GHOST System Verification | Gemini Observatory

News

5 Sep 2023: The special GHOST Shared Risk Call for Proposals through FastTurnaround has been issued. Proposal deadline is 30 Sept at 12:00 noon (HST), for observations during the GHOST run 30 November - 19 December.
1 Sep 2023: Reduced data from the SV run is expected to become available in the archive starting 6 Sept. These were reduced with v0.9.4 and v1.0.0 of the GHOST DR pipeline using DRAGONS 3.0. Note that new installations of the DR software may not yet be possible, and further updates to the DR pipeline may still be possible ahead of the shared risk observations. The reduced spectrophotometric standard observations are the _standard.fits files. In the _dragons.fits files, all the orders have been stitched together with the wavelength on a log-linear scale, calibrated to in-air wavelengths, and corrected for barycentric motion. Sky subtraction was also performed. The _calibrated.fits files are the reduced spectra before stitching the orders and the format of the file is more complex.
31 Aug 2023: The special GHOST Shared-risk call for proposals through Fast Turnaround is expected to be out Tuesday September 5.
12 Jul 2023: Evaluations of the data are being posted as they are received. Check below in the science section for these. The reduced data will be made available on the archive after a couple issues with the data reduction pipeline are resolved.
12 Jul 2023: There will be a series of GHOST webinars in late July/early August to help introduce GHOST to the community and present results of this SV process. For more information and to sign up, check the webinar page.
14 Jun 2023: Raw data from the SV run are becoming publicly available from the archive. All data should be available by 18 June.
24 May 2023: Details of the observations taken during the SV run are provided below .
18 May 2023: The successful SV run (May 9-17) has just concluded! High priority observations from most of the programs were completed. Details of the observations will be provided below in the coming week. Raw data will be publicly available from the archive one month from the date taken.
9 May 2023: Observations are being taken for the GHOST SV run which started tonight. Science cases are listed here. Raw data will be released 1 month after it is observed.

Introduction

A GHOST System Verification (SV) observing run is planned for May 2023. The purpose of this run is to:

Perform end-to-end testing of the software, documentation, and operational procedures to prepare for larger scale deployment (i.e., GHOST Shared Risk Call for Proposals in 23B, Regular operations in 24A)
Provide an initial set of publicly available GHOST data to showcase the commissioned capabilities and range of science and inform proposal preparation by the wider Gemini community

About 40 hours of engineering time have been allocated for GHOST SV observations.

Regular updates on the GHOST System Verification observation planning and results will be presented on this page. An expected timeline is provided below.

A SV team, which includes Gemini observatory personnel and community representatives will plan, conduct, reduce, and evaluate the observations, and present the results to support broader community use of GHOST. A subset of this group, the Instrument Science Team (IST), is primarily responsible for developing observations to take for SV, and reducing and analyzing those datasets. The IST is chosen in consultation with the Gemini Directorate, STAC, and the NRC-led GHOST Instrument team.

SV Team

Instrument Science Team (IST)	Affiliation	Additional Roles
Siyi Xu	Gemini/NOIRLab	SV Lead
Kristin Chiboucas	Gemini/NOIRLab	Deputy SV Lead
Christian Hayes	NRC Herzberg	Data Reduction S/W Support
Eder Martioli	Laboratório Nacional de Astrofísica (LNA)/BR NGO
Emily Deibert	Gemini/NOIRLab	GHOST Instrument Support
Jeong-Eun Heo	Gemini/NOIRLab	GHOST Instrument Support
Kim Venn	University of Victoria
Roberto Gamen	Instituto de Astrofísica de La Plata (CONICET - UNLP)
Venu Kalari	Gemini/NOIRLab	GHOST Instrument Support
Vinicius Placco	NOIRLab/US NGO

