Cosmology Lunchtime Seminar

Week of Monday, January 20th 2020

Monday, January 27th 2020
12:15 pm:
Speaker: Najmeh Emami, University of California, Riverside
Subject: Understanding Bursty Star Formation in Dwarf Galaxies, Its Effect on Galactic morphology, and Implications for Reionization

Dwarf galaxies -- low-mass galaxies with stellar masses below 10^9 M_Sun -- are the most abundant galaxies in the universe. Due to their shallow gravitational potential well and small gas reservoirs, dwarfs are easily disrupted by supernovae feedback and can lose a fraction of their cold gas to the intergalactic medium in the form of outflows. Implementation of feedback into the hydrodynamical simulations suggest that this phenomenon leads to a stochastic star formation history in these low-mass systems called "burstiness". Burstiness can cause a large variation of many physical quantities such as metallicity, morphology, radial velocity, dark matter density profile, etc. and can reconcile the discrepancies between the predictions from cold dark matter and observations in near-field cosmology. In the first part of my talk, I will describe our method of characterizing burstiness using two different star formation rate indicators that are sensitive to the recent and current star formation changes. We use exponentially rising/falling burst models to determine the timescales and amplitudes of the bursts for each mass bin and compare the results to the simulations and other models. In the second part of the talk, I will discuss the importance of dwarfs to the reionization of the universe and describe our measurement of "xi_ion" as one of the key components in determining the ionizing emissivity of dwarf galaxies. Lastly, I will talk about the effect of burstiness on the morphology of dwarf galaxies. In particular, I will examine the effect of burstiness on galaxy size fluctuation and will conclude this by interpreting the relationships between this quantity and other star formation rate indicators

Faculty Host: Patrick Kelly

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