Publications


Search for dark matter annihilations in the Sun with the 79-string IceCube detector

ArXiv (2012)

I collaboration, MG Aartsen, R Abbasi, Y Abdou, M Ackermann, J Adams, JA Aguilar, M Ahlers, D Altmann, K Andeen, J Auffenberg, X Bai, M Baker, SW Barwick, V Baum, R Bay, K Beattie, JJ Beatty, S Bechet, JB Tjus, KH Becker, M Bell, ML Benabderrahmane, S BenZvi, J Berdermann, P Berghaus, D Berley, E Bernardini, D Bertrand, DZ Besson, D Bindig, M Bissok, E Blaufuss, J Blumenthal, DJ Boersma, S Bohaichuk, C Bohm, D Bose1, S Böser, O Botner, L Brayeur, AM Brown, R Bruijn, J Brunner, S Buitink, M Carson, J Casey, M Casier, D Chirkin, B Christy, K Clark, F Clevermann, S Cohen, DF Cowen, AHC Silva, M Danninger, J Daughhetee, JC Davis, CD Clercq, SD Ridder, F Descamps, P Desiati, GD Vries-Uiterweerd, T DeYoung, JC Díaz-Vélez, J Dreyer, JP Dumm, M Dunkman, R Eagan, B Eberhardt, J Eisch, RW Ellsworth, O Engdegård, S Euler, PA Evenson, O Fadiran, AR Fazely, A Fedynitch, J Feintzeig, T Feusels, K Filimonov, C Finley, T Fischer-Wasels, S Flis, A Franckowiak, R Franke, K Frantzen, T Fuchs, TK Gaisser, J Gallagher, L Gerhardt, L Gladstone, T Glüsenkamp, A Goldschmidt, G Golup, JA Goodman, D Góra, D Grant, A Groß, S Grullon, M Gurtner, C Ha, AH Ismail, A Hallgren, F Halzen, K Hanson, D Heereman, P Heimann, D Heinen, K Helbing, R Hellauer, S Hickford, GC Hill, KD Hoffman, R Hoffmann, A Homeier, K Hoshina, W Huelsnitz, PO Hulth, K Hultqvist, S Hussain, A Ishihara, E Jacobi, J Jacobsen, GS Japaridze, O Jlelati, A Kappes, T Karg, A Karle, J Kiryluk, F Kislat, J Kläs, SR Klein, JH Köhne, G Kohnen, H Kolanoski, L Köpke, C Kopper, S Kopper, DJ Koskinen, M Kowalski, M Krasberg, G Kroll, J Kunnen, N Kurahashi, T Kuwabara, M Labare, H Landsman, MJ Larson, R Lauer, M Lesiak-Bzdak, J Lünemann, J Madsen, R Maruyama, K Mase, HS Matis, F McNally, K Meagher, M Merck, P Mészáros, T Meures, S Miarecki, E Middell, N Milke, J Miller, L Mohrmann, T Montaruli, R Morse, R Nahnhauer, U Naumann, SC Nowicki, DR Nygren, A Obertacke, S Odrowski, A Olivas, M Olivo, A O'Murchadha, S Panknin, L Paul, JA Pepper, CPDL Heros, D Pieloth, N Pirk, J Posselt, PB Price, GT Przybylski, L Rädel, K Rawlins, P Redl, E Resconi, W Rhode, M Ribordy, M Richman, B Riedel, JP Rodrigues, C Rott, T Ruhe, B Ruzybayev, D Ryckbosch, SM Saba, T Salameh, HG Sander, M Santander, S Sarkar, K Schatto, M Scheel, F Scheriau, T Schmidt, M Schmitz, S Schoenen, S Schöneberg, L Schönherr, A Schönwald, A Schukraft, L Schulte, O Schulz, D Seckel, SH Seo, Y Sestayo, S Seunarine, C Sheremata, MWE Smith, M Soiron, D Soldin, GM Spiczak, C Spiering, M Stamatikos, T Stanev, A Stasik, T Stezelberger, RG Stokstad, A Stöß, EA Strahler, R Ström, GW Sullivan, H Taavola, I Taboada, A Tamburro, S Ter-Antonyan, S Tilav, PA Toale, S Toscano, M Usner, DVD Drift, NV Eijndhoven, AV Overloop, JV Santen, M Vehring, M Voge1, M Vraeghe, C Walck, T Waldenmaier, M Wallraff, M Walter, R Wasserman, C Weaver, C Wendt, S Westerhoff, N Whitehorn, K Wiebe, CH Wiebusch, DR Williams, H Wissing, M Wolf, TR Wood, K Woschnagg, C Xu, DL Xu, XW Xu, JP Yanez, G Yodh, S Yoshida, P Zarzhitsky, J Ziemann, S Zierke, A Zilles, M Zoll

We have performed a search for muon neutrinos from dark matter annihilation in the center of the Sun with the 79-string configuration of the IceCube neutrino telescope. For the first time, the DeepCore sub-array is included in the analysis, lowering the energy threshold and extending the search to the austral summer. The 317 days of data collected between June 2010 and May 2011 are consistent with the expected background from atmospheric muons and neutrinos. Upper limits are therefore set on the dark matter annihilation rate, with conversions to limits on spin-dependent and spin-independent WIMP-proton cross-sections for WIMP masses in the range 20 - 5000 GeV. These are the most stringent spin-dependent WIMP-proton cross-sections limits to date above 35 GeV.


Measurement of Atmospheric Neutrino Oscillations with IceCube

ArXiv (2013)

TI Collaboration

We present the first statistically significant detection of neutrino oscillations in the high-energy regime ($>$ 20 GeV) from an analysis of IceCube Neutrino Observatory data collected in 2010-2011. This measurement is made possible by the low energy threshold of the DeepCore detector ($\sim 20$ GeV) and benefits from the use of the IceCube detector as a veto against cosmic ray-induced muon background. The oscillation signal was detected within a low-energy muon neutrino sample (20 -- 100 GeV) extracted from data collected by DeepCore. A high-energy muon neutrino sample (100 GeV -- 10 TeV) was extracted from IceCube data to constrain systematic uncertainties. Disappearance of low-energy upward-going muon neutrinos was observed, and the non-oscillation hypothesis is rejected with more than $5\sigma$ significance. In a two-neutrino flavor formalism, our data are best described by the atmospheric neutrino oscillation parameters $\Delta m^2_{23}= (2.3^{+0.6}_{-0.5})\cdot 10^{-3}$ eV$^2$ and $\sin^2(2 \theta_{23})>0.93$, and maximum mixing is favored.


