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R. Giovanelli

Publications and source records attributed to R. Giovanelli.

51 records · Page 3Linked to original sources
arXiv1999

Near-infrared observations of galaxies in Pisces-Perseus: III. Global scaling relations of disks and bulges

We determine the parameters of scaling relations analogous to the Fundamental Plane of elliptical galaxies for the bulges and disks of a sample of 40 spiral galaxies. To this end we derive structural parameters (scalelengths and surface brightnesses) from near infrared H band images, and kinematical parameters (rotational velocities) from optical rotation curves. In the case of the disks, we test the accuracy of the derived relation as a distance indicator by comparing its scatter to that of the H band Tully-Fisher relation for the same sample, and find that the accuracy attained by the latter is slightly higher (the dispersion is 19% versus 23% for this sample). It is speculated that the difference is due to the more robust character of global parameters, rather than those associated with the inner parts of disks. It also apperas that (a) either the stellar mass-to-light ratios of bulge and disk increase with the size of the components, or (b) the bulge and disk relative contributions to the overall rotation of the galaxy (and, as a consequence, to its total mass) become steadily smaller with increasing size.

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arXiv1998

The Universality of the Fundamental Plane of E and S0 Galaxies. Sample Definition and I Band Photometric Data

As part of a project to compare the Fundamental Plane and Tully-Fisher distance-scales, we present here I band CCD photometry for 636 early-type galaxies in 8 clusters and groups of galaxies. These are the A262, A1367, Coma (A1656), A2634, Cancer and Pegasus clusters, and the NGC 383 and NGC 507 groups. Sample selection, cluster properties, and cluster membership assignment criteria are discussed. We present photometric parameters that are used in the Fundamental Plane relation, the effective radius r_e and the effective surface brightness mu_e, as derived from a r^{1/4} fit to the observed radial photometric profile of each galaxy. A comparison with similar data found in the literature for the Coma cluster shows that large systematic uncertainties can be introduced in the measurement of r_e and mu_e by the particular method used to derive those parameters. However the particular combination of these two parameters that enters in the Fundamental Plane relation is a quantity that can be measured with high accuracy.

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arXiv1998

The Universality of the Fundamental Plane of E and S0 Galaxies. Spectroscopic data

We present here central velocity dispersion measurements for 325 early-type galaxies in eight clusters and groups of galaxies, including new observations for 212 galaxies. The clusters and groups are the A262, A1367, Coma (A1656), A2634, Cancer and Pegasus clusters, and the NGC 383 and NGC 507 groups. The new measurements were derived from medium dispersion spectra, that cover 600 A centered on the Mg Ib triplet at lambda ~ 5175. Velocity dispersions were measured using the Tonry & Davis cross-correlation method, with a typical accuracy of 6%. A detailed comparison with other data sources is made.

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arXiv1998

Spiral Galaxies and the Peculiar Velocity Field

Monopole and dipole signatures of the peculiar velocity field as derived from the SFI sample of field spirals and the SCI and SC2 samples of cluster spirals are presented. The monopole exhibits no evidence of a `Hubble bubble' within 7000 km/s as suggested by Zehavi et al. (1998); the dipole of the reflex motion of the Local Group converges to the CMB dipole within less than 6000 km/s, and remains consistent with it, when referred to the reference frame constituted by the SC2 cluster sample, which extends to 20,000 km/s.

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arXiv1998

The Motions of Clusters of Galaxies and the Dipoles of the Peculiar Velocity Field

In preceding papers of this series, TF relations for galaxies in 24 clusters with radial velocities between 1000 and 9200 km/s (SCI sample) were obtained, a Tully-Fisher (TF) template relation was constructed and mean offsets of each cluster with respect to the template obtained. Here, an estimate of the line-of-sight peculiar velocities of the clusters and their associated errors are given. It is found that cluster peculiar velocities in the Cosmic Microwave Background reference frame do not exceed 600 k/ms and that their distribution has a line-of-sight dispersion of 300 k/ms, suggesting a more quiescent cluster peculiar velocity field than previously reported. When measured in a reference frame in which the Local Group is at rest, the set of clusters at cz > 3000 km/s exhibits a dipole moment in agreement with that of the CMB, both in amplitude and apex direction. It is estimated that the bulk flow of a sphere of 6000 km/s radius in the CMB reference frame is between 140 and 320 km/s. These results are in agreement with those obtained from an independent sample of field galaxies (Giovanelli et al. 1998; see astro-ph/9807274)

