65 research outputs found
Refining the M_BH-V_c scaling relation with HI rotation curves of water megamaser galaxies
Black hole - galaxy scaling relations provide information about the
coevolution of supermassive black holes and their host galaxies. We compare the
black hole mass - circular velocity (MBH - Vc) relation with the black hole
mass - bulge stellar velocity dispersion (MBH - sigma) relation, to see whether
the scaling relations can passively emerge from a large number of mergers, or
require a physical mechanism, such as feedback from an active nucleus. We
present VLA H I observations of five galaxies, including three water megamaser
galaxies, to measure the circular velocity. Using twenty-two galaxies with
dynamical MBH measurements and Vc measurements extending to large radius, our
best-fit MBH - Vc relation, log MBH = alpha + beta log(Vc /200 km s^-1), yields
alpha = 7.43+/-0.13, beta = 3.68+1.23/-1.20, and intrinsic scatter epsilon_int
= 0.51+0.11/-0.09. The intrinsic scatter may well be higher than 0.51, as we
take great care to ascribe conservatively large observational errors. We find
comparable scatter in the MBH - sigma relations, epsilon_int = 0.48+0.10/-0.08,
while pure merging scenarios would likely result in a tighter scaling with the
dark halo (as traced by Vc) than baryonic (sigma) properties. Instead, feedback
from the active nucleus may act on bulge scales to tighten the MBH - sigma
relation with respect to the MBH - Vc relation, as observed.Comment: 27 pages, 15 figures, ApJ accepte
FIREBALL: Detector, data acquisition and reduction
The Faint Intergalactic Redshifted Emission Balloon (FIREBALL) had its first scientific flight in June 2009. The instrument combines microchannel plate detector technology with fiber-fed integral field spectroscopy on an unstable stratospheric balloon gondola platform. This unique combination poses a series of calibration and data reduction challenges that must be addressed and resolved to allow for accurate data analysis. We discuss our approach and some of the methods we are employing to accomplish this task
FIREBALL: Instrument pointing and aspect reconstruction
The Faint Intergalactic Redshifted Emission Balloon (FIREBALL) had its first scientific flight in June 2009. The instrument is a 1 meter class balloon-borne telescope equipped with a vacuum-ultraviolet integral field spectrograph intended to detect emission from the inter-galactic medium at redshifts 0.3 < z < 1.0. The scientific goals and the challenging environment place strict constraints on the pointing and tracking systems of the gondola. In this manuscript we briefly review our pointing requirements, discuss the methods and solutions used to meet those requirements, and present the aspect reconstruction results from the first successful scientific flight
Design and construction progress of LRS2-B: a new low resolution integral field spectrograph for the Hobby-Eberly Telescope
The upcoming Wide-Field Upgrade (WFU) has ushered in a new era of
instrumentation for the Hobby-Eberly Telescope (HET). Here, we present the
design, construction progress, and lab tests completed to date of the
blue-optimized second generation Low Resolution Spectrograph (LRS2-B). LRS2-B
is a dual-channel, fiber fed instrument that is based on the design of the
Visible Integral Field Replicable Unit Spectrograph (VIRUS), which is the new
flagship instrument for carrying out the HET Dark Energy eXperiment (HETDEX).
