20 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
KELT-24b: A 5M_J 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) =6508±49 K, a mass of M∗ = 1.461^(+0.056)_(−0.060) M_⊙, radius of R∗ = 1.506±0.022 R_⊙, and an age of 0.77^(+0.61)_(−0.42) Gyr. Its planetary companion (KELT-24 b) has a radius of R_P = 1.272^(+0.021)_(−0.022) R_J, a mass of MP = 5.18^(+0.21)_(−0.22) M_J, and from Doppler tomographic observations, we find that the planet's orbit is well-aligned to its host star's projected spin axis (λ = 2.6^(+5.1)_(−3.6)). 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
Another Shipment of Six Short-Period Giant Planets from TESS
We present the discovery and characterization of six short-period, transiting
giant planets from NASA's Transiting Exoplanet Survey Satellite (TESS) --
TOI-1811 (TIC 376524552), TOI-2025 (TIC 394050135), TOI-2145 (TIC 88992642),
TOI-2152 (TIC 395393265), TOI-2154 (TIC 428787891), & TOI-2497 (TIC 97568467).
All six planets orbit bright host stars (8.9 <G< 11.8, 7.7 <K< 10.1). Using a
combination of time-series photometric and spectroscopic follow-up observations
from the TESS Follow-up Observing Program (TFOP) Working Group, we have
determined that the planets are Jovian-sized (R = 1.00-1.45 R),
have masses ranging from 0.92 to 5.35 M, and orbit F, G, and K stars
(4753 T 7360 K). We detect a significant orbital eccentricity
for the three longest-period systems in our sample: TOI-2025 b (P = 8.872 days,
= ), TOI-2145 b (P = 10.261 days, =
), and TOI-2497 b (P = 10.656 days, =
). TOI-2145 b and TOI-2497 b both orbit subgiant host
stars (3.8 g 4.0), but these planets show no sign of inflation
despite very high levels of irradiation. The lack of inflation may be explained
by the high mass of the planets; M (TOI-2145
b) and M (TOI-2497 b). These six new discoveries
contribute to the larger community effort to use {\it TESS} to create a
magnitude-complete, self-consistent sample of giant planets with
well-determined parameters for future detailed studies.Comment: 20 Pages, 6 Figures, 8 Tables, Accepted by MNRA
Doctor of Philosophy
dissertationOne of the greatest mysteries in modern-day astrophysics is that of the nature and composition of dark matter. Numerous lines of research have sought to detect and characterize this unknown material. Cosmological simulations in particular have proven very successful at re-creating observed large scale structure given a few simple assumptions about dark matter. These simulations, however, become discrepant with observations on smaller scales. Tension between simulations and observations still exists in the predicted abundance of dark matter subhalos: small, gravitationally-bound dark matter halos. These subhalos are believed to host dwarf galaxies in the Milky Way. The observed abundance of dwarf galaxies, however, is too low by an order of magnitude. This thesis describes an observational program to address this tension. Strong gravitational lensing has been demonstrated to have the ability to detect dark matter substructure and empirically test cosmological simulations across large regions of the universe. We propose an extension of current results using a particular class of lensed galaxies known as Lyman-a Emitters (LAEs) to achieve lower mass detection thresholds. Our sample of high-resolution HST images holds the greatest substructure detection power of any to date. We develop the statistical framework to measure the mass fraction and slope of the subhalo mass function (SHMF). Our preliminary results suggest a substructure mass fraction f = 0.0020+0.0027 0.0013 which is lower than previous studies, but consistent with both observational results and theoretical predictions. For the slope we find a = 0.968+0.485 0.524 which is significantly lower than cosmological predictions. Given this tension, we suspect that we are less sensitive to low-mass substructure than high-mass substructure. We propose an alternative analysis that may definitively determine whether this apparent difference is real or an artifact introduced in data reduction. We also discuss the implications for warm dark matter (WDM) if our results hold