Fletcher Waller
A5101400614- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Isotope Analysis in Ecology
- Planetary Science and Exploration
- Nuclear Physics and Applications
- Blind Source Separation Techniques
- Atmospheric Ozone and Climate
- Space Exploration and Technology
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- History and Developments in Astronomy
- Astronomical Observations and Instrumentation
- Adaptive optics and wavefront sensing
University of Victoria
2022-2024
Herzberg Institute of Astrophysics
2024
Gemini South Observatory
2023
Abstract The Gemini High Resolution Optical Spectrograph (GHOST) is a fiber-fed spectrograph system on the South telescope that provides simultaneous wavelength coverage from 348 to 1061 nm, and designed for optimal performance between 363 950 nm. It can observe up two objects simultaneously in 7.′5 diameter field of regard at R ≃ 56,000 or single object 75,000. spectral resolution modes are obtained by using integral units image slice 1.″2 aperture factor five width 19 fibers high mode...
ABSTRACT This study focuses on Pristine$\_180956.78$−294759.8 (hereafter P180956, [Fe/H] = −1.95 ± 0.02), a star selected from the Pristine Inner Galaxy Survey (PIGS), and followed-up with recently commissioned Gemini High-resolution Optical SpecTrograph (GHOST) at South telescope. The GHOST spectrograph’s high efficiency in blue spectral region (3700−4800 Å) enables detection of elemental tracers early supernovae (e.g. Al, Mn, Sr, Eu). exhibits chemical signatures resembling those found...
ABSTRACT Gaia EDR3 data were used to identify potential members in the outskirts of three ultra-faint dwarf (UFD) galaxies: Coma Berenices (>2Rh), Ursa Major I (∼4Rh), and Boötes as well a new member central region I. These targets observed with Gemini GRACES spectrograph, which was determine precision radial velocities metallicities that confirm their associations UFD galaxies. The spectra also measure absorption lines for 10 elements (Na, Mg, K, Ca, Sc, Ti, Cr, Fe, Ni, Ba), chemical...
ABSTRACT The investigation of the metal-poor tail in Galactic bulge provides unique information on early Milky Way assembly and evolution. A chemo-dynamical analysis 17 very stars (VMP, [Fe/H]<−2.0) selected from Pristine Inner Galaxy Survey was carried out based Gemini/GRACES spectra. chemistry suggests that majority our are similar to halo. Orbits calculated Gaia EDR3 imply these brought into during earliest assembly. Most have large [Na,Ca/Mg] abundances, thus show little evidence...
Abstract The Gemini High-resolution Optical SpecTrograph (GHOST) is the newest high-resolution spectrograph to be developed for a large-aperture telescope, recently deployed and commissioned at Gemini-South telescope. In this paper, we present first science results from GHOST taking during its commissioning runs. We have observed bright metal-poor benchmark star HD 122563, along with two stars in ultrafaint dwarf galaxy Reticulum II (Ret ii ), one of which was previously identified as...
Abstract We report on a chemo-dynamical analysis of SPLUS J142445.34−254247.1 (SPLUS J1424−2542), an extremely metal-poor halo star enhanced in elements formed by the rapid neutron-capture process ( r -process). This was first selected as candidate from its narrowband S-PLUS photometry and followed up spectroscopically medium resolution with Gemini-South/GMOS, which confirmed low-metallicity status. High-resolution spectroscopy gathered GHOST at Gemini-South, allowing for determination...
ABSTRACT Pristine_183.6849 + 04.8619 (P1836849) is an extremely metal-poor ([Fe/H] = −3.3 ± 0.1) star on a prograde orbit confined to the Galactic disc. Such stars are rare and may have their origins in protogalactic fragments that formed early Milky Way, low-mass satellites accreted later, or forming situ plane. Here, we present chemo-dynamical analysis of spectral features between 3700−11 000 Å from high-resolution spectrum taken during Science Verification new Gemini High-resolution...