Additional Support	Affiliation	Roles
David Jones	Gemini/NOIRLab	Community Engagement
Zachary Hartman	Gemini/NOIRLab	Community Engagement
Susan Ridgeway	NOIRLab/US NGO	Community Engagement
Chris Simpson	Gemini/NOIRLab	Data Reduction S/W Advisor
Kathleen Labrie	Gemini/NOIRLab	Data Reduction S/W Advisor
Bryan Miller	Gemini/NOIRLab	Operations S/W Support
Joanna Thomas-Osip	Gemini/NOIRLab	Science Operations Support
Janice Lee	Gemini/NOIRLab	Project Sponsor & Gemini Directorate Representative

Expected timeline

April: Observation planning. Test Phase I Tool (PIT) and Observing Tool (OT) software. Begin data reduction pipeline SV testing.
May: Observations performed ~May 10-15. Description of the observations released.
June: Data reduction and evaluation. Raw data released.
July: Results of data quality evaluation released. Final report on strengths and weaknesses of the overall GHOST observation system.
August: Expected release of Call for Proposals for GHOST Shared Risk science in late August, with deadline September 30, for observations in the period November - January 2024. 61.3 hours have been allocated for this call.

GHOST Modes to be showcased in this SV run

Standard Resolution mode (R > 50,000)
- Single target mode
  - Bright targets (V_AB < 17.5 mag)
  - Fainter targets (17.5 < V_AB < 19 mag)
- Dual target mode
  - Bright targets (V_AB < 17.5 mag)
High Resolution mode (R > 75,000)
- Single target
  - bright targets (V_AB < 16 mag)

Acknowledgement for papers using GHOST SV data

Please include the following acknowledgment in any paper that makes use of GHOST SV data, in addition to the general Gemini acknowledgment.

GHOST was built by a collaboration between Australian Astronomical Optics at Macquarie University, National Research Council Herzberg of Canada, and the Australian National University, and funded by the International Gemini partnership. The instrument scientist is Dr. Alan McConnachie at NRC, and the instrument team is also led by Dr. Gordon Robertson (at AAO), and Dr. Michael Ireland (at ANU).

The authors would like to acknowledge the contributions of the GHOST instrument build team, the Gemini GHOST instrument team, the full SV team, and the rest of the Gemini operations team that were involved in making the SV observations a success.

Types of Science being done in SV

Program	PIs
GS-2023A-SV-101: Galactic Metal Poor Stars	Vinicius Placco, Kim Venn, Miji Jeong, Jeong-Eun Heo
GS-2023A-SV-102: GHOST Transmission Spectroscopy of Hot Exoplanet Atmospheres	Emily Deibert, Eder Martioli
GS-2023A-SV-103: Symbiotic Stars and White Dwarfs	Jeong-Eun Heo, Siyi Xu
GS-2023A-SV-104: Binary Star Systems	Roberto Gamen
GS-2023A-SV-105: Chemical abundance studies of stars in ultra-faint dwarf galaxies	Christian Hayes
GS-2023A-SV-106: Sextans A early type stars	Venu Kalari
GS-2023A-SV-107: Extragalactic Compact Systems	Kristin Chiboucas, Siyi Xu

GS-2023A-SV-101: Galactic Metal Poor Stars

High-resolution Spectroscopy of Extremely Metal-Poor Stars (Link to the data evaluation and analysis)
PI: Vinicius Placco
Modes: Standard resolution, single target, 2x4 and 1x2 binning
Science Goals: We will determine the chemical abundance patterns of extremely metal-poor stars ([Fe/H]<-3) with low carbon enhancement. These were identified from S-PLUS (narrow-band photometry) and followed up with med-res spectroscopy using Gemini/GMOS and Blanco/COSMOS. With a set of chemical abundances measured, in particular for lighter elements (Z<30) it will be possible to confirm their low-metallicity status and also compare their abundance pattern with yields from zero-metallicity faint supernova models available in the literature. These can help constrain the progenitor population for these stars. Moreover, these (bright) stars have very good Gaia parameters, allowing for a chemodynamical analysis, which can further constrain their origin.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
2MASSJ1424	14:24:45.4	-25:42:47	g 14.4	IQ70/CC70/SB80	20230510	0073	6x900s	IQ70/CC70

