Galaxy SPT 0538-50 belongs to the so-called dusty galaxies with star formation. Recently, scientists used the ALMA antenna array to get a proper look at what’s going on there.
Observations of dusty star-forming galaxies
Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers observed a dusty star-forming galaxy known as SPT 0538-50. The results of the observational campaign, presented on December 4 on the arXiv preprint server, provide more information about the structure of this galaxy.
So-called star-forming dust galaxies (SFDGs) are heavily obscured galaxies that undergo a period of intense star formation, with star formation rates that can even reach 1,000 solar masses per year. However, although many SFDGs are known, their nuclear structure, which may be important for a better understanding of the evolution of these galaxies, is still not fully understood.
Structure of the galaxy nucleus SPT 0538-50
SPT 0538-50 is a SFDG with a redshift of 2.78, with an infrared luminosity of 3.4 trillion solar luminosities. The galaxy has a stellar mass of about 33 billion solar masses and a star formation rate of 760 solar masses per year.
Recently, a team of astronomers led by Hannah Stacey of the European Southern Observatory (ESO) conducted long-term continuum observations of SPT 0538-50 with ALMA to reveal its nuclear structure.
ALMA observations showed that the central region of SPT 0538-50 has a double helical arm morphology and a potential nuclear bar. The researchers hypothesize that the nuclear bar may contribute to the flow of gas that powers the nuclear flare and the galaxy’s supermassive black hole. They added that these findings suggest that SPT 0538-50 may be dynamically cold, like local nuclear disks.
The study found that SPT 0538-50 has an effective radius of approximately 1,950 light-years, a Sersic index of 1.2 and a positional angle of 4.0. These parameters are consistent with a compact disk comparable to other known SFDGs.
High density of star formation
From the data collected, the astronomers obtained an extreme star formation rate density for the central region of SPT 0538-50, which was about 2,000 solar masses/year/kiloparsec2. Thus, this is a super-Eddington velocity compared to the Eddington limit for nearby superluminous infrared galaxies.
The authors of the paper note that a high density of gas is needed to explain such a high density of star formation rate in the central region of the studied galaxy. They added that the additional influence of secular dynamical processes is required to accumulate high gas densities within a few hundred light-years of the center of SPT 0538-50.
“These features may indicate that secular dynamical processes play a role in accumulating a high concentration of cold gas that fuels the rapid formation of a compact stellar spheroid and black hole accretion,” the scientists concluded.
Provided by phys.org
