5,434 research outputs found
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
Recommended from our members
Skill Rating by Bayesian Inference
Systems Engineering often involves computer modelling the behaviour of proposed systems and their components. Where a component is human, fallibility must be modelled by a stochastic agent. The identification of a model of decision-making over quantifiable options is investigated using the game-domain of Chess. Bayesian methods are used to infer the distribution of players’ skill levels from the moves they play rather than from their competitive results. The approach is used on large sets of games by players across a broad FIDE Elo range, and is in principle applicable to any scenario where high-value decisions are being made under pressure
Light-depth relationship for activated algae
Dissertation (Ph. D.)--University of Kansas, Civil Engineering, 1972
A global magnetic anomaly map
A subset of POGO satellite magnetometer data has been formed that is suitable for analysis of crustal magnetic anomalies. Using a thirteenth order field model, fit to these data, magnetic residuals have been calculated over the world to latitude limits of plus 50 deg. These residuals averaged over one degree latitude-longitude blocks represent a detailed global magnetic anomaly map derived solely from satellite data. Preliminary analysis of the map indicates that the anomalies are real and of geological origin
Investigation of the fiber reinforcement of a cobalt base alloy for application at elevated temperature
Technique developed for incorporating alumina and silicon carbide fibers in cobalt base alloy for application at high temperature
- …