Comparison between x-ray scattering and velocity-interferometry measurements from shocked liquid deuterium

Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 87 (2013)

K Falk, BJB Crowley, CD Murphy, JS Wark, G Gregori, SP Regan, SX Hu, PB Radha, J Vorberger, DO Gericke, SH Glenzer, AP Jephcoat

The equation of state of light elements is essential to understand the structure of Jovian planets and inertial confinement fusion research. The Omega laser was used to drive a planar shock wave in the cryogenically cooled deuterium, creating warm dense matter conditions. X-ray scattering was used to determine the spectrum near the boundary of the collective and noncollective scattering regimes using a narrow band x-ray source in backscattering geometry. Our scattering spectra are thus sensitive to the individual electron motion as well as the collective plasma behavior and provide a measurement of the electron density, temperature, and ionization state. Our data are consistent with velocity-interferometry measurements previously taken on the same shocked deuterium conditions and presented by K. Falk. This work presents a comparison of the two diagnostic systems and offers a detailed discussion of challenges encountered. ©2013 American Physical Society.


CONSTRAINTS ON THE ORIGIN OF COSMIC RAYS ABOVE 10(18) eV FROM LARGE-SCALE ANISOTROPY SEARCHES IN DATA OF THE PIERRE AUGER OBSERVATORY

ASTROPHYSICAL JOURNAL LETTERS 762 (2013) ARTN L13

P Abreu, M Aglietta, M Ahlers, EJ Ahn, IFM Albuquerque, D Allard, I Allekotte, J Allen, P Allison, A Almela, J Alvarez Castillo, J Alvarez-Muniz, R Alves Batista, M Ambrosio, A Aminaei, L Anchordoqui, S Andringa, T Antici'c, C Aramo, E Arganda, F Arqueros, H Asorey, P Assis, J Aublin, M Ave, M Avenier, G Avila, AM Badescu, M Balzer, KB Barber, AF Barbosa, R Bardenet, SLC Barroso, B Baughman, J Baeuml, C Baus, JJ Beatty, KH Becker, A Belletoile, JA Bellido, S BenZvi, C Berat, X Bertou, PL Biermann, P Billoir, F Blanco, M Blanco, C Bleve, H Bluemer, M Bohacova, D Boncioli, C Bonifazi, R Bonino, N Borodai, J Brack, I Brancus, P Brogueira, WC Brown, R Bruijn, P Buchholz, A Bueno, L Buroker, RE Burton, KS Caballero-Mora, B Caccianiga, L Caramete, R Caruso, A Castellina, O Catalano, G Cataldi, L Cazon, R Cester, J Chauvin, SH Cheng, A Chiavassa, JA Chinellato, J Chirinos Diaz, J Chudoba, M Cilmo, RW Clay, G Cocciolo, L Collica, MR Coluccia, R Conceicao, F Contreras, H Cook, MJ Cooper, J Coppens, A Cordier, S Coutu, CE Covault, A Creusot, A Criss, J Cronin, A Curutiu, S Dagoret-Campagne, R Dallier, B Daniel, S Dasso, K Daumiller, BR Dawson, RM de Almeida, M De Domenico, C De Donato, SJ de Jong, G De La Vega, DMWJM Jr, JRT de Mello Neto, I De Mitri, V de Souza, KD de Vries, L del Peral, M del Rio, O Deligny, H Dembinski, N Dhital, C Di Giulio, ML Diaz Castro, PN Diep, F Diogo, C Dobrigkeit, W Docters, JC D'Olivo, PN Dong, A Dorofeev, JC dos Anjos, MT Dova, D D'Urso, I Dutan, J Ebr, R Engel, M Erdmann, CO Escobar, J Espadanal, A Etchegoyen, P Facal San Luis, H Falcke, K Fang, G Farrar, AC Fauth, N Fazzini, AP Ferguson, B Fick, JM Figueira, A Filevich, A Filipcic, S Fliescher, CE Fracchiolla, ED Fraenkel, O Fratu, U Froehlich, B Fuchs, R Gaior, RF Gamarra, S Gambetta, B Garcia, ST Garcia Roca, D Garcia-Gamez, D Garcia-Pinto, G Garilli, A Gascon Bravo, H Gemmeke, PL Ghia, M Giller, J Gitto, H Glass, MS Gold, G Golup, F Gomez Albarracin, M Gomez Berisso, PF Gomez Vitale, P Goncalves, JG Gonzalez, B Gookin, A Gorgi, P Gouffon, E Grashorn, S Grebe, N Griffith, AF Grillo, Y Guardincerri, F Guarino, GP Guedes, P Hansen, D Harari, TA Harrison, JL Harton, A Haungs, T Hebbeker, D Heck, AE Herve, GC Hill, C Hojvat, N Hollon, VC Holmes, P Homola, JR Hoerandel, P Horvath, M Hrabovsky, D Huber, T Huege, A Insolia, F Ionita, A Italiano, S Jansen, C Jarne, S Jiraskova, M Josebachuili, K Kadija, KH Kampert, P Karhan, P Kasper, I Katkov, B Kegl, B Keilhauer, A Keivani, JL Kelley, E Kemp, RM Kieckhafer, HO Klages, M Kleifges, J Kleinfeller, J Knapp, D-H Koang, K Kotera, N Krohm, O Kroemer, D Kruppke-Hansen, D Kuempel, JK Kulbartz, N Kunka, G La Rosa, C Lachaud, D LaHurd, L Latronico, R Lauer, P Lautridou, S Le Coz, MSAB Leao, D Lebrun, P Lebrun, MA Leigui de Oliveira, A Letessier-Selvon, I Lhenry-Yvon, K Link, R Lopez, A Lopez Agueera, K Louedec, J Lozano Bahilo, L Lu, A Lucero, M Ludwig, H Lyberis, MC Maccarone, C Macolino, S Maldera, J Maller, D Mandat, P Mantsch, AG Mariazzi, J Marin, V Marin, IC Maris, HR Marquez Falcon, G Marsella, D Martello, L Martin, H Martinez, O Martinez Bravo, D Martraire, JJ Masias Meza, HJ Mathes, J Matthews, JAJ Matthews, G Matthiae, D Maurel, D Maurizio, PO Mazur, G Medina-Tanco, M Melissas, D Melo, E Menichetti, A Menshikov, P Mertsch, S Messina, C Meurer, R Meyhandan, S Mi'canovi'c, MI Micheletti, IA Minaya, L Miramonti, L Molina-Bueno, S Mollerach, M Monasor, D Monnier Ragaigne, F Montanet, B Morales, C Morello, E Moreno, JC Moreno, M Mostafa, CA Moura, MA Muller, G Mueller, M Muenchmeyer, R Mussa, G Navarra, JL Navarro, S Navas, P Necesal, L Nellen, A Nelles, J Neuser, PT Nhung, M Niechciol, L Niemietz, N Nierstenhoefer, D Nitz, D Nosek, L Nozka, J Oehlschlaeger, A Olinto, M Ortiz, N Pacheco, DP Selmi-Dei, M Palatka, J Pallotta, N Palmieri, G Parente, E Parizot, A Parra, S Pastor, T Paul, M Pech, J Pekala, R Pelayo, IM Pepe, L Perrone, R Pesce, E Petermann, S Petrera, A Petrolini, Y Petrov, C Pfendner, R Piegaia, T Pierog, P Pieroni, M Pimenta, V Pirronello, M Platino, M Plum, VH Ponce, M Pontz, A Porcelli, P Privitera, M Prouza, EJ Quel, S Querchfeld, J Rautenberg, O Ravel, D Ravignani, B Revenu, J Ridky, S Riggi, M Risse, P Ristori, H Rivera, V Rizi, J Roberts, W Rodrigues de Carvalho, G Rodriguez, I Rodriguez Cabo, J Rodriguez Martino, J Rodriguez Rojo, MD Rodriguez-Frias, G Ros, J Rosado, T Rossler, M Roth, B Rouille-d'Orfeuil, E Roulet, AC Rovero, C Ruehle, A Saftoiu, F Salamida, H Salazar, F Salesa Greus, G Salina, F Sanchez, CE Santo, E Santos, EM Santos, F Sarazin, B Sarkar, S Sarkar, R Sato, N Scharf, V Scherini, H Schieler, P Schiffer, A Schmidt, O Scholten, H Schoorlemmer, J Schovancova, P Schovanek, F Schroeder, D Schuster, SJ Sciutto, M Scuderi, A Segreto, M Settimo, A Shadkam, RC Shellard, I Sidelnik, G Sigl, HH Silva Lopez, O Sima, A 'Smiallkowski, R Smida, GR Snow, P Sommers, J Sorokin, H Spinka, R Squartini, YN Srivastava, S Stanic, J Stapleton, J Stasielak, M Stephan, A Stutz, F Suarez, T Suomijaervi, AD Supanitsky, T Susa, MS Sutherland, J Swain, Z Szadkowski, M Szuba, A Tapia, M Tartare, O Tascau, R Tcaciuc, NT Thao, D Thomas, J Tiffenberg, C Timmermans, W Tkaczyk, CJ Todero Peixoto, G Toma, L Tomankova, B Tome, A Tonachini, G Torralba Elipe, P Travnicek, DB Tridapalli, G Tristram, E Trovato, M Tueros, R Ulrich, M Unger, M Urban, JF Valdes Galicia, I Valino, L Valore, G van Aar, AM van den Berg, S van Velzen, A van Vliet, E Varela, B Vargas Cardenas, JR Vazquez, RA Vazquez, D Veberic, V Verzi, J Vicha, M Videla, L Villasenor, H Wahlberg, P Wahrlich, O Wainberg, D Walz, AA Watson, M Weber, K Weidenhaupt, A Weindl, F Werner, S Westerhoff, BJ Whelan, A Widom, G Wieczorek, L Wiencke, B Wilczynska, H Wilczynski, M Will, C Williams, T Winchen, M Wommer, B Wundheiler, T Yamamoto, T Yapici, P Younk, G Yuan, A Yushkov, B Zamorano Garcia, E Zas, D Zavrtanik, M Zavrtanik, I Zaw, A Zepeda, J Zhou, Y Zhu, M Zimbres Silva, M Ziolkowski, PA Collaboration


