![[PukiWiki]](image/pukiwiki.png "[PukiWiki]")
Language: English
Abstract: In this talk, I will present the Astronomy Department (DAS) at Universidad de Chile in the greater context of astronomy in Chile. DAS researchers address a large variety of topics from Solar System to Extragalactic research facilitating several opportunities for collaboration, student exchange and formation. Additionally, highlights in planetary sciences research from my group will be addressed in more detail.
Language: English
Abstract: Our team has recently commissioned the HATPI facility (www.hatpi.org) at Las Campanas Observatory in Chile. HATPI observes the entire visible sky 30 degrees above the horizon at moderately high spatial resolution, very high photometric precision, and with a fast cadence of 45 seconds. The instrument consists of 64 lenses, each equipped with a back illuminated CCD, and each lens unit capable of accurate micro-tracking. In brief, anything that happens in the night sky down to ~16th magnitude (at 45s cadence) or 18th magnitude (per night) is captured by HATPI. The scientific goal of HATPI is to observe the variable sky, while complementing LSST and TESS. In particular, the key science areas are i) transiting exoplanets and variable stars, ii) transient objects, such as gamma-ray burst afterglows iii) moving objects, such as near-earth asteroids and comets. I will summarize the exciting early science from the commissioning data of HATPI, and will eagerly await comments and suggestions.
Language: English
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.
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.
