arXiv subjects

Riccardo Giovanelli

Publications and source records attributed to Riccardo Giovanelli.

At least 145 records · Page 8Linked to original sources

arXiv2000

A Search for OH Megamasers at z > 0.1. I. Preliminary Results

We present the preliminary results of a survey for OH megamasers underway at the Arecibo Observatory. The goals of the survey are to calibrate the luminosity function of OH megamasers to the low-redshift galaxy merger rate (0.1 < z < 0.2), and to use the enhanced sample of OH megamasers provided by the survey to study OH megamaser environments, engines, lifetimes, and structure. The survey should double the known OH megamaser sample to roughly 100 objects. Survey results will be presented in installments to facilitate community access to the data. Here we report the discovery of 11 OH megamasers and one OH absorber, and include upper limits on the isotropic 1667 MHz OH line luminosity of 53 other luminous infrared galaxies at z > 0.1. The new megamasers show a wide range of spectral properties, but are consistent with the extant set of 55 previously reported objects, only 8 of which have z > 0.1.

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arXiv1999

The Convergence Depth of the Local Peculiar Velocity Field

We have obtained Tully-Fisher (TF) measurements for some 3000 late-type galaxies in the field and in 76 clusters distributed throughout the sky between 10 and 200\h Mpc. The cluster data are applied to the construction of an I band TF template, resulting in a relation with a scatter of 0.35 magnitudes and a zero-point accurate to 0.02 magnitudes. Peculiar motions are computed by referral to the template relation, and the distribution of line-of-sight cluster peculiar motions is presented. The dipole of the reflex motion of the Local Group of galaxies with respect to galaxies with measured peculiar velocity converges to the CMB dipole within less than 6000 km/s. The progression of this convergence is well illustrated when the reflex motion is referred to a well-distributed sample of field galaxies, and it is maintained when the reflex motion is referred to the reference frame constituted by the distant clusters in our sample. The field and cluster samples exhibit bulk motion amplitudes of order 200 km/s or smaller. Finally, we apply our sample of cluster peculiar velocities to a test of the putative Hubble bubble recently claimed by Zehavi and coworkers. In contrast to their findings, our data support a relatively quiescent Hubble flow beyond 35\h Mpc.

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arXiv1999

Seeking the Local Convergence Depth. V. Tully-Fisher Peculiar Velocities for 52 Abell Clusters

We have obtained I band Tully-Fisher (TF) measurements for 522 late-type galaxies in the fields of 52 rich Abell clusters distributed throughout the sky between 50 and 200\h Mpc. Here we estimate corrections to the data for various forms of observational bias, most notably Malmquist and cluster population incompleteness bias. The bias-corrected data are applied to the construction of an I band TF template, resulting in a relation with a dispersion of 0.38 magnitudes and a kinematical zero-point accurate to 0.02 magnitudes. This represents the most accurate TF template relation currently available. Individual cluster TF relations are referred to the average template relation to compute cluster peculiar motions. The line-of-sight dispersion in the peculiar motions is 341+/-93 km/s, in general agreement with that found for the cluster sample of Giovanelli and coworkers.

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arXiv1999

Seeking the Local Convergence Depth. IV. Tully-Fisher Observations of 35 Abell Clusters

We present Tully-Fisher observations for 35 rich Abell clusters of galaxies. Results from I band photometry and optical rotation curve work comprise the bulk of this paper. This is the third such data installment of an all-sky survey of 52 clusters in the distance range 50 to 200\h Mpc. The complete data set provides the basis for determining an accurate Tully-Fisher template relation and for estimating the amplitude and direction of the local bulk flow on a 100\h Mpc scale.

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arXiv1999

Large-Scale Power Spectrum and Cosmological Parameters from SFI Peculiar Velocities

We estimate the power spectrum of mass density fluctuations from peculiar velocities of galaxies by applying an improved maximum-likelihood technique to the new all-sky SFI catalog. Parametric models are used for the power spectrum and the errors, and the free parameters are determined by assuming Gaussian velocity fields and errors and maximizing the probability of the data given the model. It has been applied to generalized CDM models with and without COBE normalization. The method has been carefully tested using artificial SFI catalogs. The most likely distance errors are found to be similar to the original error estimates in the SFI data. The general result that is not very sensitive to the prior model used is a relatively high amplitude of the power spectrum. For example, at k=0.1 h/Mpc we find P(k)Ω^{1.2}=(4.4+/-1.7)X10^3 (Mpc/h)^3. An integral over the power spectrum yields σ_8Ω^{0.6}=0.82+/-0.12. Model-dependent constraints on the cosmological parameters are obtained for families of CDM models. For example, for COBE-normalized ΛCDM models (scalar fluctuations only), the maximum-likelihood result can be approximated by Ωn^{2} h_{60}^{1.3} =0.58+/-0.11. The formal random errors quoted correspond to the 90% confidence level. The total uncertainty, including systematic errors associated with nonlinear effects, may be larger by a factor of ~2. These results are in agreement with an application of a similar method to other data (Mark III).

