BULGELESS GIANT GALAXIES CHALLENGE OUR PICTURE OF GALAXY FORMATION BY HIERARCHICAL CLUSTERING,

By J. Kormendy, N. Drory, R. Bender, M. Cornell. 2010

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To better understand the prevalence of bulgeless galaxies in the nearby field, we dissect giant Sc–Scd galaxies with Hubble Space Telescope (HST) photometry and Hobby–Eberly Telescope (HET) spectroscopy. We use the HET High Resolution Spectrograph (resolution R ≡ λ/FWHM ≃ 15, 000) to measure stellar velocity dispersions in the nuclear star clusters and (pseudo)bulges of the pure-disk galaxies M 33, M 101, NGC 3338, NGC 3810, NGC 6503, and NGC 6946. The dispersions range from 20 ± 1 km s−1 in the nucleus of M 33 to 78 ± 2 km s−1 in the pseudobulge of NGC 3338. We use HST archive images to measure the brightness profiles of the nuclei and (pseudo)bulges in M 101, NGC 6503, and NGC 6946 and hence to estimate their masses. The results imply small mass-to-light ratios consistent with young stellar populations. These observations lead to two conclusions. (1) Upper limits on the masses of any supermassive black holes are M• ≲ (2.6 ± 0.5) × 106 M☉ in M 101 and M• ≲ (2.0 ± 0.6) × 106 M☉ in NGC 6503. (2) We show that the above galaxies contain only tiny pseudobulges that make up ≲3% of the stellar mass. This provides the strongest constraints to date on the lack of classical bulges in the biggest pure-disk galaxies. We inventory the galaxies in a sphere of radius 8 Mpc centered on our Galaxy to see whether giant, pure-disk galaxies are common or rare. We find that at least 11 of 19 galaxies with Vcirc > 150 km s−1, including M 101, NGC 6946, IC 342, and our Galaxy, show no evidence for a classical bulge. Four may contain small classical bulges that contribute 5%–12% of the light of the galaxy. Only four of the 19 giant galaxies are ellipticals or have classical bulges that contribute ∼1/3 of the galaxy light. We conclude that pure-disk galaxies are far from rare. It is hard to understand how bulgeless galaxies could form as the quiescent tail of a distribution of merger histories. Recognition of pseudobulges makes the biggest problem with cold dark matter galaxy formation more acute: How can hierarchical clustering make so many giant, pure-disk galaxies with no evidence for merger-built bulges? Finally, we emphasize that this problem is a strong function of environment: the Virgo cluster is not a puzzle, because more than 2/3 of its stellar mass is in merger remnants.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/9334ea92efe47e85bf99d0274c3bc8086b32a413