ABSTRACT Dwarf galaxies are valuable laboratories for dynamical studies related to dark matter and galaxy evolution, yet it is currently unknown just how physically extended their stellar components are. Satellites orbiting the Galaxy’s potential may undergo tidal stripping by host, or alternatively, themselves have accreted smaller systems whose debris populates dwarf’s own halo. Evidence of these past interactions, if present, best searched in outskirts satellite. However, foreground...
Abstract The Gemini South telescope is now equipped with a new high-resolution spectrograph called the High-resolution Optical SpecTrograph (GHOST). This instrument provides high-efficiency, spectra covering 347–1060 nm in single exposure of either one or two targets simultaneously, along precision radial velocity spectroscopy utilizing an internal calibration source. It can operate at spectral element resolving power 76,000 56,000, and reach signal-to-noise ratio ∼5 1 hr on V ∼ 20.8 mag...
ABSTRACT The Gemini High-resolution Optical SpecTrograph (GHOST) is a new Echelle spectrograph available on the Gemini-South telescope as of Semester 2024A. We present first high-resolution spectrum quasar J1449−1227 (redshift zem = 3.27) using data taken during commissioning GHOST. observed hosts an intervening iron-poor {[Fe/H] −2.5} damped Lyman α system (DLA) at redshift z 2.904. Taking advantage high spectral resolving power GHOST (R ≈ 55 000), we are able to accurately model metal...
he Gemini High-Resolution Optical SpecTrograph (GHOST) is a fibre-fed echelle spectrograph recently commissioned at Gemini-South. It has wide variety of observing modes tuned for range science cases, which contribute to number unique data reduction challenges. In this paper, we describe the state GHOST pipeline and application during commissioning phase
Abstract With high equilibrium temperatures and tidally locked rotation, ultra-hot Jupiters (UHJs) are unique laboratories within which to probe extreme atmospheric physics chemistry. In this paper, we present high-resolution dayside spectroscopy of the UHJ WASP-189 b obtained with new Gemini High-resolution Optical SpecTrograph (GHOST) at South Observatory. The observations, cover 3 hr post-eclipse orbital phases, were during instrument’s System Verification run. We detect planet’s...
The Gemini High Resolution Optical Spectrograph (GHOST) is the next generation high resolution spectrograph for South Observatory, and this has recently been commissioned in May 2021. In a single exposure, it can obtain full optical spectrum from blueward of 360nm to beyond 1 micron. Two modes operation mean that either one object be observed at R~80000, or two objects R~55000. First light results have tested all aspects scientific performance GHOST science user perspective, including range...
The Gemini High-resolution Optical SpecTrograph (GHOST) is the newest high resolution spectrograph to be developed for a large aperture telescope, recently deployed and commissioned at Gemini-South telescope. In this paper, we present first science results from GHOST taking during its commissioning runs. We have observed bright metal-poor benchmark star HD 122563, along with two stars in ultra faint dwarf galaxy, Ret II, one of which was previously identified as candidate member, but did not...
The Gemini High Resolution Optical Spectrograph (GHOST) is a fiber-fed spectrograph system on the South telescope that provides simultaneous wavelength coverage from 348 - 1061nm, and designed for optimal performance between 363 950nm. It can observe up to two objects simultaneously in 7.5 arcmin diameter field of regard at R = 56,000 or single object 75,000. spectral resolution modes are obtained by using integral units image slice 1.2" aperture factor five width 19 fibers high mode three 7...
The Gemini High-resolution Optical SpecTrograph (GHOST) is a new echelle spectrograph available on the Gemini-South telescope as of Semester 2024A. We present first high resolution spectrum quasar J1449-1227 (redshift z_em=3.27) using data taken during commissioning GHOST. observed hosts an intervening iron-poor ([Fe/H] = -2.5) damped Lyman alpha (DLA) system at redshift z=2.904. Taking advantage spectral resolving power GHOST (R~55000), we are able to accurately model metal absorption lines...
