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

O debate sobre os métodos de ensino nos liceus portugueses (anos 30 a 60 do século XX)

Congresso realizado nos dias 6 a 9 de Maio de 2014, em Toluca, MéxicoA presente comunicação tem como objetivo refletir sobre os métodos de ensino, ao nível do ensino secundário, tal como são propostos e debatidos por educadores e professores em duas das grandes revistas pedagógicas consagrados a esse nível de ensino e ligadas a um importante contexto de formação de professores – o Liceu Normal de Pedro Nunes situado em Lisboa. Estamos a falar do Boletim do Liceu Normal de Lisboa Pedro Nunes (1932-1938) e de Palestra. Revista de pedagogia e cultura (1957-1973).info:eu-repo/semantics/publishedVersio

A multifrequency study of supernova remnants in the Large Magellanic Cloud

Supernova remnants (SNRs) are the structures left behind after the explosive death of a star - the supernova (SN). They are responsible for the chemical enrichment of galaxies and inject massive amounts of energy into their surroundings. As they play a significant role in the dynamical and chemical evolution of galaxies, understanding them is of great importance. In this study, I look toward the SNR population of the Large Magellanic Cloud (LMC) - an irregular dwarf galaxy located at a distance of ~ 50 kpc. The LMC is an ideal laboratory for astronomers due to the numerous favourable attributes that aid in observations, e.g., its relatively close proximity, low foreground absorption, and nearly face on orientation. Although emission across the electromagnetic spectrum is included in this study, the primary focus is on emission in the radio-continuum. Hence, the majority of the data used in this thesis consists of pointed and mosaic observations taken with the Australia Telescope Compact Array - a radio interferometer consisting of six 22-m telescopes. Depending on the set-up of this array, the observations may result in high-resolution images - used to study the intricate structure of the remnants, or low resolution images, for obtaining total flux measurements. The first component of this work looks into the individual SNRs and the candidates, adding to the population with the discovery and classification of new SNRs and (re)measuring known remnants. The result of this is the most comprehensive catalogue of SNRs in the LMC. In this catalogue, multi-frequency morphologies of the remnant were examined and various properties were measured, such as the size, integrated flux density measurements at several radio-continuum frequencies - leading to the resulting radio spectral indices, polarisation (and Faraday rotation where possible), star formation history and star formation rates of the surrounding environment, surface-brightness, and luminosity. The second portion of this work makes use of the properties measured and recorded in the catalogue in conjunction with properties (e.g., age) from the literature to carry out basic statistical analysis to inspect the entire population of SNRs in the LMC. This allows astronomers to track the evolution of SNRs, and investigate how certain properties (spectral index, surface brightness etc.) changed as they aged. Further, it showed the relationship between the stellar environment that the SNR resides and the type of SN that it underwent, allowing for this information to be use to better understand other galaxies and star forming regions. With a more complete luminosity function, it was seen that the influence of SNRs to the cosmic ray acceleration in a galaxy is very significant

Radio-continuum study of MCSNR J0536-7038 (DEM L249)

We present a detailed radio-continuum study on Australia Telescope Compact Array (ATCA) observations of Large Magellanic Cloud (LMC) supernova remnant (SNR), MCSNR J0536-7038. This Type Ia SNR follows a horseshoe morphology, with a size 32 pc × 32 pc (1-pc uncertainty in each direction). It exhibits a radio spectrum α=-0.52±0.07 between λ=73 and 6 cm. We report detections of regions showing moderately high fractional polarisation at 6 cm, with a peak value of 71±25 % and a mean fractional polarisation of 35±8 %. We also estimate an average rotation measure across the remnant of -237 rad m-2. The intrinsic magnetic field appears to be uniformly distributed, extending in the direction of the two brightened limbs of the remnant

Optical discovery and multiwavelength investigation of supernova remnant MCSNR J0512-6707 in the Large Magellanic Cloud

We present optical, radio and X-ray data that confirm a new supernova remnant (SNR) in the Large Magellanic Cloud (LMC) discovered using our deep Hα imagery. Optically, the new SNR has a somewhat filamentary morphology and a diameter of 56 × 64 arcsec (13.5 × 15.5 pc at the 49.9 kpc distance of the LMC). Spectroscopic follow-up of multiple regions show high [S ii]/Hα emission-line ratios ranging from 0.66 ± 0.02 to 0.93 ± 0.01, all of which are typical of an SNR. We found radio counterparts for this object using our new Australia Telescope Compact Array (ATCA) 6 cm pointed observations as well as a number of available radio surveys at 8640 MHz, 4850 MHz, 1377 MHz and 843 MHz. With these combined data we provide a spectral index α ≈ −0.5 between 843 and 8640 MHz. Both spectral line analysis and the magnetic field strength, ranging from 124 to 184 μG, suggest a dynamical age between ∼2200 and ∼4700 yr. The SNR has a previously catalogued X-ray counterpart listed as HP 483 in the ROSAT Position Sensitive Proportional Counter (PSPC) catalogue.9 page(s

A multi-wavelength look at the young plerionic supernova remnant 0540-69.3

We present a study of the plerionic supernova remnant 0540-69.3 in the LMC in X-ray, radio, optical, and infrared. We find that the shell of 0540-69.3 is characterized in the X-ray by thermal nonequilibrium plasma with depleted Mg and Si abundances and a temperature of kT ∼ 0.7 keV. This thermal emission is superimposed with synchrotron emission in several regions. Based on X-ray spectra and on morphological considerations in all surveyed wavebands, we conclude that the shell is expanding into a clumpy and highly inhomogeneous medium. In one region of the shell we find an overabundance of Ne, suggesting the presence of ejecta near the edge of the remnant. We also see evidence for reheating of material via a reverse shock originating from the interaction of the supernova blast wave with a particularly dense cloud in the surrounding medium. Finally, we perform the first detailed study of the "halo" region extending 1.2-2.2 pc from the central pulsar. We detect the presence of thermal and nonthermal spectral components but do not find evidence for mixing or ejecta. We conclude that the thermal component is not a counterpart to similar optical and infrared halos and that it is most likely due to the projection of shell material along the line of sight