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DTSTART:20250101T000000
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DTSTART;TZID=UTC:20260519T133000
DTEND;TZID=UTC:20260519T141500
DTSTAMP:20260604T071631
CREATED:20260518T111837Z
LAST-MODIFIED:20260518T115102Z
UID:9691-1779197400-1779200100@cassa.site
SUMMARY:Journal Talk 19: Imtiaz et al. (2026 (expected))
DESCRIPTION:Resolved Metallicity and Age Gradients in the Lensed Quiescent Galaxy AGEL0014 at z ≈ 1.4. \n[Based on research done under supervision of Dr. Nicha Leethochawalit\, Researcher at National Astronomical Research Institute of Thailand (NARIT)] \nAbstract: The formation and quenching mechanisms of massive galaxies at high redshift remain a focal point of galaxy evolution studies. We present a spatially resolved stellar population analysis of the lensed quiescent galaxy AGEL0014 (z ≈ 1.4) to constrain its formation history. Combining HST (F814W )\, Gemini/GSAOI (H\, J\, Ks)\, and Keck/MOSFIRE (J\,Y ) data\, we modeled the system using Lenstronomy. To robustly recover intrinsic stellar population trends given the seeing (≈ 0.4′′)\, we forward-modeled source plane metallicity gradients\, applying light-weighting and PSF convolution to the projected image-plane map to simulate slit data. Full spectrum fitting with the alf (Absorption Line Fitter) code reveals a clear positive age gradient and a negative metallicity gradient. The central region exhibits log(Age/Gyr) = 0.37 ± 0.05 and [Z/H] = −0.31 ± 0.11\, while the outer region hosts an older population with log(Age/Gyr) = 0.49 ± 0.07 and [Z/H] = −0.53 ± 0.10. Interestingly\, [Fe/H] increases from 0.01 ± 0.11 in the core to 0.19 ± 0.10 in the periphery. These signatures support an outside-in quenching scenario: the high α-enrichment in the core suggests it formed in a short\, intense burst and quenched abruptly\, whereas the iron-rich outskirts imply a more extended star formation history allowing for enrichment from Type Ia progenitors. \nLink: https://docs.google.com/presentation/d/1plgX7tQJdRSfYA3rwAsktoAbKSD9Am6z/edit?usp=sharing \nPresenter: Ahmad Al-Imtiaz (Graduate Research Assistant at CASSA; M.Sc. in Physics from Shahjalal University of Science & Technology) \n\nTo get notified\, subscribe using the Google Form: \nhttps://forms.gle/fikhmc7Y2whjJWKK9
URL:https://cassa.site/event/jtalk-19/
LOCATION:CASSA\, IUB Main Building Rooftop\, Plot 16\, Aftabuddin Ahmed Road\, Block B\, Bashundhara RA (Main Building Rooftop)\, Dhaka\, 1229\, Bangladesh
CATEGORIES:Journal Talk
ATTACH;FMTTYPE=image/webp:https://cassa.site/wp-content/uploads/2025/06/journal-talk.webp
ORGANIZER;CN="CASSA%2C Independent University%2C Bangladesh":MAILTO:cassa@iub.edu.bd
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BEGIN:VEVENT
DTSTART;TZID=UTC:20260602T133000
DTEND;TZID=UTC:20260602T141000
DTSTAMP:20260604T071631
CREATED:20260601T082846Z
LAST-MODIFIED:20260601T083703Z
UID:9719-1780407000-1780409400@cassa.site
SUMMARY:Journal Talk 20: Rose et al. (2019)
DESCRIPTION:Think Global\, Act Local: The Influence of Environment Age and Host Mass on Type Ia Supernova Light Curves. \nAbstract: \nThe reliability of Type Ia Supernovae (SNe Ia) may be limited by the imprint of their galactic origins. To investigate the connection between supernovae and their host characteristics\, we developed an improved method to estimate the stellar population age of the host as well as the local environment around the site of the supernova. We use a Bayesian method to estimate the star formation history and mass weighted age of a supernova’s environment by matching observed spectral energy distributions to a synthesized stellar population. Applying this age estimator to both the photometrically and spectroscopically classified Sloan Digital Sky Survey II supernovae (N = 103)\, we find a 0.114 ± 0.039 mag “step” in the average Hubble residual at a stellar age of ∼8 Gyr; it is nearly twice the size of the currently popular mass step. We then apply a principal component analysis on the SALT2 parameters\, host stellar mass\, and local environment age. We find that a new parameter\, PC1\, consisting of a linear combination of stretch\, host stellar mass\, and local age\, shows a very significant (4.7σ) correlation with Hubble residuals. There is a much broader range of PC1 values found in the Hubble flow sample when compared with the Cepheid calibration galaxies. These samples have mildly statistically different average PC1 values\, at ∼2.5σ\, resulting in at most a 1.3% reduction in the evaluation of H0. Despite accounting for the highly significant trend in SN Ia Hubble residuals\, there remains a 9% discrepancy between the most recent precision estimates of H0 using SN Ia and the CMB. \nDOI: https://doi.org/10.3847/1538-4357/ab0704 \nPresenter: Deba Priyo Guha (Postbac Research Assistant at CASSA; M.Sc. (Ongoing) on Theoretical Physics\, University of Dhaka) \n\nTo get notified\, subscribe using the Google Form: \nhttps://forms.gle/fikhmc7Y2whjJWKK9
URL:https://cassa.site/event/jtalk-20/
LOCATION:CASSA\, IUB Main Building Rooftop\, Plot 16\, Aftabuddin Ahmed Road\, Block B\, Bashundhara RA (Main Building Rooftop)\, Dhaka\, 1229\, Bangladesh
CATEGORIES:Journal Talk
ATTACH;FMTTYPE=image/webp:https://cassa.site/wp-content/uploads/2025/06/journal-talk.webp
ORGANIZER;CN="CASSA%2C Independent University%2C Bangladesh":MAILTO:cassa@iub.edu.bd
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