Search results for "QSOS"
showing 7 items of 7 documents
A Study of the Correlation between the Amplification of the Fe Kα Line and the X‐Ray Continuum of Quasars due to Microlensing
2006
The observed enhancement of the Fe Kα line in three gravitationally lensed QSOs (MG J0414+0534, QSO 2237+0305, and H1413+117) is interpreted in terms of microlensing, even when equivalent X-ray continuum amplification is not observed. In order to interpret these observations, first we studied the effects of microlensing on quasar spectra produced by a straight fold caustic crossing over a standard relativistic accretion disk. The disk emission was analyzed using the ray-tracing method, considering Schwarzschild and Kerr metrics. When the emission is separated into two regions (an inner disk corresponding to the Fe Kα line and an outer annulus corresponding to the continuum, or vice versa), …
Measuring Microlensing using Spectra of Multiply Lensed Quasars
2012
We report on a program of spectroscopic observations of gravitationally-lensed QSOs with multiple images. We seek to establish whether microlensing is occurring in each QSO image using only single-epoch observations. We calculate flux ratios for the cores of emission lines in image pairs to set a baseline for no microlensing. The offset of the continuum flux ratios relative to this baseline yields the microlensing magnification free from extinction, as extinction affects the continuum and the lines equally. When we find chromatic microlensing, we attempt to constrain the size of the QSO accretion disk. SDSSJ1004+4112 and HE1104-1805 show chromatic microlensing with amplitudes $0.2< |\Delta …
The ALHAMBRA survey: Discovery of a faint QSO at z = 5.41
2013
[Aims]: We aim to illustrate the potentiality of the Advanced Large, Homogeneous Area, Medium-Band Redshift Astronomical (ALHAMBRA) survey to investigate the high-redshift universe through the detection of quasi stellar objects (QSOs) at redshifts higher than 5. [Methods]: We searched for QSOs candidates at high redshift by fitting an extensive library of spectral energy distributions-including active and non-active galaxy templates, as well as stars-to the photometric database of the ALHAMBRA survey (composed of 20 optical medium-band plus the 3 broad-band JHKs near-infrared filters). [Results]: Our selection over ≈1 square degree of ALHAMBRA data (∼1/4 of the total area covered by the sur…
The High A(V) Quasar Survey: Reddened quasi-stellar objects selected from optical/near-infrared photometry - II
2014
Quasi-stellar objects (QSOs) whose spectral energy distributions (SEDs) are reddened by dust either in their host galaxies or in intervening absorber galaxies are to a large degree missed by optical color selection criteria like the one used by the Sloan Digital Sky Survey (SDSS). To overcome this bias against red QSOs, we employ a combined optical and near-infrared color selection. In this paper, we present a spectroscopic follow-up campaign of a sample of red candidate QSOs which were selected from the SDSS and the UKIRT Infrared Deep Sky Survey (UKIDSS). The spectroscopic data and SDSS/UKIDSS photometry are supplemented by mid-infrared photometry from the Wide-field Infrared Survey Explo…
Study of the Extended Narrow‐Line Region in the Host Galaxy of the Lensed QSO 2237+0305 (z= 1.69)
2004
The detection of spatially extended line emission in multiply imaged QSOs offers a new possibility to study the properties (kinematics and structure) of the ionized gas in the host galaxies of high-redshift QSOs. We have studied the arc of extended emission detected in Q2237+0305, finding that it arises from the core of the C III] λ1909 emission line and that the emission in the wings is compact. From the morphology of the emission-line profiles we have identified an additional narrow emission line component affecting the core of the spectra in the region of the arc (around component D). The kinematic analysis shows that the extended narrow-line region (NLR) exhibits broadening similar to t…
Microlensing of a Biconical Broad‐Line Region
2006
The influence of microlensing in the profiles of the emission lines generated in a biconical geometry is discussed. Microlensing amplification in this anisotropic model is not directly related to the bicone's intrinsic size but depends on the orientation of the bicone axis and on the cone aperture. The orientation of the projected bicone with respect to the shear of the magnification pattern can induce very interesting effects, like the quasi-periodic enhancements of the red/blue part of the emission line profile or the lack of correlation between the broad line region (BLR) and continuum light curves of QSOs. The emission line profiles of a BLR moving in a high caustic concentration exhibi…
Quasi-stellar objects in the ALHAMBRA survey
2012
[Context]: Even the spectroscopic capabilities of today's ground and space-based observatories can not keep up with the enormous flow of detections (>10 5 deg -2) unveiled in modern cosmological surveys as: i) would be required enormous telescope time to perform the spectroscopic follow-ups and ii) spectra remain unattainable for the fainter detected population. In the past decade, the typical accuracy of photometric redshift (photo-z) determination has drastically improved. Nowdays, it has become a perfect complement to spectroscopy, closing the gap between photometric surveys and their spectroscopic follow-ups. The photo-z precision for active galactic nuclei (AGN) has always lagged behin…