Research Report for 2022

Professor Patrick Hartigan's research involved the formation of stars, stellar jets, emission nebulae, the physics of shock waves, laboratory astrophysics and time-domain astronomy in 2022. A full list of publications is available on the Web, as are overview pages that describe research areas of young stars and stellar jets.

Massive Star Forming Regions/JWST:Hartigan is leading a project to obtain orbital parameters for newly-discovered young eclipsing binaries in the Carina massive star formation region. Eclipsing binaries are the most reliable way to test pre-main-sequence evolutionary tracks because the primary and secondary must have the same ages. The eclipsing binary data allows us to measure the radii and temperatures of each star accurately, making it possible to find their individual ages. Only a handful of young eclipsing binaries are known, so new discoveries of these objects are an important constraint to the theory. We have spectra of several candidate young stars with the 4-m SOAR telescope in Chile.

Hartigan is a collaborator on one of the fifteen large proposals accepted in the first round for the James Webb Space Telescope (JWST; O. Berne PI). The project observed the Orion Bar region to show how the various instruments on JWST help to clarify the physics of dust and gas in the PDR, as well as the lifetimes of evaporating protostellar disks in the region. Several papers are forthcoming and are in various stages of preparation and submission.

Stellar Jets: A second project, led by B. Nisini in Rome, images regions very close to protostars in an attempt to learn how jets are launched. The Hubble Space Telescope portion of this project was published in 2021 in the Astrophysical Journal, and a companion project with the James Webb Space Telescope has now been approved and should begin acquiring data sometime in 2023.

Rochester graduate student Robert Markwick completed a study of colliding hydrodynamic flows in order to identify the instabilities that are present when strong cooling exists in the postshock gas. The results of this work emphasized the importance of the thin shell instability, and were published in Physics of Plasmas in 2022.

ALMA Studies of Photodissociation Regions:With Rice professor Andrea Isella, graduate student Maxwell Hummel, and Dublin City University professor Turlough Downes, Hartigan published a large paper in the Astronomical Journal concerning a bright region of photodissociation in the Carina Nebula. The paper was based on integrating existing Gemini adaptive optics molecular hydrogen images with new data cubes of three isotopologues of CO and C acquired with with the the Atacama Large Millimeter Array in Chile. The data show a clear progression from H2 to CI to CO as one proceeds deeper into the PDR. We identified 254 distinct clumps of C18O within the molecular cloud and found most of the clumps were near the boundary of stability, with less massive clumps more unbound. While there is some flattening along the PDR front, there are no well-defined pillars that might be interpreted as triggered star formation.

A second paper, led by Downes, used the CO datacubes to quantify turbulent length scales in the cloud. This paper has been accepted by MNRAS and will appear sometime in early 2023. . 

Time Domain Studies:In 2019, Hartigan led a team that successfully acquired a full month of time on the Blanco NOAO 4-m telescope in Chile to study variability in the Carina star formation region with the Dark Energy Camera (DECam). This imager has a full field of view of over 2 degrees, and is ideal for monitoring light variations of the thousands of young stars present in this region. Variability holds clues to many aspects of the star formation process, including rotational properties, obscuration by dusty envelopes, starspot coverage, accretion and flares. We continue to reduce and analyze these data. Results from the project will presage what the Large Synoptic Survey telescope may accomplish in this arena.

UC Irvine graduate student and former Rice undergraduate Rae Holcomb published her study of rotation periods from TESS satellite data using an algorithm she began developing while at Rice. The work appeared in the Astrophysical Journal in 2022. The study uncovered a hitherto unknown population of rapidly-rotating M-stars.

Large Synoptic Survey Telescope and a future UV Space Telescope:  Hartigan is part of the Transient and Variable Stars group of the Large Synoptic Survey Telescope, a facility under construction in Chile that will survey the entire sky visible from that location every three days. These data will usher in a new era of `time-domain astronomy', requiring astronomers to sort through vast amounts of data in a short time. Hartigan is part of a team that assessed the optimal temporal cadence for young stars and the work was published in PASP.

Laboratory Astrophysics:  Hartigan was a Co-I on two laboratory experiments whose results were published in in 2022. The first paper was led by Joseph Levesque (Michigan/Los Alamos) and appeared in the journal Physics of Plasmas, and explored how structured magnetic fields affect the location of a magnetized bow shock created from a supersonic flow driven by a powerful laser. The second work was led by Danny Russell at Imperial College in London and was published in Phys. Rev. Letters. The experiment produced the first subcritical shock in a collisional plasma, and compared the results with theoretical expectations.

Campus Observatory and Outreach Activities: The Rice University Campus Observatory (RUCO), located on the roof of the Brockman Physics building continues to be the workhorse for our undergraduate major and nonmajor courses. We have a working wide-field CCD with seven filters, and have tested out a new Shelyak spectrometer for use in the lab. We are focusing a great deal of effort to track down an unknown vibration source that has been affecting observations.  Hartigan gave several interviews regarding the James Webb Space Telescope and eclipses during the year. Observatory schedules can be found on the observatory website.

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Patrick Hartigan