70 research outputs found
Observations of quasar host galaxies with laser guide star AO
We report on observations of two quasar host galaxies made with the Lick Observatory adaptive optic system using a laser guide star tuned to the wavelength of the sodium D lines. A brief outline of the system is given, and a description of its performance when obtaining science data. We discuss techniques for obtaining calibration of the point spread function and the analysis steps required to obtain useful scientific results. We present H-band images of quasar host galaxies made with the system. Estimates of the host galaxy magnitudes and central black hole masses were made from these data. These are the first observations of quasar host galaxies with a sodium laser guide star
The Spitzer mid-infrared AGN survey. II-the demographics and cosmic evolution of the AGN population
We present luminosity functions derived from a spectroscopic survey of AGN
selected from Spitzer Space Telescope imaging surveys. Selection in the
mid-infrared is significantly less affected by dust obscuration. We can thus
compare the luminosity functions of the obscured and unobscured AGN in a more
reliable fashion than by using optical or X-ray data alone. We find that the
AGN luminosity function can be well described by a broken power-law model in
which the break luminosity decreases with redshift. At high redshifts
(), we find significantly more AGN at a given bolometric luminosity than
found by either optical quasar surveys or hard X-ray surveys. The fraction of
obscured AGN decreases rapidly with increasing AGN luminosity, but, at least at
high redshifts, appears to remain at \% even at bolometric
luminosities . The data support a picture in which the
obscured and unobscured populations evolve differently, with some evidence that
high luminosity obscured quasars peak in space density at a higher redshift
than their unobscured counterparts. The amount of accretion energy in the
Universe estimated from this work suggests that AGN contribute about 12\% to
the total radiation intensity of the Universe, and a high radiative accretion
efficiency is required to match current
estimates of the local mass density in black holes.Comment: 14 pages, accepted by Ap
Observations of quasar host galaxies with laser guide star AO
We report on observations of two quasar host galaxies made with the Lick Observatory adaptive optic system using a laser guide star tuned to the wavelength of the sodium D lines. A brief outline of the system is given, and a description of its performance when obtaining science data. We discuss techniques for obtaining calibration of the point spread function and the analysis steps required to obtain useful scientific results. We present H-band images of quasar host galaxies made with the system. Estimates of the host galaxy magnitudes and central black hole masses were made from these data. These are the first observations of quasar host galaxies with a sodium laser guide star
Commissioning ShARCS: the Shane Adaptive optics infraRed Camera-Spectrograph for the Lick Observatory 3-m telescope
We describe the design and first-light early science performance of the Shane
Adaptive optics infraRed Camera-Spectrograph (ShARCS) on Lick Observatory's 3-m
Shane telescope. Designed to work with the new ShaneAO adaptive optics system,
ShARCS is capable of high-efficiency, diffraction-limited imaging and
low-dispersion grism spectroscopy in J, H, and K-bands. ShARCS uses a
HAWAII-2RG infrared detector, giving high quantum efficiency (>80%) and Nyquist
sampling the diffraction limit in all three wavelength bands. The ShARCS
instrument is also equipped for linear polarimetry and is sensitive down to 650
nm to support future visible-light adaptive optics capability. We report on the
early science data taken during commissioning.Comment: 9 pages, 7 figures. Presented at SPIE Astronomical Telescopes +
Instrumentation conference, paper 9148-11
Swimming with ShARCS: Comparison of On-sky Sensitivity With Model Predictions for ShaneAO on the Lick Observatory 3-meter Telescope
The Lick Observatory's Shane 3-meter telescope has been upgraded with a new
infrared instrument (ShARCS - Shane Adaptive optics infraRed Camera and
Spectrograph) and dual-deformable mirror adaptive optics (AO) system (ShaneAO).
