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Analysis of the Cleburne, Texas, Earthquake Sequence from June 2009 to June 2010
(2013-12) Justinic, Ashley Howe; Stump, Brian; Hayward, Chris; Frohlich, Cliff; Frohlich, Cliff
On 9 June 2009, an M-bLg 2.8 earthquake shook Cleburne, Texas, a community not known to have previously experienced earthquakes. Over 50 small earthquakes followed by the end of December 2009. A temporary network of four and then five IRIS-Passcal broadband systems was deployed from June 2009 to June 2010, recording data that were used to locate 38 events with the most confident P- and S-arrival picks. Event locations were distributed along a 2 km long north-northeast trend. The location centroid was at 32.298 degrees N, 97.372 degrees W and at 3.6 km depth. This location is approximately 1.3 km from a saltwater disposal well that began injection in October 2007 and 3.2 km away from a second injection well that was active from September 2005 to late July 2009. Focal mechanisms estimated for the best-recorded events suggest a north-northeast-south-southwest-trending normal fault with a dip of similar to 50 degrees and a component of oblique motion (rake of similar to-80 degrees). This average solution is generally consistent with the north-northeast-trending extensional faults that are prevalent across parts of Texas, Oklahoma, Louisiana, and Arkansas. Stress drops calculated from P and S spectra for seven different events ranged from 3.9 to 90 bars, with most estimates between 40 and 50 bars, typical values for intraplate earthquakes. Because there were no known previous earthquakes, and the located events were close to the two injection wells and near the injection depth, the possibility exists that earthquakes may be related to fluid injection.
Antibody-Independent Isolation of Circulating Tumor Cells by Continuous-Flow Dielectrophoresis
(2013-01) Shim, Sangjo; Stemke-Hale, Katherine; Tsimberidou, Apostolia M.; Noshari, Jamileh; Anderson, Thomas E.; Gascoyne, Peter R. C.; Shim, Sangjo; Noshari, Jamileh; Anderson, Thomas E.; Gascoyne, Peter R. C.
Circulating tumor cells (CTCs) are prognostic markers for the recurrence of cancer and may carry molecular information relevant to cancer diagnosis. Dielectrophoresis (DEP) has been proposed as a molecular marker-independent approach for isolating CTCs from blood and has been shown to be broadly applicable to different types of cancers. However, existing batch-mode microfluidic DEP methods have been unable to process 10 ml clinical blood specimens rapidly enough. To achieve the required processing rates of 106 nucleated cells/min, we describe a continuous flow microfluidic processing chamber into which the peripheral blood mononuclear cell fraction of a clinical specimen is slowly injected, deionized by diffusion, and then subjected to a balance of DEP, sedimentation and hydrodynamic lift forces. These forces cause tumor cells to be transported close to the floor of the chamber, while blood cells are carried about three cell diameters above them. The tumor cells are isolated by skimming them from the bottom of the chamber while the blood cells flow to waste. The principles, design, and modeling of the continuous-flow system are presented. To illustrate operation of the technology, we demonstrate the isolation of circulating colon tumor cells from clinical specimens and verify the tumor origin of these cells by molecular analysis. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4774304]
Beltrami state in black-hole accretion disk: A magnetofluid approach
(2015-12) Bhattacharjee, Chinmoy; Das, Rupam; Stark, David J.; Mahajan, S. M.; Bhattacharjee, Chinmoy; Stark, David J.; Mahajan, S. M.
Using the magnetofluid unification framework, we show that the accretion disk plasma (embedded in the background geometry of a black hole) can relax to a class of states known as the Beltrami-Bernoulli (BB) equilibria. Modeling the disk plasma as a Hall magnetohydrodynamics (MHD) system, we find that the space-time curvature can significantly alter the magnetic (velocity) decay rates as we move away from the compact object; the velocity profiles in BB states, for example, deviate substantially from the predicted corresponding geodesic velocity profiles. These departures imply a rich interplay of plasma dynamics and general relativity revealed by examining the corresponding Bernoulli condition representing "homogeneity" of total energy. The relaxed states have their origin in the constraints provided by the two helicity invariants of Hall MHD. These helicities conspire to introduce an oscillatory length scale into the system that is strongly influenced by relativistic and thermal effects.