Probing the origin of cosmic-rays with extremely high energy neutrinos using the IceCube Observatory

ArXiv (2013)

I Collaboration, MG Aartsen, R Abbasi, M Ackermann, J Adams, JA Aguilar, M Ahlers, D Altmann, C Arguelles, J Auffenberg, X Bai, M Baker, SW Barwick, V Baum, R Bay, JJ Beatty, JB Tjus, KH Becker, S BenZvi, P Berghaus, D Berley, E Bernardini, A Bernhard, DZ Besson, G Binder, D Bindig, M Bissok, E Blaufuss, J Blumenthal, DJ Boersma, C Bohm, D Bose, S Böser, O Botner, L Brayeur, HP Bretz, AM Brown, R Bruijn, J Casey, M Casier, D Chirkin, A Christov, B Christy, K Clark, F Clevermann, S Coenders, S Cohen, DF Cowen, AHC Silva, M Danninger, J Daughhetee, JC Davis, M Day, CD Clercq, SD Ridder, P Desiati, KDD Vries, MD With, T DeYoung, JC Díaz-Vélez, M Dunkman, R Eagan, B Eberhardt, J Eisch, S Euler, PA Evenson, O Fadiran, AR Fazely, A Fedynitch, J Feintzeig, T Feusels, K Filimonov, C Finley, T Fischer-Wasels, S Flis, A Franckowiak, K Frantzen, T Fuchs, TK Gaisser, J Gallagher, L Gerhardt, L Gladstone, T Glüsenkamp, A Goldschmidt, G Golup, JG Gonzalez, JA Goodman, D Góra, DT Grandmont, D Grant, P Gretskov, JC Groh, A Groß, C Ha, AH Ismail, P Hallen, A Hallgren, F Halzen, K Hanson, D Heereman, D Heinen, K Helbing, R Hellauer, S Hickford, GC Hill, KD Hoffman, R Hoffmann, A Homeier, K Hoshina, W Huelsnitz, PO Hulth, K Hultqvist, S Hussain, A Ishihara, E Jacobi, J Jacobsen, K Jagielski, GS Japaridze, K Jero, O Jlelati, B Kaminsky, A Kappes, T Karg, A Karle, M Kauer, JL Kelley, J Kiryluk, J Kläs, SR Klein, JH Köhne, G Kohnen, H Kolanoski, L Köpke, C Kopper, S Kopper, DJ Koskinen, M Kowalski, M Krasberg, A Kriesten, K Krings, G Kroll, J Kunnen, N Kurahashi, T Kuwabara, M Labare, H Landsman, MJ Larson, M Lesiak-Bzdak, M Leuermann, J Leute, J Lünemann, O Macías, J Madsen, G Maggi, R Maruyama, K Mase, HS Matis, F McNally, K Meagher, M Merck, T Meures, S Miarecki, E Middell, N Milke, J Miller, L Mohrmann, T Montaruli, R Morse, R Nahnhauer, U Naumann, H Niederhausen, SC Nowicki, DR Nygren, A Obertacke, S Odrowski, A Olivas, A Omairat, A O'Murchadha, L Paul, JA Pepper, CPDL Heros, C Pfendner, D Pieloth, D Pieloth, E Pinat, J Posselt, PB Price, GT Przybylski, L Rädel, M Rameez, K Rawlins, P Redl, R Reimann, E Resconi, W Rhode, M Ribordy, M Richman, B Riedel, JP Rodrigues, C Rott, T Ruhe, B Ruzybayev, D Ryckbosch, SM Saba, HG Sander, M Santander, S Sarkar, K Schatto, F Scheriau, T Schmidt, M Schmitz, S Schoenen, S Schöneberg, A Schönwald, A Schukraft, L Schulte, O Schulz, D Seckel, Y Sestayo, S Seunarine, R Shanidze, C Sheremata, MWE Smith, D Soldin, GM Spiczak, C Spiering, M Stamatikos, T Stanev, NA Stanisha, A Stasik, T Stezelberger, RG Stokstad, A Stößl, EA Strahler, R Ström, GW Sullivan, H Taavola, I Taboada, A Tamburro, A Tepe, S Ter-Antonyan, G Tešić, S Tilav, PA Toale, MN Tobin, S Toscano, E Unger, M Usner, S Vallecorsa, NV Eijndhoven, AV Overloop, JV Santen, M Vehring, M Voge, M Vraeghe, C Walck, T Waldenmaier, M Wallraff, C Weaver, M Wellons, C Wendt, S Westerhoff, N Whitehorn, K Wiebe, CH Wiebusch, DR Williams, H Wissing, M Wolf, TR Wood, K Woschnagg, DL Xu, XW Xu, JP Yanez, G Yodh, S Yoshida, P Zarzhitsky, J Ziemann, S Zierke, M Zoll

We have searched for extremely high energy neutrinos using data taken with the IceCube detector between May 2010 and May 2012. Two neutrino induced particle shower events with energies around 1 PeV were observed, as reported previously. In this work, we investigate whether these events could originate from cosmogenic neutrinos produced in the interactions of ultra-high energy cosmic-rays with ambient photons while propagating through intergalactic space. Exploiting IceCube's large exposure for extremely high energy neutrinos and the lack of observed events above 100 PeV, we can rule out the corresponding models at more than 90% confidence level. The model independent quasi-differential 90% CL upper limit, which amounts to $E^2 \phi_{\nu_e + \nu_\mu + \nu_\tau} = 1.2 \times 10^{-7}$ GeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$ at 1 EeV, provides the most stringent constraint in the energy range from 10 PeV to 10 EeV. Our observation disfavors strong cosmological evolution of the highest energy cosmic ray sources such as the Fanaroff-Riley type II class of radio galaxies.


