Posters will be presented on boards throughout the meeting. Before lunch, there will a single talk slot given over to a slide presentation of the posters. This will comprise one slide per poster, with each slide having been prepared in advance by the poster author.
Posters
Oliver Butters (The Open University)
Magnetic properties of cataclysmic variables
Cataclysmic variables are a class of binary stars in which material is ripped off the surface of a Sun-like star and gravitationally pulled towards its white dwarf companion, in a process known as accretion. This study looks at the effect of magnetic fields on this accretion process in the cataclysmic variable subclass known as intermediate polars (IPs).
We have used a magnetic accretion model to investigate the accretion flows of IPs throughout parameter space. The results of our numerical simulations demonstrate that broadly four types of accretion flow configuration are possible: discs, streams, rings and propellers. We show that the equilibrium spin periods in IPs, for a given orbital period and magnetic moment, occur where the flow changes from a type characterised by spin-up (i.e. disc or stream) to one characterised by spin-down (i.e. propeller or ring).
By modelling the emission regions in these systems and calculating the absorption profiles we are now generating synthetic light curves of the different flow types. This will soon become a classification tool which we can use to infer magnetic field strengths in IPs, hence giving a greater understanding in the origin, evolution and ultimate fate of IPs.Chris Cottis (University of Leicester)
The ghost of Lyman-alpha as evidence for radiative acceleration in BAL quasars
The feature that is poetically known as the ghost of Lyman-alpha is a hump seen 5900km/s blueward of the line centre in the broad absorption troughs of some BALQSOs. It is normally seen in Carbon IV but can be present in the absorption troughs of other species. The feature is believed to be caused by the increased radiation pressure on Nitrogen V ions with this velocity due to lyman-alpha. This increased acceleration leads to a deficit of absorbing species evident by increased flux in the absorption trough. Our work has produced a significantly larger sample than has been previously reported allowing us to investigate the criteria set out by Arav (1996) that should be met in order for this interaction to dominate over acceleration due to other species.
Arav (1996) ApJ 465 617Philip Davis (The Open University)
A Test For Disrupted Magnetic Braking in Cataclysmic Variable Evolution
The standard and most widely cited explanation for the dearth of observed cataclysmic variables (CVs) with orbital periods between 2 and 3 hours hours (coined the "Period Gap") is the disrupted magnetic braking model. Despite its success in reproducing the correct position and width of the Period Gap, there is little independent observational support for disrupted magnetic braking. Employing population synthesis techniques we calculate the present day population of two types of detached white dwarf-main sequence star binaries; systems that have emerged from a post common envelope phase (PCEBs) and systems which transferred mass at some point in their past but are now detached as a result of disrupted magnetic braking (DCVs). We find that there is a clear excess of DCVs over PCEBs within the Period Gap. For the most likely scenario we find the ratio DCV:PCEB is between 4.5 and 13.5. We suggest that such an excess provides a robust test for disrupted magnetic braking, and if determined observationally, would strongly corroborate it.Francesca Faedi (University of Leicester)
Transit detection limits for sub-stellar and terrestrial companions to White Dwarfs
We explored the possibility of detecting brown dwarfs, gas giants and terrestrial companions in orbit around white dwarfs by means of their transit signature. The relatively small size of a white dwarf host star (approximately 1R Earth ), would imply that a transit of any companion body larger than the Earth might lead to a total eclipse. We show that companions as small as the Moon orbiting a V ~12 magnitude white dwarf are readily detectable in relatively low signal-to-noise data from surveys such as WASP. This work also shows that future surveys such as Pan-Starrs and LSST, able of observing tens of thousands of white dwarfs, will be capable to detect a significant number of eclipsing sub-stellar companions, and will increase the chances of detecting transiting rocky bodies. These observations will place constraints on models of common envelope and close binary evolution and help to understand the evolution of hot Jupiter systems as well as the solar system in the post-main sequence phase.Martin Feix (University of St Andrew's)
