arXiv subjects

G. Paturel

Publications and source records attributed to G. Paturel.

At least 19 recordsLinked to original sources

arXiv2017

LIGO-Virgo events localization as a test of gravitational wave polarization state

The detection of the gravitational wave events GW150914, GW151226, LVT 151012 and GW170104 by the Advanced LIGO antennas has opened a new possibility for the study of fundamental physics of gravitational interaction. We suggest a new method for determining the polarization state of a gravitational wave, which is independent of the nature of a GW source. For this, we calculate the allowed sky positions of GW sources along apparent circles. This is done for each polarization state by considering the sensitivity pattern of each antenna and relative amplitudes of detected signals. The positions of circles are calculated with respect to the line joining both LIGO antennas using the observed arrival time delay of the signal between them. The apparent circles (AC) on the sky for allowed positions of the GW sources for the GW150914, GW151226 and LVT151012 events are parallel to the plane of the disc-like large scale structure known as the Local Super-Cluster (LSC) of galaxies which extends up to radius $\sim 100$ Mpc and having thickness $\sim 30$ Mpc. For the GW170104 event, the AC is perpendicular to the LSC plane but the predicted position of the source may also belong to the LSC plane, which is consistent with detection of possible optical counterpart ATLAS17aeu. The next aLIGO-aVirgo observing runs are proposed to test the possibility of clustering the GW sources along the LSC plane.

gr-qc↗

arXiv2002

Sidereal time analysis as a toll for the study of the space distribution of sources of gravitational waves

Gravitational wave (GW) detectors operating on a long time range can be used for the study of space distribution of sources of GW bursts or to put strong upper limits on the GW signal of a wide class of source candidates. For this purpose we propose here a sidereal time analysis to analyze the output signal of GW detectors. Using the characteristics of some existing detectors, we demonstrate the capability of the sidereal time analysis to give a clear signature of different localizations of GW sources: the Galactic Center, the Galactic Plane, the Supergalactic plane, the Great Attractor. On the contrary, a homogeneous 3D-distribution of GW sources gives a signal without features. In this paper we consider tensor gravitational waves with randomly oriented polarization. We consider GW detectors at fixed positions on the Earth, and a fixed orientation of the antenna.

astro-ph↗

arXiv2002

Calibration of the distance scale from galactic Cepheids:II Use of the HIPPARCOS calibration

New estimate of the distances of 36 nearby galaxies is presented. It is based on the calibration of the V- and I-band Period-Lumi- nosity relations for galactic Cepheids measured by the HIPPARCOS mission. The distance moduli are obtained in a classical way. The statistical bias due to the incompleteness of the sample is corrected according to the precepts introduced by Teerikorpi (1987). We adopt a constant slope (the one obtained with LMC Cepheids). The correction for incompleteness bias introduce an uncertainty which depends on each galaxy. On the mean, this uncertainty is small (0.04 mag) but it may reach 0.3 mag. We show that the un- certainty due to the correction of the extinction is small (propably less than 0.05 mag.). The correlation between the metallicity and the morphological type of the host galaxy sug- gests us to reduce the application to spiral galaxies in order to bypass the problem of metallicity. We suspect that the adopted PL slopes are not valid for all morphological types of galaxies. This may induce a mean systematic shift of 0.1 mag on distance moduli. A comparison with the distance moduli recently published by Freedman et al. (2001) shows there is a reasonably good agreement with our distance moduli.

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arXiv2002

Calibration of the distance scale from galactic Cepheids: I Calibration based on the GFG sample