Carbon Abundance in an Ultra Metal-Poor Star
PI: Vinicius Placco
Modes: Standard resolution, single target, 2x4 binning
Science Goals: There are only about 40 stars observed with high-resolution (R > 20,000) spectroscopy in the literature with [Fe/H]<-4, including only 7 at [Fe/H]<-5. Among these, the fraction of stars with carbon enhancement is 80% for [Fe/H]<-4 and 100% for [Fe/H]<-5. These are considered "true" second-generation stars and provide essential constraints on the IMF of Population III, believed to be the first to be born in the Universe. There is one bright star (CD-38 245 - [Fe/H] ~ -4) in this group that, to this date, doesn't have a carbon abundance measurement, only an upper limit. Moreover, the current upper limit is below the expected value for this metallicity range. Having definite measurements for carbon is crucial to better understand star formation at the lowest metallicities. As an added benefit, the high S/N required for the carbon abundance will allow measurements of many additional atomic features than previous works, further constraining its chemical abundances.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
CD-38 245	00:46:36	-37:39:33.5	V 11.9	IQ85/CC70/SB80	20230513	0235, 0237-0238	3x1200s	IQ70/CC70
"					20230516	0143-0145	3x1200s	IQ85-Any/CC50/SB80-Any
"					20230518	0121	1x1200s	IQ85-Any/CC50

Chemically Peculiar EMP near-circular planar MW star (Link to the data evaluation and analysis)
PI: Kim Venn
Modes: Standard resolution, single target, 2x2 binning
Science Goals: The early accretion history of the MW disk will be revealed by high-resolution spectroscopy of individual stars, even in the era of Gaia and stellar spectroscopic surveys. The targets are rare and expected to be extremely metal poor ([Fe/H] < -3), today on near-circular planar orbits, and likely to have a chemical fingerprint that reveals their origins – thus properties of the early universe as held in the secrets of the accreted proto-galactic fragments. We propose to observe Pristine_183.6849+04.8619 (G=14.8, A_G=0.03). Venn et al. (2020) found it has a near-circular prograde planar orbit (R_apo = 8.5 kpc, ecc = 0.3, Z_max = 1.2 kpc), and analysis of its CFHT/ESPaDoNS spectrum showed it is EMP ([Fe/H] = -3.1), with unusually low magnesium and sodium ([Mg/Fe] = 0.1, [Na/Fe] = -0.2); all other elements were below detection limits. GHOST spectra would uniquely probe carbon and heavy elements (Eu, Sr, Ba) to test its origins and the nucleosynthetic history of the gas in its original host galaxy.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
Pristine_183.6849+04.8619	12:14:44.4	+04:51:42.8	V 15.0	IQ70/CC70/SBAny	20230510	0072	Red: 5x1200s, Blue: 3x1800s	IQ70/CC70

High-resolution spectroscopic follow-up of Dynamically Associated Metal-Poor star
PI: Vinicius Placco, Miji Jeong, Jeong-Eun Heo
Modes: Standard resolution, single target, 1x2 binning
Science Goals: J1222 (g = 12.9 mag) is dynamically associated with substructures of the MW known as Gaia-Sausage or Gaia-Enceladus and has a low metallicity [Fe/H] < -2.0. Considering the retrograde motion, it is a strong candidate to have originated from outside MW. Therefore, we propose to obtain a standard-resolution (R=50,000) spectrum for J1222. Through the high-quality spectrum, we can accurately determine the atmospheric parameters of the star and measure chemical abundances from various elemental absorption lines. Combining the detailed chemical abundance with kinematic information from Gaia, this study will allow us to further investigate the star formation history of the progenitor of this substructure in the Galactic halo.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
J1222	12:22:16.86	-06:33:45.26	g 12.86	IQ85/CC70/SB50	20230510	0055	3x1500s	IQ70/CC50