Asymmetric Gravitational Lenses in TeVeS and Application to the Bullet Cluster
We explore the lensing properties of asymmetric matter density distributions in Bekenstein's Tensor-Vector-Scalar theory (TeVeS). Using an iterative Fourier-based solver for the resulting non-linear scalar field equation, we numerically calculate the total gravitational potential and derive the corresponding TeVeS lensing maps. Considering variations on rather small scales, we show that the lensing properties significantly depend on the lens's extent along the line of sight. Furthermore, all simulated TeVeS convergence maps strongly track the dominant baryonic components, non-linear effects, being capable of counteracting this trend, turn out to be very small. Setting up a toy model for the cluster merger 1E0657-558, we infer that TeVeS cannot explain observations without assuming an additional dark mass component in both cluster centers, which is in accordance with previous work. Future applications and other tests of TeVeS or similar non-Einsteinian gravities are discussed.Timothy Garn (University of Cambridge)
The redshift evolution of the infrared / radio correlation
The correlation between the infrared and radio luminosities of star-forming galaxies is the tightest known relationship between the global properties of galaxies, spanning over 6 orders of magnitude in luminosity. By constructing a sample of 238 galaxies within the Spitzer extragalactic First Look Survey field with radio detections at 1.4 GHz and 610 MHz, up to seven infrared detections between 3.6 and 160 microns, five-band optical photometry from SDSS and a spectroscopic redshift, we have probed the evolution in this correlation out to z ~ 1.
The large amount of spectral information available allows extremely accurate conversions between observed flux densities and rest-frame luminosities, essential for studying the correlation at high redshifts. We derive two independent estimates of star formation rate for each source, and use these to identify a possible evolution of the magnetic fields within star-forming galaxies between redshift 1 and the present day.Sarah Graves (University of Cambridge)
Star Formation in Orion: Mapping CO Outflows with HARP/ACSIS
HARP is a new 16 detector SIS spectral imaging array at the JCMT. Together with ACSIS (Auto-Correlation Spectrometer and Imaging System), it allows for far faster mapping in the sub-mm B-band (325 to 375 GHz). As part of a joint project between the HARP and ACSIS teams, a large scale CO 3-2 mapping of approximately 2 square degrees of the Orion A molecular cloud was conducted. The aim was to carry out a census of warm molecular outflows over a large region, allowing comparison with the results of other surveys of outflow tracers, such as shocked molecular hydrogen.
Some of the first images arising from this survey will be presented, and some of the methods for identifying molecular outflows will be discussed. Comparison will also be made between these CO 3-2 images and those arising from observations of both other outflow tracers (e.g. shocked molecular hydrogen) and protostars themselves (e.g. IR and dust continuum images).Sohan Jheeta (The Open University)
What is life?
Huge sums of money are being spent on space missions that are usually linked to the quest for 'the origin of life.' Many of these are aimed at detecting amino acids or other biological chemicals. In light of this, it is important that we should know what is meant by 'life' and what it constitutes.
Although there are already numerous definitions of life, they all fall somewhat short of the mark. In addition, there are even those who would argue that, by and large, definitions are useless since they merely state that which is already known. However, we believe that it is rather imperative that we attempt to define what life is in order to facilitate the search for extraterrestrial entities - after all we do classify everything else in science - eg mass, length and time.
Two typical front runners in describing life are: Gerald Joyce's definition and the MERRING definition. The former states that life is: "a self-sustaining system capable of Darwinian evolution." This is widely accepted by NASA. It should, nevertheless, be realised that life is not self-sustaining, in that it needs constant inputs from external sources. Equally important to question is: what exactly do we mean by Darwinian evolution? (Since Darwin never actually used the word 'evolution', Darwinian or otherwise.) Moreover, the RNA world, for instance, could well be considered to be Lamarckian instead of Darwinian.
