ABSTRACT
One of the most protracted problems in astronomy has been understanding the evolution of galaxy morphology. Much discussion has surrounded how lenticular galaxies may form a bridging ...population between elliptical and spiral galaxies. However, with recourse to a galaxy’s central black hole mass, accretion-built spiral galaxies have emerged as the bridging population between low-mass lenticular galaxies and the dusty merger-built lenticular galaxies contiguous with elliptical galaxies and ‘brightest cluster galaxies’ in the black hole/galaxy mass diagram. Spiral galaxies, including the Milky Way, appear built from gas accretion and minor mergers onto what were initially lenticular galaxies. These connections are expressed as a new morphology sequence, dubbed the ‘Triangal’, which subsumes elements of the Hubble sequence and the van den Bergh trident and reveals the bridging nature of the often overlooked ellicular galaxies. Furthermore, a quadratic black hole/galaxy mass relation is found to describe ordinary elliptical galaxies. The relation is roughly parallel to the quadratic-like relations observed for the central spheroidal component of spiral galaxies, dust-rich lenticular galaxies, and old dust-poor lenticular galaxies. The brightest cluster galaxies are offset according to expectations from an additional major merger. The findings have implications for feedback from active galactic nuclei, mapping morphology into simulations, and predicting gravitational wave signals from colliding supermassive black holes. A new galaxy speciation model is presented. It disfavours the ‘monolithic collapse’ scenario for spiral, dusty lenticular, and elliptical galaxies. It reveals substantial orbital angular momentum in the Universe’s first galaxies and unites dwarf and ordinary ‘early-type’ galaxies.
ABSTRACT Lenticular galaxies are notoriously misclassified as elliptical galaxies and, as such, a (disc inclination)-dependent correction for dust is often not applied to the magnitudes of dusty ...lenticular galaxies. This results in overly red galaxy colours, impacting their distribution in the colour–magnitude diagram. It is revealed how this has led to an underpopulation of the ‘green valley’ by hiding a ‘green mountain’ of massive dust-rich lenticular galaxies – known to be built from gas-rich major mergers – within the ‘red sequence’ of colour–(stellar mass) diagrams. Correcting for dust, a ‘green mountain’ appears at M*,gal ∼ 1011 M⊙, along with signs of an extension to lower masses producing a ‘green range’ or ‘green ridge’ on the green side of the ‘red sequence’ and ‘blue cloud.’ The ‘red sequence’ is shown to be comprised of two components: a red plateau defined by elliptical galaxies with a near-constant colour and by lower-mass dust-poor lenticular galaxies, which are mostly a primordial population but may include faded/transformed spiral galaxies. The presence of the quasi-triangular-shaped galaxy evolution sequence, previously called the ‘Triangal’, is revealed in the galaxy colour–(stellar mass) diagram. It tracks the speciation of galaxies and their associated migration through the diagram. The connection of the ‘Triangal’ to previous galaxy morphology sequences (Fork, Trident, and Comb) is also shown herein. Finally, the colour–(black hole mass) diagram is revisited, revealing how the dust correction generates a blue–green sequence for the spiral and dust-rich lenticular galaxies that is offset from a green–red sequence defined by the dust-poor lenticular and elliptical galaxies.
ABSTRACT
It has been suggested that ultracompact dwarf (UCD) galaxies are the ‘threshed’ remains of larger galaxies. Simulations have revealed that extensive tidal-stripping may pare a galaxy back to ...its tightly bound, compact nuclear star cluster. It has therefore been proposed that the two-component nature of UCD galaxies may reflect the original nuclear star cluster surrounded by the paltry remnants of its host galaxy. A simple quantitative test of this theory is devised and applied here. If the mass of the central black hole (BH) in UCD galaxies, relative to the mass of the UCD galaxies’ inner stellar component, i.e. the suspected nuclear star cluster, matches with the (black hole mass)–(nuclear star cluster mass) relation observed in other galaxies, then it would provide quantitative support for the stripped galaxy scenario. Such consistency is found for four of the five UCD galaxies reported to have a massive BH. This (black hole mass)–(nuclear star cluster mass) relation is then used to predict the central BH mass in two additional UCD galaxies, and to reveal that NGC 205 and possibly NGC 404 (which only has an upper limit to its black hole mass) also follow this scaling relation.
Using the latest sample of 48 spiral galaxies having a directly measured supermassive black hole mass, MBH, we determine how the maximum disk rotational velocity, vmax (and the implied dark matter ...halo mass, MDM), correlates with the (i) black hole mass, (ii) central velocity dispersion, 0, and (iii) spiral-arm pitch angle, φ. We find that M BH ∝ v max 10.62 1.37 ∝ M DM 4.35 0.66 , significantly steeper than previously reported, and with a total root mean square scatter (0.58 dex) similar to that about the MBH- 0 relation for spiral galaxies-in stark disagreement with claims that MBH does not correlate with disks. Moreover, this MBH-vmax relation is consistent with the unification of the Tully-Fisher relation (involving the total stellar mass, M*,tot) and the steep M BH ∝ M * , tot 3.05 0.53 relation observed in spiral galaxies. We also find that 0 ∝ v max 1.55 0.25 ∝ M DM 0.63 0.11 , consistent with past studies connecting stellar bulges (with 0 100 km s−1), dark matter halos, and a nonconstant vmax/ 0 ratio. Finally, we report that tan φ ∝ ( − 1.18 0.19 ) log v max ∝ ( − 0.48 0.09 ) log M DM , providing a novel formulation between the geometry (i.e., the logarithmic spiral-arm pitch angle) and kinematics of spiral galaxy disks. While the vmax-φ relation may facilitate distance estimations to face-on spiral galaxies through the Tully-Fisher relation and using φ as a proxy for vmax, the MDM-φ relation provides a path for determining dark matter halo masses from imaging data alone. Furthermore, based on a spiral galaxy sample size that is double the size used previously, the self-consistent relations presented here provide dramatically revised constraints for theory and simulations.
