@article{19964, abstract = {It has been suggested that giant planet occurrence peaks for stars with M* ≈ 3 M⊙ at a value a factor of 4 higher than observed for solar-mass stars. This population of giant planets predicted to frequently orbit main-sequence B stars at a ≈ 10 au is difficult to characterize during the few hundred million years while fusion persists in their host stars. By the time those stars become massive, young white dwarfs, any giant planets present would still be luminous as a consequence of their recent formation. From an initial sample of 2195 Gaia-identified massive, young white dwarfs, we use homogeneous Spitzer Infrared Array Camera (IRAC) photometry to search for evidence of unresolved giant planets. For 30 systems, these IRAC data provide sensitivity to objects with M ≲ 10 MJup, and we identify one candidate with M ≈ 4 MJup orbiting the white dwarf GALEX J071816.4+373139. Correcting for the possibility that some of the white dwarfs in our sample result from mergers, we find a giant planet occurrence n GP = 0.11+0.13-0.07 for stars with initial masses M* ≳ 3 M⊙. Our occurrence inference is consistent with both the Doppler-inferred occurrence of giant planets orbiting M* ≈ 2 M⊙ giant stars and the theoretically predicted factor of 4 enhancement in the occurrence of giant planets orbiting M* ≈ 3 M⊙ stars relative to solar-mass stars. Future James Webb Space Telescope NIRCam observations of our sample would provide sensitivity to Saturn-mass planets and thereby a definitive estimate of the occurrence of giant planets orbiting stars with M* ≳ 3 M⊙.}, author = {Cheng, Sihao and Schlaufman, Kevin C. and Caiazzo, Ilaria}, issn = {1538-3881}, journal = {The Astronomical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{A candidate giant planet companion to the massive, young White Dwarf GALEX J071816.4+373139 informs the occurrence of giant planets orbiting B stars}}, doi = {10.3847/1538-3881/addd21}, volume = {170}, year = {2025}, } @article{11604, abstract = {The NASA Transiting Exoplanet Survey Satellite (TESS) is observing tens of millions of stars with time spans ranging from ∼27 days to about 1 yr of continuous observations. This vast amount of data contains a wealth of information for variability, exoplanet, and stellar astrophysics studies but requires a number of processing steps before it can be fully utilized. In order to efficiently process all the TESS data and make it available to the wider scientific community, the TESS Data for Asteroseismology working group, as part of the TESS Asteroseismic Science Consortium, has created an automated open-source processing pipeline to produce light curves corrected for systematics from the short- and long-cadence raw photometry data and to classify these according to stellar variability type. We will process all stars down to a TESS magnitude of 15. This paper is the next in a series detailing how the pipeline works. Here, we present our methodology for the automatic variability classification of TESS photometry using an ensemble of supervised learners that are combined into a metaclassifier. We successfully validate our method using a carefully constructed labeled sample of Kepler Q9 light curves with a 27.4 days time span mimicking single-sector TESS observations, on which we obtain an overall accuracy of 94.9%. We demonstrate that our methodology can successfully classify stars outside of our labeled sample by applying it to all ∼167,000 stars observed in Q9 of the Kepler space mission.}, author = {Audenaert, J. and Kuszlewicz, J. S. and Handberg, R. and Tkachenko, A. and Armstrong, D. J. and Hon, M. and Kgoadi, R. and Lund, M. N. and Bell, K. J. and Bugnet, Lisa Annabelle and Bowman, D. M. and Johnston, C. and García, R. A. and Stello, D. and Molnár, L. and Plachy, E. and Buzasi, D. and Aerts, C.