BBL 9/28/2020 — 3 Talks! Speakers: Shengqi Yang (NYU); Louise Welsh (Durham UK); Kishalay De (CalTech)
Monday September 28, 2020 12:00 pm
Shengqi Yang, New York University 12:00
Multitracer cosmological line intensity mapping mock lightcone simulation
Abstract: Sub-millimeter emission lines are important tracers of the cold gas and ionized environments of galaxies and are the targets for future line intensity mapping surveys. Physics-based simulations that predict multiple emission lines arising from different phases of the interstellar medium are crucial for constraining the global physical conditions of galaxies with upcoming LIM observations. In this work we present a general framework for creating multitracer mock sub-millimeter line intensity maps based on physically grounded galaxy formation and sub-mm line emission models. We simulate a mock lightcone of 2 deg^2 over a redshift range 0<z<10, comprising discrete galaxies and galaxy CII, CO, CI emission. We present simulated line intensity maps for two fiducial surveys with resolution and observational frequency windows representative of COMAP and EXCLAIM. We show that the star formation rate and line emission scaling relations predicted by our simulation significantly differ at low halo masses from widely used empirical relations, which are often calibrated to observations of luminous galaxies at lower redshifts. We show that these differences lead to significant changes in key summary statistics used in intensity mapping, such as the one point intensity probability density function and the power spectrum. It will be critical to use more realistic and complex models to forecast the ability of future line intensity mapping surveys to measure observables such as the cosmic star formation rate density.
Host: Frebel Group
Louise Welsh, University of Durham – UK at 12:20
The stochastic enrichment of near-pristine systems: Population II stars vs the most metal-poor DLAs
Abstract: In this talk, I will present a stochastic chemical enrichment model that uses the chemistry of near-pristine systems to infer the properties of the first generation of stars. This model accounts for the mass distribution of the enriching stellar population, the typical explosion energy of their supernovae, and the number of stars that have contributed to the enrichment. Using this model, I have investigated the enrichment history of both the most metal-poor Damped Lyman-alpha systems (DLAs; Welsh et al. 2019, 2020) and a sample of metal-poor Milky Way halo stars (Welsh et al. submitted). I have found that the number of massive stars that chemically contribute to a typical metal-poor halo star (~5) is comparable to the number of enriching stars inferred for the most metal-poor DLAs. Taken together, this analysis suggests that some of the lowest mass structures at z~3 contain the chemical products from <13 (2 sigma) Population III enriched minihaloes. The inferred IMF is consistent with a Salpeter distribution for both the DLA and stellar samples. Additionally, the stellar sample shows a preference towards enrichment from minimally mixed hypernovae. Finally, I will present the first bound on the carbon isotope ratio (12C/13C) of a near-pristine gas cloud (Welsh et al. 2020). This measurement allows us to place a limit on the relative importance of low mass (~1 Msun) Population III stars.
Host: Anna Frebel
Kishalay De, California Institute of Technology at 12:40
The dawn of wide-field infrared time domain astronomy with Palomar Gattini-IR
Abstract: Palomar Gattini-IR is a new wide-field near-infrared time domain survey operating from Palomar observatory in California. Using a 30 cm telescope mounted with a 2K X 2K detector, Gattini-IR achieves a field of view of 25 square degrees with a pixel scale of 8.7 X 8.7 arcsec. In this talk, I will present the system design, survey operations and data processing system of Palomar Gattini-IR. With a field of view 40 times larger than any other existing near infrared imager, Gattini-IR is performing the first un-targeted, all-sky census of the dynamic infrared sky to a depth of 16 AB mag and cadence of 1 – 2 nights. I will discuss first results from a broad range of infrared-bright time domain phenomena being systematically characterized with the survey — ranging from discovery of highly reddened classical novae in the Galactic plane, obscured outbursts from Young Stellar Objects, variability in dust obscured Galactic stars, reddened microlensing events in the Galactic plane and infrared bright supernovae in nearby galaxies.