# How does the Tully-Fisher relation work?

Table of Contents

## How does the Tully-Fisher relation work?

The key point of the Tully-Fisher relationship is that the speed of rotation of material in a spiral galaxy is related to the luminosity of that galaxy: high speeds occur in galaxies of high luminosity. To establish this fact, TF77 carefully selected galaxies for which rotation velocities could be measured accurately.

What is the Tully-Fisher relationship How can we use this to measure distance over what distances can it be used?

The Tully-Fisher relation is a correlation between the luminosity and the HI 21cm line width in spiral galaxies (LLW relation). It is used to derive galaxy distances in the interval 7 to 100 Mpc. Closer, the Cepheids, TRGB and Surface Brightness Fluctuation methods give a better accuracy.

### What is the physical significance of the Tully-Fisher relation for spiral galaxies?

We find a new Tully–Fisher-like relation for spiral galaxies holding at different galactocentric radii. This radial Tully–Fisher relation allows us to investigate the distribution of matter in the optical regions of spiral galaxies.

What did Tully-Fisher discover about galaxy rotation in 1977?

The Tully–Fisher distance method (Tully & Fisher 1977) utilizes the measured relationship between galaxy rotation and luminosity. Galaxy rotation can be derived from the line-of-sight H i emission line width, and the resulting luminosity estimate combined with measured photometry is used to determine the distance.

#### What is the Tully Fisher relation quizlet?

What is the Tully-Fisher relation? It relates rotational speeds of galaxies as measured by the broadness of their emission lines to their luminosities.

What are the two methods that are best suited to determine the distance to a distant galaxy?

For more-distant galaxies, astronomers rely on the exploding stars known as supernovae. Like Cepheids, the rate at which a certain class of supernovae brighten and fade reveals their true brightness, which then can be used to calculate their distance.

## Which of these standard candles has been used to determine distances to the most distant galaxies?

The best standard candle for determining the distance to the nearby galaxies is the Cepheid variable star. These are bright and reasonably common, with strong identifying signatures, so their observation in other galaxies is not too difficult.

How do they measure distances to galaxies?

Astronomers can use what are called surface brightness fluctuations (SBF, for short), along with the color of a galaxy, to calculate how far away it is from earth. Most galaxies measured in this way are millions of light years away.

### How do we know the distance to galaxies?

How do we measure distances to galaxies?

To determine the distance to a galaxy one would only need to measure its apparent (angular) size, and use the small angle equation: a = s / d, where a is the measured angular size (in radians!), s is the galaxy’s true size (diameter), and d is the distance to the galaxy.

#### What method is used to determine the distances of very remote galaxies?

For very remote galaxies, astronomers use the observed redshift as a distance indicator; the longer the galaxy’s light has been travelling through expanding space, the more its light waves have been stretched to longer (redder) wavelengths.

What is the most accurate way to determine the distance to a nearby galaxy?

What is the most accurate way to determine the distance to a relatively nearby galaxy? It’s called “parallax“. Basically you look at how much the star appears to move in the sky as a result of the earth actually moving on its orbit aroun the sun the more the star seems to move the closer it is.

## Which technique was used to first determine the distances to nearby galaxies?

trigonometric parallax
The first scientist to do so was Friedrich Bessel in 1838. The method that is used to measure distances to nearby stars is called trigonometric parallax, or sometimes, triangulation.

How do we determine distance of galaxies?