Characteristics Of Planetary Candidates Observed By Kepler. II. Analysis Of The First Four Months Of Data
(2011-07) Borucki, William J.; Koch, David G.; Basri, Gibor; Batalha, Natalie; Brown, Timothy M.; Bryson, Stephen T.; Caldwell, Douglas; Christensen-Dalsgaard, Jorgen; Cochran, William D.; DeVore, Edna; Dunham, Edward W.; Gautier, Thomas N., III; Geary, John C.; Gilliland, Ronald; Gould, Alan; Howell, Steve B.; Jenkins, Jon M.; Latham, David W.; Lissauer, Jack J.; Marcy, Geoffrey W.; Rowe, Jason; Sasselov, Dimitar; Boss, Alan; Charbonneau, David; Ciardi, David; Doyle, Laurance; Dupree, Andrea K.; Ford, Eric B.; Fortney, Jonathan; Holman, Matthew J.; Seager, Sara; Steffen, Jason H.; Tarter, Jill; Welsh, William F.; Allen, Christopher; Buchhave, Lars A.; Christiansen, Jessie L.; Clarke, Bruce D.; Das, Santanu; Desert, Jean-Michel; Endl, Michael; Fabrycky, Daniel; Fressin, Francois; Haas, Michael; Horch, Elliott; Howard, Andrew; Isaacson, Howard; Kjeldsen, Hans; Kolodziejczak, Jeffery; Kulesa, Craig; Li, Jie; Lucas, Philip W.; Machalek, Pavel; McCarthy, Donald; MacQueen, Phillip; Meibom, Soren; Miquel, Thibaut; Prsa, Andrej; Quinn, Samuel N.; Quintana, Elisa V.; Ragozzine, Darin; Sherry, William; Shporer, Avi; Tenenbaum, Peter; Torres, Guillermo; Twicken, Joseph D.; Van Cleve, Jeffrey; Walkowicz, Lucianne; Witteborn, Fred C.; Still, Martin; Cochran, William D.; Endl, Michael
On 2011 February 1 the Kepler mission released data for 156,453 stars observed from the beginning of the science observations on 2009 May 2 through September 16. There are 1235 planetary candidates with transit-like signatures detected in this period. These are associated with 997 host stars. Distributions of the characteristics of the planetary candidates are separated into five class sizes: 68 candidates of approximately Earth-size (R-p < 1.25 R-circle plus), 288 super-Earth-size (1.25 R-circle plus <= R-p < 2 R-circle plus), 662 Neptune-size (2 R-circle plus <= R-p < 6 R-circle plus), 165 Jupiter-size (6 R-circle plus <= R-p < 15 R-circle plus), and 19 up to twice the size of Jupiter (15 R-circle plus <= R-p < 22 R-circle plus). In the temperature range appropriate for the habitable zone, 54 candidates are found with sizes ranging from Earth-size to larger than that of Jupiter. Six are less than twice the size of the Earth. Over 74% of the planetary candidates are smaller than Neptune. The observed number versus size distribution of planetary candidates increases to a peak at two to three times the Earth-size and then declines inversely proportional to the area of the candidate. Our current best estimates of the intrinsic frequencies of planetary candidates, after correcting for geometric and sensitivity biases, are 5% for Earth-size candidates, 8% for super-Earth-size candidates, 18% for Neptune-size candidates, 2% for Jupiter-size candidates, and 0.1% for very large candidates; a total of 0.34 candidates per star. Multi-candidate, transiting systems are frequent; 17% of the host stars have multi-candidate systems, and 34% of all the candidates are part of multi-candidate systems.
Discovery of the Transiting Planet Kepler-5B
(2010-04) Koch, David G.; Borucki, William J.; Rowe, Jason F.; Batalha, Natalie M.; Brown, Timothy M.; Caldwell, Douglas A.; Caldwell, John; Cochran, William D.; DeVore, Edna; Dunham, Edward W.; Dupree, Andrea K.; Gautier, Thomas N., III; Geary, John C.; Gilliland, Ron L.; Howell, Steve B.; Jenkins, Jon M.; Latham, David W.; Lissauer, Jack J.; Marcy, Geoff W.; Morrison, David; Tarter, Jill; Cochran, William D.
