Presentation Title

Star Formation Rate Indicators in the FIRE Galaxy Formation Simulations

Faculty Mentor

Professor Claude-André Faucher-Giguère

Start Date

18-11-2017 1:45 PM

End Date

18-11-2017 2:00 PM

Location

9-279

Session

Physical Sciences 1

Type of Presentation

Oral Talk

Subject Area

physical_mathematical_sciences

Abstract

Understanding the rate at which stars form is vital to understanding galaxy formation. Observationally, the star formation rates (SFRs) of galaxies are typically measured using light in different bands under the assumption of a time-steady SFR. We use galaxy formation simulations from the Feedback In Realistic Environments (FIRE) project, which in some regimes predict time variable (bursty) SFRs, to analyze the timescales probed by H-alpha and far ultraviolet (FUV) SFR indicators. We also quantify the possible dependence of SFR indicators on SFR variability. Our preliminary results based on a Milky Way-mass galaxy simulation indicate that the best-fit timescales probed by these indicators do not depend significantly on whether the SFR is bursty, with best- fitting timescales of about 4 Myr for H-alpha and about 10 Myr for FUV in both the time-steady and bursty regimes.

Summary of research results to be presented

Our project is motivated by desiring to test the assumption made when calibrating SFR indicators: that SFR is constant for a period of time. However, simulations like FIRE and observations like: Shivaei et al. 2015, Guo et al. 2016, and Shimakawa et al. 2017 suggest time variable (bursty) star formation. We use the self-consistent star formation histories realized in the simulation to quantify differences between observationally-inferred SFRs. We analyze the SFR indicators probed by Far Ultra Violet (FUV) light and Recombination lines, (Hα) which probe 10-100 Myr and 3-10 Myr respectively. We calculate the SFRs probed by FUV light and Hα in periods of time when the galaxy experiences bursty and non-bursty star formation and compare to the true SFRs in the simulation in order to predict the averaged time scales on which the true SFR is best measured by the indicator. Preliminary results suggest the best-fit averaged timescale is not sensitive to whether it is estimated in the bursty regime or the non-bursty regime. The Hα indicator works best at an averaged time scale of 4 Myr and the FUV works best at an averaged time scale of 11 Myr.

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Nov 18th, 1:45 PM Nov 18th, 2:00 PM

Star Formation Rate Indicators in the FIRE Galaxy Formation Simulations

9-279

Understanding the rate at which stars form is vital to understanding galaxy formation. Observationally, the star formation rates (SFRs) of galaxies are typically measured using light in different bands under the assumption of a time-steady SFR. We use galaxy formation simulations from the Feedback In Realistic Environments (FIRE) project, which in some regimes predict time variable (bursty) SFRs, to analyze the timescales probed by H-alpha and far ultraviolet (FUV) SFR indicators. We also quantify the possible dependence of SFR indicators on SFR variability. Our preliminary results based on a Milky Way-mass galaxy simulation indicate that the best-fit timescales probed by these indicators do not depend significantly on whether the SFR is bursty, with best- fitting timescales of about 4 Myr for H-alpha and about 10 Myr for FUV in both the time-steady and bursty regimes.