61 research outputs found
Effects of Electricity and Altered Conductivity on Rainbow Trout Embryos: A Study to Determine Efficacy of Electricity for Eradication of Invasive Salmonids
Electricity has been an applied means of facilitating capture and removal of invasive fishes for many years. Current methods involve use of electrodes to establish a current through which passing fish will be susceptible to a brief shock to stun. This method, however, only affects free swimming individuals and is not inclusive of early life history stages such as embryos within spawning substrate. This study evaluates the susceptibility of embryonic and larval stage rainbow trout (Oncorhynchus mykiss) to direct DC current between 2-20v/cm in varying conductive waters to determine lethality for invasive salmonid eradication efforts. Rainbow trout embryos (n = 10 embryos/exposure) were initially exposed to homogeneous electric fields for 5 sec with a water conductivity of 220uS/cm from 1 day post fertilization (DPF)/ 27 temperature units (TU) to 15 DPF/405TU. Mortality was assessed 24 hours post exposure and the LV50 (lethal voltage) at 220uS/cm was determined for each TU. Embryos from six periods of development were then exposed to their respective LV50 voltages in varying conductive waters (20-600uS/cm). Susceptibility to direct DC voltages increased with voltage but overall susceptibility decreased with development. Susceptibility to a constant voltage increased with increasing conductivity and was consistent throughout early development (81TU-292TU), but the effects of increased conductivity were not enhanced in eyed embryos after 364TU. Results indicate that direct DC current applied prior to eyed embryonic stages, the period of greatest trout embryo susceptibility, is an effective means of eradicating invasive and nuisance salmonids
A Microlensing Accretion Disk Size Measurement in the Lensed Quasar WFI 2026-4536
We use thirteen seasons of R-band photometry from the 1.2m Leonard Euler
Swiss Telescope at La Silla to examine microlensing variability in the
quadruply-imaged lensed quasar WFI 2026-4536. The lightcurves exhibit
of uncorrelated variability across all epochs and a
prominent single feature of within a single season.
We analyze this variability to constrain the size of the quasar's accretion
disk. Adopting a nominal inclination of 60, we find an accretion
disk scale radius of at a
rest-frame wavelength of 2043\,\unicode{xC5}, and we estimate a black hole
mass of , based on the
CIV line in VLT spectra. This size measurement is fully consistent with the
Quasar Accretion Disk Size - Black Hole Mass relation, providing another system
in which the accretion disk is larger than predicted by thin disk theory.Comment: 26 pages, 8 figures, Appendix with data table, pg 12-2
The Most Powerful Lenses in the Universe: Quasar Microlensing as a Probe of the Lensing Galaxy
Optical and X-ray observations of strongly gravitationally lensed quasars
(especially when four separate images of the quasar are produced) determine not
only the amount of matter in the lensing galaxy but also how much is in a
smooth component and how much is composed of compact masses (e.g., stars,
stellar remnants, primordial black holes, CDM sub-halos, and planets). Future
optical surveys will discover hundreds to thousands of quadruply lensed
quasars, and sensitive X-ray observations will unambiguously determine the
ratio of smooth to clumpy matter at specific locations in the lensing galaxies
and calibrate the stellar mass fundamental plane, providing a determination of
the stellar . A modest observing program with a sensitive, sub-arcsecond
X-ray imager, combined with the planned optical observations, can make those
determinations for a large number (hundreds) of the lensing galaxies, which
will span a redshift range of Comment: Astro2020 Science White Pape
THE BOSS EMISSION-LINE LENS SURVEY. IV. SMOOTH LENS MODELS for the BELLS GALLERY SAMPLE
We present \textsl{Hubble Space Telescope} (\textsl{HST}) F606W-band imaging
observations of 21 galaxy-Ly emitter lens candidates in the Baryon
Oscillation Spectroscopic Survey (BOSS) Emission-Line Lens Survey (BELLS) for
GALaxy-Ly EmitteR sYstems (BELLS GALLERY) survey. 17 systems are
confirmed to be definite lenses with unambiguous evidence of multiple imaging.
