1,875 research outputs found
The lens and source of the optical Einstein ring gravitational lens ER 0047-2808
(Abridged) We perform a detailed analysis of the optical gravitational lens
ER 0047-2808 imaged with WFPC2 on the Hubble Space Telescope. Using software
specifically designed for the analysis of resolved gravitational lens systems,
we focus on how the image alone can constrain the mass distribution in the lens
galaxy. We find the data are of sufficient quality to strongly constrain the
lens model with no a priori assumptions about the source. Using a variety of
mass models, we find statistically acceptable results for elliptical
isothermal-like models with an Einstein radius of 1.17''. An elliptical
power-law model (Sigma \propto R^-beta) for the surface mass density favours a
slope slightly steeper than isothermal with beta = 1.08 +/- 0.03. Other models
including a constant M/L, pure NFW halo and (surprisingly) an isothermal sphere
with external shear are ruled out by the data. We find the galaxy light profile
can only be fit with a Sersic plus point source model. The resulting total
M/L_B contained within the images is 4.7 h_65 +/-0.3. In addition, we find the
luminous matter is aligned with the total mass distribution within a few
degrees. The source, reconstructed by the software, is revealed to have two
bright regions, with an unresolved component inside the caustic and a resolved
component straddling a fold caustic. The angular size of the entire source is
approx. 0.1'' and its (unlensed) Lyman-alpha flux is 3 x 10^-17 erg/s/cm^2.Comment: 13 pages, 5 figures. Revised version accepted for publication in
MNRA
Correcting CIV-Based Virial Black Hole Masses
The CIV broad emission line is visible in optical spectra to redshifts
exceeding z~5. CIV has long been known to exhibit significant displacements to
the blue and these `blueshifts' almost certainly signal the presence of strong
outflows. As a consequence, single-epoch virial black hole (BH) mass estimates
derived from CIV velocity-widths are known to be systematically biased compared
to masses from the hydrogen Balmer lines. Using a large sample of 230
high-luminosity (log = 45.5-48 erg/s), redshift 1.5<z<4.0 quasars
with both CIV and Balmer line spectra, we have quantified the bias in CIV BH
masses as a function of the CIV blueshift. CIV BH masses are shown to be a
factor of five larger than the corresponding Balmer-line masses at CIV
blueshifts of 3000 km/s and are over-estimated by almost an order of magnitude
at the most extreme blueshifts, >5000 km/s. Using the monotonically increasing
relationship between the CIV blueshift and the mass ratio BH(CIV)/BH(H)
we derive an empirical correction to all CIV BH-masses. The scatter between the
corrected CIV masses and the Balmer masses is 0.24 dex at low CIV blueshifts
(~0 km/s) and just 0.10 dex at high blueshifts (~3000 km/s), compared to 0.40
dex before the correction. The correction depends only on the CIV line
properties - i.e. full-width at half maximum and blueshift - and can therefore
be applied to all quasars where CIV emission line properties have been
measured, enabling the derivation of un-biased virial BH mass estimates for the
majority of high-luminosity, high-redshift, spectroscopically confirmed quasars
in the literature.Comment: Accepted for publication in MNRAS; fixed typo in CIV wavelengt
Warped Phenomenology
We explore the phenomenology associated with the recently proposed localized
gravity model of Randall and Sundrum where gravity propagates in a
5-dimensional non-factorizable geometry and generates the 4-dimensional
weak-Planck scale hierarchy by an exponential function of the compactification
radius, called a warp factor. The Kaluza-Klein tower of gravitons which emerge
in this scenario have strikingly different properties than in the factorizable
case with large extra dimensions. We derive the form of the graviton tower
interactions with the Standard Model fields and examine their direct production
in Drell-Yan and dijet events at the Tevatron and LHC as well as the KK
spectrum line-shape at high-energy linear \epem colliders. In the case where
the first KK excitation is observed, we outline the procedure to uniquely
determine the parameters of this scenario. We also investigate the effect of KK
tower exchanges in contact interaction searches. We find that present
experiments can place meaningful constraints on the parameters of this model.Comment: 14 pages, LaTex, 3 fig
The compact, ∼1 kpc host galaxy of a quasar at a redshift of 7.1
We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [C ii] fine-structure line and the underlying far-infrared (FIR) dust continuum emission in J1120+0641, the most distant quasar currently known (). We also present observations targeting the CO(2–1), CO(7–6), and [C i] 369 μm lines in the same source obtained at the Very Large Array and Plateau de Bure Interferometer. We find a [C ii] line flux of Jy and a continuum flux density of mJy beam−1, consistent with previous unresolved measurements. No other source is detected in continuum or [C ii] emission in the field covered by ALMA (~ 25''). At the resolution of our ALMA observations (0farcs23, or 1.2 kpc, a factor of ~70 smaller beam area compared to previous measurements), we find that the majority of the emission is very compact: a high fraction (~80%) of the total line and continuum flux is associated with a region 1–1.5 kpc in diameter. The remaining ~20% of the emission is distributed over a larger area with radius lesssim4 kpc. The [C ii] emission does not exhibit ordered motion on kiloparsec scales: applying the virial theorem yields an upper limit on the dynamical mass of the host galaxy of , only ~20 × higher than the central black hole (BH). The other targeted lines (CO(2–1), CO(7–6), and [C i]) are not detected, but the limits of the line ratios with respect to the [C ii] emission imply that the heating in the quasar host is dominated by star formation, and not by the accreting BH. The star formation rate (SFR) implied by the FIR continuum is 105–340 , with a resulting SFR surface density of ~100–350 kpc−2, well below the value for Eddington-accretion-limited star formation
Probing Exotic Higgs Sectors in Collisions
I review extended Higgs sectors and constraints thereon arising from
, gauge-coupling unification and b\to s\gam. The couplings and decays
of the Higgs boson eigenstates are outlined for triplet representations. Direct
experimental probes of exotic Higgs bosons are reviewed with a focus on the
important role that would be played by an or collider.Comment: 21 pages, full postscript file is available via anonymous ftp at
ftp://ucdhep.ucdavis.edu/gunion/emem97.ps; one reference adde
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