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The SAAO is at a geographically crucial site in the southern hemisphere between South America and Australasia. SAAO has a long history of involvement in infrared and optical astronomy that dates back almost two hundred years. The observatory expects to continue contributing to astronomical research for many years to come, using its small (0.5m, 0.75m, 1.0m and 1.9m) telescopes and their various instruments (ranging from spectroscopy to polarimetry and high-speed photometry), together with the Southern African Large Telescope (SALT) and other hosted international telescopes. In this paper, I discuss the capabilities and uses of the SAAO small telescopes, and the challenges that threaten astronomical research at the observatory, including light pollution and other emerging threats to the usually dust-free and dark-night-sky site at Sutherland. This is mitigated by the legislation called the Astronomy Geographic Advantage (AGA) Act of 2007 that protects the observatory from these threats.
The angular momenta of rarefied preplanetesimals needed for formation of small-body binaries can be obtained at collisions of preplanetesimals. Trans-Neptunian objects, including trans-Neptunian binaries, could be formed from contracting rarefied preplanetesimals.
This talk covers preliminary work in which we apply a strictly differential line-by-line chemical abundance analysis to high quality UVES spectra of the globular cluster NGC 6752. We achieve extremely high precision in the measurement of relative abundance ratios. Our results indicate that the observed abundance dispersion exceeds the measurement uncertainties and that many pairs of elements show significant correlations when plotting [X1/H] vs. [X2/H]. Our tentative conclusions are that either NGC 6752 is not chemically homogeneous at the ≃0.03 dex level or the abundance variations and correlations signify star-to-star He abundance variations.
We discuss the roles of protostellar outflow feedback in cluster formation using observational data of nearby cluster-forming regions like rho Oph, NGC1333, and Serpens. The observations suggest that observed protostellar outflow feedback appears to be sufficient both to maintain supersonic turbulence and to dynamically support the parent cluster-forming clumps. However, it is not enough to destroy the parent clumps by the current outflow activity. This implies that star formation process may not be too short and probably last at least for several local dynamical times.
We carry out a multi-wavelength analysis of star forming galaxies in the massive cluster MS0451.6-0305 at z∼0.54 to shed light on the evolution of the far-infrared-radio relationship in rich clusters. We have performed Spectral Energy Distribution (SED) fitting of IRAC 3.6μ, IRAC 4.5μ and MIPS 24μ photometry from Spitzer to derive the total infrared bolometric luminosity of spectroscopically confirmed cluster members with radio counterparts. The radio flux densities were measured from deep Very Large Array (VLA) radio continuum observations. The relationship between the infrared and radio luminosities for our sources show the strong correlation found between these two parameters for star forming galaxies. The far-infrared to radio luminosity ratio (qIR) values measured for these sources are comparable to those measured in low redshift clusters and indicative of an excess of radio emission.
We summarise the results of observing faint cataclysmic variables from the Catalina Real-Time Transient Survey, resulting in confirming the theoretically predicted maximum in the orbital period histogram near a period of 80 minutes.
Quiet-Sun magnetic fields are enigmatic in terms of their properties, and their origin is not well understood. One likely possibility is that they are a consequence of interactions with turbulent convective motions of various temporal and spatial scales. Here we investigate the relationship between small-scale magnetic fields and various convection flows. We demonstrate that in addition to granulation and supergranulation, mesogranulation also plays an important role in structuring quiet-Sun magnetic fields. We also study the vector magnetic fields in the quiet Sun, and propose that emerging granular-scale bipolar loops are major sources of the quiet-Sun magnetic fields.
I highlight three results from cosmological hydrodynamic simulations that yield a realistic red sequence of galaxies: 1) Major galaxy mergers are not responsible for shutting off star-formation and forming the red sequence. Starvation in hot halos is. 2) Massive galaxies grow substantially (~ × 2 in mass) after being quenched, primarily via minor (1:5) mergers. 3) Hot halo quenching naturally explains why galaxies are red when they either (a) are massive or (b) live in dense environments.
We extensively investigate the terrestrial planetary formation for the inclined planetary systems (considering the OGLE-2006-BLG-109L system as example) in the late stage. In the simulations, we show that the occurrence of terrestrial planets appears to be common in the final assembly stage. Moreover, we find that a lot of runs finally occupy at least one planet in the habitable zone (HZ). On the other hand, the numerical results also indicate that the inner region of the planetesimal disk, ranging from ~ 0.1 to 0.3 AU, plays an important role in building up terrestrial planets. The outcomes suggest that it may exist moderate possibility for the inclined systems to harbor terrestrial planets in the HZ.
Luminous Red Galaxies (LRGs) have old, red stellar populations often interpreted as evidence of a formation scenario in which these galaxies form in a single intense burst of star formation at high redshift. By measuring the average age of LRGs at two different redshifts, one can potentially measure the redshift interval corresponding to a time interval and thus measure the Hubble parameter H(z) ≈ −(1 + z)−1 Δ z/Δt (as in Jimenez & Loeb). The goal of this project is to measure directly the expansion rate of the universe at the redshift range 0.1 < z < 1.0 within 3% precision. We explore the age-dating of Sloan Digital Sky Survey LRGs using the stellar population models of Lick absorption line indices after stacking spectra in redshift bins to increase the signal-to-noise. We also use the method of full spectral fitting to measure the ages of LRGs observed with the Southern Africa Large Telescope (SALT).
