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

Central Star Formation in Pseudobulges and Classical Bulges

I use Spitzer 3.6-8.0 \mu m color profiles to compare the radial structure of star formation in pseudobulges and classical bulges. Pseudobulges are ``bulges'' which form through secular evolution, rather than mergers. In this study, pseudobulges are identified using the presence of disk-like structure in the center of the galaxy (nuclear spiral, nuclear bar, and/or high ellipticity in bulge); classical bulges are those galaxy bulges with smooth isophotes which are round compared to the outer disk, and show no disky structure in their bulge. I show that galaxies structurally identified as having pseudobulges have higher central star formation rates than those of classical bulges. Further, I also show that galaxies identified as having classical bulges have remarkably regular star formation profiles. The color profiles of galaxies with classical bulges show a star forming outer disk with a sharp change, consistent with a decline in star formation rates, toward the center of the galaxy. Classical bulges have a nearly constant inner profile (r < 1.5 kpc) that is similar to elliptical galaxies. Pseudobulges in general show no such transition in star formation properties from the outer disk to the central pseudobulge. Thus I conclude that pseudobulges and classical bulges do in fact form their stars via different mechanisms. Further, this adds to the evidence that classical bulges form most of their stars in fast episodic bursts, in a similar fashion to elliptical galaxies; whereas, pseudobulges form stars from longer lasting secular processes.Comment: accepted to ApJ Letter

Expert systems in typography

Electronic publishing systems are providing authors with a tremendous amount of power formerly only available to printers: the choice of typographic design and layout. However, many authors use this power without the proper background, with potentially disastrous results. We have developed a prototype expert system that provides users of electronic publishing systems with the printer\u27s knowledge in computer form in one narrow area of the publishing field to aid them in preparing their publications

Satellite Sampling and Retrieval Errors in Regional Monthly Rain Estimates from TMI AMSR-E, SSM/I, AMSU-B and the TRMM PR

Passive and active microwave rain sensors onboard earth-orbiting satellites estimate monthly rainfall from the instantaneous rain statistics collected during satellite overpasses. It is well known that climate-scale rain estimates from meteorological satellites incur sampling errors resulting from the process of discrete temporal sampling and statistical averaging. Sampling and retrieval errors ultimately become entangled in the estimation of the mean monthly rain rate. The sampling component of the error budget effectively introduces statistical noise into climate-scale rain estimates that obscure the error component associated with the instantaneous rain retrieval. Estimating the accuracy of the retrievals on monthly scales therefore necessitates a decomposition of the total error budget into sampling and retrieval error quantities. This paper presents results from a statistical evaluation of the sampling and retrieval errors for five different space-borne rain sensors on board nine orbiting satellites. Using an error decomposition methodology developed by one of the authors, sampling and retrieval errors were estimated at 0.25 resolution within 150 km of ground-based weather radars located at Kwajalein, Marshall Islands and Melbourne, Florida. Error and bias statistics were calculated according to the land, ocean and coast classifications of the surface terrain mask developed for the Goddard Profiling (GPROF) rain algorithm. Variations in the comparative error statistics are attributed to various factors related to differences in the swath geometry of each rain sensor, the orbital and instrument characteristics of the satellite and the regional climatology. The most significant result from this study found that each of the satellites incurred negative longterm oceanic retrieval biases of 10 to 30%

The Molecular Gas Density in Galaxy Centers and How It Connects to Bulges

In this paper we present gas density, star formation rate, stellar masses, and bulge disk decompositions for a sample of 60 galaxies. Our sample is the combined sample of BIMA SONG, CARMA STING, and PdBI NUGA surveys. We study the effect of using CO-to-H_2 conversion factors that depend on the CO surface brightness, and also that of correcting star formation rates for diffuse emission from old stellar populations. We estimate that star formation rates in bulges are typically lower by 20% when correcting for diffuse emission. We find that over half of the galaxies in our sample have molecular gas surface density >100 M_sun pc^-2. We find a trend between gas density of bulges and bulge Sersic index; bulges with lower Sersic index have higher gas density. Those bulges with low Sersic index (pseudobulges) have gas fractions that are similar to that of disks. We also find that there is a strong correlation between bulges with the highest gas surface density and the galaxy being barred. However, we also find that classical bulges with low gas surface density can be barred as well. Our results suggest that understanding the connection between the central surface density of gas in disk galaxies and the presence of bars should also take into account the total gas content of the galaxy and/or bulge Sersic index. Indeed, we find that high bulge Sersic index is the best predictor of low gas density inside the bulge (not barredness of the disk). Finally, we show that when using the corrected star formation rates and gas densities, the correlation between star formation rate surface density and gas surface density of bulges is similar to that of disks.Comment: Accepted for publication in Ap

A Classroom Experiment on Exchange Rate Determination with Purchasing Power Parity

We develop a classroom experiment on exchange rate determination appropriate for undergraduate courses in macroeconomics and international economics. Students represent citizens from different countries and need to obtain currency to purchase goods. By participating in a sealed bid auction to buy currency, students gain a better understanding of currency markets and the determination of exchange rates. The implicit framework for exchange rate determination is one in which prices are perfectly flexible (in the long run) so that purchasing power parity (PPP) prevails. Additional treatments allow students to examine the impact of transport costs, nontradable goods and tariffs on the exchange rate and to explore possible deviations from PPP.

Direct introduction of nitrogen and oxygen functionality with spatial control using copper catalysis.

Synthetic chemists have spent considerable effort optimizing the synthesis of nitrogen and oxygen containing compounds through a number of methods; however, direct introduction of N- and O-functionality remains challenging. Presented herein is a general method to allow for the simultaneous installation of N- and O-functionality to construct unexplored N-O heterocyclic and amino-alcohol scaffolds. This transformation uses earth abundant copper salts to facilitate the formation of a carbon-centered radical and subsequent carbon-nitrogen bond formation. The intermediate aminoxyl radical is terminated by an intramolecularly appended carbon-centered radical. We have exploited this methodology to also access amino-alcohols with a range of aliphatic and aromatic linkers