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arXiv1998

Seeking the Local Convergence Depth. The Abell Cluster Dipole Flow to 200 Mpc/h

We have obtained new Tully-Fisher (TF) peculiar velocity measurements for 52 Abell galaxy clusters distributed throughout the sky between ~ 50 and 200 Mpc/h.The measurements are based on I band photometry and optical rotation curves for a sample of 522 spiral galaxies, from which an accurate TF template relation has been constructed. Individual cluster TF relations are referred to the template to compute cluster peculiar motions. The reflex motion of the Local Group of galaxies is measured with respect to the reference frame defined by our cluster sample and the distant portion of the Giovanelli et al. (1998) cluster set. We find the Local Group motion in this frame to be 565+/-113 km/s in the direction (l,b)=(267,26)+/-10 when peculiar velocities are weighted according to their errors. After optimizing the dipole calculation to sample equal volumes equally, the vector is 509+/-195 km/s towards (255,33)+/-22. Both solutions agree, to within 1-sigma or better, with the Local Group motion as inferred from the cosmic microwave background (CMB) dipole. Thus, the cluster sample as a whole moves slowly in the CMB reference frame, its bulk flow being at most 200 km/s.

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arXiv1997

Seeking the Local Convergence Depth. II. TF Observations of the Clusters A114, A119, A194, A2295, A2457, A2806, A3193, A3381, AND A3744

We present Tully-Fisher (TF) observations for nine rich Abell clusters of galaxies. This is the second such data installment of an all-sky survey of 50 clusters in the redshift range 0.02 < z < 0.06. The data extends the TF study of nearby clusters of Giovanelli et al.; they will be used jointly to determine an accurate I band TF template and to establish a cluster inertial reference frame to z = 0.06.

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arXiv1997

Comparison of the SFI Peculiar Velocities with the IRAS 1.2 Jy Gravity Field

We present a comparison between the peculiar velocity fields measured from the SFI all-sky Sbc-Sc Tully-Fisher catalog and that derived from the \iras 1.2 Jy redshift survey galaxy distribution. The analysis is based on the expansion of these data in redshift space using smooth orthonormal functions and is performed using low and high resolution expansions, with an effective smoothing scale which increases almost linearly with redshift. The effective smoothing scales at 3000 \kms are 1500\kms and 1000\kms for the low and high resolution filters. The agreement between the high and low resolution SFI velocity maps is excellent. The general features in the filtered SFI and \iras velocity fields agree remarkably well within 6000\kms. This good agreement between the fields allows us to determine the parameter $β=Ω^{0.6}/b$, where $Ω$ is the cosmological density parameter and $b$ is the linear biasing factor. From a likelihood analysis on the SFI and \iras modes we find that $β=0.6\pm 0.1$ independently of the resolution of the modal expansion. For this value of $β$, the residual fields for the two filters show no systematic variations within 6000 \kms. Most remarkable is the lack of any coherent, redshift dependent dipole flow in the residual field.

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arXiv1997

Redshift-Space Distortions and the Real-Space Clustering of Different Galaxy Types