Magnetic field generation by Biermann battery and Weibel instability in laboratory shock waves

EAS Publications Series 58 (2012) 23-26

G Gregori, F Miniati, B Reville, RP Drake

Magnetic field generation in the Universe is still an open problem. Possible mechanisms involve the Weibel instability, due to anisotropic phase-space distributions, as well as the Biermann battery, due to misaligned density and temperature gradients. These mechanisms can be reproduced in scaled laboratory experiments. In this contribution we estimate the relative importance of these two processes and explore the laser-energy requirements for producing Weibel dominated shocks. © The Author(s) 2013.


Search for time-independent neutrino emission from astrophysical sources with 3 years of IceCube data

ArXiv (2013)

I Collaboration, MG Aartsen, R Abbasi, Y Abdou, M Ackermann, J Adams, JA Aguilar, M Ahlers, D Altmann, J Auffenberg, X Bai, M Baker, SW Barwick, V Baum, R Bay, JJ Beatty, S Bechet, JB Tjus, KH Becker, ML Benabderrahmane, S BenZvi, P Berghaus, D Berley, E Bernardini, A Bernhard, D Bertrand, DZ Besson, G Binder, D Bindig, M Bissok, E Blaufuss, J Blumenthal, DJ Boersma, S Bohaichuk, C Bohm, D Bose, S Böser, O Botner, L Brayeur, HP Bretz, AM Brown, R Bruijn, J Brunner, M Carson, J Casey, M Casier, D Chirkin, A Christov, B Christy, K Clark, F Clevermann, S Coenders, S Cohen, DF Cowen, AHC Silva, M Danninger, J Daughhetee, JC Davis, M Day, CD Clercq, SD Ridder, P Desiati, KDD Vries, MD With, T DeYoung, JCD iaz-Vélez, M Dunkman, R Eagan, B Eberhardt, J Eisch, RW Ellsworth, S Euler, PA Evenson, O Fadiran, AR Fazely, A Fedynitch, J Feintzeig, T Feusels, K Filimonov, C Finley, T Fischer-Wasels, S Flis, A Franckowiak, K Frantzen, T Fuchs, TK Gaisser, J Gallagher, L Gerhardt, L Gladstone, T Glüsenkamp, A Goldschmidt, G Golup, JG Gonzalez, JA Goodman, D Góra, DT Grandmont, D Grant, A Groß, C Ha, AH Ismail, P Hallen, A Hallgren, F Halzen, K Hanson, D Heereman, D Heinen, K Helbing, R Hellauer, S Hickford, GC Hill, KD Hoffman, R Hoffmann, A Homeier, K Hoshina, W Huelsnitz, PO Hulth, K Hultqvist, S Hussain, A Ishihara, E Jacobi, J Jacobsen, K Jagielski, GS Japaridze, K Jero, O Jlelati, B Kaminsky, A Kappes, T Karg, A Karle, JL Kelley, J Kiryluk, J Kläs, SR Klein, JH Köhne, G Kohnen, H Kolanosk, L Köpke, C Kopper, S Kopper, DJ Koskinen, M Kowalski, M Krasberg, K Krings, G Kroll, J Kunnen, N Kurahashi, T Kuwabara, M Labare, H Landsman, MJ Larson, M Lesiak-Bzdak, M Leuermann, J Leute, J Lünemann, O Macías, J Madsen, G Maggi, R Maruyama, K Mase, HS Matis, F McNally, K Meagher, M Merck, T Meures, S Miarecki, E Middell, N Milke, J Miller, L Mohrmann, T Montaruli, R Morse, R Nahnhauer, U Naumann, H Niederhausen, SC Nowicki, DR Nygren, A Obertacke, S Odrowski, A Olivas, A Omairat, A O'Murchadha, L Paul, JA Pepper, CPDL Heros, C Pfendner, D Pieloth, E Pinat, J Posselt, PB Price, GT Przybylski, L Rädel, M Rameez, K Rawlins, P Redl, R Reimann, E Resconi, W Rhode, M Ribordy, M Richman, B Riedel, JP Rodrigues, C Rott, T Ruhe, B Ruzybayev, D Ryckbosch, SM Saba, T Salameh, HG Sander, M Santander, S Sarkar, K Schatto, F Scheriau, T Schmidt, M Schmitz, S Schoenen, S Schöneberg, A Schönwald, A Schukraft, L Schulte, O Schulz, D Seckel, Y Sestayo, S Seunarine, R Shanidze, C Sheremata, MWE Smith, D Soldin, GM Spiczak, C Spiering, M Stamatikos, T Stanev, A Stasik, T Stezelberger, RG Stokstad, A Stößl, EA Strahler, R Ström, GW Sullivan, H Taavola, I Taboada, A Tamburro, A Tepe, S Ter-Antonyan, G Tešić, S Tilav, PA Toale, S Toscano, E Unger, M Usner, S Vallecorsa, NV Eijndhoven, AV Overloop, JV Santen, M Vehring, M Voge1, M Vraeghe, C Walck, T Waldenmaier, M Wallraff, C Weaver, M Wellons, C Wendt, S Westerhoff, N Whitehorn, K Wiebe, CH Wiebusch, DR Williams, H Wissing, M Wolf, TR Wood, K Woschnagg, DL Xu, XW Xu, JP Yanez, G Yodh, S Yoshida, P Zarzhitsky, J Ziemann, S Zierke, M Zoll

