Astr 5460 Fri., Jan. 31, 2003

Today: Textbook Ordering

Astro-ph (xxx.lanl.gov)

WIRO: not this weekend

Assignment for Friday check

Email feedback please

Longair, Ch. 2 (Large Scale Struct.)

Unless noted, all figs and eqs from Longair.

Note: This class will meet W&F, 5440 will be M&W

Preliminaries

Astro-ph preprints for the week:

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

Keep looking – we’ll do this every week.

Discuss homework assignment

My solution and ancillary source files will be posted on the webpage (e.g., LaTex, sm, etc.)

Big Bang Essentials

Hubble Expansion

Black Body Background Radiation

Light Element Abundances

Age of oldest stars consistent with Ho age

Very Early Universe

Isotropy – the universe looks the same in all directions, again strictly true on large scales

Small Baryon/Anti-baryon asymmetry

Close to critical (Omega = 1) (will be HW)

Initial fluctuations to seed structure growth

Longair Chapter 2

Large scale distribution of radiation and matter in the Universe as determined through observational work.

Cosmic Microwave Background Radiation

Large-scale Distribution of Galaxies

Hubble’s Law

Cosmic Microwave Background Observations

First detected by Wilson and Penzias in 1960’s

Serendipitous detection – thought is was noise in their radio telescope but couldn’t find cause. Only later heard of theoretical predictions

Best spectrum observed by COBE satellite

Red curve is theoretical prediction

43 Observed data points plotted there
error bars so small they are covered by curve.

it is covered by curve.

Isotropy also measured by COBE

T varies by less than 0.01 K across sky

Small “dipole” anisotropy seen

Blue = 2.721 Red = 2.729

Caused by motion of Milky Way falling towards the Virgo supercluster.

Research Notes

Some Hubble studies performed using the CMBR as the reference-frame for galaxy velocities. Heliocentric velocities are relative to the sun, and there is still the motion of the sun around the Milky Way (about 225 km/s) and the motion of the Milky Way.

Who will volunteer to do a short presentation on the MAP and PLANCK missions next week?

Slide 8

Background Temp. Fluctuations

Zeldovich and Sunyaev in late 1960s:

Injection of energy at z > 1000, then leads to an equilibrium Bose-Einstein spectrum which depends on a dimensionless chemical potential μ:

Background Temp. Fluctuations

Zeldovich and Sunyaev in late 1960s:

Compton scattering by hot electrons in the IGM leads to a distortion of the background spectrum:

CMBR: How Isotropic?

Homework Assignment

Verify by next Friday that if you redshift a blackbody spectrum that the spectrum remains a blackbody and that the blackbody temperature changes by a factor of 1+z. You need not turn this assignment in, but I may ask someone to demonstrate this on the blackboard.

Large-scale Distribution of Galaxies

Large-scale Distribution of Galaxies

On small scales, the universe is very inhomogeneous (stars, galaxies). What about larger scales?

Angular two-point correlation function w(θ):

Large-scale Distribution of Galaxies

This function w(θ) describes apparent clustering on the sky down to some magnitude limit.

More physically meaningful is the spatial two-point correlation function ξ(r) which describes clustering in 3-D about a galaxy:

Large-scale Distribution of Galaxies

w(θ) isn’t so hard to measure from various surveys – just need positions.

ξ(r) is harder – must have redshifts to do properly. Can make some assumptions however.

Large-scale Distribution of Galaxies

Hubble’s Law and Expansion

Conclusions

On the largest scales it is appropriate to impose the conditions of isotropy and homogeneity, plus uniform expansion.

These simplifications plus GR provide relatively simple “world models” that provide a framework for cosmology and the origin of galaxies and other large scale structures.

Hubble’s Law and Expansion


	Today: Textbook Ordering
	Astro-ph (xxx.lanl.gov)
	WIRO: not this weekend
	Assignment for Friday check
	Email feedback please
	Longair, Ch. 2 (Large Scale Struct.)

	Unless noted, all figs and eqs from Longair.
	Note: This class will meet W&F, 5440 will be M&W


	Astro-ph preprints for the week:
		http://xxx.lanl.gov/astro-ph
	Keep looking – we’ll do this every week.

	Discuss homework assignment
		My solution and ancillary source files will be posted on the webpage (e.g., LaTex, sm, etc.)


	Hubble Expansion

	Black Body Background Radiation

	Light Element Abundances

	Age of oldest stars consistent with Ho age


	Isotropy – the universe looks the same in all directions, again strictly true on large scales

	Small Baryon/Anti-baryon asymmetry

	Close to critical (Omega = 1) (will be HW)

	Initial fluctuations to seed structure growth


	Large scale distribution of radiation and matter in the Universe as determined through observational work.
	Cosmic Microwave Background Radiation
	Large-scale Distribution of Galaxies
	Hubble’s Law


First detected by Wilson and Penzias in 1960’s
	Serendipitous detection – thought is was noise in their radio telescope but couldn’t find cause. Only later heard of theoretical predictions

Best spectrum observed by COBE satellite
	Red curve is theoretical prediction
	43 Observed data points plotted there error bars so small they are covered by curve.
	it is covered by curve.

Isotropy also measured by COBE
	T varies by less than 0.01 K across sky
	Small “dipole” anisotropy seen
		Blue = 2.721 Red = 2.729
		Caused by motion of Milky Way falling towards the Virgo supercluster.


	Some Hubble studies performed using the CMBR as the reference-frame for galaxy velocities. Heliocentric velocities are relative to the sun, and there is still the motion of the sun around the Milky Way (about 225 km/s) and the motion of the Milky Way.
	Who will volunteer to do a short presentation on the MAP and PLANCK missions next week?


	Zeldovich and Sunyaev in late 1960s:
		Injection of energy at z > 1000, then leads to an equilibrium Bose-Einstein spectrum which depends on a dimensionless chemical potential μ:


	Zeldovich and Sunyaev in late 1960s:
		Compton scattering by hot electrons in the IGM leads to a distortion of the background spectrum:


	Verify by next Friday that if you redshift a blackbody spectrum that the spectrum remains a blackbody and that the blackbody temperature changes by a factor of 1+z. You need not turn this assignment in, but I may ask someone to demonstrate this on the blackboard.


	On small scales, the universe is very inhomogeneous (stars, galaxies). What about larger scales?
	Angular two-point correlation function w(θ):


	This function w(θ) describes apparent clustering on the sky down to some magnitude limit.
	More physically meaningful is the spatial two-point correlation function ξ(r) which describes clustering in 3-D about a galaxy:


	w(θ) isn’t so hard to measure from various surveys – just need positions.
	ξ(r) is harder – must have redshifts to do properly. Can make some assumptions however.


	On the largest scales it is appropriate to impose the conditions of isotropy and homogeneity, plus uniform expansion.
	These simplifications plus GR provide relatively simple “world models” that provide a framework for cosmology and the origin of galaxies and other large scale structures.