Recursos de colección

Caltech Authors (144.724 recursos)

Repository of works by Caltech published authors.

Group = Space Astrophysics Laboratory

Mostrando recursos 1 - 20 de 151

  1. Broadband UBVR_CI_C photometry of horizontal-branch and metal-poor candidates from the HK and Hamburg/ESO surveys. I

    Beers, Timothy C.; Flynn, Chris; Rossi, Silvia; Sommer-Larsen, Jesper; Wilhelm, Ronald; Marsteller, Brian; Lee, Young Sun; De Lee, Nathan; Krugler, Julie; Deliyannis, Constantine P.; Simmons, Andrew T.; Mills, Elisabeth; Zickgraf, Franz-Josef; Holmberg, Johan; Önehag, Anna; Eriksson, Anders; Terndrup, Donald M.; Salim, Samir; Andersen, Johannes; Nordström, Birgitta; Frebel, Anna; Rhee, Jaehyon
    We report broadband UBV and/or BVR_CI_C CCD photometry for a total of 1857 stars in the thick-disk and halo populations of the Galaxy. The majority of our targets were selected as candidate field horizontal-branch or other A-type stars (FHB/A, N = 576), or candidate low-metallicity stars (N = 1221), from the HK and Hamburg/ESO objective-prism surveys. Similar data for a small number of additional stars from other samples are also reported. These data are being used for several purposes. In the case of the FHB/A candidates they are used to accurately separate the lower gravity FHB stars from various higher...

  2. The FIREBall fiber-fed UV spectrograph

    Tuttle, Sarah E.; Schiminovich, David; Milliard, Bruno; Grange, Robert; Martin, D. Christopher; Rahman, Shahinur; Deharveng, Jean-Michel; McLean, Ryan; Tajiri, Gordon; Matuszewski, M.
    FIREBall (Faint Intergalactic Redshifted Emission Balloon) had a successful first engineering flight in July of 2007 from Palestine, Texas. Here we detail the design and construction of the spectrograph. FIREBall consists of a 1m telescope coupled to a fiber-fed ultraviolet spectrograph flown on a short duration balloon. The spectrograph is designed to map hydrogen and metal line emission from the intergalactic medium at several redshifts below z=1, exploiting a small window in atmospheric oxygen absorption at balloon altitudes. The instrument is a wide-field IFU fed by almost 400 fibers. The Offner mount spectrograph is designed to be sensitive in the...

  3. Nonadiabatic quantum phase transition in a trapped spinor condensate

    Świsłocki, Tomasz; Witkowska, Emilia; Matuszewski, Michał
    We study the effect of an external harmonic trapping potential on an outcome of the nonadiabatic quantum phase transition from an antiferromagnetic to a phase-separated state in a spin-1 atomic condensate. Previously, we demonstrated that the dynamics of an untrapped system exhibits double universality with two different scaling laws appearing due to the conservation of magnetization. We show that in the presence of a trap, double universality persists. However, the corresponding scaling exponents are strongly modified by the transfer of local magnetization across the system. The values of these exponents cannot be explained by the effect of causality alone, as...

  4. Phase ordering kinetics of a nonequilibrium exciton-polariton condensate

    Kulczykowski, Michał; Matuszewski, Michał
    We investigate the process of coarsening via annihilation of vortex-antivortex pairs, following the quench to the condensate phase in a nonresonantly pumped polariton system. We find that the late-time dynamics is an example of universal phase-ordering kinetics, characterized by scaling of correlation functions in time. Depending on the parameters of the system, the evolution of the characteristic length scale L(t) can be the same as for the two-dimensional XY model, described by a power law with the dynamical exponent z≈2 and a logarithmic correction, or z≈1 which agrees with previous studies of conservative superfluids.

  5. Interactive optomechanical coupling with nonlinear polaritonic systems

    Bobrovska, N.; Matuszewski, M.; Liew, T. C. H.; Kyriienko, O.
    We study a system of interacting matter quasiparticles strongly coupled to photons inside an optomechanical cavity. The resulting normal modes of the system are represented by hybrid polaritonic quasiparticles, which acquire effective nonlinearity. Its strength is influenced by the presence of a mechanical mode and depends on the resonance frequency of the cavity. This leads to an interactive type of optomechanical coupling, which is distinct from previously studied dispersive and dissipative couplings in optomechanical systems. The emergent interactive coupling is shown to generate effective optical nonlinearity terms of high order, which are quartic in the polariton number. We consider particular...

