New protocluster of massive quiescent galaxies discovered

A world workforce of astronomers reviews the invention of a brand new protocluster of huge quiescent galaxies at a redshift of roughly 4.0. That is the primary detection of a protocluster of this kind at such a excessive redshift. The discovering was detailed in a paper published Nov. 20 on the pre-print server arXiv.

Galaxy clusters harbor from a whole lot to hundreds of galaxies sure collectively by gravity. They’re essentially the most immense gravitationally sure buildings within the universe, and will function glorious laboratories for learning galaxy evolution and cosmology.

Astronomers are particularly enthusiastic about research of protoclusters of galaxies, the progenitors of clusters. Such objects, discovered at excessive redshifts (over 2.0), might present important details about the early phases of the universe.

Now, a gaggle of astronomers led by Masayuki Tanaka of the Nationwide Astronomical Observatory of Japan (NAOJ) has discovered a brand new high-redshift protocluster. By analyzing the information from the Subaru/XMM-Newton Deep Survey (SDXS), they recognized a focus of at the least 5 huge quiescent galaxies, at a redshift of three.99. The examine was complemented by information from follow-up observations with the MOSFIRE spectrograph on the Keck I telescope.

The newfound galaxies acquired designations: SXDS2_19838, SXDS2_15659, SXDS2_16609, SXDS2_19229, and SXDS2_19997. The galaxy SXDS2_19838 is essentially the most huge of them as its stellar mass and halo mass had been measured to be 113.1 billion and three.1 trillion solar masses, respectively.

The observations present that SXDS2_19838 is surrounded by 4 different galaxies, which collectively have stellar and halo plenty, of about 230 billion and eight.5 trillion solar plenty, respectively. All of the galaxies of this overdensity skilled not too long ago an episode of starburst exercise, adopted by a speedy quenching. Now, they’ve star-formation charges (SFRs) between 1.4 and 11.5 solar plenty per 12 months.

The collected information counsel that every one these 5 galaxies fashioned and quenched at comparable occasions. The authors of the paper assume that this protocluster will collapse to type the core of a large cluster. They added that the protocluster could also be a denser system than noticed, and that the member galaxies should not but in the identical halo on the time of the commentary, however additional research are wanted to substantiate it.

Summing up the outcomes, the researchers underline how distinctive their discovery is. “That is the primary discovery of a focus of quiescent galaxies at this high redshift and it serves as a singular laboratory to analyze the function of the setting at z = 4 for the primary time,” the scientists concluded.

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