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arXiv1998

Near-infrared observations of galaxies in Pisces-Perseus: II. Extinction effects and disk opacity

We study the correlations with inclination of H-band disk and bulge structural parameters and I-H colour profiles for a sample of 154 spiral galaxies, in order to detect possible effects due to internal extinction by dust. The selection of the sample assures that galaxies at different inclinations are not intrinsically different, so that the observed correlations represent the real behaviour of the parameter considered. All the parameters are derived from a bi-dimensional fitting of the galaxy image. We find that extinction, though small at near infrared wavelengths, is sufficient to produce observable effects. In particular the observed increase of the average disk scalelength and the reddening of the disk I-H colour at high inclinations are clear signatures of the presence of dust. The total H-band disk luminosity depends little on inclination; on the other hand significant corrections to the face-on aspect are derived for the H-band central disk brightness and the disk scalelength. The bulge parameters exhibit little or no dependence on inclination. Simulations carried out with a simple model for an internally-extincted galaxy show that these results imply a central H-band optical depth between 0.3 and 0.5.

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arXiv1998

Peculiar Velocity Dipoles of Field Galaxies

The Tully-Fisher (Tully and Fisher 1977; TF) relation is applied to obtain peculiar velocities of field spirals galaxies and to calculate dipoles of the peculiar velocity field to cz ~ 8000 km/s. The field galaxy sample is spatially co-extensive with and completely independent on a cluster sample, for which dipole characteristics are given in a separate paper. Dipoles of the peculiar velocity field are obtained separately by applying (i) an inverse version of the TF relation and selecting galaxies by redshift windowing and (ii) a direct TF relation, with velocities corrected for the inhomogeneous Malmquist bias, and windowing galaxies by TF distance. The two determinations agree, as they do with the cluster sample. When measured in a reference frame in which the Local Group is at rest, the dipole moment of field galaxies farther than ~4000 km/s is in substantial agreement, both in amplitude and direction, with that exhibited by the Cosmic Microwave Background radiation field.

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arXiv1997

Peculiar Velocities of Clusters in CDM Models

Recently, peculiar velocity measurements became available for a new sample of galaxy clusters. From an accurately calibrated Tully-Fisher relation for spiral galaxies, we compute the rms cluster peculiar velocity and compare it to the linear theory predictions of COBE-normalized low-density and open CDM models (LambdaCDM and OCDM, respectively). Confidence levels for model rejection are estimated using a Monte Carlo procedure to generate for each model a large ensemble of artificial data sets. Following Zaroubi et al. (1997), we express our results in terms of constraints on the (Omega_0,n_pr,h) parameter space. Such constraints turn into sigma_8 Omega_0^{0.6}=0.50^{+0.25}_{-0.14} at the 90% c.l., thus in agreement with results from cluster abundance. We show that our constraints are also consistent with those implied by the shape of the galaxy power spectrum within a rather wide range for the values of the model parameters. Finally, we point out that our findings disagree at about the 3sigma level with respect to those by Zaroubi et al. (1997), based on the Mark III catalogue, which tend to prefer larger Omega_0 values within the CDM class of models.

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arXiv1996

The Tully-Fisher Relation and H_not

The use of the Tully-Fisher (TF) relation for the determination of the Hubble Constant relies on the availability of an adequate template TF relation and of reliable primary distances. Here we use a TF template relation with the best available kinematical zero-point, obtained from a sample of 24 clusters of galaxies extending to cz ~ 9,000 km/s, and the most recent set of Cepheid distances for galaxies fit for TF use. The combination of these two ingredients yields H_not = 69+/-5 km/(s Mpc). The approach is significantly more accurate than the more common application with single cluster (e.g. Virgo, Coma) samples.

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arXiv1996

The I-Band Tully-Fisher Relation for Cluster Galaxies: Data Presentation

Observational parameters which can be used for redshift-independent distance determination using the Tully-Fisher (TF) technique are given for 782 spiral galaxies in the fields of 24 clusters or groups. I band photometry for the full sample was either obtained by us or compiled from published literature. Rotational velocities are derived either from 21 cm spectra or optical emission line long--slit spectra, and converted to a homogeneous scale. In addition to presenting the data, a discussion of the various sources of error on TF parameters is introduced, and the criteria for the assignment of membership to each cluster are given. The construction of a TF template, bias corrections and cluster motions are discussed in an accompanying paper.

