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The Nancy Grace Roman Space Telescope is capable of delivering an unprecedented all-sky, high-spatial resolution, multi-epoch infrared map to the astronomical community. This opportunity arises in the midst of numerous ground- and space-based surveys that will provide extensive spectroscopy and imaging together covering the entire sky (such as Rubin/LSST, Euclid, UNIONS, SPHEREx, DESI, SDSS-V, GALAH, 4MOST, WEAVE, MOONS, PFS, UVEX, NEO Surveyor, etc.). Roman can uniquely provide uniform high-spatial-resolution (~0.1 arcsec) imaging over the entire sky, vastly expanding the science reach and precision of all of these near-term and future surveys. This imaging will not only enhance other surveys, but also facilitate completely new science. By imaging the full sky over two epochs, Roman can measure the proper motions for stars across the entire Milky Way, probing 100 times fainter than Gaia out to the very edge of the Galaxy. Here, we propose NANCY: a completely public, all-sky survey that will create a high-value legacy dataset benefiting innumerable ongoing and forthcoming studies of the universe. NANCY is a pure expression of Roman's potential: it images the entire sky, at high spatial resolution, in a broad infrared bandpass that collects as many photons as possible. The majority of all ongoing astronomical surveys would benefit from incorporating observations of NANCY into their analyses, whether these surveys focus on nearby stars, the Milky Way, near-field cosmology, or the broader universe., Comment: Submitted to the call for white papers for the Roman Core Community Survey (June 16th, 2023), and to the Bulletin of the AAS

Stellar streams form through the tidal disruption of satellite galaxies or globular clusters orbiting a host galaxy. Globular cluster streams are of particular interest since they are thin (dynamically cold) and therefore sensitive to perturbations from low-mass subhalos. Since the subhalo mass function differs depending on the dark matter composition, these gaps can provide unique constraints on dark matter models. However, current samples are limited to the Milky Way. With its large field of view, deep imaging sensitivity, and high angular resolution, the upcoming {\it Nancy Grace Roman Space Telescope} ({\it Roman}); presents a unique opportunity to significantly increase the number of observed streams and gaps. This paper presents a first exploration of the prospects for detecting gaps in streams in M31 and other nearby galaxies with resolved stars. We simulate the formation of gaps in a Palomar-5-like stream and generate mock observations of these gaps together with background stars in M31 and foreground Milky Way stellar fields. We assess {\it Roman}'s ability to detect gaps out to 10~Mpc through visual inspection and with the gap-finding tool {\it FindTheGap}. We conclude that gaps of $\approx 1.5$~kpc in streams that are created from subhalos of masses $\geq5 \times 10^6$ {\Msun} are detectable within a 2--3~Mpc volume in exposures of 1000s--1~hour. This volume contains $\approx$ 200 galaxies. Large samples of stream gaps in external galaxies will open up a new era of statistical analyses of gap characteristics in stellar streams and help constrain dark matter models., Comment: Submitted to ApJ. Comments are welcome!

This registration contains underlying data from a study that demonstrates inducible transposon mutagenesis in Chlamydia trachomatis, accompanying the paper submitted to Wellcome Open Research.

Supplemental material, sj-docx-1-evi-10.1177_13563890221126744 for Evaluating local system change using a comparative maturity matrix by Mike Coldwell, Sarah Pearson and Ian Wilson in Evaluation

Supplemental material, sj-docx-1-evi-10.1177_13563890221126744 for Evaluating local system change using a comparative maturity matrix by Mike Coldwell, Sarah Pearson and Ian Wilson in Evaluation

From the vast population of stellar streams in the Milky Way,we know that the morphology of thin, stellar streams, in particular, can be used to test the distribution and nature of dark matter.In the course of the nextdecade, a wealth of extragalactic stellar streams observations will becomeavailable, and stellar streams will be observed in galaxies out to severalhundred Mpc. How will we take full advantage of these observations anddecipher the astrophysical information the data contain?In this talk, I review the current and future prospects of detecting stellar streams in external galaxies with a focus on globular cluster streams. I create mock-stellar streams and inject them to data from the PAndAS M31 survey to produce simulated M31 backgrounds mimicking what the Nancy Grace Roman Space Telescope (Roman) will observe in M31. Additionally,I estimate the distance limit to which globular cluster streams will be observable. Recent results demonstrate that for a 1 hour exposure Roman should detect globular cluster streams in resolved stars in galaxies out to distances beyond 3.5 Mpc. This volume contains at least 199 galaxies of which > 90% are dwarfs. If these external galaxies do not host spiral arms or galactic bars, gaps in their stellar streams provide an ideal test case for evidence of interactions with dark matter subhalos.

In this Dissertation we explore how the nature of tidal interactions tear gravitationally bound systems apart into distinct morphological and kinematic structures. We use the properties of these structures, persisting for billions of years, to investigate the potential of the Milky Way Galaxy and to disentangle the baryonic evolution of gas in dwarf galaxy interactions. We approach these problems through a combination of observations, and simulations, as well as comparisons between the two. In particular, we use the properties of the thin, curved stellar stream emerging from the old, Milky Way globular cluster, Palomar 5 (Pal 5) to show that its mere existence can rule out a moderately triaxial potential model of our Galaxy. Pal 5-like streams on appropriate orbits diffuse much further in space from the orbital path (dubbed “stream-fanning”) in this triaxial potential than in the oblate case. We further show that torques from the Milky Way’s Galactic bar, can create ever-widening gaps in stellar streams. The fact that the bar can create such under densities, demonstrates that we should be careful when interpreting gaps in stellar streams as indirect evidence of the existence of dark matter subhalos in our Galaxy. We carry out a systematic study of resolved neutral hydrogen (HI) synthesis maps of 10 interacting dwarf galaxy pairs. The pairs are located in a range of environments and captured at various interaction stages. We find that the neutral gas is extended in the interacting pairs when compared to non-paired analogs, indicating that gas is tidally pre- processed. Additionally, we find that dwarf-dwarf interactions enable the “parking” of gas at large distances to serve as a continual gas supply channel to the dwarfs until accretion by a more massive host. We model a specific dwarf pair in our sample, NGC 4490/85, which is an isolated analog of the Magellanic Clouds and is surrounded by a ∼50 kpc extended HI envelope. We use hybrid N-body and test-particle simulations along with a visualization interface to simultaneously reproduce the observed present-day morphology and kinematics. Our numerical results con- firm that encounters between two dwarf galaxies can “park” baryons at very large distances, without the aid of environmental effects. The extended tidal features will continue to evolve over several billion years which will affect the efficiency of gas stripping if such dwarf pairs are accreted by a massive host. In contrast, in isolated environments dwarf-dwarf interactions can create a long-lived supply mode of gas to the merger remnant potentially explaining the population of dwarfs in the field with large gas envelopes, but limited star formation. All of these topics share the common theme of utilizing morphological and kinematic structures left behind from ongoing gravitational interactions on various scales.