19 research outputs found
A VLA Survey of Radio-Selected SDSS Broad Absorption Line Quasars
We have built a sample of 74 radio-selected broad absorption line quasars
from the Sloan Digital Sky Survey Data Release 5 (SDSS DR5) and Faint Images of
the Radio Sky at Twenty Centimeters (FIRST), along with a well matched sample
of 74 unabsorbed "normal" quasars. The sources have been observed with the NRAO
Very Large Array/Expanded Very Large Array at 8.4 GHz (3.5 cm) and 4.9 GHz (6
cm). All sources have additional archival 1.4 GHz (21 cm) data. Here we present
the measured radio fluxes, spectral indices, and our initial findings. The
percentage of BAL quasars with extended structure (on the order of 10%) in our
sample is similar to previous studies at similar resolutions, suggesting that
BAL quasars are indeed generally compact, at least at arsecond resolutions. The
majority of sources do not appear to be significantly variable at 1.4 GHz, but
we find two previously unidentified BAL quasars that may fit into the "polar"
BAL category. We also identify a significant favoring of steeper radio spectral
index for BAL compared to non-BAL quasars. This difference is apparent for
several different measures of the spectral index, and persists even when
restricting the samples to only include compact objects. Because radio spectral
index is a statistical indicator of viewing angle for large samples, these
results suggest that BAL quasars do have a range of orientations but are more
often observed farther from the jet axis compared to normal quasars.Comment: Accepted for publication in the Astrophysical Journa
Discovery of a Classic FR-II Broad Absorption Line Quasar from the FIRST Survey
We have discovered a remarkable quasar, FIRST J101614.3+520916, whose optical
spectrum shows unambiguous broad absorption features while its double-lobed
radio morphology and luminosity clearly indicate a classic Fanaroff-Riley Type
II radio source. Its radio luminosity places it at the extreme of the recently
established class of radio-loud broad absorption line quasars (Becker et al.
1997, 2000; Brotherton et al. 1998). Because of its hybrid nature, we speculate
that FIRST J101614.3+520916 is a typical FR-II quasar which has been
rejuvenated as a broad absorption line (BAL) quasar with a Compact Steep
Spectrum core. The direction of the jet axis of FIRST J101614.3+520916 can be
estimated from its radio structure and optical brightness, indicating that we
are viewing the system at a viewing angle of > 40 degrees. The position angles
of the radio jet and optical polarization are not well-aligned, differing by 20
to 30 degrees. When combined with the evidence presented by Becker et al.
(2000) for a sample of 29 BAL quasars showing that at least some BAL quasars
are viewed along the jet axis, the implication is that no preferred viewing
orientation is necessary to observe BAL systems in a quasar's spectrum. This,
and the probable young nature of compact steep spectrum sources, leads
naturally to the alternate hypothesis that BALs are an early stage in the lives
of quasars.Comment: 14 pages, 6 postscript figures; accepted for publication in the
Astrophysical Journa
What Determines the Depth of BALs? Keck HIRES Observations of BALQSO 1603+300
We find that the depth and shape of the broad absorption lines (BALs) in
BALQSO 1603+3002 are determined largely by the fraction of the emitting source
which is covered by the BAL flow. In addition, the observed depth of the BALs
is poorly correlated with their real optical depth. The implication of this
result is that abundance studies based on direct extraction of column densities
from the depth of the absorption troughs are unreliable. Our conclusion is
based on analysis of unblended absorption features of two lines from the same
ion (in this case the Si IV doublet), which allows unambiguous separation of
covering factor and optical depth effects. The complex morphology of the
covering factor as a function of velocity suggests that the BALs are produced
by several physically separated outflows. The covering factor is ion dependent
in both depth and velocity width. We also find evidence that in BALQSO
1603+3002 the flow does not cover the broad emission line region.Comment: 13 pages, 2 figures, accepted for publication in Ap
The radio-luminosity - black hole mass correlation for quasars from the FIRST Bright Quasar Survey, and a ``unification scheme'' for radio-loud and radio-quiet quasars
Several independent lines of evidence now point to a correlation between
black hole mass, M_bh, and radio-luminosity. In this paper we discuss the
correlation for quasars from the FIRST Bright Quasar Survey (FBQS), using black
hole mass estimates from Hbeta linewidths. The FBQS objects fill in the gap
between the radio-loud and radio-quiet quasars in the radio-luminosity -
optical-luminosity plane, and we find that they fill the corresponding gap in
the M_bh - radio luminosity correlation. There is thus a continuous variation
of radio luminosity with M_bh, and no evidence for a ``switch'' at some set of
critical parameter values which turns on powerful radio jets. By combining the
FBQS data with that for quasars from the Palomar-Green survey we find evidence
for a dependence of radio-luminosity on accretion rate relative to the
Eddington limit, L/L_Edd, as well as on M_bh, consistent with the well-known
radio-optical correlation for radio-loud quasars. We therefore suggest a new
scheme to ``unify'' radio-loud and radio-quiet objects in which radio
luminosity scales proportional to M_bh^{1.9+/-0.2}(L/L_Edd)^{1.0} for
L/L_Edd~0.1, with an apparently weaker accretion rate dependence at low
L/L_Edd. The scatter about this relation is +/-1.1 dex, and may well hide
significant contributions from other physical effects, such as black hole spin
and radio source environment.Comment: 7 pages, 4 figures, accepted for publication in ApJ Letter
Keck Hires Observations of the QSO First J104459.6+365605: Evidence for a Large Scale Outflow
This paper presents an analysis of a Keck HIRES spectrum of the QSO FIRST
J104459.6+365605. The line of sight towards the QSO contains two clusters of
outflowing clouds that give rise to broad blue shifted absorption lines. The
outflow velocities of the clouds range from -200 to -1200 km/s and from -3400
to -5200 km/s, respectively. The width of the individual absorption lines
ranges from 50 to more than 1000 km/s. The most prominent absorption lines are
those of Mg II, Mg I, and Fe II. The low ionization absorption lines occur at
the same velocities as the most saturated Mg II lines, showing that the Fe II,
Mg I and Mg II line forming regions must be closely associated. Many absorption
lines from excited states of Fe II are present, allowing a determination of the
population of several low lying energy levels. From this we determine an
electron density in the Fe II line forming regions of 4000 per cubic cm.
