1,356 research outputs found
The Intermediate Line Region and the Baldwin Effect
Statistical investigations of samples of quasars have established that
clusters of properties are correlated. The strongest trends among the
ultraviolet emission-line properties are characterized by the object-to-object
variation of emission from low-velocity gas, the so-called ``intermediate-line
region'' or ILR. The strongest trends among the optical emission-line
properties are characterized by the object-to-object variation of the line
intensity ratio of [O III] 5007 to optical Fe II. Additionally, the strength of
ILR emission correlates with [O III]/Fe II, as well as with radio and X-ray
properties. The fundamental physical parameter driving these related
correlations is not yet identified. Because the variation in the ILR dominates
the variation in the equivalent widths of lines showing the Baldwin effect, it
is important to understand whether the physical parameter underlying this
variation also drives the Baldwin effect or is a primary source of scatter in
the Baldwin effect.Comment: 11 pages, to appear in the proceedings of the meeting on "Quasars as
Standard Candles for Cosmology" held on May 18-22, 1998, at La Serena, Chile.
To be published by ASP, editor G. Ferlan
Outflows and the Physical Properties of Quasars
We have investigated a sample of 5088 quasars from the Sloan Digital Sky
Survey Second Data Release in order to determine how the frequency and
properties of broad absorptions lines (BALs) depend on black hole mass,
bolometric luminosity, Eddington fraction (L/L_Edd), and spectral slope. We
focus only on high-ionization BALs and find a number of significant results.
While quasars accreting near the Eddington limit are more likely to show BALs
than lower systems, BALs are present in quasars accreting at only a
few percent Eddington. We find a stronger effect with bolometric luminosity,
such that the most luminous quasars are more likely to show BALs. There is an
additional effect, previously known, that BAL quasars are redder on average
than unabsorbed quasars. The strongest effects involving the quasar physical
properties and BAL properties are related to terminal outflow velocity. Maximum
observed outflow velocities increase with both the bolometric luminosity and
the blueness of the spectral slope, suggesting that the ultraviolet luminosity
to a great extent determines the acceleration. These results support the idea
of outflow acceleration via ultraviolet line scattering.Comment: Uses emulateapj.cls, 14 pages including 7 tables and 7 figures.
Accepted for publication in the Astrophysical Journal, Unabridged version of
Table 4 can be downloaded from http://physics.uwyo.edu/agn
X-ray and optical counterparts of hard X-ray selected sources from the SHEEP survey: first results
We present followup observations of five hard X-ray sources from the ASCA
5-10 keV SHEEP survey, which has a limiting flux of erg
cm s. Chandra data have been obtained to improve the X-ray
positions from a few arcmin to , which allows unambiguous optical
identification. While the objects almost certainly house AGN based on their
X-ray luminosity, optical spectroscopy reveals a variety of properties. The
identifications indicate that the SHEEP survey samples the same populations as
deeper surveys which probe the origin of the X-ray background, but because the
SHEEP sources are far brighter, they are more amenable to detailed followup
work. We find a variety of classifications and properties, including a type II
QSO, a galaxy undergoing star formation, and a broad-line AGN which has a very
hard X-ray spectrum, indicating substantial absorption in the X-ray but none in
the optical. Two objects have X-ray/optical flux ratios which, were they at an
X-ray flux level typical of objects in Chandra deep surveys, would place them
in the ``optically faint'' category. They are both identified with broad line
QSOs at z. Clearly this survey - which is relatively unbiased against
obscured objects - is revealing a set of remarkable objects quite different to
the familiar classes of AGN found in previous optical and soft X-ray surveys.Comment: 5 pages, 3 figures. MNRAS, in pres
The Profiles of H-Beta and [OIII] 5007 in Radio-Loud Quasars
Moderate-resolution spectra of the H--[O III] 5007 region
have been obtained for 41 radio-loud quasars in order to investigate
relationships among their broad- and narrow-line profiles, radio structures,
and X-ray properties. Spectra from the literature have been included to form a
data set of 60 radio-loud quasars. A variety of statistical analyses have been
performed, identifying several strong, related trends. The FWHM, equivalent
width, and degree of redward asymmetry of H increase with decreasing
radio core dominance (an orientation indicator), whereas the FWHM of [O III]
5007 increases with luminosity and . These and other
effects are briefly discussed.Comment: To appear in the Astrophysical Journal Supplement. Warning: A large
paper, 360kb uuencoded, compressed postscript, including figures (except Fig.
1a-g, the spectra, which are at the ftp site below) and tables. The entire
paper is also available by anonymous ftp at
ftp://pan.as.utexas.edu/pub/HBpreprint
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