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Galaxies Survey (galaxy + survey)
Selected AbstractsVariations in 24-,m morphologies among galaxies in the Spitzer Infrared Nearby Galaxies Survey: new insights into the Hubble sequenceMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007G. J. Bendo ABSTRACT To study the distribution of star formation and dust emission within nearby galaxies, we measured five morphological parameters in the 3.6- and 24-,m wavebands for 65 galaxies in the Spitzer Infrared Nearby Galaxies Survey (SINGS) and eight galaxies that were serendipitously observed by SINGS. The morphological parameters demonstrate strong variations along the Hubble sequence, including statistically significant differences between S0/a-Sab and Sc-Sd galaxies. Early-type galaxies are generally found to be compact, centralized, symmetric sources in the 24-,m band, while late-type galaxies are generally found to be extended, asymmetric sources. These results suggest that the processes that increase the real or apparent sizes of galaxies' bulges also lead to more centralized 24-,m dust emission. Several phenomena, such as strong nuclear star formation, Seyfert activity, or outer ring structures, may cause galaxies to deviate from the general morphological trends observed at 24 ,m. We also note that the 24-,m morphologies of Sdm-Im galaxies are quite varied, with some objects appearing very compact and symmetric but others appearing diffuse and asymmetric. These variations reflect the wide variation in star formation in irregular galaxies as observed at other wavelengths. The variations in the 24-,m morphological parameters across the Hubble sequence mirror many of the morphological trends seen in other tracers of the ISM and in stellar emission. However, the 24-,m morphological parameters for the galaxies in this sample do not match the morphological parameters measured in the stellar wavebands. This implies that the distribution of dust emission is related to but not equivalent to the distribution of stellar emission. [source] The SCUBA Local Universe Galaxy Survey , II.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2001m data: evidence for cold dust in bright IRAS galaxies This is the second in a series of papers presenting results from the SCUBA Local Universe Galaxy Survey. In our first paper we provided 850-,m flux densities for 104 galaxies selected from the IRAS Bright Galaxy Sample and we found that the 60-, 100-,m (IRAS) and 850-,m (SCUBA) fluxes could be adequately fitted by emission from dust at a single temperature. In this paper we present 450-,m data for the galaxies. With the new data, the spectral energy distributions of the galaxies can no longer be fitted with an isothermal dust model , two temperature components are now required. Using our 450-,m data and fluxes from the literature, we find that the 450/850-,m flux ratio for the galaxies is remarkably constant, and this holds from objects in which the star formation rate is similar to our own Galaxy, to ultraluminous infrared galaxies (ULIRGs) such as Arp 220. The only possible explanation for this is if the dust emissivity index for all of the galaxies is ,2 and the cold dust component has a similar temperature in all galaxies . The 60-,m luminosities of the galaxies were found to depend on both the dust mass and the relative amount of energy in the warm component, with a tendency for the temperature effects to dominate at the highest L60. The dust masses estimated using the new temperatures are higher by a factor of ,2 than those determined previously using a single temperature. This brings the gas-to-dust ratios of the IRAS galaxies into agreement with those of the Milky Way and other spiral galaxies which have been intensively studied in the submm. [source] Six-Degree Field Galaxy Survey completeASTRONOMY & GEOPHYSICS, Issue 3 2009Article first published online: 29 MAY 200 An international research group has announced that the the Six-Degree Field Galaxy Survey, the most detailed map of the nearby universe, is now complete. [source] Optimal integrated Sachs,Wolfe detection and joint likelihood for cosmological parameter estimationMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2008M. Frommert ABSTRACT We analyse the local variance effect in the standard method for detecting the integrated Sachs,Wolfe (ISW) effect via cross-correlating the cosmic microwave background (CMB) with the large-scale structure (LSS). Local variance is defined as the systematic noise in the ISW detection that originates in the realization of the matter distribution in the observed Universe. We show that the local variance contributes about 11 per cent to the total variance in the standard method if a perfect and complete LSS survey up to z, 2 is assumed. Due to local variance, the estimated detection significance and cosmological parameter constraints in the standard method are biased. In this work, we present an optimal method of how to reduce the local variance effect in the ISW detection by working conditional on the LSS data. The variance of the optimal method, and hence the signal-to-noise ratio, depends on the actual realization of the matter distribution in the observed Universe. We show that for an ideal galaxy survey, the average signal-to-noise ratio is enhanced by about 7 per cent in the optimal method, as compared to the standard method. In the framework of our method, it is straightforward to correct for the magnification bias coming from gravitational lensing effects. Furthermore, there is no need to estimate the covariance matrix by Monte Carlo simulations as in the standard method, which saves time and increases the accuracy. Finally, we derive the correct joint likelihood function for cosmological parameters given CMB and LSS data within the linear LSS formation regime, which includes a small coupling of the two data sets due to the ISW effect. [source] Delaunay Tessellation Field Estimator analysis of the PSCz local Universe: density field and cosmic flowMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2007Emilio