118469851
PHOTOMETRIC REDSHIFTS OF SUBMILLIMETER GALAXIES
We use the photometric redshift method of Chakrabarti & McKee to infer photometric redshifts of submillimeter galaxies with far-IR (FIR) Herschel data obtained as part of the PACS Evolutionary Probe program. For the sample with spectroscopic redshifts, we demonstrate the validity of this method over a large range of redshifts (4 z 0.3) and luminosities, finding an average accuracy in (1 + z phot)/(1 + z spec) of 10%. Thus, this method is more accurate than other FIR photometric redshift methods. This method is different from typical FIR photometric methods in deriving redshifts from the light-to-gas mass (L/M) ratio of infrared-bright galaxies inferred from the FIR spectral energy distribution, rather than dust temperatures. To assess the dependence of our photometric redshift method on the data in this sample, we contrast the average accuracy of our method when we use PACS data, versus SPIRE data, versus both PACS and SPIRE data. We also discuss potential selection effects that may affect the Herschel sample. Once the redshift is derived, we can determine physical properties of infrared-bright galaxies, including the temperature variation within the dust envelope, luminosity, mass, and surface density. We use data from the GOODS-S field to calculate the star formation rate density (SFRD) of submillimeter bright sources detected by AzTEC and PACS. The AzTEC-PACS sources, which have a threshold 850 μm flux 5 mJy, contribute 15% of the SFRD from all ultraluminous infrared galaxies (L IR 1012 L ☉), and 3% of the total SFRD at z ~ 2.
118984787
A NEW PROBE OF THE DISTRIBUTION OF DARK MATTER IN GALAXIES
The scale radius of dark matter halos is a critical parameter for specifying the density distribution of dark matter, and is therefore a fundamental parameter for modeling galaxies. We develop here a novel, observationally motivated probe to quantitatively infer its value within the context of the Navarro, Frenk, & White profile. We demonstrate that disturbances in the extended atomic hydrogen gas disks of galaxies can be analyzed to infer the scale radius of the dark matter halo. Our primary metric is the phase (i.e., the shape of the spiral) of the m = 1 mode of the disturbance in the outskirts of the gas disk, which we take to be produced by a tidal interaction. We apply the method to the Whirlpool galaxy, which has an optically visible satellite. We infer a scale radius of ~17 kpc for M51, which is consistent with expectations from dissipationless cosmological simulations. We explore potential degeneracies due to orbital inclination, initial conditions, satellite mass, and pericenter approach distance, and find our results to be relatively insensitive to these considerations. Our method of tracing the dark potential well through observed disturbances in outer gas disks is complementary to gravitational lensing.
118956575
Simulating Merging Galaxies: The Infrared View
We calculate multi-wavelength spectral energy distributions (SEDs) (spanning optical to millimeter wavelengths) from simulations of major galaxy mergers using a three-dimensional radiative transfer code, which treats the absorption and scattering of radiation as well as the reemission from dust grains self-consistently. These calculations allow us to deduce correlations from the X-rays to millimeter wavelengths. We confirm observed correlations for Spitzer Space Telescope’s IRAC bands, as well as correlations observed in the IRAS era. We also make predictions that should be testable by future instruments. The power of the dynamical approach afforded by calculating fluxes from the merger simulations is that we can directly correlate observed clustering in the data as seen in IRAC color-color plots with the relative amount of time the system spends in a region of color-color space. We also present photo albums spanning the lifetime of SMGs, from its infancy in the pre-merger phase to its final stage as an elliptical galaxy, as seen in various bands. Finally, we compare the SEDs from the simulations to recent observations of SMGs. Our calculations, which match observed correlations both for local ULIRGs and higher redshift systems, suggest that simulations of major mergers with black hole feedback provide an excellent framework within which to understand the emission from local ULIRGs, and their high redshift cousins, the submillimeter galaxies.
119086181
Geodesic deviation in Regge calculus
Geodesic deviation is the most basic manifestation of the influence of gravitational fields on matter. We investigate geodesic deviation within the framework of Regge calculus, and compare the results with the continuous formulation of general relativity on two different levels. We show that the continuum and simplicial descriptions coincide when the cumulative effect of the Regge contributions over an infinitesimal element of area is considered. This comparison provides a quantitative relation between the curvature of the continuous description and the deficit angles of Regge calculus. The results presented might also be of help in developing generic ways of including matter terms in the Regge equations.
