Reionization Constraints on the Contribution of Primordial Compact Objects to Dark Matter

Many lines of evidence suggest that nonbaryonic dark matter constitutes roughly 30% of the critical closure density, but the composition of this dark matter is unknown. One class of candidates for the dark matter is compact objects formed in the early universe, with typical masses M between 0.1 and 1 solar masses to correspond to the mass scale of objects found with microlensing observing projects. Specific candidates of this type include black holes formed at the epoch of the QCD phase transition, quark stars, and boson stars. Here we show that accretion onto these objects produces substantial ionization in the early universe, with an optical depth to Thomson scattering out to z=1100 of approximately tau=2-4 [f_CO\epsilon_{-1}(M/Msun)]^{1/2} (H_0/65)^{-1}, where \epsilon_{-1} is the accretion efficiency \epsilon\equiv L/{\dot M}c^2 divided by 0.1 and f_CO is the fraction of matter in the compact objects. The current upper limit to the scattering optical depth, based on the anisotropy of the microwave background, is approximately 0.4. Therefore, if accretion onto these objects is relatively efficient, they cannot be the main component of nonbaryonic dark matter.Comment: 12 pages including one figure, uses aaspp4, submitted to Ap

Deprojection of Rich Cluster Images

We consider a general method of deprojecting 2D images to reconstruct the 3D structure of the projected object, assuming axial symmetry. The method consists of the application of the Fourier Slice Theorem to the general case where the axis of symmetry is not necessarily perpendicular to the line of sight, and is based on an extrapolation of the image Fourier transform into the so-called cone of ignorance. The method is specifically designed for the deprojection of X-ray, Sunyaev-Zeldovich (SZ) and gravitational lensing maps of rich clusters of galaxies. For known values of the Hubble constant, H0, and inclination angle, the quality of the projection depends on how exact is the extrapolation in the cone of ignorance. In the case where the axis of symmetry is perpendicular to the line of sight and the image is noise-free, the deprojection is exact. Given an assumed value of H0, the inclination angle can be found by matching the deprojected structure out of two different images of a given cluster, e.g., SZ and X-ray maps. However, this solution is degenerate with respect to its dependence on the assumed H0, and a third independent image of the given cluster is needed to determine H0 as well. The application of the deprojection algorithm to upcoming SZ, X-ray and weak lensing projected mass images of clusters will serve to determine the structure of rich clusters, the value of H0, and place constraints on the physics of the intra-cluster gas and its relation to the total mass distribution.Comment: 7 pages, LaTeX, 2 Postscript figures, uses as2pp4.sty. Accepted for publication in ApJ Letters. Also available at: http://astro.berkeley.edu:80/~squires/papers/deproj.ps.g

Dark baryons and rotation curves

The best measured rotation curve for any galaxy is that of the dwarf spiralXXXX DDO 154, which extends out to about 20 disk scale lengths. It provides an ideal laboratory for testing the universal density profile prediction from high resolution numerical simulations of hierarchical clustering in cold dark matter dominated cosmological models. We find that the observed rotation curve cannot be fit either at small radii, as previously noted, or at large radii. We advocate a resolution of this dilemma by postulating the existence of a dark spheroid of baryons amounting to several times the mass of the observed disk component and comparable to that of the cold dark matter halo component. Such an additional mass component provides an excellent fit to the rotation curve provided that the outer halo is still cold dark matter-dominated with a density profile and mass-radius scaling relation as predicted by standard CDM-dominated models. The universal existence of such dark baryonic spheroidal components provides a natural explanation of the universal rotation curves observed in spiral galaxies, may have a similar origin and composition to the local counterpart that has been detected as MACHOs in our own galactic halo via gravitational microlensing, and is consistent with, and even motivated by, primordial nucleosynthesis estimates of the baryon fraction.Comment: 16 pages LaTeX, 2 postscript figures. To be published in The Astrophysical Journal, Letter

Evaluational adjectives

This paper demarcates a theoretically interesting class of "evaluational adjectives." This class includes predicates expressing various kinds of normative and epistemic evaluation, such as predicates of personal taste, aesthetic adjectives, moral adjectives, and epistemic adjectives, among others. Evaluational adjectives are distinguished, empirically, in exhibiting phenomena such as discourse-oriented use, felicitous embedding under the attitude verb `find', and sorites-susceptibility in the comparative form. A unified degree-based semantics is developed: What distinguishes evaluational adjectives, semantically, is that they denote context-dependent measure functions ("evaluational perspectives")—context-dependent mappings to degrees of taste, beauty, probability, etc., depending on the adjective. This perspective-sensitivity characterizing the class of evaluational adjectives cannot be assimilated to vagueness, sensitivity to an experiencer argument, or multidimensionality; and it cannot be demarcated in terms of pretheoretic notions of subjectivity, common in the literature. I propose that certain diagnostics for "subjective" expressions be analyzed instead in terms of a precisely specified kind of discourse-oriented use of context-sensitive language. I close by applying the account to `find x PRED' ascriptions

