaria. In this paper we report coordinates, diameters,
H and [SII] fluxes for 203 HII regions detected in two fields of view
in IC342 galaxy. The number of detected HII regions is 5 times higher than
previously known in these two parts of the galaxy.Comment: 9 pages, 3 tables, 4 figures. Table 3 corrected + small corrections
in the tex
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