  6. Angular dependence of giant Zeeman effect for semimagnetic cavity polariton

    Mirek, R; Król, M.; Lekenta, K.; Rousset, J.-G.; Nawrocki, M.; Kulczykowski, M.; Matuszewski, M.; Szczytko, J.; Pacuski, W.; Piętka, B.
    The observation of spin-related phenomena of microcavity polaritons has been limited due to the weak Zeeman effect of nonmagnetic semiconductors. We demonstrate that the incorporation of magnetic ions into quantum wells placed in a nonmagnetic microcavity results in enhanced effects of magnetic field on exciton-polaritons. We show that in such a structure the Zeeman splitting of exciton-polaritons strongly depends on the photon-exciton detuning and polariton wave vector. Our experimental data are explained by a model where the impact of magnetic field on the lower polariton state is directly inherited from the excitonic component, and the coupling strength to the cavity...

  7. Discovery of an Enormous Lyα Nebula in a Massive Galaxy Overdensity at z = 2.3

    Cai, Zheng; Fan, Xiaohui; Yang, Yujin; Bian, Fuyan; Prochaska, J. Xavier; Zabludoff, Ann; McGreer, Ian; Zheng, Zhen-Ya; Greenberg, Richard; Cantalupo, Sebastiano; Frye, Brenda; Hamden, Erika; Jiang, Linhua; Kashikawa, Nobunari; Wang, Ran
    Enormous Lyα nebulae (ELANe), unique tracers of galaxy density peaks, are predicted to lie at the nodes and intersections of cosmic filamentary structures. Previous successful searches for ELANe have focused on wide-field narrowband surveys or have targeted known sources such as ultraluminous quasi-stellar objects (QSOs) or radio galaxies. Utilizing groups of coherently strong Lyα absorptions, we have developed a new method to identify high-redshift galaxy overdensities and have identified an extremely massive overdensity, BOSS1441, at z = 2-3. In its density peak, we discover an ELAN that is associated with a relatively faint continuum. To date, this object has the...

  8. Fireball Multi Object Spectrograph: As-built optic performances

    Grange, R.; Milliard, B.; Lemaitre, G.; Quiret, S.; Hamden, E.; Schiminovich, D.
    Fireball (Faint Intergalactic Redshifted Emission Balloon) is a NASA/CNES balloon-borne experiment to study the faint diffuse circumgalactic medium from the line emissions in the ultraviolet (200 nm) above 37 km flight altitude. Fireball relies on a Multi Object Spectrograph (MOS) that takes full advantage of the new high QE, low noise 13 μm pixels UV EMCCD. The MOS is fed by a 1 meter diameter parabola with an extended field (1000 arcmin2) using a highly aspherized two mirror corrector. All the optical train is working at F/2.5 to maintain a high signal to noise ratio. The spectrograph (R~ 2200 and...

  9. The faint intergalactic-medium red-shifted emission balloon: future UV observations with EMCCDs

    Kyne, Gillian; Hamden, Erika T.; Lingner, Nicole; Morrissey, Patrick; Nikzad, Shouleh; Martin, D. Christopher
    We present the latest developments in our joint NASA/CNES suborbital project. This project is a balloon-borne UV multi-object spectrograph, which has been designed to detect faint emission from the circumgalactic medium (CGM) around low redshift galaxies. One major change from FIREBall-1 has been the use of a delta-doped Electron Multiplying CCD (EMCCD). EMCCDs can be used in photon-counting (PC) mode to achieve extremely low readout noise (¡ 1e-). Our testing initially focused on reducing clock-induced-charge (CIC) through wave shaping and well depth optimisation with the CCD Controller for Counting Photons (CCCP) from Nüvü. This optimisation also includes methods for reducing...

  10. FIREBALL: the Faint Intergalactic medium Redshifted Emission Balloon: overview and first science flight results

    Milliard, Bruno; Martin, D. Christopher; Schiminovich, David; Evrard, Jean; Matuszewski, Matt; Rahman, Shahinur; Tuttle, Sarah; McLean, Ryan; Deharveng, Jean-Michel; Mirc, Frederi; Grange, Robert; Chave, Robert
    FIREBALL (the Faint Intergalactic Redshifted Emission Balloon) is a balloon-borne 1m telescope coupled to an ultraviolet fiber-fed spectrograph. FIREBALL is designed to study the faint and diffuse emission of the intergalactic medium, until now detected primarily in absorption. FIREBALL is a path finding mission to test new technology and make new constraints on the temperature and density of this gas. We report on the first successful science flight of FIREBALL, in June 2009, which proved every aspect of the complex instrument performance, and provided the strongest measurements and constraints on IGM emission available from any instrument.

