Examinando por Autor "Hempel, A."
Mostrando 1 - 6 de 6
Resultados por página
Opciones de ordenación
Ítem Comparison of Sunyaev-Zel'dovich measurements from Planck and from the Arcminute Microkelvin Imager for 99 galaxy clusters(EDP Sciences, 2015-08) Perrott, Y.C.; Olamaie, M.; Rumsey, C.; Brown, M.L.; Feroz, F.; Grainge, K.J.B.; Hobson, M.P.; Lasenby, A.N.; MacTavish, C.J.; Pooley, G.G.; Saunders, R.D.E.; Schammel, M.P.; Scott, P.F.; Shimwell, T.W.; Titterington, D.J.; Waldram, E.M.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aussel, H.; Barrena, R.; Bikmaev, I.; Böhringer, H.; Burenin, R.; Carvalho, P.; Chon, G.; Comis, B.; Dahle, H.; Democles, J.; Douspis, M.; Harrison, D.; Hempel, A.; Hurier, G.; Khamitov, I.; Kneissl, R.; MacÍas-Pérez, J.F.; Melin, J.-B.; Pointecouteau, E.; Pratt, G.W.; Rubiño-Martín, J.A.; Stolyarov, V.; Sutton, D.We present observations and analysis of a sample of 123 galaxy clusters from the 2013 Planck catalogue of Sunyaev-Zel'dovich sources with the Arcminute Microkelvin Imager (AMI), a ground-based radio interferometer. AMI provides an independent measurement with higher angular resolution, 3 arcmin compared to the Planck beams of 5-10 arcmin. The AMI observations thus provide validation of the cluster detections, improved positional estimates, and a consistency check on the fitted size (θs) and flux (Ytot) parameters in the generalised Navarro, Frenk and White (GNFW) model. We detect 99 of the clusters. We use the AMI positional estimates to check the positional estimates and error-bars produced by the Planck algorithms PowellSnakes and MMF3. We find that Ytot values as measured by AMI are biased downwards with respect to the Planck constraints, especially for high Planck-S/N clusters. We perform simulations to show that this can be explained by deviation from the universal pressure profile shape used to model the clusters. We show that AMI data can constrain the α and β parameters describing the shape of the profile in the GNFW model for individual clusters provided careful attention is paid to the degeneracies between parameters, but one requires information on a wider range of angular scales than are present in AMI data alone to correctly constrain all parameters simultaneously. © 2015 ESO.Ítem COSMOGRAIL: XVII. Time delays for the quadruply imaged quasar PG 1115+080(EDP Sciences, 2018-08) Bonvin, V.; Chan, J.H.H.; Millon, M.; Rojas, K.; Courbin, F.; Chen, G.C.-F.; Fassnacht, C.D.; Paic, E.; Tewes, M.; Chao, D.C.-Y.; Chijani, M.; Gilman, D.; Gilmore, K.; Williams, P.; Buckley-Geer, E.; Frieman, J.; Marshall, P.J.; Suyu, S.H.; Treu, T.; Hempel, A.; Kim, S.; Lachaume, R.; Rabus, M.; Anguita, T.; Meylan, G.; Motta, V.; Magain, P.We present time-delay estimates for the quadruply imaged quasar PG 1115+080. Our results are based on almost daily observations for seven months at the ESO MPIA 2.2 m telescope at La Silla Observatory, reaching a signal-to-noise ratio of about 1000 per quasar image. In addition, we re-analyze existing light curves from the literature that we complete with an additional three seasons of monitoring with the Mercator telescope at La Palma Observatory. When exploring the possible source of bias we considered the so-called microlensing time delay, a potential source of systematic error so far never directly accounted for in previous time-delay publications. In 15 yr of data on PG 1115+080, we find no strong evidence of microlensing time delay. Therefore not accounting for this effect, our time-delay estimates on the individual data sets are in good agreement with each other and with the literature. Combining the data sets, we obtain the most precise time-delay estimates to date on PG 1115+080, with Δt(AB) = 8.3+1.5 -1.6 days (18.7% precision), Δt(AC) = 9.9+1.1 -1.1 days (11.1%) and Δt(BC) = 18.8+1.6 -1.6 days (8.5%). Turning these time delays into cosmological constraints is done in a companion paper that makes use of ground-based Adaptive Optics (AO) with the Keck telescope. © ESO 2018.Ítem Optical validation and characterisation of Planck PSZ1 sources at the Canary Islands observatories: II. Second year of ITP13 observations(EDP Sciences, 2020-06) Barrena, R.; Ferragamo, A.; Rubiño-Martín, J.A.; Streblyanska, A.; Aguado-Barahona, A.; Tramonte, D.; Génova-Santos, R.T.; Hempel, A.; Lietzen, H.; Aghanim, N.; Arnaud, M.; Böhringer, H.We report new galaxy clusters previously unknown included in the first Planck Sunyaev Zeldovich (SZ) sources catalogue, the PSZ1. The results presented here were achieved during the second year of a two-year observational programme, the ITP13, developed at the Roque de los Muchachos Observatory (La Palma, Spain). Using the 2.5m Isaac Newton telescope, the 3.5m Telescopio Nazionale Galileo, the 4.2 m William Herschel