GS-2023A-SV-102: GHOST Transmission Spectroscopy of Hot Exoplanet Atmospheres

GHOST Spectroscopy of Hot Exoplanet Atmospheres(Link to the data evaluation and analysis)
PI: Emily Deibert
Modes: High resolution, 1x4 binning
Science Goals: Characterizing exoplanet atmospheres is the next frontier in exoplanet science, with the potential to shed light on exoplanet compositions, dynamics, and formation histories. High-resolution spectroscopy is one of the most promising methods by which we can characterize exoplanet atmospheres, as it allows us to resolve individual atomic spectral lines, search for phase- and altitude-dependent atmospheric variability, and detect the weak absorption signals due to atmospheric molecules. In recent years, high-resolution spectroscopy at optical wavelengths has flourished, with dozens of atomic and molecular atmospheric species now detected. High-resolution optical spectra have allowed us to study condensation (e.g., Ehrenreich et al. 2020), atmospheric escape (e.g., Turner et al. 2020), non-local thermodynamic equilibrium effects (e.g., Deibert et al. 2021b), and atmospheric wind speeds (e.g., Seidel et al. 2021), among many other atmospheric processes. Highly irradiated hot and ultra-hot Jupiters are particularly compelling targets because their optical spectra are rich in atomic and ionic species (including Na I, K I, Ca II,Ti I, and Fe I) due to the fact that most molecules have ionized at these hot (>2000 K) temperatures. With high-resolution optical spectra, we can potentially resolve a dozen or more species (e.g., Tabernero et al. 2021, Kesseli et al 2022), answering a number of questions about the physical and chemical processes at work in hot exoplanet atmospheres.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
WASP-189	15:02:44.9	-03:01:53	V 6.6	IQ85/CC70/SBAny	20230513	0059 - 0222	164 x 45s	IQ70/CC70

Characterization of a solar-like star and its transiting hot Jupiter (Link to the data evaluation and analysis)
PI: Eder Martioli
Modes: Standard resolution, dual target, 2x4 binning
Science Goals: High-resolution spectral observations of transiting exoplanet systems provide important constraints for the characterization of planets and their host stars. We propose to observe the transit of a hot Jupiter around a Sun-like star in GHOST's dual target mode to obtain differential time series with simultaneous observation of a comparison star of similar magnitude and spectral type. From these observations, one can measure the shape of the transit as a function of wavelength and thus obtain the spectral variations in the depth of the transit to detect atmospheric features by transmission spectroscopy. The optical domain of GHOST allows the detection of atomic features such as Na and K or molecular features such as H2O and CO2. The overall shape of the transmission spectrum or even the absence of features can inform about the physics of the planet's atmospheres, such as whether there is dominant Reighleigh scattering or to distinguish between a cloudy and a cloud-free atmosphere. If these observations can be sufficiently anchored (for example, using the reference star as an RV constant), one can measure the spin-orbit obliquity through the Rossiter McLaughlin effect. An important scientific capability of GHOST that will be explored in this experiment, which is important for exoplanetary science, is the characterization of the Sun-like host star. We will combine the spectra in the time series to measure fundamental stellar properties such as Teff, log(g), [Fe/H], vsin(i), elemental abundances and activity indices.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
WASP-108	13:03:18.718	-49:38:22.8	V 11.21	IQ85/CC70/SBAny	20230512	0045 - 0073	28x (Red: 2x300s Blue: 1x600s)	IQ85/CC70
18 Sco (Standard)	16:15:37.27	-08:22:09.98	V 5.5	IQ85/CC80/SBAny	20230512	0084 - 0086	3x (Red: 8x15s Blue: 2x60s)	IQ85/CC70

