A consistency test for determining whether ultracompact dwarf galaxies could be the remnant nuclei of threshed galaxies

Graham, Alister W.

doi:10.1093/mnras/stz3547

Cited by 25 publications

(21 citation statements)

References 192 publications

(218 reference statements)

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“…(v) Our accurate stellar-mass model yields improved constraints on the NSC, with a total stellar mass M NSC approximately 10 times smaller than that derived purely photometrically by Pechetti et al (2020), thus making our new M BH and M NSC consistent with the recent M BH -M NSC scaling relation of Graham (2020).…”

Section: O N C L U S I O N Ssupporting

confidence: 57%

“…Graham (2020) recently discussed a new correlation between M BH and M NSC in low-mass galaxies and UCDs, that combines the M NSC -M bulge and M BH -M bulge (or equivalently M NSC -σ and M BH -σ ) correlations (e.g. Scott, Graham & Schombert 2013; Graham 2016; Capuzzo-Dolcetta & Tosta e Melo 2017; Davis, Graham & Cameron 2019b; Sahu, Graham & Davis 2019a,b): log M NSC M = (0.38 ± 0.06) log M BH 10 7.89 M + (7.70 ± 0.20) .…”

mentioning

confidence: 99%

“…Figure 8 Graham's (2020). M BH -M NSC scaling relation (red solid line) and its 1σ uncertainties (red dotted lines).…”

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confidence: 99%

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The MBHBM⋆ Project – II. Molecular gas kinematics in the lenticular galaxy NGC 3593 reveal a supermassive black hole

Nguyen

Bureau

Thater

et al. 2021

Monthly Notices of the Royal Astronomical Society

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As part of the Measuring Black Holes in below Milky Way-mass (M⋆) galaxies (MBHBM⋆) Project, we present a dynamical measurement of the supermassive black hole (SMBH) mass in the nearby lenticular galaxy NGC 3593, using cold molecular gas 12CO(2-1) emission observed at an angular resolution of ≈0${_{.}^{\prime\prime}}$3 (≈10 pc) with the Atacama Large Millimeter/submillimeter Array (ALMA). Our ALMA observations reveal a circumnuclear molecular gas disc (CND) elongated along the galaxy major axis and rotating around the SMBH. This CND has a relatively low-velocity dispersion (≲10 km s−1) and is morphologically complex, with clumps having higher integrated intensities and velocity dispersions (≲25 km s−1). These clumps are distributed along the ridges of a two-arm/bi-symmetric spiral pattern surrounded by a larger ring-like structure (radius r ≈ 10 arcsec or ≈350 pc). This pattern likely plays an important role to bridge the molecular gas reservoirs in the CND and beyond (10 ≲ r ≲ 35 arcsec or 350 pc ≲ r ≲ 1.2 kpc). Using dynamical modelling, the molecular gas kinematics allow us to infer an SMBH mass $M_{\rm BH}=2.40_{-1.05}^{+1.87}\times 10^6$ M⊙ (only statistical uncertainties at the 3σ level). We also detect a massive core of cold molecular gas (CMC) of mass MCMC = (5.4 ± 1.2) × 106 M⊙ and effective (half-mass) radius rCMC,e = 11.2 ± 2.8 pc, co-spatial with a nuclear star cluster (NSC) of mass MNSC = (1.67 ± 0.48) × 107 M⊙ and effective radius rNSC,e = 5.0 ± 1.0 pc (or 0${_{.}^{\prime\prime}}$15 ± 0${_{.}^{\prime\prime}}$03). The mass profiles of the CMC and NSC are well described by Sérsic functions with indices 1−1.4. Our MBH and MNSC estimates for NGC 3593 agree well with the recently compiled MBH–MNSC scaling relation. Although the MNSC uncertainty is twice the inferred MBH, the rapid central rise of the rotation velocities of the CND (as the radius decreases) clearly suggests an SMBH. Indeed, our dynamical models show that even if MNSC is at the upper end of its allowed range, the evidence for a BH does not vanish, but remains with a lower limit of MBH > 3 × 105 M⊙.

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Section: O N C L U S I O N Ssupporting

confidence: 57%

mentioning

confidence: 99%

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The MBHBM⋆ Project – II. Molecular gas kinematics in the lenticular galaxy NGC 3593 reveal a supermassive black hole

Nguyen

Bureau

Thater

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…An earlier stage of such shredding, of an infalling dwarf galaxy, has been reported in a galaxy at a redshift z = 0.145 by Forbes et al (2003). See also UGC 10214 (Vorontsov-Vel'Yaminov 1959;Miskol-czi et al 2011), NGC 7714 (Soria & Motch 2004), and M32 giving itself to M31 (Arp 1964;Graham 2002;Gordon et al 2006). Various stages of the interaction process are evident in the catalog of Vorontsov-Velyaminov (1977), and the scenario in which a galaxy is threshed and reduced to its dense core has been developed by (Bekki & Freeman 2003).…”

