CATA Associate Researcher to lead two ALMA projects

Manuel Aravena was awarded two ALMA Large Programs, where he will participate as Co-Principal Investigator of the PHOENIX and HIDING in the HUDF projects.

Manuel Aravena, Associate Researcher at the Center for Astrophysics and Related Technologies (CATA) and professor at Diego Portales University, was selected as co-Principal Investigator for two ambitious large-scale observation programs using the ALMA radio telescope: PHOENIX and HIDING in the HUDF. Both seek to answer key questions about the formation and evolution of galaxies, from the cosmic dawn to the era of greatest stellar activity in the Universe.

PHOENIX

PHOENIX is a program to study the earliest and most distant galaxies discovered to date (redshifts z=8-14), in which CATA researchers Rodrigo Herrera-Camus (UdeC) and Jorge González (PUC) are also participating.

The program seeks to open an unprecedented window onto the birth of the first galaxies, seeking to answer three fundamental questions: How much star formation is hidden by dust? When and how does dust appear in the early Universe? And what are the physical conditions of the gas that fuels this growth?

Based on these questions, we want to know how much star formation is hidden by dust, in order to obtain the first reliable “total count” of stellar activity in these very young galaxies. We are also interested in discovering when and how dust appears in the Universe: whether it is produced by exploding stars (supernovae) or whether dust grains grow very quickly within the gas. And finally, we want to know the properties of their gas, measuring density, temperature, and composition with ALMA and JWST together,” says Manuel Aravena.

PHOENIX will observe a representative sample of around 15 very distant galaxies, when the universe was between 300 and 650 million years old (just 2–5% of its current age). “The goal is to move from isolated cases to solid conclusions, and to look for gas movements, possible winds, and extended emission by stacking weak signals,” adds the researcher, who is also a member of the Millennium Nucleus MINGAL.

As it is a large-scale program that has only recently been awarded, PHOENIX does not yet have any results of its own. However, Aravena highlights what is new in the field. “ALMA has already reached the z>>10 front with detections of ionized oxygen in some galaxies discovered by JWST, but the samples are still small. PHOENIX seeks to multiply them by four and deliver a reference dataset for this early era,” he reveals.

HIDING in the HUDF

The second project, in which Jorge González (PUC) is also co-principal investigator, will focus on the Hubble Ultra Deep Field (HUDF), the region of the sky most studied by space and ground-based telescopes. This work seeks to obtain high-resolution images of galaxies in the “cosmic noon” in this area.

What is the “cosmic noon”? In the words of the CATA researcher, it is described as “the era of the Universe when galaxies were forming stars at the highest rate, about 10–11 billion years ago (redshift z≈1–3)”.

The HUDF already contains detailed maps of stars and star-forming regions, but we have yet to see the same level of detail for cold gas and dust, which are the “fuel” that allows new stars to form.

“HIDING will obtain very high-resolution images from ALMA. With that sharpness, we will be able to better separate the effect of dust from the aging of stars, measure where stars are actually forming per unit area, and trace the shape and size of gas and dust within each galaxy,” explains Aravena.

Although previous ALMA observations have been made in this region, none combine the sensitivity and resolution that HIDING will provide. “From space, the JWST has already given us incredible maps of stars and star-forming regions, which shows that the missing piece of the puzzle is cold dust and gas at the same resolution,” adds the CATA researcher.

Thus, with the new time at ALMA, the data will provide “HD maps” of fuel in dozens of galaxies typical of the cosmic noon, resolving neighborhood-scale structures within each galaxy. “We will learn about the sizes and shapes of gas and dust, whether they are spread out or concentrated in the center, and how they relate to the areas where stars are born. In other words, we will see the fuel of galaxies with the same clarity with which we already see their stars. That closes the circle and tells us how galaxies grew during the most intense period of the universe,” concludes the UDP academic.