3,537 research outputs found
Candidate Type II Quasars at 2 < z < 4.3 in the Sloan Digital Sky Survey III
At low redshifts, dust-obscured quasars often have strong yet narrow
permitted lines in the rest-frame optical and ultraviolet, excited by the
central active nucleus, earning the designation Type II quasars. We present a
sample of 145 candidate Type II quasars at redshifts between 2 and 4.3,
encompassing the epoch at which quasar activity peaked in the universe. These
objects, selected from the quasar sample of the Baryon Oscillation
Spectroscopic Survey of the Sloan Digital Sky Survey III, are characterized by
weak continuum in the rest-frame ultraviolet (typical continuum magnitude of i
\approx 22) and strong lines of CIV and Ly \alpha, with Full Width at Half
Maximum less than 2000 kms-1. The continuum magnitudes correspond to an
absolute magnitude of -23 or brighter at redshift 3, too bright to be due
exclusively to the host galaxies of these objects. Roughly one third of the
objects are detected in the shorter-wavelength bands of the WISE survey; the
spectral energy distributions (SEDs) of these objects appear to be intermediate
between classic Type I and Type II quasars seen at lower redshift. Five objects
are detected at rest frame 6\mu m by Spitzer, implying bolometric luminosities
of several times 10^46 erg s-1. We have obtained polarization measurements for
two objects; they are roughly 3% polarized. We suggest that these objects are
luminous quasars, with modest dust extinction (A_V ~ 0.5 mag), whose
ultraviolet continuum also includes a substantial scattering contribution.
Alternatively, the line of sight to the central engines of these objects may be
partially obscured by optically thick material.Comment: 26 pages, 13 figures, 10 tables, 4 machine readable tables. Accepted
for publication in MNRA
Increasing task behavior in a language arts program by providing reinforcement
The work of retarded readers using a programmed language arts curriculum was observed under various conditions of reinforcement in a controlled classroom. Task behavior was followed by conditions of no consequence, teacher praise, a work-break consequence, a monetary consequence and feedback on amount of work (relative to previous work). Extinction of task behavior tended to occur under conditions of no consequence and of teacher praise. Conditions of monetary consequence and of feedback on progress resulted in high, sustained rates of work behavior.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32918/1/0000299.pd
Type II Quasars from the Sloan Digital Sky Survey: V. Imaging host galaxies with the Hubble Space Telescope
Type II quasars are luminous Active Galactic Nuclei whose centers are
obscured by large amounts of gas and dust. In this paper we present 3-band HST
images of nine type II quasars with redshifts 0.2 < z < 0.4 selected from the
Sloan Digital Sky Survey based on their emission line properties. The intrinsic
luminosities of these AGN are estimated to be -24 > M_B > -26, but optical
obscuration allows their host galaxies to be studied unencumbered by bright
nuclei. Each object has been imaged in three continuum filters (`UV', `blue'
and `yellow') placed between the strong emission lines. The spectacular, high
quality images reveal a wealth of details about the structure of the host
galaxies and their environments. Six of the nine galaxies in the sample are
ellipticals with de Vaucouleurs light profiles, one object has a well-defined
disk component and the remaining two have marginal disks. Stellar populations
of type II quasar hosts are more luminous (by a median of 0.3-0.7 mag,
depending on the wavelength) and bluer (by about 0.4 mag) than are M* galaxies
at the same redshift. When smooth fits to stellar light are subtracted from the
images, we find both positive and negative residuals that become more prominent
toward shorter wavelengths. We argue that the negative residuals are due to
kpc-scale dust obscuration, while most positive residuals are due to the light
from the nucleus scattered off interstellar material in the host galaxy.
Scattered light makes a significant contribution to the broad band continuum
emission and can be the dominant component of the extended emission in the UV
in extreme cases.Comment: 51 pages, including 12 grey scale figures, 4 color figures, 5 tables.
