A “Missing” Galaxy Immortalized by the VST (Cosmology)

The photo of the week of the European Southern Observatory is an image obtained from Chile with the Vst telescope (made by INAF) of the ultra-diffuse galaxy Udg 4. The image was acquired as part of a program for the study of structures very faint in the clusters of galaxies, Vegas, led by Enrichetta Iodice of the INAF of Naples

If you look closely at the faint and blurred center of the image opposite, you can see a “ghost” galaxy – the Udg 4, with a not-so-creepy name – captured by ESO’s Vlt Survey Telescope ( Vst ).

The acronym Udg stands for ultra-diffuse galaxy : objects as large as the Milky Way but with one hundred to one thousand times fewer stars. These galaxies are extremely faint and lack gas to form stars, which makes them look almost like a soft cosmic cloud or patch in space. Their origins remain uncertain, but astronomers speculate they may be “missing” galaxies that lost gas early in their life.

This Udg 4 image was taken as part of a study by a much larger program, the Vst Early-type Galaxy Survey (Vegas), which aims to investigate very faint structures in galaxy clusters : large groups of many galaxies bound together. by gravity. The study – led by Vegas principal investigator Enrichetta Iodice of the National Institute of Astrophysics, and published last year in Astronomy & Astrophysics  – found several ultra-diffuse galaxies in the Hydra cluster .

Several INAF astronomers from Naples, Teramo and Padua participate in the study. In the photo the young Neapolitan researchers and students of the Vegas team. From left: Marco Mirabile, Marilena Spavone, Enrichetta Iodice (principal investigator of Vegas), Rossella Ragusa, Antonio La Marca and Giuseppe D’Ago. Credits: Inaf

“Further observations are necessary to clarify their true nature”, Iodice underlines to Media Inaf . «This is part of a large-scale project that aims to detect a large number of Udg in all images of Vegas. For the new Udg sample, we aim to obtain new spectroscopic data in order to study stellar populations and their dark matter content ».

Given their fragile appearance, UDGs can be difficult to spot. However, the VST, equipped with its OmegaCam camera , provides extraordinary sensitivity to light, allowing astronomers to study such elusive objects.

Featured image: The ultra-diffuse galaxy Udg 4 seen from the Vst. Credits: Eso / Iodice et al.


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Provided by INAF

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