Astronomers discover giant new galaxy at rest

Astronomers report the discovery of a new, massive, quiet galaxy with a high redshift. The galaxy, COSMOS-1047519, was discovered with the Keck I telescope. The discovery is detailed in a paper published August 29 on the arXiv preprint server. Giant galaxies that have ceased to form stars (known as dormant large galaxies) may be the ancestors of giant elliptical galaxies. Because these objects form stars earlier and gather their stellar masses more quickly, they could play a key role in improving our understanding of galactic evolution. To date, only very few stationary galaxies with high redshifts (greater than 4.0) have been detected by spectroscopy. The discovery of new galaxies of this kind is of great importance to astronomers, as these objects could advance our understanding of the early universe. Today, a team of astronomers led by Takumi Kakimoto of the University of Advanced Study in Japan confirmed the detection of another massive resting galaxy, with a redshift of 4.53 . This discovery was made using a Keck/MOSFIRE spectrometer.

“We present spectroscopic confirmation of a stationary giant galaxy at z = 4.53 based on the Keck/MOSFIRE observations. We confirm very high stellar masses and very low star formation rates through through extensive SED [spectral energy distribution] tuning using photometry.” and spectroscopy,” the researchers wrote in the paper. Observations show that COSMOS-1047519 has a mass of about 60 billion solar masses and a star formation rate (SFR) of just 10 solar masses per year. The galaxy’s stellar age is estimated to be 180 million years. Astronomers point out that the estimated SFR undershoots the main star formation sequence by more than 1 dex at a redshift of 4.5. The star formation history of COSMOS-1047519 inferred from SED fits shows that the galaxy experienced a stellar explosion at redshift 5.0, followed by a rapid extinction around about 100 million years old. The result thus makes COSMOS-1047519 one of the youngest dormant galaxies with a redshift greater than 3.0. The results also indicate that COSMOS-1047519 is likely an extinct galaxy.

Trying to figure out the physical processes responsible for preventing star formation in COSMOS-1047519, the paper’s authors propose the most plausible hypothesis.

Source: arXiv (2023). DOI: 10.48550/arxiv.2308.15011