We present 44 days of high duty cycle, ultra precise photometry of the 13th magnitude star Kepler-5 (KIC 8191672, T(eff) = 6300 K, log g = 4.1), which exhibits periodic transits with a depth of 0.7%. Detailed modeling of the transit is consistent with a planetary companion with an orbital period of 3.548460 +/- 0.000032 days and a radius of 1.431(-0.052)(+0.041) R(J). Follow-up radial velocity measurements with the Keck HIRES spectrograph on nine separate nights demonstrate that the planet is more than twice as massive as Jupiter with a mass of 2.114(-0.059)(+0.056) M(J) and a mean density of 0.894 +/- 0.079 g cm(-3).
Finding Ultracool Brown Dwarfs With MegaCam On CFHT: Method And First Results
(2008-06) Delorme, P.; Willott, C. J.; Forveille, T.; Delfosse, X.; Reyle, C.; Bertin, E.; Albert, L.; Artigau, E.; Robin, A. C.; Allard, F.; Doyon, R.; Hill, G. J.; Hill, G. J.
Aims. We present the first results of a wide field survey for cool brown dwarfs with the MegaCam camera on the CFHT telescope, the Canada-France Brown Dwarf Survey, hereafter CFBDS. Our objectives are to find ultracool brown dwarfs and to constrain the field-brown dwarf mass function thanks to a larger sample of L and T dwarfs. Methods. We identify candidates in CFHT/MegaCam i' and z' images using optimised psf-fitting within Source Extractor, and follow them up with pointed near-infrared imaging on several telescopes. Results. We have so far analysed over 350 square degrees and found 770 brown dwarf candidates brighter than z'(AB) = 22.5. We currently have J-band photometry for 220 of these candidates, which confirms 37% as potential L or T dwarfs. Some are among the reddest and farthest brown dwarfs currently known, including an independent identification of the recently published ULAS J003402.77-005206.7 and the discovery of a second brown dwarf later than T8, CFBDS J005910.83-011401.3. Infrared spectra of three T dwarf candidates confirm their nature, and validate the selection process. Conclusions. The completed survey will discover similar to 100 T dwarfs and similar to 500 L dwarfs or M dwarfs later than M8, approximately doubling the number of currently known brown dwarfs. The resulting sample will have a very well-defined selection function, and will therefore produce a very clean luminosity function.
GEMS : Galaxy Fitting Catalogs and Testing Parametric Galaxy Fitting Codes : GALFIT and GIM2D
(2007-10) Haeussler, Boris; McIntosh, Daniel H.; Barden, Marco; Bell, Eric F.; Rix, Hans-Walter; Borch, Andrea; Beckwith, Steven V. W.; Caldwell, John A. R.; Heymans, Catherine; Jahnke, Knud; Jogee, Shardha; Koposov, Sergey E.; Meisenheimer, Klaus; Sanchez, Sebastian F.; Somerville, Rachel S.; Wisotzki, Lutz; Wolf, Christian; Caldwell, John A. R.
In the context of measuring the structures of intermediate-redshift galaxies with HST ACS surveys, we tune, test, and compare two widely used fitting codes (GALFIT and GIM2D) for fitting single-component Sersic models to both simulated and real galaxy data. Our study focuses on the GEMS survey with the sensitivity of typical HST survey data, and we include our final catalog of fit results for all 41,495 objects detected in GEMS. Using simulations, we find that fitting accuracy depends sensitively on galaxy profile shape. Exponential disks are well fit and have small measurement errors, whereas fits to de Vaucouleurs profiles show larger uncertainties owing to the large amount of light at large radii. Both codes provide reliable fits with little systematic error for galaxies with effective surface brightnesses brighter than that of the sky; the formal uncertainties returned by these codes significantly underestimate the true uncertainties (as estimated using the simulations). We find that GIM2D suffers significant systematic errors for spheroids with close companions owing to the difficulty of effectively masking out neighboring galaxy light; there appears to be no work-around to this important systematic in GIM2D's current implementation. While this crowding error affects only a small fraction of galaxies in GEMS, it must be accounted for in the analysis of deeper cosmological images or of more crowded fields with GIM2D. In contrast, GALFIT results are robust to the presence of neighbors because it can simultaneously fit the profiles of multiple companions as well as the galaxy of interest. We find GALFIT's robustness to nearby companions and factor of greater than or similar to 20 faster runtime speed are important advantages over GIM2D for analyzing large HST ACS data sets.
