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DTSTAMP:20260815T053040Z
LAST-MODIFIED:20190618T165211Z
DTSTART:20190626T173000Z
DTEND:20190626T183000Z
UID:event2144@bu.edu
URL:http://physics.bu.edu/internal/events/show/2144
SUMMARY:PROBING DARK ENERGY WITH LARGE-SCALE GALAXY CLUSTERING:   FROM INST
	RUMENTATION TO SIMULATION
DESCRIPTION:Featuring Yutong Duan\n\nPart of the PhD Final Oral Exams.\n\nE
	xamining Committee:  Steve Ahlen\, Martin Schmaltz\, Daniel Eisenstein\, Ed
	ward Kearns\, Alex Sushkov\n\nAbstract:\n\nMapping the Large-Scale Structur
	e of the universe at the Cosmic Frontier is a promising experimental avenue
	 which will address in the next decade several pressing open questions in c
	osmology and particle physics\, most notably the accelerating cosmic expans
	ion. The observed distribution of galaxies and quasars traces the underlyin
	g matter density field and contains a wealth of information from signatures
	 of primordial conditions to the background evolution rate. In this colloqu
	ium. I will describe our involvement in the instrumentation and in the anal
	ysis of cosmological N-body simulations. The Dark Energy Spectroscopic Inst
	rument (DESI) is a next-generation\, Stage IV dark energy experiment under 
	construction that will measure the expansion history of the universe throug
	h Baryon Acoustic Oscillations and the growth of structure through Redshift
	-Space Distortions. With an order of magnitude improvement over previous re
	dshift surveys\, DESI will place tight constraints on the dark energy equat
	ion of state\, modified gravity\, the existence of extra light species\, ne
	utrino masses\, and models of inflation. ProtoDESI was the first on-sky dem
	onstration of the critical DESI technology where we successfully acquired t
	argets with fibre positioners and maintained pointing stability. Using coor
	dinate measurement machines\, we performed complete metrology on the DESI f
	ocal plate structure and aligned 12 production petals to a projected optica
	l throughput of 99.88% ± 0.12% RMS\, ensuring minimal loss of photons at t
	he focal surface. Finally\, we quantify the shifts of the acoustic scale po
	tentially resulting from galaxy clustering bias\, which constitutes an incr
	easingly significant source of theoretical systematics in distance measurem
	ents with the standard ruler. Utilising mock catalogues based on generalise
	d halo occupation population of high-accuracy Abacus simulations in the lar
	gest volume to date for such tests\, 48 h⁻³Gpc³\, we find a 0.3% shift 
	in the line-of-sight acoustic scale for one variation in the satellite gala
	xy population and a 0.7% shift for an extreme level of velocity bias of the
	 central galaxies\, while other models tested are consistent with zero shif
	t at the 0.2% level after reconstruction. We note that these bias models pr
	oduce sizeable and likely distinguishable changes at small scales that corr
	elate with the shifts.
LOCATION:PRB 595\, 3 Cummington Mall\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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