Astronomy Colloquia at Caltech for 2018-19

Colloquia are held every Wednesday during the academic year at 4pm in the Cahill Hameetman auditorium.
Wine and cheese will be served in the Cahill Foyer from 5-5:30pm.

Month
Date
Speaker

Talk Title
OCTOBER
3

Speaker: David Charbonneau
Institute: Harvard
Host: D. Mawet

The Terrestrial Planets of Other Stars

For the next decade, the only opportunity to study the atmospheres of terrestrial exoplanets will be scrutinize these worlds when they transit nearby small stars. There are 417 mid-to-late M-dwarfs within 15 parsecs, yet we know surprisingly little about them, let alone their attendant planets. I will discuss recent findings from the MEarth Project and TESS Mission, which seek to discover the most spectroscopically accessible terrestrial exoplanets. Our recent discovery of a several rocky worlds transiting the nearby small star LHS1140 provides an unprecedented opportunity to detect the molecules present in the atmosphere of a terrestrial exoplanet. In our planetary quest, MEarth observations have sharpened our understanding of the evolution of these low-mass stars, and hence the stellar environment in which these planets may wither or thrive.

10

Speaker: Caroline Morley
Institute: UT Austin
Host: Eve Lee

From Exotic to Familiar: Observing Exoplanet Atmospheres in the Coming Decade

Observations of exoplanets to date have used the Hubble and Spitzer Space Telescopes to reveal exotic exoplanet atmospheres, including significant effort to characterize planets with radii between Earth's and Neptune's -for which we have no counterparts in the solar system-that are accessible to current telescopes. Observations of their transmission spectra reveal a diversity of worlds, some shrouded in clouds and others with molecular features. I will discuss the types of clouds and hazes that can obscure transmission spectra, and show the effect that these thick hazes have on the thermal emission of small exoplanets. I will discuss some of my plans for new observations during the first cycle of JWST to measure the thermal emission of these planets. The new frontier of exoplanet atmosphere studies is characterizing the atmospheres of planets more familiar to Earthlings: cold gas giants and temperate Earths. I will discuss my current work to reveal the atmosphere of a cold free-floating giant planet, and my plans for detecting a host of interesting molecules in its atmosphere with JWST. We will soon be able to access Earth-sized, temperate worlds for the most favorable 3 systems orbiting the small stars. I will discuss the recent discoveries of Earth-sized planets around bright M dwarfs and how we might use JWST to detect their atmospheres. Lastly, I will discuss prospects with current and upcoming ground-based telescopes to detect exoplanet atmospheres, including some steps to take preceding the launch of JWST.

17

Speaker:  J. Xavier Prochaska
Institute: UC Santa Cruz
Host: Chris Martin

The Wolfe Disk: ALMA Discoveries of Distant, HI-selected Galaxies

I will review our series of successful programs to dissect the interstellar medium of distant, star-forming galaxies with the Atacama Large Millimeter Array (ALMA).  In particular, I will discuss surveys of the set of HI-selected galaxies known as the damped Lya systems (DLAs).  We resolve, in part, a decades old struggle to identify the galactic counterparts of these DLAs and thereby place them firmly in the modern picture of galaxy formation.  I will also highlight high spectral and spatial resolution observations of the Wolfe Disk,a z~4 galaxy with a Milky Way-like rotation curve.

24
Speaker: Brad Cenko
Institute: NASA
Host: M. Kasliwal

Recent Observational Puzzles from Tidal Disruption Flares: Towards Viable Probes in the LSST Era

I will present an overview of efforts across the electromagnetic spectrum to identify and study tidal disruption flares (TDFs), when a star wanders too close to a super-massive black hole and is torn apart by tidal forces. In particular I will focus on three unexpected surprises that challenge the most basic picture of these events: 1) large inferred radii for the optical/UV-emitting material, indicating either circularization of the bound debris at large distances and/or significant reprocessing of the radiation from the inner accretion disk; 2) the ubiquity of outflows, detected at radio, X-ray, and UV wavelengths, ranging from speeds of 100 km/s to near the speed of light; and, 3) the peculiar atomic abundances observed in the UV and optical spectra of these objects. Understanding the nature of the broadband emission will be critical if we wish to ultimately utilize these events as probes of black hole mass in distant quiescent galaxies in the LSST era. Finally I will provide an introduction to upcoming and proposed wide-field surveys that will help us address these issues in the coming years.

31
Speaker: Jason Rhodes
Institute: JPL
Host: D. Mawet

NASA's Next Astrophysics Flagship: The Wide Field Infrared Survey Telescope (WFIRST)

The top recommendation for a large space mission in the US 2010 Decadal Survey was the Wide Field Infrared Survey Telescope (WFIRST).  Similarities in hardware requirements between proposed dark energy, exoplanet microlensing, and near infrared surveyor missions allowed for a single mission that would accomplish all three goals.  The gift of an existing 2.4 meter telescope to NASA by another US government agency allowed for the addition of a coronagraph that will take images and spectra of nearby exoplanets; this instrument will be a technological stepping stone to imaging other Earths in the 2030s.  I will give an overview of WFIRST's proposed instrumentation, science goals, and implementation plan. I will delve into the details of a number of scientific and technical efforts in Pasadena that are paving the way for this ambitious and exciting mission.


NOVEMBER
7
Speaker: Decker French
Institute:  Univ of Arizona
Host: A. Faisst

TBD

14
Speaker: Tamas Budavari
Institute: John Hopkins Univ
Host: M. Graham

TBD

28

Speaker: Ken Shen
Institute: Berkeley
Host: J. Fuller

TBD

DECEMBER
5
Speaker: Jessie Christiansen
Institute: Caltech
Host: D. Mawet

TBD

12

Speaker: Laura Ferrarese
Institute: Gemini Obs.
Host: M. Kasliwal

TBD

JANUARY 9

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16

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23

Speaker: Alex Szalay
Institute: John Hopkins
Host: Mansi Kasliwal

TBD

30

Speaker: Yanqin Wu
Institute: Univ of Toronto
Host: Eve Lee

TBD

FEBRUARY
6

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13

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20

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27

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MARCH
6

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13

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20

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27

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APRIL
3

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10

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17

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24

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MAY
1

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8

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15

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22

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29

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JUN
5

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Information for Speakers

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