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Mapping the Galactic Free-Free Foreground via Interstellar Hα Emission
Reynolds R.J., Haffner L.M.
Recently completed Hα surveys of large portions of the sky can be used to create maps of the free-free intensity distribution at high Galactic latitude that are independent of the spectral fits to the CMB data. This provides an opportunity to test the accuracy of the spectral fitting procedures and to search for other sources of Galactic forground contamination that could be confused spectrally with the free-free, such as spinning dust grains. The Wisconsin Hα Mapper (WHAM) survey has sampled the sky north of declination −30° at about one degree angular resolution and has revealed that, except for a few isolated regions of enhanced emission, δTff (30 GHz) ≲ 30 μK at Galactic latitudes near 15°, decreasing to δTff(30 GHz) ≲ 4 μK at latitudes above 50°. Also in progress are Hα surveys that sample the sky at higher angular resolution.
Commissioning the Very Small Array
Rusholme B.
The Very Small Array (VSA) is a fourteen-element interferometer for sensitive measurement of the CMB anisotropies on scales of three degrees to ten arcminutes. The telescope is now observing on site in Tenerife after a period of commissioning, including the first map of the Sunyaev-Zel'dovich effect in the Coma cluster.A distinguishing feature of the instrument is that each antenna in the array tracks quasi-independently, providing a characteristic fringe rate per baseline which can be used to reject many systematics. This effect has been optimised in the antenna array design.
The TopHat Cosmic Microwave Background Anisotropy Experiment
Silverberg R.F.
We have developed a balloon-borne experiment to measure the Cosmic Microwave Background Radiation anisotropy on angular scales from ˜50° down to ˜20′. The instrument observes at frequencies between 150 and 690 GHz and will be flown on an Antarctic circumpolar long duration flight. To greatly improve the experiment performance, the front-end of the experiment is mounted on the top of the balloon. With high sensitivity, broad sky coverage, and well-characterized systematic errors, the results of this experiment can be used to strongly constrain cosmological models and probe the early stages of large-scale structure formation in the Universe.
Globular Clusters as Probes of the Virgo gE NGC 4472
Bridges T., Ashman K., Beasley M., Geisler D., Hanes D., Sharpies R., Zepf S.
We present radial velocities for 144 globular clusters (GCs) around the Virgo gE NGC 4472 (M49), and ages and metallicities for 131 GCs. We confirm our earlier finding that the metal-poor GCs have a significantly higher velocity dispersion than the metal-rich GCs, and we find little or no rotation in the metal-rich GCs. The velocity dispersion profile is consistent with isotropic GC orbits and the mass distribution inferred from X-ray data. Our sample of GCs spans a metallicity range of −1.6 ≤ [Fe/H] ≤ 0 dex. The metal-poor and metal-rich GCs are coeval within the errors, and all GCs older than 6 Gyr at 95% confidence.
The Very Small Array
Scott P.F.
The VSA is a 14-element aperture-synthesis telescope for mapping structure in the Cosmic Microwave Background which is now being commissioned at the Teide Observatory, Tenerife. It operates at frequencies between 26 and 36 GHz, with a bandwidth of 1.5GHz. Its elements track the sky, providing fringe-rate discrimination of any instrumental effects such as antenna cross-talk or ground radiation. The instrument incorporates a single-baseline interferometer comprising two large (3.7m) dishes, which is used to provide concurrent (and same frequency) pointed flux measurements of point sources in the VSA fields, the positions of these source having been obtained previously from survey observations made with the Cambridge Ryle Telescope at 15 GHz. The VSA is now completing its commissioning programme and it will start routine observations in September 2000.
First Year WMAP Observations
Bennett C.L.
The results of the first year WMAP sky survey are full sky microwave maps in five frequency bands from 23 to 94 GHz. Calibration errors are < 0.5% and the low systematic error level is well specified. The cosmic microwave background (CMB) is separated from the foregrounds using the multifrequency data. The 2 ≤ l ≤ 900 anisotropy power spectrum is cosmic variance limited for l < 354 with a signal-to-noise ratio >1 per mode to l = 658. The temperature-polarization cross-power spectrum reveals both acoustic features and a large angle correlation from reionization. The optical depth of reionization is τ = 0.17 ± 0.04. A best-fit cosmological model to the CMB and other measures of large scale structure works remarkably well with only a few parameters. The age of the best-fit universe is t0 = 13.7 ± 0.2 Gyr old. The matter density is Ωmh2 = 0.135+0.008--0.009, the baryon density is Ωbh2 = 0.0224 ± 0.0009, and the total mass-energy of the universe is Ωtot = 1.02±0.02. For WMAP data alone, ns = 0.99 ± 0.04. The lack of CMB fluctuation power on the largest angular scales reported by COBE and confirmed by WMAP is intriguing. WMAP continues to operate, so results will improve.
