Secular Evolution in Disk Galaxies: Pseudobulge Growth and the Formation of Spheroidal Galaxies

Updating Kormendy & Kennicutt (2004, ARAA, 42, 603), we review internal secular evolution of galaxy disks. One consequence is the growth of pseudobulges that often are mistaken for true (merger-built) bulges. Many pseudobulges are recognizable as cold, rapidly rotating, disky structures. Bulges have Sersic function brightness profiles with index n > 2; most pseudobulges have n <= 2. Recognition of pseudobulges makes the biggest problem with cold dark matter galaxy formation more acute: How can hierarchical clustering make so many pure disk galaxies with no evidence for merger-built bulges? E. g., the giant Scd galaxies M101 and NGC 6946 have rotation velocities of V ~ 200 km/s but nuclear star clusters with velocity dispersions of 25 to 40 km/s. Within 8 Mpc of us, 11 of 19 galaxies with V > 150 km/s show no evidence for a classical bulge, while only 7 are ellipticals or have classical bulges. It is hard to understand how bulgeless galaxies could form as the quiescent tail of a distribution of merger histories. Our second theme is environmental secular evolution. We confirm that spheroidal galaxies have fundamental plane (FP) correlations that are almost perpendicular to those for bulges and ellipticals. Spheroidals are not dwarf ellipticals. Rather, their structural parameters are similar to those of late-type galaxies. We suggest that spheroidals are defunct late-type galaxies transformed by internal processes such as supernova-driven gas ejection and environmental processes such as secular harassment and ram-pressure stripping. Minus spheroidals, the FP of ellipticals and bulges has small scatter. With respect to these, pseudobulges are larger and less dense.Comment: 11 pages, 6 Postscript figures; requires asp2006.sty; as published, except with updated references; for a version with full resolution figures, see http://chandra.as.utexas.edu/~kormendy/kormendy-rome.pd

Galaxy Clustering Around Nearby Luminous Quasars

We examine the clustering of galaxies around a sample of 20 luminous low redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope. The HST resolution makes possible galaxy identification brighter than V=23.5 and as close as 2'' to the quasar. We find a significant enhancement of galaxies within a projected separation of < 100 kpc/h of the quasars. If we model the qso/galaxy correlation function as a power law with a slope given by the galaxy/galaxy correlation function, we find that the ratio of the qso/galaxy to galaxy/galaxy correlation functions is $3.8\pm 0.8$. The galaxy counts within r<15 kpc/h of the quasars are too high for the density profile to have an appreciable core radius ( > 100 kpc). Our results reinforce the idea that low redshift quasars are located preferentially in groups of 10-20 galaxies rather than in rich clusters. We see no significant difference in the clustering amplitudes derived from radio-loud and radio-quiet subsamples.Comment: 16 pages, 3 figures (included), 2 tables, Apj in pres

The Logarithmic Triviality of Compact QED Coupled to a Four Fermi Interaction

This is the completion of an exploratory study of Compact lattice Quantum Electrodynamics with a weak four-fermi interaction and four species of massless fermions. In this formulation of Quantum Electrodynamics massless fermions can be simulated directly and Finite Size Scaling analyses can be performed at the theory's chiral symmetry breaking critical point. High statistics simulations on lattices ranging from $8^4$ to $24^4$ yield the equation of state, critical indices, scaling functions and cumulants. The measurements are well fit with the orthodox hypothesis that the theory is logarithmically trivial and its continuum limit suffers from Landau's zero charge problem.Comment: 27 pages, 15 figues and 10 table

A Discotic Disguised as a Smectic: A Hybrid Columnar Bragg Glass

We show that discotics, lying deep in the columnar phase, can exhibit an x-ray scattering pattern which mimics that of a somewhat unusual smectic liquid crystal. This exotic, new glassy phase of columnar liquid crystals, which we call a ``hybrid columnar Bragg glass'', can be achieved by confining a columnar liquid crystal in an anisotropic random environment of e.g., strained aerogel. Long-ranged orientational order in this phase makes {\em single domain} x-ray scattering possible, from which a wealth of information could be extracted. We give detailed quantitative predictions for the scattering pattern in addition to exponents characterizing anomalous elasticity of the system.Comment: 4 RevTeX pgs, 2 eps figures. To appear in PR