We present the results of a search for neutrino point sources using the IceCube data collected between April 2008 and May 2011 with three partially completed configurations of the detector: the 40-, 59- and 79-string configurations. The live-time of this data set are 1,040 days. An unbinned maximum likelihood ratio test was used to search for an excess of neutrinos above the atmospheric background at any given direction in the sky. By adding two more years of data with improved event selection and reconstruction techniques, the sensitivity was improved by a factor 3.5 or more with respect to the previously published results obtained with the 40-string configuration of IceCube. We performed an all-sky survey and a dedicated search using a catalog of \textit{a priori} selected objects observed by other telescopes. In both searches, the data are compatible with the background-only hypothesis. In the absence of evidence for a signal, we set upper limits on the flux of muon neutrinos. For an E$^{-2}$ neutrino spectrum, the observed limits are between 0.9 and $23.2\times 10^{-12}$ TeV$^{-1}$ cm$^{-2}$s$^{-1}$. We also report upper limits for neutrino emission from groups of sources which were selected according to theoretical models or observational parameters and analysed with a stacking approach.


Fast and Slow Rotators in the Densest Environments: a SWIFT IFS study of the Coma Cluster

ArXiv (2013)

RCW Houghton, RL Davies, F D'Eugenio, N Scott, N Thatte, F Clarke, M Tecza, GS Salter, LMR Fogarty, T Goodsall

We present integral-field spectroscopy of 27 galaxies in the Coma cluster observed with the Oxford SWIFT spectrograph, exploring the kinematic morphology-density relationship in a cluster environment richer and denser than any in the ATLAS3D survey. Our new data enables comparison of the kinematic morphology relation in three very different clusters (Virgo, Coma and Abell 1689) as well as to the field/group environment. The Coma sample was selected to match the parent luminosity and ellipticity distributions of the early-type population within a radius 15' (0.43 Mpc) of the cluster centre, and is limited to r' = 16 mag (equivalent to M_K = -21.5 mag), sampling one third of that population. From analysis of the lambda-ellipticity diagram, we find 15+-6% of early-type galaxies are slow rotators; this is identical to the fraction found in the field and the average fraction in the Virgo cluster, based on the ATLAS3D data. It is also identical to the average fraction found recently in Abell 1689 by D'Eugenio et al.. Thus it appears that the average slow rotator fraction of early type galaxies remains remarkably constant across many different environments, spanning five orders of magnitude in galaxy number density. However, within each cluster the slow rotators are generally found in regions of higher projected density, possibly as a result of mass segregation by dynamical friction. These results provide firm constraints on the mechanisms that produce early-type galaxies: they must maintain a fixed ratio between the number of fast rotators and slow rotators while also allowing the total early-type fraction to increase in clusters relative to the field. A complete survey of Coma, sampling hundreds rather than tens of galaxies, could probe a more representative volume of Coma and provide significantly stronger constraints, particularly on how the slow rotator fraction varies at larger radii.


Search for Relativistic Magnetic Monopoles with IceCube

ArXiv (2012)