New estimates of the distances of 36 nearby galaxies are presented based on accurate distances of galactic Cepheids obtained by Gieren, Fouque and Gomez (1998) from the geometrical Barnes-Evans method. The concept of 'sosie' is applied to extend the distance determination to extragalactic Cepheids without assuming the linearity of the PL relation. Doing so, the distance moduli are obtained in a straightforward way. The correction for extinction is made using two photometric bands (V and I) according to the principles introduced by Freedman and Madore (1990). Finally, the statistical bias due to the incompleteness of the sample is corrected according to the precepts introduced by Teerikorpi (1987) without introducing any free parameters (except the distance modulus itself in an iterative scheme). The final distance moduli depend on the adopted extinction ratio {R_V}/{R_I} and on the limiting apparent magnitude of the sample. A comparison with the distance moduli recently published by the Hubble Space Telescope Key Project (HSTKP) team reveals a fair agreement when the same ratio {R_V}/{R_I} is used but shows a small discrepancy at large distance. In order to bypass the uncertainty due to the metallicity effect it is suggested to consider only galaxies having nearly the same metallicity as the calibrating Cepheids (i.e. Solar metallicity). The internal uncertainty of the distances is about 0.1 magnitude but the total uncertainty may reach 0.3 magnitude.

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arXiv2001

Statistics of the detection rates for tensor and scalar gravitational waves from the local galaxy universe

We use data on the local 3-dimensional galaxy distribution for studying the statistics of the detection rates of gravitational waves (GW) coming from supernova explosions. We consider both tensor and scalar gravitational waves which are possible in a wide range of relativistic and quantum gravity theories. We show that statistics of GW events as a function of sidereal time can be used for distinction between scalar and tensor gravitational waves because of the anisotropy of spatial galaxy distribution. For calculation of the expected amplitudes of GW signals we use the values of the released GW energy, frequency and duration of GW pulse which are consistent with existing scenarios of SN core collapse. The amplitudes of the signals produced by Virgo and the Great Attractor clusters of galaxies is expressed as a function of the sidereal time for resonant bar detectors operating now (IGEC) and for forthcoming laser interferometric detectors (VIRGO).Then, we calculate the expected number of GW events as a function of sidereal time produced by all the galaxies within 100 Mpc. In the case of axisymmetric rotational core collapse which radiates a GW energy of $10^{-9}M_{\odot}c^2$, only the closest explosions can be detected. However, in the case of nonaxisymmetric supernova explosion, due to such phenomena as centrifugal hangup, bar and lump formation, the GW radiation could be as strong as that from a coalescing neutron-star binary. For radiated GW energy higher than $10^{-6}M_{\odot}c^2$ and sensitivity of detectors at the level $h \approx 10^{-23}$ it is possible to detect Virgo cluster and Great Attractor, and hence to use the statistics of GW events for testing gravity theories.

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arXiv2001

On the quiescence of the Hubble flow in the vicinity of the Local Group

Cepheid distances of local galaxies (<7 Mpc) are used to study the very nearby velocity field, as pioneered by Sandage (Sandage 1986) who also pointed out its remarkable properties: linearity and quietness. The new data show that the velocity dispersion in the distance range as seen from the barycentre of the Local Group 1-8 Mpc is as low as 38 km/sec. The local rate of expansion coincides with the global Hubble constant. Down to 1.5 Mpc we cannot detect a deviation from the linear Hubble flow. This puts an upper limit for the mass of the Local Group, for a wide class of Friedman models, including those with the cosmological constant.

astro-ph↗

arXiv2000

The DENIS Point Source Catalogue towards the Magellanic Clouds

We have compiled the near infrared Point Source Catalogue (PSC) towards the Magellanic Clouds (MCs) extracted from the data obtained with the Deep Near Infrared Survey of the Southern Sky - DENIS (Epchtein et al. 1997). The catalogue covers an area of of 19.87* 16 square degrees centered on (RA, DEC)=(5h27m20s, -69o00'00'') for the Large Magellanic Cloud (LMC) and 14.7* 10 square degrees centered on (RA, DEC)=(h02m40s, -73o00'00'' for the Small Magellanic Cloud (SMC) at the epoch J2000. It contains about 1300000 sources towards the LMC and 300000 sources towards the SMC each detected in at least 2 of the 3 photometric bands involved in the survey (I, J, Ks). 70% of the detected sources are true members of the Magellanic Clouds, respectively and consist mainly of red giants, asymptotic giant branch stars and super-giants. The observations have all been made with the same instrument and the data have been calibrated and reduced uniformly. The catalogue provides a homogeneous set of photometric data.

