NASA’s Legacy ExtraGalactic UV Survey Data Released

Daniela Calzetti
Daniela Calzetti

NASA today announced the release of the most comprehensive ultraviolet (UV) survey of nearby galaxies to date, performed with the Hubble Space Telescope. The data were obtained as part of the Hubble Treasury project known as Legacy ExtraGalactic Ultraviolet Survey (LEGUS).

Astronomer Daniela Calzetti is principal investigator for the project. She says about 55 astronomers from more that 30 institutions on four continents make up the LEGUS team. Calzetti and colleagues are releasing the stellar and star cluster catalogs for the 50 LEGUS galaxies, which contain measurements for about 39 million stars and over 8,000 star clusters, or large groupings of stars.

The measurements include light from the UV to the red for all sources, and these will be an important resource for the astronomical community. The UV measurements, released in these catalogs for the first time, trace the youngest and hottest stellar populations, thus enabling astronomers to investigate locations of recent star formation in the galaxies, she explains. The catalogs enable unique science, including the investigation of the evolution of stars and star clusters across different environments.

A specialist in how galaxies are formed, Calzetti is internationally known for “Calzetti’s Law,” a tool she developed in the mid-1990s that, among other things, allows astronomers to estimate how much information they are missing due to dust obscuring probes of very distant galaxies. She noted recently that it has not been refuted and it may be a matter of time before another astronomer comes up with an idea to replace it, but at present it is still the accepted way to deal with dust contamination in galaxies.

Calzetti’s research interest is in exploring galaxies and how their shape is linked to the stars they form. For example, she points out, the question is still “highly debated” as to why the youngest stars congregate in spiral arms or in rings around the centers of galaxies, and how these structures evolve with time as the galaxy ages.