14 research outputs found
ASCA and RXTE Observations of Non-Thermal X-ray Emission from Galactic Supernova Remnants: G156.2+5.7
(Abridged) We are conducting a survey of Galactic shell-type supernova
remnants (SNRs) known or suspected to possess non-thermal components to their
X-ray emission using new and archived observations made with such X-ray
satellites as ROSAT, ASCA, RXTE, Chandra and XMM-Newton. This research is
intended to probe the phenomenon of cosmic-ray acceleration by Galactic SNRs
and estimate the maximum energy of cosmic-ray electrons accelerated by these
sources. To illustrate this work, we examine the X-ray spectrum of the
northwestern rim of an SNR suspected to have a non-thermal component to its
X-ray emission, G156.2+5.7 (RX J04591+5147), over the energy range of
approximately 0.7-12.0 keV using observations made by the ASCA GIS and the RXTE
PCA. We compare fits made to the non-thermal component using two models, a
simple power law and SRCUT. Both models give acceptable fits: the photon index
derived from the fit made with the power law model, 2.0 (+0.2, -0.5), is
comparable to values obtained for the bright rims of other SNRs with hard X-ray
spectra. Using the SRCUT model, we derive a value of 2.42 (+0.24, -0.23) x
10^17 Hz for the cutoff frequency: based on this value and assuming a mean
magnetic field strength of 14 microGauss, we estimate the cutoff energy of
cosmic-ray electrons accelerated by G156.2+5.7 to be approximately 32 TeV. This
energy value is well short of the "knee" feature of the cosmic-ray spectrum.Comment: 6 pages with 2 figures. This tex file uses the style file cospar.sty
from Elvesier Science Publishers. To be published in Advances in Space
Research, Proceedings of 34th COSPAR Assembly (October 2002), Symposium E1.4,
"High Energy Studies of Supernova Remnants and Neutron Stars," eds. W.
Hermsen and W. Becker (2003
Radio-Continuum study of the Nearby Sculptor Group Galaxies. Part 1: NGC 300 at lambda = 20 cm
A series of new radio-continuum (lambda=20 cm) mosaic images focused on the
NGC 300 galactic system were produced using archived observational data from
the VLA and/or ATCA. These new images are both very sensitive (rms=60 microJy)
and feature high angular resolution (<10"). The most prominent new feature is
the galaxy's extended radio-continuum emission, which does not match its
optical appearance. Using these newly created images a number of previously
unidentified discrete sources have been discovered. Furthermore, we demonstrate
that a joint deconvolution approach to imaging this complete data-set is
inferior when compared to an immerge approach.Comment: 13 pages, 12 figures, accepted to APSS, new version to correct the
missing reference
Optical Spectra of SNR Candidates in NGC 300
We present moderate-resolution (<5A) long-slit optical spectra of 51 nebular
objects in the nearby Sculptor Group galaxy NGC 300 obtained with the 2.3 meter
Advanced Technology Telescope at Siding Spring Observatory, Australia. Adopting
the criterion of [SII]/Ha>=0.4 to confirm supernova remnants (SNRs) from
optical spectra, we find that of 28 objects previously proposed as SNRs from
optical observations, 22 meet this criterion with six showing [SII]/Ha of less
than 0.4. Of 27 objects suggested as SNRs from radio data, four are associated
with the 28 previously proposed SNRs. Of these four, three (included in the 22
above) meet the criterion. In all, 22 of the 51 nebular objects meet the
[SII]/Ha criterion as SNRs while the nature of the remaining 29 objects remains
undetermined by these observations.Comment: Accepted for publication in Astrophysics & Space Scienc
A search for candidate radio supernova remnants in the nearby irregular starburst galaxies NGC 4214 and NGC 4395
A search for candidate radio supernova remnants in the nearby irregular starburst galaxies NGC 4214 and NGC 4395
We present the results of a search for new candidate radio supernova remnants (SNRs) in the nearby starburst irregular galaxies NGC 4214 and NGC 4395 using archived radio observations made with the Very Large Array (VLA) at the wavelengths of 3.5 cm, 6 cm and 20 cm for NGC 4214 and 6 cm and 20 cm for NGC 4395. These observations were analyzed as part of our ongoing search for candidate radio SNRs in nearby galaxies: the goal of this search is to prepare a large sample of candidate radio SNRs for the purpose of a robust statistical study of the properties of these sources. Based on our analysis, we have confirmed the nonthermal nature of the discrete radio sources α and β in NGC 4214 and classify these sources as candidate radio SNRs based on their positional coincidences with HII regions in that galaxy. We have measured the flux densities of the two candidate radio SNRs at each wavelength and calculated corresponding spectral indices: we have also measured flux densities of two other discrete radio sources in these galaxies - ρ in NGC 4214 and #3 in NGC 4395 which we suspect to be additional candidate radio SNRs based on their positional coincidences with other HII regions in these galaxies. However, the radio data presently available for these sources cannot confirm such a classification and additional observations are needed. We have also calculated the radio luminosities Lradio at the wavelength of 20 cm for these two candidate radio SNRs as well as the corresponding values for the minimum total energy Emin required to power these radio sources via synchrotron emission and the corresponding magnetic field strength Bmin. We have compared our mean calculated values for these properties with the mean values for populations of candidate radio SNRs in other starburst galaxies: while the values for Lradio and Bmin are roughly comparable to the values seen in other starburst galaxies, the mean value for Emin is higher than the mean value of any other starburst galaxy. Finally, we include these two candidate radio SNRs in a discussion of the Σ − D relation for extragalactic candidate radio SNRs and find that these sources are located on the shallower end of the master Σ − D relation for all extragalactic SNRs as derived by Urošević et al.(2005).