GS-2023A-SV-103: Symbiotic Stars and White Dwarfs

Monitoring Raman O VI feature in M 1-21(Link to the data evaluation and analysis)
PI: Jeong-Eun Heo
Modes: Standard resolution, single target, 1x2 binning
Science Goals: We found one interesting symbiotic star showing a significant change in Raman O VI profile over the four months. The object is M 1‐ 21, known to have strong Raman O VI with multiple‐peak profiles with a relatively short orbital period of ∼800 days. High‐resolution spectra of M 1‐21 with MIKE taken in March and July 2017 show three main‐peak components of Raman O VI having different velocity values from ‐30 km/s to 90 km/s. In addition, we detected a significant change in the Raman profile over the four months: the middle peak flux decreased significantly, whereas others varied only slightly. To characterize this component and determine whether it changes depending on the orbital phase, we need to perform high-resolution spectroscopic monitoring for this target. We expect to distinguish velocity components with different origins. This study will allow us to better understand the mechanism of Raman-scattering and further investigate the detailed structure of the symbiotic star.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
M 1-21	17:34:17.2	-19:09:21.9	V 13.7	IQ85/CC50/SB50	20230518	0074 - 0075	3x180s, 1x10s	IQ85-Any/CC50
LTT 7379 (Standard)	18:36:25.95	-44:18:36.91	V 10.22	IQ85/CC70/SBAny	20230518	0076	Red: 140s, Blue 300s	IQ85-Any/CC50

Searching Raman O VI features in Galactic SySts(Link to the data evaluation and analysis)
PI: Jeong-Eun Heo
Modes: Standard resolution, single target, 1x2 binning
Science Goals: Our team has collected high-resolution spectra of symbiotic stars, from which we have noted that several objects have strikingly similar profiles of the Raman O VI features. Previous studies suggest that the Raman O VI features provide information of the kinematics of the emission region and the geometry of the scattering region. Therefore, the similarity of the Raman O VI profiles suggests that they have similar kinematics of the emission region and the geometry of the scattering region, implying that their evolutionary stages are closely related. We thus expect to infer the evolutionary stage of a given SySt from the statistical study of its Raman O VI profile. It would also be interesting to study the relation between the outburst history and the Raman O VI profiles, which could confirm our hypothesis that Raman O VI profiles provide information of bipolar jet outflow. Moreover, we anticipate discovering a correlation with X-ray characteristics because the hardness of X-ray depends on the existence of accretion and nuclear burning on their WD surface. With a detailed profile analysis of Raman O VI features, our proposal aims to construct the extensive atlas of Raman O VI features in Galactic SySts by obtaining high-resolution spectra of SySts which have the confirmed Raman O VI feature in their mid-resolution spectra but have never been observed with high-resolution spectrographs. This comprehensive atlas will pave the way for addressing important and broad astrophysical questions and revealing the late stage of stellar evolution.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
V366 Car	09:54:43.3	-57:18:52.4	V 13.0	IQ85/CC50/SB80	20230516	0041-0042	3x150s, 1x10s	IQ85/CC50
Hen 3-828	12:50:58.0	-57:50:47.0	V 13.4	IQ85/CC50/SB80	20230516	0043-0044	3x150s, 1x10s	IQ85/CC50
LTT 4816 (Standard)	12:38:49.78	-49:48:00.22	V 13.96	IQ85/CC50/SB80	20230516	0042, 0045	2x (Red: 2x140s, Blue 1x300s)	IQ85/CC50