2MASS and the Nearby Universe
Huchra J., Martimbeau N., Jarrett T., Cutri R., Skrutskie M., Schneider S., Steining R., Macri L., Mader J., George T.
The Two Micron All-Sky Survey was conceived over a decade ago for the express purpose of mapping the Milky Way and the Universe nearby. 2MASS is now complete and the final data products, including the extended source catalog (XSC), have been released. The XSC contains nearly a million galaxies to the stated completeness goal of K=13.5. While the catalog becomes incomplete at the faintest magnitudes and lowest galactic latitudes due to confusion, at the bright end the catalog is essentially complete down to very low latitudes (b less than 5 degrees), which makes it an excellent survey for the distribution of matter in the nearby Universe. Redshift information is now nearly complete for the 24,000 galaxies brighter than K=11.25 and above |b|=5°. We now have an amazing census of galaxy (baryonic mass) concentrations over the whole sky and inside z=0.04. Several new structures are elucidated and the characteristics of the structures are described. We also examine the match between the predicted gravitational velocity vector of the Local Group and the motions determined by other experiments including the CMB dipole.
Dynamical Evolution of the Universe in the Quark-Hadron Phase Transition and Nugget Formation
Goyal A., Chandra D.
We study the dynamics of first-order phase transition in the early Universe when it was 10 −50μs old with quarks and gluons condensing into hadrons. We look at the evolution of the Universe in small as well as large super cooling scenario.
Bulk Motion of Galaxies and Hubble Flow Anisotropy on a Scale of 100 Mpc
Parnovsky S.L., Karachentseva V.E., Kudrya Y.N., Karachentsev I.D.
We study a large-scale bulk motion of thin edge-on spiral galaxies from the RFGC catalogue using a multipole decomposition of velocity field. The quadrupole and octupole components are statistically significant. The first one corresponds to the Hubble flow anisotropy, the second one leads to decrease of modulus of dipole component due to the strong dipole-octupole interaction.
Angular Distribution of Gamma-Ray Bursts: An Observational Probe of Cosmological Principle
Mészáros A., Balázs L.G., Vavrek R., Horváth I., Bagoly Z.
The test of the isotropy in the angular distribution of the gamma-ray bursts collected in BATSE Catalog (Meegan C. A. et al. 2000) is a test of cosmological principle itself, because the gamma-ray bursts are at cosmological distances. Several articles of the authors study this question (Balázs L. G., Mészáros A., & Horváth I., Astron. Astrophys., 339, 1, 1998; Balázs L. G., Mészáros A., Horváth I., & Vavrek R., Astron. Astrophys. Suppl., 138, 417, 1999; Mészáros A., Bagoly Z., & Vavrek R. Astron. Astrophys., 354, 1, 2000; Mészáros A., Bagoly Z., Horváth I., Balázs L.G. & Vavrek R. Astrophys. J., 539, 98, 2000). The final conclusion concerning the validity of isotropy is complicated both by instrumental effects and by the fact that there are three subgroups of gamma-ray bursts (“short”, “intermediate”, “long”; separation is done with respect to the duration of bursts). The long bursts are surely up to z ⋍ 4 (z is the redshift); for the remaining two subclasses the redshifts are unknown. The done tests of isotropy suggest (after the elimination of instrumental effects) the existence of anisotropy for the intermediate subclass on the confidence level > 95%. On the other hand, for the remaining two subclasses the situation is unclear; there is no unambiguous rejection of isotropy for them yet on the higher than 95% confidence level. If the bursts of intermediate subclass are at high z-s (say, at z > 0.1), then the validity of cosmological principle would be in serious doubt.
Radio Microlensing: Past, Present & Near Future
Koopmans L.V., de Bruyn A.G., Fassnacht C.D., Wambsganss J., Blandford R.D.