The lenses are primarily massive early-type galaxies (ETGs) at redshifts of
approximately , while the lensed sources are Ly emitters (LAEs)
at redshifts from 2 to 3. Although the \textsl{HST} imaging data are well fit
by smooth lens models consisting of singular isothermal ellipsoids in an
external shear field, a thorough exploration of dark substructures in the lens
galaxies is required. The Einstein radii of the BELLS GALLERY lenses are on
average larger than those of the BELLS lenses because of the much higher
source redshifts which will allow a detailed investigation of the radius
evolution of the mass profile in ETGs. With the aid of the average lensing magnification, the LAEs are resolved to comprise individual
star-forming knots of a wide range of properties with characteristic sizes from
less than 100 pc to several kpc, rest-frame far UV apparent AB magnitudes from
29.6 to 24.2, and typical projected separations of 500 pc to 2 kpc.Comment: 15 pages, 4 figures, minor edits to match the ApJ published versio
First radial velocity results from the MINiature Exoplanet Radial Velocity Array (MINERVA)
The MINiature Exoplanet Radial Velocity Array (MINERVA) is a dedicated
observatory of four 0.7m robotic telescopes fiber-fed to a KiwiSpec
spectrograph. The MINERVA mission is to discover super-Earths in the habitable
zones of nearby stars. This can be accomplished with MINERVA's unique
combination of high precision and high cadence over long time periods. In this
work, we detail changes to the MINERVA facility that have occurred since our
previous paper. We then describe MINERVA's robotic control software, the
process by which we perform 1D spectral extraction, and our forward modeling
Doppler pipeline. In the process of improving our forward modeling procedure,
we found that our spectrograph's intrinsic instrumental profile is stable for
at least nine months. Because of that, we characterized our instrumental
profile with a time-independent, cubic spline function based on the profile in
the cross dispersion direction, with which we achieved a radial velocity
precision similar to using a conventional "sum-of-Gaussians" instrumental
profile: 1.8 m s over 1.5 months on the RV standard star HD 122064.
Therefore, we conclude that the instrumental profile need not be perfectly
accurate as long as it is stable. In addition, we observed 51 Peg and our
results are consistent with the literature, confirming our spectrograph and
Doppler pipeline are producing accurate and precise radial velocities.Comment: 22 pages, 9 figures, submitted to PASP, Peer-Reviewed and Accepte
Rest-frame UV Properties of Luminous Strong Gravitationally Lensed Ly Emitters from the BELLS GALLERY Survey
We present deep rest-frame UV spectroscopic observations using the Gran
Telescopio Canarias of six gravitationally lensed Lya emitters (LAEs) at
selected from the BELLS GALLERY survey. By taking the
magnifications into account, we show that LAEs can be as luminous as L(Lya) =
30x10 erg s-1 and M(UV) = -23 (AB) without invoking an AGN component, in
contrast with previous findings. We measure Lya rest-frame equivalent widths,
EW(Lya), ranging from 16\AA to 50\AA and Lya escape fractions, fesc(Lya), from
10% to 40%. Large EW(Lya) and fesc(Lya) are found predominantly in LAEs showing
weak low-ionization ISM absorption (EW < 1\AA) and narrow Lya profiles (< 300
km s-1 FWHM) with their peak close (< 80 km s-1) to their systemic redshifts,
suggestive of less scatter from low HI column densities that favours the escape
of Lya photons. We infer stellar metallicities of Z/Zsun ~ 0.2 in almost all
LAEs by comparing the P-Cygni profiles of the wind lines NV1240\AA and
CIV1549\AA with those from stellar synthesis models. We also find a trend
between M(UV) and the velocity offset of ISM absorption lines, such as the most
luminous LAEs experience stronger outflows. The most luminous LAEs show star
formation rates up to 180 Msun yr-1, yet they appear relatively blue
((UV) ~ -1.8 to -2.0) showing evidence of little dust attenuation
(E(B-V) = 0.10-0.14). These luminous LAEs may be particular cases of young
starburst galaxies that have had no time to form large amounts of dust. If so,
they are ideal laboratories to study the early phase of massive star formation,
stellar and dust mass growth, and chemical enrichment histories of starburst
galaxies at high-z.Comment: 23 pages, 10 figures, 6 tables. Accepted for publication in MNRA
KELT-24b: A 5M\u3csub\u3eJ\u3c/sub\u3e Planet on a 5.6 day Well-aligned Orbit around the Young V = 8.3 F-star HD 93148
We present the discovery of KELT-24 b, a massive hot Jupiter orbiting a bright (V = 8.3 mag, K = 7.2 mag) young F-star with a period of 5.6 days. The host star, KELT-24 (HD 93148), has a T eff = K, a mass of M * = M ⊙, a radius of R * = 1.506 ± 0.022 R ⊙, and an age of Gyr. Its planetary companion (KELT-24 b) has a radius of R P = 1.272 ± 0.021 R J and a mass of M P = M J, and from Doppler tomographic observations, we find that the planet\u27s orbit is well-aligned to its host star\u27s projected spin axis (). The young age estimated for KELT-24 suggests that it only recently started to evolve from the zero-age main sequence. KELT-24 is the brightest star known to host a transiting giant planet with a period between 5 and 10 days. Although the circularization timescale is much longer than the age of the system, we do not detect a large eccentricity or significant misalignment that is expected from dynamical migration. The brightness of its host star and its moderate surface gravity make KELT-24b an intriguing target for detailed atmospheric characterization through spectroscopic emission measurements since it would bridge the current literature results that have primarily focused on lower mass hot Jupiters and a few brown dwarfs
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