We present first-light measurements of imaging sensitivity in the Ks band. We
compare measured results to predicted signal-to-noise ratio and magnitude
limits from modeling the emissivity and throughput of ShaneAO and ShARCS. The
model was validated by comparing its results to the Keck telescope adaptive
optics system model and then by estimating the sky background and limiting
magnitudes for IRCAL, the previous infra-red detector on the Shane telescope,
and comparing to measured, published results. We predict that the ShaneAO
system will measure lower sky backgrounds and achieve 20\% higher throughput
across the bands despite having more optical surfaces than the current
system. It will enable imaging of fainter objects (by 1-2 magnitudes) and will
be faster to reach a fiducial signal-to-noise ratio by a factor of 10-13. We
highlight the improvements in performance over the previous AO system and its
camera, IRCAL.Comment: 13 pages, 5 figures, SPIE Astronomical Telescopes + Instrumentation,
Montreal 201
Adaptive Optics Imaging Survey of Luminous Infrared Galaxies
We present high resolution imaging observations of a sample of previously
unidentified far-infrared galaxies at z < 0.3. The objects were selected by
cross-correlating the IRAS Faint Source Catalog with the VLA FIRST catalog and
the HST Guide Star Catalog to allow for adaptive optics observations. We found
two new ULIGs (with L_FIR equal to or greater than 10^{12} L_sun) and 19 new
LIGs (with L_FIR equal to or greater than 10^{11} L_sun). Twenty of the
galaxies in the sample were imaged with either the Lick or Keck adaptive optics
systems in H or K'. Galaxy morphologies were determined using the two
dimensional fitting program GALFIT and the residuals examined to look for
interesting structure. The morphologies reveal that at least 30% are involved
in tidal interactions, with 20% being clear mergers. An additional 50% show
signs of possible interaction. Line ratios were used to determine powering
mechanism; of the 17 objects in the sample showing clear emission lines - four
are active galactic nuclei and seven are starburst galaxies. The rest exhibit a
combination of both phenomena.Comment: 29 pages, 8 figures, accepted for publication in A
Opto-Mechanical Design of ShaneAO: the Adaptive Optics System for the 3-meter Shane Telescope
A Cassegrain mounted adaptive optics instrument presents unique challenges
for opto-mechanical design. The flexure and temperature tolerances for
stability are tighter than those of seeing limited instruments. This criteria
requires particular attention to material properties and mounting techniques.
This paper addresses the mechanical designs developed to meet the optical
functional requirements. One of the key considerations was to have
gravitational deformations, which vary with telescope orientation, stay within
the optical error budget, or ensure that we can compensate with a steering
mirror by maintaining predictable elastic behavior. Here we look at several
cases where deformation is predicted with finite element analysis and Hertzian
deformation analysis and also tested. Techniques used to address thermal
deformation compensation without the use of low CTE materials will also be
discussed.Comment: 14 pages, 14 figures, 4 tables. Presented at SPIE Astronomical
Telescopes + Instrumentation conference, paper 9148-11
Analysis of Neptune's 2017 Bright Equatorial Storm
We report the discovery of a large (8500 km diameter) infrared-bright
storm at Neptune's equator in June 2017. We tracked the storm over a period of
7 months with high-cadence infrared snapshot imaging, carried out on 14 nights
at the 10 meter Keck II telescope and 17 nights at the Shane 120 inch reflector
at Lick Observatory. The cloud feature was larger and more persistent than any
equatorial clouds seen before on Neptune, remaining intermittently active from
at least 10 June to 31 December 2017. Our Keck and Lick observations were
augmented by very high-cadence images from the amateur community, which
permitted the determination of accurate drift rates for the cloud feature. Its
zonal drift speed was variable from 10 June to at least 25 July, but remained a
constant m s from 30 September until at least 15
November. The pressure of the cloud top was determined from radiative transfer
calculations to be 0.3-0.6 bar; this value remained constant over the course of
the observations. Multiple cloud break-up events, in which a bright cloud band
wrapped around Neptune's equator, were observed over the course of our
observations. No "dark spot" vortices were seen near the equator in HST imaging
on 6 and 7 October. The size and pressure of the storm are consistent with
moist convection or a planetary-scale wave as the energy source of convective
upwelling, but more modeling is required to determine the driver of this
equatorial disturbance as well as the triggers for and dynamics of the observed
cloud break-up events.Comment: 42 pages, 14 figures, 6 tables; Accepted to Icaru
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