Strongly correlated non-intrinsic variability between 5 and 8.5 GHz has been observed in one of the lensed images of the gravitational lens B1600+434. These non-intrinsic (i.e. ‘external’) variations are interpreted as radio-micro-lensing of relativistic μas-scale jet components in the source at a redshift of z=1.59 by massive compact objects in the halo of the edge-on disk lens galaxy at z=0.41. We shortly summarize these observations and discuss several new observational and theoretical programs to investigate this new phenomenon in more detail.
The X-ray Background as a Cosmological Tool
Barcons X., Carrera F.J., Ceballos M.T.
We review the use of the X-ray background (XRB) as a cosmological tool with emphasis on three techniques: multipole analysis, autocorrelation functions and excess fluctuations. Although these methods of analysis of XRB fluctuations, and in particular the excess fluctuations method, are quite sensitive to cosmological parameters, the poor knowledge of a possibly redshift dependent bias parameter for the sources that dominate the X-ray background prevents the derivation of firm conclusions at present. Conversely, knowledge of the cosmological parameters could be used together with XRB fluctuations to assess the clustering properties of AGN as the dominant XRB sources.
Constraining the Cosmic Mass Density from the SBF Survey Peculiar Velocities
Blakeslee J.P., Tonry J.L., Dressler A., Ajhar E.A., Davis M., Willick J.A., Strauss M.A., Narayan V.K.
The recently completed I-band SBF Survey of Galaxy Distances contains about 300 galaxy distances within cz ≲ 4000 km/s. These data allow for good constraints on the local mass density and velocity fields. The mass density parameter βI ≡ Ω0.6/bI, where bI is the biasing factor of the IRAS redshift survey galaxies, is found to be βI ≍ 0.45.
Emergent Structure: the First Two Centuries of the First Two Eons
Trimble V.
“Early” maps of the cosmos included the 26th dynasty air god Shu supporting the sky goddess Nut above the earth god Geb, Descartes' Voronoi tesselation, William Herschel's star gauging, and Carl Charlier's 1922 plot of the nebulae in NGC, which he intended as observational support for the fractal nature of large scale cosmic structure (about which he was probably wrong, though right about there being more than one level of clustering). Because Shapley, van Maanen, and others were still denying the very existence of external galaxies at the same time that Lundmark and Opik were measuring their distances and masses and Charlier plotting hierarchies, the story of the discovery of very large scale structure (and streaming) in the universe cannot be told in perfectly linear fashion. There are, however, half a dozen or so discrete phases that can be recognized and three underlying themes, (1) expanding horizons, (2) additional levels of structure, and (3) increasing mediocrity of our vantage point.
Local Distance Indicators
Feast M.
A summary is given of the calibration of the Cepheid scale required in the derivation of distances from observations at V and I, as in the HST work on extragalactic Cepheids. There is some evidence that a small metallicity correction may be necessary in deriving distances in this way. The evidence for this comes both from observations of Cepheids of different metallicities and from a comparison of the LMC distance modulus derived from Cepheids and that derived by other methods.
Verifying the Use of Supernovae as Probes of the Cosmic Expansion
Ellis R., Sullivan M.
We present preliminary results of a follow-up survey which aims to characterise in detail those galaxies which hosted Type Ia supernovae found by the Supernova Cosmology Project. Our survey has two components: Hubble Space Telescope imaging with STIS and Keck spectroscopy with ESI, the goal being to classify each host galaxy into one of three broad morphological/spectral classes and hence to investigate the dependence of supernovae properties on host galaxy type over a large range in redshift. Of particular interest is the supernova Hubble diagram characterised by host galaxy class which suggests that most of the scatter arises from those occurring in late-type irregulars. Supernovae hosted by (presumed dust-free) E/SO galaxies closely follow the adopted SCP cosmological model. Although larger datasets are required, we cannot yet find any significant difference in the light curves of distant supernovae hosted in different galaxy types.
AMiBA: Array for Microwave Background Anisotropy
Lo K.Y., Chiueh T.H., Martin R.N., Ng K., Liang H., Pen U., Ma C.