}, issn = {1538-3881}, journal = {The Astronomical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {5}, publisher = {IOP Publishing}, title = {{TESS Data for Asteroseismology (T’DA) stellar variability classification pipeline: Setup and application to the Kepler Q9 data}}, doi = {10.3847/1538-3881/ac166a}, volume = {162}, year = {2021}, } @article{13459, abstract = {The B emission-line stars are rapid rotators that were probably spun up by mass and angular momentum accretion through mass transfer in an interacting binary. Mass transfer will strip the donor star of its envelope to create a small and hot subdwarf remnant. Here we report on Hubble Space Telescope/STIS far-ultraviolet spectroscopy of a sample of Be stars that reveals the presence of the hot sdO companion through the calculation of cross-correlation functions of the observed and model spectra. We clearly detect the spectral signature of the sdO star in 10 of the 13 stars in the sample, and the spectral signals indicate that the sdO stars are hot, relatively faint, and slowly rotating as predicted by models. A comparison of their temperatures and radii with evolutionary tracks indicates that the sdO stars occupy the relatively long-lived, He-core burning stage. Only 1 of the 10 detections was a known binary prior to this investigation, which emphasizes the difficulty of finding such Be+sdO binaries through optical spectroscopy. However, these results and others indicate that many Be stars probably host hot subdwarf companions.}, author = {Wang, Luqian and Gies, Douglas R. and Peters, Geraldine J. and Götberg, Ylva Louise Linsdotter and Chojnowski, S. Drew and Lester, Kathryn V. and Howell, Steve B.}, issn = {1538-3881}, journal = {The Astronomical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {5}, publisher = {American Astronomical Society}, title = {{The detection and characterization of Be+sdO binaries from HST/STIS FUV spectroscopy}}, doi = {10.3847/1538-3881/abf144}, volume = {161}, year = {2021}, } @article{15216, abstract = {AM CVn systems are a rare type of accreting binary that consists of a white dwarf and a helium-rich, degenerate donor star. Using the Zwicky Transient Facility (ZTF), we searched for new AM CVn systems by focusing on blue, outbursting stars. We first selected outbursting stars using the ZTF alerts. We cross matched the candidates with Gaia and Pan-STARRS catalogs. The initial selection of candidates based on the Gaia BP-RP contains 1751 unknown objects. We used the Pan-STARRS g-r and r-i color in combination with the Gaia color to identify 59 strong AM CVn candidates. We obtained identification spectra of 35 sources, of which 18 are high-priority candidates, and discovered nine new AM CVn systems and one magnetic CV that shows only He-ii lines. Using the outburst recurrence time, we estimate the orbital periods of the nine new AM CVn systems that are in the range of 29–50 minutes. We conclude that targeted follow up of blue, outbursting sources is an efficient method to find new AM CVn systems and we plan to follow up all candidates we identified to systematically study the population of outbursting AM CVn systems.}, author = {van Roestel, Jan and Creter, Leah and Kupfer, Thomas and Szkody, Paula and Fuller, Jim and Green, Matthew J. and Rich, R. Michael and Sepikas, John and Burdge, Kevin and Caiazzo, Ilaria and Mróz, Przemek and Prince, Thomas A. and Duev, Dmitry A. and Graham, Matthew J. and Shupe, David L. and Laher, Russ R. and Mahabal, Ashish A. and Masci, Frank J.}, issn = {1538-3881}, journal = {The Astronomical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {3}, publisher = {American Astronomical Society}, title = {{A systematic search for outbursting AM CVn systems with the Zwicky transient facility}}, doi = {10.3847/1538-3881/ac0622}, volume = {162}, year = {2021}, } @article{17528, abstract = {We performed a series of numerical experiments to quantify the sensitivity of the predictions for weak lensing statistics obtained in ray-tracing dark matter (DM)-only simulations, to two hyper-parameters that influence the accuracy as well as the computational cost of the predictions: the thickness of the lens planes used to build past light cones and the mass resolution of the underlying DM simulation. The statistics considered are the power spectrum (PS) and a series of non-Gaussian