The inner hundred parsecs of the Milky Way hosts the nearest supermassive black hole, largest reservoir of dense gas, greatest stellar density, hundreds of massive main and post main sequence stars, ...and the highest volume density of supernovae in the Galaxy. As the nearest environment in which it is possible to simultaneously observe many of the extreme processes shaping the Universe, it is one of the most well-studied regions in astrophysics. Due to its proximity, we can study the center of our Galaxy on scales down to a few hundred AU, a hundred times better than in similar Local Group galaxies and thousands of times better than in the nearest active galaxies. The Galactic Center (GC) is therefore of outstanding astrophysical interest. However, in spite of intense observational work over the past decades, there are still fundamental things unknown about the GC. JWST has the unique capability to provide us with the necessary, game-changing data. In this White Paper, we advocate for a JWST NIRCam survey that aims at solving central questions, that we have identified as a community: i) the 3D structure and kinematics of gas and stars; ii) ancient star formation and its relation with the overall history of the Milky Way, as well as recent star formation and its implications for the overall energetics of our galaxy's nucleus; and iii) the (non-)universality of star formation and the stellar initial mass function. We advocate for a large-area, multi-epoch, multi-wavelength NIRCam survey of the inner 100\,pc of the Galaxy in the form of a Treasury GO JWST Large Program that is open to the community. We describe how this survey will derive the physical and kinematic properties of ~10,000,000 stars, how this will solve the key unknowns and provide a valuable resource for the community with long-lasting legacy value.
We examine the observed properties of the Nili Fossae olivine-clay-carbonate
lithology from orbital data and in situ by the Mars 2020 rover at the
S\'e\'itah unit in Jezero crater, including: 1) ...composition (Liu, 2022) 2)
grain size (Tice, 2022) 3) inferred viscosity (calculated based on geochemistry
collected by SuperCam (Wiens, 2022)). Based on the low viscosity and
distribution of the unit we postulate a flood lava origin for the
olivine-clay-carbonate at S\'e\'itah. We include a new CRISM map of the clay
2.38 {\mu}m band and use in situ data to show that the clay in the olivine
cumulate in the S\'e\'itah formation is consistent with talc or serpentine from
Mars 2020 SuperCam LIBS and VISIR and MastCam-Z observations. We discuss two
intertwining aspects of the history of the lithology: 1) the emplacement and
properties of the cumulate layer within a lava lake, based on terrestrial
analogs in the Pilbara, Western Australia, and using previously published
models of flood lavas and lava lakes, and 2) the limited extent of post
emplacement alteration, including clay and carbonate alteration (Clave, 2022;
Mandon, 2022).
The next decade affords tremendous opportunity to achieve the goals of Galactic archaeology. That is, to reconstruct the evolutionary narrative of the Milky Way, based on the empirical data that ...describes its current morphological, dynamical, temporal and chemical structures. Here, we describe a path to achieving this goal. The critical observational objective is a Galaxy-scale, contiguous, comprehensive mapping of the disk's phase space, tracing where the majority of the stellar mass resides. An ensemble of recent, ongoing, and imminent surveys are working to deliver such a transformative stellar map. Once this empirical description of the dust-obscured disk is assembled, we will no longer be operationally limited by the observational data. The primary and significant challenge within stellar astronomy and Galactic archaeology will then be in fully utilizing these data. We outline the next-decade framework for obtaining and then realizing the potential of the data to chart the Galactic disk via its stars. One way to support the investment in the massive data assemblage will be to establish a Galactic Archaeology Consortium across the ensemble of stellar missions. This would reflect a long-term commitment to build and support a network of personnel in a dedicated effort to aggregate, engineer, and transform stellar measurements into a comprehensive perspective of our Galaxy.
We examine the observed properties of the Nili Fossae olivine-clay-carbonate lithology from orbital data and in situ by the Mars 2020 rover at the Séítah unit in Jezero crater, including: 1) ...composition (Liu, 2022) 2) grain size (Tice, 2022) 3) inferred viscosity (calculated based on geochemistry collected by SuperCam (Wiens, 2022)). Based on the low viscosity and distribution of the unit we postulate a flood lava origin for the olivine-clay-carbonate at Séítah. We include a new CRISM map of the clay 2.38 {\mu}m band and use in situ data to show that the clay in the olivine cumulate in the Séítah formation is consistent with talc or serpentine from Mars 2020 SuperCam LIBS and VISIR and MastCam-Z observations. We discuss two intertwining aspects of the history of the lithology: 1) the emplacement and properties of the cumulate layer within a lava lake, based on terrestrial analogs in the Pilbara, Western Australia, and using previously published models of flood lavas and lava lakes, and 2) the limited extent of post emplacement alteration, including clay and carbonate alteration (Clave, 2022; Mandon, 2022).
We present the data reduction procedures being used by the GALAH survey, carried out with the HERMES fibre-fed, multi-object spectrograph on the 3.9~m Anglo-Australian Telescope. GALAH is a unique ...survey, targeting 1 million stars brighter than magnitude V=14 at a resolution of 28,000 with a goal to measure the abundances of 29 elements. Such a large number of high resolution spectra necessitates the development of a reduction pipeline optimized for speed, accuracy, and consistency. We outline the design and structure of the Iraf-based reduction pipeline that we developed, specifically for GALAH, to produce fully calibrated spectra aimed for subsequent stellar atmospheric parameter estimation. The pipeline takes advantage of existing Iraf routines and other readily available software so as to be simple to maintain, testable and reliable. A radial velocity and stellar atmospheric parameter estimator code is also presented, which is used for further data analysis and yields a useful verification of the reduction quality. We have used this estimator to quantify the data quality of GALAH for fibre cross-talk level (\(\lesssim0.5\)%) and scattered light (\(\sim5\) counts in a typical 20 minutes exposure), resolution across the field, sky spectrum properties, wavelength solution reliability (better than \(1\) \(\mathrm{km\ s^{-1}}\) accuracy) and radial velocity precision.
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