Masses and scaling relations for nuclear star clusters, and their co-existence with central black holes

By I. Georgiev, T. Böker, N. Leigh, N. Lutzgendorf, N. Neumayer. 2016

133 citations recorded by the source corpus.

Galactic nuclei typically host either a Nuclear Star Cluster (NSC, prevalent in galaxies with masses $\lesssim 10^{10}M_\odot$) or a Massive Black Hole (MBH, common in galaxies with masses $\gtrsim 10^{12}M_\odot$). In the intermediate mass range, some nuclei host both a NSC and a MBH. In this paper, we explore scaling relations between NSC mass (${\cal M}_{\rm NSC}$) and host galaxy total stellar mass (${\cal M}_{\star,\rm gal}$) using a large sample of NSCs in late- and early-type galaxies, including a number of NSCs harboring a MBH. Such scaling relations reflect the underlying physical mechanisms driving the formation and (co)evolution of these central massive objects. We find $\sim\!1.5\sigma$ significant differences between NSCs in late- and early-type galaxies in the slopes and offsets of the relations $r_{\rm eff,NSC}$--${\cal M}_{\rm NSC}$, $r_{\rm eff, NSC}$--${\cal M}_{\star,\rm gal}$ and ${\cal M}_{\rm NSC}$--${\cal M}_{\star,\rm gal}$, in the sense that $i)$ NSCs in late-types are more compact at fixed ${\cal M}_{\rm NSC}$ and ${\cal M}_{\star,\rm gal}$; and $ii)$ the ${\cal M}_{\rm NSC}$--${\cal M}_{\star,\rm gal}$ relation is shallower for NSCs in late-types than in early-types, similar to the ${\cal M}_{\rm BH}$--${\cal M}_{\star,\rm bulge}$ relation. We discuss these results in the context of the (possibly ongoing) evolution of NSCs, depending on host galaxy type. For NSCs with a MBH, we illustrate the possible influence of a MBH on its host NSC, by considering the ratio between the radius of the MBH sphere of influence and $r_{\rm eff, NSC}$. NSCs harbouring a sufficiently massive black hole are likely to exhibit surface brightness profile deviating from a typical King profile.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f029fd3b5a3ace6b79d4ecf11cbe3be3e458b752

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In Astronomy and Astrophysics

Citations in the corpus

Greatly Enhanced Merger Rates of Compact-object Binaries in Non-spherical Nuclear Star Clusters (2017, background): “Most nearby galaxies contain a compact stellar cluster residing at their kinematical and photometric center (e.g., Neumayer et al. 2011; Turner et al. 2012; den Brok et al. 2014; Georgiev & Böker 2014; Georgiev et al. 2016).”
Formation and Evolution of Compact-object Binaries in AGN Disks (2019, background): “78Bulge 1 SMBH 8 0.228 ( ) ⎛ ⎝⎜ ⎞ ⎠⎟ The radius of the nuclear star clusters in late-type galaxies is expressed as (Georgiev et al. 2016) = ´ r M M 3.23 pc 3.6 10 .”
Assisted inspirals of stellar mass black holes embedded in AGN discs: solving the ‘final au problem’ (2016, background): “These SMBHs are indeed surrounded by dense nuclear star clusters (NSCs; Georgiev & Böker 2014) which can in many cases dominate the mass of the central parsecs (Georgiev et al. 2016).”
Stellar Dynamics and Stellar Phenomena Near a Massive Black Hole (2017, background): “1010 M ), while the nucleus of very massive galaxies (& 1012 M ) is completely dominated by the MBH. MBHs and nuclear stellar clusters often coexist in galaxies in the intermediate mass range (Georgiev et al. 2016).”
Black hole growth through hierarchical black hole mergers in dense star clusters: implications for gravitational wave detections (2018, methodology): “We compute Γm(Mcl, rh) for the NNC = 151 clusters in the observational sample of Georgiev et al. (2016) with a well determined mass and effective radius (see Fig.”
Selection bias in dynamically measured supermassive black hole samples: its consequences and the quest for the most fundamental relation (2016, background): “…examine whether bulge or total luminosity is a better predictor ofMbh (e.g., Marconi & Hunt 2003; Häring & Rix 2004; Kormendy & Bender 2011; Läsker et al. 2014), or consider the connection to nuclear star clusters only in terms of stellar mass (e.g., Antonini et al. 2015; Georgiev et al. 2016).”
Nuclear star clusters (2009, background): “A factor of two difference was previously noted by Georgiev et al. (2016), but the data shown here suggests this offset may not extend down to the lowest mass NSCs. 3.”
MERGING BLACK HOLE BINARIES IN GALACTIC NUCLEI: IMPLICATIONS FOR ADVANCED-LIGO DETECTIONS (2016, methodology): “The cluster radii and masses were taken from the sample of late-type galaxies of Georgiev et al. (2016).”