observables, including the one-point probability density function, lensing peaks, and Minkowski functionals. Counterintuitively, we find that using thin lens planes (< 60 h−1 Mpc on a 240 h−1 Mpc simulation box) suppresses the PS over a broad range of scales beyond what would be acceptable for a survey comparable to the Large Synoptic Survey Telescope (LSST). A mass resolution of 7.2 × 1011 h−1 M⊙ per DM particle (or 2563 particles in a (240 h−1 Mpc)3 box) is sufficient to extract information using the PS and non-Gaussian statistics from weak lensing data at angular scales down to 1' with LSST-like levels of shape noise.}, author = {Matilla, José Manuel Zorrilla and Waterval, Stefan and Haiman, Zoltán}, issn = {0004-6256}, journal = {The Astronomical Journal}, number = {6}, publisher = {American Astronomical Society}, title = {{Optimizing simulation parameters for weak lensing analyses involving non-Gaussian observables}}, doi = {10.3847/1538-3881/ab8f8c}, volume = {159}, year = {2020}, } @article{11616, abstract = {We present the discovery of HD 221416 b, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. HD 221416 b (HIP 116158, TOI-197) is a bright (V = 8.2 mag), spectroscopically classified subgiant that oscillates with an average frequency of about 430 μHz and displays a clear signature of mixed modes. The oscillation amplitude confirms that the redder TESS bandpass compared to Kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with TESS 2 minute cadence observations. Asteroseismic modeling yields a robust determination of the host star radius (R⋆ = 2.943 ± 0.064 R⊙), mass (M⋆ = 1.212 ± 0.074 M⊙), and age (4.9 ± 1.1 Gyr), and demonstrates that it has just started ascending the red-giant branch. Combining asteroseismology with transit modeling and radial-velocity observations, we show that the planet is a "hot Saturn" (Rp = 9.17 ± 0.33 R⊕) with an orbital period of ∼14.3 days, irradiance of F = 343 ± 24 F⊕, and moderate mass (Mp = 60.5 ± 5.7 M⊕) and density (ρp = 0.431 ± 0.062 g cm−3). The properties of HD 221416 b show that the host-star metallicity–planet mass correlation found in sub-Saturns (4–8 R⊕) does not extend to larger radii, indicating that planets in the transition between sub-Saturns and Jupiters follow a relatively narrow range of densities. With a density measured to ∼15%, HD 221416 b is one of the best characterized Saturn-size planets to date, augmenting the small number of known transiting planets around evolved stars and demonstrating the power of TESS to characterize exoplanets and their host stars using asteroseismology.}, author = {Huber, Daniel and Chaplin, William J. and Chontos, Ashley and Kjeldsen, Hans and Christensen-Dalsgaard, Jørgen and Bedding, Timothy R. and Ball, Warrick and Brahm, Rafael and Espinoza, Nestor and Henning, Thomas and Jordán, Andrés and Sarkis, Paula and Knudstrup, Emil and Albrecht, Simon and Grundahl, Frank and Andersen, Mads Fredslund and Pallé, Pere L. and Crossfield, Ian and Fulton, Benjamin and Howard, Andrew W. and Isaacson, Howard T. and Weiss, Lauren M. and Handberg, Rasmus and Lund, Mikkel N. and Serenelli, Aldo M. and Rørsted Mosumgaard, Jakob and Stokholm, Amalie and Bieryla, Allyson and Buchhave, Lars A. and Latham, David W. and Quinn, Samuel N. and Gaidos, Eric and Hirano, Teruyuki and Ricker, George R. and Vanderspek, Roland K. and Seager, Sara and Jenkins, Jon M. and Winn, Joshua N. and Antia, H. M. and Appourchaux, Thierry and Basu, Sarbani and Bell, Keaton J. and Benomar, Othman and Bonanno, Alfio and Buzasi, Derek L. and Campante, Tiago L. and Çelik Orhan, Z. and Corsaro, Enrico and Cunha, Margarida S. and Davies, Guy R. and Deheuvels, Sebastien and Grunblatt, Samuel K. and Hasanzadeh, Amir and Di Mauro, Maria Pia and A. García, Rafael and Gaulme, Patrick and Girardi, Léo and Guzik, Joyce A. and Hon, Marc and Jiang, Chen and Kallinger, Thomas and Kawaler, Steven D. and Kuszlewicz, James S. and Lebreton, Yveline and Li, Tanda and Lucas, Miles and Lundkvist, Mia S. and Mann, Andrew W. and Mathis, Stéphane and Mathur, Savita and Mazumdar, Anwesh and Metcalfe, Travis