Distances from Surface Brightness Fluctuations

The practice of measuring galaxy distances from their spatial fluctuations in surface brightness is now a decade old. While several past articles have included some review material, this is the first intended as a comprehensive review of the surface brightness fluctuation (SBF) method. The method is conceptually quite simple, the basic idea being that nearby (but unresolved) star clusters and galaxies appear "bumpy", while more distant ones appear smooth. This is quantified via a measurement of the amplitude of the Poisson fluctuations in the number of unresolved stars encompassed by a CCD pixel (usually in an image of an elliptical galaxy). Here, we describe the technical details and difficulties involved in making SBF measurements, discuss theoretical and empirical calibrations of the method, and review the numerous applications of the method from the ground and space, in the optical and near-infrared. We include discussions of stellar population effects and the "universality" of the SBF standard candle. A final section considers the future of the method.Comment: Invited review article to appear in: `Post-Hipparcos Cosmic Candles', A. Heck & F. Caputo (Eds), Kluwer Academic Publ., Dordrecht, in press. 22 pages, including 3 postscript figures; uses Kluwer's crckapb.sty LaTex macro file, enclose

A First Comparison of the SBF Survey Distances with the Galaxy Density Field: Implications for H_0 and Omega

We compare the peculiar velocities measured in the SBF Survey of Galaxy Distances with the predictions from the density fields of the IRAS 1.2 Jy flux-limited redshift survey and the Optical Redshift Survey (ORS) to derive simultaneous constraints on the Hubble constant $H_0$ and the density parameter $\beta = \Omega^{0.6}/b$, where $b$ is the linear bias. We find $\beta_I=0.42^{+0.10}_{-0.06}$ and $\beta_O=0.26\pm0.08$ for the IRAS and ORS comparisons, respectively, and $H_0=74\pm4$ \kmsMpc (with an additional 9% uncertainty due to the Cepheids themselves). The match between predicted and observed peculiar velocities is good for these values of $H_0$ and $\beta$, and although there is covariance between the two parameters, our results clearly point toward low-density cosmologies. Thus, the unresolved discrepancy between the ``velocity-velocity'' and ``density-density'' measurements of $\beta$ continues.Comment: 4 pages with 3 embedded ps figures; uses emulateapj.sty (included). Accepted for publication in ApJ Letter

Potential of the Surface Brightness Fluctuations method to measure distances to dwarf elliptical galaxies in nearby clusters

The potential of the Surface Brightness Fluctuations (SBF) method to determine the membership of dwarf elliptical galaxies (dEs) in nearby galaxy clusters is investigated. Extensive simulations for SBF measurements on dEs in the I-band for various combinations of distance modulus, seeing and integration time are presented, based on average VLT FORS1 and FORS2 zero points. These show that for distances up to 20 Mpc (Fornax or Virgo cluster distance), reliable membership determination of dEs can be obtained down to very faint magnitudes -10<M_V<-12 mag (25 mag / arcsec^2) within integration times of the order of 1 hour and with good seeing. Comparing the limiting magnitudes of the method for the different simulated observing conditions we derive some simple rules to calculate integration time and seeing needed to reach a determined limiting magnitude at a given distance modulus for observing conditions different to the ones adopted in the simulations. Our simulations show a small offset of the order of 0.15 mag towards measuring too faint SBF. It is shown that this is due to loss of fluctuation signal when recovering pixel-to-pixel fluctuations from a seeing convolved image. To check whether our simulations represent well the behaviour of real data, SBF measurements for a real and simulated sample of bright Centaurus Cluster dEs are presented. They show that our simulations are in good agreement with the achievable S/N of SBF measurements on real galaxies.Comment: 12 pages, 8 figures, accepted by A&A, replaced by version with non-abridged bottom page limi

On surface brightness fluctuations: probabilistic and statistical bases I: Stellar population and theoretical SBF

This work aims to provide a theoretical formulation of Surface Brightness Fluctuations (SBF) in the framework of probabilistic synthesis models, and to distinguish between the different distributions involved in the SBF definition. RESULTS: We propose three definitions of SBF: (i) stellar population SBF, which can be computed from synthesis models and provide an intrinsic metric of fit for stellar population studies; (ii) theoretical SBF, which include the stellar population SBF plus an additional term that takes into account the distribution of the number of stars per resolution element psi(N); theoretical SBF coincide with Tonry & Schneider (1998) definition in the very particular case that psi(N) is assumed to be a Poisson distribution. However, the Poisson contribution to theoretical SBF is around 0.1% of the contribution due to the stellar population SBF, so there is no justification to include any reference to Poisson statistics in the SBF definition; (iii) observational SBF, which are those obtained in observations that are distributed around the theoretical SBF. Finally, we show alternative ways to compute SBF and extend the application of stellar population SBF to defining a metric of fitting for standard stellar population studies. CONCLUSIONS: We demostrate that SBF are observational evidence of a probabilistic paradigm in population synthesis, where integrated luminosities have an intrinsic distributed nature, and they rule out the commonly assumed deterministic paradigm of stellar population modeling.Comment: A&A accepte

