Our galaxy’s spitballs: Modeling the Evolution of Fragments Produced in Tidal Disruption Events Eden Girma, Harvard College Dr. James Guillochon, Harvard Institute for Theory and Computation

What’s going on? But wait! Jupiter-mass fragments forming in stream Adapted from Rees, 1988 3. Star is "spaghettified" into a long, smooth stream (?) 1. Star passes very close to a supermassive black hole A star is disrupted by a supermassive black hole roughly once per ten thousand years per galaxy, if a hundred planets form per strand, that means over the history of a galaxy (say the Milky Way), there will be 100*1e-4/yr*1e10 yr = 100 million planets produced this way in and around our galaxy! IMAGE: Density two years after disruption and, in the insets, close-ups of the fragments that forms along the stream. Eric coughlin, Einstein Postdoctoral Fellow at the University of California at Berkeley. But wait! 2. Star experiences ‘distortion’ by tidal forces exerted upon it. Credit: Coughlin, 2015

Simulation Process Video: Evolution of fragments produced from 50 disruptions, over 107 years The sun

Simulation Results Probability Distance Probability Probability Girma+ 2017 (in prep) 613 10,860 Simulation Results Probability 88.9% Distance Probability Distance 77.5% 21.6% <1% Distance Probability

Distance to the nearest fragment Using our data, we can find the number of fragments given a surveying radius from our sun: 8 kpc 1 kpc shell rmin = 200 parsecs

New insights ... A majority of fragments produced by TDEs in our galaxy are unbound to the black hole traveling at hyper-velocity speeds Bound fragments produced by TDEs in our galaxy are more likely to possess tightly bound orbits around Sgr A* The nearest fragment may be as near as 200 parsecs (~700 light-years) only 0.326% of fragments travel within a spherical shell of thickness 1 kpc at a distance 8 kpc from the galactic center. Image Credit: James Guillochon

New insights ... and Additional Questions How can we find these fragments, and what will they look like? Extremely cold – visible in infrared, not so much in optical (JWST and microlensing/LSST) Requires more in-depth simulation of their cooling process What about TDEs occurring in other galaxies? The Virgo Cluster, 20 Mpc away NGC 1300, 18.7 Mpc away Tadpole Galaxy, 129 Mpc away Artwork by Mark Garlick only 0.326% of fragments travel within a spherical shell of thickness 1 kpc at a distance 8 kpc from the galactic center.

Thank you! Acknowledgements Dr. James Guillochon, Harvard CfA Prof. John Johnson and Prof. Jorge Moreno, The Banneker and Aztlán Institutes American Astronomical Society All of you here  Thank you!