S. and Miglio, Andrea and F. G. Monteiro, Mário J. P. and Mosser, Benoit and Noll, Anthony and Nsamba, Benard and Joel Ong, Jia Mian and Örtel, S. and Pereira, Filipe and Ranadive, Pritesh and Régulo, Clara and Rodrigues, Thaíse S. and Roxburgh, Ian W. and Aguirre, Victor Silva and Smalley, Barry and Schofield, Mathew and Sousa, Sérgio G. and Stassun, Keivan G. and Stello, Dennis and Tayar, Jamie and White, Timothy R. and Verma, Kuldeep and Vrard, Mathieu and Yıldız, M. and Baker, David and Bazot, Michaël and Beichmann, Charles and Bergmann, Christoph and Bugnet, Lisa Annabelle and Cale, Bryson and Carlino, Roberto and Cartwright, Scott M. and Christiansen, Jessie L. and Ciardi, David R. and Creevey, Orlagh and Dittmann, Jason A. and Nascimento, Jose-Dias Do and Eylen, Vincent Van and Fürész, Gabor and Gagné, Jonathan and Gao, Peter and Gazeas, Kosmas and Giddens, Frank and Hall, Oliver J. and Hekker, Saskia and Ireland, Michael J. and Latouf, Natasha and LeBrun, Danny and Levine, Alan M. and Matzko, William and Natinsky, Eva and Page, Emma and Plavchan, Peter and Mansouri-Samani, Masoud and McCauliff, Sean and Mullally, Susan E. and Orenstein, Brendan and Soto, Aylin Garcia and Paegert, Martin and van Saders, Jennifer L. and Schnaible, Chloe and Soderblom, David R. and Szabó, Róbert and Tanner, Angelle and Tinney, C. G. and Teske, Johanna and Thomas, Alexandra and Trampedach, Regner and Wright, Duncan and Yuan, Thomas T. and Zohrabi, Farzaneh}, issn = {0004-6256}, journal = {The Astronomical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics}, number = {6}, publisher = {IOP Publishing}, title = {{A hot Saturn orbiting an oscillating late subgiant discovered by TESS}}, doi = {10.3847/1538-3881/ab1488}, volume = {157}, year = {2019}, } @article{17686, abstract = {The coalescence of a supermassive black hole binary (SMBHB) is thought to be accompanied by an electromagnetic (EM) afterglow, produced by the viscous infall of the surrounding circumbinary gas disk after the merger. It has been proposed that once the merger has been detected in gravitational waves (GWs) by LISA, follow-up EM searches for this afterglow can help identify the EM counterpart of the LISA source. Here we study whether the afterglows may be sufficiently bright and numerous to be detectable in EM surveys alone. The viscous afterglow, which lasts for years to decades for SMBHBs in LISA's sensitivity window, is characterized by rapid increases in both the bolometric luminosity and in the spectral hardness of the source. If quasar activity is triggered by the same major galaxy mergers that produce SMBHBs, then the afterglow could be interpreted as a signature of the birth of a quasar. Using an idealized model for the post-merger viscous spreading of the circumbinary disk and the resulting light curve, and using the observed luminosity function of quasars as a proxy for the SMBHB merger rate, we delineate the survey requirements for identifying such birthing quasars. If circumbinary disks have a high disk surface density and viscosity, an all-sky soft X-ray survey with a sensitivity of ~<3x10^-14 erg s^-1 cm^-2 and a time resolution of ~months could identify dozens of birthing quasars with sustained brightening rates of >10%/yr. If >1% of the X-ray emission is reprocessed into optical frequencies, birthing quasars could also be identified in optical transient surveys such as the LSST. Distinguishing a birthing quasar from other variable sources may be facilitated by the monotonic hardening of its spectrum, but will likely remain challenging. This reinforces the notion that joint EM-plus-GW observations offer the best prospects for identifying the EM signatures of SMBHB mergers.