The Future of Direct Supermassive Black Hole Mass Estimates

(Abridged) The repeated discovery of supermassive black holes (SMBHs) at the centers of galactic bulges, and the discovery of relations between the SMBH mass (M) and the properties of these bulges, has been fundamental in directing our understanding of both galaxy and SMBH formation and evolution. However, there are still many questions surrounding the SMBH - galaxy relations. For example, are the scaling relations linear and constant throughout cosmic history, and do all SMBHs lie on the scaling relations? These questions can only be answered by further high quality direct M estimates from a wide range in redshift. In this paper we determine the observational requirements necessary to directly determine SMBH masses, across cosmological distances, using current M modeling techniques. We also discuss the SMBH detection abilities of future facilities. We find that if different M modeling techniques, using different spectral features, can be shown to be consistent, then both 30 m ground- and 16 m space-based telescopes will be able to sample M 1e9Msol across ~95% of cosmic history. However, we find that the abilities of ground-based telescopes critically depend on future advancements in adaptive optics systems; more limited AO systems will result in limited effective spatial resolutions, and forces observations towards the near-infrared where spectral features are weaker and more susceptible to sky features. Ground-based AO systems will always be constrained by relatively bright sky backgrounds and atmospheric transmission. The latter forces the use of multiple spectral features and dramatically impacts the SMBH detection efficiency. The most efficient way to advance our database of direct SMBH masses is therefore through the use of a large (16 m) space-based UVOIR telescope.Comment: PASP Accepte

Seeing the sky through Hubble's eye: The COSMOS SkyWalker

Large, high-resolution space-based imaging surveys produce a volume of data that is difficult to present to the public in a comprehensible way. While megapixel-sized images can still be printed out or downloaded via the World Wide Web, this is no longer feasible for images with 10^9 pixels (e.g., the Hubble Space Telescope Advanced Camera for Surveys [ACS] images of the Galaxy Evolution from Morphology and SEDs [GEMS] project) or even 10^10 pixels (for the ACS Cosmic Evolution Survey [COSMOS]). We present a Web-based utility called the COSMOS SkyWalker that allows viewing of the huge ACS image data set, even through slow Internet connections. Using standard HTML and JavaScript, the application successively loads only those portions of the image at a time that are currently being viewed on the screen. The user can move within the image by using the mouse or interacting with an overview image. Using an astrometrically registered image for the COSMOS SkyWalker allows the display of calibrated world coordinates for use in science. The SkyWalker "technique" can be applied to other data sets. This requires some customization, notably the slicing up of a data set into small (e.g., 256^2 pixel) subimages. An advantage of the SkyWalker is the use of standard Web browser components; thus, it requires no installation of any software and can therefore be viewed by anyone across many operating systems.Comment: 4 pages, 2 figures, accepted for publication in PAS

A new extensive catalog of optically variable AGN in the GOODS Fields and a new statistical approach to variability selection

Variability is a property shared by practically all AGN. This makes variability selection a possible technique for identifying AGN. Given that variability selection makes no prior assumption about spectral properties, it is a powerful technique for detecting both low-luminosity AGN in which the host galaxy emission is dominating and AGN with unusual spectral properties. In this paper, we will discuss and test different statistical methods for the detection of variability in sparsely sampled data that allow full control over the false positive rates. We will apply these methods to the GOODS North and South fields and present a catalog of variable sources in the z band in both GOODS fields. Out of 11931 objects checked, we find 155 variable sources at a significance level of 99.9%, corresponding to about 1.3% of all objects. After rejection of stars and supernovae, 139 variability selected AGN remain. Their magnitudes reach down as faint as 25.5 mag in z. Spectroscopic redshifts are available for 22 of the variability selected AGN, ranging from 0.046 to 3.7. The absolute magnitudes in the rest-frame z-band range from ~ -18 to -24, reaching substantially fainter than the typical luminosities probed by traditional X-ray and spectroscopic AGN selection in these fields. Therefore, this is a powerful technique for future exploration of the evolution of the faint end of the AGN luminosity function up to high redshifts.Comment: Accepted for publication in The Astrophysical Journal (version 2: minor changes to text after receiving comments

Analysis of the SFR - M* plane at z<3: single fitting versus multi-Gaussian decomposition