The Infrared Surface Brightness Fluctuation Distances to the Hydra and Coma Clusters

We present IR surface brightness fluctuation (SBF) distance measurements to NGC 4889 in the Coma cluster and to NGC 3309 and NGC 3311 in the Hydra cluster. We explicitly corrected for the contributions to the fluctuations from globular clusters, background galaxies, and residual background variance. We measured a distance of 85 +/- 10 Mpc to NGC 4889 and a distance of 46 +/- 5 Mpc to the Hydra cluster. Adopting recession velocities of 7186 +/- 428 km/s for Coma and 4054 +/- 296 km/s for Hydra gives a mean Hubble constant of H_0 = 87 +/- 11 km/s/Mpc. Corrections for residual variances were a significant fraction of the SBF signal measured, and, if underestimated, would bias our measurement towards smaller distances and larger values of H_0. Both NICMOS on the Hubble Space Telescope and large-aperture ground-based telescopes with new IR detectors will make accurate SBF distance measurements possible to 100 Mpc and beyond.Comment: 24 pages, 4 PostScript figures, 2 JPEG images; accepted for publication in Ap

Asymmetric Drift and the Stellar Velocity Ellipsoid

We present the decomposition of the stellar velocity ellipsoid using stellar velocity dispersions within a 40 deg wedge about the major-axis (sigma_maj), the epicycle approximation, and the asymmetric drift equation. Thus, we employ no fitted forms for sigma_maj and escape interpolation errors resulting from comparisons of the major and minor axes. We apply the theoretical construction of the method to integral field data taken for NGC 3949 and NGC 3982. We derive the vertical-to-radial velocity dispersion ratio (sigma_z / sigma_R) and find (1) our decomposition method is accurate and reasonable, (2) NGC 3982 appears to be rather typical of an Sb type galaxy with sigma_z / sigma_R = 0.73 (+0.13/-0.11) despite its high surface brightness and small size, and (3) NGC 3949 has a hot disk with sigma_z / sigma_R = 1.18 (+0.36/-0.28).Comment: 4 pages including 3 figures, to appear in "Island Universes: Structure and Evolution of Disk Galaxies", Terschelling, Netherlands, July 3-8, 200

A CO Survey of Gravitationally Lensed Quasars with the IRAM Interferometer

We present the results of a CO survey of gravitationally lensed quasars, conducted with the Plateau de Bure Interferometer over the last three years. Among the 18 objects surveyed, one was detected in CO line emission, while six were detected in the continuum at 3mm and three in the continuum at 1mm. The low CO detection rate may at least in part be due to uncertainties in the redshifts derived from quasar broad emission lines. The detected CO source, the z=3.2 radio quiet quasar MG0751+2716, is quite strong in the CO(4-3) line and in the millimeter/submillimeter continuum, the latter being emission from cool dust. The integrated CO line flux is 5.96 +- 0.45 Jy.km/s, and the total molecular gas mass is estimated to be in the range M(H_2) = 1.6-3.1 X 10^9 solar masses.Comment: 5 pages, 2 figures, uses aa.cls and psfig.st

Discovery of Non-radial pulsations in PQ Andromedae

We have detected pulsations in time-series photometry of the WZ Sge dwarf nova PQ And. The strongest peak in the power spectrum occurs at a period of 10.5 minutes. Similar periods have been observed in other WZ Sge systems and are attributed to ZZ Ceti type non-radial pulsations. There is no indication in the photometry of an approximately 1.7 hour orbital period as reported in previous spectroscopic observations.Comment: 7 pages, 5 figure

Dark Matter Relic Abundance and Scalar-Tensor Dark Energy

Scalar-tensor theories of gravity provide a consistent framework to accommodate an ultra-light quintessence scalar field. While the equivalence principle is respected by construction, deviations from General Relativity and standard cosmology may show up at nucleosynthesis, CMB, and solar system tests of gravity. After imposing all the bounds coming from these observations, we consider the expansion rate of the universe at WIMP decoupling, showing that it can lead to an enhancement of the dark matter relic density up to few orders of magnitude with respect to the standard case. This effect can have an impact on supersymmetric candidates for dark matter.Comment: 12 pages, 13 figures; V2: references added, matches published versio