Optical observations of the nearby galaxy IC342 with narrow band [SII] and Hα filters. I
We present observations of a portion of the nearby spiral galaxy IC342 using
narrow band [SII] and Hα 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, Hα
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. [Projekat Ministarstva nauke
Republike Srbije, br. 176005: Emission nebulae: structure and evolution
ASCA and XMM-Newton observations of the galactic supernova remnant G311.5−0.3
We present an analysis of X-ray observations made with ASCA and XMM-Newton of
the Galactic supernova remnant (SNR) G311.5−0.3. Prior infrared and radio
observations of this SNR have revealed a shell-like morphology at both
wavelengths. The spectral index of the radio emission is consistent with
synchrotron emission, while the infrared colors are consistent with emission
from shocked molecular hydrogen. Also previous CO observations have
indicated an interaction between G311.5−0.3 and an adjacent molecular cloud.
Our previous analysis of the pointed ASCA observation made of this SNR
detected X-ray emission from the source for the first time but lacked the
sensitivity and the angular resolution to rigorously investigate its X-ray
properties. We have analyzed an archival XMM-Newton observation that
included G311.5−0.3 in the field of view: this is the first time that
XMM-Newton data has been used to probe the X-ray properties of this SNR. The
XMM-Newton observation confirms that the X-ray emission from G311.5−0.3 is
centrally concentrated and supports the classification of this source as a
mixed-morphology SNR. In addition, our joint fitting of extracted ASCA and
XMM-Newton spectra favor a thermal origin for the X-ray emission over a
non-thermal origin. The spectral fitting parameters for our TBABS×APEC fit
to the extracted spectra are NH = 4.63+1.87 −0.85×1022 cm −2 and kT =
0.68+0.20−0.24 keV. From these fit parameters, we derive the following
values for physical parameters of the SNR: ne = 0.20 cm −3, np = 0.17 cm −3,
MX = 21.4 M· and P/k = 3.18×106 K cm −3
Radio-continuum study of the nearby sculptor group galaxies. Part 3: NGC 7793 at λ=12.2, 6 and 3 cm
A morphological study of the supernova remnant Rx J0852.0-4622 (Vela Jr.)
We conduct a multiwavelength morphological study of the Galactic supernova remnant (SNR) RX J0852.0–4622 (also known as Vela Jr., Vela Z, and G266.2−1.2). RX J0852.0–4622 is coincident with the edge of the larger Vela SNR causing confusion in the attribution of some filamentary structures to either RX J0852.0–4622 or its larger sibling. We find that the RX J0852.0–4622 radio-continuum emission can be characterized by a two-dimensional shell with a radius of 0fdg90 ± 0fdg01 (or 11.8 ± 0.6 pc at an assumed distance of 750 pc) centered at (l, b) = (133fdg08 ± 0fdg01,−46fdg34 ± 0fdg01) (or R.A. = 8h52m19fs2, decl. = −46°20'24farcs0, J2000), consistent with X-ray and gamma-ray emission. Although [O iii] emission features are generally associated with the Vela SNR, one particular [O iii] emission feature, which we denote as "the Vela Claw," morphologically matches a molecular clump that is thought to have been stripped by the stellar progenitor of the RX J0852.0–4622 SNR. We argue that the Vela Claw feature is possibly associated with RX J0852.0–4622. Toward the northwestern edge of RX J0852.0–4622 , we find a flattening of the radio spectral index toward another molecular clump also thought to be associated with RX J0852.0–4622 . It is currently unclear whether this feature and the Vela Claw result from interactions between the RX J0852.0–4622 shock and interstellar medium gas.Nigel I. Maxted, M. D. Filipović, H. Sano, G. E. Allen, T. G. Pannuti ... T. J. Galvin ... et al