Colloquium: Shaking the dust off the Sombrero

Event date
-
Speaker
Jessica Sutter
Affiliation
USRA
Location
(In person) Ames Research Center (Virtual) Webex
Event Type

The interplay between heating and cooling within the interstellar medium (ISM) is crucial for the regulation of ongoing star formation and therefore plays a key role in galaxy evolution. While the heating of the ISM can be traced by dust emission, cooling occurs via fine structure line emission, primarily the 158μm singly-ionized carbon line, [CII]. By comparing these tracers in a wide variety of galaxy types, inclinations, and ISM conditions, we can assess what conditions limit the photoelectric heating efficiency and therefore could hamper potential future star formation.

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Colloquium: Investigating the electron density distribution in low metallicity environment

Event date
-
Speaker
Fiorella Polles
Affiliation
USRA
Location
(In person) Ames Research Center (Virtual) Webex
Event Type

ALMA studies of galaxies at the epoch of reionization revealed that the far-infrared line emission [OIII]λ88µm is often very strong, a result which suggests a diffuse hard radiation field and a porous interstellar medium (ISM), through which the ionizing photons escape. While it is not possible to study in the detail the ISM of these high-redshift galaxies, we can gain insights into the internal structure of these galaxies by studying local analogs of the ‘chemically young’ environments that characterize those high-redshift galaxies: the nearby low-metallicity dwarf galaxies.

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Magnets in the Sky

Event date
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Speaker
Bryan Gaensler
Affiliation
U. Toronto
Location
Online
Event Type

Everywhere we look, the Universe is threaded with magnetism. These magnetic fields are surprisingly organised and coherent, and are vital to many of the fundamental processes that astronomers take for granted. However, the mechanisms that create and then sustain magnetism in the Universe are not understood, in no small part because magnetic fields are usually not directly observable.

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Multiwavelength Observations of Dwarf-Dwarf Mergers: Fueling Hierarchical Assembly

Event date
Speaker
Sabrina Stierwalt
Affiliation
Occidental College
Location
Online
Event Type

Both cosmological simulations and observations of the ultraviolet luminosity function suggest dwarf galaxies are the dominant population at high redshifts and that the galaxy merger rate per unit volume is dominated by low mass galaxies. However, dwarf-dwarf interactions have not yet been subject to systematic study, even in the nearby universe. I will report on our efforts to do just that: TiNy Titans is the first systematic study of a sample of isolated interacting dwarf galaxies and the mechanisms governing their star formation.

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Interstellar Hydrides and What They Tell Us

Event date
Speaker
David Neufeld
Affiliation
JHU
Location
Online
Event Type

Interstellar hydrides - that is, molecules containing a single heavy element atom with one or more hydrogen atoms - were among the first molecules detected outside the solar system. They lie at the root of interstellar chemistry, being among the first species to form in initially atomic gas along with molecular hydrogen and its associated ions.

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Simulating Protoplanetary Disk Ices

Event date
Speaker
Nicholas Ballering
Affiliation
UVA
Location
Online
Event Type

Ices play a crucial role in planet formation and the delivery of volatiles to terrestrial planets, yet direct observations of ices in protoplanetary disks have, to date, been limited. Upcoming observational facilities—including JWST, large ground-based telescopes, SPHEREx, new SOFIA instrumentation, and future far-IR missions—will greatly enhance our view of disk ices by measuring their infrared spectral features. I will present a suite of models designed to complement these upcoming observations.

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Surprises from the Expansion of the Universe

Event date
Speaker
Adam Riess
Affiliation
JHU/STScI
Location
Online
Event Type

The Hubble constant remains one of the most important parameters in the cosmological model, setting the size and age scales of the Universe. Present uncertainties in the cosmological model including the nature of dark energy, the properties of neutrinos and the scale of departures from flat geometry can be constrained by measurements of the Hubble constant made to higher precision than was possible with the first generations of Hubble Telescope instruments.

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Simulating vs. Observing Molecular Clouds: What’s Hidden in The Dark?

Event date
Speaker
Steffie Walch-Gassner
Affiliation
U. Cologne
Location
Online
Event Type

Molecular gas is mostly traced by CO line emission. In particular 12CO(J=1-0) is bright and hence it is commonly used to estimate the molecular gas content of cold clouds. Yet, the CO molecule does not trace all molecular gas. It is more easily dissociated than molecular hydrogen and hence needs visual extinctions higher than 3 mag in order to survive. This leads to the existence of CO-dark molecular hydrogen. Once formed, the CO line becomes quickly optically thick. As a result, only a narrow range of column densities can actually be traced well with 12CO.

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The Magnetic Milky Way in Three Dimensions

Event date
-
Speaker
Susan Clark
Affiliation
Stanford U
Location
Online
Event Type

Magnetic fields thread our Milky Way Galaxy, influencing interstellar physics from cosmic ray propagation to star formation. The magnetic interstellar medium is also a formidable foreground for experimental cosmology, particularly for the quest to find signatures of inflation in the polarized cosmic microwave background (CMB). Despite its importance across scientific realms, the structure of the Galactic magnetic field is not well understood.

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