telescope and the 10.4 m Gran Telescopio Canarias we characterised 75 SZ sources with low SZ significance, SZ S=N < 5:32. We performed deep optical imaging and spectroscopy in order to associate actual galaxy clusters with the SZ Planck source. We adopted robust criteria, based on the 2D spatial distribution, richness, and velocity dispersions to confirm actual optical counterparts up to z < 0:85. The selected systems are confirmed only if they are well aligned with respect to the PSZ1 coordinate and show high richness and high velocity dispersion. In addition, we also inspected the Compton y-maps and SZ significance in order to identify unrealistic detections. Following this procedure, we identify 26 cluster counterparts associated with the SZ emission, which means that only about 35% of the clusters considered in this low S/N PSZ1 subsample are validated. Forty-nine SZ sources (65% of this PSZ1 subset) remain unconfirmed. At the end of the ITP13 observational programme, we have studied 256 SZ sources with Dec 15 (212 of them completely unknown), finding optical counterparts for 152 SZ sources. The ITP13 validation programme has allowed us to update the PSZ1 purity, which is now more refined, increasing from 72% to 83% in the low SZ S/N regime. Our results are consistent with the predicted purity curve for the full PSZ1 catalogue and with the expected fraction of false detections caused by the non-Gaussian noise of foreground signals. We find a strong correlation between the number of unconfirmed sources and the thermal emission of diffiuse galactic dust at 857 GHz, thus increasing the fraction of false Planck SZ detections at low galactic latitudes. © 2020 EDP Sciences. All rights reserved.Ítem Optical validation and characterization of Planck PSZ1 sources at the Canary Islands observatories: I. First year of ITP13 observations(EDP Sciences, 2018-08) Barrena, R.; Streblyanska, A.; Ferragamo, A.; Rubiño-Martín, J.A.; Aguado-Barahona, A.; Tramonte, D.; Génova-Santos, R.T.; Hempel, A.; Lietzen, H.; Aghanim, N.; Arnaud, M.; Böhringer, H.; Chon, G.; Democles, J.; Dahle, H.; Douspis, M.; Lasenby, A.N.; Mazzotta, P.; Melin, J.B.; Pointecouteau, E.; Pratt, G.W.; Rossetti, M.; Van Der Burg, R.F.J.We have identified new clusters and characterized previously unknown Planck Sunyaev-Zeldovich (SZ) sources from the first Planck catalogue of SZ sources (PSZ1). The results presented here correspond to an optical follow-up observational programme developed during approximately one year (2014) at Roque de los Muchachos Observatory, using the 2.5 m Isaac Newton telescope, the 3.5 m Telescopio Nazionale Galileo, the 4.2 m William Herschel telescope and the 10.4 m Gran Telescopio Canarias. We have characterized 115 new PSZ1 sources using deep optical imaging and spectroscopy. We adopted robust criteria in order to consolidate the SZ counterparts by analysing the optical richness, the 2D galaxy distribution, and velocity dispersions of clusters. Confirmed counterparts are considered to be validated if they are rich structures, well aligned with the Planck PSZ1 coordinate and show relatively high velocity dispersion. Following this classification, we confirm 53 clusters, which means that 46% of this PSZ1 subsample has been validated and characterized with this technique. Sixty-Two SZ sources (54% of this PSZ1 subset) remain unconfirmed. In addition, we find that the fraction of unconfirmed clusters close to the galactic plane (at |b| < 25°) is greater than that at higher galactic latitudes (|b| > 25°), which indicates contamination produced by radio emission of galactic dust and gas clouds on these SZ detections. In fact, in the majority of the cases, we detect important galactic cirrus in the optical images, mainly in the SZ target located at low galactic latitudes, which supports this hypothesis. © ESO 2018.Ítem Planck intermediate results: XXXVI. Optical identification and redshifts of Planck SZ sources with telescopes at the Canary Islands observatories(EDP Sciences, 2016-02) Ade, P.A.R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A.J.; Barreiro, R.B.; Barrena, R.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bikmaev, I.; Böhringer, H.; Bonaldi, A.; Bonavera, L.; Bond, J.R.; Borrill, J.; Bouchet, F.R.; Burenin, R.; Burigana, C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chary, R.-R.; Chiang, H.C.; Chon, G.; Christensen, P.R.; Clements, D.L.; Colombo, L.P.L.; Combet, C.; Comis, B.; Crill, B.P.; Curto, A.; Cuttaia, F.; Dahle, H.; Danese, L.; Davies, R.D.; Davis, R.J.; De Bernardis, P.; De Rosa, A.; De Zotti, G.; Delabrouille, J.; Diego, J.M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T.A.; Eriksen, H.K.; Ferragamo, A.