}, author = {Tanaka, Takamitsu and Haiman, Zoltán and Menou, Kristen}, issn = {0004-6256}, journal = {The Astronomical Journal}, number = {2}, pages = {642--651}, publisher = {American Astronomical Society}, title = {{Witnessing the birth of a quasar}}, doi = {10.1088/0004-6256/140/2/642}, volume = {140}, year = {2010}, } @article{17727, abstract = {We report on i-band snapshot observations of 157 Sloan Digital Sky Survey (SDSS) quasars at 4-3.8 (3 sigma), assuming a break in the quasar luminosity function at M*_145=-24.5. This constraint is considerably stronger than the limit of beta>-4.63 obtained from the absence of lensing in four z>5.7 quasars. Such constraints are important for our understanding of the true space density of high-redshift quasars and the ionization state of the early universe.}, author = {Richards, Gordon T. and Haiman, Zoltán and Pindor, Bartosz and Strauss, Michael A. and Fan, Xiaohui and Eisenstein, Daniel and Schneider, Donald P. and Bahcall, Neta A. and Brinkmann, J. and Fukugita, Masataka}, issn = {0004-6256}, journal = {The Astronomical Journal}, number = {1}, pages = {49--54}, publisher = {American Astronomical Society}, title = {{A snapshot survey for gravitational lenses among z ≥ 4.0 quasars. II. Constraints on the 4.0 < z < 5.4 quasar population}}, doi = {10.1086/498063}, volume = {131}, year = {2006}, } @article{17790, abstract = {Over the last few years, the Sloan Digital Sky Survey (SDSS) has discovered several hundred quasars with redshift between 4.0 and 6.4. Including the effects of magnification bias, one expects a priori that an appreciable fraction of these objects are gravitationally lensed. We have used the Advanced Camera for Surveys on the Hubble Space Telescope to carry out a snapshot imaging survey of high-redshift SDSS quasars to search for gravitationally split lenses. This paper, the first in a series reporting the results of the survey, describes snapshot observations of four quasars at z = 5.74, 5.82, 5.99, and 6.30, respectively. We find that none of these objects has a lensed companion within 5 mag with a separation larger than 0farcs3; within 2.5 mag we can rule out companions within 0farcs1. Based on the nondetection of strong lensing in these four systems, we constrain the z ∼ 6 luminosity function to a slope of β > -4.63 (3 σ), assuming a break in the quasar luminosity function at M = -24.1. We discuss the implications of this constraint on the ionizing background due to quasars in the early universe. Given that these quasars are not highly magnified, estimates of the masses of their central engines by the Eddington argument must be taken seriously, possibly challenging models of black hole formation.}, author = {Richards, Gordon T. and Strauss, Michael A. and Pindor, Bartosz and Haiman, Zoltán and Fan, Xiaohui and Eisenstein, Daniel and Schneider, Donald P. and Bahcall, Neta A. and Brinkmann, J. and Brunner, Robert}, issn = {0004-6256}, journal = {The Astronomical Journal}, number = {3}, pages = {1305--1312}, publisher = {American Astronomical Society}, title = {{A snapshot survey for gravitational lenses among z ≥ 4.0 quasars. I. The z >5.7 sample}}, doi = {10.1086/381906}, volume = {127}, year = {2004}, } @article{17750, abstract = {We present the discovery of three new quasars at z>6 in 1300 deg^2 of SDSS imaging data, J114816.64+525150.3 (z=6.43), J104845.05+463718.3 (z=6.23) and J163033.90+401209.6 (z=6.05). The first two objects have weak Ly alpha emission lines; their redshifts are determined from the positions of the Lyman break. They are only accurate to 0.05 and could be affected by the presence of broad absorption line systems. The last object has a Ly alpha strength more typical of lower redshift quasars. Based on a sample of six quasars at z>5.7 that cover 2870 deg^2 presented in this paper and in Paper I, we estimate the comoving density of luminous quasars at z 6 and M_{1450} < -26.8 to be (8 +/- 3)x10^{-10} Mpc^{-3} (for H_0 = 50 km/s/Mpc, Omega = 1). HST imaging of two z>5.7 quasars and high-resolution ground-based images (seeing 0.4'') of three additional z>5.7 quasars show that none of them is gravitationally lensed. The luminosity distribution of the high-redshfit quasar sample suggests the bright end slope of the quasar luminosity function at z 6 is shallower than Psi L^{-3.5} (2-sigma), consistent with the absence of strongly lensed objects.