Near-Infrared Photometry of the High-Redshift Quasar RDJ030117+002025: Evidence for a Massive Starburst at z=5.5

With a redshift of z=5.5 and an optical blue magnitude M_B ~ -24.2 mag (~4.5 10^12 L_sun), RDJ030117+002025 is the most distant optically faint (M_B > -26 mag) quasar known. MAMBO continuum observations at lambda=1.2 mm (185 micrometer rest-frame) showed that this quasar has a far-IR luminosity comparable to its optical luminosity. We present near-infrared J- and K-band photometry obtained with NIRC on the Keck I telescope, tracing the slope of the rest frame UV spectrum of this quasar. The observed spectral index is close to the value of alpha_nu ~ -0.44 measured in composite spectra of optically-bright SDSS quasars. It thus appears that the quasar does not suffer from strong dust extinction, which further implies that its low rest-frame UV luminosity is due to an intrinsically-faint AGN. The FIR to optical luminosity ratio is then much larger than that observed for the more luminous quasars, supporting the suggestion that the FIR emission is not powered by the AGN but by a massive starburst.Comment: 6 pages, APJ in pres

A Molecular Einstein Ring: Imaging a Starburst Disk Surrounding a Quasi-Stellar Object

Images of the CO 2-1 line emission, and the radio continuum emission, from the redshift 4.12 gravitationally lensed quasi-stellar object (QSO) PSS J2322+1944 reveal an Einstein ring with a diameter of 1.5". These observations are modeled as a star forming disk surrounding the QSO nucleus with a radius of 2 kpc. The implied massive star formation rate is 900 M_sun/year. At this rate a substantial fraction of the stars in a large elliptical galaxy could form on a dynamical time scale of 10^8 years. The observation of active star formation in the host galaxy of a high-redshift QSO supports the hypothesis of coeval formation of supermassive black holes and stars in spheroidal galaxies.Comment: 12 pages. to appear in Science, April 200

Thermodynamics of Dyonic Lifshitz Black Holes

Black holes with asymptotic anisotropic scaling are conjectured to be gravity duals of condensed matter system close to quantum critical points with non-trivial dynamical exponent z at finite temperature. A holographic renormalization procedure is presented that allows thermodynamic potentials to be defined for objects with both electric and magnetic charge in such a way that standard thermodynamic relations hold. Black holes in asymptotic Lifshitz spacetimes can exhibit paramagnetic behavior at low temperature limit for certain values of the critical exponent z, whereas the behavior of AdS black holes is always diamagnetic.Comment: 26 pages, 4 figure

Large N gauge theories and topological cigars

We analyze the conjectured duality between a class of double-scaling limits of a one-matrix model and the topological twist of non-critical superstring backgrounds that contain the N=2 Kazama-Suzuki SL(2)/U(1) supercoset model. The untwisted backgrounds are holographically dual to double-scaled Little String Theories in four dimensions and to the large N double-scaling limit of certain supersymmetric gauge theories. The matrix model in question is the auxiliary Dijkgraaf-Vafa matrix model that encodes the F-terms of the above supersymmetric gauge theories. We evaluate matrix model loop correlators with the goal of extracting information on the spectrum of operators in the dual non-critical bosonic string. The twisted coset at level one, the topological cigar, is known to be equivalent to the c=1 non-critical string at self-dual radius and to the topological theory on a deformed conifold. The spectrum and wavefunctions of the operators that can be deduced from the matrix model double-scaling limit are consistent with these expectations.Comment: 34 page

Double Scaling Limits and Twisted Non-Critical Superstrings

We consider double-scaling limits of multicut solutions of certain one matrix models that are related to Calabi-Yau singularities of type A and the respective topological B model via the Dijkgraaf-Vafa correspondence. These double-scaling limits naturally lead to a bosonic string with c $\leq$ 1. We argue that this non-critical string is given by the topologically twisted non-critical superstring background which provides the dual description of the double-scaled little string theory at the Calabi-Yau singularity. The algorithms developed recently to solve a generic multicut matrix model by means of the loop equations allow to show that the scaling of the higher genus terms in the matrix model free energy matches the expected behaviour in the topological B-model. This result applies to a generic matrix model singularity and the relative double-scaling limit. We use these techniques to explicitly evaluate the free energy at genus one and genus two.Comment: 32 pages, 3 figure

Rock glaciers and paraglacial features influence stream invertebrates in a deglaciating Alpine area

This is the pre-peer reviewed version of the following article: Brighenti, S, Tolotti, M, Bertoldi, W, Wharton, G, Bruno, MC. Rock glaciers and paraglacial features influence stream invertebrates in a deglaciating Alpine area. Freshwater Biology. 2020; 00: 1– 14. https://doi.org/10.1111/fwb.13658, which has been published in final form at https://doi.org/10.1111/fwb.13658. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions

Phase transition and hyperscaling violation for scalar Black Branes

We investigate the thermodynamical behavior and the scaling symmetries of the scalar dressed black brane (BB) solutions of a recently proposed, exactly integrable Einstein-scalar gravity model [1], which also arises as compactification of (p-1)-branes with a smeared charge. The extremal, zero temperature, solution is a scalar soliton interpolating between a conformal invariant AdS vacuum in the near-horizon region and a scale covariant metric (generating hyperscaling violation on the boundary field theory) asymptotically. We show explicitly that for the boundary field theory this implies the emergence of an UV length scale (related to the size of the brane), which decouples in the IR, where conformal invariance is restored. We also show that at high temperatures the system undergoes a phase transition. Whereas at small temperature the Schwarzschild-AdS BB is stable, above a critical temperature the scale covariant, scalar-dressed BB solution, becomes energetically preferred. We calculate the critical exponent z and the hyperscaling violation parameter of the scalar-dressed phase. In particular we show that the hyperscaling violation parameter is always negative. We also show that the above features are not a peculiarity of the exact integrable model of Ref.[1], but are a quite generic feature of Einstein-scalar and Einstein-Maxwell-scalar gravity models for which the squared-mass of the scalar field is positive and the potential vanishes exponentially as the scalar field goes to minus infinity.Comment: 20 pages, 4 figures. In the revised version it has been pointed out that the Einstein-scalar gravity model considered in the paper also arises as compactification of black p-branes with smeared charge

Radio Observations of Infrared Luminous High Redshift QSOs

We present Very Large Array (VLA) observations at 1.4 GHz and 5 GHz of a sample of 12 Quasi-stellar Objects (QSOs) at z = 3.99 to 4.46. The sources were selected as the brightest sources at 250 GHz from the recent survey of Omont et al. (2001). We detect seven sources at 1.4 GHz with flux densities, S_{1.4} > 50 microJy. These centimeter (cm) wavelength observations imply that the millimeter (mm) emission is most likely thermal dust emission. The radio-through-optical spectral energy distributions for these sources are within the broad range defined by lower redshift, lower optical luminosity QSOs. For two sources the radio continuum luminosities and morphologies indicate steep spectrum, radio loud emission from a jet-driven radio source. For the remaining 10 sources the 1.4 GHz flux densities, or limits, are consistent with those expected for active star forming galaxies. If the radio emission is powered by star formation in these systems, then the implied star formation rates are of order 1e3 M_solar/year. We discuss the angular sizes and spatial distributions of the radio emitting regions, and we consider briefly these results in the context of co-eval black hole and stellar bulge formation in galaxies.Comment: to appear in the A