Winds from Nuclear Starbursts: Old Truths and Recent Progress on Superwinds

I will discuss a few select aspects of the most common and best understood galactic-scale outflow -- starburst-driven superwinds, focusing on winds from nuclear starburst galaxies. I will show that modern observations, in particular in the soft and hard X-ray bands, complement and reinforce the existing paradigm of superwinds as flows collectively driven by multiple SNe. The properties of the diffuse X-ray emission from dwarf starburst galaxies, L_BOL ~ L_* starbursts in spiral galaxies, and ULIRGS, are all consistent with superwind activity. Where appropriate, I contrast the physics of starburst-driven winds with poorly collimated winds from AGN, and discuss what we know of the role of LLAGN and Seyfert nuclei in starburst superwind galaxies.Comment: To appear in the proceedings of IAU symposium 222: The Interplay among Black Holes, Stars and ISM in Galactic Nuclei, held in Gramado, Brazil, March 1-5 2004. Eds. Th. Storchi Bergmann, L.C. Ho & H.R. Schmitt. 6 pages, 1 figur

Predicting X-ray emission from wind-blown bubbles - Limitations of fits to ROSAT spectra

Wind-blown bubbles, from those around massive O and Wolf-Rayet stars, to superbubbles around OB associations and galactic winds in starburst galaxies, have a dominant role in determining the structure of the Interstellar Medium. X-ray observations of these bubbles are particularly important as most of their volume is taken up with hot gas, 1E5 < T (K) < 1E8. However, it is difficult to compare X-ray observations, usually analysed in terms of single or two temperature spectral model fits, with theoretical models, as real bubbles do not have such simple temperature distributions. In this introduction to a series of papers detailing the observable X-ray properties of wind-blown bubbles, we describe our method with which we aim to solve this problem, analysing a simulation of a wind-blown bubble around a massive star. We model a wind of constant mass and energy injection rate, blowing into a uniform ISM, from which we calculate X-ray spectra as would be seen by the ROSAT PSPC. We compare the properties of the bubble as would be inferred from the ROSAT data with the true properties of the bubble in the simulation. We find standard spectral models yield inferred properties that deviate significantly from the true properties, even though the spectral fits are statistically acceptable, and give no indication that they do not represent to true spectral distribution. Our results suggest that in any case where the true source spectrum does not come from a simple single or two temperature distribution the "observed" X-ray properties cannot naively be used to infer the true properties.Comment: 14 pages, LaTeX with 13 eps figures, condensed abstract. MNRAS in pres

The Energetics and Mass-loss of Mrk33

We present ROSAT HRI X-ray data and optical imaging of the important dwarf starburst Markarian 33. We find an extended, complex, shell-like morphology in the X-ray emission, with an extent of 2.3 x 1.9kpc, coincident with the bright star-forming regions at the centre of the galaxy. The physical extent of this X-ray emission from Mrk 33 is very similar to the observed Halpha emission, and suggests that the bulk of the X-ray emission is coming from an expanding superbubble. We estimate the age and mass of Mrk 33's starburst to be 5.8 Myr and 6.9 x 10^{6} Msolar respectively with the energy injection rate in the central regions of the galaxy being 10^{41} erg/s, while the associated mass-loss rate from the star-forming regions is estimated to be 0.2 Msolar/yr. We suggest that the X-ray emission is predominantly powered by starburst type activity and argue that a blowout in the form of a galactic wind is the most likely fate for Mrk 33 resulting in the loss of most of the galaxy's metal-enriched material and a small fraction (<1 per cent) of the ISM.Comment: 13 pages, 6 figures, accepted for publication in MNRA

Chandra and XMM-Newton Observations of NGC 4214: The Hot Interstellar Medium and the Luminosity Function of Dwarf Starbursts

We present results from Chandra and XMM-Newton X-ray observations of NGC 4214, a nearby dwarf starburst galaxy containing several young regions of very active star-formation. Starburst regions are known to be associated with diffuse X-ray emission, and in this case the X-ray emission from the galaxy shows an interesting morphological structure within the galaxy, clearly associated with the central regions of active star-formation. Of the two main regions of star-formation in this galaxy, X-ray emission associated with the older is identified whereas little is detected from the younger, providing an insight into the evolutionary process of the formation of superbubbles around young stellar clusters. The spectra of the diffuse emission from the galaxy can be fitted with a two temperature component thermal model with kT=0.14keV and 0.52keV, and analysis of this emission suggests that NGC 4214 will suffer a blow-out in the future. The point source population of the galaxy has an X-ray luminosity function with a slope of -0.76. This result, together with those for other dwarf starburst galaxies (NGC 4449 and NGC 5253), was added to a sample of luminosity functions for spiral and starburst galaxies. The slope of the luminosity function of dwarf starbursts is seen to be similar to that of their larger counterparts and clearly flatter than those seen in spirals. Further comparisons between the luminosity functions of starbursts and spiral galaxies are also made.Comment: 16 pages, 12 figures. Accepted for publication in MNRA

Exploring heritage through time and space : Supporting community reflection on the highland clearances

On the two hundredth anniversary of the Kildonan clearances, when people were forcibly removed from their homes, the Timespan Heritage centre has created a program of community centred work aimed at challenging pre conceptions and encouraging reflection on this important historical process. This paper explores the innovative ways in which virtual world technology has facilitated community engagement, enhanced visualisation and encouraged reflection as part of this program. An installation where users navigate through a reconstruction of pre clearance Caen township is controlled through natural gestures and presented on a 300 inch six megapixel screen. This environment allows users to experience the past in new ways. The platform has value as an effective way for an educator, artist or hobbyist to create large scale virtual environments using off the shelf hardware and open source software. The result is an exhibit that also serves as a platform for experimentation into innovative ways of community co-creation and co-curation.Postprin

Chandra & XMM-Newton Observations of NGC5253. Analysis of the X-ray Emission from a Dwarf Starburst Galaxy

We present Chandra and XMM-Newton X-ray data of NGC5253, a local starbursting dwarf elliptical galaxy, in the early stages of a starburst episode. Contributions to the X-ray emission come from discrete point sources and extended diffuse emission, in the form of what appear to be multiple superbubbles, and smaller bubbles probably associated with individual star clusters. Chandra detects 17 sources within the optical extent of NGC5253 down to a completeness level corresponding to a luminosity of 1.5E37 erg/s.The slope of the point source X-ray luminosity function is -0.54, similar to that of other nearby dwarf starburst galaxies. Several different types of source are detected within the galaxy, including X-ray binaries and the emission associated with star-clusters. Comparison of the diffuse X-ray emission with the observed Halpha emission shows similarities in their extent. The best spectral fit to the diffuse emission is obtained with an absorbed, two temperature model giving temperatures for the two gas components of ~0.24keV and ~0.75keV.The derived parameters of the diffuse X-ray emitting gas are as follows: a total mass of \~1.4E6 f^{1/2} Msun, where f is the volume filling factor of the X-ray emitting gas, and a total thermal energy content for the hot X-ray emitting gas of \~3.4E54 f^{1/2} erg. The pressure in the diffuse gas is P/k ~ 1E6f^{-1/2}K/cm3. We find that these values are broadly commensurate with the mass and energy injection from the starburst population. Analysis of the kinematics of the starburst region suggest that the stellar ejecta contained within it can escape the gravitational potential well of the galaxy, and pollute the surrounding IGM.Comment: 19 pages, In Press in MNRA