5 research outputs found
CIV Emission and the Ultraviolet through X-ray Spectral Energy Distribution of Radio-Quiet Quasars
In the restframe UV, two of the parameters that best characterize the range
of emission-line properties in quasar broad emission-line regions are the
equivalent width and the blueshift of the CIV line relative to the quasar rest
frame. We explore the connection between these emission-line properties and the
UV through X-ray spectral energy distribution (SED) for radio-quiet (RQ)
quasars. Our sample consists of a heterogeneous compilation of 406 quasars from
the Sloan Digital Sky Survey and Palomar-Green survey that have well-measured
CIV emission-line and X-ray properties (including 164 objects with measured
Gamma). We find that RQ quasars with both strong CIV emission and small CIV
blueshifts can be classified as "hard-spectrum" sources that are (relatively)
strong in the X-ray as compared to the UV. On the other hand, RQ quasars with
both weak CIV emission and large CIV blueshifts are instead "soft-spectrum"
sources that are (relatively) weak in the X-ray as compared to the UV. This
work helps to further bridge optical/soft X-ray "Eigenvector 1" relationships
to the UV and hard X-ray. Based on these findings, we argue that future work
should consider systematic errors in bolometric corrections (and thus accretion
rates) that are derived from a single mean SED. Detailed analysis of the CIV
emission line may allow for SED-dependent corrections to these quantities.Comment: AJ, in press; 39 pages, 11 figures, 3 table
Unification of Luminous Type 1 Quasars through CIV Emission
Using a sample of 30,000 quasars from SDSS-DR7, we explore the range of
properties exhibited by high-ionization, broad emission lines, such as CIV
1549. Specifically we investigate the anti-correlation between L_UV and
emission line EQW (the Baldwin Effect) and the "blueshifting" of
high-ionization emission lines. The blueshift of the CIV emission line is
nearly ubiquitous, with a mean shift of 810 km/s for radio-quiet (RQ) quasars
and 360 km/s for radio-loud (RL) quasars, and the Baldwin Effect is present in
both RQ and RL samples. Composite spectra are constructed as a function of CIV
emission line properties in attempt to reveal empirical relationships between
different line species and the SED. Within a two-component disk+wind model of
the broad emission line region (BELR), where the wind filters the continuum
seen by the disk component, we find that RL quasars are consistent with being
dominated by the disk component, while BALQSOs are consistent with being
dominated by the wind component. Some RQ objects have emission line features
similar to RL quasars; they may simply have insufficient black hole (BH) spin
to form radio jets. Our results suggest that there could be significant
systematic errors in the determination of L_bol and BH mass that make it
difficult to place these findings in a more physical context. However, it is
possible to classify quasars in a paradigm where the diversity of BELR
parameters are due to differences in an accretion disk wind between quasars
(and over time); these differences are underlain primarily by the SED, which
ultimately must be tied to BH mass and accretion rate.Comment: 51 pages, 18 figures, accepted by AJ, revised version includes
various modifications based on the referee's comment
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The extreme-ultraviolet stellar characterization for atmospheric physics and evolution (ESCAPE) mission concept
The long-term stability of exoplanetary atmospheres depends critically on the extreme-ultraviolet (EUV) flux from the host star. The EUV flux likely controls the demographics of the short-period planet population as well the ability for rocky planets to maintain habitable environments long enough for the emergence of life. We present the Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) mission, an astrophysics Small Explorer proposed to NASA. ESCAPE employs extreme-and far-ultraviolet spectroscopy (70 - 1800 angstrom) to characterize the high-energy radiation environment in the habitable zones (HZs) around nearby stars. ESCAPE provides the first comprehensive study of the stellar EUV environments that control atmospheric mass-loss and determine the habitability of rocky exoplanets. The ESCAPE instrument comprises an EUV grazing incidence telescope feeding four diffraction gratings and a photon-counting detector. The telescope is 50 cm diameter with four nested parabolic primary mirrors and four nested elliptical secondary mirrors, fabricated and aligned by NASA Marshall Space Flight Center and the Smithsonian Astrophysical Observatory. The off-plane grating assemblies are fabricated at Pennsylvania State University and the ESCAPE detector system is a micro-channel plate (MCP; 125mm x 40mm active area) sensor developed by the University of California, Berkeley. ESCAPE employs the versatile and high-heritage Ball Aerospace BCP-100 spacecraft.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]