GMOS Spectroscopy of SCUBA Galaxies Behind A851

We have identified counterparts to two submillimeter (submm) sources, SMM J09429+4659 and SMM J09431+4700, seen through the core of the z=0.41 cluster Abell 851. We employ deep 1.4-GHz observations and the far-infrared/radio correlation to refine the submm positions and then optical and near-infrared imaging to locate their counterparts. We identify an extremely red counterpart to SMM J09429+4659, while GMOS spectroscopy with Gemini-North shows that the R=23.8 radio source identified with SMM J09431+4700 is a hyperluminous infrared galaxy (L_FIR~1.5x10^13 L_sun) at z=3.35, the highest spectroscopic redshift so far for a galaxy discovered in the submm. The emission line properties of this galaxy are characteristic of a narrow-line Seyfert-1, although the lack of detected X-ray emission in a deep XMM-Newton observation suggests that the bulk of the luminosity of this galaxy is derived from massive star formation. We suggest that active nuclei, and the outflows they engender, may be an important part of the evolution of the brightest submm galaxies at high redshifts.Comment: to appear in the Oct 1 issue of ApJ Letter

The Black Hole Mass - Galaxy Bulge Relationship for QSOs in the SDSS DR3

We investigate the relationship between black hole mass and host galaxy velocity dispersion for QSOs in Data Release 3 of the Sloan Digital Sky Survey. We derive black hole mass from the broad Hbeta line width and continuum luminosity, and the bulge stellar velocity dispersion from the [OIII] narrow line width. At higher redshifts, we use MgII and [OII] in place of Hbeta and [OIII]. For redshifts z < 0.5, our results agree with the black hole mass - bulge velocity dispersion relationship for nearby galaxies. For 0.5 < z < 1.2, this relationship appears to show evolution with redshift in the sense that the bulges are too small for their black holes. However, we find that part of this apparent trend can be attributed to observational biases, including a Malmquist bias involving the QSO luminosity. Accounting for these biases, we find ~0.2 dex evolution in the black hole mass-bulge velocity dispersion relationship between now and redshift z ~ 1.Comment: Accepted by ApJ, 15 pages, 9 figure

Early Growth and Efficient Accretion of Massive Black Holes at High Redshift

Black-hole masses of the highest redshift quasars (4 <~ z <~ 6) are estimated using a previously presented scaling relationship, derived from reverberation mapping of nearby quasars, and compared to quasars at lower redshift. It is shown that the central black holes in luminous z >~ 4 quasars are very massive (>~ 10^9 solar masses). It is argued that the mass estimates of the high-z quasars are not subject to larger uncertainties than those for nearby quasars. Specifically, the large masses are not overestimates and the lack of similarly large black-hole masses in the nearby Universe does not rule out their existence at high-z. However, AGN host galaxies do not typically appear fully formed or evolved at these early epochs. This supports scenarios in which black holes build up mass very fast in a radiatively inefficient (or obscured) phase relative to the stars in their galaxies. Additionally, upper envelopes of black-hole mass of approximately 10^{10} solar masses and bolometric luminosity of ~ 10^{48} erg/s are observed at all redshifts.Comment: 17 pages including 7 figures (5 in color) and 1 table. To appear in ApJ, v600, January 1, 200

Probing spin-charge separation in a Tomonaga-Luttinger liquid

In a one-dimensional (1D) system of interacting electrons, excitations of spin and charge travel at different speeds, according to the theory of a Tomonaga-Luttinger Liquid (TLL) at low energies. However, the clear observation of this spin-charge separation is an ongoing challenge experimentally. We have fabricated an electrostatically-gated 1D system in which we observe spin-charge separation and also the predicted power-law suppression of tunnelling into the 1D system. The spin-charge separation persists even beyond the low-energy regime where the TLL approximation should hold. TLL effects should therefore also be important in similar, but shorter, electrostatically gated wires, where interaction effects are being studied extensively worldwide.Comment: 11 pages, 4 PDF figures, uses scicite.sty, Science.bs

Ribbons on the CBR Sky: A Powerful Test of a Baryon Symmetric Universe

If the Universe consists of domains of matter and antimatter, annihilations at domain interfaces leave a distinctive imprint on the Cosmic Background Radiation (CBR) sky. The signature is anisotropies in the form of long, thin ribbons of width $\theta_W\sim 0.1^\circ$, separated by angle $\theta_L\simeq 1^\circ(L/100h^{-1}{Mpc})$ where L is the characteristic domain size, and y-distortion parameter $y \approx 10^{-6}$. Such a pattern could potentially be detected by the high-resolution CBR anisotropy experiments planned for the next decade, and such experiments may finally settle the question of whether or not our Hubble volume is baryon symmetric.Comment: LaTeX, 10 pages, 4 figures in epsf. Revised version corrects a couple of relevant mistake

Positrons from particle dark-matter annihilation in the Galactic halo: propagation Green's functions

We have made a calculation of the propagation of positrons from dark-matter particle annihilation in the Galactic halo in different models of the dark matter halo distribution using our 3D code, and present fits to our numerical propagation Green's functions. We show that the Green's functions are not very sensitive to the dark matter distribution for the same local dark matter energy density. We compare our predictions with computed cosmic ray positron spectra (``background'') for the ``conventional'' CR nucleon spectrum which matches the local measurements, and a modified spectrum which respects the limits imposed by measurements of diffuse Galactic gamma-rays, antiprotons, and positrons. We conclude that significant detection of a dark matter signal requires favourable conditions and precise measurements unless the dark matter is clumpy which would produce a stronger signal. Although our conclusion qualitatively agrees with that of previous authors, it is based on a more realistic model of particle propagation and thus reduces the scope for future speculations. Reliable background evaluation requires new accurate positron measurements and further developments in modelling production and propagation of cosmic ray species in the Galaxy.Comment: 8 pages, 6 ps-figures, 3 tables, uses revtex. Accepted for publication in Physical Review D. More details can be found at http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm