DSpace Angular :: Browsing by Author "Quintana, H"

Browsing by Author "Quintana, H"

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5@5 -: a 5 GeV energy threshold array of imaging atmospheric Cherenkov telescopes at 5 km altitude
(2001) Aharonian, FA; Konopelko, AK; Völk, HJ; Quintana, H
We discuss the concept and the performance of a powerful future ground-based astronomical instrument, 5@5 - a 5 GeV energy threshold stereoscopic array of several large imaging atmospheric Cherenkov telescopes (IACTs) installed at a very high mountain elevation of about 5 km a.s.l. - for the study of the gamma -ray sky at energies from approximately 5 to 100 GeV, where the capabilities of both the current space-based and ground-based gamma -ray projects are quite limited. With its potential to detect the "standard" EGRET gamma -ray sources with spectra extending beyond several GeV in exposure times from 1 to 10(3) s, such a detector may serve as an ideal "gamma-ray timing explorer" for the study of transient non-thermal phenomena like gamma -radiation from AGN jets, synchrotron flares of microquasars, the high energy (GeV) counterparts of gamma ray bursts, etc. 5@5 also would allow detailed gamma -ray spectroscopy of persistent nonthermal sources like pulsars, supernova remnants, plerions, radiogalaxies, and others, with unprecedented for gamma -ray astronomy photon statistics. The existing technological achievements in the design and construction of multi(1000)-pixel, high resolution imagers, as well as of large, 20 m diameter class multi-mirror dishes with rather modest optical requirements, would allow the construction of such a detector in the foreseeable future, although in the longer terms from the point of view of ongoing projects of 100 GeV threshold IACT arrays like HESS which is in the build-up phase. An ideal site for such an instrument could be a high-altitude, 5 km a.s.l. or more, flat area with a linear scale of about 100 m in a very arid mountain region in the Atacama desert of Northern Chile. (C) 2001 Elsevier Science B.V. All rights reserved.
A catalog of 203 galaxy clusters serendipitously detected in the ROSAT PSPC pointed observations
(1998) Vikhlinin, A; McNamara, BR; Forman, W; Jones, C; Quintana, H; Hornstrup, A
We present a catalog of 203 clusters of galaxies serendipitously detected in 647 ROSAT PSPC high Galactic latitude pointings covering 158 deg(2). This is one of the largest X-ray-selected cluster samples, comparable in size only to the ROSAT All-Sky Survey sample of nearby clusters (Ebeling et al. 1997). We detect clusters in the inner 17.'5 of the ROSAT PSPC field of view using the spatial extent of their X-ray emission. Fluxes of detected clusters range from 1.6 x 10(-14) to 8 x 10(-12) ergs s(-1) cm(-2) in the 0.5-2 keV energy band. X-ray luminosities range from 10(42) ergs s(-1), corresponding to very poor groups, to similar to 5 x 10(44) ergs s(-1), corresponding to rich clusters. The cluster redshifts range from z = 0.015 to z > 0.5. The catalog lists X-ray fluxes, core radii, and spectroscopic redshifts for 73 clusters and photometric redshifts for the remainder. Our detection method, optimized for finding extended sources in the presence of source confusion, is described in detail. Selection effects necessary for a statistical analysis of the cluster sample are comprehensively studied by Monte Carlo simulations. We have optically confirmed 203 of 223 X-ray sources as clusters of galaxies. Of the remaining 20 sources, 19 are likely false detections arising from blends of unresolved point X-ray sources. Optical identifications of the remaining object are hampered by a bright nearby star. Above a flux of 2 x 10(-13) ergs s(-1) cm(-2), 98% of extended X-ray sources are optically confirmed clusters. The number of false detections and their flux distribution are in perfect agreement with simulations. The log N-log S relation for clusters derived from our catalog shows excellent agreement with counts of bright clusters derived from the Einstein Extended Medium Sensitivity Survey and ROSAT All-Sky Survey. At fainter fluxes, our log N-log S relation agrees with the smaller area WARPS survey. Our cluster counts appear to be systematically higher than those from a 50 deg(2) survey by Rosati et al. In particular, at a flux of 2 x 10(-13) ergs s(-1) cm(-2), we find a surface density of clusters of 0.57 +/- 0.07 deg(-2), which is a factor of 1.3 more than was found-by Rosati et al. This difference is marginally significant at the similar to 2 sigma level. The large area of our survey makes it possible to study the evolution of the X-ray luminosity function in the high luminosity range inaccessible with other, smaller area ROSAT surveys.
Batch discovery of nine z ∼ 1 clusters using X-ray and K or R, z′ images
(2005) Andreon, S; Valtchanov, I; Jones, LR; Altieri, B; Bremer, M; Willis, J; Pierre, M; Quintana, H
We present the results of an initial search for clusters of galaxies at z similar to 1 and above, using data from 2.9 square degrees of XMM-Newton images. By selecting weak potentially extended X-ray sources with faint or no identifications in deep, ground-based optical imaging, we have constructed a starting sample of 19 high-redshift cluster candidates. Near-IR and R, z' imaging of these fields identified nine of them as high-redshift systems. Six of these were confirmed spectroscopically, three at z similar to 1.0 and the other three in the 0.8 < Z < 0.92 range. The remaining three systems have solid photometric evidence to be at Z(phot) similar to 0-8, 1.0 and 1.3. The present sample significantly increases the number of such clusters. The measured density of z I clusters, after discarding 'low'-redshift systems at z less than or similar to 0.92 is about 1.7 deg(-2) (with 68 per cent confidence interval equal to [1.0, 2.9]) for f(x) greater than or similar to 2.5 10(-15) erg cm(-2) s(-1) ([0.5-2] keV) and this is a lower limit, having, screened not all potential z similar to 1 candidate clusters. Coordinates, X-ray measures and evidence for nine X-ray-selected high-redshift clusters is given.
CCD sequences in the Shapley supercluster of galaxies .1. The LCO-Toronto telescope data
(1996) Infante, L; Slezak, E; Quintana, H
We present R CCD photometric sequences of stars for calibrating ESO/SERC (R) survey plates in the region of the Shapley supercluster of galaxies.
CCD sequences in the shapley supercluster of galaxies .2. The ESO data
(1996) Slezak, E; Infante, L; Quintana, H
We present V and R CCD photometric sequences of stars and galaxies for calibrating ESO/SERC (R) survey plates in the region of the Shapley supercluster of galaxies.
Cosmological constraints from the evolution of the cluster baryon mass function at z ∼ 0.5
(2003) Vikhlinin, A; Voevodkin, A; Mullis, CR; VanSpeybroeck, L; Quintana, H; McNamara, BR; Gioia, I; Hornstrup, A; Henry, JP; Forman, WR; Jones, C
We present a new method for deriving cosmological constraints based on the evolution of the baryon mass function of galaxy clusters and implement it using 17 distant clusters from our 160 deg(2) ROSAT survey. The method uses the cluster baryon mass as a proxy for the total mass, thereby avoiding the large uncertainties of the M-tot-T or M-tot-L-X relations used in all previous studies. Instead, we rely on a well-founded assumption that the M-b/M-tot ratio is a universal quantity, which should result in a much smaller systematic uncertainty. Taking advantage of direct and accurate Chandra measurements of the gas masses for distant clusters, we find strong evolution of the baryon mass function between z > 0.4 and the present. The observed evolution defines a narrow band in the Omega(m)-Lambda plane, Omega(m) + 0.23Lambda = 0.41 +/- 0.10 at 68% confidence, which intersects with constraints from the cosmic microwave background and Type Ia supernovae near Omega(m) = 0.3 and Lambda = 0.7.
Deconstruction Abell 3266: A major merger in a quiet cluster
(2000) Flores, RA; Quintana, H; Way, MJ
We present results of simple N-body simulations that strengthen the suggestion that Abell 3266 is composed of two subunits of comparable mass that have merged recently. Both the real cluster and the N-body dark-matter cluster show mixed signals of substructure under statistical tests. However, in a decidedly nonstatistical approach allowed by the wide-area coverage and the large number of redshifts Quintana, Ramirez, & Way measured in A3266, they sliced the real cluster in redshift space to uncover a peculiar spatial distribution of galaxies that they suggested was the result of a recent merger. In our simulations, a similar distribution is the result of an ongoing merger between two comparable-mass units that started about 2 x 10(9) yr ago in the N-body simulations. We also find that the distribution of emission-line galaxies in A3266 traces the same structure. We discuss further tests of our merger hypothesis and speculate on the possibility that a similar process might be occurring in other, apparently relaxed clusters at the present epoch.
Dynamics of the cluster of galaxies A3266 (Sersic 40/6) .1. Spectroscopic data
(1996) Quintana, H; Ramirez, A; Way, MJ
We present 387 velocities covering an area 1.8 degrees x1.8 degrees, including 229 new galaxy velocities obtained from 309 spectra, of which 317 appear to be cluster members according to our analysis. Based on this extended velocity sample we reanalyzed the velocity structure of the cluster. We found a strongly decreasing velocity dispersion profile that, as well as the mean velocity, shows significant radial scatter. Inside the 2.5h(50)(-1) Mpc radius, the velocity dispersion has a value of 1306+/-73 km s(-1), while further out than 3h(50)(-1) Mpc it falls below 800 km s(-1). The global dispersion is 1085+/-51 km s(-1). We found a remarkable velocity substructure, which we interpret as a tidal outgoing arm reaching from the center to the northernmost extensions surveyed. The arm could be produced by a recent merger with another cluster, that moved from the front and SW direction and scattered from the main cluster core into the arm. This model allows us to derive an epoch for the collision between the more massive core and the front edge of the incoming cluster of 4X10(9)h(50)(-1) yr ago and of similar to 2X10(9)h(50)(-1) yr for the merging of both cores. Formation of the dumb-bell is a later merger process of the two BCMs, consistent with theoretical estimates. The collision picture is also consistent with the distorted x-ray image. The very northernmost parts of the arm could, alternatively, be interpreted as ongoing infall of a few outlying loose groups. The suggestion of a faint galaxy system within 400h(50)(-1) kpc, satellite to the central dumb-bell, is maintained in spite of the large central velocity dispersion value; however, confirmation requires data for further compact faint members. From several mass estimators we derived a cluster dynamical mass value of 5X10(15)h(50)(-1) M(.), but this value should be seen in the merger context described. (C) 1996 American Astronomical Society.
Evolution of cluster X-ray luminosities and radii: Results from the 160 square degree rosat survey
(1998) Vikhlinin, A; McNamara, BR; Forman, W; Jones, C; Quintana, H; Hornstrup, A
We searched for cluster X-ray luminosity and radius evolution using our sample of 203 galaxy clusters detected in the 160 deg(2) survey with the ROSAT PSPC (Vikhlinin et al.). With such a large area survey, it is possible, for the first time with ROSAT, to test the evolution of luminous clusters, L-X > 3 x 10(44) ergs s(-1) in the 0.5-2 keV band. We detect a factor of 3-4 deficit of such luminous clusters at z > 0.3 compared with the present. The evolution is much weaker or absent at modestly lower luminosities, (1-3) x 10(44) ergs s(-1). At still lower luminosities, we find no evolution from the analysis of the log N-log S relation. The results in the two upper L, bins are in agreement with the Einstein Extended Medium-Sensitivity Survey evolution result (Gioia et al.; Henry ct al.), which was obtained using a completely independent cluster sample. The low-L-X results are in agreement with other ROSAT surveys (e.g., Rosati et al.; Jones et al.). We also compare the distribution of core radii of nearby and distant (z > 0.4) luminous (with equivalent temperatures of 4-7 keV) clusters and detect no evolution. The ratio of average core radius for z similar to 0.5 and z < 0.1 clusters is 0.9 +/- 0.1, and the core radius distributions are remarkably similar. A decrease of cluster sizes incompatible with our data is predicted by self-similar evolution models for a high-Omega universe.
Galaxy evolution in clusters up to z=1.0
(2004) Andreon, S; Willis, J; Quintana, H; Valtchanov, I; Pierre, M; Pacaud, F
We present a combined study of the colour-magnitude relation, colour distribution and luminosity function (LF) of a sample of 24 clusters at redshifts 0.3 < z < 1. The sample is largely composed of X-ray selected/detected clusters. Most of the clusters at redshifts z < 0.6 display X-ray luminosity or richness typical of poor clusters or groups, rather than the more typical, massive clusters studied in literature at redshifts z ≳ 0.3. All our clusters, including groups, display a colour-magnitude relation consistent with a passively evolving stellar population formed at a redshift z(f) ≳ 2, in accordance with observed galaxy populations in more massive clusters studied at comparable redshifts. Colours and luminosity functions (LFs) show that the cluster galaxy population is consistent with the presence of at least two components: old systems formed at high redshift that have evolved passively from that epoch, together with a galaxy population displaying more recent star fortnation. The former population forms at 2 ≲ z(f) ≲ 5, the latter at redshifts z < 1. A model in which stars do not evolve is clearly rejected both by the colour of reddest galaxies and by the characteristic luminosity m* measures. All clusters (with one possible exception) are detected independently by an almost three-dimensional optical search employing sky position and colour - this despite the primary X-ray selection and low X-ray flux/optical richness displayed by most of the sample.