  11. FIREBALL: the first ultraviolet fiber fed spectrograph

    Tuttle, Sarah E.; Schiminovich, David; Grange, Robert; Rahman, Shahinur; Matuszewski, Mateusz; Milliard, Bruno; Deharveng, Jean-Michel; Martin, D. Christopher
    FIREBall (the Faint Intergalactic Redshifted Emission Balloon) is a balloon-borne 1m telescope coupled to an ultraviolet fiber-fed spectrograph. FIREBall is designed to study the faint and diffuse emission of the warm hot intergalactic medium, until now detected primarily in absorption. FIREBall is a pathfinding mission to test new technology and make new constraints on the temperature and density of this gas. FIREBall has flown twice, the most recent flight (June 2009) a fully functioning science flight. Here we describe the spectrograph design, current setup, and calibration measurements from the campaign.

  12. Charge-coupled devices detectors with high quantum efficiency at UV wavelengths

    Hamden, Erika T.; Jewell, April D.; Shapiro, Charles A.; Cheng, Samuel R.; Goodsall, Tim M.; Hennessy, John; Hoenk, Michael; Jones, Todd; Gordon, Sam; Ong, Hwei Ru; Schiminovich, David; Martin, D. Christopher; Nikzad, Shouleh
    We report on multilayer high efficiency antireflection coating (ARC) design and development for use at UV wavelengths on CCDs and other Si-based detectors. We have previously demonstrated a set of single-layer coatings, which achieve >50% quantum efficiency (QE) in four bands from 130 to 300 nm. We now present multilayer coating designs that significantly outperform our previous work between 195 and 215 nm. Using up to 11 layers, we present several model designs to reach QE above 80%. We also demonstrate the successful performance of 5 and 11 layer ARCs on silicon and fused silica substrates. Finally, we present a...

  13. A Newly Forming Cold Flow Protogalactic Disk, a Signature of Cold Accretion from the Cosmic Web

    Martin, D. Christopher; Matuszewski, Mateusz; Morrissey, Patrick; Neill, James D.; Moore, Anna; Steidel, Charles C.; Trainor, Ryan
    How galaxies form from, and are fueled by, gas from the intergalactic medium (IGM) remains one of the major unsolved problems in galaxy formation. While the classical Cold Dark Matter paradigm posits galaxies forming from cooling virialized gas, recent theory and numerical simulations have highlighted the importance of cold accretion flows—relatively cool (T ~ few × 104 K) unshocked gas streaming along filaments into dark matter halos, including hot, massive, high-redshift halos. These flows are thought to deposit gas and angular momentum into the circumgalactic medium resulting in disk- or ring-like structures, eventually coalescing into galaxies forming at filamentary intersections....

  14. UV photon-counting CCD detectors that enable the next generation of UV spectroscopy missions: AR coatings that can achieve 80-90% QE

    Hamden, Erika T.; Greer, Frank; Schiminovich, David; Nikzad, Shouleh; Martin, D. Christopher
    We describe recent progress in the development of anti-reflection coatings for use at UV wavelengths on CCDs and other Si-based detectors. We have previously demonstrated a set of coatings which are able to achieve greater than 50% QE in 4 bands from 130nm to greater than 300nm. We now present new refinements of these AR-coatings which will improve performance in a narrower bandpass by 50% over previous work. Successful test films have been made to optimize transmission at 190nm, reaching 80% potential transmission.

  15. Noise and dark performance for FIREBall-2 EMCCD delta-doped CCD detector

    Hamden, Erika T.; Lingner, Nicole; Kyne, Gillian; Morrissey, Patrick; Martin, D. Christopher
    The Faint Intergalactic-medium Redshifted Emission Balloon (FIREBall-2) is an experiment designed to observe low density emission from HI, CIV, and OVI in the circum-galactic medium around low-redshift galaxies. To detect this diffuse emission, we use a high-efficiency photon-counting EMCCD as part of FIREBall-2's detector. The flight camera system includes a custom printed circuit board, a mechanical cryo-cooler, zeolite and charcoal getters, and a Nüvü controller, for fast read-out speeds and waveform shaping. Here we report on overall detector system performance, including pressure and temperature stability. We describe dark current and CIC measurements at several temperatures and substrate voltages, with the...