}, author = {Fan, Xiaohui and Strauss, Michael A. and Schneider, Donald P. and Becker, Robert H. and White, Richard L. and Haiman, Zoltán and Gregg, Michael and Pentericci, Laura and Grebel, Eva K. and Narayanan, Vijay K. and Loh, Yeong-Shang and Richards, Gordon T. and Gunn, James E. and Lupton, Robert H. and Knapp, Gillian R. and Ivezić, Željko and Brandt, W. N. and Collinge, Matthew and Hao, Lei and Harbeck, Daniel and Prada, Francisco and Schaye, Joop and Strateva, Iskra and Zakamska, Nadia and Anderson, Scott and Brinkmann, Jon and Bahcall, Neta A. and Lamb, Don Q. and Okamura, Sadanori and Szalay, Alex and York, Donald G.}, issn = {0004-6256}, journal = {The Astronomical Journal}, number = {4}, pages = {1649--1659}, publisher = {American Astronomical Society}, title = {{A survey of z > 5.7 quasars in the Sloan Digital Sky Survey. II. Discovery of three additional quasars at z > 6}}, doi = {10.1086/368246}, volume = {125}, year = {2003}, } @article{17799, abstract = {The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of ≈106 galaxies, 100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001 June, the SDSS released to the general astronomical community its early data release, roughly 462 deg2 of imaging data including almost 14 million detected objects and 54,008 follow-up spectra. The imaging data were collected in drift-scan mode in five bandpasses (u, g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2, 22.2, 21.3, and 20.5, respectively. The photometric calibration is reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are flux- and wavelength-calibrated, with 4096 pixels from 3800 to 9200 Å at R ≈ 1800. We present the means by which these data are distributed to the astronomical community, descriptions of the hardware used to obtain the data, the software used for processing the data, the measured quantities for each observed object, and an overview of the properties of this data set.}, author = {Stoughton, Chris and Lupton, Robert H. and Bernardi, Mariangela and Blanton, Michael R. and Burles, Scott and Castander, Francisco J. and Connolly, A. J. and Eisenstein, Daniel J. and Frieman, Joshua A. and Hennessy, G. S. and Hindsley, Robert B. and Ivezić, Željko and Kent, Stephen and Kunszt, Peter Z. and Lee, Brian C. and Meiksin, Avery and Munn, Jeffrey A. and Newberg, Heidi Jo and Nichol, R. C. and Nicinski, Tom and Pier, Jeffrey R. and Richards, Gordon T. and Richmond, Michael W. and Schlegel, David J. and Smith, J. Allyn and Strauss, Michael A. and SubbaRao, Mark and Szalay, Alexander S. and Thakar, Aniruddha R. and Tucker, Douglas L. and Vanden Berk, Daniel E. and Yanny, Brian and Adelman, Jennifer K. and Anderson, Jr., John E. and Anderson, Scott F. and Annis, James and Bahcall, Neta A. and Bakken, J. A. and Bartelmann, Matthias and Bastian, Steven and Bauer, Amanda and Berman, Eileen and Böhringer, Hans and Boroski, William N. and Bracker, Steve and Briegel, Charlie and Briggs, John W. and Brinkmann, J. and Brunner, Robert and Carey, Larry and Carr, Michael A. and Chen, Bing and Christian, Damian and Colestock, Patrick L. and Crocker, J. H. and Csabai, István and Czarapata, Paul C. and Dalcanton, Julianne and Davidsen, Arthur F. and Davis, John Eric and Dehnen, Walter and Dodelson, Scott and Doi, Mamoru and Dombeck, Tom and Donahue, Megan and Ellman, Nancy and Elms, Brian R. and Evans, Michael L. and Eyer, Laurent and Fan, Xiaohui and Federwitz, Glenn R. and Friedman, Scott and Fukugita, Masataka and Gal, Roy and Gillespie, Bruce and Glazebrook, Karl and Gray, Jim and Grebel, Eva K. and Greenawalt, Bruce and Greene, Gretchen and Gunn, James E. and de Haas, Ernst and Haiman, Zoltán and Haldeman, Merle and Hall, Patrick B. and Hamabe, Masaru and Hansen, Brad and Harris, Frederick H. and Harris, Hugh and Harvanek, Michael and Hawley, Suzanne L. and Hayes, J. J. E. and Heckman, Timothy M. and Helmi, Amina and Henden, Arne and Hogan, Craig J. and Hogg, David W. and Holmgren, Donald J. and Holtzman, Jon and Huang, Chih-Hao and Hull, Charles and Ichikawa, Shin-Ichi and Ichikawa, Takashi and Johnston, David E. and Kauffmann, Guinevere and Kim, Rita S. J. and Kimball, Tim and Kinney, E. and Klaene, Mark