Steward Observatory grad student Lucy Steffes wins multiple awards for her poster on prestellar cores
Steward Observatory graduate student Lucy Steffes has won two prizes for her poster, titled “Preliminary Results on a Survey of Deuterated Methanol and Ammonia in Prestellar Cores in Ophiuchus – Comparison Deuteration Chemistry on Icy Dust Grains and in the Gas Phase”
Lucy Steffes, a first-year graduate student in the Astronomy Department at The University of Arizona, is on a winning streak: in March, her poster—titled “Preliminary Results on a Survey of Deuterated Methanol and Ammonia in Prestellar Cores in Ophiuchus – Comparison Deuteration Chemistry on Icy Dust Grains and in the Gas Phase”—won second prize at a ESO meeting in Garching, Germany. Now, Lucy’s poster has won a Chambliss Award at the AAS meeting in Anchorage, Alaska.
View Lucy’s winning poster here.
Of Lucy’s awards, her advisor Yancy Shirley—astronomy professor for the Department of Astronomy and astronomer at Steward Observatory—notes that the molecular cloud Ophiuchus, the object of Lucy’s study—is only observable for a couple of hours each day, so her survey is the compilation of many months of observing shifts to build up a statistically significant sample of prestellar cores. Lucy organized and trained a team of undergraduate students to assist with some of the observing: current Astronomy Majors Chase McMahon, Emma Vertachnik, Julien Barrosse, Aaron McCray, and Anna Brandigi. Alongside her team, she has spent many late nights and early mornings on her research while also taking classes and doing all the things expected of a first-year graduate student.
“It’s awesome to see Lucy’s hard work being recognized by the community,” said Shirley. “It’s a pleasure working with such a talented and dedicated student, and I look forward to seeing which directions she will be taking her thesis research.”
Lucy Steffes presents her winning poster at the AAS meeting in Anchorage, Alaska.
Background on Lucy’s research
Long before stars ignite and planets take shape, the ingredients for stellar formation condense in giant clouds of gas and dust known as molecular clouds. Within these molecular clouds, there are dense regions, called prestellar cores, which are bound by the cores’ gravity and the external pressure of the surrounding cloud. Prestellar cores are the earliest observable phase of star formation, existing prior to the formation of a protostar and a nascent planetary system.
It is important to understand how the molecular chemistry evolves in prestellar cores as they set the initial chemical conditions for future planet formation. One tool to study this chemical evolution is deuterium fractionation. Deuterium, a heavy isotope of hydrogen, typically has an abundance ratio of 1 deuterium atom to 70,000 hydrogen atoms in the gas between the stars. In the very cold (~10 K) molecular gas inside prestellar cores, this ratio can “fractionate” or increase by factors of more than 1000 over hundreds of thousands of years. Therefore, deuterium fractions of molecules may be used as a chemical evolution indicator – the higher the deuterium fraction, the longer the prestellar core has spent at a particular density and temperature.
Not all molecules form and fractionate in the same way with some molecules, such as ammonia, primarily forming and fractionating in the gas phase and other molecules, such as methanol, primarily forming and fractionating on the icy surfaces of dust grains.
Lucy’s work
High in the Arizona mountains, Lucy Steffes is tuning in to the chemical whispers of star formation, using a radio telescope to understand the evolution of one of the nearest molecular clouds to the Sun. Lucy is using the Arizona Radio Observatory 12m telescope on Kitt Peak to perform the first large scale deuterium fraction study of the Ophiuchus Molecular Cloud (420 lightyears away). She is observing deuterated versions of ammonia and methanol to probe both ways of fractionating, and she is finding that the methanol deuterium fraction in Ophiuchus is remarkably like the ratio observed toward deeply embedded protostars in the next phase of star formation indicating that there is chemical inheritance from the prestellar core phase to the protostellar core phase.
Lucy is also finding systematic chemical differences in the deuterium fractions between Ophiuchus and other nearby molecular clouds, such as the Taurus Molecular Cloud (450 light years away). Her findings suggest that even before stars and planets are born, the chemistry that shapes them is already being written.
This research is supported by a National Science Foundation Astronomy and Astrophysics Grant, and observing will be completed in the Fall of 2025.