The MERRING definition of life is simply a list of properties exhibited by various life forms on Earth. These properties are encompassed in the acronym MERRING: Movement, Excretion, Reproduction, Respiration, Irritability, Nutrition, Growth.
So, bacterial spores do not move any more than grains of sand in suspension. Post menopausal women cannot reproduce and fire grows, as do crystals. In short, the MERRING definition may only be good for a discussion point and/or a teaching aid.
Since we believe that neither of these, nor any of the current definitions accurately encompass what life actually is, we propose an alternative, which we will refer to here as 'NEW': "Life is a thermodynamically open chemical system with a boundary. It contains an information based complex system with emergent properties, part of which drives a metabolism based on a proton gradient. This information is heritable and coded in such a way as to allow variation and thus evolution."
Table 1 compares the 3 definitions — it can be seen that our new one is in favour of mule being alive and the rest dead.Joyce MERRING NEW definition Virus Alive Dead Dead Crystal Dead Dead Dead Flame Dead Dead Dead Mule Dead Dead Alive How can this new definition help in the exploration of extraterrestrial life? In fact, by itself, it does nothing, but it will require a new and radical approach in that we should focus on developing the methodology to detect proton gradients. At present, that would appear to be an insurmountable task, but it is a task which is not impossible! After all, history has shown us that what may appear to be insoluble at the outset can be overcome in time with perseverance and persuasion — as was the case with the discovery of quantum mechanics nearly 100 years ago. That said, we fully acknowledge that this approach would only detect living systems similar to those present on Earth and that totally alien systems might exist which would fall outside this definition. We would, however, argue that they would be difficult to detect by any mechanism.
Evan Keane (University of Manchester)
Do we have too many neutron stars?
Recent studies of the transient radio sky have revealed new and exciting classes of object. These include Rotating Radio Transients (RRATs), Pulsating Ultra-cool Brown Dwarfs, transient radio emission from magnetars and periodic bursts from the Galatcic centre to name but a few. Here we focus on the discovery of RRATs. These are a new population of isolated neutron star discovered in the Parkes Multibeam Pulsar Survey. Emission from RRATs is in the form of infrequent, short bright bursts. They typically emit for less than 1second/day but the implications of their existence are very important. This is because of the huge predicted population of these hard to detect sources. For instance, there are thought to be more RRATs than radio pulsars! Examination of birthrates shows that with this discovery we seem to have neutron stars being born faster than the core-collapse supernova rate! Explaining this is a huge challenge for theory. The solution, whatever it may be, looks like it will shed light on neutron star evolution trends in RRATs as well as in the separate population of x-ray dim isolated neutron stars and in the so called magnetars.Julia Kennedy (University of Edinburgh)
Materials for Cutting-Edge Experiments in Astronomy and Particle Physics
Many exciting discoveries in Astronomy, Particle Physics and Gravitational Wave Research are expected. This research will require the use of advanced instruments, many of which will require cryostat operation at helium and sub-kelvin temperatures. Currently little is known about the behaviour of many materials at these temperatures, which is a necessity for construction.
My poster will show some current and future projects which use cryogenic operation as well as demonstrating the technique used for the material characterising experiments currently being carried out at the ROE.Jonathan Marshall (The Open University)
YSOs and Protoplanetary Discs in L1551
L1551, part of the Taurus-Auriga complex, is an extensively studied nearby region of low mass star formation. Spitzer IRAC (3.6 - 8.0µm) data were analysed in order to search for new YSO sources and characterise the extinction across the region at superior resolution and sensitivity than previously possible. 583 sources were detected in both [3.6] and [8.0] wavebands. The spectral index of these sources yielded over 200 YSO candidates. 156 of the 583 sources were found to be coincident with known 2MASS sources and could therefore be subjected to more detailed analysis. Combined Spitzer and 2MASS data enabled the luminosity function of sources in the region to be calculated (as a proxy for the initial mass function). A dozen new YSO sources have been discovered and fitted with model spectral energy distributions. Sources with high (>0) spectral index were found clustered in regions of high extinction.Iain McDonald (Keele University)
Mass Loss in the Globular Cluster omega Centauri
Omega Centauri is the largest Galactic globular cluster, well-known for its multiple-metallicity populations. We aim to characterise Population II giant branch mass loss and the reasons behind the lack of retention of inter-stellar medium by the cluster.
