A galaxy merger observed that generated a quenching galaxy with a tidal tail

Combined view of the galaxy SDSS J1448+1010 seen by ALMA and Hubble (Image ALMA (ESO/NAOJ/NRAO), J. Spilker et al (Texas A&M), S. Dagnello (NRAO/AUI/NSF))
Combined view of the galaxy SDSS J1448+1010 seen by ALMA and Hubble (Image ALMA (ESO/NAOJ/NRAO), J. Spilker et al (Texas A&M), S. Dagnello (NRAO/AUI/NSF))

An article published in “The Astrophysical Journal Letters” reports a study on the galaxy SDSS J1448+1010. A team of researchers used the ALMA radio telescope, the Hubble Space Telescope, and other instruments to examine it and found that no more stars are forming inside it. After analyzing the observations collected, they concluded that this is due to the fact that SDSS J1448+1010 is the result of a galaxy merger in which a large part of the hydrogen that forms the stars was ejected as a result of the gravitational effects suffered in the course of that event. In fact, the researchers discovered what was defined as a tidal tail formed by the ejected materials, which also include stars.

Galaxies can have periods of intense star formation and can become quenching at some point in their life. A study of 13 galaxies that became quenching after a period of intense star formation included SDSS J1448+1010, whose full name is SDSS J144845.91+101010.5, which showed an unusual situation. The various mechanisms that make galaxies quenching are not yet well understood, so finding a galaxy of this type that didn’t consume all its gas in star formation was a cause of interest for a team of researchers who conducted a follow-up study.

Galaxy mergers are a normal phenomenon in the universe, and astronomers found many cases of galaxies at various stages of this process. During a merger, gas clouds in the two original galaxies can undergo compression due to gravitational dynamics, triggering a new phase of star formation. The study of the galaxy SDSS J1448+1010 showed a completely different result that gave an opposite outcome.

The merger that spawned the SDSS J1448+1010 galaxy occurred when the universe was about half its current age and from Earth we see that process nearing its completion. During a merger, the original galaxies exert gravitational forces that depend on their relative position and the distribution of masses within them. In this case, the result was that about half of the gas needed to form new stars was pushed out of the new galaxy forming what was defined as a tidal tail along with various stars that ended up the same way.

Now the galaxy SDSS J1448+1010 is quenching due to the scarcity of gas useful to form new stars. This is a surprising discovery because it’s the first time that astronomers discovered such an effect of a galaxy merger. This doesn’t mean that it’s a unique case and now the researchers intend to study other cases of mergers to see if they had similar effects. These are processes that continue for many millions of years with remarkable effects on the future of the galaxies in which they occur.

Artist's concept of the galaxy SDSS J1448+1010 with its tidal tail (Image ALMA (ESO/NAOJ/NRAO), S.Dagnello (NRAO/AUI/NSF))
Artist’s concept of the galaxy SDSS J1448+1010 with its tidal tail (Image ALMA (ESO/NAOJ/NRAO), S.Dagnello (NRAO/AUI/NSF))

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