We present a large-scale view of the magnetic field (MF) in the central 3° × 2° region of our Galaxy. There is a smooth transition of the large-scale MF configuration in this region.
Magnetic helicity is a physical quantity that describes field topology. It is also a conserved quantity as Berger in 1984 demonstrated that the total magnetic helicity is still conserved in the corona even when there is a fast magnetic reconnection. It is generally believed that solar magnetic fields, together with their helicity, are created in the convection zone by various dynamo processes. These fields and helicity are transported into the corona through solar photosphere and finally released into the interplanetary space via various processes such as coronal mass ejections (CMEs) and solar winds. Here I will give a brief review on our recent works, first on helicity observations on the photosphere and how to understand these observations via dynamo models. Mostly, I will talk about what are the possible consequences of magnetic helicity accumulation in the corona, namely, the formation of magnetic flux ropes, CMEs taking place as an unavoidable product of coronal evolution, and flux emergences as a trigger of CMEs. Finally, I will address on in what a form magnetic field in the interplanetary space would accommodate a large amount of magnetic helicity that solar dynamo processes have been continuously producing.
We present a multiwavelength photometric analysis of the innermost (3×3 kpc2) Globular Clusters (GCs) of M87. Their Spectral Energy Distributions (SEDs) were built with J and Ks imaging obtained with NaCo at the VLT, along with HST UV-optical archival data. Using both Galatic GC templates and stellar population models, we derived ages (> 10 Gyr) and metallicities ([Fe/H]~ −0.7) for these clusters (e.g: Cohen et al. 1998). These GCs have lower metallicities than its host galaxy. This agrees with the idea that the GC population formed earlier than the bulk of the stars.
We briefly present recent progress using the ASH code to model in 3-D the solar convection, dynamo and its coupling to the deep radiative interior. We show how the presence of a self-consistent tachocline influences greatly the organization of the magnetic field and modifies the thermal structure of the convection zone leading to realistic profiles of the mean flows as deduced by helioseismology.
Using known frequencies of the twin peak high-frequency quasiperiodic oscillations (HF QPOs) and known mass M of the central black hole, the black-hole dimensionless spin a can be determined assuming a concrete version of the resonance model. However, large range of observationally limited values of the black hole mass implies a low precision of the spin estimates. We discuss the possibility of higher precision of the black hole spin a measurements in the framework of multi-resonance model inspired by observations of more than two HF QPOs in some black hole sources. We determine the spin and mass dependence of the twin peak frequencies with a general rational ratio n:m assuming a non-linear resonance of oscillations with the epicyclic and Keplerian frequencies or their combinations. In the multi-resonant model, the twin peak resonances are combined properly to give the observed frequency set. We focus on the special case of duplex frequencies, when the top, bottom, or mixed frequency is common at two different radii where the resonances occur giving triple frequency sets.
Massive galaxies with old stellar populations have been put forwards as a challenge to models in which cosmic structures grow hierarchically through gravitational instability. I will explain how the growth of massive galaxies is helped by features of hierarchical models. I give a brief outline of how the galaxy formation process is modelled in hierarchical cosmologies using semi-analytical models, and illustrate how these models can be refined as our understanding of processes such as star formation improves. I then present a brief survey of the current state of play in the modelling of massive galaxies and list some outstanding challenges.
The fast growing number of science data repositories is opening enormous possibilities to scientists all over the world. The emergence of citizen science projects is engaging in science discovery a large number of citizens globally. Astronomical research is now a possibility to anyone having a computer and some form of data access. This opens a very interesting and strategic possibility to engage large audiences in the making and understanding of science. On another perspective it would be only natural to imagine that soon enough data mining will be an active part of the academic path of university or even secondary schools students. The possibility is very exciting but the road not very promising. Even in the most developed nations, where all schools are equipped with modern ICT facilities the use of such possibilities is still a very rare episode. The Galileo Teacher Training Program GTTP, a legacy of IYA2009, is participating in some of the most emblematic projects funded by the European Commission and targeting modern tools, resources and methodologies for science teaching. One of this projects is Discover the Cosmos which is aiming to target this issue by empowering educators with the necessary skills to embark on this innovative path: teaching science while doing science.
We develop the technique of ionization parameter mapping (IPM) to probe the optical depth of Hii regions, applying our method to the Magellanic Clouds. Our results dramatically clarify the radiative transfer in these galaxies. Based on Sii, Oiii, and Hα imaging from the Magellanic Clouds Emission Line Survey, we find that the frequency of optically thin objects correlates strongly with Hα luminosity and correlates inversely with Hi column density. The aggregate escape fraction for the Lyman continuum is sufficient to ionize the diffuse, warm ionized medium, but the galactic escape fraction is dominated by the few largest Hii regions. The quantitative trends are similar in both the LMC and SMC in spite of their different star formation and Hi properties.
Comets generally stay long in the sky and can be seen from many places on the surface of the Earth. We are interested in historical comets which were observed at plural sites. We have shown in a previous work (Tanikawa & Sôma, 2008) that in the seventh century, five comets were observed independently in China and Japan. From this fact and other data, we deduced that Japanese observational astronomy started in the seventh century. We know that, other than China and Japan, Korea and Vietnam had observational astronomy before the 9th century. We look for historical comets observed at plural sites by surveying the existing literature of respective countries. Examining the independence of the records, we provide a list of comets observed independently at plural sites. This strengthens the reliability of the records of comets. The list can be used for other purposes.