A White Dwarf with A Disintegrating Asteroid (Link to the data evaluation and analysis)
PI: Siyi Xu
Modes: Standard resolution, single target, 1x2 binning
Science Goals: Planets are prevalent around main sequence stars, but little is known about their fate once the star evolves off the main sequence. WD 1145+017 is the first white dwarf discovered to show transits from a disintegrating asteroid (Vanderburg et al. 2015). It has been studied intensively using various facilities from the ground (e.g., Keck, VLT) and in space (e.g., Spitzer, Hubble). It turns out to be a remarkable system. WD 1145+017 shows strong infrared excess from a dust disk. The atmosphere is heavily polluted from accretion of the circumstellar material. WD 1145+017 also uniquely shows broad circumstellar gas absorption (as shown in Figure 1). It is a benchmark system that ties all the components of planetary systems around white dwarfs together. Here, we propose to obtain one new epoch of GHOST spectra to understand the long term evolution of the circumstellar lines in WD 1145+017.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
WD 1145+017	11:48:33.6	+01:28:59.4	V 17.3	IQ70/CC70/SB80	20230510	0056	3x1800s	IQ70-85/CC70-80
LTT 7379 (Standard)	18:36:25.95	-44:18:36.91	V 10.22	IQ85/CC70/SBAny	20230516	0106	Red: 60s, Blue 300s	IQ85/CC50

GS-2023A-SV-104: Binary Star Systems

Revealing ghosts in single-lined spectroscopic binaries
PI: Roberto Gamen
Modes: High resolution, 1x2 binning
Science Goals: I propose to obtain high resolution and SNR spectra of a few massive single-lined spectroscopic binary systems (SB1) aiming at revealing their ghostly companions. These stars have been identified as SB1 from optical spectra obtained with echelle spectrographs attached to 2-meter class telescopes (typical R=40000). To identify any spectral feature of a companion (and to measure their radial velocities) permits determining the minimum masses of both components (and mass ratios), and, in turn, contributing with observational evidence about some issues related with the massive stellar formation, e.g. how extreme is the competitive accretion among massive stars.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
HD 152314	16:54:32.00	-41:48:18	V 7.8	IQ85/CC70/SB80	20230511	0045 - 0047	1x300s	IQ85/CC70
HD 165246	18:06:04.68	-24:11:43	V 7.6	IQ85/CC70/SB80	20230513	0223-0225	3x200s	IQ70/CC70
"					20230515	0052-0054	3x200s	IQ70-85/CC70
"					20230516	0102-0104	3x200s	IQ85/CC50
HD 101190	11:38:09.91	-63:11:49	V 7.4	IQ85/CC70/SB80	20230514	0018-0020	3x180s	IQ70/CC50
"					20230516	0037-0039	3x180s	IQ85/CC70
HD 163892	17:59:26.31	-22:28:00	V 7.4	IQ85/CC70/SB80	20230515	0029-0031	3x180s	IQ85/CC70
HIP 84150 (Telluric)	17:12:16.205	-39:30:25.02	V 5.655	IQ85/CC70/SB80	20230511	0048-0050	1x60s	IQ85/CC70

High-precision analysis of binary systems using GHOST
PI: Roberto Gamen
Modes: Standard resolution, single target, 2x8 binning
Science Goals: The chemical tagging consist in the possibility of identifying co-natal stars, based on the assumption that they share a common homogeneous composition (e.g. Freeman & Bland-Hawthorn 2002, ARA&A, 40, 487; Casamiquela+2021, A&A 654, A151). This idea motivated important surveys such as APOGEE, GALAH and the Gaia-ESO survey. However, there is recent evidence of a possible relation between binary separation and metallicity difference between components (Ramirez+2019, MNRAS 490, 2448; Liu+2021, MNRAS 508, 1227). If confirmed, this relation would strongly challenge the homogeneity assumed for co-natal stars. Also, this would place important constraints to formation models of multiple systems (e.g. Bate 2019, MNRAS 484, 2341; Guszejnov+2021, MNRAS 502, 3646) and also to hydrodynamic simulations of ISM mixing (e.g. Feng & Krumholz 2014, Nature 513, 523; Armillotta+2018, MNRAS, 481, 5000). Giant planet occurrence could be also severely impacted: for instance, a metallicity difference of ∼0.3 dex implies a probability difference of 15-30% between both stars (e.g. Fischer & Valenti, 2005, ApJ 622, 1102). Therefore, this important correlation should be urgently explored. The general aim of this proposal is to test the proposed correlation between binary separation and metallicity difference between components, through a high-precision analysis of a carefully selected sample of binary stars.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
HD 138202	15:31:43.47	-31:02:49.08	V 9.71	IQ85/CC70/SBAny	20230515	0055 - 0057	3x180s	IQ85/CC70
CD-30 12303	15:31:46.27	-31:03:53.40	V 9.79	IQ85/CC70/SBAny	20230516	0073-0075	3x200s	IQ85/CC50-70