Section: Discussionmentioning

confidence: 92%

Potential Black Hole Seeding of the Spiral Galaxy NGC 4424 via an Infalling Star Cluster

Graham,

Soria,

Ciambur

et al. 2021

Preprint

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Galaxies can grow through their mutual gravitational attraction and subsequent union. While orbiting a regular high-surface-brightness galaxy, the body of a low-mass galaxy can be stripped away. However, the stellar heart of the infalling galaxy, if represented by a tightly bound nuclear star cluster, is more resilient. From archival Hubble Space Telescope images, we have discovered a red, tidallystretched star cluster positioned ∼5 (∼400 pc in projection) from, and pointing toward the center of, the post-merger spiral galaxy NGC 4424. The star cluster, which we refer to as 'Nikhuli', has a near-infrared luminosity of (6.88 ± 1.85) × 10 6 L ,F 160W and likely represents the nucleus of a captured/wedded galaxy. Moreover, from our Chandra X-ray Observatory image, Nikhuli is seen to contain a high-energy X-ray point source, with L 0.5−8 keV = 6.31 +7.50 −3.77 × 10 38 erg s −1 (90% confidence). We argue that this is more likely to be an active massive black hole than an X-ray binary. Lacking an outward-pointing comet-like appearance, the stellar structure of Nikhuli favors infall rather than the ejection from a gravitational-wave recoil event. A minor merger with a low-mass early-type galaxy may have sown a massive black hole, aided an X-shaped pseudobulge, and be sewing a small bulge. The stellar mass and the velocity dispersion of NGC 4424 predict a central black hole of (0.6-1.0)×10 5 M , similar to the expected intermediate-mass black hole in Nikhuli, and suggestive of a black hole supply mechanism for bulgeless late-type galaxies. We may potentially be witnessing black hole seeding by capture and sinking, with a nuclear star cluster the delivery vehicle.

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“…We can test the plausibility of the stripped nuclei hypothesis by comparing the stellar mass of the clusters to a predicted NSC mass inferred from scaling relationships between black holes, NSCs, and their host galaxies similar to what was done in Graham (2020). If the luminous GCs with elevated M/L V are the remnant stripped nuclei of galaxies, we expect their stellar mass to be comparable with the NSC mass of their progenitor galaxy (Pfeffer & Baumgardt 2013).…”

Section: A Consistency Check For the Tidal Stripping Formation Scenariomentioning

confidence: 96%

A population of luminous globular clusters and stripped nuclei with elevated mass to light ratios around NGC 5128

Dumont,

Seth,

Strader

et al. 2021

Preprint

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The dense central regions of tidally disrupted galaxies can survive as ultra-compact dwarfs (UCDs) that hide among the luminous globular clusters (GCs) in the halo of massive galaxies. An exciting confirmation of this model is the detection of overmassive black holes in the centers of some UCDs, which also lead to elevated dynamical mass-to-light ratios (M/L dyn ). Here we present new high-resolution spectroscopic observations of 321 luminous GC candidates in the massive galaxy NGC 5128/Centaurus A. Using these data we confirm 27 new luminous GCs, and measure velocity dispersions for 57 luminous GCs (with g-band luminosities between 2.5 × 10 5 and 2.5 × 10 7 L ), of which 48 have no previous reliable measurements. Combining these data with size measurements from Gaia, we determine the M/L dyn for all 57 luminous GCs. We see a clear bimodality in the M/L dyn distribution, with a population of normal GCs with mean M/L dyn = 1.51 ± 0.31, and a second population of ∼20 GCs with elevated mean M/L dyn = 2.68 ± 0.22. We show that black holes with masses ∼ 4-18% of the luminous GCs can explain the elevated mass-to-light ratios. Hence, it is plausible that the NGC 5128 sources with elevated M/L dyn are mostly stripped galaxy nuclei that contain massive central black holes, though future high spatial resolution observations are necessary to confirm this hypothesis for individual sources. We also present a detailed discussion of an extreme outlier, VHH81-01, one of the largest and most massive GC in NGC 5128, making it an exceptionally strong candidate to be a tidally stripped nucleus.

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A consistency test for determining whether ultracompact dwarf galaxies could be the remnant nuclei of threshed galaxies

Cited by 25 publications

References 192 publications

The MBHBM⋆ Project – II. Molecular gas kinematics in the lenticular galaxy NGC 3593 reveal a supermassive black hole

The MBHBM⋆ Project – II. Molecular gas kinematics in the lenticular galaxy NGC 3593 reveal a supermassive black hole

Potential Black Hole Seeding of the Spiral Galaxy NGC 4424 via an Infalling Star Cluster

A population of luminous globular clusters and stripped nuclei with elevated mass to light ratios around NGC 5128

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