We have mapped omega Cen with Spitzer at wavelengths between 3.6 and 70 micron to identify dust-producing stars; follow-up of these has begun with recent 8-13 micron spectra obtained at Gemini-South of the two brightest giant branch members, for which we also have optical spectra.
We are also using the Spitzer imaging along with our new ATCA radio synthesis maps to try to understand the nature of the dusty and gaseous emission in the vicinity of omega Cen, which could relate to material in the process of leaving the cluster.James Mullaney (University of Durham)
Intermediate emission line regions of Narrow Line Seyfert 1 galaxies
Based on our new optical spectroscopic sample, we examine the kinematic properties of various emission line regions in narrow line Seyfert 1s (NLS1s), by modelling their profiles using multiple component fits. We interpret these results by comparison with equivalent components measured in the spectra of some broad line Seyfert 1s and a typical Seyfert 2 galaxy. We find that the Ha and Hb line profiles cannot be modelled using the traditional two gaussians typical for broad line Seyferts. We investigate the merits of Lorentzian-plus-gaussian and three-gaussian fits to these lines, and find that the latter provides a statistically better fit requiring the presence of a broad (>3000km/s, FWHM) component. This may correspond to a suppressed broad line region in NLS1s with similar kinematics to those of typical broad line Seyfert 1s.
From the profiles of the forbidden high ionisation lines in NLS1s, we find that they appear to trace an 'intermediate' velocity region with kinematics between the standard broad and narrow line regions. Additional evidence of this region is present in the profiles of the permitted Balmer lines. Finally, we note that despite having quite similar ionisation potentials, the relative intensities of the highly ionised lines of [Fe X]6374 and [FeXI]7892, display considerable dispersion from one galaxy to another. The interpretation of this requires further modelling, but suggests the possibility of using the ratio as a diagnostic to constrain the shape of the spectral energy distribution in the vicinity of ~100eV. A region which cannot be directly observed, but which may contribute significantly to the bolometric luminosity.Tim Rawle (University of Durham)
NUV-IR colours of local cluster red sequence galaxies
We present GALEX near-UV and 2MASS IR photometry for red sequence galaxies in local clusters. The samples are selected to exclude even low level emission. We analyse the NUV-J colour-magnitude relation (CMR) and find that the intrinsic scatter is an order of magnitude larger than for the analogous optical CMR, in agreement with previous studies. Comparing the NUV-J colours with spectroscopically-derived stellar population parameters, we find a strong correlation with metallicity, only a marginal trend with age, and no correlation with the alpha/Fe ratio. We explore the origin of the large scatter and conclude that neither aperture effects nor the UV upturn phenomenon contribute significantly. We show that the scatter could be attributed to simple 'frosting' by either a young or a low metallicity subpopulation.Alberto Rebassa Mansergas (University of Warwick)
Post Common Envelope Binaries from the SDSS
Close binaries containing a compact object make up a wide variety of objects such as white dwarf binaries, some of which are SN Ia progenitors, or close neutron star binaries, which are possible progenitors of short Gamma-Ray bursts. The evolution of all close binaries depends crucially on the rate at which angular momentum is extracted from the binary orbit. The two most important sources of angular momentum loss are the common envelope phase and magnetic braking. Both precesses are known for long but still poorly understood, and significant progress will only be achieved if they can be calibrated using innovate observational input. We are carrying out the first dedicated spectroscopic survey of white dwarf/main sequence binaries. By identifying in this sample those systems that have undergone a common envelope and measuring their binary parameters, we will provide the much needed constraints for further development of binary evolution theory. We have so far identified 55 new post common envelope binaries and measured 26 orbital periods.N. Robertson Rowell (University of Edinburgh)
