5 research outputs found
Joint Strong and Weak Lensing Analysis of the Massive Cluster Field J0850+3604
We present a combined strong and weak lensing analysis of the
J085007.6+360428 (J0850) field, which was selected by its high projected
concentration of luminous red galaxies and contains the massive cluster Zwicky
1953. Using Subaru/Suprime-Cam imaging and
MMT/Hectospec spectroscopy, we first perform a weak lensing shear analysis to
constrain the mass distribution in this field, including the cluster at and a smaller foreground halo at . We then add a strong
lensing constraint from a multiply-imaged galaxy in the imaging data with a
photometric redshift of . Unlike previous cluster-scale lens
analyses, our technique accounts for the full three-dimensional mass structure
in the beam, including galaxies along the line of sight. In contrast with past
cluster analyses that use only lensed image positions as constraints, we use
the full surface brightness distribution of the images. This method predicts
that the source galaxy crosses a lensing caustic such that one image is a
highly-magnified "fold arc", which could be used to probe the source galaxy's
structure at ultra-high spatial resolution ( pc). We calculate the mass
of the primary cluster to be with a concentration of , consistent with the mass-concentration relation of
massive clusters at a similar redshift. The large mass of this cluster makes
J0850 an excellent field for leveraging lensing magnification to search for
high-redshift galaxies, competitive with and complementary to that of
well-studied clusters such as the HST Frontier Fields.Comment: Accepted for publication in The Astrophysical Journal; 14 pages, 13
figures, 3 table
The z=0.54 LoBAL Quasar SDSS J085053.12+445122.5: II. The Nature of Partial Covering in the Broad-Absorption-Line Outflow
It has been known for 20 years that the absorbing gas in broad absorption
line quasars does not completely cover the continuum emission region, and that
partial covering must be accounted for to accurately measure the column density
of the outflowing gas. However, the nature of partial covering itself is not
understood. Extrapolation of the SimBAL spectral synthesis model of the HST COS
UV spectrum from SDSS J0850+4451 reported by Leighly et al. 2018 to
non-simultaneous rest-frame optical and near-infrared spectra reveals evidence
that the covering fraction has wavelength dependence, and is a factor of 2.5
times higher in the UV than in the optical and near-infrared bands. The
difference in covering fraction can be explained if the outflow consists of
clumps that are small and either structured or clustered relative to the
projected size of the UV continuum emission region, and have a more diffuse
distribution on size scales comparable to the near-infrared continuum emission
region size. The lower covering fraction over the larger physical area results
in a reduction of the measured total column density by a factor of 1.6 compared
with the UV-only solution. This experiment demonstrates that we can compare
rest-frame UV and near-infrared absorption lines, specifically HeI*10830, to
place constraints on the uniformity of absorption gas in broad absorbing line
quasars.Comment: Revised version after responding to referee repor