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A.A.; Franceschi, E.; Fromenteau, S.; Galeotta, S.; Galli, S.; Ganga, K.; Génova-Santos, R.T.; Giard, M.; Gjerløw, E.; González-Nuevo, J.; Górski, K.M.; Gruppuso, A.; Hansen, F.K.; Harrison, D.L.; Hempel, A.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S.R.; Hivon, E.; Hornstrup, A.; Hovest, W.; Huffenberger, K.M.; Hurier, G.; Jaffe, T.R.; Keihänen, E.; Keskitalo, R.; Khamitov, I.; Kisner, T.S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C.R.; Leonardi, R.; León-Tavares, J.; Levrier, F.; Lietzen, H.; Liguori, M.; Lilje, P.B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P.M.; Macías-Pérez, J.F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Martin, P.G.; Martínez-González, E.; Masi, S.; Matarrese, S.; McGehee, P.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J.A.; Naselsky, P.; Nati, F.; Natoli, P.; Novikov, D.; Novikov, I.; Oxborrow, C.A.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Perdereau, O.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G.W.; Prunet, S.; Puget, J.-L.; Rachen, J.P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J.A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Stolyarov, V.; Streblyanska, A.; Sudiwala, R.; Sunyaev, R.; Suur-Uski, A.-S.; Sygnet J.-F.; Tauber, J.A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tramonte, D.; Tristram, M.; Tucci, M.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L.A.; Wandelt, B.D.; Wehus, I.K.; Yvon, D.; Zacchei, A.; Zonca, A.We present the results of approximately three years of observations of Planck Sunyaev-Zeldovich (SZ) sources with telescopes at the Canary Islands observatories as part of the general optical follow-up programme undertaken by the Planck Collaboration. In total, 78 SZ sources are discussed. Deep-imaging observations were obtained for most of these sources; spectroscopic observations in either in long-slit or multi-object modes were obtained for many. We effectively used 37.5 clear nights. We found optical counterparts for 73 of the 78 candidates. This sample includes 53 spectroscopic redshift determinations, 20 of them obtained with a multi-object spectroscopic mode. The sample contains new redshifts for 27 Planck clusters that were not included in the first Planck SZ source catalogue (PSZ1).Ítem The VVV templates project towards an automated classification of VVV light-curves: I. Building a database of stellar variability in the near-infrared(EDP Sciences, 2014-07) Angeloni, R.; Contreras Ramos, R.; Catelan, M.; Dékány, I.; Gran, F.; Alonso-García, J.; Hempel, M.; Navarrete, C.; Andrews, H.; Aparicio, A.; Beamín, J.C.; Berger, C.; Borissova, J.; Contreras Peña, C.; Cunial, A.; De Grijs, R.; Espinoza, N.; Eyheramendy, S.; Eyheramendy, S.; Fiaschi, M.; Hajdu, G.; Han, J.; Hełminiak, K.G.; Hempel, A.; Hidalgo, S.L.; Ita, Y.; Jeon Y., -B; Jordán, A.; Kwon, J.; Lee, J.T.; Martín, E.L.; Masetti, N.; Matsunaga, N.; Milone, A.P.; Minniti, D.; Morelli, L.; Murgas, F.; Nagayama, T.; Navarro, C.; Ochner, P.; Pérez, P.; Pichara, K.; Rojas-Arriagada, A.; Roquette, J.; Saito, R.K.; Siviero, A.; Sohn, J.; Sung, H.-I.; Tamura, M.; Tata, R.; Tomasella, L.; Townsend, B.; Whitelock, P.Context. The Vista Variables in the Vía Láctea (VVV) ESO Public Survey is a variability survey of the Milky Way bulge and an adjacent section of the disk carried out from 2010 on ESO Visible and Infrared Survey Telescope for Astronomy (VISTA). The VVV survey will eventually deliver a deep near-IR atlas with photometry and positions in five passbands (ZYJHKS) and a catalogue of 1−10 million variable point sources – mostly unknown – that require classifications. Aims. The main goal of the VVV Templates Project, which we introduce in this work, is to develop and test the machine-learning algorithms for the automated classification of the VVV light-curves. As VVV is the first massive, multi-epoch survey of stellar variability in the near-IR, the template light-curves that are required for training the classification algorithms are not available. In the first paper of the series we describe the construction of this comprehensive database of infrared stellar variability. Methods. First, we performed a systematic search in the literature and public data archives; second, we coordinated a worldwide observational campaign; and third, we exploited the VVV variability database itself on (optically) well-known stars to gather high-quality infrared light-curves of several hundreds of variable stars. Results. We have now collected a significant (and still increasing) number of infrared template light-curves. This database will be used as a training-set for the machine-learning algorithms that will automatically classify the light-curves produced by VVV. The results of such an auto mated classification will be covered in forthcoming papers of the series.