Results 51 to 60 of about 111,891 (295)

Changing-look Quasar Candidates: First Results from Follow-up Spectroscopy of Highly Optically Variable Quasars [PDF]

Astrophysical Journal, 2018
Active galactic nuclei (AGNs) that show strong rest-frame optical/UV variability in their blue continuum and broad line emission are classified as changing-look AGN, or at higher luminosities, changing-look quasars (CLQs).
C. MacLeod, P. Green, S. Anderson, A. Bruce, M. Eracleous, M. Graham, D. Homan, A. Lawrence, Amy Lebleu, N. Ross, J. Ruan, J. Runnoe, D. Stern, W. Burgett, K. Chambers, N. Kaiser, E. Magnier, N. Metcalfe   +17 more
semanticscholar   +1 more source

Spectral energy distributions of quasars selected in the mid-infrared

, 2012
We present preliminary results on fitting of SEDs to 142 z>1 quasars selected in the mid-infrared. Our quasar selection finds objects ranging in extinction from highly obscured, type-2 quasars, through more lightly reddened type-1 quasars and normal type-
A. O. Petric, A. Sajina, D. Farrah, D. M. Nielsen, E. L. Gates, M. Lacy, S. E. Ridgway, T. Urrutia   +7 more
core   +1 more source

The X-ray Properties of z>4 Quasars [PDF]

, 2000
We report on a search for X-ray emission from quasars with redshifts greater than four using the ROSAT public database. Our search has doubled the number of z>4 quasars detected in X-rays from 6 to 12.
Blair A. J., Donald P. Schneider, Efstathiou G., Fabian A. C., Hawkins M. R. S., McMahon R. G., Molthagen K., Omont A., Pfeffermann E., Reeves J. N., Shai Kaspi, Shaver P. A., W. N. Brandt, Zickgraf F.-J.   +13 more
core   +2 more sources

What makes red quasars red? Observational evidence for dust extinction from line ratio analysis

, 2017
Red quasars are very red in the optical through near-infrared (NIR) wavelengths, which is possibly due to dust extinction in their host galaxies as expected in a scenario in which red quasars are an intermediate population between merger-driven star ...
Im, Myungshin, Kim, Dohyeong
core   +1 more source

A Population of Dust-rich Quasars at z ~ 1.5 [PDF]

, 2012
We report Herschel SPIRE (250, 350, and 500 μm) detections of 32 quasars with redshifts 0.5 ≤z < 3.6 from the Herschel Multi-tiered Extragalactic Survey (HerMES).
Bergeron, Jacqueline, Bock, Jamie, Cooray, Asantha, Dai, Y. Sophia, Elvis, Martin, Fazio, Giovanni, Hatziminaoglou, Evanthia, Huang, Jia-Sheng, Ibar, Edo, Magdis, Georgios E., Oliver, Seb J., Omont, Alain, Page, Mathew J., Pérez-Fournon, Ismael, Rigopoulou, Dimitra, Roseboom, I. G., Scott, Douglas, Symeonidis, Myrto, Trichas, Markos, Vieira, Joaquin D., Willmer, Christopher N. A., Zemcov, Michael   +21 more
core   +3 more sources

Physical Properties of 15 Quasars at z ≳ 6.5 [PDF]

, 2017
Quasars are galaxies hosting accreting supermassive black holes; due to their brightness, they are unique probes of the early universe. To date, only a few quasars have been reported at (
C. Mazzucchelli, E. Bañados, E. Bañados, B. Venemans, R. Decarli, E. Farina, F. Walter, A. Eilers, H. Rix, R. Simcoe, D. Stern, Xiaohui Fan, E. Schlafly, G. D. Rosa, J. Hennawi, J. Hennawi, K. Chambers, J. Greiner, W. Burgett, P. Draper, N. Kaiser, R. Kudritzki, E. Magnier, N. Metcalfe, C. Waters, R. Wainscoat   +25 more
semanticscholar   +1 more source

The Infrared Traced Star Formation Rates of Associated Absorption Lines Quasars

The Astrophysical Journal
Some optically selected quasars exhibit Mg ii- associated absorption lines (AALs), and their origin remains unclear. In this paper, we compile a sample of 1769 quasars, with or without Mg ii AALs, of which 1689 are far-infrared (FIR) detected quasars and
Zhe-Geng Chen, Rui-Jing Lu, Zhi-Fu Chen, Wen-Qiang Liang, Xing-Long Peng, Jing Li, Wei-Rong Huang   +6 more
doaj   +1 more source

A Survey of z~6 Quasars in the SDSS Deep Stripe. II. Discovery of Six Quasars at z_{AB}>21

, 2009
We present the discovery of six new quasars at z~6 selected from the Sloan Digital Sky Survey (SDSS) southern survey, a deep imaging survey obtained by repeatedly scanning a stripe along the celestial equator.
Abazajian, Bertin, Cool, Donald P. Schneider, Elena Malanushenko, Fan, Fan, Fan, Fuyan Bian, Gordon T. Richards, Gunn, Gunn, Hogg, Hopkins, Huan Lin, Ivezić, James Annis, Jiang, Jiang, Kuenley Chiu, Kurk, Kurk, Linhua Jiang, Lupton, Lupton, McGreer, Michael A. Strauss, Mortlock, Pier, Richards, Robert H. Lupton, Schlegel, Sebastian Jester, Shen, Shen, Smith, Spergel, Stoughton, Venemans, Vestergaard, Viktor Malanushenko, Willott, Willott, Willott, Xiaohui Fan, York   +45 more
core   +1 more source

Correlation between radio and broad-line emissions in radio-loud quasars [PDF]

, 1999
Radio emission is a good indicator of the jet power of radio-loud quasars, while the emission in broad-line can well represent the accretion disc radiation in quasars. We compile a sample of all sources of which the broad-line fluxes are available from 1
Baker, Baldwin, Baldwin, Bergeron, Blandford, Blandford, Capetti, Celotti, Celotti, Corbin, Corbin, D. R. Jiang, di Serego Alighieri, Ellingson, Espey, Falcke, Falcke, Falcke, Francis, Fricke, Gelderman, Ghisellini, Hunstead, Jackson, Kinney, Kühr, Kühr, Lacy, Lawrence, Marziani, Neugebauer, Oke, Osmer, Pauliny Toth, Perez, Rawlings, Richstone, Rudy, Serjeant, Smith, Steiner, Stickel, Stickel, Stickel, Stickel, Stickel, Stickel, Stickel, Stickel, Stickel, Stiko, Stockton, Tadhunter, Vermeulen, Wampler, Wang, Warren, Wills, Wills, Xinwu Cao   +59 more
core   +3 more sources

Gemini GNIRS Near-infrared Spectroscopy of 50 Quasars at z ≳ 5.7 [PDF]

Astrophysical Journal, 2018
We report initial results from a large Gemini program to observe z ≳ 5.7 quasars with GNIRS near-IR spectroscopy. Our sample includes 50 quasars with simultaneous ∼0.85–2.5 μm spectra covering the rest-frame ultraviolet and major broad emission lines ...
Yue Shen, Jin Wu, Linhua Jiang, E. Bañados, Xiaohui Fan, L. Ho, D. Riechers, M. Strauss, B. Venemans, M. Vestergaard, F. Walter, Feige Wang, C. Willott, Xue-bing Wu, Jinyi Yang   +14 more
semanticscholar   +1 more source