Photometry of the central regions in a complete sample of high Bautz-Morgan-type Abell clusters.: I.: Observations and data calibration
(2000) Quintana, H; Infante, L; Fouque, P; Carrasco, ER; Cuevas, H; Hertling, G; Nuñez, I
We present CCD photometry of 209 southern Abell clusters selected according to Bautz-Morgan type I, I-II, and II. We have performed total photometry in the GUM r bandpass, classified stars and galaxies, and obtained structural parameters for the images. To estimate the photometric and structural errors on the CCD images and the completeness limits of our photometry, we performed realistic simulations of stars and galaxies and ran our classification algorithms. Here, we present central galaxy counts and metric photometry of the brightest cluster,:members, for which we give accurate positions, and compare this photometry with values in the literature. A linear magnitude-redshift relation has been derived from the tenth-ranked galaxy in each cluster. Photometric redshifts have been estimated for 57 clusters. We provide either spectroscopic or photometric redshifts for all the clusters in our sample. Further analysis of these data will be presented in further publications.
Spectroscopy of the NGC 4782/3 dumbbell dominated group of galaxies: Dark haloes and merger of subgroups
(1996) Quintana, H; Ramirez, A; Way, MJ
A nearly complete sample of new velocities for 96 galaxies covering an area 1 degrees X1.25 degrees centered on NGC 4782/3 are presented, Including data from the literature a total of 125 velocities are compiled. We deduce that 40 galaxies are likely members of the group centered on NGC 4782/3, more than doubling the original confirmed 13 members. Based on this extended velocity sample we analyze the velocity structure of this unusual group. A bi-modal velocity structure centered on each of the dumbbell components provides evidence for an ongoing collision of two subgroups associated to these components. In velocity space the richer subgroup is centered on the more massive NGC 4782. From the subgroup dynamics we derive approximate dynamical masses of 5X10(13) M. and 1X10(13) M. for the NGC 4782 and NGC 4783 subgroups, respectively, This leads to a group M/L approximate to 300 (M/L)., implying that similar to 90% of the group mass is in dark form, within subsystems associated to each subgroup, The colliding elliptical galaxies have massive haloes which should be important in shaping the outcome of the collision and merger process, In particular, haloes could change the interpretation of the tidal distortions and play a role in the shaping of the radio double bent jet structure of 3C 278. (C) 1996 American Astronomical Society.
Structure and dynamics of the Shapley Supercluster -: Velocity catalogue, general morphology and mass
(2006) Proust, D; Quintana, H; Carrasco, ER; Reisenegger, A; Slezak, E; Muriel, H; Dünner, R; Sodre, L; Drinkwater, MJ; Parker, QA; Ragone, CJ
We present results of our wide-field redshift survey of galaxies in a 285 square degree region of the Shapley Supercluster (SSC), based on a set of 10 529 velocity measurements (including 1201 new ones) on 8632 galaxies obtained from various telescopes and from the literature. Our data reveal that the main plane of the SSC (v approximate to 14 500 km s(-1)) extends further than previous estimates, filling the whole extent of our survey region of 12 degrees by 30 degrees on the sky (30 x 75 h(-1) Mpc). There is also a connecting structure associated with the slightly nearer Abell 3571 cluster complex (v approximate to 12 000 km s(-1)). These galaxies seem to link two previously identified sheets of galaxies and establish a connection with a third one at v = 15 000 km s(-1) near RA = 13(h). They also tend to fill the gap of galaxies between the foreground Hydra-Centaurus region and the more distant SSC. In the velocity range of the Shapley Supercluster (9000 km s(-1) < cz < 18 000 km s(-1)), we found redshift-space overdensities with b(j) < 17.5 of similar or equal to 5.4 over the 225 square degree central region and similar or equal to 3.8 in a 192 square degree region excluding rich clusters. Over the large region of our survey, we find that the intercluster galaxies make up 48 per cent of the observed galaxies in the SSC region and, accounting for the different completeness, may contribute nearly twice as much mass as the cluster galaxies. In this paper, we discuss the completeness of the velocity catalogue, the morphology of the supercluster, the global overdensity, and some properties of the individual galaxy clusters in the Supercluster.