  16. Deep GALEX UV Survey of the Kepler Field. I. Point Source Catalog

    Olmedo, Manuel; Lloyd, James; Mamajek, Eric E.; Chávez, Miguel; Bertone, Emanuele; Martin, D. Christopher; Neill, James D.
    We report observations of a deep near-ultraviolet (NUV) survey of the Kepler field made in 2012 with the Galaxy Evolution Explorer (GALEX) Complete All-Sky UV Survey Extension (CAUSE). The GALEX-CAUSE Kepler survey (GCK) covers 104 square degrees of the Kepler field and reaches a limiting magnitude of NUV ~ 22.6 at 3σ. Analysis of the GCK survey has yielded a catalog of 669,928 NUV sources, of which 475,164 are cross-matched with stars in the Kepler Input Catalog. Approximately 327 of 451 confirmed exoplanet host stars and 2614 of 4696 candidate exoplanet host stars identified by Kepler have NUV photometry in...

  17. The detection rate of early UV emission from supernovae: A dedicated GALEX/PTF survey and calibrated theoretical estimates

    Ganot, Noam; Gal-Yam, Avishay; Ofek, Eran O.; Sagiv, Ilan; Waxman, Eli; Lapid, Ofer; Kulkarni, Shrinivas R.; Ben-Ami, Sagi; Kasliwal, Mansi M.; Chelouche, Doron; Rafter, Stephen; Behar, Ehud; Laor, Ari; Poznanski, Dovi; Nakar, Udi; Maoz, Dan; Trakhtenbrot, Benny; Neill, James D.; Barlow, Thomas A.; Martin, D. Christopher; Gezari, Suvi; Arcavi, Iair; Bloom, Joshua S.; Nugent, Peter E.; Sullivan, Mark
    The radius and surface composition of an exploding massive star, as well as the explosion energy per unit mass, can be measured using early UV observations of core collapse supernovae (SNe). We present the first results from a simultaneous GALEX/PTF search for early UV emission from SNe. Six Type II SNe and one Type II superluminous SN (SLSN-II) are clearly detected in the GALEX NUV data. We compare our detection rate with theoretical estimates based on early, shock-cooling UV light curves calculated from models that fit existing Swift and GALEX observations well, combined with volumetric SN rates. We find that...

  18. Exploring the Role of Globular Cluster Specific Frequency on the Nova Rates in Three Virgo Elliptical Galaxies

    Curtin, C.; Shafter, A. W.; Pritchet, C. J.; Neill, J. D.; Kundu, A.; Maccarone, T. J.
    It has been proposed that a galaxy's nova rate might be enhanced by the production of nova progenitor binaries in the dense cores of its globular clusters (GCs). To explore this idea, relative nova rates in three Virgo elliptical galaxies, M87, M49, and M84, which have significantly different GC specific frequencies (SN) of 14, 3.6, and 1.6, respectively, were measured over the course of 4 epochs spanning a period of 14 months. To simplify the analysis, observations of the nearly equidistant galaxies were made on the same nights, with the same integration times, and through the same filter (Hα), so...

  19. The Influence of Galaxy Surface Brightness on the Mass–Metallicity Relation

    Wu, Po-Feng; Kudritzki, Rolf-Peter; Tully, R. Brent; Neill, J. D.
    We study the effect of surface brightness on the mass–metallicity relation using nearby galaxies whose gas content and metallicity profiles are available. Previous studies using fiber spectra indicated that lower surface brightness galaxies have systematically lower metallicities for their stellar mass, but the results were uncertain because of aperture effects. With stellar masses and surface brightnesses measured at Wide-field Infrared Explorer W1 and W2 bands, we re-investigate the surface brightness dependence with spatially resolved metallicity profiles and find similar results. We further demonstrate that the systematical difference cannot be explained by the gas content of galaxies. For two galaxies with...

  20. A Giant Protogalactic Disk Linked to the Cosmic Web

    Martin, D. Christopher; Matuszewski, Mateusz; Morrissey, Patrick; Neill, James D.; Moore, Anna; Cantalupo, Sebastiano; Prochaska, J. Xavier; Chang, Daphne
    The specifics of how galaxies form from, and are fuelled by, gas from the intergalactic medium remain uncertain. Hydrodynamic simulations suggest that ‘cold accretion flows’—relatively cool (temperatures of the order of 10^4 kelvin), unshocked gas streaming along filaments of the cosmic web into dark-matter halos—are important. These flows are thought to deposit gas and angular momentum into the circumgalactic medium, creating disk- or ring-like structures that eventually coalesce into galaxies that form at filamentary intersections. Recently, a large and luminous filament, consistent with such a cold accretion flow, was discovered near the quasi-stellar object QSO UM287 at redshift 2.279 using...

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