What kind of research do we do?


  • Interstellar Matter in our Galaxy

    On the most nearby scales (within several hundred times the distance from the Earth to the Sun), the local interstellar medium (ISM) provides the boundary conditions for our Solar System, and the specific properties of the local ISM (as we pass through it) may have significant implications for the viability of life on the Earth. More globally, the ISM is an active participant in the overall life cycles of galaxies and stars. Stars are formed out of interstellar gas and dust (primarily hydrogen and helium), synthesize heavier elements from those initial raw materials, and return material to the ISM during their lives (and, in may cases, as they die). The abundances of elements heavier than hydrogen and helium found in the Galactic ISM thus reflect their production in successive generations of stars in the Galaxy.
  • Interstellar Matter in the Large and Small Magellanic Clouds

    Studies of the interstellar medium in the Magellanic Clouds (MC) explore different environmental conditions from those typically probed in our own Galactic ISM. On average, MC stars and H II regions have metallicities below solar values by 0.3 dex (LMC) and 0.6--0.7 dex (SMC), though the relative elemental abundances (e.g., [X/Zn], for elements X that we consider) are generally similar to those found for analogous Galactic objects. The ISM in both MC generally has lower dust-to-gas ratios, stronger ambient radiation fields, and significant differences in UV extinction (especially in the SMC). Determination of elemental abundances, depletions, and physical conditions in the MC ISM therefore provides interesting tests for theoretical models of interstellar clouds and dust grains, and should also yield insights into the nature of the even lower metallicity QSO absorption-line systems.
  • Interstellar Dust

    [few sentences describing ISM research]
  • Journey of the Sun

    The Sun moves through a low density (n<0.2 atoms /cc), warm (T=6500 K) diffuse interstellar cloud which forms the galactic environment of the Sun and provides the boundary conditions for the heliosphere. The space motion of the Sun is such that it has been within the interior of the Local Bubble for millions of years (the local bubble represents a deficit of interstellar gas). However, a discontinuity appears in ultraviolet observations of the velocity of the interstellar gas towards the nearest star (alpha Cen). This indicates that the galactic environment of the Sun may change within the next 10,000 years, which is pretty fascinating since the interplanetary environment at the location of the Earth is highly sensitive to the physical properties of the interstellar cloud surrounding the Sun. Frisch works in this area.
  • Intergalactic Matter

    Understanding the abundances and physical conditions in the interstellar media of our Galaxy and of other nearby galaxies (looking for both similarities and differences) also provides a basis for understanding the absorption-line systems (ALS) seen toward distant QSO's (quasi-stellar objects). The QSOALS exhibit absorption similar (in some respects) to the interstellar absorption features found in those more local contexts, and they are thought to be associated with distant galaxies (at earlier stages in their lives). At redshifts of 0.5--5.0, the QSOALS sample a fair fraction of the history of the Universe, and provide perhaps the best opportunity for tracing the global evolution of heavy element abundances from very early times to the present --- with significant implications also for the formation and evolution of galaxies.

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