The evolutionary sequence of active galactic nuclei and galaxy formation revealed

Today, almost every galaxy spheroid contains a massive black hole: a remnant of, and testament to, a period in its evolution when it contained an active galactic nucleus (AGN). However, the sequence and timescales of the formation of the black hole and surrounding spheroid of stars are completely unknown, leaving a large gap in our knowledge of how the universe attained its present appearance. Here we present submillimeter observations of matched samples of X-ray absorbed and unabsorbed AGNs that have luminosities and redshifts characteristic of the sources responsible for most of the mass in present-day black holes. Strong submillimeter emission, an isotropic signature of copious star formation, is found only in the X-ray–absorbed sample, ruling out orientation effects as the cause of the absorption. The space density and luminosity range of the X-ray–absorbed AGNs indicate that they are undergoing the transition between a hidden growth phase and an unabsorbed AGN phase and imply that the X-ray–absorbed period in the AGN's evolution coincides with the formation of the galaxy spheroid

Comparative Study of the Application of Chelating Resins for Rare Earth Recovery

The adsorption properties of chelating ion exchange resins containing mixed sulfonic/phosphonic (SP), aminophosphonic (AP) or iminodiacetic (IDA) acid functional groups were investigated towards the rare earth elements (REE). The aim of this work was to determine the potential for such resins to assist in the isolation of a mixed rare earth product under conditions relevant to the hydrometallurgical processing of rare earth containing minerals. The selectivity of the resins towards La, Sm and Ho, versus the common impurity metals; Al, Fe and Th, was determined in sulfuric acid media. The chelating resins all displayed a similar selectivity with Fe and Th adsorbed in preference to the REE and Al (i.e.Th≃ Fe>> REE≃ Al). The IDA resin displayed a far superior performance compared to both phosphonic resins (SP and AP) as well as a strong acid cation exchange resin for the adsorption of REE in the presence of very high Na or Ca concentrations. Equilibrium and kinetic adsorption isotherms for La were measured and successfully modelled with all resins, and the elution characteristics of selected resins investigated in both batch and column operation. A number of areas were identified where these resins could be exploited to provide an advantage in the hydrometallurgical processing of RE

Freak observers and the measure of the multiverse

I suggest that the factor $p_j$ in the pocket-based measure of the multiverse, $P_j=p_j f_j$, should be interpreted as accounting for equilibrium de Sitter vacuum fluctuations, while the selection factor $f_j$ accounts for the number of observers that were formed due to non-equilibrium processes resulting from such fluctuations. I show that this formulation does not suffer from the problem of freak observers (also known as Boltzmann brains).Comment: 6 pages, no figures; references adde

Catching NGC4051 in the low state with XMM-Newton

The Narrow Line Seyfert 1 galaxy NGC4051 shows unusual low flux states, lasting several months, when the 2-10 keV X-ray spectrum becomes unusually hard (photon index<1) while the spectrum at lower X-ray energies is dominated by a large soft excess. A Chandra TOO of the low state has shown that the soft excess and hard components are variable and well-correlated. The variability of the hard component rules out an origin in a distant reflector. Here we present results from a recent XMM-Newton TOO of NGC4051 in the low state, which allows a much more detailed examination of the nature of the hard and soft spectral components in the low state. We demonstrate that the spectral shape in the low state is consistent with the extrapolation of the spectral pivoting observed at higher fluxes. The XMM-Newton data also reveals the warm absorbing gas in emission, as the drop in the primary continuum flux unmasks prominent emission lines from a range of ion species.Comment: 4 pages, 4 figures. Proc. of the meeting: "The Restless High-Energy Universe" (Amsterdam, The Netherlands), E.P.J. van den Heuvel, J.J.M. in 't Zand, and R.A.M.J. Wijers Ed

Superstars and Giant Gravitons in M-theory

Following hep-th/0109127, we show that a certain class of BPS naked singularities (superstars) found in compactifications of M-theory can be interpreted as being composed of giant gravitons. More specifically, we study superstars which are asymptotically AdS_7 x S^4 and AdS_4 x S^7 and show that these field configurations can be interpreted as being sourced by continuous distributions of spherical M2- and M5-branes, respectively, which carry internal momenta and have expanded on the spherical component of the space-time.Comment: 13 page