The HETDEX Pilot Survey. IV. The Evolution Of O II Emitting Galaxies From Z Similar To 0.5 To Z Similar To 0
(2013-05) Ciardullo, Robin; Gronwall, Caryl; Adams, Joshua J.; Blanc, Guillermo A.; Gebhardt, Karl; Finkelstein, Steven L.; Jogee, Shardha; Hill, Gary J.; Drory, Niv; Hopp, Ulrich; Schneider, Donald P.; Zeimann, Gregory R.; Dalton, Gavin B.; Adams, Joshua J.; Blanc, Guillermo A.; Gebhardt, Karl; Finkelstein, Steven L.; Jogee, Shardha
We present an analysis of the luminosities and equivalent widths of the 284 z < 0.56 [O II]-emitting galaxies found in the 169 arcmin(2) pilot survey for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). By combining emission-line fluxes obtained from the Mitchell spectrograph on the McDonald 2.7 m telescope with deep broadband photometry from archival data, we derive each galaxy's dereddened [O II] lambda 3727 luminosity and calculate its total star formation rate. We show that over the last similar to 5Gyr of cosmic time, there has been substantial evolution in the [O II] emission-line luminosity function, with L* decreasing by similar to 0.6 +/- 0.2 dex in the observed function, and by similar to 0.9 +/- 0.2 dex in the dereddened relation. Accompanying this decline is a significant shift in the distribution of [O II] equivalent widths, with the fraction of high equivalent-width emitters declining dramatically with time. Overall, the data imply that the relative intensity of star formation within galaxies has decreased over the past similar to 5Gyr, and that the star formation rate density of the universe has declined by a factor of similar to 2.5 between z similar to 0.5 and z similar to 0. These observations represent the first [O II]-based star formation rate density measurements in this redshift range, and foreshadow the advancements which will be generated by the main HETDEX survey.
High Angular Resolution Imaging And Infrared Spectroscopy Of CoRoT Candidates
(2013-08) Guenther, E. W.; Fridlund, M.; Alonso, R.; Carpano, S.; Deeg, H. J.; Deleuil, M.; Dreizler, S.; Endl, M.; Gandolfi, D.; Gillon, M.; Guillot, T.; Jehin, E.; Leger, A.; Moutou, C.; Nortmann, L.; Rouan, D.; Samuel, B.; Schneider, J.; Tingley, B.; Endl, M.
Context. Studies of transiting extrasolar planets are of key importance for understanding the nature of planets outside our solar system because their masses, diameters, and bulk densities can be measured. An important part of transit-search programmes is the removal of false-positives. In the case of the CoRoT space mission, the majority of the false-positives are removed by a detailed analysis of the light curves and by seeing-limited imaging in- and out-of-transit. However, the critical question is how many of the candidates that passed all these tests are false-positives. Such false-positives can be caused by eclipsing binaries, which are either related or unrelated to the targets. Aims. For our study we selected 25 CoRoT candidates that have already been screened against false-positives using detailed analysis of the light curves and seeing-limited imaging, which has transits that are between 0.7 and 0.05% deep. Our aim is to search for companion candidates that had not been recognized in previous observations. Methods. We observed 20 candidates with the adaptive optics imager NaCo and 18 with the high-resolution infrared spectrograph CRIRES. Results. We found previously unknown stars within 2 0 0 of the targets in seven of the candidates. All of these are too faint and too close to the targets to have been previously detected with seeing-limited telescopes in the optical. Our study thus leads to the surprising results that if we remove all candidates excluded by the sophisticated analysis of the light-curve, as well as carrying out deep imaging with seeing-limited telescopes, still 28 35% of the remaining candidates are found to possess companions that are bright enough to be false-positives. Conclusions. Given that the companion candidates cluster around the targets and that the J - K colours are consistent with physical companions, we conclude that the companion candidates are more likely to be physical companions rather than unrelated field stars.
