Browsing by Subject "photometry"

Now showing 1 - 7 of 7
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    Characterization of the nearby L/T binary brown dwarf wise J104915.57–531906.1 at 2 pc from the sun
    (2013) Kniazev, A Y; Väisänen, P; Mužić, K; Mehner, A; Boffin, H M J; Kurtev, R; Melo, C; Ivanov, V D; Girard, J; Mawet, D; Schmidtobreick, L; Huelamo, N; Borissova, J; Minniti, D; Ishibashi, K; Potter, S B; Beletsky, Y; Buckley, D A H; Crawford, S; Gulbis, A A S; Kotze, P; Miszalski, B; Pickering, T E; Romero-Colmenero, E; Williams, T B
    WISE J104915.57$-$531906.1 is a L/T brown dwarf binary located 2pc from the Sun. The pair contains the closest known brown dwarfs and is the third closest known system, stellar or sub-stellar. We report comprehensive follow-up observations of this newly uncovered system. We have determined the spectral types of both components (L8+/-1, for the primary, agreeing with the discovery paper; T1.5+/-2 for the secondary, which was lacking spectroscopic type determination in the discovery paper) and, for the first time, their radial velocities (V_rad~23.1, 19.5 km/s) using optical spectra obtained at the Southern African Large Telescope (SALT) and other facilities located at the South African Astronomical Observatory (SAAO). The relative radial velocity of the two components is smaller than the range of orbital velocities for theoretically predicted masses, implying that they form a gravitationally bound system. We report resolved near-infrared JHK_S photometry from the IRSF telescope at the SAAO which yields colors consistent with the spectroscopically derived spectral types. The available kinematic and photometric information excludes the possibility that the object belongs to any of the known nearby young moving groups or associations. Simultaneous optical polarimetry observations taken at the SAAO 1.9-m give a non-detection with an upper limit of 0.07%. For the given spectral types and absolute magnitudes, 1Gyr theoretical models predict masses of 0.04--0.05 M_odot for the primary, and 0.03--0.05 M_odot for the secondary.
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    Improved constraints on type Ia supernova host galaxy properties using multi-wavelength photometry and their correlations with supernova properties
    (2011) Gupta, Ravi R; D’Andrea, Chris B; Sako, Masao; Conroy, Charlie; Smith, Mathew; Bassett, Bruce; Frieman, Joshua A; Garnavich, Peter M; Jha, Saurabh W; Kessler, Richard; Lampeitl, Hubert; Marriner, John; Nichol, Robert C; Schneider, Donald P
    We improve estimates of the stellar mass and mass-weighted average age of Type Ia supernova (SN Ia) host galaxies by combining UV and near-IR photometry with optical photometry in our analysis. Using 206 SNe Ia drawn from the full three-year Sloan Digital Sky Survey (SDSS-II) Supernova Survey (median redshift of z 0.2) and multi-wavelength host-galaxy photometry from SDSS, the Galaxy Evolution Explorer, and the United Kingdom Infrared Telescope Infrared Deep Sky Survey, we present evidence of a correlation (1.9σ confidence level) between the residuals of SNe Ia about the best-fit Hubble relation and the mass-weighted average age of their host galaxies. The trend is such that older galaxies host SNe Ia that are brighter than average after standard light-curve corrections are made. We also confirm, at the 3.0σ level, the trend seen by previous studies that more massive galaxies often host brighter SNe Ia after light-curve correction.