I Collaboration, R Abbasi, Y Abdou, M Ackermann, J Adams, JA Aguilar, M Ahlers, D Altmann, K Andeen, J Auffenberg, X Bai, M Baker, SW Barwick, V Baum, R Bay, K Beattie, JJ Beatty, S Bechet, JB Tjus, KH Becker, M Bell, ML Benabderrahmane, S BenZvi, J Berdermann, P Berghaus, D Berley, E Bernardini, D Bertrand, DZ Besson, D Bindig, M Bissok, E Blaufuss, J Blumenthal, DJ Boersma, C Bohm, D Bose, S Böser, O Botner, L Brayeur, AM Brown, R Bruijn, J Brunner, S Buitink, M Carson, J Casey, M Casier, D Chirkin, B Christy, F Clevermann, S Cohen, DF Cowen, AHC Silva, M Danninger, J Daughhetee, JC Davis, CD Clercq, F Descamps, P Desiati, GD Vries-Uiterweerd, T DeYoung, JC Díaz-Vélez, J Dreyer, JP Dumm, M Dunkman, R Eagan, J Eisch, RW Ellsworth, O Engdegård, S Euler, PA Evenson, O Fadiran, AR Fazely, A Fedynitch, J Feintzeig, T Feusels, K Filimonov, C Finley, T Fischer-Wasels, S Flis, A Franckowiak, R Franke, K Frantzen, T Fuchs, TK Gaisser, J Gallagher, L Gerhardt, L Gladstone, T Glüsenkamp, A Goldschmidt, JA Goodman, D Góra, D Grant, A Groß, S Grullon, M Gurtner, C Ha, AH Ismail, A Hallgren, F Halzen, K Hanson, D Heereman, P Heimann, D Heinen, K Helbing, R Hellauer, S Hickford, GC Hill, KD Hoffman, R Hoffmann, A Homeier, K Hoshina, W Huelsnitz, PO Hulth, K Hultqvist, S Hussain, A Ishihara, E Jacobi, J Jacobsen, GS Japaridze, O Jlelati, A Kappes, T Karg, A Karle, J Kiryluk, F Kislat, J Kläs, SR Klein, JH Köhne, G Kohnen, H Kolanoski, L Köpke, C Kopper, S Kopper, DJ Koskinen, M Kowalski, M Krasberg, G Kroll, J Kunnen, N Kurahashi, T Kuwabara, M Labare, K Laihem, H Landsman, MJ Larson, R Lauer, M Lesiak-Bzdak, J Lünemann, J Madsen, R Maruyama, K Mase, HS Matis, F McNally, K Meagher, M Merck, P Mészáros, T Meures, S Miarecki, E Middell, N Milke, J Miller, L Mohrmann, T Montaruli, R Morse, SM Movit, R Nahnhauer, U Naumann, SC Nowicki, DR Nygren, A Obertacke, S Odrowski, A Olivas, M Olivo, A O'Murchadha, S Panknin, L Paul, JA Pepper, CPDL Heros, D Pieloth, N Pirk, J Posselt, PB Price, GT Przybylski, L Rädel, K Rawlins, P Redl, E Resconi, W Rhode, M Ribordy, M Richman, B Riedel, JP Rodrigues, F Rothmaier, C Rott, T Ruhe, B Ruzybayev, D Ryckbosch, SM Saba, T Salameh, HG Sander, M Santander, S Sarkar, K Schatto, M Scheel, F Scheriau, T Schmidt, M Schmitz, S Schoenen, S Schöneberg, L Schönherr, A Schönwald, A Schukraft, L Schulte, O Schulz, D Seckel, SH Seo, Y Sestayo, S Seunarine, MWE Smith, M Soiron, D Soldin, GM Spiczak, C Spiering, M Stamatikos, T Stanev, A Stasik, T Stezelberger, RG Stokstad, A Stößl, EA Strahler, R Ström, GW Sullivan, H Taavola, I Taboada, A Tamburro, S Ter-Antonyan, S Tilav, PA Toale, S Toscano, M Usner, DVD Drift, NV Eijndhoven, AV Overloop, JV Santen, M Vehring, M Voge, C Walck, T Waldenmaier, M Wallraff, M Walter, R Wasserman, C Weaver, C Wendt, S Westerhoff, N Whitehorn, K Wiebe, CH Wiebusch, DR Williams, H Wissing, M Wolf, TR Wood, K Woschnagg, C Xu, DL Xu, XW Xu, JP Yanez, G Yodh, S Yoshida, P Zarzhitsky, J Ziemann, A Zilles, M Zoll

We present the first results in the search for relativistic magnetic monopoles with the IceCube detector, a subsurface neutrino telescope located in the South Polar ice cap containing a volume of 1 km$^{3}$. This analysis searches data taken on the partially completed detector during 2007 when roughly 0.2 km$^{3}$ of ice was instrumented. The lack of candidate events leads to an upper limit on the flux of relativistic magnetic monopoles of $\Phi_{\mathrm{90%C.L.}}\sim 3\e{-18}\fluxunits$ for $\beta\geq0.8$. This is a factor of 4 improvement over the previous best experimental flux limits up to a Lorentz boost $\gamma$ below $10^{7}$. This result is then interpreted for a wide range of mass and kinetic energy values.


The ATLAS3D Project - XXIII. Angular momentum and nuclear surface brightness profiles

Monthly Notices of the Royal Astronomical Society 433 (2013) 2812-2839

D Krajnović, AM Karick, RL Davies, T Naab, M Sarzi, E Emsellem, M Cappellari, P Serra, PT de Zeeuw, N Scott, RM McDermid, A-M Weijmans, TA Davis, K Alatalo, L Blitz, M Bois, M Bureau, F Bournaud, A Crocker, P-A Duc, S Khochfar, H Kuntschner, R Morganti, T Oosterloo, LM Young

We investigate nuclear light profiles in 135 ATLAS3D galaxies for which the Hubble Space Telescope (HST) imaging is available and compare them to the large-scale kinematics obtained with the SAURONintegral-field spectrograph. Specific angular momentum, λR, correlateswith the shape of nuclear light profiles, where, as suggested by previous studies, cores are typically found in slow rotators and core-less galaxies are fast rotators. As also shown before, cores are found only in massive galaxies and only in systems with the stellar mass (measured via dynamical models) M ≳ 8 × 1010 M· Based on our sample, we, however, see no evidence for a bimodal distribution of nuclear slopes. The best predictor for finding a core is based on the stellar velocity dispersion within an effective radius, se, and specific angular momentum, where cores are found for λR ≲ 0.25 and σe ≳ 160 kms-1. We estimate that only about 10 per cent of nearby early-type galaxies contain cores. Furthermore, we show that there is a genuine population of fast rotators with cores. We also show that core fast rotators are morphologically, kinematically and dynamically different from core slow rotators. The cores of fast rotators, however, could harbour black holes of similar masses to those in core slow rotators, but typically more massive than those found in core-less fast rotators. Cores of both fast and slow rotators are made of old stars and found in galaxies typically lacking molecular or atomic gas (with a few exceptions). Core-less galaxies, and especially core-less fast rotators, are underluminous in the diffuse X-ray emission, but the presence of a core does not imply high X-ray luminosities. Additionally, we postulate (as many of these galaxies lack HST imaging) a possible population of core-less galaxies among slow rotators, which cannot be explained as face-on discs, but comprise a genuine sub-population of slow rotators. These galaxies are typically less massive and flatter than core slow rotators, and show evidence for dynamical cold structures and exponential photometric components. Based on our findings, major nondissipative (gas-poor) mergers together with black hole binary evolution may not be the only path for formation of cores in early-type galaxies. We discuss possible processes for formation of cores and their subsequent preservation. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Stream-orbit misalignment I: The dangers of orbit-fitting

