Events Calendar

A search for high-redshift galaxies..., Benne Holwerda

Date:
Thursday, October 18, 2018
Time:
1:30 pm - 2:30 pm
Location:
Physics & Astronomy Building (PAB)
Room: 100
Department of Physics & Astronomy
London, Ontario
Cost:
Free

Department of Physics and Astronomy

PHYSICS & ASTRONOMY COLLOQUIUM

Dr. Benne W. Holwerda

Department of Physics & Astronomy
University of Louisville

“A search for high-redshift galaxies and an accidental galactic survey of dwarf stars with Hubble”

ABSTRACT

Current searches for high-redshift galaxies use a combination of near-infrared filters with one or more optical filters to check for contaminants. One of these contaminants are faint dwarf stars in the disk and halo of our own Milky Way Galaxy. Thus in the search for the galaxies that caused the Reionization of the Universe, an accidental census of Dwarf stars in the Milky Way was conducted as well. I report on one observational approach with the Hubble Space Telescope; the Brightest Origin of Reionizing Galaxies (BORG) survey. 

I will discuss the identification of the distant high-redshift galaxies, their unique properties, the faint brown and red dwarf stars (M-dwarfs) and our results on characterizing the shape of the Milky Way from their number. We identified stellar objects in the BoRG survey and mapped their distribution onto the Milky Way. Results are a thin disk (300pc), the rediscovery of the Sagittarius stream, a total count of 58 billion M-dwarfs in the Milky Way of which 7% reside in the halo. We also found a population of very bright, redshift eight galaxies (“Super-Eights”) that show evidence for strong nebular emission lines and direct observations of Lyman-alpha.

These M-dwarfs may be useful to register the on-sky position of NASA/ESA’s new flagship telescope, the James Webb Space Telescope and as a science by-product of ESA’s EUCLID or NASA's WFIRST telescope. The Super-Eights appear to reveal a very specific mode of star-formation that may have played a critical role in the Reionization of the Universe. I will discuss future prospects.

STUDENTS – after the talk, you’re encouraged to return to the 2nd floor Atrium lounge to meet with the speaker.
COFFEE – coffee and cookies will be available in the 2nd floor Atrium lounge at 1:15 p.m.
CELL PHONES – as a courtesy to the speaker and audience, please set your cellphones to “silent” mode. Thanks!
Host:
Prof. P. Barmby
Contact:
Jodi Guthrie - Assistant to the Chair
jodi@uwo.ca
519-661-2111 x.86438
Event Type:


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