Seminars and Colloquia at ESO Santiago

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Streamers and accretion shocks are predicted by theoretical models, however, only few protostars show evidence of these physical processes at the disk-envelope interface. Infalling streamers can replenish the disk with fresh material from the envelope and accretion shocks are able to sublimate molecules to the gas-phase that, otherwise, will remain looked into dust grains.

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We present You Only Stack Once (YOSO), a new AI-based approach for detecting moving objects in astronomical images. Unlike traditional shift-and-stack methods, YOSO skips velocity assumptions and directly stacks time-series images using a Gaussian Motion Filter (GMoF). This pixel-level filter convolves each pixel’s temporal light curve with the expected motion profile of a moving object, thereby amplifying time-coherent signals while suppressing noise and the stationary background. The stacked output is then analyzed with a deep learning model trained to recognize the distinct profiles of moving object trails. YOSO enables fast, motion-unbiased, and highly sensitive detections down to signal-to-noise ratios of 0.5:1. While primarily designed for Trans-Neptunian and Near-Earth Object searches, the method also shows strong potential for extending to exoplanet detection in high-contrast imaging.

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The weakness of the hyperfine 21cm line, the main tracer of the atomic gas content of galaxies, has meant that we know little about the HI mass of high-redshift galaxies and its evolution. This has long been one of the biggest lacunae in our understanding of galaxy evolution. ``Stacking'' of the 21cm emission signals from a large sample of high-redshift galaxies, with known optical positions and redshifs and observed simultaneously with a radio interferometer, can allow one to determine the atomic gas properties of the galaxy population. The advent of new or upgraded radio interferometers, with wideband spectral capabilities and modern correlators, has recently yielded dramatic progress in this field. In this talk, I will describe the state of the art in such 21cm stacking experiments from deep studies with the Giant Metrewave Radio Telescope that have yielded the first measurements of the atomic gas properties of star-forming galaxies during the era of cosmic noon.

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Gamma-ray bursts fascinate astronomers both for their astounding power and for their effectiveness as cosmological probes. Spectroscopy of their bright optical counterparts allows to dissect the interstellar and circumgalactic medium of high-redshift star-forming galaxies, testing their gas, metals, dust, and molecular content. At the same time, also thanks to a new suite of instruments, we have been discovering a richer diversity of progenitor systems - with the two main players being collapsing massive stars and binary compact object mergers. I will highlight the recent progress and surprises in the field achieved via the "Stargate" program at the VLT.

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