In press in AJ. Version with higher-resolution images available at
http://www.astro.princeton.edu/~nadia/qso2.html. (Minor changes in response
to the referee report
Energy-efficient polymeric gas separation membranes for a sustainable future: A review
AbstractOver the past three decades, polymeric gas separation membranes have become widely used for a variety of industrial gas separations applications. This review presents the fundamental scientific principles underpinning the operation of polymers for gas separations, including the solution-diffusion model and various structure/property relations, describes membrane fabrication technology, describes polymers believed to be used commercially for gas separations, and discusses some challenges associated with membrane materials development. A description of new classes of polymers being considered for gas separations, largely to overcome existing challenges or access applications that are not yet practiced commercially, is also provided. Some classes of polymers discussed in this review that have been the focus of much recent work include thermally rearranged (TR) polymers, polymers of intrinsic microporosity (PIMs), room-temperature ionic liquids (RTILs), perfluoropolymers, and high-performance polyimides
Additional Ultracool White Dwarfs Found in the Sloan Digital Sky Survey
We identify seven new ultracool white dwarfs discovered in the Sloan Digital
Sky Survey (SDSS). The SDSS photometry, spectra, and proper motions are
presented, and additional BVRI data are given for these and other previously
discovered ultracool white dwarfs. The observed colors span a remarkably wide
range, qualitatively similar to colors predicted by models for very cool white
dwarfs. One of the new stars (SDSS J1251+44) exhibits strong collision-induced
absorption (CIA) in its spectra, while the spectra and colors of the other six
are consistent with mild CIA. Another of the new discoveries (SDSS J2239+00A)
is part of a binary system -- its companion is also a cool white dwarf, and
other data indicate that the companion exhibits an infrared flux deficiency,
making this the first binary system composed of two CIA white dwarfs. A third
discovery (SDSS J0310-00) has weak Balmer emission lines. The proper motions of
all seven stars are consistent with membership in the disk or thick disk.Comment: Accepted for Astrophysical Journal. 16 pages (includes 3 figures
Four-shooter: a large format charge-coupled-device camera for the Hale telescope
We describe an astronomical camera for the 200-in. Hale telescope using four 800 X800 Texas Instruments CCDs in an optical arrangement that allows imaging of a contiguous 1600-pixel-square region of sky. The system employs reimaging optics to yield a scale of 0.33 arcsec per pixel, a good match to the best seeing conditions at Palomar Observatory. Modern high-efficiency coatings are used in the complex optical system to yield a throughput at peak efficiency of nearly 50% (including the losses in the telescope), corresponding to a quantum efficiency on the sky of about 30%. The system uses a fifth CCD in a spectroscopic channel, and it is possible to obtain simultaneous imaging and spectroscopic observations with the system. The camera may also be used in a scanning mode, in which the telescope tracking rate is offset, and the charge is clocked in the chips in such a manner as to keep the charge image aligned with the optical image. In this way, a survey for high-redshift quasars has been carried out over a large area of sky. The instrument has produced images for the most distant clusters of galaxies yet discovered as well as spectra of the most distant galaxies yet observed
Effect of using an auditory trainer on the attentional, language, and social behaviors of autistic children
Two groups of seven autistic children wore an auditory trainer for an average of 24 minutes per day over two 5- week periods interspersed with 5-week control periods in a time series design. Videotapes were coded for three attentional states (normal, withdrawn, attacking), for verbalization and signing, and for appropriate and acceptable behaviors. Results demonstrated a decrease in time spent withdrawn and increases in signing and in schoolappropriate behavior. Results are interpreted as congruent with Katz's theory of reduced attention due to deficits in auditory conductance .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44599/1/10803_2005_Article_BF01531499.pd
Discovery of Four Gravitationally Lensed Quasars from the Sloan Digital Sky Survey
We present the discovery of four gravitationally lensed quasars selected from
the spectroscopic quasar catalog of the Sloan Digital Sky Survey. We describe
imaging and spectroscopic follow-up observations that support the lensing
interpretation of the following four quasars: SDSS J0832+0404 (image separation
\theta=1.98", source redshift z_s=1.115, lens redshift z_l=0.659); SDSS
J1216+3529 (\theta=1.49", z_s=2.012); SDSS J1322+1052 (\theta=2.00",
z_s=1.716); and SDSS J1524+4409 (\theta=1.67", z_s=1.210, z_l=0.320). Each
system has two lensed images. We find that the fainter image component of SDSS
J0832+0404 is significantly redder than the brighter component, perhaps because
of differential reddening by the lensing galaxy. The lens potential of SDSS
J1216+3529 might be complicated by the presence of a secondary galaxy near the
main lensing galaxy.Comment: 25 pages, 10 figures, 6 tables, accepted for publication in A
Broad Absorption Line Variability in Repeat Quasar Observations from the Sloan Digital Sky Survey
We present a time-variability analysis of 29 broad absorption line quasars
(BALQSOs) observed in two epochs by the Sloan Digital Sky Survey (SDSS). These
spectra are selected from a larger sample of BALQSOs with multiple observations
by virtue of exhibiting a broad CIV 1549 absorption trough separated
from the rest frame of the associated emission peak by more than 3600 km
s. Detached troughs facilitate higher precision variability
measurements, since the measurement of the absorption in these objects is not
complicated by variation in the emission line flux. We have undertaken a
statistical analysis of these detached-trough BALQSO spectra to explore the
relationships between BAL features that are seen to vary and the dynamics of
emission from the quasar central engine. We have measured variability within
our sample, which includes three strongly variable BALs. We have also verified
that the statistical behavior of the overall sample agrees with current model
predictions and previous studies of BAL variability. Specifically, we observe
that the strongest BAL variability occurs among the smallest equivalent width
features and at velocities exceeding 12,000 km s, as predicted by recent
disk-wind modeling.Comment: 11 pages, 7 figures. Accepted for publication in Ap
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