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arXiv2000

Investigations of the Local Supercluster Velocity Field III. Tracing the backside infall with distance moduli from the direct Tully-Fisher relation

We have extended the discussion of Paper II (Ekholm et al. 1999) to cover also the backside of the Local Supercluster (LSC) by using 96 galaxies within Theta<30 deg from the adopted centre of LSC and with distance moduli from the direct B-band Tully-Fisher relation. In order to minimize the influence of the Malmquist bias we required log V_max>2.1 and sigma_{B_T}<0.2 mag. We found out that if R_Virgo<20 Mpc this sample fails to follow the expected dynamical pattern from the Tolman-Bondi (TB) model. When we compared our results with the Virgo core galaxies given by Federspiel et al. (1998) we were able to constrain the distance to Virgo: R_Virgo=20-24 Mpc. When analyzing the TB-behaviour of the sample as seen from the origin of the metric as well as that with distances from the extragalactic Cepheid PL-relation we found additional support to the estimate R_Virgo=21 Mpc given in Paper II. Using a two-component mass-model we found a Virgo mass estimate M_Virgo= (1.5-2)M_virial, where M_virial=9.375.10^14M_sun for R_Virgo=21 Mpc. This estimate agrees with the conclusion in Paper I (Teerikorpi et al. 1992). Our results indicate that the density distribution of luminous matter is shallower than that of the total gravitating matter when q_0<=0.5. The preferred exponent in the density power law, alpha\approx2.5, agrees with recent theoretical work on the universal density profile of dark matter clustering in an Einstein-deSitter universe (Tittley & Couchman 1999).

astro-ph↗

arXiv1999

Investigations of the Local Supercluster Velocity Field II. A study using Tolman-Bondi solution and galaxies with accurate distances from the Cepheid PL-relation

A sample of 32 galaxies with accurate distance moduli from the Cepheid PL-relation (Lanoix 1999) has been used to study the dynamical behaviour of the Local (Virgo) supercluster. We used analytical Tolman-Bondi (TB) solutions for a spherically symmetric density excess embedded in the Einstein-deSitter universe (q_0=0.5). Using 12 galaxies within Theta=30 degr from the centre we found a mass estimate of 1.62M_virial for the Virgo cluster. This agrees with the finding of Teerikorpi et al. (1992} that TB-estimate may be larger than virial mass estimate from Tully & Shaya (1984). Our conclusions do not critically depend on our primary choice of the global H_0=57 km/s/Mpc established from SNe Ia (Lanoix 1999). The remaining galaxies outside Virgo region do not disagree with this value. Finally, we also found a TB-solution with the H_0 and q_0 cited yielding exactly one virial mass for the Virgo cluster.

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arXiv1999

Evidence for dark matter in different scales from the KLUN galaxy sample

The KLUN (Kinematics of the Local UNiverse) sample of 6600 spiral galaxies is used in studying dark matter in different scales: Type dependence of the zero-point of Tully-Fisher relation indicates M/L \approx 9 -- 16 in galactic scale. Preliminary results from a study of selection effect influencing double galaxies give a larger value M/L \approx 30 -- 50. Study of the Perseus-Pisces supercluster, using Malmquist bias corrected TF distances and Tolman-Bondi solutions indicates M/L \approx 200 -- 600 for the large clusters. Application of developed version of Sandage-Tammann-Hardy test of the linearity of Hubble law inside the observed hierarchical (fractal) galaxy distribution up to 200 Mpc suggests that either Ω_0 is very small (0.01) or major part of the matter is uniformly distributed dark matter.