and Kleinman, S. J. and Klypin, Anatoly and Knapp, G. R. and Korienek, John and Krolik, Julian and Kron, Richard G. and Krzesiński, Jurek and Lamb, D. Q. and Leger, R. French and Limmongkol, Siriluk and Lindenmeyer, Carl and Long, Daniel C. and Loomis, Craig and Loveday, Jon and MacKinnon, Bryan and Mannery, Edward J. and Mantsch, P. M. and Margon, Bruce and McGehee, Peregrine and McKay, Timothy A. and McLean, Brian and Menou, Kristen and Merelli, Aronne and Mo, H. J. and Monet, David G. and Nakamura, Osamu and Narayanan, Vijay K. and Nash, Thomas and Neilsen, Jr., Eric H. and Newman, Peter R. and Nitta, Atsuko and Odenkirchen, Michael and Okada, Norio and Okamura, Sadanori and Ostriker, Jeremiah P. and Owen, Russell and Pauls, A. George and Peoples, John and Peterson, R. S. and Petravick, Donald and Pope, Adrian and Pordes, Ruth and Postman, Marc and Prosapio, Angela and Quinn, Thomas R. and Rechenmacher, Ron and Rivetta, Claudio H. and Rix, Hans-Walter and Rockosi, Constance M. and Rosner, Robert and Ruthmansdorfer, Kurt and Sandford, Dale and Schneider, Donald P. and Scranton, Ryan and Sekiguchi, Maki and Sergey, Gary and Sheth, Ravi and Shimasaku, Kazuhiro and Smee, Stephen and Snedden, Stephanie A. and Stebbins, Albert and Stubbs, Christopher and Szapudi, István and Szkody, Paula and Szokoly, Gyula P. and Tabachnik, Serge and Tsvetanov, Zlatan and Uomoto, Alan and Vogeley, Michael S. and Voges, Wolfgang and Waddell, Patrick and Walterbos, René and Wang, Shu-i and Watanabe, Masaru and Weinberg, David H. and White, Richard L. and White, Simon D. M. and Wilhite, Brian and Wolfe, David and Yasuda, Naoki and York, Donald G. and Zehavi, Idit and Zheng, Wei}, issn = {1538-3881}, journal = {The Astronomical Journal}, number = {1}, pages = {485--548}, publisher = {American Astronomical Society}, title = {{Sloan digital sky survey: Early data release}}, doi = {10.1086/324741}, volume = {123}, year = {2002}, } @article{17825, abstract = {We present the results from a survey of i-dropout objects selected from ∼1550 deg^2 of multicolor imaging data from the Sloan Digital Sky Survey to search for luminous quasars at z ≳ 5.8. Objects with i*-z* > 2.2 and z* < 20.2 are selected, and follow-up J-band photometry is used to separate L- and T-type cool dwarfs from high-redshift quasars. We describe the discovery of three new quasars, SDSSp J083643.85+005453.3 (z = 5.82), J130608.26+035626.3 (z = 5.99), and J103027.10+052455.0 (z = 6.28). The quasar SDSSp J083643.85+005453.3 is a radio source with flux of 1.1 mJy at 20 cm. The spectra of all three quasars show strong and broad Lyα + N V emission lines and very strong Lyα forest absorption, with a mean continuum decrement DA > 0.90. The ARC 3.5 m spectrum of SDSSp J103027.10+052455.0 shows that over a range of ∼300 Å immediately blueward of the Lyα emission, the average transmitted flux is only 0.003 ± 0.020 times that of the continuum level, consistent with zero flux over a ∼300 Å range of the Lyα forest region and suggesting a tentative detection of the complete Gunn-Peterson trough. The existence of strong metal lines in the quasar spectra suggests early metal enrichment in the quasar environment. The three new objects, together with the previously published z = 5.8 quasar SDSSp J104433.04-012502.2, form a complete color-selected flux-limited sample at z ≳ 5.8. We estimate the selection function of this sample, taking into account the estimated variations in the quasar spectral energy distribution, as well as observational photometric errors. We find that at z = 6, the comoving density of luminous quasars at M1450 < -26.8 (H0 = 50 km s-1 Mpc-1, Ω = 1) is 1.1 × 10-9 Mpc-3. This is a factor of ∼2 lower than that at z ∼ 5 and is consistent with an extrapolation of the observed quasar evolution at z < 5. Using the current sample, we discuss the constraint on the shape of the quasar luminosity function and the implications for the contribution of quasars to the ionizing background at z ∼ 6. The luminous quasars discussed in the paper have central black hole masses of several times 109 M⊙ by the Eddington argument, with likely dark halo masses on the order of 1013 M⊙. Their observed space density provides a sensitive test of models of quasar and galaxy formation at high redshift.