Internal wave pressure, velocity, and energy flux from density perturbations
(2016-05) Allshouse, Michael R.; Lee, Frank M.; Morrison, Philip J.; Swinney, Harry L.; Allshouse, Michael R.; Lee, Frank M.; Morrison, Philip J.; Swinney, Harry L.
Determination of energy transport is crucial for understanding the energy budget and fluid circulation in density varying fluids such as the ocean and the atmosphere. However, it is rarely possible to determine the energy flux field J = pu, which requires simultaneous measurements of the pressure and velocity perturbation fields p and u, respectively. We present a method for obtaining the instantaneous J(x, z, t) from density perturbations alone: A Green's function-based calculation yields p; u is obtained by integrating the continuity equation and the incompressibility condition. We validate our method with results from Navier-Stokes simulations: The Green's function method is applied to the density perturbation field from the simulations and the result for J is found to agree typically to within 1% with J computed directly using p and u from the Navier-Stokes simulation. We also apply the Green's function method to density perturbation data from laboratory schlieren measurements of internal waves in a stratified fluid and the result for J agrees to within 6% with results from Navier-Stokes simulations. Our method for determining the instantaneous velocity, pressure, and energy flux fields applies to any system described by a linear approximation of the density perturbation field, e.g., to small-amplitude lee waves and propagating vertical modes. The method can be applied using our MATLAB graphical user interface EnergyFlux.
Interspecific Dominance Via Vocal Interactions Mediates Altitudinal Zonation In Neotropical Singing Mice
(2013-11) Pasch, Bret; Bolker, Benjamin M.; Phelps, Steven M.; Pasch, Bret; Phelps, Steven M.
Interspecific aggression between ecologically similar species may influence geographic limits by mediating competitive exclusion at the range edge. Advertisement signals that mediate competitive interactions within species may also provide social information that contributes to behavioral dominance and spatial segregation among species. We studied the mechanisms underlying altitudinal range limits in Neotropical singing mice (Scotinomys), a genus of muroid rodent in which males vocalize to repel rivals and attract mates. We first delineated replacement zones and described temperature regimes on three mountains in Costa Rica and Panama where Chiriquii singing mice (S. xerampelinus) abruptly replace Alston''s singing mice (S. teguina). Next, we conducted interspecific behavioral trials and reciprocal removal experiments to examine if interspecific aggression mediated species replacement. Finally, we performed reciprocal playback experiments to investigate whether response to song matched competitive interactions. Behavioral trials and removal experiments suggest that S. xerampelinus is behaviorally dominant and excludes S. teguina from higher, cooler altitudes. Playback experiments indicate that subordinate S. teguina is silenced and repelled by heterospecific song, whereas S. xerampelinus responded to heterospecifics with approach and song rates comparable to responses to conspecifics. Thus, interspecific communication reflects underlying dominance and suggests that acoustic signaling contributes to altitudinal zonation of ecologically similar congeners. Our findings implicate the use of social information in structuring spatial distributions of animal communities across landscapes and provide insight into how large-scale patterns are generated by individual interactions.
Letter to James E. Allen from Marguerite M. Hanchey on 1968-11-14
(1968-11-14) Hanchey, Marguerite M.
O III Emission And Gas Kinematics In A Lyman-Alpha Blob At Z Similar To 3.1
(2013-04) McLinden, Emily M.; Malhotra, Sangeeta; Rhoads, James E.; Hibon, Pascale; Weijmans, Anne-Marie; Tilvi, Vithal; McLinden, Emily M.