The Gemini South telescope is now equipped with a new high-resolution spectrograph called GHOST (the High-resolution Optical SpecTrograph). This instrument provides high-efficiency, spectra covering 347-1060 nm in single exposure of either one or two targets simultaneously, along precision radial velocity spectroscopy utilizing an internal calibration source. It can operate at spectral element resolving power 76000 56000, and reach SNR$\sim$5 1hr on V$\sim$20.8 mag target median site seeing,...
With high equilibrium temperatures and tidally locked rotation, ultra-hot Jupiters (UHJs) are unique laboratories within which to probe extreme atmospheric physics chemistry. In this paper, we present high-resolution dayside spectroscopy of the UHJ WASP-189b obtained with new Gemini High-resolution Optical SpecTrograph (GHOST) at South Observatory. The observations, cover three hours post-eclipse orbital phases, were during instrument's System Verification run. We detect planet's atmosphere...
This study focuses on Pristine$\_180956.78$$-$$294759.8$ (hereafter P180956, $[Fe/H] =-1.95\pm0.02$), a star selected from the Pristine Inner Galaxy Survey (PIGS), and followed-up with recently commissioned Gemini High-resolution Optical SpecTrograph (GHOST) at South telescope. The GHOST spectrograph's high efficiency in blue spectral region ($3700-4800$~\AA) enables detection of elemental tracers early supernovae (\eg Al, Mn, Sr, Eu). exhibits chemical signatures resembling those found...
Dwarf galaxies are valuable laboratories for dynamical studies related to dark matter and galaxy evolution, yet it is currently unknown just how physically extended their stellar components are. Satellites orbiting the Galaxy's potential may undergo tidal stripping by host, or alternatively, themselves have accreted smaller systems whose debris populates dwarf's own halo. Evidence of these past interactions, if present, best searched in outskirts satellite. However, foreground contamination...
Gaia EDR3 data was used to identify potential members in the outskirts of three ultra faint dwarf (UFD) galaxies; Coma Berenices (> 2Rh), Ursa Major I ($\sim$ 4Rh), and Boötes as well a new member central region I. These targets were observed with Gemini GRACES spectrograph, which determine precision radial velocities metallicities that confirm their associations UFD galaxies. The spectra also measure absorption lines for 10 elements (Na, Mg, K, Ca, Sc, Ti, Cr, Fe, Ni, Ba), chemical...
Pristine_183.6849+04.8619 (P1836849) is an extremely metal-poor ([Fe/H]$=-3.3\pm0.1$) star on a prograde orbit confined to the Galactic disk. Such stars are rare and may have their origins in protogalactic fragments that formed early Milky Way, low mass satellites accreted later, or forming situ plane. Here we present chemo-dynamical analysis of spectral features between $3700-11000$\r{A} from high-resolution spectrum taken during Science Verification new Gemini High-resolution Optical...
We report on the chemo-dynamical analysis of SPLUS J142445.34-254247.1, an extremely metal-poor halo star enhanced in elements formed by rapid neutron-capture process. This was first selected as a candidate from its narrow-band S-PLUS photometry and followed up spectroscopically medium-resolution with Gemini South/GMOS, which confirmed low-metallicity status. High-resolution spectroscopy gathered GHOST at South, allowing for determination chemical abundances 36 elements, carbon to thorium....
The investigation of the metal-poor tail in Galactic bulge provides unique information on early Milky Way assembly and evolution. A chemo-dynamical analysis 17 very stars (VMP, [Fe/H] $<-2.0$) selected from Pristine Inner Galaxy Survey was carried out based Gemini/GRACES spectra. chemistry suggests that majority our are similar to halo. Orbits calculated {\it Gaia} EDR3 imply these brought into during earliest assembly. Most have large [Na,Ca/Mg] abundances, thus show little evidence...