GS-2023A-SV-105: Chemical abundance studies of stars in ultra-faint dwarf galaxies

Investigating the chemistry of the ultra-faint satellites Bliss 1 and Crater 2 (Link to the data evaluation and analysis)
PI: Christian Hayes
Modes: Standard resolution, single target, 2x8 binning
Science Goals: Ultra-faint dwarf galaxies (UFDs) are some of the oldest and most metal-poor stellar systems in the local universe, and, as such, provide a unique opportunity to explore the star formation and chemical enrichment in environments like those of the first galaxies. Some of these systems even house stars that are thought to have been enriched by individual rare nucleosynthesis events, as seen in the r-process enhancement in Reticulum 2 (Ji et al. 2016), or enrichment from so-called faint supernovae as seen in a Pisces II UFD star (Spite et al. 2018). Crater 2 has previously been identified as a particularly interesting UFD, because of it’s unusually large size (covering ~ 5 degrees on the sky), putting it into a class of few other objects, such as the Antlia 2 UFD, that have been proposed to be tidally disrupted. Recent dynamical studies of Crater 2, however, suggest that its velocity dispersion is too low (relative to its size) to be consistent solely with tidal stripping (Ji et al. 2021, Borukhovetskaya et al. 2022). By studying the chemistry of this system we can see if this reveals any hints to how this system has evolved (for example chemical abundance patterns can reveal whether a system has experienced inflows or outflows of gas; Andrews et al. 2017, Hasselquist et al. 2021).

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
GDR32672	11:47:59.19	-18:10:40.67	V 17.8	Q70/CC50/SB20	20230513	0056	3x800s	IQ70/CC50-70
GDR36912	11:50:08.67	-18:18:14.66	V 17.8	IQ70/CC50/SB20	20230513	0057	3x800s	IQ70/CC50-70

Observing the metal-poor benchmark star HD 140283
PI: Christian Hayes
Modes: High resolution,1x1 binning
Science Goals: HD 140283 is a well studied metal-poor subgiant benchmark star. It is one of the few evolved metal-poor Gaia ESO benchmark stars, and has also been studied interferometrically so its stellar parameters are well understood. Observing this star would demonstrate GHOSTs wavelength coverage, resolution, and sensitivity in a way comparable to other high resolution spectrographs, many of which have observed this star. This star is also often compared to as a metal-poor stellar template that can be observed at high S/N and high resolution to investigate the spectral features that are present in other (lower S/N and lower resolution) observations of metal-poor stars.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
HD 140283	15:43:01.32	-10:56:07.72	V 7.21	IQ85/CC80/SB80	20230511	0051	3x200s	IQ70/CC70

GS-2023A-SV-106: Sextans A early type stars

Sextans A early type stars
PI: Venu Kalari
Modes: Standard resolution, single target, 2x8 binning
Science Goals: We propose to observe a 21mag early type star in nearby dwarf galaxy SextansA. This is the earliest known spectral type, of O3-5Vz, at metallicities below a 1/10 Zsolar. This would be pushing the boundaries of observational possibilities, since such a target has never been observed at such a high resolution before. With a predicted SNR of around 10, it will be possible to detect other lines such as NV or HeII and also perform a basic analysis, subject to a quality assessment.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
SextansA - s2	10:10:58	-04:44:1	V 20	IQ70/CC50/SB50	20230514	0015-0017	3 x (Red: 2x1800s, Blue: 1x3600)	IQ20/CC50
"					20230518	0064	1 x (Red: 2x1800s, Blue: 1x3600)	IQAny/CC50