We have examined the relationship between supermassive black hole mass (M sub(BH)) and the stellar mass of the host spheroid (M sub(sph),low *) for a sample of 75 nearby galaxies. To derive the ...spheroid stellar masses we used improved Two Micron All Sky Survey Ks-band photometry from the ARCHANGEL photometry pipeline. Dividing our sample into core-Sersic and Sersic galaxies, we find that they are described by very different M sub(BH)-M sub(sph),low * relations. For core-Sersic galaxies-which are typically massive and luminous, with M sub(BH) > ~ 2 x 10 super(8) M sub(middot in circle)-we find M sub(BH) is proportional to (ProQuest: Formulae and/or non-USASCII text omitted), consistent with other literature relations. However, for the Sersic galaxies-with typically lower masses, M sub(sph),low * <, ~ 3 x 10 super(10) M sub(middot in circle)-we find M sub(BH) is proportional to (ProQuest: Formulae and/or non-USASCII text omitted), a dramatically steeper slope that differs by more than 2 standard deviations. This relation confirms that, for Sersic galaxies, M sub(BH) is not a constant fraction of M sub(sph),low *. Sersic galaxies can grow via the accretion of gas which fuels both star formation and the central black hole, as well as through merging. Their black hole grows significantly more rapidly than their host spheroid, prior to growth by dry merging events that produce core-Sersic galaxies, where the black hole and spheroid grow in lockstep. We have additionally compared our Sersic M sub(BH)-M sub(sph),low * relation with the corresponding relation for nuclear star clusters, confirming that the two classes of central massive object follow significantly different scaling relations.
ABSTRACT
We recently revealed that bulges and elliptical galaxies broadly define distinct, superlinear relations in the (black hole mass, Mbh)–(spheroid stellar mass, M*,sph) diagram or Mbh−M*,sph ...diagram, with the order-of-magnitude lower Mbh/M*,sph ratios in the elliptical galaxies due to major (disc-destroying, elliptical-building) dry mergers. Here, we present a more nuanced picture. Galaxy mergers, in which the net orbital angular momentum does not cancel, can lead to systems with a rotating disc. This situation can occur with either wet (gas-rich) mergers involving one or two spiral galaxies, e.g. NGC 5128, or dry (relatively gas-poor) collisions involving one or two lenticular galaxies, e.g. NGC 5813. The spheroid and disc masses of the progenitor galaxies and merger remnant dictate the shift in the Mbh−M*,sph and Mbh−Re,sph diagrams. We show how this explains the (previously excluded merger remnant) Sérsic S0 galaxies near the bottom of the elliptical sequence and core-Sérsic S0 galaxies at the top of the bulge sequence, neither of which are faded spiral galaxies. Different evolutionary pathways in the scaling diagrams are discussed. We also introduce two ellicular (ES) galaxy types, explore the location of brightest cluster galaxies and stripped ‘compact elliptical’ galaxies in the Mbh−M*,sph diagram, and present a new merger-built Mbh−M*,sph relation which may prove helpful for studies of nanohertz gravitational waves. This work effectively brings into the fold many systems previously considered outliers with either overly massive or undermassive black holes relative to the near-linear Mbh−M*,sph ‘red sequence’ patched together with select bulges and elliptical galaxies.
We compare the set of local galaxies having dynamically measured black holes with a large, unbiased sample of galaxies extracted from the Sloan Digital Sky Survey. We confirm earlier work showing ...that the majority of black hole hosts have significantly higher velocity dispersions σ than local galaxies of similar stellar mass. We use Monte Carlo simulations to illustrate the effect on black hole scaling relations if this bias arises from the requirement that the black hole sphere of influence must be resolved to measure black hole masses with spatially resolved kinematics. We find that this selection effect artificially increases the normalization of the M
bh–σ relation by a factor of at least ∼3; the bias for the M
bh–M
star relation is even larger. Our Monte Carlo simulations and analysis of the residuals from scaling relations both indicate that σ is more fundamental than M
star or effective radius. In particular, the M
bh–M
star relation is mostly a consequence of the M
bh–σ and σ–M
star relations, and is heavily biased by up to a factor of 50 at small masses. This helps resolve the discrepancy between dynamically based black hole–galaxy scaling relations versus those of active galaxies. Our simulations also disfavour broad distributions of black hole masses at fixed σ. Correcting for this bias suggests that the calibration factor used to estimate black hole masses in active galaxies should be reduced to values of f
vir ∼ 1. Black hole mass densities should also be proportionally smaller, perhaps implying significantly higher radiative efficiencies/black hole spins. Reducing black hole masses also reduces the gravitational wave signal expected from black hole mergers.
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