Astr 5460 Wed., Feb. 12, 2003

Today: WIRO: TBA

Reminders/Assignments

MAP!

Longair, Ch. 3 (Galaxies)

Unless noted, all figs and eqs from Longair.

MAP!

NASA press conference yesterday:

Ho=71
T=13.7 Gyr
Omega=1.00
Omega_baryon=0.04
Omega_dm=0.23
Omega_lambda=0.73

First stars at z~16

http://map.gsfc.nasa.gov/m_mm.html

WIRO – science+

Group Assignment: Take notes and develop a WIRO/PFC Observer’s Handbook. Obviously this is delayed, but it would be a good idea to familiarize yourself with the information on the WIRO webpages:

http://physics.uwyo.edu/~mpierce/WIRO/

We will be doing an observing assignment in conjunction with ASTR 5440 involving CMDs of open clusters. Details to come.

Reminders/Preliminaries

Astro-ph preprints for Friday:

http://xxx.lanl.gov/astro-ph

SDSS, 2dF Surveys (Darnel)

Chapter 3: Galaxies

General, basic properties outlined here. More will be covered in ASTR 5440.

Classifications

Luminosity Functions

Galaxy Masses

Elliptical Galaxies

Spiral Galaxies

Correlations with Types

Interacting Galaxies: The Antennae

Interacting Galaxies: Cartwheel

Effects of Collisions

Stars pass “through” each other, although orbits disrupted

Gas clouds collide

Gas stripped away from stars

Collisions cause bursts of star formation

Ellipticals may be galaxies which have suffered collisions

Spirals may be galaxies which have not suffered collisions

Joshua Barnes (Hawaii) and the Space Telescope Science Institude provide a simulation of the Antenna Galaxies: http://imgsrc.stsci.edu/op/pubinfo/pr/1997/34/images/anima.mov

Simulation of the Cartwheel Encounter

From the Space Telescope Science Institute which also provided the Cartwheel image in the textbook:

http://imgsrc.hubblesite.org/hu/discoveries/striking_encounters/graphics/cartwheel.mpg

Luminosity Functions

The frequency with which galaxies of a particular luminosity are found in space. Note that luminosities can be expressed in magnitudes:

Luminosity Functions

Felton (1977):

Luminosity Functions

Solid line is the best fit SCHECHTER (1976) function:

Luminosity Functions

Exact parameters depend on sample. SDSS and 2dF will provide the best estimates soon (Jon?). Typically slopes around a = -1, M_B = -20 (note that quasars by definition more luminous than -23).

Luminosity Functions

Features to note

Morphology matters, also field vs. cluster.

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. More on this in Chapter 4.

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).

Luminosity Functions

Important number is integrated luminosity per unit volume. Power-law is infinite, but integration is finite. The luminosity density is:

Luminosity Density

For some typical numbers we get:

Luminosity Density

So what are observed mass-to-light ratios?

Much lower than critical, and now MAP seems to be confirming baryons 4% of critical, consistent with Big Bang Nucleosynthesis (yes, we will get to this stuff!). Dark matter helps, but only up to about 30%.

Handy numbers

Mean galaxy luminosity is 1.25 L* = 1.55x10¹⁰ h^-2 Lsun

Typical number density of 0.01 h^-3 Mpc^-3 indicates a typical galaxy separation of 5 h^-1 Mpc, but of course on those scales galaxies do cluster (Ch. 2)

Galaxy Masses

On Friday…but an assignment in the meantime (tentatively due Friday Feb 21 – not trivial start early!).

Everyone needs to turn in their own paper, but it is OK to share tasks like web searching, downloading, and the like.

Galaxy Spectra assignment

The textbook is rather weak when it comes to observational properties like spectra – as budding young observers you need to know more!

Find and download the galaxy spectra templates of Kinney et al. (1996) – and read the paper!

Find and download the spectral synthesis population models of Bruzual and Charlot.

“Fit” the elliptical template and one spiral galaxy.

Show some plots indicating how broad-band colors change with redshift assuming not evolution (up to z=2).

Write up your results like you would for publication with clarity, citations, etc.


	Today: WIRO: TBA
	Reminders/Assignments
	MAP!
	Longair, Ch. 3 (Galaxies)



	Unless noted, all figs and eqs from Longair.


	NASA press conference yesterday:
	Ho=71 T=13.7 Gyr Omega=1.00 Omega_baryon=0.04 Omega_dm=0.23 Omega_lambda=0.73 First stars at z~16

	http://map.gsfc.nasa.gov/m_mm.html


	Group Assignment: Take notes and develop a WIRO/PFC Observer’s Handbook. Obviously this is delayed, but it would be a good idea to familiarize yourself with the information on the WIRO webpages:
	http://physics.uwyo.edu/~mpierce/WIRO/
	We will be doing an observing assignment in conjunction with ASTR 5440 involving CMDs of open clusters. Details to come.


	Astro-ph preprints for Friday:
		http://xxx.lanl.gov/astro-ph

	SDSS, 2dF Surveys (Darnel)


	General, basic properties outlined here. More will be covered in ASTR 5440.
		Classifications
		Luminosity Functions
		Galaxy Masses
		Elliptical Galaxies
		Spiral Galaxies
		Correlations with Types


	Stars pass “through” each other, although orbits disrupted

	Gas clouds collide
		Gas stripped away from stars
		Collisions cause bursts of star formation

	Ellipticals may be galaxies which have suffered collisions
	Spirals may be galaxies which have not suffered collisions

	Joshua Barnes (Hawaii) and the Space Telescope Science Institude provide a simulation of the Antenna Galaxies: http://imgsrc.stsci.edu/op/pubinfo/pr/1997/34/images/anima.mov


	From the Space Telescope Science Institute which also provided the Cartwheel image in the textbook:
	http://imgsrc.hubblesite.org/hu/discoveries/striking_encounters/graphics/cartwheel.mpg


	The frequency with which galaxies of a particular luminosity are found in space. Note that luminosities can be expressed in magnitudes:


	Exact parameters depend on sample. SDSS and 2dF will provide the best estimates soon (Jon?). Typically slopes around a = -1, M_B = -20 (note that quasars by definition more luminous than -23).


	Features to note
		Morphology matters, also field vs. cluster.
		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. More on this in Chapter 4.
		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).


	Important number is integrated luminosity per unit volume. Power-law is infinite, but integration is finite. The luminosity density is:


	So what are observed mass-to-light ratios?
		Much lower than critical, and now MAP seems to be confirming baryons 4% of critical, consistent with Big Bang Nucleosynthesis (yes, we will get to this stuff!). Dark matter helps, but only up to about 30%.

	Handy numbers
		Mean galaxy luminosity is 1.25 L* = 1.55x10¹⁰ h^-2 Lsun
		Typical number density of 0.01 h^-3 Mpc^-3 indicates a typical galaxy separation of 5 h^-1 Mpc, but of course on those scales galaxies do cluster (Ch. 2)


	On Friday…but an assignment in the meantime (tentatively due Friday Feb 21 – not trivial start early!).
	Everyone needs to turn in their own paper, but it is OK to share tasks like web searching, downloading, and the like.


	The textbook is rather weak when it comes to observational properties like spectra – as budding young observers you need to know more!
	Find and download the galaxy spectra templates of Kinney et al. (1996) – and read the paper!
	Find and download the spectral synthesis population models of Bruzual and Charlot.
	“Fit” the elliptical template and one spiral galaxy.
	Show some plots indicating how broad-band colors change with redshift assuming not evolution (up to z=2).
	Write up your results like you would for publication with clarity, citations, etc.