105 research outputs found
Dust Formation Observed in Young Supernova Remnants with Spitzer
We present dust features and masses observed in young supernova remnants
(SNRs) with Spitzer IRS mapping and staring observations of four youngest
supernova remnants: SNR 1E102.2-7219 (E0102) in the SMC, Cas A and G11.2-0.3 in
our Galaxy, and N132D in the LMC. The spectral mapping data revealed a number
of dust features which include 21 micron-peak dust and featureless dust in Cas
A and 18-micron peak dust in E0102 and N132D. The 18 micron-peak feature is
fitted by a mix of MgSiO and solid Si dust grains, while the 21-micron peak
dust is by a mix of silicates and FeO; we also explore dust fitting using
Continuous Distribution of Ellipsoid grain models. We report detection of CO
fundamental band from Cas A in near-infrared. We review dust features observed
and identified in other SNRs. The dust emission is spatially correlated with
the ejecta emission, showing dust is formed in SN ejecta. The spectra of E0102
show rich gas lines from ejecta including strong ejecta lines of Ne and O,
including two [Ne III] lines and two [Ne V] lines which allow us to diagnostic
density and temperature of the ejecta and measure the ejecta masses. E0102 and
N132D show weak or lacking Ar, Si, and Fe ejecta, whereas the young Galactic
SNR Cas A show strong Ar, Si, and S and weak Fe. We discuss compositions and
masses of dust and association with those of ejecta and finally, dust
contribution from SNe to early Universe.Comment: conference proceeding for "Cosmic Dust - Near and Far" (Heidelberg,
Germany), 11pages and 7 figure
Spitzer Observations of the Young Core-Collapse Supernova Remnant 1E0102-72.3: Infrared Ejecta Emission and Dust Formation
We present Spitzer Infrared Spectrograph and Infrared Array Camera observations of the young supernova remnant E0102 (SNR 1E0102-7219) in the Small Magellanic Cloud. The infrared spectra show strong lines of Ne and O, with the [Ne II] line at 12.8 μm having a large velocity dispersion of 2000-4500 km s^(–1) indicative of fast-moving ejecta. Unlike the young Galactic SNR Cas A, E0102 lacks emission from Ar and Fe. Diagnostics of the observed [Ne III] line pairs imply that [Ne III] emitting ejecta have a low temperature of 650 K, while [Ne V] line pairs imply that the infrared [Ne V] emitting ejecta have a high density of ~10^4 cm^(–3). We have calculated radiative shock models for various velocity ranges including the effects of photoionization. The shock model indicates that the [Ne V] lines come mainly from the cooling zone, which is hot and dense, whereas [Ne II] and [Ne III] come mainly from the photoionization zone, which has a low temperature of 400-1000 K. We estimate an infrared-emitting Ne ejecta mass of 0.04 M_⊙ from the infrared observations, and discuss implications for the progenitor mass. The spectra also have a dust continuum feature peaking at 18 μm that coincides spatially with the ejecta, providing evidence that dust formed in the expanding ejecta. The 18 μm peak dust feature is fitted by a mixture of MgSiO_3 and Si dust grains, while the rest of the continuum requires either carbon or Al2O3 grains. We measure the total dust mass formed within the ejecta of E0102 to be ~0.014 M_⊙. The dust mass in E0102 is thus a factor of a few smaller than that in Cas A. The composition of the dust is also different, showing relatively less silicate and likely no Fe-bearing dust, as is suggested by the absence of Fe-emitting ejecta
A multiwavelength study of the supernova remnant G296.8-0.3
We report XMM-Newton observations of the Galactic supernova remnant
G296.8-0.3, together with complementary radio and infrared data. The spatial
and spectral properties of the X-ray emission, detected towards G296.8-0.3, was
investigated in order to explore the possible evolutionary scenarios and the
physical connexion with its unusual morphology detected at radio frequencies.
