Astr 5460 Wed. Sep. 8, 2004

Today: Classification and Morphology

Kinematics and Masses

(Skipping Ch. 2 of Combes et al. on ISM. If you didn’t take ISM last spring, you should read it.)

Unless noted, all figs and equations from Combes et al. or Longair’s Galaxy Formation.

Homework questions/discussion

WIRO discussion

Luminosity Functions

Features to note

Morphology matters, also field vs. cluster.

L* or M* in rich clusters isn’t a bad “standard candle”

cD galaxies in cluster centers are special cases; they are like massive ellipticals but have extra stellar envelopes. They do not fit extrapolations of ellipitical LFs.

Low luminosity end of LFs not well determined (Irr and dwarf ellipticals). Again SDSS will probably be the best word on this (if it goes faint enough).

Frequency of Galaxy Types:
As a function of clustering

Trends along Hubble Sequence

Trends along Hubble Sequence

Roberts & Haynes 1994:

Trends along Hubble Sequence

Roberts & Haynes 1994:

Masses from S0 to Scd roughly constant, then decrease, and M/L roughly the same – more next chapter (3)

H I not significant in ellipticals (< 1 in 10000), but is in spirals (0.01 to 0.15 from Sa to Sm) (see Ch. 2)

Total surface density decreases, H I surface density increases

Ellipticals are red, spirals are blue…

H II regions frequency increases monotonically along the sequence (Kennicutt et al. 1989)

Star formation rates appear key to these relations

Cosmic Star Formation History

From Hopkins et al. (2001)

Kinematics and Masses of Galaxies (Ch. 3, Combes et. al)

Optical Determinations

Methods – optical rotation curves

Properties of rotation curves

Radio Determinations – HI maps

Mass Distributions

Methods of Analysis

M/L Ratios

Tully-Fischer Law

Kinematics and Masses of Galaxies

Taken both from Combes et al. and Longair, as needed.

How do we measure the masses of astronomical objects, in general? Of binary stars? Of single stars? Of groups of many objects, like galaxies?

Galaxy Masses

Rotation Curves of Spiral Galaxies:

This just comes from Newton, by equating gravity to centripetal acceleration. This produces Kepler’s third law, and “Keplerian” orbital velocities around point sources fall off as r^-1/2. How about for galaxies?

The Galactic Rotation Curve

Keplerian fall-off near center indicates compact mass at center

Flat curve throughout disk indicates much distributed mass

Lack of fall-off beyond visible “edge” indicates “dark matter”

Galaxy Rotation Curves

Normalized mass distributions based on average rotation curves for different “types.” Sc is type I, Sa and Sb are of all three types.

The famous Tully-Fisher law (basically L ~ V4). Mike Pierce is an expert. Why is H-band better and why is this so important in extragalactic astronomy?

What is its origin?


	Today: Classification and Morphology
	Kinematics and Masses

	(Skipping Ch. 2 of Combes et al. on ISM. If you didn’t take ISM last spring, you should read it.)

	Unless noted, all figs and equations from Combes et al. or Longair’s Galaxy Formation.

	Homework questions/discussion
	WIRO discussion


	Features to note
		Morphology matters, also field vs. cluster.
		L* or M* in rich clusters isn’t a bad “standard candle”
		cD galaxies in cluster centers are special cases; they are like massive ellipticals but have extra stellar envelopes. They do not fit extrapolations of ellipitical LFs.
		Low luminosity end of LFs not well determined (Irr and dwarf ellipticals). Again SDSS will probably be the best word on this (if it goes faint enough).


	Roberts & Haynes 1994:
		Masses from S0 to Scd roughly constant, then decrease, and M/L roughly the same – more next chapter (3)
		H I not significant in ellipticals (< 1 in 10000), but is in spirals (0.01 to 0.15 from Sa to Sm) (see Ch. 2)
		Total surface density decreases, H I surface density increases
		Ellipticals are red, spirals are blue…
		H II regions frequency increases monotonically along the sequence (Kennicutt et al. 1989)
	Star formation rates appear key to these relations


	Optical Determinations
		Methods – optical rotation curves
		Properties of rotation curves
	Radio Determinations – HI maps
	Mass Distributions
		Methods of Analysis
		M/L Ratios
		Tully-Fischer Law


	Taken both from Combes et al. and Longair, as needed.

	How do we measure the masses of astronomical objects, in general? Of binary stars? Of single stars? Of groups of many objects, like galaxies?


	Rotation Curves of Spiral Galaxies:



	This just comes from Newton, by equating gravity to centripetal acceleration. This produces Kepler’s third law, and “Keplerian” orbital velocities around point sources fall off as r^-1/2. How about for galaxies?


	Keplerian fall-off near center indicates compact mass at center
	Flat curve throughout disk indicates much distributed mass
	Lack of fall-off beyond visible “edge” indicates “dark matter”


	The famous Tully-Fisher law (basically L ~ V4). Mike Pierce is an expert. Why is H-band better and why is this so important in extragalactic astronomy?
	What is its origin?