FIRI - a Far-Infrared Interferometer

Half of the energy ever emitted by stars and accreting objects comes to us in the FIR waveband and has yet to be properly explored. We propose a powerful Far-InfraRed Interferometer mission, FIRI, to carry out high-resolution imaging spectroscopy in the FIR. This key observational capability is essential to reveal how gas and dust evolve into stars and planets, how the first luminous objects in the Universe ignited, how galaxies formed, and when super-massive black holes grew. FIRI will disentangle the cosmic histories of star formation and accretion onto black holes and will trace the assembly and evolution of quiescent galaxies like our Milky Way. Perhaps most importantly, FIRI will observe all stages of planetary system formation and recognise Earth-like planets that may harbour life, via its ability to image the dust structures in planetary systems. It will thus address directly questions fundamental to our understanding of how the Universe has developed and evolved - the very questions posed by ESA's Cosmic Vision.Comment: Proposal developed by a large team of astronomers from Europe, USA and Canada and submitted to the European Space Agency as part of "Cosmic Vision 2015-2025

Optical and X-ray Observations of M31N 2007-12b: An Extragalactic Recurrent Nova with a Detected

We report combined optical and X-ray observations of nova M31N 2007-12b. Optical spectroscopy obtained 5 days after the 2007 December outburst shows evidence of very high ejection velocities (FWHM H$\alpha \simeq 4500$ km s$^{-1}$). In addition, Swift X-ray data show that M31N 2007-12b is associated with a Super-Soft Source (SSS) which appeared between 21 and 35 days post-outburst and turned off between then and day 169. Our analysis implies that M_{\rm WD} \ga 1.3 M$_{\odot}$ in this system. The optical light curve, spectrum and X-ray behaviour are consistent with those of a recurrent nova. Hubble Space Telescope observations of the pre-outburst location of M31N 2007-12b reveal the presence of a coincident stellar source with magnitude and color very similar to the Galactic recurrent nova RS Ophiuchi at quiescence, where the red giant secondary dominates the emission. We believe that this is the first occasion on which a nova progenitor system has been identified in M31. However, the greatest similarities of outburst optical spectrum and SSS behaviour are with the supposed Galactic recurrent nova V2491 Cygni. A previously implied association of M31N 2007-12b with nova M31N 1969-08a is shown to be erroneous and this has important lessons for future searches for recurrent novae in extragalactic systems. Overall, we show that suitable complementary X-ray and optical observations can be used not only to identify recurrent nova candidates in M31, but also to determine subtypes and important physical parameters of these systems. Prospects are therefore good for extending studies of recurrent novae into the Local Group with the potential to explore in more detail such important topics as their proposed link to Type Ia Supernovae.Comment: 10 pages, 4 figures, accepted for publication in the Astrophysical Journal. This paper - which replaces the original accepted paper - accounts for the positional coincidence of M31N 2007-12b and M31N 1969-08a and uses additional HST archival dat

The Seyfert-LINER Galaxy NGC 7213: An XMM-Newton Observation

We examine the XMM X-ray spectrum of the LINER-AGN NGC 7213, which is best fit with a power law, K-alpha emission lines from Fe I, Fe XXV and Fe XXVI and a soft X-ray collisionally ionised thermal plasma with kT=0.18 +0.03/-0.01 keV. We find a luminosity of 7x10^(-4) L_Edd, and a lack of soft X-ray excess emission, suggesting a truncated accretion disc. NGC 7213 has intermediate X-ray spectral properties, between those of the weak AGN found in the LINER M81 and higher luminosity Seyfert galaxies. This supports the notion of a continuous sequence of X-ray properties from the Galactic Centre through LINER galaxies to Seyferts, likely determined by the amount of material available for accretion in the central regions.Comment: 7 pages, 2 figures. To appear in From X-ray Binaries to Quasars: Black Hole Accretion on All Mass Scales, ed. T. J. Maccarone, R. P. Fender, and L. C. Ho (Dordrecht: Kluwer

Classical and Thermodynamic Stability of Black Branes

It is argued that many non-extremal black branes exhibit a classical Gregory-Laflamme instability if, and only if, they are locally thermodynamically unstable. For some black branes, the Gregory-Laflamme instability must therefore disappear near extremality. For the black $p$-branes of the type II supergravity theories, the Gregory-Laflamme instability disappears near extremality for $p=1,2,4$ but persists all the way down to extremality for $p=5,6$ (the black D3-brane is not covered by the analysis of this paper). This implies that the instability also vanishes for the near-extremal black M2 and M5-brane solutions.Comment: 21 pages, LaTeX. v2: Various points clarified, typos corrected and reference adde

Supersymmetry without Supersymmetry

We present four-dimensional M-theory vacua with N>0 supersymmetry which, from the perspective of perturbative Type IIA string theory, have N=0. Such vacua can appear when the compactifying 7-manifold is a U(1) fibration. The missing superpartners are Dirichlet 0-branes. Someone unable to detect Ramond-Ramond charge would thus conclude that these worlds have no unbroken supersymmetry. In particular, the gravitinos (and also some of the gauge bosons) are 0-branes not seen in perturbation theory but which curiously remain massless however weak the string coupling.Comment: Latex, 16 pages. Minor revisions and reference adde