LRS2-B utilizes a microlens-coupled integral field unit (IFU) that covers a
7"x12" area on the sky having unity fill-factor with ~300 spatial elements that
subsample the median HET image quality. The fiber feed assembly includes an
optimized dichroic beam splitter that allows LRS2-B to simultaneously observe
370 nm to 470 nm and 460 nm to 700 nm at fixed resolving powers of R \approx
1900 and 1200, respectively. We discuss the departures from the nominal VIRUS
design, which includes the IFU, fiber feed, camera correcting optics, and
volume phase holographic grisms. Additionally, the motivation for the selection
of the wavelength coverage and spectral resolution of the two channels is
briefly discussed. One such motivation is the follow-up study of spectrally and
(or) spatially resolved Lyman-alpha emission from z ~ 2.5 star-forming galaxies
in the HETDEX survey. LRS2-B is planned to be a commissioning instrument for
the HET WFU and should be on-sky during quarter 4 of 2013. Finally, we mention
the current state of LRS2-R, the red optimized sister instrument of LRS2-B.Comment: 22 pages, 12 figures, 2 tables. To be published in Proc. SPIE, 2012,
"Ground-Based and Airborne Instrumentation for Astronomy IV", 8446-103. In
v2, a note has been added indicating that this paper has been superseded by
arXiv:1407:601
Mass production of volume phase holographic gratings for the VIRUS spectrograph array
The Visible Integral-field Replicable Unit Spectrograph (VIRUS) is a baseline
array of 150 copies of a simple, fiber-fed integral field spectrograph that
will be deployed on the Hobby-Eberly Telescope (HET). VIRUS is the first
optical astronomical instrument to be replicated on an industrial scale, and
represents a relatively inexpensive solution for carrying out large-area
spectroscopic surveys, such as the HET Dark Energy Experiment (HETDEX). Each
spectrograph contains a volume phase holographic (VPH) grating with a 138 mm
diameter clear aperture as its dispersing element. The instrument utilizes the
grating in first-order for 350-550 nm. Including witness samples, a suite of
170 VPH gratings has been mass produced for VIRUS. Here, we present the design
of the VIRUS VPH gratings and a discussion of their mass production. We
additionally present the design and functionality of a custom apparatus that
has been used to rapidly test the first-order diffraction efficiency of the
gratings for various discrete wavelengths within the VIRUS spectral range. This
device has been used to perform both in-situ tests to monitor the effects of
adjustments to the production prescription as well as to carry out the final
acceptance tests of the gratings' diffraction efficiency. Finally, we present
the as-built performance results for the entire suite of VPH gratings.Comment: 16 pages, 11 figures, 2 tables. To be published in Proc. SPIE, 2014,
"Advances in Optical and Mechanical Technologies for Telescopes and
Instrumentation", 9151-53. The work presented in this article follows from
arXiv:1207:448
FIREBALL: the first ultraviolet fiber fed spectrograph
FIREBall (the Faint Intergalactic Redshifted Emission Balloon) is a balloon-borne 1m telescope coupled to an ultraviolet fiber-fed spectrograph. FIREBall is designed to study the faint and diffuse emission of the warm hot intergalactic medium, until now detected primarily in absorption. FIREBall is a pathfinding mission to test new technology and make new constraints on the temperature and density of this gas. FIREBall has flown twice, the most recent flight (June 2009) a fully functioning science flight. Here we describe the spectrograph design, current setup, and calibration measurements from the campaign
The Influence of Motion and Stress on Optical Fibers
We report on extensive testing carried out on the optical fibers for the
VIRUS instrument. The primary result of this work explores how 10+ years of
simulated wear on a VIRUS fiber bundle affects both transmission and focal
ratio degradation (FRD) of the optical fibers. During the accelerated lifetime
tests we continuously monitored the fibers for signs of FRD. We find that
transient FRD events were common during the portions of the tests when motion
was at telescope slew rates, but dropped to negligible levels during rates of
motion typical for science observation. Tests of fiber transmission and FRD
conducted both before and after the lifetime tests reveal that while
transmission values do not change over the 10+ years of simulated wear, a clear
increase in FRD is seen in all 18 fibers tested. This increase in FRD is likely
due to microfractures that develop over time from repeated flexure of the fiber
bundle, and stands in contrast to the transient FRD events that stem from
localized stress and subsequent modal diffusion of light within the fibers.
There was no measurable wavelength dependence on the increase in FRD over 350
nm to 600 nm. We also report on bend radius tests conducted on individual
fibers and find the 266 microns VIRUS fibers to be immune to bending-induced
FRD at bend radii of R > 10cm. Below this bend radius FRD increases slightly
with decreasing radius. Lastly, we give details of a degradation seen in the
fiber bundle currently deployed on the Mitchell Spectrograph (formally VIRUS-P)
at McDonald Observatory. The degradation is shown to be caused by a localized
shear in a select number of optical fibers that leads to an explosive form of
FRD. In a few fibers, the overall transmission loss through the instrument can
exceed 80%.Comment: 19 pages, 22 figure
The FIREBall fiber-fed UV spectrograph
FIREBall (Faint Intergalactic Redshifted Emission Balloon) had a successful first engineering flight in July of 2007 from Palestine, Texas. Here we detail the design and construction of the spectrograph. FIREBall consists of a 1m telescope coupled to a fiber-fed ultraviolet spectrograph flown on a short duration balloon. The spectrograph is designed to map hydrogen and metal line emission from the intergalactic medium at several redshifts below z=1, exploiting a small window in atmospheric oxygen absorption at balloon altitudes. The instrument is a wide-field IFU fed by almost 400 fibers. The Offner mount spectrograph is designed to be sensitive in the 195-215nm window accessible at our altitudes of 35-40km. We are able to observe Lyα, as well as OVI and CIV doublets, from 0.3 < z < 0.9. Observations of UV bright B stars and background measurements allow characterization of throughput for the entire system and will inform future flights
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