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arXiv1999

Extragalactic Cepheid database

We present in this paper an exhaustive compilation of all published data of extragalactic Cepheids. We have checked every light curve in order to characterize the different types of Cepheid and detect potential overtone pulsators, or to estimate the quality of the data. This compilation of about 3000 photometric measurements will constitute a very useful tool for astronomers involved for instance in the extragalactic distance scale.

astro-ph↗

arXiv1999

Kinematics of the Local Universe. X. H_0 from the inverse B-band Tully-Fisher relation using diameter and magnitude limited samples

We derive the value of H_0 using the inverse diameter and magnitude B-band Tully-Fisher relations and the large all-sky sample KLUN (5171 spiral galaxies). Our kinematical model was that of Peebles centered at Virgo. Our calibrator sample consisted of 15 field galaxies with cepheid distance moduli measured mostly with HST. A straightforward application of the inverse relation yielded H_0\approx 80 km/sec/Mpc for the diameter relation and H_0\approx 70 km/sec/Mpc for the magnitude relation. H_0 from diameters is about 50 percent and from magnitudes about 30 percent larger than the corresponding direct estimates (cf. Theureau et al. 1997b). This discrepancy could not be resolved in terms of a selection effect in log V_max nor by the dependence of the zero-point on the Hubble type. We showed that a new, calibrator selection bias (Teerikorpi et al. 1999), is present. By using samples of signicificant size (N=2142 for diameters and N=1713 for magnitudes) we found for a homogeneous distribution of galaxies (alpha=0) H_0\approx 50 km/sec/Mpc for both the diameters and magnitudes. Also H_0's from a fractal distribution of galaxies (decreasing radial number density gradient alpha=0.8) agree with the direct predictions. This is the first time when the inverse Tully-Fisher relation clearly lends credence to small values of the Hubble constant H_0 and to long cosmological distance scale consistently supported by Sandage and his collaborators.

astro-ph↗

arXiv1999

Direct Calibration of the Cepheid Period-Luminosity relation (Based on data from the ESA HIPPARCOS astrometry satellite)

After the first release of HIPPARCOS data, Feast & Catchpole gave a new value to the zero-point of the visual Cepheid Period-Luminosity relation based on trigonometric parallaxes. Because of the large uncertainties on these parallaxes, the way in which individual measurements are weighted bears a crucial importance, and the discrepancy they show leads to the conclusion that the choice of the best weighting system can be provided through a Monte-Carlo simulation. On the basis of such a simulation it is shown that: - A cut in πor in σ_π / πintroduces a strong bias. - The zero-point is more stable when only the brightest Cepheids are used. - The Feast & Catchpole weighting gives the best zero-point and the lowest dispersion. After correction, the adopted visual Period-Luminosity relation is: = -2.77 log P - 1.44 \pm 0.05. Moreover, we extend this study to the photometric I-band (Cousins) and obtain: = -3.05 log P - 1.81 \pm 0.09.

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arXiv1999

First DENIS I-band extragalactic catalog

This paper presents the first I-band photometric catalog of the brightest galaxies extracted from the Deep Near Infrared Survey of the Southern Sky (DENIS) An automatic galaxy recognition program has been developed to build this provisional catalog. The method is based on a discriminating analysis. The most discriminant parameter to separate galaxies from stars is proved to be the peak intensity of an object divided by its array. Its efficiency is better than 99%. The nominal accuracy for galaxy coordinates calculated with the Guide Star Catalog is about 6 arcseconds. The cross-identification with galaxies available in the Lyon-Meudon Extragalactic DAtabase (LEDA) allows a calibraton of the I-band photometry with the sample of Mathewson et Al. Thus, the catalog contains total I-band magnitude, isophotal diameter, axis ratio, position angle and a rough estimate of the morphological type code for 20260 galaxies. The internal completeness of this catalog reaches magnitude $I_{lim}=14.5$, with a photometric accuracy of $\sim 0.18m$. 25% of the Southern sky has been processed in this study. This quick look analysis allows us to start a radio and spectrographic follow-up long before the end of the survey.

astro-ph↗

arXiv1998

Bias in the Cepheid PL relation

We show that the Cepheid PL relation is affected by a Malmquist type bias, the so-called population incompleteness bias. Its calculated slope appears shallower than the true one because of the cutoff in apparent magnitude resulting from the instrumental limiting magnitude. Furthermore, the use of the PL relation, even with the correct slope, leads to underestimation of distances which is not negligible. We confirm this finding by studying simulated PL relations, and we show that this bias may be as large as 0.2 or 0.3 magnitudes on distance modulus. We also test the efficiency of a cutoff in $\log P$ and show that it is a good way to minimize this bias. However, a correction of this is difficult as long as the completeness of the sample is not perfectly well established.