The analysis of galaxies on the star formation rate - stellar mass (SFR-M*) plane is a powerful diagnostic for galaxy evolution at different cosmic times. We consider a sample of 24463 galaxies from the CANDELS/GOODS-S survey to conduct a detailed analysis of the SFR-M* relation at redshifts 0.5$\leqslant z<$3 over more than three dex in stellar mass. To obtain SFR estimates, we utilise mid- and far-IR photometry when available, and rest-UV fluxes for all the other galaxies. We perform our analysis in different redshift bins, with two different methods: 1) a linear regression fitting of all star-forming galaxies, defined as those with specific star formation rates $\rm log_{10}(sSFR/yr^{-1}) > -9.8$, similarly to what is typically done in the literature; 2) a multi-Gaussian decomposition to identify the galaxy main sequence (MS), the starburst sequence and the quenched galaxy cloud. We find that the MS slope becomes flatter when higher stellar mass cuts are adopted, and that the apparent slope change observed at high masses depends on the SFR estimation method. In addition, the multi-Gaussian decomposition reveals the presence of a starburst population which increases towards low stellar masses and high redshifts. We find that starbursts make up ~5% of all galaxies at z=0.5-1.0, while they account for ~16% of galaxies at 2$<z<$3 with log$_{10}(M^{*})=$8.25-11.25. We conclude that the dissection of the SFR-M* in multiple components over a wide range of stellar masses is necessary to understand the importance of the different modes of star formation through cosmic time.Comment: 15 pages, 12 figures, 1 table. Accepted for publication in A&A, after addressing referee report. Main changes with respect to v1: two new appendixes to investigate the impact of redshift outliers and to test a two-Gaussian component fit to the sSFR distribution. No conclusion change

Die vraag na 'verstaan' in die Christologie van D Bonhoeffer

'Understanding' in the Christology of D BonhoefferThere has been a change in the approach to hermeneutics, with the result that it is no longer considered merely auxihary to exegesis, but is seen as a basic science, the central problem of the so-called new understanding of Scriptures. In the study of Dogmatics this opens new visions. In this regard Bonhoeffer asked certain questions, of which some are still important today. Characteristic of Bonhoeffer is that man, who has 'come of age' and is 'a-religious', is of decisive importance in the construction of a Christology. To 'save' the 'Gospel' in a world that has 'come of age', a new understanding of Scriptures is necessary, and this must be done in an a-religious way. The only question is whether he did not lose both the uniqueness of the Christian revelation and faith and the reality that is central to Christianity

Padveiligheid: Teologies-etiese opmerkings by enkele navorsingsprojekte in verband met die verkeersituasie in die RSA

Road safety: Observations of a theological-ethical nature on a few research projects concerning the traffic situation in the RSASouth Africa has an unacceptably high incidence of traffic deaths and serious injuries. Statistics feature among the highest in the world in relation to population; 15,3 percent per 100 000 people. This article suggests that all the churches in South Africa should be called upon to get involved by way of their own ecclesiastical methods and ways. Not only the functions of the church offices should be emphasised, but also the calling of each and every member of the congregation, including the youth. In this regard special attention is given to the theological-ethical contents of the message of the churches

Oop of geslote Nagmaalsviering? ’n Vraag aan die Nederduitsch Hervormde Kerk van Afrika

Open or closed Communion? A question addressed to the Nederduitsch Hervormde Kerk van AfrikaThis article focuses on the open invitation to partake in the Lord’s Supper, according to the prescription of the Nederduitsch Hervormde Kerk. Fundamentally, Holy Communion is not there for the individual. It is given to the community. Neither is the Lord’s Supper the place to practise church discipline; it is the place where the liberating presence of the crucified Lord is celebrated. For this reason, proper preaching must lead to the Lord’s Supper, and not away from it. The conclusion is that the Nederduitsch Hervormde Kerk should take the question of an open invitation to the Lord’s Supper seriously

A prospective evaluation of emergency patients presenting to 8-hour primary care clinics.

Includes abstract. Includes bibliographical references

Die betekenis van die kerklike dogma

The meaning of the dogmaBecause dogmatic decisions of the past are not guaranteed to remain relevant for contemporary temptations and attacks, and because the dogma is by intrinsically relative to the Word of God, this article argues that a critical interpre tation of the dogma is essential. The purpose of such a critical interpretation must be to keep dogma relevant and alive. Therefore questions like the origin of the dogma, the essence of the dogma, the hermeneutics of the dogma and the task of dogmatics, should be answered