Modelling the ionization state of the absorbing gas with this value of the
electron density as a constraint, we find that the distance between the Fe II
and Mg I line forming region and the continuum source is of order 700 parsec.
From the correspondence in velocity between the Fe II, Mg I and Mg II lines
we infer that the Mg II lines must be formed at the same distance. The Mg II
absorption fulfills the criteria for Broad Absorption Lines defined by Weymann
et al. (1991). This large distance is surprising, since BALs are generally
thought to be formed in outflows at a much smaller distance from the nucleus.Comment: 34 pages, 11 figures. Accepted by The Astrophysical Journa
XMM-Newton Detection of the Rare FR II BAL Quasar FIRST J101614.3+520916
We have detected FIRST J101614.3+520916 with the XMM-Newton X-ray
Observatory. FIRST J101614.3+520916, one of the most extreme radio-loud, broad
absorption line (BAL) quasars so far discovered, is also a Fanaroff-Riley type
II (FR II) radio source. We find that, compared to its estimated intrinsic
X-ray flux, the observed X-rays are likely suppressed, and that the observed
hardness ratio indicates significant soft X-ray photons. This is inconsistent
with the simplest model, a normal quasar spectrum absorbed by a large neutral
HI column density, which would primarily absorb the softer photons. More
complex models, involving partial covering, an ionized absorber, ionized mirror
reflection, or jet contributions need to be invoked to explain this source. The
suppressed but soft X-ray emission in this radio-loud BAL quasar is consistent
with the behavior displayed by other BAL quasars, both radio-loud and
radio-quiet.Comment: 5 pages, 2 figures. Accepted in AJ. (Typos corrected.
XMM-Newton detection of the rare Fanaroff-Riley type II broad absorption line quasar first J101614.3+520916
We have detected FIRST J101614.3+520916 with the XMM-Newton X-ray observatory. FIRST J101614.3+520916, one of the most extreme radio-loud, broad absorption line (BAL) quasars so far discovered, is also a Fanaroff-Riley type II radio source. We find that, compared to its estimated intrinsic X-ray flux, the observed X-rays are likely suppressed and that the observed hardness ratio indicates significant soft X-ray photons. This is inconsistent with the simplest model, a normal quasar spectrum absorbed by a large neutral H I column density, which would primarily absorb the softer photons. More complex models, involving partial covering, an ionized absorber, ionized mirror reflection, or jet contributions need to be invoked to explain this source. The suppressed but soft X-ray emission in this radio-loud BAL quasar is consistent with the behavior displayed by other BAL quasars, both radio-loud and radio-quiet
The FIRST Bright Quasar Survey. II. 60 Nights and 1200 Spectra Later
We have used the VLA FIRST survey and the APM catalog of the POSS-I plates as
the basis for constructing a new radio-selected sample of optically bright
quasars. This is the first radio-selected sample that is competitive in size
with current optically selected quasar surveys. Using only two basic criteria,
radio-optical positional coincidence and optical morphology, quasars and BL
Lacs can be identified with 60% selection efficiency; the efficiency increases
to 70% for objects fainter than magnitude 17. We show that a more sophisticated
selection scheme can predict with better than 85% reliability which candidates
will turn out to be quasars.
This paper presents the second installment of the FIRST Bright Quasar Survey
with a catalog of 636 quasars distributed over 2682 square degrees. The quasar
sample is characterized and all spectra are displayed. The FBQS detects both
radio-loud and radio-quiet quasars out to a redshift z>3. We find a large
population of objects of intermediate radio-loudness; there is no evidence in
our sample for a bimodal distribution of radio characteristics. The sample
includes ~29 broad absorption line quasars, both high and low ionization, and a
number of new objects with remarkable optical spectra.Comment: 41 pages plus 39 gifs which contain all quasar spectra. Accepted for
publication in the Astrophysical Journal Supplement Serie
HST STIS Observations of PG 0946+301: the Highest Quality UV Spectrum of a BALQSO
We describe deep (40 orbits) HST/STIS observations of the BALQSO PG 0946+301
and make them available to the community. These observations are the major part
of a multi-wavelength campaign on this object aimed at determining the
ionization equilibrium and abundances (IEA) in broad absorption line (BAL)
QSOs. We present simple template fits to the entire data set, which yield firm
identifications for more than two dozen BALs from 18 ions and give lower limits
for the ionic column densities. We find that the outflow's metalicity is
consistent with being solar, while the abundance ratio of phosphorus to other
metals is at least ten times solar. These findings are based on diagnostics
that are not sensitive to saturation and partial covering effects in the BALs,
which considerably weakened previous claims for enhanced metalicity. Ample
evidence for these effects is seen in the spectrum. We also discuss several
options for extracting tighter IEA constraints in future analyses, and present
the significant temporal changes which are detected between these spectra and
those taken by the HST/FOS in 1992.Comment: 32 pages, 7 figures, to appear in ApJ. See also companion paper by
Arav, Korista and De Koo