The 160 Square Degree ROSAT Survey
(2003) Mullis, CR; McNamara, BR; Quintana, H; Vikhlinin, A; Henry, JP; Gioia, IM; Hornstrup, A; Forman, W; Jones, C
We present the revised catalog of galaxy clusters detected as extended X-ray sources in the 160 Square Degree ROSAT Survey, including spectroscopic redshifts and X-ray luminosities for 200 of the 201 members. The median redshift is z(median) = 0.25, and the median X-ray luminosity is L-X,L-median = 4.2 x 10(43) h(50)(-2) s(-1) (0.5 - 2.0 keV). This is the largest high-redshift sample of X-ray - selected clusters published to date. There are 73 objects at z > 0.3 and 22 objects at z > 0.5 drawn from a statistically complete flux-limited survey with a median object flux of 1.4 x 10(-13) ergs cm(-2) s(-1). We describe the optical follow-up of these clusters with an emphasis on our spectroscopy, which has yielded 155 cluster redshifts, 110 of which are presented here for the first time. These measurements, combined with 45 from the literature and other sources, provide near-complete spectroscopic coverage for our survey. We discuss the final optical identifications for the extended X-ray sources in the survey region and compare our results to similar X-ray cluster searches.
The Butcher-Oemler effect at z∼0.35
(2006) Andreon, S; Quintana, H; Tajer, M; Galaz, G; Surdej, J
In this paper we focus on the much debated Butcher-Oemler effect: the increase with redshift of the fraction of blue galaxies in clusters. Considering a representative cluster sample made of seven groups/clusters at z similar to 0.35, we have measured the blue fraction from the cluster core to the cluster outskirts and the field mainly using wide-field Cerro Tololo Inter-American Observatory images. This sample represents a random selection of a volume complete X-ray selected cluster sample, selected so that there is no physical connection with the studied quantity (blue fraction), to minimize observational biases. In order to statistically assess the significance of the Butcher-Oemler effect, we introduce the tools of Bayesian inference. Furthermore, we have modified the blue fraction definition in order to take into account the reduced age of the Universe at higher redshifts, because we should no longer attempt to reject an unphysical universe in which the age of the Universe does depend on redshift, whereas the age of its content does not. We have measured the blue fraction from the cluster centre to the field and we find that the cluster affects the properties of the galaxies up to two virial radii at z similar to 0.35. Data suggest that during the last 3 Gyr no evolution of the blue fraction, from the cluster core to the field value, is seen beyond that needed to account for the varying age with the redshift of the Universe and of its content. The agreement of the radial profiles of the blue fraction at z= 0 and z similar to 0.35 implies that the pattern infall did not change over the last 3 Gyr, or, at least, its variation has no observational effect on the studied quantity.
The central region of the Fornax cluster I. A catalog and photometric properties of galaxies in selected CCD fields
(1999) Hilker, M; Kissler-Patig, M; Richtler, T; Infante, L; Quintana, H
We present a photometric catalog (based on V and I photometry) of galaxies in the central regions of the Fornax galaxy cluster. Our 11 CCD fields cover 0.17 square degrees in total. The limiting surface brightness is around 24 mag arcsec(-2), similar to that of Ferguson's (1989) catalog, whereas our limiting total magnitude is around V similar or equal to 22 mag, about two magnitudes fainter. It is the surface brightness limit, however. that prevents us from detecting the counterparts of the faintest Local Group dwarf spheroidals. The photometric properties of all objects are presented as a catalog (Appendix A)(1). The properties and fit parameters of the surface brightness profiles for a sub-sample are presented as a second catalog (Appendix B)(1).