Cool white dwarfs and the age of the galaxy
The coolest white dwarfs found in the galactic disc formed roughly 8 Gyr ago from the burnt out remains of the first stars, and have been cooling slowly ever since. Accurate cooling models can be used to wind the clock back to the earliest periods of star formation in the galactic disc, and combined with a large enough observational sample can be used to constrain the age of the disc to better than 0.5 Gyr. We present early efforts to identify and characterise a new sample of these 'ultracool' white dwarfs.Mairead Skelly (Imperial College London)
Mapping spots on young, cool stars
Observations of young stars are key to understanding stellar evolution. In my talk I will focus on T Tauri stars: the pre-main sequence equivalents of the Sun. They are 1 - 10 million years old and often support circumstellar disks out of which planets may form. T Tauri stars are highly variable, typically with lightcurve amplitudes of around 0.1 mag. The variability is caused by cool spots on the surface. These spots are equivalent to sunspots, but the large variabilities indicate that they are much bigger than sunspots. I will describe a technique called Doppler imaging which is used to produce maps of the spots. Such maps can provide useful information on the star. Firstly they can tell us about its magnetic field. Starspots form where magnetic field lines emerge through the surface of the star. Given the large variability observed in T Tauri stars we can infer that they are magnetically very active. By mapping the distribution of the spots we can find out more about the field. Secondly: by observing the starspots over a longer period we can investigate the rotational behaviour of the star. In the Sun the equator rotates more rapidly than the poles . This fact was discovered by observing sunspots as they cross the Solar disk: the spots at higher latitudes fall behind those near the equator. This "differential rotation" is responsible for the Sun's well-known 11-year cycle. By carrying out similar analysis on T Tauri stars we can investigate whether they have differential rotation too and a similar cycle to the Sun, or is the behaviour in the interiors of these young stars very different altogether?Anthony Smith (University of Sussex)
A census of K-band galaxies from the UKIDSS Large Area Survey
It is possible to learn a lot about a population's history by taking a census. The new near-infrared UKIDSS Large Area Survey (LAS), combined with its optical counterpart, the Sloan Digital Sky Survey, makes it possible to take a census of low-redshift galaxies focussing on the distribution of stellar mass, as revealed by the K-band light. I present some recent results looking at the luminosities and surface brightnesses of galaxies in the LAS.Paul Steele (University of Leicester)
White Dwarfs in UKIDSS: Sub-stellar companions and debris disks
We present a near-infrared (near-IR) photometric search for sub-stellar companions and debris disks around white dwarfs in the UKIRT Deep Sky Survey (UKIDSS). We cross-correlate the SDSS DR4 and McCook and Sion catalogues of white dwarfs with the UKIDSS DR1 and DR2 databases. A near-IR colour-colour diagram is then constructed to identify outliers with photometric excesses consistent with unresolved sub-stellar companions or debris disks. We present three possible very low mass companions and one candidate debris dust disk - perhaps the first detected around a hot (T=60,000K) helium atmosphere (DO) white dwarf.Xufen Wu (University of St Andrew's)
Escape from the MONDian Galaxies
In MOdified Newtonian Dynamics (MOND) the internal potential well of a galaxy is made shallower if considering the acceleration of the center of mass of the galaxy towards neighbouring galaxies. We numerically solve the modified Poisson equation of MOND, and show that the external acceleration of the Milky Way is consistent with the RAVE-observed 550 km/s escape speed for the solar neighbourhood stars. Moreover, we predict in galaxy clusters Low Surface Brightness (LSB) galaxy members are destroyed because of very shallow potential wells of these fast-accelerating satellites.The Local Organising Committee are keen to hear any questions or comments you might have ahead of the meeting and can be contacted at ras-yam@roe.ac.uk.