}, author = {Fan, Xiaohui and Narayanan, Vijay K. and Lupton, Robert H. and Strauss, Michael A. and Knapp, Gillian R. and Becker, Robert H. and White, Richard L. and Pentericci, Laura and Leggett, S. K. and Haiman, Zoltán and Gunn, James E. and Ivezić, Željko and Schneider, Donald P. and Anderson, Scott F. and Brinkmann, J. and Bahcall, Neta A. and Connolly, Andrew J. and Csabai, István and Doi, Mamoru and Fukugita, Masataka and Geballe, Tom and Grebel, Eva K. and Harbeck, Daniel and Hennessy, Gregory and Lamb, Don Q. and Miknaitis, Gajus and Munn, Jeffrey A. and Nichol, Robert and Okamura, Sadanori and Pier, Jeffrey R. and Prada, Francisco and Richards, Gordon T. and Szalay, Alex and York, Donald G.}, issn = {0004-6256}, journal = {The Astronomical Journal}, number = {6}, pages = {2833--2849}, publisher = {American Astronomical Society}, title = {{A survey of z > 5.8 quasars in the sloan digital sky survey. I. Discovery of three new quasars and the spatial density of luminous quasars at z ∼ 6}}, doi = {10.1086/324111}, volume = {122}, year = {2001}, } @article{17823, abstract = {We present observations of SDSSp J104433.04-012502.2, a luminous quasar at z = 5.80 discovered from Sloan Digital Sky Survey (SDSS) multicolor imaging data. This object was selected as an i'-band dropout object, with i* = 21.8 ± 0.2 and z* = 19.2 ± 0.1. It has an absolute magnitude M1450 = -27.2 (H0 = 50 km s-1 Mpc-1, q0 = 0.5). The spectrum shows a strong and broad Lyα emission line, strong Lyα forest absorption lines with a mean continuum decrement DA = 0.91 and a Lyman limit system at z = 5.72. The spectrum also shows strong O I and Si IV emission lines similar to those of quasars at z ≲ 5, suggesting that these metals were produced at a redshift beyond 6. The lack of a Gunn-Peterson trough in the spectrum indicates that the universe is already highly ionized at z ∼ 5.8. Using a high-resolution spectrum in the Lyα forest region, we place a conservative upper limit on the optical depth because of the Gunn-Peterson effect of τ < 0.5 in regions of minimum absorption. The Lyα forest absorption in this object is much stronger than that in quasars at z ≲ 5. The object is unresolved in a deep image with excellent seeing, implying that it is unlensed. The black hole mass of this quasar is ∼3 × 109 M⊙ if we assume no lensing amplification and that it is radiating at the Eddington luminosity, implying that it resides in a very massive dark matter halo. The discovery of one quasar at M1450 < -27 in a survey area of 600 deg2 is consistent with an extrapolation of the observed luminosity function at lower redshifts. The abundance and evolution of such quasars can provide sensitive tests for models of quasar and galaxy formation.}, author = {Fan, Xiaohui and White, Richard L. and Davis, Marc and Becker, Robert H. and Strauss, Michael A. and Haiman, Zoltán and Schneider, Donald P. and Gregg, Michael D. and Gunn, James E. and Knapp, G. R. and Lupton, Robert H. and Anderson, Jr., John E. and Anderson, Scott F. and Annis, James and Bahcall, Neta A. and Boroski, William N. and Brunner, Robert J. and Chen, Bing and Connolly, Andrew J. and Csabai, István and Doi, Mamoru and Fukugita, Masataka and Hennessy, G. S. and Hindsley, Robert B. and Ichikawa, Takashi and Ivezić, Željko and Loveday, Jon and Meiksin, Avery and McKay, Timothy A. and Munn, Jeffrey A. and Newberg, Heidi Jo and Nichol, Robert and Okamura, Sadanori and Pier, Jeffrey R. and Sekiguchi, Maki and Shimasaku, Kazuhiro and Stoughton, Chris and Szalay, Alexander S. and Szokoly, Gyula P. and Thakar, Aniruddha R. and Vogeley, Michael S. and York, Donald G.}, issn = {0004-6256}, journal = {The Astronomical Journal}, number = {3}, pages = {1167--1174}, publisher = {American Astronomical Society}, title = {{The Discovery of a Luminous z = 5.80 Quasar from the Sloan Digital Sky Survey}}, doi = {10.1086/301534}, volume = {120}, year = {2000}, }