The evolution and geometry of the outer parts of the Small Magellanic Cloud

The purpose of this study is to achieve an improved and more complete understanding of the structure and evolutionary history of the Small Magellanic Cloud, the second nearest galaxy to our own.The study was focused on the northeastern and west/southwestern outer parts of the SMC, including populations at projected distances larger than 2.2 kpc from the centre of the SMC. These regions have scarcely been studied in detail in the past.The observational material consisted of good quality B and R photographic plates taken with the U.K. Schmidt Telescope in Australia, digitised by the COSMOS automatic microdensitometer and calibrated by a series of CCD photometric sequences obtained at the European Southern Observatory (with the 1.5m Danish Telescope) and at the Anglo-Australian Observatory (with the 4m Telescope)A study of the carbon star population in the SMC outer regions was also conducted, using UKST prism plates. The carbon stars were used as probes of the intermediate-age populations in the outer parts of the SMC.Colour-magnitude diagrams were constructed over the whole of the area measured. The analysis of the properties of these diagrams resulted in (a) establishing the population synthesis in the outer parts of the SMC as a function of position with respect to the centre, and (b) probing the geometrical structure (in three dimensions) of these outlying regions of the SMC, which led to the discovery of a significant line-of-sight depth in the NE outer parts

Supernova remnants and candidates detected in the XMM-Newton M31 large survey

We present the analysis of supernova remnants (SNRs) and candidates in M31 identified in the XMM-Newton large programme survey of M31. SNRs are among the bright X-ray sources in a galaxy. They are good indicators of recent star formation activities of a galaxy and of the interstellar environment in which they evolve. By combining the X-ray data of sources in M31 with optical data as well as with optical and radio catalogues, we aim to compile a complete, revised list of SNRs emitting X-rays in M31 detected with XMM-Newton, study their luminosity and spatial distribution, and understand the X-ray spectrum of the brightest SNRs. We analysed the X-ray spectra of the twelve brightest SNRs and candidates using XMM-Newton data. The four brightest sources allowed us to perform a more detailed spectral analysis and the comparison of different models to describe their spectrum. For all M31 large programme sources we searched for optical counterparts on the Ha, [Sii], and [Oiii] images of the Local Group Galaxy Survey. We confirm 21 X-ray sources as counterparts of known SNRs. In addition, we identify five new X-ray sources as X-ray and optically emitting SNRs. Seventeen sources are no longer considered as SNR candidates. We have thus created a list of 26 X-ray SNRs and 20 candidates in M31 based on their X-ray, optical, and radio emission, which is the most recent complete list of X-ray SNRs in M31. The brightest SNRs have X-ray luminosities of up to 8 x 10^36 erg/s in the 0.35 - 2.0 keV band.Comment: Accepted by AandA. 15 pages. Appendices will be published electronically onl

Deep XMM-Newton observations of the northern disk of M31 II: Tracing the hot interstellar medium

Aims: We use new deep XMM-Newton observations of the northern disk of M 31 to trace the hot interstellar medium (ISM) in unprecedented detail and to characterise the physical properties of the X-ray emitting plasmas. Methods: We used all XMM-Newton data up to and including our new observations to produce the most detailed image yet of the hot ISM plasma in a grand design spiral galaxy such as our own. We compared the X-ray morphology to multi-wavelength studies in the literature to set it in the context of the multi-phase ISM. We performed spectral analyses on the extended emission using our new observations as they offer sufficient depth and count statistics to constrain the plasma properties. Data from the Panchromatic Hubble Andromeda Treasury were used to estimate the energy injected by massive stars and their supernovae. We compared these results to the hot gas properties. Results: The brightest emission regions were found to be correlated with populations of massive stars, notably in the 10 kpc star-forming ring. The plasma temperatures in the ring regions are ~0.2 keV up to ~0.6 keV. We suggest this emission is hot ISM heated in massive stellar clusters and superbubbles. We derived X-ray luminosities, densities, and pressures for the gas in each region. We also found large extended emission filling low density gaps in the dust morphology of the northern disk, notably between the 5 kpc and 10 kpc star-forming rings. We propose that the hot gas was heated and expelled into the gaps by the populations of massive stars in the rings. Conclusions. It is clear that the massive stellar populations are responsible for heating the ISM to X-ray emitting temperatures, filling their surroundings, and possibly driving the hot gas into the low density regions. Overall, the morphology and spectra of the hot gas in the northern disk of M 31 is similar to other galaxy disks.Comment: 23 pages, 14 figures, accepted for publication in Astronomy & Astrophysic