We study the distortions induced by peculiar velocities on the redshift-space correlation function of galaxies of different morphological types in the Pisces-Perseus redshift survey. Redshift-space distortions affect early- and late-type galaxies in different ways. In particular, at small separations, the dominant effect comes from virialized cluster cores, where ellipticals are the dominant population. The net result is that a meaningful comparison of the clustering strength of different morphological types can be performed only in real space, i.e., after projecting out the redshift distortions on the two-point correlation function xi(r_p,pi). A power-law fit to the projected function w_p(r_p) on scales smaller than 10/h Mpc gives r_o = 8.35_{-0.76}^{+0.75} /h Mpc, γ= 2.05_{-0.08}^{+0.10} for the early-type population, and r_o = 5.55_{-0.45}^{+0.40} /h Mpc, γ= 1.73_{-0.08}^{+0.07} for spirals and irregulars. These values are derived for a sample luminosity brighter than M_{Zw} = -19.5. We detect a 25% increase of r_o with luminosity for all types combined, from M_{Zw} = -19 to -20. In the framework of a simple stable-clustering model for the mean streaming of pairs, we estimate sigma_12(1), the one-dimensional pairwise velocity dispersion between 0 and 1 /h Mpc, to be 865^{+250}_{-165} km/s for early-type galaxies and 345^{+95}_{-65} km/s for late types. This latter value should be a fair estimate of the pairwise dispersion for ``field'' galaxies; it is stable with respect to the presence or absence of clusters in the sample, and is consistent with the values found for non-cluster galaxies and IRAS galaxies at similar separations.

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arXiv1997

Seeking the Local Convergence Depth. I. TF Observations of the Clusters A168, A397, A569, A1139, A1228, and A1983

We present first results of an all-sky observing program designed to improve the quality of the I band Tully-Fisher (TF) template and to obtain the reflex motion of the Local Group with respect to clusters to z = 0.06. We are obtaining between 5 and 15 TF measurements per cluster on a sample of 50 clusters at intermediate redshifts (0.02 < z < 0.06). Presentation of the data for seven Abell clusters of galaxies is given here. This data incorporates methods for estimating the true inclination of a spiral disk, an observational parameter undervalued for small angular-sized galaxies or for galaxies observed in poor seeing conditions.

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arXiv1997

Spectroscopy of Edge-on Spirals

We present HI line observations of 744 edge-on spiral galaxies, extracted from the Flat Galaxy Catalog of Karachentsev et al. (1993). Fluxes, systemic velocities and line widths are given for 587 detected galaxies, as well as search parameters for 157 undetected systems. Widths are corrected for instrumental broadening, smoothing, signal-to--noise and profile shape, and an estimate of the error on the width is given. When corrected for turbulent broadening and inclination angle of the disks, the velocity widths presented here can provide the appropriate line width parameter needed to derive distances via the Tully-Fisher relation.

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arXiv1997

An Economical Technique for the Estimate of Galaxy Distances: the Photometric Fundamental Plane

We show that it is possible to define a purely Photometric Fundamental Plane (PFP) for early-type galaxies. This relation is similar to the standard Fundamental Plane (FP), and is obtained by replacing the velocity dispersion parameter with the difference between the magnitude of a galaxy and that of the mode of the Gaussian luminosity function of E and S0 galaxies. The dispersion in the PFP is comparable to that of the standard FP. However, the use of the mode of the luminosity function to compute the magnitude differences introduces a systematic uncertainty in the derivation of the PFP relation zero-point, so that its accuracy for distance determinations does not scale with the square root of the number of objects used to perform the fit. The method is also vulnerable to any bias that might affect the estimate of the mode of the luminosity function. If however the mode of the luminosity function can be reliably determined, the PFP relation can provide distance estimates with an accuracy comparable to the FP relation, with the advantage that the use of photometric parameters alone reduces drastically the observational requirements of the PFP, in comparison with those of the FP relation. This practical advantage makes the PFP a very economical distance indication method.

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arXiv1996

Deviations from Hubble Flow in the Local Universe

Reviews observational situation in the measurement of peculiar velocities in the local universe. Emphasis is placed on such topics as: Do spirals and ellipticals yield the same peculiar velocity field? What is the cluster velocity distribution function? What is the convergence depth of the local universe, as seen by inspection of motions of clusters and of field galaxies? Are there large-scale bulk flows? A reconstruction of the density field and an estimate of the Hubble constant are also given.

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arXiv1996

A Test of the Lauer--Postman Bulk Flow

We use Tully--Fisher distances for a sample of field late spiral galaxies to test the Lauer and Postman (1994; hereinafter LP) result suggestive of a bulk flow with respect to the Cosmic Microwave Background reference frame, of amplitude of +689 km/s in the direction l=343, b=+52. A total of 432 galaxies are used, subdivided between two cones, of 30deg semiaperture each and pointed respectively toward the apex and antapex of the LP motion. The peculiar velocities in the two data sets are inconsistent with a bulk flow of the amplitude claimed by LP. When combined in opposition, the peculiar velocity medians in shells of constant redshift width are never larger than half the amplitude of the LP bulk flow. Out to 5000 km/s the median bulk velocity in the LP apex--antapex cones is about 200 km/s or less, dropping to a value indistinguishable from zero beyond that distance. It can be excluded that field spiral galaxies within 8000 km/s partake of a bulk flow of the amplitude and direction reported by LP.

