The promise of advanced technology for future air transports

Progress in all weather 4-D navigation and wake vortex attenuation research is discussed and the concept of time based metering of aircraft is recommended for increased emphasis. The far term advances in aircraft efficiency were shown to be skin friction reduction and advanced configuration types. The promise of very large aircraft, possibly all wing aircraft is discussed, as is an advanced concept for an aerial relay transportation system. Very significant technological developments were identified that can improve supersonic transport performance and reduce noise. The hypersonic transport was proposed as the ultimate step in air transportation in the atmosphere. Progress in the key technology areas of propulsion and structures was reviewed. Finally, the impact of alternate fuels on future air transports was considered and shown not to be a growth constraint

The Ks-band Luminosity and Stellar Mass Functions of Galaxies in z~1 Clusters

We present the near-infrared (Ks-band) luminosity function of galaxies in two z~1 cluster candidates, 3C336 and Q1335+28. A third cluster, 3C289, was observed but found to be contaminated by a foreground system. Our wide field imaging data reach to Ks=20.5 (5sigma), corresponding to ~M*+2.7 with respect to the passive evolution. The near-infrared luminosity traces the stellar mass of a galaxy due to its small sensitivity to the recent star formation history. Thus the luminosity function can be transformed to the stellar mass function of galaxies using the $J-K$ colours with only a small correction (factor<2) for the effects of on-going star formation. The derived stellar mass function spans a wide range in mass from ~3 x 10^{11}Msun down to ~6 x 10^{9}Msun (set by the magnitude limit). The form of the mass function is very similar to lower redshift counterparts such as that from 2MASS/LCRS clusters (Balogh et al. 2001) and the z=0.31 clusters (Barger et al. 1998). This indicates little evolution of galaxy masses from z=1 to the present-day. Combined with colour data that suggest star formation is completed early (z>>1) in the cluster core, it seems that the galaxy formation processes (both star formation and mass assembly) are strongly accerelated in dense environments and has been largely completed by z=1. We investigate whether the epoch of mass assembly of massive cluster galaxies is earlier than that predicted by the hierarchical galaxy formation models. These models predict the increase of characteristic mass by more than factor ~3 between z=1 and the present day. This seems incompatible with our data.Comment: 12 pages, including 12 figures, uses mn.sty and epsf.sty. Accepted for publication in MNRAS Main Journa

Galaxy bulges and their black holes: a requirement for the quenching of star formation

One of the central features of the last 8 to 10 billion years of cosmic history has been the emergence of a well-populated red sequence of non-star-forming galaxies. A number of models of galaxy formation and evolution have been devised to attempt to explain this behavior. Most current models require feedback from supermassive black holes (AGN feedback) to quench star formation in galaxies in the centers of their dark matter halos (central galaxies). Such models make the strong prediction that all quenched central galaxies must have a large supermassive black hole (and, by association, a prominent bulge component). I show using data from the Sloan Digital Sky Survey that the observations are consistent with this prediction. Over 99.5% of red sequence galaxies with stellar masses in excess of 10^{10} M_{\sun} have a prominent bulge component (as defined by having a Sersic index n above 1.5). Those very rare red sequence central galaxies with little or no bulge (n<1.5) usually have detectable star formation or AGN activity; the fraction of truly quenched bulgeless central galaxies is <0.1% of the total red sequence population. I conclude that a bulge, and by implication a supermassive black hole, is an absolute requirement for full quenching of star formation in central galaxies. This is in agreement with the most basic prediction of the AGN feedback paradigm.Comment: 6 pages, 4 color figures (figure 1 is of slightly degraded quality). To appear in August 1 edition of the Astrophysical Journa

Reconstructing the History of Star Formation in Rich Cluster Cores

We address the current crucial issues on the formation and evolution of cluster galaxies: ie., connection between the Butcher-Oemler effect, assembly of cluster galaxies, truncation of star formation, and the origin of S0 galaxies. We construct the field corrected colour-magnitude (CM) diagrams for 7 CNOC clusters (0.23<z<0.43) and Coma, and illustrate the evolution of the complete cluster population down to the present-day based on the model in which star formation is truncated when the galaxies infall from the surrounding field. We show that the blue galaxies are incorporated into the present-day tight CM relation as they fade and become redder after the truncation, which is possibly responsible for producing faint S0's (>M*+1). Truncation of star formation is, however, found to be relatively milder (with a time scale of 1 Gyr) than suggested by the viorent processes such as ram-pressure stripping and/or mergers/harassment. The BO effect is after all found to be a combination of three effects, namely, increasing field star formation activity, increasing galaxy infall rate, and the truncatin of star formation after the accretion. Our approach naturally leads to the history of galaxy assembly and `global' star foramtion for `cluster' galaxies.Comment: 20 pages, 12 figures, Accepted for Publication in MNRAS (first submitted on 9th Feb 2000

The millimetre variability of M81* -- Multi-epoch dual frequency mm-observations of the nucleus of M81