We present spectroscopic measurements of the [O III] emission line from two subregions of strong Ly alpha emission in a radio-quiet Lyman-alpha blob (LAB). The blob under study is LAB1 at z similar to 3.1, and the [OIII] detections are from the two Lyman break galaxies (LBGs) embedded in the blob halo. The [OIII] measurements were made with LUCIFER on the 8.4 m Large Binocular Telescope and NIRSPEC on 10 m Keck Telescope. Comparing the redshift of the [OIII] measurements to Ly alpha redshifts from SAURON allows us to take a step toward understanding the kinematics of the gas in the blob. Using both LUCIFER and NIRSPEC we find velocity offsets between the [OIII] and Lya redshifts that are modestly negative or consistent with 0 km s(-1) in both subregions studied (ranging from -72+/-42-+6+/-33 km s(-1)). A negative offset means Ly alpha is blueshifted with respect to [O III] a positive offset then implies Lya is redshifted with respect to [O III]. These results may imply that outflows are not primarily responsible for Lyman alpha escape in this LAB, since outflows are generally expected to produce a positive velocity offset. In addition, we present an [O III] line flux upper limit on a third region of LAB1, a region that is unassociated with any underlying galaxy. We find that the [OIII] upper limit from the galaxy-unassociated region of the blob is at least 1.4-2.5 times fainter than the [OIII] flux from one of the LBG-associated regions and has an [O III] to Ly alpha ratio measured at least 1.9-3.4 times smaller than the same ratio measured from one of the LBGs.
Physical And Morphological Properties Of O II Emitting Galaxies In The HETDEX Pilot Survey
(2015-02) Bridge, Joanna S.; Gronwall, Caryl; Ciardullo, Robin; Hagen, Alex; Zeimann, Greg; Malz, A. I.; Acquaviva, Viviana; Schneider, Donald P.; Drory, Niv; Gebhardt, Karl; Jogee, Shardha; Drory, Niv; Gebhardt, Karl; Jogee, Shardha
The Hobby-Eberly Dark Energy Experiment pilot survey identified 284 [O II] lambda 3727 emitting galaxies in a 169 arcmin(2) field of sky in the redshift range 0 < z < 0.57. This line flux limited sample provides a bridge between studies in the local universe and higher-redshift [O II] surveys. We present an analysis of the star formation rates (SFRs) of these galaxies as a function of stellar mass as determined via spectral energy distribution fitting. The [O II] emitters fall on the "main sequence" of star-forming galaxies with SFR decreasing at lower masses and redshifts. However, the slope of our relation is flatter than that found for most other samples, a result of the metallicity dependence of the [O II] star formation rate indicator. The mass-specific SFR is higher for lower mass objects, supporting the idea that massive galaxies formed more quickly and efficiently than their lower mass counterparts. This is confirmed by the fact that the equivalent widths of the [O II] emission lines trend smaller with larger stellar mass. Examination of the morphologies of the [O II] emitters reveals that their star formation is not a result of mergers, and the galaxies' half-light radii do not indicate evolution of physical sizes.
Self-modulation of nonlinear waves in a weakly magnetized relativistic electron-positron plasma with temperature
(2012-04) Asenjo, Felipe A.; Borotto, Felix A.; Chian, Abraham C. L.; Munoz, Victor; Valdivia, J. Alejandro; Rempel, Erico L.; Asenjo, Felipe A.
We develop a nonlinear theory for self-modulation of a circularly polarized electromagnetic wave in a relativistic hot weakly magnetized electron-positron plasma. The case of parallel propagation along an ambient magnetic field is considered. A nonlinear Schrodinger equation is derived for the complex wave amplitude of a self-modulated wave packet. We show that the maximum growth rate of the modulational instability decreases as the temperature of the pair plasma increases. Depending on the initial conditions, the unstable wave envelope can evolve nonlinearly to either periodic wave trains or solitary waves. This theory has application to high-energy astrophysics and high-power laser physics.