ArXiv (2013)

JL Sanders, J Binney

Tidal streams don't, in general, delineate orbits. A stream-orbit misalignment is expected to lead to biases when using orbit-fitting to constrain models for the Galactic potential. In this first of two papers we discuss the expected magnitude of the misalignment and the resulting dangers of using orbit-fitting algorithms to constrain the potential. We summarize data for known streams which should prove useful for constraining the Galactic potential, and compute their actions in a realistic Galactic potential. We go on to discuss the formation of tidal streams in angle-action space, and explain why, in general, streams do not delineate orbits. The magnitude of the stream-orbit misalignment is quantified for a logarithmic potential and a multi-component Galactic potential. Specifically, we focus on the expected misalignment for the known streams. By introducing a two-parameter family of realistic Galactic potentials we demonstrate that assuming these streams delineate orbits can lead to order one errors in the halo flattening and halo-to-disc force ratio at the Sun. We present a discussion of the dependence of these results on the progenitor mass, and demonstrate that the misalignment is mass-independent for the range of masses of observed streams. Hence, orbit-fitting does not yield better constraints on the potential if one uses narrower, lower-mass streams.


Orbital-free density-functional theory simulations of the dynamic structure factor of warm dense aluminum

Physical Review Letters 111 (2013)

TG White, S Richardson, BJB Crowley, LK Pattison, JWO Harris, G Gregori

Here, we report orbital-free density-functional theory (OF DFT) molecular dynamics simulations of the dynamic ion structure factor of warm solid density aluminum at T=0.5 eV and T=5 eV. We validate the OF DFT method in the warm dense matter regime through comparison of the static and thermodynamic properties with the more complete Kohn-Sham DFT. This extension of OF DFT to dynamic properties indicates that previously used models based on classical molecular dynamics may be inadequate to capture fully the low frequency dynamics of the response function. © 2013 American Physical Society.


Analysing surveys of our Galaxy - II. Determining the potential

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 433 (2013) 1411-1424

PJ McMillan, JJ Binney


DIFFUSE INTERSTELLAR BAND AT 8620 angstrom IN RAVE: A NEW METHOD FOR DETECTING THE DIFFUSE INTERSTELLAR BAND IN SPECTRA OF COOL STAR

ASTROPHYSICAL JOURNAL 778 (2013) ARTN 86

J Kos, T Zwitter, EK Grebel, O Bienayme, J Binney, J Bland-Hawthorn, KC Freeman, BK Gibson, G Gilmore, G Kordopatis, JF Navarro, Q Parker, WA Reid, G Seabroke, A Siebert, A Siviero, M Steinmetz, F Watson, RFG Wyse


The ATLAS3D project - XV. Benchmark for early-type galaxies scaling relations from 260 dynamical models: Mass-to-light ratio, dark matter, fundamental plane and mass plane

Monthly Notices of the Royal Astronomical Society 432 (2013) 1709-1741

M Cappellari, N Scott, K Alatalo, L Blitz, M Bois, F Bournaud, M Bureau, AF Crocker, RL Davies, TA Davis, PT de Zeeuw, P-A Duc, E Emsellem, S Khochfar, D Krajnović, H Kuntschner, RM McDermid, R Morganti, T Naab, T Oosterloo, M Sarzi, P Serra, A-M Weijmans, LM Young

We study the volume-limited and nearly mass-selected (stellar mass Mstars ≳ 6 × 109 M⊙) ATLAS3D sample of 260 early-type galaxies (ETGs, ellipticals Es and lenticulars S0s). We construct detailed axisymmetric dynamical models (Jeans Anisotropic MGE), which allow for orbital anisotropy, include a dark matter halo and reproduce in detail both the galaxy images and the high-quality integral-field stellar kinematics out to about 1Re, the projected half-light radius. We derive accurate total mass-to-light ratios (M/L)e and dark matter fractions fDM, within a sphere of radius r = Re centred on the galaxies.We alsomeasure the stellar (M/L)stars and derive a median dark matter fraction fDM = 13 per cent in our sample. We infer masses MJAM = L × (M/L)e ≈ 2 ×M1/2, where M1/2 is the total mass within a sphere enclosing half of the galaxy light. We find that the thin two-dimensional subset spanned by galaxies in the (MJAM, σe,Rmaje ) coordinates system, which we call the Mass Plane (MP) has an observed rms scatter of 19 per cent, which implies an intrinsic one of 11 per cent. Here, Rmaje is the major axis of an isophote enclosing half of the observed galaxy light, while σe is measuredwithin that isophote. The MP satisfies the scalar virial relation MJAM ∝ σ2e Rmaje within our tight errors. This show that the larger scatter in the Fundamental Plane (FP) (L, σe, Re) is due to stellar population effects [including trends in the stellar initial mass function (IMF)]. It confirms that the FP deviation from the virial exponents is due to a genuine (M/L)e variation. However, the details of how both Re and σe are determined are critical in defining the precise deviation from the virial exponents. The main uncertainty in masses or M/L estimates using the scalar virial relation is in the measurement of Re. This problem is already relevant for nearby galaxies and may cause significant biases in virial mass and size determinations at high redshift. Dynamical models can eliminate these problems.We revisit the (M/L)e-σe relation, which describes most of the deviations between the MP and the FP. The best-fitting relation is (M/L)e ∝ σ0.72e (r band). It provides an upper limit to any systematic increase of the IMF mass normalization with σe. The correlation is more shallow and has smaller scatter for slow rotating systems or for galaxies in Virgo. For the latter, when using the best distance estimates, we observe a scatter in (M/L)e of 11 per cent, and infer an intrinsic one of 8 per cent. We perform an accurate empirical study of the link between se and the galaxies circular velocity Vcirc within 1Re (where stars dominate) and find the relation max (Vcirc) ≈ 1.76 × σe, which has an observed scatter of 7 per cent. The accurate parameters described in this paper are used in the companion Paper XX (Cappellari et al.) of this series to explore the variation of global galaxy properties, including the IMF, on the projections of the MP. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Diffusive shock acceleration at laser-driven shocks: Studying cosmic-ray accelerators in the laboratory

New Journal of Physics 15 (2013)

B Reville, AR Bell, G Gregori

The non-thermal particle spectra responsible for the emission from many astrophysical systems are thought to originate from shocks via a first order Fermi process otherwise known as diffusive shock acceleration. The same mechanism is also widely believed to be responsible for the production of high energy cosmic rays. With the growing interest in collisionless shock physics in laser produced plasmas, the possibility of reproducing and detecting shock acceleration in controlled laboratory experiments should be considered. The various experimental constraints that must be satisfied are reviewed. It is demonstrated that several currently operating laser facilities may fulfil the necessary criteria to confirm the occurrence of diffusive shock acceleration of electrons at laser produced shocks. Successful reproduction of Fermi acceleration in the laboratory could open a range of possibilities, providing insight into the complex plasma processes that occur near astrophysical sources of cosmic rays. © IOP Publishing and Deutsche Physikalische Gesellschaft.


