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DTSTART;TZID=UTC:20251113T180000
DTEND;TZID=UTC:20251113T190000
DTSTAMP:20260516T032240
CREATED:20251113T150529Z
LAST-MODIFIED:20251126T061455Z
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SUMMARY:CASSA Colloquium 9: Photometric Redshifts for Next-Generation Sky Surveys
DESCRIPTION:Speaker (online): Biprateep Dey\, PhD\, Postdoctoral Fellow\, Department of Statistical Sciences\, University of Toronto\, Canada. \nTitle: Photometric Redshifts for Next-Generation Sky Surveys \nAbstract: Knowing the distances to galaxies as measured by their cosmological redshift is crucial for studies of cosmology\, galaxy evolution\, and astronomical transients. The next generation of astronomical imaging surveys (like LSST\, Euclid\, and Roman Observatories) will all be critically dependent on estimates of galaxy redshifts from imaging data alone; the resulting measurements are called photometric redshifts or photo-z’s. Traditional photo-z estimation methods only use measures of total light received from a galaxy (colors and magnitudes) as inputs\, thereby\, throwing away the rich pixel-level information present in images. Moreover\, the uncertainty estimates produced by these methods are not statistically well defined and the availability of data to train these methods is scarce. I will present my work on developing new deep learning-based photo-z estimation methods that take images directly as inputs and provide state-of-the-art photo-z prediction accuracy while being interpretable and requiring less training data. I will also talk about a statistical formalism that I developed to produce well-calibrated photo-z uncertainty estimates that are method-agnostic and employ minimal assumptions. Finally\, I will also provide an overview of our recent efforts to obtain spectroscopic samples to train for photo-z algorithms using the Dark Energy Spectroscopic Instrument (DESI).
URL:https://cassa.site/event/colloquium-9/
LOCATION:CASSA\, IUB Main Building Rooftop\, Plot 16\, Aftabuddin Ahmed Road\, Block B\, Bashundhara RA (Main Building Rooftop)\, Dhaka\, 1229\, Bangladesh
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/webp:https://cassa.site/wp-content/uploads/2025/10/dey.webp
ORGANIZER;CN="CASSA%2C Independent University%2C Bangladesh":MAILTO:cassa@iub.edu.bd
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DTSTART;TZID=UTC:20251120T180000
DTEND;TZID=UTC:20251120T193000
DTSTAMP:20260516T032240
CREATED:20251120T134604Z
LAST-MODIFIED:20251126T061318Z
UID:6122-1763661600-1763667000@cassa.site
SUMMARY:CASSA Colloquium 10: Probing galaxy evolution using massive early-type galaxies at intermediate redshift
DESCRIPTION:Speaker (online): Pritom Mozumdar\, Postdoctoral Researcher\, Department of Physics and Astronomy\, University of California\, Los Angeles\, USA. \nTitle: Probing galaxy evolution using massive early-type galaxies at intermediate redshift \nAbstract: Over the past 8 billion years (since redshift\, z ~ 1)\, the Universe – and the galaxies within it – have changed dramatically. Cosmological simulations suggest that massive early-type galaxies (ETGs)\, which are large\, old systems mostly made of stars\, have slowly transformed in their internal structure during this time. However\, observational evidence of these transformations at intermediate redshift ( z ~ 0.5) isn’t conclusive and sometimes even seems to disagree with what simulations predict. One major reason is the lack of statistically large sample of ETGs with high-quality data at intermediate redshifts. To fill this gap\, I assembled a sample of around 200 massive ETGs at 0.25 < z < 0.75. With this dataset\, I addressed two big questions – 1) Have the stars in these galaxies become more randomly moving\, that is\, have their motions become less ordered\, over cosmic time? 2) Has the overall distribution of mass\, including both stars and dark matter\, changed as the Universe aged? By comparing these galaxies to similar ones in today’s Universe (z ~ 0)\, I found evidence that both the stellar motions and the mass distributions have evolved – offering new clues about how massive galaxies grew and changed over cosmic history.
URL:https://cassa.site/event/colloquium-10/
LOCATION:CASSA\, IUB Main Building Rooftop\, Plot 16\, Aftabuddin Ahmed Road\, Block B\, Bashundhara RA (Main Building Rooftop)\, Dhaka\, 1229\, Bangladesh
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/webp:https://cassa.site/wp-content/uploads/2025/10/mozumdar.webp
ORGANIZER;CN="CASSA%2C Independent University%2C Bangladesh":MAILTO:cassa@iub.edu.bd
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