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Citations in the corpus

Theoretical Challenges in Galaxy Formation (2016, background): “…considerations must be important in understanding their formation, since isolated systems tend to be disk dominated and those in regions of high galactic density tend to be dominated by the spheroidal component (e.g. Blanton & Moustakas 2009, Cappellari 2011, Dressler 1980, Kormendy et al. 2010).”
Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions (2011, background): “This could mean that the Local Volume is just a statistical anomaly, but it could also point, in line with the two previous challenges, towards more rapid structure formation, allowing sparse regions to more quickly form large galaxies cleaning their environment, making the galaxies larger and the v”
Cosmological simulations of the formation of the stellar haloes around disc galaxies (2011, background): “Kormendy et al. (2010) have recently demonstrated, using high quality photometric and spectropscopic observations, that many of the largest nearby disc galaxies lack obvious classical bulge components (i.e., are “bulgeless”).”
The Milky Way’s stellar disk (2013, background): “…for the Milky Way in particular, but lead generically to the question of how resilient stellar disks are to tidal interactions; it has been claimed (e.g., Kormendy et al. 2010; Shen et al. 2010) that the existence of large, thin stellar disks poses a challenge to the merger-driven ΛCDM picture.”
The Evolution of Galaxy Structure Over Cosmic Time (2014, background): “Disk properties are also highly environmentally driven, with few classical bulge or elliptical systems in low density environments (Kormendy et al. 2010).”
Nuclear star clusters (2009, background): “Since the integrated velocity dispersions of NSCs are typically low (< 20− 30km/s), the spectral resolution of the observations needs to be sufficiently high (R&5000, e.g. Walcher et al. 2005; Kormendy et al. 2010).”
Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation (2014, background): “But the majority of disk galaxies do not have a classical bulge [142,143], while 94 % of isolated disk galaxies which typically must also have grown via mergers if the SMoC is to be valid do not appear to have classical bulges [144].”
Hierarchical formation of bulgeless galaxies – II. Redistribution of angular momentum via galactic fountains (2011, background): “This means that the large scale outflow of low angular momentum gas is not likely to explain the fact that many massive disc galaxies do not have classical bulges (Kormendy et al. 2010).”
A DIVERSITY OF PROGENITORS AND HISTORIES FOR ISOLATED SPIRAL GALAXIES (2012, background): “Even more stricking is the fact that 80% of local galaxies (i.e. within the local 11 Mpc sphere) more massive than 109 M are either bulgeless or only have a pseudobulge (Fisher & Drory 2011, see also Kautsch et al. 2006 and Kormendy et al. 2010).”
THE EMISSION BY DUST AND STARS OF NEARBY GALAXIES IN THE HERSCHEL KINGFISH SURVEY (2011, background): “They include both passive spirals as well as spirals with obscured star formation (Masters et al. 2010b). massive galaxies experience major mergers (Kormendy et al. 2010); however, they both have a very large gas supply (Walter et al. 2008) with which they could potentially form stars, and NGC 6946…”
The current status of galaxy formation (2012, background): “Massive bulgeless galaxies with thin disks are reasonably common (Kormendy et al., 2010).”
A REVISED PARALLEL-SEQUENCE MORPHOLOGICAL CLASSIFICATION OF GALAXIES: STRUCTURE AND FORMATION OF S0 AND SPHEROIDAL GALAXIES (2011, background): “Moreover, Sc galaxies do not contain classical bulges, and later-type galaxies scarcely even contain pseudobulges (Kormendy & Kennicutt 2004; Kormendy et al. 2010).”
FORMING REALISTIC LATE-TYPE SPIRALS IN A ΛCDM UNIVERSE: THE ERIS SIMULATION (2011, background): “More typical galaxies undergoing significant mergers at later times may develop smaller bulges due to the more prolonged effect of supernovae outflows, which could explain why 11 out of 19 nearby massive spirals show no evidence for a classical bulge (Kormendy et al. 2010)).”
Physical Models of Galaxy Formation in a Cosmological Framework (2014, background): “The flip side of producing enough spheroid dominated galaxies is the challenge of producing galaxies that are close to pure disks, which are perhaps surprisingly frequently observed in the real Universe (Fisher & Drory 2011, Kormendy et al. 2010).”
Coevolution (Or Not) of Supermassive Black Holes and Host Galaxies (2013, methodology): “…Virgo cluster (no W′ cloud); (5) Thomsen et al. (1997) SBF distance to NGC 4881 in the Coma cluster; (6) mean of distance determinations adopted in Kormendy et al. (2010); sources are given there; (7) Monachesi et al. (2011); agrees with (8); (8) mean of many determinations listed on NED, using…”
The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology (2012, background): “Similarly, Kormendy et al. (2010) state ‘It is hard to understand how bulge-less galaxies could formas the quiescent tail of a distribution of merger histories.’”
Reconstructing the star formation history of the Milky Way disc(s) from chemical abundances (2014, unknown): “These conclusions make the Milky Way fit its local environment: Kormendy et al. (2010) and Fisher & Drory (2012) showed that within 10 and 12 Mpc, the dominant type among giant discs are either pure discs or disc with pseudo bulges.”
CALIBRATING EXTINCTION-FREE STAR FORMATION RATE DIAGNOSTICS WITH 33 GHz FREE–FREE EMISSION IN NGC 6946 (2011, background): “Such a scenario seems plausible given the large stellar densities associated with the pseudobulge of NGC6946 (Kormendy et al. 2010) which completely fills our beam; the radius of the bulge is ≈15′′ (Regan & Vogel 1995) and contains a stellar minibar (Elmegreen et al. 1998).”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “In key respects, the Milky Way is typical of large galaxies today in low-density environments (Kormendy et al. 2010), especially with a view to global parameters (e.g., current SFR ṁ , baryon fraction fbary) given its total stellar mass (cf. de Rossi et al. 2009), as we discuss below.”