There are still many open questions as to the physical mechanisms at work in Low Luminosity AGN that accrete in the extreme sub-Eddington regime. Simultaneous multi-wavelength studies have been very successful in constraining the properties of SgrA*, the extremely sub-Eddington black hole at the centre of our Milky Way. M81*, the nucleus of the nearby spiral galaxy M81, is an ideal source to extend the insights obtained on SgrA* toward higher luminosity AGN. Here we present observations at 3 and 1 mm that were obtained within the framework of a coordinated,multi-wavelength campaign on M81*. The continuum emission from M81* was observed during three epochs with the IRAM Plateau de Bure Interferometer simultaneously at wavelengths of 3 and 1 mm. We present the first flux measurements of M81* at wavelengths around 1 mm. We find that M81* is a continuously variable source with the higher variability observed at the shorter wavelength. Also, the variability at 3 and 1 mm appears to be correlated. Like SgrA*, M81* appears to display the strongest flux density and variability in the mm-to-submm regime. There remains still some ambiguity concerning the exact location of the turnover frequency from optically thick to optically thin emission. The observed variability time scales point to an upper size limit of the emitting region of the order 25 Schwarzschild radii. The data show that M81* is indeed a system with very similar physical properties to SgrA* and an ideal bridge toward high luminosity AGN. The data obtained clearly demonstrate the usefulness and, above all, the necessity of simultaneous multi-wavelength observations of LLAGN.Comment: accepted for publication in A&

The First Detailed X-ray Observations of High-Redshift, Optically-Selected Clusters: XMM-Newton Results for Cl 1324+3011 at z = 0.76 and Cl 1604+4304 at z = 0.90

We present the first detailed X-ray observations of optically-selected clusters at high redshift. Two clusters, Cl 1324+3011 at z = 0.76 and Cl 1604+4304 at z = 0.90, were observed with XMM-Newton. The optical center of each cluster is coincident with an extended X-ray source whose emission is detected out to a radius of 0.5 Mpc. The emission from each cluster appears reasonably circular, with some indication of asymmetries and more complex morphologies. Similarly to other optically-selected clusters at redshifts of z > 0.4, both clusters are modest X-ray emitters with bolometric luminosities of only Lx = 1.4 - 2.0 x 10^(44) erg/s. We measure gas temperatures of T = 2.88 (+0.71/-0.49) keV for Cl 1324+3011 and 2.51 (+1.05/-0.69) keV for Cl 1604+4304. The X-ray properties of both clusters are consistent with the high-redshift Lx-T relation measured from X-ray-selected samples at z > 0.5. However, based on the local relations, their X-ray luminosities and temperatures are low for their measured velocity dispersions (sigma). The clusters are cooler by a factor of 2 - 9 compared to the local sigma-T relation. We briefly discuss the possible explanations for these results.Comment: 14 pages, 4 figures; accepted for publication in Astrophysical Journal Letters; version with full resolution figures available at http://bubba.ucdavis.edu/~lubin/xmm.pd

Tony Harrison in Nigeria: Teacher, Translator and Dramatist

Tony Harrison, famously born and bred in Leeds, was a Lecturer at Ahmadu Bello University in Northern Nigeria from 1962 to 1966. Harrison’s notebooks show that his earliest experiments with Northern Englishes and dialects were carried out in Nigeria at this time. His letters and notebooks also reflect his interest in languages and traditions of the region. Harrison was also fascinated with questions of spoken language, dialect, slang and swearing, and collected widely to prepare for his teaching, including lists of onomatopoeic words in Hausa, Yoruba, Igbo, Igala and Igbirra. This article draws on documents held in the extensive Tony Harrison Archive held at the Brotherton Library at the University of Leeds to highlight Harrison’s extraordinary interest in speech and performance in Nigeria, including his experiments with dialect, speech and slang. It is suggested that these experiments did not only shape Harrison’s early writing, but were formative for his subsequent literary practice, both as a poet and dramatist. The article shows that Harrison’s early work in Nigeria is crucial to understanding the poetics and politics of his later work, moving away from the established binaries of current literary scholarship which remains dominated by the tension between his working-class background and grammar school education

Color bimodality: Implications for galaxy evolution

We use a sample of 69726 galaxies from the SDSS to study the variation of the bimodal color-magnitude (CM) distribution with environment. Dividing the galaxy population by environment (Sigma_5) and luminosity (-23<M_r<-17), the u-r color functions are modeled using double-Gaussian functions. This enables a deconvolution of the CM distributions into two populations: red and blue sequences. The changes with increasing environmental density can be separated into two effects: a large increase in the fraction of galaxies in the red distribution, and a small color shift in the CM relations of each distribution. The average color shifts are 0.05+-0.01 and 0.11+-0.02 for the red and blue distributions, respectively, over a factor of 100 in projected neighbor density. The red fraction varies between about 0% and 70% for low-luminosity galaxies and between about 50% and 90% for high-luminosity galaxies. This difference is also shown by the variation of the luminosity functions with environment. We demonstrate that the effects of environment and luminosity can be unified. A combined quantity, Sigma_mod = Sigma_5/Mpc^{-2} + L_r/L_{-20.2}, predicts the fraction of red galaxies, which may be related to the probability of transformation events. Our results are consistent with major interactions (mergers and/or harassment) causing galaxies to transform from the blue to the red distribution. We discuss this and other implications for galaxy evolution from earlier results and model the effect of slow transformations on the color functions.Comment: 14 pages, 8 figures, in AIP Conf. Proc., The New Cosmology, eds. R. E. Allen et al. (aka. The Mitchell Symposium), see http://proceedings.aip.org/proceedings/confproceed/743.jsp ; v2: replaced Figure 5 which was incomplete in original submissio