Related papers: Absorption Line Studies in the Halo
High velocity gas that does not conform to Galactic rotation is observed throughout the Galaxy's halo. One component of this gas, HI high velocity clouds (HVCs), have attracted attention since their discovery in the 1960s and remain…
Recent, high sensitivity, HI observations of nearby spiral galaxies show that their thin `cold' disks are surrounded by thick layers (halos) of neutral gas with anomalous kinematics. We present results for three galaxies viewed at different…
Molecular hydrogen (H$_2$) is by far the most abundant molecule in the Universe. However, due to the low emissivity of H$_2$, carbon monoxide (CO) is widely used instead to trace molecular gas in galaxies. The relative abundances of these…
We examine how HI and metal absorption lines within low-redshift galaxy halos trace the dynamical state of circumgalactic gas, using cosmological hydrodynamic simulations that include a well-vetted heuristic model for galactic outflows. We…
Stellar halos may hold some of the best preserved fossils of the formation history of galaxies. They are a natural product of the merging processes that probably take place during the assembly of a galaxy, and hence may well be the most…
The Milky Way's disk-halo interface mediates energy and mass exchange between the interstellar thin disk and the halo. In the first detailed study of the Perseus arm's disk-halo interface, we combine HST/STIS and COS absorption spectra…
The Magellanic Stream, a gaseous tail that trails behind the Magellanic Clouds, could replenish the Milky Way with a tremendous amount of gas if it reaches the Galactic disk before it evaporates into the halo. To determine how the…
Deep photometric surveys of the Milky Way have revealed diffuse structures encircling our Galaxy far beyond the "classical" limits of the stellar disk. This paper reviews results from our own and other observational programs, which together…
We have combined observations of Galactic high-velocity HI from two surveys: a very sensitive survey from the Green Bank 140ft Telescope with limited sky coverage, and the less sensitive but complete Galactic All Sky Survey from the 64m…
Stellar streams are key players in many aspects of Milky Way studies and, in particular, studying their orbital dynamics is crucial for furthering our understanding of the Milky Way's gravitational potential. Although this is not a trivial…
A pole-count analysis of the infrared 2MASS survey is presented, in order to identify faint stream-like structures within the halo of the Milky Way. Selecting stars with colours consistent with M-giant stars, we find a strong over-density…
Feedback is indispensable in galaxy formation. However, lacking resolutions, cosmological simulations often use ad hoc feedback parameters. Conversely, small-box simulations, while better resolving the feedback, cannot capture gas evolution…
FUSE spectra of 100 extragalactic objects are analyzed to obtain measures of O VI absorption along paths through the Milky Way thick disk/halo. Strong O VI absorption over the approximate velocity range from -100 to 100 km/s reveals a…
We summarise recent results from analysis of APOGEE/Gaia data for stellar populations in the Galactic halo, disk, and bulge, leading to constraints on the contribution of dwarf galaxies and globular clusters to the stellar content of the…
Million degree gas is present at near-zero redshift and is due either to a gaseous Galactic Halo or a more diffuse but very massive Local Group medium. We can discriminate between these models because the column densities should depend on…
The Canadian Galactic Plane Survey has opened new vistas on the Milky Way, including cold hydrogen clouds that bridge a critical gap between the classical diffuse interstellar medium and the gravitationally bound molecular clouds that can…
Every star-forming galaxy has a halo of metal-enriched gas extending out to at least 100 kpc, as revealed by the absorption lines this gas imprints on the spectra of background quasars. However, quasars are sparse and typically probe only…
Modeling the Milky Way stellar halo requires well-determined density and velocity anisotropy profiles. However, it has been challenging to gather a large sample of stars with six-dimensional data that extend beyond 40 kpc to map the outer…
We present the first results from the Small Magellanic Cloud portion of a new Australia Telescope Compact Array (ATCA) HI absorption survey of both of the Magellanic Clouds, comprising over 800 hours of observations. Our new HI absorption…
Using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST) the COS Science Team has conducted a high signal-to-noise survey of 14 bright QSOs. In a previous paper (Savage et al. 2014) these far-UV spectra were used to…