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arXiv1996

The I-Band Tully-Fisher Relation for Cluster Galaxies: a Template Relation, its Scatter and Bias Corrections

Infrared I band photometry and velocity widths for galaxies in 24 clusters, with radial velocities between 1,000 and 10,000 \kms, are used to construct a template Tully--Fisher (TF) relation. The sources of scatter in the TF diagram are analyzed in detail; it is shown that the common practice of referring to a single figure of TF scatter is incorrect and can lead to erroneous bias corrections. Biases resulting from sample incompleteness, catalog inaccuracies, cluster size and other sources, as well as dependences of TF parameters on morphological type and local environment, are discussed and appropriate corrections are obtained. A template TF relation is constructed by combining the data from the 24 clusters, and kinematic cluster offsets from a putative reference frame which well approximates null velocity with respect to the cosmic microwave background, are obtained.

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arXiv1995

What is the Small-Scale Velocity Dispersion of Galaxy Pairs?

We present some new results from an ongoing investigation of the anisotropy of the two--point correlation function for optically selected galaxies. We have estimated xi(r_p,pi) from the Perseus-Pisces redshift survey, which is now virtually 100\% complete for all morphological types to m_B = 15.5. We detect strong distortions of the iso-correlation contours in xi(r_p,pi). These correspond to a global (`cluster' plus `field') pairwise velocity dispersion at 1 h^{-1} Mpc, sigma(1), which is about a factor of two higher than the canonical value \sim 350 km s^{-1} obtained from the CfA1 survey and recently from the 1.2 Jy IRAS redshift survey. However, the variance of this value is still rather strong even within the relatively large volumes surveyed (typically 90$^\circ$ $\times$ 45$^\circ$ $\times$ 100 h^{-1} Mpc). From the largest volume explorable (126 h^{-1} Mpc depth), the best bet for the `cosmic' value of sigma(1) seems to be between 600 and 700 km s^{-1}. However, for a hopefully robust determination of its value we will have to wait for the analyses of the next generation of larger {\tenbf optical} redshift surveys (such as, e.g., the now completed ESP or the forthcoming Sloan Digital Sky Survey).

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arXiv1994

Sizes of Voids as a test for Dark Matter Models

We use the void probability statistics to study the redshift-space galaxy distribution as described by a volume-limited subsample of the Perseus-Pisces survey. We compare the results with the same analysis realized on artificial samples, extracted from high-resolution N-body simulations by reproducing the observational biases of the real data set. Simulations are run for the Cold+HotDM model (CHDM) and for unbiased and biased (b=1.5) CDM models in a 50 Mpc/h box. We identify galaxies as residing in peaks of the evolved density field. We fragment overmerged structures into individual galaxies so as to reproduce both the correct luminosity function (after assuming M/ L values for the resulting galaxy groups) and the two-point correlation function. Our main result is that a void-probability function (VPF) from the standard CHDM model with fractions 60% cold, 30% hot, 10% barions, exceeds the observational VPF with a high confidence level. CDM models produce smaller VPF independent of the biasing parameter. We verify the robustness of this result against changing the observer position in the simulations and the galaxy identification in the evolved density field.

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arXiv1994

Deviations from Hierarchical Clustering in Real and Redshift Space

We discuss the effects of redshift--space distortions on the estimate of high order galaxy correlation functions. We use both the Perseus--Pisces redshift survey and the results of high--resolution N--body simulations to explore the consequences of working in redshift space on the detection of deviations from hierarchical clustering. Both for real and simulated data, significant deviations from hierarchical clustering seem to be present in real space. Their behaviour is coherent with that expected from an initially biased galaxy field, once the displacement from the sites where galaxies formed, due to the nonlinear gravitational evolution, is taken into account. The passage to redshift space has the net effect of filtering out the higher powers required to fit the distribution in real space. This magnifies the distortions operated by nonlinear evolution on the initial distribution, erasing the residual narrow scale range (2--5~$h^{-1}$Mpc) where deviations from hierarchical clustering are still detectable in real space. We conclude that such deviations can hardly be estimated using data in redshift space.

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