The Seventh Data Release of the Sloan Digital Sky Survey
(2009-05) Abazajian, Kevork N.; Adelman-McCarthy, Jennifer K.; Agueros, Marcel A.; Allam, Sahar S.; Prieto, Carlos Allende; An, Deokkeun; Anderson, Kurt S. J.; Anderson, Scott F.; Annis, James; Bahcall, Neta A.; Bailer-Jones, C. A. L.; Barentine, J. C.; Bassett, Bruce A.; Becker, Andrew C.; Beers, Timothy C.; Bell, Eric F.; Belokurov, Vasily; Berlind, Andreas A.; Berman, Eileen F.; Bernardi, Mariangela; Bickerton, Steven J.; Bizyaev, Dmitry; Blakeslee, John P.; Blanton, Michael R.; Bochanski, John J.; Boroski, William N.; Brewington, Howard J.; Brinchmann, Jarle; Brinkmann, J.; Brunner, Robert J.; Budavari, Tamas; Carey, Larry N.; Carliles, Samuel; Carr, Michael A.; Castander, Francisco J.; Cinabro, David; Connolly, A. J.; Csabai, Istvan; Cunha, Carlos E.; Czarapata, Paul C.; Davenport, James R. A.; de Haas, Ernst; Dilday, Ben; Doi, Mamoru; Eisenstein, Daniel J.; Evans, Michael L.; Evans, N. W.; Fan, Xiaohui; Friedman, Scott D.; Frieman, Joshua A.; Fukugita, Masataka; Gansicke, Boris T.; Gates, Evalyn; Gillespie, Bruce; Gilmore, G.; Gonzalez, Belinda; Gonzalez, Carlos F.; Grebel, Eva K.; Gunn, James E.; Gyory, Zsuzsanna; Hall, Patrick B.; Harding, Paul; Harris, Frederick H.; Harvanek, Michael; Hawley, Suzanne L.; Hayes, Jeffrey J. E.; Heckman, Timothy M.; Hendry, John S.; Hennessy, Gregory S.; Hindsley, Robert B.; Hoblitt, J.; Hogan, Craig J.; Hogg, David W.; Holtzman, Jon A.; Hyde, Joseph B.; Ichikawa, Shin-ichi; Ichikawa, Takashi; Im, Myungshin; Ivezic, Zeljko; Jester, Sebastian; Jiang, Linhua; Johnson, Jennifer A.; Jorgensen, Anders M.; Juric, Mario; Kent, Stephen M.; Kessler, R.; Kleinman, S. J.; Knapp, G. R.; Konishi, Kohki; Kron, Richard G.; Krzesinski, Jurek; Kuropatkin, Nikolay; Lampeitl, Hubert; Lebedeva, Svetlana; Lee, Myung Gyoon; Lee, Young Sun; Leger, R.French; Lepine, Sebastien; Li, Nolan; Lima, Marcos; Lin, Huan; Long, Daniel C.; Loomis, Craig P.; Loveday, Jon; Lupton, Robert H.; Magnier, Eugene; Malanushenko, Olena; Malanushenko, Viktor; Mandelbaum, Rachel; Margon, Bruce; Marriner, John P.; Martinez-Delgado, David; Matsubara, Takahiko; McGehee, Peregrine M.; McKay, Timothy A.; Meiksin, Avery; Morrison, Heather L.; Mullally, Fergal; Munn, Jeffrey A.; Murphy, Tara; Nash, Thomas; Nebot, Ada; Neilsen, Eric H., Jr.; Newberg, Heidi Jo; Newman, Peter R.; Nichol, Robert C.; Nicinski, Tom; Nieto-Santisteban, Maria; Nitta, Atsuko; Okamura, Sadanori; Oravetz, Daniel J.; Ostriker, Jeremiah P.; Owen, Russell; Padmanabhan, Nikhil; Pan, Kaike; Park, Changbom; Pauls, George; Peoples, John, Jr.; Percival, Will J.; Pier, Jeffrey R.; Pope, Adrian C.; Pourbaix, Dimitri; Price, Paul A.; Purger, Norbert; Quinn, Thomas; Raddick, M. Jordan; Fiorentin, Paola Re; Richards, Gordon T.; Richmond, Michael W.; Riess, Adam G.; Rix, Hans-Walter; Rockosi, Constance M.; Sako, Masao; Schlegel, David J.; Schneider, Donald P.; Scholz, Ralf-Dieter; Schreiber, Matthias R.; Schwope, Axel D.; Seljak, Uros; Sesar, Branimir; Sheldon, Erin; Shimasaku, Kazu; Sibley, Valena C.; Simmons, A. E.; Sivarani, Thirupathi; Smith, J. Allyn; Smith, Martin C.; Smolcic, Vernesa; Snedden, Stephanie A.; Stebbins, Albert; Steinmetz, Matthias; Stoughton, Chris; Strauss, Michael A.; SubbaRao, Mark; Suto, Yasushi; Szalay, Alexander S.; Szapudi, Istvan; Szkody, Paula; Tanaka, Masayuki; Tegmark, Max; Teodoro, Luis F. A.; Thakar, Aniruddha R.; Tremonti, Christy A.; Tucker, Douglas L.; Uomoto, Alan; Vanden Berk, Daniel E.; Vandenberg, Jan; Vidrih, S.; Vogeley, Michael S.; Voges, Wolfgang; Vogt, Nicole P.; Wadadekar, Yogesh; Watters, Shannon; Weinberg, David H.; West, Andrew A.; White, Simon D. M.; Wilhite, Brian C.; Wonders, Alainna C.; Yanny, Brian; Yocum, D. R.; York, Donald G.; Zehavi, Idit; Zibetti, Stefano; Zucker, Daniel B.; Barentine, J. C.
