2004/05/12 by Patrick B. Hall, Stephanie A. Snedden, M. Niederste-Ostholt +5 · 1 citation
Physics and Astronomy · #Absorption (acoustics) #Absorption spectroscopy #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Atomic physics #Emission spectrum #Equivalent width #Excited state #Full width at half maximum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Line (geometry) #Optics #Physics #Quasar #Spectral line #astro-ph
paper · pdf · doi:10.1086/422488
published as Astron.J.128:534,2004 · 9 pages, 4 figures, accepted by AJ for the August 2004 issue
arxiv created 2004/05/12 · openalex publication_date 2004/08/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The z = 3.02 quasar SDSS J095253.83+011421.9 exhibits broad metal-line emission (C IV FWHM ≃ 9000 km s -1 ), but broad Lyα emission is not present. Instead, only a narrow Lyα line is observed (FWHM ≃ 1140 km s -1 ). The large C /Lyα ratio in the broad-line region (BLR) emission from this object can be matched most closely by a BLR dominated by gas at very high densities (10 15 cm -3 ), which suppresses the Lyα emission, and illuminated by an incident power law extending to ∼200 μm, which yields increased emission from purely collisionally excited coolant lines (such as C IV, N V, and O VI) but not from recombination lines like Lyα. However, the strong C III emission predicted by this model is not observed, and the observed broad C III] emission must come from a lower density BLR component and should be accompanied by broad Lyα emission, which is not observed. The least unlikely explanation for this spectrum seems to be that any intrinsic broad Lyα emission is removed by smooth N V absorption in the red wing of the Lyα emission line and by smooth Lyα absorption in the blue wing of the Lyα emission line. This postulated smooth absorption would be in addition to the strong, associated, narrow absorption seen in numerous ions. Smooth absorption in Lyα, N V, and O VI, but not in C IV, would be unusual, but not impossible, although it is suspicious that the postulated absorption must almost exactly cancel the postulated intrinsic broad emission. We conclude that the spectrum of SDSS J0952+0114 appears unique (among ≃3600 SDSS spectra of quasars at z > 2.12) because of some combination of unusual parameters, and we discuss possible observations to determine the combination of circumstances responsible for the spectrum.