I study planet-forming disks around nearby young stars using submillimeter interferometers, principally ALMA in Chile, and the SMA and JCMT on Maunakea. I also use optical and infrared telescopes to characterize the host stars. My previous work included large scale molecular cloud structure and clustered star formation. These subjects link to my current focus on disks through the broad goal of placing our solar system in context, and reconciling astronomical observations with meteoritic constraints on our origin.
Understanding the origins of our Solar System and the tremendous diversity of exoplanetary systems are key questions in modern astronomy. Primarily using (sub-)millimeter wavelength telescopes, we have been measuring the dust and gas content of protoplanetary disks in different regions to learn about the initial conditions and timescale for forming exoplanets. The Atacama Large Millimeter Array is poised to revolutionize many of the issues discussed in our pre-ALMA review.
We can readily measure the solid content (aka dust) in protoplanetary disks from millimeter continuum observations. Measuring the gas mass is much harder but we think we have a way and we are currently working on expanding our parametric modeling to infer gas surface densities. This is now being applied to new large ALMA surveys.
During my ~25 years as an astronomer, I have followed the advances in radio instrumention to go from studying molecular clouds to individual star formation in dense cores and now to planet formation in disks. Some of this work is summarized in a Protostars and Planets IV review, or at this old research page.
The most long-lasting impact of this is an algorithm, CLUMPFIND, that I developed to analyze the structure in 3-d datasets from spectral line mapping and which, to my amazement, continues to be used today!
- See ADS link below
The Interstellar Medium (ISM) is the gas and dust between the stars. Stars form from it, their winds and supernova enrich and replenish it. Temperatures in the ISM range from the very hot, ~106 K, to the very cold, ~10 K. Densities span an even wider dynamic range, from less than 10-3 to greater than 106particles per cubic centimeter. Even the highest densities, however, are far more rarefied than the best vacuums currently attainable on Earth and thus the ISM allows us to explore physical processes in unique environments. This course will discuss observations and theories of a wide range of ISM environments from pervasive diffuse, ionized gas to dense, molecular clouds and star forming regions. In the last part of the course, we will transition from interstellar to circumstellar material (i.e. disks) as this is an active area of research at the IfA.
(taught 2004, 2006, 2008, 2009, 2012, 2014, 2016)
Estimation is an essential skill for astronomy and life in general. This course will introduce students to the utility of order of magnitude calculations and practicing the ability to “think on your feet”. I will give short overviews of basic physical concepts but the majority of the class time will be spent interactively, with students tackling pre-assigned problems at the whiteboard. If time permits, I will challenge the class by extending the problem or asking a new, unseen question.
(taught Spring 2015)
This series of seminars will introduce students to radio astronomy and inteferometry. The course will be split roughly evenly between lectures on the techniques and applications of observing at submillimeter wavelengths and practical work using real data. For the latter, we will use ALMA science verification datasets and work through the associated tutorials on data reduction and analysis. Students will need a laptop computer running (Mac OS) unix or linux. The goal is for students to learn the skills of submillimeter astronomy and interferometry so as to be able to propose for SMA, ALMA, or JVLA observations in their chosen science area.
(taught Spring 2003, Spring 2013)
How did the Earth and other planets form? How common are planets around other stars, and what are their properties? These questions are at the forefront of the earth and space sciences and are the modern manifestations of questions about our origin and uniqueness that are probably as old as human consciousness itself. Observations and measurements have almost always preceded theory in this field of inquiry, and hence this course is structured according to the three windows through which almost everything has been learned in this field: (1) astronomical observations of the process of star and planet formation; (2) measurements of early events recorded in Solar System materials, and detection and (3) characterization of planets around other stars.
(co-taught with Sasha Krot and Eric Gaidos, Spring 2006)
This is a non-mathematical, introductory class for undergraduate non-science majors. I give a broad overview of astronomy from planets to quasars. Click on the link above for the course web page.
(taught Spring 2005, Fall 2010)
AURA Member Representative, 2014 – present
ALMA Science Advisory Committee, 2007 – 2008, 2010 – 2012
ALMA North American Science Advisory Committee, 2005 – 2008 (Chair, 2006-2007), 2010 – 2012
JCMT Board member, 2003 – 2006, 2008 – 2014
SMA Advisory Committee, 2003 – 2006
CSO Time Allocation Committee, 2002 – 2006
AAS Committee for the Status of Minorities in Astronomy, 2002-2007
Editor of the Test Bank for The Cosmic Perspective. 2000-2006
Participant in AAS Congressional Visits Day, 2001
Panelist for NSF, NASA, ERC grant review committees 2002+
Panelist for HST, NRAO, and NOAO time allocation committees 2000+ (HST panel chair 2014)
Referee for Nature, Science, ApJ, AJ, A&A, MNRAS, PASJ, Ap&SS
SOC for >10 meetings from 2005+
Graduate Chair, 2016 – present
Faculty Chair, 2012 – 2014
Astronomy Personnel Subcommittee, 2011 (Chair)
Graduate Research Oversight Group, 2011 – 2014
Director Search Committee, 2011
University Research Council, 2008 – 2011
Faculty Advisory Committee, 2006 – 2009
Faculty Review Committee, 2006 – 2009
Scientific Staff Screening Committee, 2009 – 2012
Graduate Admissions Committee, 2004 – 2006 (Chair, 2006), 2010-11
Qualifying Exam Committee, 2005 – 2006, 2009 – 2011
Telescope Time Allocation Committee, 2003 – 2005, 2011
- PI of NSF, NASA, and NRAO grants
- NSF CAREER awardee
- NRAO Jansky fellow
- The Berkeley Fellowship for Graduate study
- Scholarship, Queens' College, Cambridge University
- Megan Ansdell
- Greta Guidi (visiting student from Italy)
- Chris Beaumont (PhD 2013)
- Geoff Mathews (PhD 2012)
- Rita Mann (PhD 2010)
- Sean Andrews (PhD 2007)
- Sandrine Bottinelli (PhD 2006)
- Catherine Garland (PhD 2004)
- Christian Flores (699-1 MS 2016)
- Conor McPartland (699-2 MS 2015)
- Ehsan Kourkchi (699-1 MS 2013)
- Will Best (699-2 MS 2012)
- Nicholas Lee (699-2 MS 2010)
- Chian Chou-Chen (699-1 MS 2009)
- Nienke van der Marel
- Lucas Cieza (2010-2014)
- Jagadheep Pandian (2008-2011)
- Jon Swift (2005-2008)
- Thomas Stanke (2003-2005)