As part of a 4-year Cosmology and Particle Astrophysics (CosPA) Research Excellence Initiative in Taiwan, AMiBA - a 19-element dual-channel 85-105 GHz interferometer array is being specifically built to search for high redshift clusters of galaxies via the Sunyaev-Zeldovich Effect (SZE). In addition, AMiBA will have full polarization capabilities, in order to probe the polarization properties of the Cosmic Microwave Background. AMiBA, to be sited on Mauna Kea in Hawaii or in Chile, will reach a sensitivity of ˜ 1 mJy or 7μK in 1 hour. The project involves extensive international scientific and technical collaborations. The construction of AMiBA is scheduled to starting operating in early 2004.
Cosmological Parameters from Eigenmode Analysis of Sloan Digital Sky Survey Galaxy Redshifts
Szalay A., Pope A., Matsubara T., Blanton M.R., Eisenstein D.J., Gray J., Jain B.
We present estimates of cosmological parameters from the application of the Karhunen-Loève transform to the analysis of the 3D power spectrum of density fluctuations using Sloan Digital Sky Survey galaxy redshifts. We use Ωmh and fb = Ωb/Ωm to describe the shape of the power spectrum, σL8g for the (linearly extrapolated) normalization, and β to parametrize linear theory redshift space distortions. on scales k ≤ 0.16hMpc--1, our maximum likelihood values are Ωmh = 0.264 ± 0.043, fb = 0.286 ± 0.065, σL8g = 0.966 ± 0.048, and β = 0.45 ± 0.12. When we take a prior on Ωb from WMAP, we find Ωmh = 0.207 ± 0.030, which is in excellent agreement with WMAP and 2dF. This indicates that we have reasonably measured the gross shape of the power spectrum but we have difficulty breaking the degeneracy between and Ωmh and fb because the baryon oscillations are not resolved in the current spectroscopic survey window function.
The Jodrell Bank - IAC 33 GHz Interferometer
Harrison D.L., Watson R.A., Rubiño-Martin J.A., Macias-Perez J.F., Davies R.D., Rebolo R., Gutiérrez C.M., Davis R.J.
This paper presents results obtained with the Jodrell Bank - IAC two-element 33 GHz interferometer, located at the Teide Observatory on Tenerife, which is designed to measure the level of the Cosmic Microwave Background (CMB) fluctuations on angular scales of 1° and 2°. The result from a maximum likelihood analysis of observations taken at Dec +41° of δTl = 63+7-6μK at l = 208 ± 18 is comparable with those of Boomerang and Maxima. The contribution of possible foreground contaminants are considered.
SWIRE and SIRTF Surveys
Lonsdale C.J.
The launch of SIRTF on August 25, 2003 opens an exciting new era for the infrared. Building on the legacy of IRAS, COBE & ISO, SIRTF will image the sky from 3.6–160 μm in tiered surveys, from wide (∼80 sq. deg.) reaching z∼1 in depth for L*FIR galaxies, to small, deep, confusion-limited surveys. SIRTF will measure the accumulation of stellar mass at high redshift, and the evolution of dusty systems (disks, starbursts & AGN) since z∼4, on size scales up to several hundred Mpc. The next decade will also see two major all-sky IR surveys, ASTRO-F and WISE (Wide-field Infrared Survey Explorer), and the launch of Herschel and Planck.
Ω0 Concordance
Fukugita M.
The determinations of the mass density parameter Ω0 are examined with a particular emphasis given to the new cosmic microwave background (CMB) experiments. It is shown that the Ω0 and the Hubble constant H0 from CMB are quite consistent with those from other observations with the aid of the hierarchical structure formation models based on cold dark matter dominance with the cosmological constant that makes the universe flat. The concordance value of Ω0 is 0.25-0.45.
Chandra and FUSE View of the WHIM: the Local Group and Beyond
Nicastro F.
In this contribution, I review the current observational evidence for the existence of filaments of Warm-Hot Intergalactic Medium (WHIM). In particular, I first focus on the controversial issue of the identification of the z ∼ 0 highly ionized far-ultraviolet (i.e. OVI) and X-ray (i.e. OVII, OVIII and NeIX) absorbers with either a very tenuous and diffuse WHIM filament, or with much denser condensations of material at large distances in the Galactic halo. I then present our recent detection (confidence level > 3σ) of the OVII WHIM at z > 0 and derive an estimate of the total number of baryons contained in this hard-to-detect phase of the IGM.