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arXiv1996

The I-Band Tully-Fisher Relation and the Hubble Constant

The application of the I band Tully--Fisher relation towards determining the Hubble constant is reviewed, with particular attention to the impact of scatter and bias corrections in the relation. A template relation is derived from galaxies in 24 clusters. A subset of 14 clusters with cz ~ 4000 to 9000 km/s is used as an inertial frame to define the velocity zero point of the relation. Twelve galaxies with Cepheid distances are used to establish the absolute magnitude scale of the Tully--Fisher relation, and thus to determine a value of H_not = 70\pm5 km/s/Mpc. Estimates of the peculiar velocities of the Virgo and Fornax clusters are also given. Assuming that the distance to Fornax is 18.2 Mpc (N1365), H_not = 76\pm8 km/s/Mpc. Assuming that Virgo lies at 17.4 Mpc (M100, N4496, N4639), H_not = 67\pm8 km/s/Mpc.

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arXiv1996

The Relative Distance between the Clusters of Galaxies A2634 and Coma

The Tully-Fisher and Fundamental Plane relations are used to obtain two independent estimates of the relative distance between the clusters A2634 and Coma. Previously published studies of A2634 showed a large discrepancy between the distance estimates obtained with the TF and the Dn-sigma relations, questioning the reliability of redshift-independent distances obtained using these relations. Because of the importance of this issue, we have obtained new distance estimates for A2634, based on much larger samples than previously used, and selected according to rigorous membership criteria. New I band CCD photometry for 175 galaxies, new 21 cm observations of 11 galaxies, and new velocity dispersion measurements for 62 galaxies are used together with previously published data in building these samples. After the appropriate corrections for sample incompleteness have been taken into account, we find the TF and FP distance estimates to be in good agreement, both indicating that A2634 has a negligibly small peculiar velocity with respect to the Cosmic Microwave Background reference frame. Because of the high accuracy with which the two distance estimates have been obtained, their agreement strongly supports the universality of the TF and FP relations, and therefore their reliability for the estimate of redshift-independent distances.

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arXiv1996

The Mass Distribution in the Nearby Universe

We present a new reconstruction of the mass density and the peculiar velocity fields in the nearby universe using recent measurements of Tully-Fisher distances for a sample of late spirals. We find significant differences between our reconstructed fields and those obtained in earlier work: overdensities tend to be more compact while underdense regions, consisting of individual voids, are more abundant. Our results suggest that voids observed in redshift surveys of galaxies represent real voids in the underlying matter distribution. While we detect a bulk velocity of $\sim$ 300 \kms, within a top-hat window 6000 \kms in radius, the flow is less coherent than previously claimed, exhibiting a bifurcation towards the Perseus-Pisces and the Great Attractor complexes. This is the first time that this feature is seen from peculiar velocity measurements. The observed velocity field resembles, more closely than any previous reconstruction, the velocity field predicted from self-consistent reconstructions based on all-sky redshift surveys. This better match is likely to affect estimates of the parameter $β= Ω^{0.6}/b$ and its uncertainty based on velocity-velocity comparisons.

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arXiv1995

The HI Content of Spirals. I. Field-Galaxy HI Mass Functions and HI Mass-Optical Size Regression

A standard parametric maximum-likelihood technique is used to determine both the probability distribution over total HI mass $M_{\rm HI}$ and the regression of this quantity on the linear optical diameter $D_{\rm o}$ for field giant spirals (Sa-Sc) from a complete HI-flux-limited data set of these objects. Gaussian and Schechter parametrizations of the HI mass function are explored. We find that the available data are equally well described by both models, and that the different morphological classes of giant spirals have HI mass functions which, in general, agree well within the errors. The largest discrepancy corresponds to the Sb-type systems which exhibit a deficit of low HI-mass objects relative to the other types. Using a straightforward generalization of the gaussian model, we have also investigated the linear dependence of $M_{\rm HI}$ on $D_{\rm o}$. We confirm that the HI content of spirals is much better predicted by the size of their optical disks than by their morphological types alone. The inferred correlations imply a considerable decrease of the ratio $M_{\rm HI}/D_{\rm o}^2$ with increasing galaxy size for types earlier than Sc.

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