NGC4603

Cepheids in NGC4603

Planetary Nebula Luminosity FunctionN

umbe

r

Milky Way novae

Planetaries vs. Cepheids

Tip of Red Giant Branch (TRGB) vs. Cepheids

SBF vs. Cepheids

SN1994d (HST Image)

At peak brightness, SNe are comparable in brightness to a large spiral galaxy = you can see them out to Gpc distances

High-redshift SN

SN Light Curves - Type Ia

Note: this doesn’t work in the “R” or “I” bands (which is what you want to use for dusty host galaxies)

The brightest SNe (intrinsically) have a longer rise and decline time; the faintest have a shorter rise and decline time

Type Ia Light Curves in Different Bandpasses

Peak in brightness occurs at different times in different bandpasses, and in some cases there is a secondary peak (i.e., wavelengths longer than R band)

Vertical axis: number of magnitudes by which the SN has declined in B-band over the first 15 days after maximum brightness

Horizontal axis: mean I-band flux (relative to maximum) over the 20 to 40 days after the max. brightness in B-band occurred

Vertical axis: I-band flux of the supernova (relative to maximum I-band flux)

Horizontal axis: time since the maximum in B-band occurred (note the “negative time”!!)

Another way to calibrate Type Ia SNe

If cosmological constant is not zero, what do you expect to see?

• Cosmological constant acts like “anti-gravity”; should cause the universe to expand more quickly than would otherwise expect (i.e., it should make the universe’s “brakes” weaker or even non-existent)

• Faster than expected expansion = bigger distances to cosmological objects than expected = standard candles (i.e., Type I-a SNe) should seem “fainter” than they otherwise would be for their observed redshift

• Also should be a characteristic imprint on the temperature fluctuations of the CMBR (we’ve already seen this)

• SNe Type I-a don’t know ANYTHING about the CMBR (and vice versa), so if both suggest the presence of a cosmological constant, then either the universe is toying with us perversely OR we’re really on to something!

Classical Hubble Diagram for Type Ia Supernovae; at z=1.0 the difference in expected magnitude for 3 wildly different cosmogonies is only about 0.5mag!!

Flat, matter-dom. universeOpen universeFlat, Lambda-dominated

“Residual Hubble Diagram” from Knop et al (2003); universe with no mass and no cosmological constant / “dark energy” is a flat line for all redshifts

Search for z > 1 SNe carried out by Riess et al. using HST in conjunction with GOODS survey (ACS + NICMOS ToO follow-up); obtained 16

SNe, including 6 of the 7 highest-z SNe known

Riess et al. (2004); High-z supernovae from HST show universe decelerated in the past, transition happened at z = 0.46 +/- 0.13

“Jerk” is a purely kinematic model; the jerk is the derivative of the deceleration parameter, and deceleration parameter is the derivative of the Hubble parameter

Cluster constraints on matter density come from “total” mass-to-light ratio, assuming clusters are “fair samples” of the universe; can also include constraints on P(k) from large-scale structure observations

Cluster constraints on dark energy come from evolution of the cluster mass function with redshift (poor at the moment due to lack of high-z clusters, but will improve!)