GS-2023A-SV-107: Extragalactic compact systems

Extragalactic compact stellar systems (Link to the data evaluation and analysis)
PI: Kristin Chiboucas
Modes: Standard resolution, single target, 2x4 binning
Science Goals: Ultra-compact dwarfs (UCDs) are massive star clusters whose origins are still being investigated. They may be globular clusters comprising the extreme bright tail of the globular cluster luminosity function or super star cluster end products from the mergers of massive star clusters, or they may be remnant nuclear star clusters of tidally stripped galaxies. The populations may also be composed of some combination of these various processes. A number of UCDs and globular clusters have been found with high internal velocity dispersions and elevated M/L ratios, which has been used to infer the presence of supermassive black holes in their cores, indicative of a galactic origin (e.g. Gebhardt et al. 2002, Mieske et al. 2013, Dumont et al. 2022). Nuclear star clusters, which formed in the cores of dark matter haloes, are also likely to have experienced more extended star formation histories than globular clusters. Some of the bright globular cluster/UCDs in CenA, which have previous high resolution spectroscopic observations, have been shown to exhibit evidence for a central supermassive black hole, while others do not (Dumont et al. 2022). Investigating the detailed chemical compositions of the systems with and without purported supermassive central black holes and between these objects and nuclear star clusters may shed further light on the evolutionary history of these compact stellar systems. The observations proposed here of both a nuclear star cluster and a couple UCDs will also be used to test GHOST capabilities on extended objects.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
HD 205905 (Standard)	21:39:10.151	-27:18:23.66	V 6.74	IQ85/CC80/SBAny	20230513	0234	3x8s	IQ70/CC70
HD 165195 (RV Standard)	18:04:40.071	03:46:44.72	V 7.3	IQ85/CC80/SBAny	20230513	0233	6x5s	IQ70/CC70
HD 103295 (RV Standard)	11:53:37.022	-28:38:13.02	V 9.56	IQ85/CC70/SBAny	20230515	0032	3x20s	IQ70-85/CC70

Resolving the “trees” of the Lyman-alpha Forest (Link to the data evaluation and analysis)
PI: Siyi Xu
Modes: Standard resolution, single target, 1x2 binning
Science Goals: Quasars are among the most luminous objects in the universe and as such can be observed to very large distances to peer back in the early phases of cosmic evolution. Finding and measuring the most luminous objects among the quasar population probes the high-end of the luminosity function, giving us clues about the physics of black hole accretion and about their formation mechanism (Schindler et al. 2021, ApJ 906, 12). As bright beacons, they trace large-scale structures in which they reside as well as the gas systems along the line-of-sight toward these luminous background sources. In particular, optical spectra of quasars at redshift z>2.1 probe the Lyman-alpha forest made by a series of hydrogen-absorbing intervening clouds from the circumgalactic medium (CGM) and intergalactic medium (IGM). In addition, absorbers from galaxies along the line-of-sight create metal absorption lines such as magnesium and carbon absorbers, which further tell us about galaxy evolution and the formation and distribution of metals in the CGM (Zou et al. 2023; arXiv:2302.13357). The exquisite resolution of the GHOST instrument (R=50,000) can give us a finely detailed picture of the Lyman-alpha forest and of the metal absorbers along the line-of-sight to bright quasars. Using early data from the Dark Energy Spectroscopic Instrument (DESI), we selected the brightest quasars at redshift z>2.1 which will be visible from Gemini South during the May science validation observing run.

Target	RA	Dec	Mag	Requested Conditions	Observation date	Observations	Integrations	Actual Conditions
QSO_1_3815	12:15:49.812	-00:34:32.17	V 17.5	IQ70/CC70/SB80	20230514	0021 - 0023	3x1500s	IQ70/CC50
EG274 (Standard)	16:23:33.838	-39:13:46.16	V 11.03	IQ85/CC70/SBAny	20230511	0041	2x90s	IQ70/CC70-80