The cluster of galaxies Abell 970
(2001) Sodré, L; Proust, D; Capelato, HV; Neto, GBL; Cuevas, H; Quintana, H; Fouqué, P
We present a dynamical analysis of the galaxy cluster Abell 970 based on a new set of radial velocities measured at ESO, Pic du Midi and Haute-Provence observatories. Our analysis indicates that this cluster has a substructure and is out of dynamical equilibrium. This conclusion is also supported by differences in the positions of the peaks of the surface density distribution and X-ray emission, as well as by the evidence of a large-scale velocity gradient in the cluster. We also found a discrepancy between the masses inferred with the virial theorem and those inferred with the X-ray emission, which is expected if the galaxies and the gas inside the cluster are not in hydrostatic equilibrium. Abell 970 has a modest cooling ow, as is expected if it is out of equilibrium. We propose that cooling flows may have an intermittent behaviour, with phases of massive cooling flows being followed by phases without significant cooling flows after the accretion of a galaxy group massive enough to disrupt the dynamical equilibrium in the centre of the clusters. A massive cooling ow will be established again, after a new equilibrium is achieved.
The Shapley Supercluster. II. Spectroscopic observations in a wide area and general morphology
(2000) Quintana, H; Carrasco, ER; Reisenegger, A
We report 2868 new multiobject spectroscopic measurements of galaxy redshifts in an area roughly 12 degrees x 6 degrees (right ascension x declination) centered on the Shapley Supercluster (SSC). These correspond to 2627 different galaxies. Including other measurements reported in the literature, the total number of galaxies with measured redshifts in a 19 degrees x 16 degrees area centered on the supercluster now reaches 5090. Of these, 949 lie in the redshift range 9000-18,000 km s(-1), which we tentatively identify with the SSC. This unprecedented sample allows a quite detailed qualitative morphological study of the SSC. Based on the three-dimensional distribution of galaxies and clusters of galaxies, we identify several subcondensations of the supercluster, as well as walls and filaments connecting them. We also iind another supercluster in the background, at redshift similar to 23,000 km s(-1).
The shapley supercluster. III. Collapse dynamics and mass of the central concentration
(2000) Reisenegger, A; Quintana, H; Carrasco, ER; Maze, J
We present the first application of a spherical collapse model to a supercluster of galaxies. Positions and redshifts of similar to 3000 galaxies in the Shapley supercluster (SSC) are used to define velocity caustics that limit the gravitationally collapsing structure in its central part. This is found to extend at least to 8 h(-1) Mpc of the central cluster, A3558, enclosing 11 ACO clusters. Infall velocities reach similar to 2000 km s(-1). Dynamical models of the collapsing region are used to estimate its mass profile. An upper bound on the mass, based on a pure spherical infall model, gives M(<8 h(-1) Mpc) less than or similar to 1.3 x 10(16) h(-1) M. for an Einstein-de Sitter (critical) universe and M(<8 h(-1) Mpc) less than or similar to 8.5 x 10(15) h(-1) M. for an empty universe. The Diaferio & Geller model, based on estimating the escape velocity, gives a significantly lower value, M(<8 h(-1) Mpc) approximate to 2.1 x 10(15) h(-1) M., very similar to the mass Geller et al. found around the Coma cluster by the same method and comparable to or slightly lower than the dynamical mass in the vriialized regions of clusters enclosed in the same region of the SSC. In both models, the overdensity in this region is substantial, but it is far from the value required to account for the peculiar motion of the Local Group with respect to the cosmic microwave background.
Velocity dispersions and cluster properties in the Southern Abell Redshift Survey clusters. II.
(2002) Muriel, H; Quintana, H; Infante, L; Lambas, DG; Way, MJ
We report an analysis of the dynamical structure of clusters of galaxies from a survey of photometric and spectroscopic observations in the fields of southern Abell clusters. We analyze the galaxy velocity field in extended regions up to 7 h(-1) Mpc from cluster centers, and we estimate mean velocity dispersions and their radial dependence. Only one from a total of 41 Abell clusters does not correspond to a dynamically bound system. However, four of these bound objects are double clusters. We estimate that 20% (seven clusters) of the 35 remaining are subject to serious projection effects. Normalizing the clustercentric distances by means of the overdensity radius r(200), and the velocity dispersion profiles (VDPs) by the corresponding mean cluster velocity dispersion, we computed the average VDP. Our results indicate a at behavior of the mean VDP at large distances from the cluster center. Nevertheless, we found that for the inner part of the clusters (r/r(200)less than or equal to1) the VDP is up to 10% smaller than at larger radii.

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