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#author("2025-07-09T07:49:35+00:00","default:wwwadm","wwwadm") #author("2025-07-09T15:24:01+00:00","default:wwwadm","wwwadm") [[IoA_Seminar]] #contents * 講演リスト [#g8648f7a] ** No. 430: July 24, 2025 (Thu) 15:30-16:30 [#dad05fe7] *** Place: Lecture Room, Institute of Astronomy, University of Tokyo / Zoom (hybrid) [#va7fc746] *** Speaker: Keiichi Ohnaka (Universidad Andrés Bello) [#d2a6b465] *** Title: TBD [#kf065e92] *** Title: Milliarcsecond-resolution near-infrared interferometric imaging of the rapidly changing red supergiant WOH G64 in the Large Magellanic Cloud [#kf065e92] Language: English Abstract: TBD Abstract: Intense mass loss at the red supergiant phase is crucial for better understanding the evolution of massive stars, particularly given that very early-phase spectra of supernovae (SNe) suggest significant increases in mass loss just before the SN explosion. WOH G64 is a rare, heavily dust-enshrouded red supergiant in the Large Magellanic Cloud (LMC) -- the brightest in the mid-IR in the LMC. We present milliarcsecond-resolution near-IR (2.0--2.45 micron) interferometric imaging of WOH G64 with the GRAVITY instrument at ESO's Very Large Telescope Interferometer (VLTI) -- the first close-up image of an individual star outside the Milky Way. The observed image reveals an elliptical ring-like structure and more compact, elongated inner emission with a size of ~4 x 2 mas. This elongated emission can be interpreted as a bipolar outflow or alternatively as a circumstellar envelope elongated due to a putative companion. Furthermore, based on our visible and near-IR photometric monitoring with the Rapid Eye Mount Telescope at La Silla since 2023 and the archival data, we found that a significant increase in the circumstellar dust should have started at some point between 2006 and 2016, perhaps due to episodic dust formation. Interestingly, another recent study reveals that the central star evolved from a red supergiant (3200 K) to a yellow hypergiant (4700 K) in 2014 within a year without an outburst or eruptive event. We will discuss ongoing and future observations to understand this unique object that provides a rare opportunity to witness the evolution of a massive star in real time and study the physics of the extreme mass loss. ** No. 429: April 17, 2025 (Thu) 15:30-16:30 [#dad05fe7] *** Place: Lecture Room, Institute of Astronomy, University of Tokyo / Zoom (hybrid) [#va7fc746] *** Speaker: Eduardo Ibar (Universidad de Valparaíso) [#d2a6b465] *** Title: The properties of emitting line galaxies discovered by the JWST Emission Line Survey (JELS) [#kf065e92] Language: English Abstract: Recombination lines are some of the best star-formation indicators in the nearby Universe. Previous surveys have mapped the evolution of H-alpha emitters out to the peak star-formation epoch at z~2. Beyond this redshift, samples of star-forming galaxies and estimates of the cosmic star-formation rate density are almost ubiquitously based on rest-frame UV. We exploit the JWST NIRCam's narrow-band filters to observe a 65 sq. arcmin in the well-studied COSMOS field, to characterise different emitting-line galaxy populations. Using difference imaging between the closely-spaced narrow and broad band filters, we find line emitters over different redshift slices, including Pa-alpha at z~1-5, Paschen-beta at z~2.6, , H-alpha at z~2.3 & 6.1, and [OIII] at z~8.1. JELS provides the first critical test for producing a clean, emission-line selected sample of galaxies into the Epoch of Reionization. Using JWST's remarkable angular resolution we measure the ionised gas structures of these galaxies at sub-kpc resolution and determine how the relationship between UV and ionised gas structures varies with host galaxy properties. Special emphasis is given to the exploration of the Paschen emitters, which provide an unobscured view at the peak of the cosmic star-formation rate density. ---------------------------------------------------------------
