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Articles 1 - 4 of 4
Full-Text Articles in Physical Sciences and Mathematics
On The Disappearance Of The Broad-Line Region In Low-Luminosity Active Galactic Nuclei, Moshe Elitzur, Luis C. Ho
On The Disappearance Of The Broad-Line Region In Low-Luminosity Active Galactic Nuclei, Moshe Elitzur, Luis C. Ho
Physics and Astronomy Faculty Publications
The disk-wind scenario for the broad-line region (BLR) and toroidal obscuration in active galactic nuclei (AGNs) predicts the disappearance of the BLR at low luminosities. In accordance with the model predictions, data from a nearly complete sample of nearby AGNs show that the BLR disappears at luminosities lower than 5 × 1039(M/107 M⊙)2/3 erg s-1, where M is the black hole mass. The radiative efficiency of accretion onto the black hole is ≲10-3 for these sources, indicating that their accretion is advection-dominated.
Discovery Of Variability In The Very High Energy Gamma-Ray Emission Of 1es 1218+304 With Veritas, P. T. Reynolds, Et Al
Discovery Of Variability In The Very High Energy Gamma-Ray Emission Of 1es 1218+304 With Veritas, P. T. Reynolds, Et Al
Physical Sciences Publications
We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of ~6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching ~20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured …
Mid-Infrared Spectroscopy Of Candidate Active Galactic Nuclei-Dominated Submillimeter Galaxies, K Coppin, A Pope, K Menendez-Delmestre, Dm Alexander, Js Dunlop, E Egami, J Gabor, E Ibar, Rj Ivison, Je Austermann, Aw Blain, Sc Chapman, Dl Clements, L Dunne, S Dye, D Farrah, Dh Hughes, Amj Mortier, Mj Page, M Rowan-Robinson, D Scott, C Simpson, I Smail, Am Swinbank, M Vaccari, Min Yun
Mid-Infrared Spectroscopy Of Candidate Active Galactic Nuclei-Dominated Submillimeter Galaxies, K Coppin, A Pope, K Menendez-Delmestre, Dm Alexander, Js Dunlop, E Egami, J Gabor, E Ibar, Rj Ivison, Je Austermann, Aw Blain, Sc Chapman, Dl Clements, L Dunne, S Dye, D Farrah, Dh Hughes, Amj Mortier, Mj Page, M Rowan-Robinson, D Scott, C Simpson, I Smail, Am Swinbank, M Vaccari, Min Yun
Astronomy Department Faculty Publication Series
Spitzer spectroscopy has revealed that 80% of submm galaxies (SMGs) are starburst (SB)-dominated in the mid-infrared. Here we focus on the remaining 20% that show signs of harboring powerful active galactic nuclei (AGNs). We have obtained Spitzer-InfraRed Spectrograph spectroscopy of a sample of eight SMGs that are candidates for harboring powerful AGNs on the basis of IRAC color selection (S 8 μm/S 4.5 μm>2, i.e., likely power-law mid-infrared spectral energy distributions). SMGs with an AGN dominating (50%) their mid-infrared emission could represent the "missing link" sources in an evolutionary sequence involving a major merger. First …
The Agn Fraction Of Submm-Selected Galaxies And Contributions To The Submm/Mm-Wave Extragalactic Background Light, S Serjeant, M Negrello, C Pearson, A Mortier, J Austermann, I Aretxaga, D Clements, S Chapman, S Dye, J Dunlop, L Dunne, D Farrah, D Hughes, Hm Lee, H Matsuhara, E Ibar, M Im, Ws Jeong, S Kim, S Oyabu, T Takagi, T Wada, G Wilson, M Vaccari, Min Yun
The Agn Fraction Of Submm-Selected Galaxies And Contributions To The Submm/Mm-Wave Extragalactic Background Light, S Serjeant, M Negrello, C Pearson, A Mortier, J Austermann, I Aretxaga, D Clements, S Chapman, S Dye, J Dunlop, L Dunne, D Farrah, D Hughes, Hm Lee, H Matsuhara, E Ibar, M Im, Ws Jeong, S Kim, S Oyabu, T Takagi, T Wada, G Wilson, M Vaccari, Min Yun
Astronomy Department Faculty Publication Series
We present a comparison of the SCUBA half degree extragalactic survey (SHADES) at 450 μm, 850 μm and 1100 μm with deep guaranteed time 15 μm AKARI FU-HYU survey data and Spitzer guaranteed time data at 3.6-24 μm in the Lockman hole east. The AKARI data was analysed using bespoke software based in part on the drizzling and minimum-variance matched filtering developed for SHADES, and was cross-calibrated against ISO fluxes. Our stacking analyses find AKARI 15 μm galaxies with 200 μJy contribute >10% of the 450 μm background, but only <4% of …