The atlas3d project - xiv. the extent and kinematics of the molecular gas in early-type galaxies

Monthly Notices of the Royal Astronomical Society 429 (2013) 534-555

TA Davis, K Alatalo, M Bureau, M Cappellari, N Scott, LM Young, L Blitz, A Crocker, E Bayet, M Bois, F Bournaud, RL Davies, PT De Zeeuw, P Duc, E Emsellem, S Khochfar, D Krajnovíc, H Kuntschner, P Lablanche, RM McDermid, R Morganti, T Naab, T Oosterloo, M Sarzi, P Serra, A Weijmans

We use interferometric 12CO(1-0) observations to compare and contrast the extent, surface brightness profiles and kinematics of the molecular gas in CO-rich ATLAS3D early-type galaxies (ETGs) and spiral galaxies. We find that the molecular gas extent is smaller in absolute terms in ETGs than in late-type galaxies, but that the size distributions are similar once scaled by the galaxies optical/stellar characteristic scalelengths. Amongst ETGs, we find that the extent of the gas is independent of its kinematic misalignment (with respect to the stars), but does depend on the environment, with Virgo cluster ETGs having less extended molecular gas reservoirs, further emphasizing that cluster ETGs follow different evolutionary pathways from those in the field. Approximately half of ETGs have molecular gas surface brightness profiles that follow the stellar light profile. These systems often have relaxed gas out to large radii, suggesting they are unlikely to have had recent merger/accretion events. A third of the sample galaxies show molecular gas surface brightness profiles that fall off slower than the light, and sometimes show a truncation. These galaxies often have a low mass, and eitherhave disturbed molecular gas or are in the Virgo cluster, suggesting that recent mergers, ram pressure stripping and/or the presence of hot gas can compress/truncate the gas. The remaining galaxies have rings, or composite profiles, that we argue can be caused by the effects of bars. We investigated the kinematics of the molecular gas using position-velocity diagrams, and compared the observed kinematics with dynamical model predictions, and the observed stellar and ionized gas velocities. We confirm that the molecular gas reaches beyond the turnover of the circular velocity curve in~70 per cent of our CO-rich ATLAS3D ETGs, validating previous work on the CO Tully-Fisher relation. In general we find that in most galaxies the molecular gas is dynamically cold, and the observed CO rotation matches well model predictions of the circular velocity. In the galaxies with the largest molecular masses, dust obscuration and/or population gradients can cause model predictions of the circular velocity to disagree with observations of the molecular gas rotation; however, these effects are confined to the most star forming systems. Bars and non-equilibrium conditions can also make the gas deviate from circular orbits. In both these cases, one expects the model circular velocity to be higher than the observed CO velocity, in agreement with our observations. Molecular gas is a better direct tracer of the circular velocity than the ionized gas, justifying its use as a kinematic tracer for Tully-Fisher and similar analyses.


Cosmic-ray acceleration and escape from supernova remnants

Monthly Notices of the Royal Astronomical Society 431 (2013) 415-429

AR Bell, KM Schure, B Reville, G Giacinti

Galactic cosmic-ray (CR) acceleration to the knee in the spectrum at a few PeV is only possible if the magnetic field ahead of a supernova remnant (SNR) shock is strongly amplified by CRs escaping the SNR. A model formulated in terms of the electric charge carried by escaping CRs predicts the maximum CR energy and the energy spectrum of CRs released into the surrounding medium. We find that historical SNRs such as Cas A, Tycho and Kepler may be expanding too slowly to accelerate CRs to the knee at the present time. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.


The role of collisions on mode competition between the two-stream and Weibel instabilities

Journal of Plasma Physics 79 (2013) 987-989

KA Humphrey, DC Speirs, R Bingham, RMGM Trines, P Norreys

We present results from numerical simulations conducted to investigate a potential method for realizing the required fusion fuel heating in the fast ignition scheme to achieving inertial confinement fusion. A comparison will be made between collisionless and collisional particle-in-cell simulations of the relaxation of a non-thermal electron beam through the two-stream instability. The results presented demonstrate energy transfer to the plasma ion population from the laser-driven electron beam via the nonlinear wave-wave interaction associated with the two-stream instability. Evidence will also be provided for the effects of preferential damping of competing instabilities such as the Weibel mode found to be detrimental to the ion heating process. © Cambridge University Press 2013.


Correlations at large scales and the onset of turbulence in the fast solar WIND

Astrophysical Journal 778 (2013)

RT Wicks, DA Roberts, A Mallet, AA Schekochihin, TS Horbury, CHK Chen

We show that the scaling of structure functions of magnetic and velocity fields in a mostly highly Alfvénic fast solar wind stream depends strongly on the joint distribution of the dimensionless measures of cross helicity and residual energy. Already at very low frequencies, fluctuations that are both more balanced (cross helicity ∼0) and equipartitioned (residual energy ∼0) have steep structure functions reminiscent of "turbulent" scalings usually associated with the inertial range. Fluctuations that are magnetically dominated (residual energy ∼-1), and so have closely anti-aligned Elsasser-field vectors, or are imbalanced (cross helicity ∼1), and so have closely aligned magnetic and velocity vectors, have wide "1/f" ranges typical of fast solar wind. We conclude that the strength of nonlinear interactions of individual fluctuations within a stream, diagnosed by the degree of correlation in direction and magnitude of magnetic and velocity fluctuations, determines the extent of the 1/f region observed, and thus the onset scale for the turbulent cascade. © 2013. The American Astronomical Society. All rights reserved.