G296.8-0.3 displays diffuse X-ray emission correlated with the peculiar radio
morphology detected in the interior of the remnant and with the shell-like
radio structure observed to the northwest side of the object. The X-ray
emission peaks in the soft/medium energy range (0.5-3.0 keV). The X-ray
spectral analysis confirms that the column density is high (NH \sim 0.64 x
10^{22} cm^{-2}) which supports a distant location (d>9 kpc) for the SNR. Its
X-ray spectrum can be well represented by a thermal (PSHOCK) model, with kT
\sim 0.86 keV, an ionization timescale of 6.1 x 10^{10} cm^{-3} s, and low
abundance (0.12 Z_sun). The 24 microns observations show shell-like emission
correlated with part of the northwest and southeast boundaries of the SNR. In
addition a point-like X-ray source is also detected close to the geometrical
center of the radio SNR. The object presents some characteristics of the
so-called compact central objects (CCO). Its X-ray spectrum is consistent with
those found at other CCOs and the value of NH is consistent with that of
G296.8-0.3, which suggests a physical connexion with the SNR.Comment: Accepted for publication in Astrophysics & Space Scienc
The 3D Structure of N132D in the LMC: A Late-Stage Young Supernova Remnant
We have used the Wide Field Spectrograph (WiFeS) on the 2.3m telescope at
Siding Spring Observatory to map the [O III] 5007{\AA} dynamics of the young
oxygen-rich supernova remnant N132D in the Large Magellanic Cloud. From the
resultant data cube, we have been able to reconstruct the full 3D structure of
the system of [O III] filaments. The majority of the ejecta form a ring of
~12pc in diameter inclined at an angle of 25 degrees to the line of sight. We
conclude that SNR N132D is approaching the end of the reverse shock phase
before entering the fully thermalized Sedov phase of evolution. We speculate
that the ring of oxygen-rich material comes from ejecta in the equatorial plane
of a bipolar explosion, and that the overall shape of the SNR is strongly
influenced by the pre-supernova mass loss from the progenitor star. We find
tantalizing evidence of a polar jet associated with a very fast oxygen-rich
knot, and clear evidence that the central star has interacted with one or more
dense clouds in the surrounding ISM.Comment: Accepted for Publication in Astrophysics & Space Science, 18pp, 8
figure
Molecular excitation in the Interstellar Medium: recent advances in collisional, radiative and chemical processes
We review the different excitation processes in the interstellar mediumComment: Accepted in Chem. Re
Kimberlites reveal 2.5-billion-year evolution of a deep, isolated mantle reservoir
The widely accepted paradigm of Earth's geochemical evolution states that the successive extraction of melts from the mantle over the past 4.5 billion years formed the continental crust, and produced at least one complementary melt-depleted reservoir that is now recognized as the upper-mantle source of mid-ocean-ridge basalts1. However, geochemical modelling and the occurrence of high 3He/4He (that is, primordial) signatures in some volcanic rocks suggest that volumes of relatively undifferentiated mantle may reside in deeper, isolated regions2. Some basalts from large igneous provinces may provide temporally restricted glimpses of the most primitive parts of the mantle3,4, but key questions regarding the longevity of such sources on planetary timescales—and whether any survive today—remain unresolved. Kimberlites, small-volume volcanic rocks that are the source of most diamonds, offer rare insights into aspects of the composition of the Earth’s deep mantle. The radiogenic isotope ratios of kimberlites of different ages enable us to map the evolution of this domain through time. Here we show that globally distributed kimberlites originate from a single homogeneous reservoir with an isotopic composition that is indicative of a uniform and pristine mantle source, which evolved in isolation over at least 2.5 billion years of Earth history—to our knowledge, the only such reservoir that has been identified to date. Around 200 million years ago, extensive volumes of the same source were perturbed, probably as a result of contamination by exogenic material. The distribution of affected kimberlites suggests that this event may be related to subduction along the margin of the Pangaea supercontinent. These results reveal a long-lived and globally extensive mantle reservoir that underwent subsequent disruption, possibly heralding a marked change to large-scale mantle-mixing regimes. These processes may explain why uncontaminated primordial mantle is so difficult to identify in recent mantle-derived melts
Presynaptically Localized Cyclic GMP-Dependent Protein Kinase 1 Is a Key Determinant of Spinal Synaptic Potentiation and Pain Hypersensitivity
Electrophysiological and behavioral experiments in mice reveal that a cGMP-dependent kinase amplifies neurotransmitter release from peripheral pain sensors, potentiates spinal synapses, and leads to exaggerated pain
Implementation of strategies to increase adolescents’ access to fruit and vegetables at school: process evaluation findings from the Boost study
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