About Me

Welcome! I'm a Phoenix native currently living in Cologne, Germany as a postdoctoral researcher in Prof. Stefanie Walch's research group. I received my PhD from the University of Massachusetts in 2019.

My research interests revolve around studying protostellar feedback effects on molecular cloud chemistry. I make use of high powered computing facilities performing astrochemical and magnetohydrodynamic simulations. Star formation is, by necessity, viewed through the a lens of emission from a wide range of molecules. Therefore, it is essential to determine the footprint various physical processes make on the large scale chemistry of molecular clouds. My work has involved studying protostellar FUV feedback, cosmic ray acceleration in protostellar accretion shocks, and developing coupled chemistry-hydrodynamic in the Orion2 code.

Turbulence Statistics and Chemistry [ADS]

Molecular clouds have, by their very nature, complicated density structures. This complication means comparing observables and physical properties from simulations can be difficult. Therefore, astronomers must rely on calibrated statistics to compare to observed clouds. There are numerous proposed statistics, each of which are sensitive to different physics. It has become clear that synthetic observations must be performed of simulations to properly compare to observations. The image on the top left are synthetic observations of asimulated molecular cloud, showing how the observed spatial structure of the cloud significantly changes through different molecular lenses.

FUV Feedback From Protostars [ADS]

Star formation is far from quiescent. Protostars eject large collimated jets, nearly spherical winds, and radiatively heat the gas around them. Radiation in the far ultraviolet (FUV), photons with energies between 5 and 13.6 eV, can lead to large scale astrochemical imprint. The image of the right is an example of protostars shining in FUV emission from a simulated molecular cloud. Performing calculations in situ is currently numerically expensive. Therefore, I have focused on performing 1-dimensional astrochemical models coupled to analytic protostellar accretion models across a wide range of molecular cloud and protostar cluster masses. Currently in development are 3-dimensional MHD simulations including ray-tracing to calculate the impact of FUV emission within molecular clouds.

Protostellar Cosmic Rays [ADS]

Interactive Cosmic Ray Ionization Rate Tool

Historically, it was widely assumed that molecular clouds were bathed in a nearly uniform field of cosmic rays, highly energetic charged particles flung through space nearly at the speed of light by violent events. Recent theoretical develops (i.e. Padovani+2009) have shown that cosmic rays from external sources would be decreased as they travel into the cloud. However, recent observations from the Seeds of Life in Space (SOLIS) collaboration, Ceccarelli+2014, and Favre+2017 have inferred cosmic ray ionization rates higher than, or equal to, the measured rates in diffuse clouds. The solution may in fact be the protostars themselves, suggested by Padovani+2016.

My work has involved coupling analytic protostellar accretion models self-consistently with shock models to calculate the acceleration of cosmic ray protons. An example cosmic ray spectra, with protons and secondary electrons as solid and dotted lines, respectively, is on the left for a 0.5 Solar Mass star as a function of its final mass. We have shockingly found that protostars are able to efficiently accerate cosmic rays throughout their envelope. Furthermore, for clouds hosting more than a couple of hundred protostars, the amount of cosmic rays being accelerated from their internal sources is able to compete with those impinging on their external boundaries.


  • 2019: Offner, S. S. R., Gaches, B. A. L., Holdship, J., ApJ, Impact of Cosmic-Ray Feedback on Accretion and Chemistry in Circumstellar Disks [ADS]
  • 2019: Gaches, B. A. L., Offner, S. S. R., Bisbas, T. G., ApJ, The Astrochemical Impact of Cosmic Rays in Protoclusters. II. CI-to-H2 and CO-to-H2 Conversion Factors [ADS]
  • 2019: Gaches, B. A. L., Offner, S. S. R., Bisbas, T. G., ApJ, The Astrochemical Impact of Cosmic Rays in Protoclusters. I. Molecular Cloud Chemistry [ADS]
  • 2018: Gaches, B. A. L., Offner, S. S. R., ApJ, Exploration of Cosmic Ray Acceleration in Protostellar Accretion Shocks and A Model for Ionization Rates in Embedded Protoclusters [ADS]
  • 2018: Gaches, B. A. L., Offner, S. S. R., ApJ, A Model for the CO-H2 Conversion Factor of Molecular Clouds with Embedded Star Clusters [ADS]
  • 2015: Gaches, B. A. L., Offner, S. S. R., Rosolowsky, E. W., Bisbas, T. G., ApJ, Astrochemical Correlations in Molecular Clouds - [ADS]


  • AAS Summer 2012 - Anchorage, AK. Tensor Smoothed Particle Hydrodynamics. [ADS]
  • UMass HPC Day 2014 - Dartmouth, MA. Astrochemical Correlations in Molecular Clouds. Award winning poster
  • NRAO Filaments Conference 2014 - Charlottesville, VA. Astrochemical Correlations in Molecular Clouds.
  • From Clouds to Protoplanetary Disks: The Astrochemical Link - Berlin, Germany, October 2015
  • From Stars to Massive Stars - Gainesville, FL, USA, April 2016
  • European Week of Astronomy and Space Science - Prague, Czech Republic, June 2017

Talks and Workshops

  • Contributed: AAS Winter 2019 - Seattle, WA
  • Seminar: ITC Seminar October 2018 - Center for Astrophysics, Cambridge, MA
  • Seminar: Origins Seminar October 2018 - Steward Obsevatory, Tucson, AZ
  • Seminar: TUNA Talk September 2018 - NRAO, Charlottesville, VA
  • Contributed: The Olympian Symposium 2018 - Paralia Katerini, Mount Olympus, Greece
  • Attendee: Krome School 2016 - Florence, Italy
  • Invited: UMass, Ahmerst HPC Seminar - April 15, 2015
  • Contributed: AAS Summer 2014 - Boston, MA. Astrochemical Correlations in Molecular Clouds