123616864
Tidal imprints of a dark subhalo on the outskirts of the Milky Way
We study the dynamical evolution of spiral structure in the stellar disks of isolated galaxies using high resolution Smoothed Particle Hydrodynamics (SPH) simulations that treat the evolution of gas, stars, and dark matter self-consistently. We focus this study on the question of self-excited spiral structure in the stellar disk and inves tigate the dynamical coupling between the cold, dissipative gaseous component and the stellar component. We find that angular momentum transport from the gas to the stars inside of corotation leads to a roughly time-steady spiral structure in the stellar disk. To make this point clea r, we contrast these results with otherwise identical simulations that do not include a cold gaseous component that is able to cool radiatively and dissipate energy, and find that spiral struc ture, when it is incipient, dies out more rapidly in simulations that do not include gas. We also employ a standard star formation prescription to convert gas into stars and find that our resul ts hold for typical gas consumption time scales that are in accord with the Kennicutt-Schmidt relation. We therefore attribute the long-lived roughly time steady spiral structure in the stel lar disk to the dynamical coupling between the gas and the stars and the resultant torques that t he self-gravitating gaseous disk is able to exert on the stars due to an azimuthal phase shift be tween the collisionless and dissipative components. Spiral galaxies present two faces to observers. When seen in blue light, these galaxies look disordered, with spurs, branche s and feather-like structures seen even in grand design galaxies , while K-band images show that these galaxies possess smooth, usually two-armed spiral patterns. We study here the dynamical interaction between the Population I component seen in blue light and the older Population II component revealed in the longer wavelengths, specifically with the intent of understanding how the intera ction between the gas and the stars affects the time evolution of spiral
116898833
Spectral energy distributions of embedded protostars and dusty galaxies
13926216
Asymptotic Quasinormal Modes of d-Dimensional Schwarzschild Black Hole with Gauss-Bonnet Correction
We obtain an analytic expression for the highly damped asymptotic quasinormal mode frequencies of the (d ≥ 5)-dimensional Schwarzschild black hole modified by the Gauss–Bonnet term, which appears in string derived models of gravity. The analytic expression is obtained under the string inspired assumption that there exists a minimum length scale in the system and in the limit when the coupling in front of the Gauss–Bonnet term in the action is small. Although there are several similarities of this geometry with that of the Schwarzschild black hole, the asymptotic quasinormal mode frequencies are quite different. In particular, the real part of the asymptotic quasinormal frequencies for this class of single horizon black holes is not proportional to log(3).
115177789
Scalar field dynamics in warped AdS3 black hole background
Abstract We study the normal modes of a scalar field in the background of a warped AdS 3 black hole which arises in topologically massive gravity. We discuss the normal mode spectrum using the brick wall boundary condition. In addition, we investigate the possibility of a more general boundary condition for the scalar field.
10835186
A comparative study of Dirac quasinormal modes of charged black holes in higher dimensions
In this work we study the Dirac quasinormal modes of higher dimensional charged black holes. Higher dimensional Reissner–Nordström type black holes as well as charged black holes in Einstein–Gauss–Bonnet theories are studied for fermionic perturbations using WKB method. A comparative study of the quasinormal modes in the two different theories of gravity has been performed. The behavior of the frequencies with the variation of black hole parameters as well as with the variation of space-time dimensions is studied. We also study the large multipole number limit of the black hole potential in order to look for an analytic expression for the frequencies.
118544491
Proof of universality of electrical conductivity at finite chemical potential
It was proposed in [1] that, for certain gauge theories with gravity duals, electrical conductivity at finite chemical potential is universal. Here we provide a general proof that, when matter stress tensor satisfies a compact constraint, electrical conductivity is universal. We further elaborate our result with several conformal as well as non-conformal gauge theories. We also discuss how boundary conductivity and universal conductivity of stretched horizon are related.
474602
Universal near-horizon conformal structure and black hole entropy
It is shown that a massless scalar probe reveals a universal near-horizon conformal structure for a wide class of black holes, including the BTZ. The central charge of the corresponding Virasoro algebra contains information about the black hole. With a suitable quantization condition on the central charge, the CFT associated with the black hole in our approach is consistent with the recent observation of Witten, where the dual theory for the BTZ in the AdS/CFT framework has been identified with the construction of Frenkel, Lepowsky and Meurman. This CFT admits the Fischer–Griess monster group as its symmetry. The logarithm of the dimension of a specific representation of the monster group has been identified by Witten as the entropy of the BTZ black hole. Our algebraic approach shows that a wide class of black holes share the same near-horizon conformal structure as that for the BTZ. With a suitable quantization condition, the CFT's for all these black holes in our formalism can be identified with the FLM model, although not through the AdS/CFT correspondence. The corresponding entropy for the BTZ provides a lower bound for the entropy of this entire class of black holes.