astro-ph↗

arXiv1998

Calibration of the Faber-Jackson relation for M31 globular clusters using Hipparcos data

In this paper we present a data analysis regarding globular clusters as possible extragalactic distance indicators. For this purpose, we collected all velocity dispersion measurements published for galactic and M31 globular clusters. The slope and the zero-point of the Faber-Jackson relation were calibrated using Hipparcos distance measurements, and the relation was applied to extragalactic globular clusters in M31. A distance modulus of 24.12 \pm 0.45 mag was found. This is coherent with what is found by fitting the red giant branches of globular clusters (24.47 \pm 0.07, Holland 98), and is found from the peak of globular clusters luminosity function (24.03 \pm 0.23, Ostriker an d Gnedin 97), but shorter than the 24.7 \pm 0.2 mag (Lanoix et al. 98) and 24.77 \pm 0.11 mag (Feast and Catchpole 97), obtained by using Hipparcos data to calibrate the Cepheid period-luminosity. This calibrated Faber-Jackson relation can now be directly use for other Sc galaxies with resolved globular clusters, as soon as large amounts of spectra will become available, e.g., through the VLT.

astro-ph↗

arXiv1998

Hubble constant from sosie galaxies and HIPPARCOS geometrical calibration

New distances, larger than previous ones, have been obtained for M 31 and M 81 based on the geometrical zero-point of the Cepheid Period-luminosity relation provided by the HIPPARCOS satellite. By combining them with independent determinations we define reasonable ranges for the distances of these important calibrating galaxies. On this basis, we determine the Hubble constant from the method of sosies (look-alike) galaxies, galaxies having the same characteristics than the calibrators. The method is quite secure because it is purely differential and it does not depend on any assumption (apart from the natural one that two sosies galaxies have similar absolute luminosities). Nevertheless, the Malmquist bias has to be taken into account. The observations behave exactly as predicted from the analytical formulation of the bias. Thus, rejecting galaxies which are affected by the Malmquist bias we derive the Hubble constant: H_o = 60 +- 10 (external) km.s^{-1}.Mpc^{-1} If we strictly use the calibration obtained with HIPPARCOS and if the bias found in the Period-Luminosity Relation is considered, the Hubble constant is smaller than this ($\approx 55 km.s^{-1}.Mpc^{-1}$). This gives arguments in favour of the long-distance scale. We briefly discuss possible improvements aiming at still reducing the uncertainty.

astro-ph↗

arXiv1998

Extragalactic database. VII Reduction of astrophysical parameters

The Lyon-Meudon Extragalactic database (LEDA) gives a free access to the main astrophysical parameters for more than 100,000 galaxies. The most common names are compiled allowing users to recover quickly any galaxy. All these measured astrophysical parameters are first reduced to a common system according to well defined reduction formulae leading to mean homogeneized parameters. Further, these parameters are also transformed into corrected parameters from widely accepted models. For instance, raw 21-cm line widths are transformed into mean standard widths after correction for instrumental effect and then into maximum velocity rotation properly corrected for inclination and non-circular velocity. This paper presents the reduction formulae for each parameter: coordinates, morphological type and luminosity class, diameter and axis ratio, apparent magnitude (UBV, IR, HI) and colors, maximum velocity rotation and central velocity dispersion, radial velocity, mean surface brightness, distance modulus and absolute magnitude, and group membership. For each of these parameters intermediate quantities are given: galactic extinction, inclination, K-correction etc.. All these parameters are available from direct connexion to LEDA (telnet lmc.univ-lyon1.fr, login: leda, no passwd OR http://www-obs.univ-lyon1.fr/leda ) and distributed on a standard CD-ROM (PGC-ROM 1996) by the Observatoire de Lyon via the CNRS (mail to petit@obs.univ-lyon1.fr).

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