Evidence of Runaway Gas Cooling in the Absence of Supermassive Black Hole Feedback at the Epoch of Cluster Formation

Abstract

Cosmological simulations, as well as mounting evidence from observations, have shown that supermassive black holes play a fundamental role in regulating the formation of stars throughout cosmic time. This has been clearly demonstrated in the case of galaxy clusters in which powerful feedback from the central black hole is preventing the hot intracluster gas from cooling catastrophically, thus reducing the expected star formation rates by orders of magnitude. These conclusions, however, have been almost entirely based on nearby clusters. Based on new Chandra X-ray observations, we present the first observational evidence for massive, runaway cooling occurring in the absence of supermassive black hole feedback in the high-redshift galaxy cluster SpARCS104922.6+564032.5 (z=1.709). The hot intracluster gas appears to be fueling a massive burst of star formation (≈900 M e yr −1) that is offset by dozens of kpc from the central galaxy. The burst is co-spatial with the coolest intracluster gas but not associated with any galaxy in the cluster. In less than 100 million years, such runaway cooling can form the same amount of stars as in the Milky Way. Therefore, intracluster stars are not only produced by tidal stripping and the disruption of cluster galaxies, but can also be produced by runaway cooling of hot intracluster gas at early times. Overall, these observations show the dramatic impact when supermassive black hole feedback fails to operate in clusters. They indicate that in the highest overdensities, such as clusters and protoclusters, runaway cooling may be a new and important mechanism for fueling massive bursts of star formation in the early universe. Unified Astronomy Thesaurus concepts: High-redshift galaxy clusters (2007); Supermassive black holes (1663); Cooling flows (2028); Intracluster medium (858); X-ray observatories (1819)

An Assessment of the In-Situ Growth of the Intracluster Light in the High Redshift Galaxy Cluster SpARCS1049+56

“…Finally, we add to this previously published infrared data that target the ongoing star formation in the core of the cluster. Using these three legs we present a census of the past, future and present star formation in the central regions of SpARCS1049 and, we posit, in agreement with Hlavacek-Larrondo et al (2020), the in-situ build-up of the ICL.…”

“…This work presented both the cluster itself (through the spectroscopic detection of 27 cluster member galaxies) as well as the high star forming core (860±130 M yr −1 ) which, at the time, was associated with the BCG. The cluster has a lensing mass of 4×10 14 M (Finner et al 2020) and has been detected in the X-ray by Hlavacek-Larrondo et al (2020). The latter work, as mentioned in the previous section, furthermore argued that SpARCS1049 contains a cool core and that the intense star formation is fed by the large scale, runaway cooling of intracluster gas, which has been allowed to cool in the cluster core due to the lack of feedback from the central AGN (Trudeau et al 2019).…”

“…Some observational studies, however, have claimed that significant amounts of in-situ star formation occurs within the BCG McDonald et al 2016), while some simulations (Puchwein et al 2010) indicate that a significant fraction of the ICL could possibly form in-situ as well. Indeed, the work of Hlavacek-Larrondo et al (2020) surmised that the growth of the ICL could be fed by runaway cooling flows, in the absence of AGN heating. The relative importance of in-situ (i.e.…”

The H α star formation main sequence in cluster and field galaxies at z ∼ 1.6

“…The other two SpARCS high-redshift clusters have also appeared in several important studies independently of the z ∼ 1.6 subsample. SpARCS-1049 is a very massive cluster for its redshift (Finner et al 2020) which has been the subject of extensive studies of its peculiar central starburst, suspected to be fed by a cooling flow or multiple wet mergers (Webb et al 2015(Webb et al , 2017Bonaventura et al 2017;Trudeau et al 2019;Hlavacek-Larrondo et al 2020). SpARCS-0335, as part of the GOGREEN survey, has been included in almost all of the GOGREEN early science papers including Old et al (2020), van der Burg et al (2020), Chan et al (in press), and Webb et al (2020).…”

Hypersphere World-Universe Model: Basic Ideas

“…Julie Hlavacek-Larrondo, et al present the first observational evidence for massive, runaway cooling occurring in the absence of supermassive BH feedback in the high-redshift galaxy cluster SpARCS104922.6 + 564032.5. Their observations show the dramatic impact when supermassive BH feedback fails to operate in clusters [30]. Black Hole fails to do its job [31].…”