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    Mid-infrared selection of active galactic nuclei with the wide-field infrared survey explorer. II. properties of wise -selected active galactic nuclei in the NDWFS Boötes field
    (2013) Assef, R J; Stern, D; Kochanek, C S; Blain, A W; Brodwin, M; Brown, M J I; Donoso, E; Eisenhardt, P R M; Jannuzi, B T; Jarrett, T H; Stanford, S A; Tsai, C W; Wu, J; Yan, L
    Stern et al. presented a study of Wide-field Infrared Survey Explorer (WISE) selection of active galactic nuclei (AGNs) in the 2 deg2 COSMOS field, finding that a simple criterion W1-W2 ≥ 0.8 provides a highly reliable and complete AGN sample for W2 < 15.05, where the W1 and W2 passbands are centered at 3.4 μm and 4.6 μm, respectively. Here we extend this study using the larger 9 deg2 NOAO Deep Wide-Field Survey Boötes field which also has considerably deeper WISE observations than the COSMOS field, and find that this simple color cut significantly loses reliability at fainter fluxes. We define a modified selection criterion combining the W1–W2 color and the W2 magnitude to provide highly reliable or highly complete AGN samples for fainter WISE sources. In particular, we define a color-magnitude cut that finds 130 ± 4 deg–2 AGN candidates for W2 < 17.11 with 90% reliability. Using the extensive UV through mid-IR broadband photometry available in this field, we study the spectral energy distributions of WISE AGN candidates. We find that, as expected, the WISE AGN selection can identify highly obscured AGNs, but that it is biased toward objects where the AGN dominates the bolometric luminosity output. We study the distribution of reddening in the AGN sample and discuss a formalism to account for sample incompleteness based on the step-wise maximum-likelihood method of Efstathiou et al. The resulting dust obscuration distributions depend strongly on AGN luminosity, consistent with the trend expected for a receding torus. At L AGN ~ 3 × 1044 erg s–1, 29% ± 7% of AGNs are observed as Type 1, while at ~4 × 1045 erg s–1 the fraction is 64% ± 13%. The distribution of obscuration values suggests that dust in the torus is present as both a diffuse medium and in optically thick clouds.
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    PHOTOMETRIC ESTIMATES OF REDSHIFTS AND DISTANCE MODULI FOR TYPE Ia SUPERNOVAE
    (2010) Kessler, Richard; Cinabro, David; Bassett, Bruce; Dilday, Benjamin; Frieman, Joshua A; Garnavich, Peter M; Jha, Saurabh; Marriner, John; Nichol, Robert C; Sako, Masao; Smith, Mathew; Bernstein, Joseph P; Bizyaev, Dmitry; Goobar, Ariel; Kuhlmann, Stephen; Schneider, Donald P; Stritzinger, Maximilian
    Large planned photometric surveys will discover hundreds of thousands of supernovae (SNe), outstripping the resources available for spectroscopic follow-up and necessitating the development of pure ...
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    PHOTOMETRIC TYPE Ia SUPERNOVA CANDIDATES FROM THE THREE-YEAR SDSS-II SN SURVEY DATA
    (2011) Sako, Masao; Bassett, Bruce; Connolly, Brian; Dilday, Benjamin; Cambell, Heather; Frieman, Joshua A; Gladney, Larry; Kessler, Richard; Lampeitl, Hubert; Marriner, John; Miquel, Ramon; Nichol, Robert C; Schneider, Donald P; Smith, Mathew; Sollerman, Jesper
    We analyze the three-year Sloan Digital Sky Survey II (SDSS-II) Supernova (SN) Survey data and identify a sample of 1070 photometric Type Ia supernova (SN Ia) candidates based on their multiband li ...
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    THE SDSS-II SUPERNOVA SURVEY: PARAMETERIZING THE TYPE Ia SUPERNOVA RATE AS A FUNCTION OF HOST GALAXY PROPERTIES
    (2012) Smith, Mathew; Nichol, Robert C; Dilday, Benjamin; Marriner, John; Kessler, Richard; Bassett, Bruce; Cinabro, David; Frieman, Joshua; Garnavich, Peter; Jha, Saurabh W; Lampeitl, Hubert; Sako, Masao; Schneider, Donald P; Sollerman, Jesper
    Using data from the Sloan Digital Sky Supernova Survey-II (SDSS-II SN Survey), we measure the rate of Type Ia supernovae (SNe Ia) as a function of galaxy properties at intermediate redshift. A samp ...
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    The seventh data release of the sloan digital sky survey
    (2009) Abazajian, Kevork N; Adelman‐McCarthy, Jennifer K; AgYeros, 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; Budavári, Tamás; Carey, Larry N
    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 deg2 of imaging data, with most of the ~2000 deg2 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° long, 2fdg5 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 deg2. The survey has completed spectroscopy over 9380 deg2 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.