This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11,663 deg(2) of imaging data, with most of the similar to 2000 deg(2) increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry on a 120 degrees long, 2 degrees.5 wide stripe along the celestial equator in the Southern Galactic Cap, with some regions covered by as many as 90 individual imaging runs. We include a co-addition of the best of these data, going roughly 2 mag fainter than the main survey over 250 deg(2). The survey has completed spectroscopy over 9380 deg(2); the spectroscopy is now complete over a large contiguous area of the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog, reducing the rms statistical errors at the bright end to 45 milliarcseconds per coordinate. We further quantify a systematic error in bright galaxy photometry due to poor sky determination; this problem is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.
A Unique Star in the Outer Halo of the Milky Way
(2009-05) Lai, David K.; Rockosi, Constance M.; Bolte, Michael; Johnson, Jennifer A.; Beers, Timothy C.; Lee, Young Sun; Prieto, Carlos Allende; Yanny, Brian; Prieto, Carlos Allende
As part of a program to measure abundance ratios in stars beyond 15 kpc from the Galactic center, we have discovered a metal-poor star in the outer halo with a unique chemical signature. We originally identified it in the Sloan Extension for Galactic Understanding and Exploration survey as a distant metal-poor star. We obtained a follow-up spectrum using the Echelle Spectrometer and Imager at the Keck 2 telescope, and measure [Fe/H] = -3.17, [Mg/Fe]= -0.10, and [Ca/Fe] = +1.11. This is one of the largest over-abundances of Ca measured in any star to date; the extremely low value of [Mg/Ca] = -1.21 is entirely unique. To have found such an unusual star in our small sample of 27 targets suggests that there may be previously unobserved classes of stars yet to be found in situ in the Galactic halo.
Variability At The Edge: Optical Near/IR Rapid-Cadence Monitoring Of Newly Outbursting FU Orionis Object HBC 722
(2013-02) Green, Joel D.; Robertson, Paul; Baek, Giseon; Pooley, David; Pak, Soojong; Im, Myungshin; Lee, Jeong-Eun; Jeon, Yiseul; Choi, Changsu; Meschiari, Stefano; Green, Joel D.; Robertson, Paul; Meschiari, Stefano
We present the detection of day-timescale periodic variability in the r-band lightcurve of newly outbursting FU Orionis-type object HBC 722, taken from >42 nights of observation with the CQUEAN instrument on the McDonald Observatory 2.1 m telescope. The optical/near-IR lightcurve of HBC 722 shows a complex array of periodic variability, clustering around 5.8-day (0.044 mag amplitude) and 1.28-day (0.016 mag amplitude) periods, after removal of overall baseline variation. We attribute the unusual number of comparable strength signals to a phenomenon related to the temporary increase in accretion rate associated with FUors. We consider semi-random "flickering," magnetic braking/field compression and rotational asymmetries in the disk instability region as potential sources of variability. Assuming that the 5.8-day period is due to stellar rotation and the 1.28-day period is indicative of Keplerian rotation at the inner radius of the accretion disk (at 2 R-star), we derive a B-field strength of 2.2-2.7 kG, slightly larger than typical T Tauri stars. If instead the 5.8-day signal is from a disk asymmetry, the instability region has an outer radius of 5.4 R-star, consistent with models of FUor disks. Further exploration of the time domain in this complicated source and related objects will be key to understanding accretion processes.