Romano-Díaz ABSTRACT We apply the Delaunay Tessellation Field Estimator (DTFE) to reconstruct and analyse the matter distribution and cosmic velocity flows in the local Universe on the basis of the PSCz galaxy survey. The prime objective of this study is the production of optimal resolution 3D maps of the volume-weighted velocity and density fields throughout the nearby universe, the basis for a detailed study of the structure and dynamics of the cosmic web at each level probed by underlying galaxy sample. Fully volume-covering 3D maps of the density and (volume-weighted) velocity fields in the cosmic vicinity, out to a distance of 150 h,1 Mpc, are presented. Based on the Voronoi and Delaunay tessellation defined by the spatial galaxy sample, DTFE involves the estimate of density values on the basis of the volume of the related Delaunay tetrahedra and the subsequent use of the Delaunay tessellation as natural multidimensional (linear) interpolation grid for the corresponding density and velocity fields throughout the sample volume. The linearized model of the spatial galaxy distribution and the corresponding peculiar velocities of the PSCz galaxy sample, produced by Branchini et al., forms the input sample for the DTFE study. The DTFE maps reproduce the high-density supercluster regions in optimal detail, both their internal structure as well as their elongated or flattened shape. The corresponding velocity flows trace the bulk and shear flows marking the region extending from the Pisces,Perseus supercluster, via the Local Superclusters, towards the Hydra,Centaurus and the Shapley concentration. The most outstanding and unique feature of the DTFE maps is the sharply defined radial outflow regions in and around underdense voids, marking the dynamical importance of voids in the local Universe. The maximum expansion rate of voids defines a sharp cut-off in the DTFE velocity divergence probability distribution function. We found that on the basis of this cut-off DTFE manages to consistently reproduce the value of ,m, 0.35 underlying the linearized velocity data set. [source] Universal fitting formulae for baryon oscillation surveysMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006Chris Blake ABSTRACT The next generation of galaxy surveys will attempt to measure the baryon oscillations in the clustering power spectrum with high accuracy. These oscillations encode a preferred scale which may be used as a standard ruler to constrain cosmological parameters and dark energy models. In this paper we present simple analytical fitting formulae for the accuracy with which the preferred scale may be determined in the tangential and radial directions by future spectroscopic and photometric galaxy redshift surveys. We express these accuracies as a function of survey parameters such as the central redshift, volume, galaxy number density and (where applicable) photometric redshift error. These fitting formulae should greatly increase the efficiency of optimizing future surveys, which requires analysis of a potentially vast number of survey configurations and cosmological models. The formulae are calibrated using a grid of Monte Carlo simulations, which are analysed by dividing out the overall shape of the power spectrum before fitting a simple decaying sinusoid to the oscillations. The fitting formulae reproduce the simulation results with a fractional scatter of 7 per cent (10 per cent) in the tangential (radial) directions over a wide range of input parameters. We also indicate how sparse-sampling strategies may enhance the effective survey area if the sampling scale is much smaller than the projected baryon oscillation scale. [source] Evolutionary population synthesis for binary stellar population at high spectral resolution: integrated spectral energy distributions and absorption-feature indicesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005Fenghui Zhang ABSTRACT Using evolutionary population synthesis, we present high-resolution (0.3 Å) integrated spectral energy distributions from 3000 to 7000 Å and absorption-line indices defined by the Lick Observatory Image Dissector Scanner (Lick/IDS) system, for an extensive set of instantaneous-burst binary stellar populations with binary interactions. The ages of the populations are in the range 1,15 Gyr and the metallicities are in the range 0.004,0.03. These high-resolution synthesis results can satisfy the needs of modern spectroscopic galaxy surveys, and are available on request. By comparing the synthetic continuum of populations at high and low resolution, we show that there is good agreement for solar metallicity and tolerable disagreement for non-solar metallicity. The strength of the Balmer lines at high spectral resolution is greater than that at low resolution for all metallicities. The comparison of Lick/IDS absorption-line indices at low and high resolution, both of which are obtained by the fitting functions, shows that the discrepancies in all indices except for TiO1 and TiO2 are insignificant for populations with Z= 0.004 and 0.02. The high-resolution Ca4227, Fe5015 and Mgb indices are redder than the corresponding low-resolution ones for populations with Z= 0.01 and 0.03; this effect lowers the derived age and metallicity of the population. The high-resolution Mg1, Fe5709 and Fe5782 indices are bluer than those at low resolution; this effect raises the age and metallicity. The discrepancy in these six indices is greater for populations with Z= 0.03 in comparison to Z= 0.01. At high resolution we compare the Lick/IDS spectral absorption indices obtained by using the fitting functions with those measured directly from the synthetic spectra. We find that the Ca4455, Fe4668, Mgb and Na D indices obtained by the use of the fitting functions are redder for all metallicities, Fe5709 is redder at Z= 0.03 and becomes bluer at Z= 0.01 and 0.004, and the other indices are bluer for all metallicities than the corresponding values measured directly from the synthetic spectra. [source] | ||||||||||