STRUCTURE AND FORMATION OF cD GALAXIES: NGC 6166 IN ABELL 2199

Hobby–Eberly Telescope (HET) spectroscopy is used to measure the velocity dispersion profile of the nearest prototypical cD galaxy, NGC 6166 in the cluster Abell 2199. We also present composite surface photometry from many telescopes. We confirm the defining feature of a cD galaxy; i.e., (we suggest), a halo of stars that fills the cluster center and that is controlled dynamically by cluster gravity, not by the central galaxy. Our HET spectroscopy shows that the velocity dispersion of NGC 6166 rises from σ ≃ 300 km s[superscript −1] in the inner r ~ 10" to σ = 865 ± 58 km s[superscript −1] at r ~ 100'' in the cD halo. This extends published observations of an outward σ increase and shows for the first time that σ rises all the way to the cluster velocity dispersion of 819 ± 32 km s[superscript −1]. We also observe that the main body of NGC 6166 moves at +206 ± 39 km s[superscript −1] with respect to the cluster mean velocity, but the velocity of the inner cD halo is ~70 km s[superscript −1] closer to the cluster velocity. These results support our picture that cD halos consist of stars that were stripped from individual cluster galaxies by fast tidal encounters. However, our photometry does not confirm the widespread view that cD halos are identifiable as an extra, low-surface-brightness component that is photometrically distinct from the inner, steep-Sérsic-function main body of an otherwise-normal giant elliptical galaxy. Instead, all of the brightness profile of NGC 6166 outside its core is described to ±0.037 V mag arcsec[superscript −2] by a single Sérsic function with index n ≃ 8.3. The cD halo is not recognizable from photometry alone. This blurs the distinction between cluster-dominated cD halos and the similarly-large-Sérsic-index halos of giant, core-boxy-nonrotating ellipticals. These halos are believed to be accreted onto compact, high-redshift progenitors ("red nuggets") by large numbers of minor mergers. They belong dynamically to their central galaxies. Still, cDs and core-boxy-nonrotating Es may be more similar than we think: both may have outer halos made largely via minor mergers and the accumulation of tidal debris. We construct a main-body+cD-halo decomposition that fits both the brightness and dispersion profiles. To fit σ(r), we need to force the component Sérsic indices to be smaller than a minimum-x[superscript 2] photometric decomposition would suggest. The main body has M[subscript V] ≃ -22.8 ≃ 30% of the total galaxy light. The cD halo has M[subscript V] ≃ -23.7, ~1/2 mag brighter than the brightest galaxy in the Virgo cluster. A mass model based on published cluster dynamics and X-ray observations fits our observations if the tangential dispersion is larger than the radial dispersion at r ≃ 20"–60". The cD halo is as enhanced in α element abundances as the main body of NGC 6166. Quenching of star formation in [< over ~]1 Gyr suggests that the center of Abell 2199 has been special for a long time during which dynamical evolution has liberated a large mass of now-intracluster stars

Volcanic Diffuse Volatile Emissions Tracked by Plant Responses Detectable From Space

Volcanic volatile emissions provide information about volcanic unrest but are difficult to detect with satellites. Volcanic degassing affects plants by elevating local CO2 and H2O concentrations, which may increase photosynthesis. Satellites can detect plant health, or a reaction to photosynthesis, through a Normalized Difference Vegetation Index (NDVI). This can act as a potential proxy for detecting changes in volcanic volatile emissions from space. We tested this method by analyzing 185 Landsat 5 and 8 images of the Tern Lake thermal area (TLTA) in northeast Yellowstone caldera from 1984 to 2022. We compared the NDVI values of the thermal area with those of similar nearby forests that were unaffected by hydrothermal activity to determine how hydrothermal activity impacted the vegetation. From 1984 to 2000, plant health in the TLTA steadily increased relative to the background forests, suggesting that vegetation in the TLTA was fertilized by volcanic CO2 and/or magmatic water. Hydrothermal activity began to stress plants in 2002, and by 2006, large swathes of trees were dying in the hydrothermal area. Throughout most of the 1990s, the least healthy plants were located in the area which became the epicenter of hydrothermal activity in 2000. These findings suggest that plant-focused measurements are sensitive to minor levels of volcanic unrest which may not be detected by other remote sensing methods, such as infrared temperature measurements. This method could be a safe and effective new tool for detecting changes in volatile emissions in volcanic environments which are dangerous or difficult to access