RBSE+2008+Radio+and+Starburst

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Alexandra JW Echtenkamp, Andrew S. Bowles, Anthony J. Sinker Breck School, Minneapolis, MN //Teacher: Chelen H. Johnson, ARBSE 2007// Radio and starburst galaxies are not the same as other galaxies; their AGNs do not produce more radiation than the other galaxies. This group will focus on radio galaxies from Right Ascension 07h 18m to 09h 43m. They will first determine if the galaxy is radio or starburst with the emission lines. Then determine the distance, velocity, and the redshift as well as define the characteristics of radio and starburst galaxies.
 * Radio and Starburst Galaxies**
 * Summary by JJ.**
 * Abstract:**


 * Intro:**

Discovered in the 1940s, radio galaxies are commonly found in elliptical galaxies. The radio galaxies are jet structured meaning they have **jets**, **two lobes**, **counter jets**, **streams of electron-filled gas** aimed in different directions from a black hole at the center of a galaxy//,// and **hot spots.** Between the lobes is the host galaxy, which is connected by jets. Jets are very important because they trace the path of material that is ejected from the active galactic nucleus and into the lobes. One jet is brighter and the lighter jet is the counterjet. This structure makes the radio galaxies somewhat symmetrical//.//

A Double Radio Source Associated with a Galactic Nucleus (DRAGN) is a radio source that is produced by jets produced by active galactic nucleus that is not in the Milky Way. This happens when an accretion disk forms around a black hole and spins, converts gravitational and rotational energy into excess perpendicular to the disk. Although DRAGNs are found in starburst galaxies which also produce radio emission lines and are mainly formed in galaxies that are larger than their host galaxies, such as elliptical galaxies//;// they are comprised of lobes, jets, and a core just as other radio galaxies are as well as hot spots in the lobes.

There are two types of radio galaxies, Franaroff-Riley type I (FR I) and type II (FR II). While the two groups share similar properties such as their size; they have different UV and infrared properties, kinematics, and host galaxies.
 * Types:**

FR I are either old or they don’t have enough material or energy to form stars. While they can no longer form new material, they are the most evolved of the radio galaxies.

The FR II galaxies have higher redshifts but are less evolved; due to this they are richer groups, meaning that there are fewer things around the galaxy//.//

To understand exactly what is researched, the basic knowledge of radio and starburst galaxies must be understood.
 * How it’s formed:**

A radio galaxy is formed when an AGN produces two persistent, oppositely directed plasma outflows. The outflows are what will soon to become the jets of the galaxy. While it is not known exactly what is inside the jets, we know that they have fast moving electrons and magnetic fields, which make the high radio frequencies. The emission that occurs moves almost at the velocity of sound.

The jets are formed through the winding up of magnetic fields, which create a black hole in the nucleus of the galaxy. The winding of the black hole converts the energy from the magnetic field into mass. This initial winding is supersonic, meaning it is faster than the speed of sound//.// From the formation stage, the radio galaxy goes through the developmental stage.
 * Beginnings:**

In this stage the galaxy grows as the jets stretch from the atmosphere or the AGNs, through the interstellar medium of host galaxies, lower densities and pressures of the outer halo of the galaxy, inter-galactic medium in surrounding galaxies, and finally to the low-density intergalactic medium. This growth of the galaxy and stretch of the jets extend outward and usually end up being bigger than the originating galaxy. The smallest known are only a few tens of parsecs across, while the largest are known to be up to several megaparsecs. The average radio galaxy is usually typically hundreds of kiloparsecs across. This is about twice the size of the Milky Way galaxy. The average life span of a radio galaxy is 20 million years//.//
 * Development:**

Starburst galaxies, the other type of galaxy being studied, are thought to be formed by close encounters or collisions of other galaxies. These collisions send a shock wave throughout the galaxy; pushing giant clouds of dust and gas, making them collapse and form hundreds of massive stars. These massive stars use up their fuel very quickly causing supernovas, which create more collisions, thus creating more stars. Starbursts are the most luminous galaxies and are thousands of light years in diameter//.(8)//

The star formations within the galaxy that ends up creating most of the stars are known as ultra-luminous clusters. They are about 10-20 light-years across and can have luminosities up to 100 million times that of the Sun.

These clusters are the densest starforming environments known. The thing that sets starburst galaxies apart from the rest is their high, intense emission lines in the far-infrared. These lines are created by the ultraviolet that is emitted by the numerous hot stars being formed. These young stars are absorbed by the dust and remitted with higher wavelengths. These wavelengths rate second only to AGNs themselves//.(9)//

While we know that starbursts last much less than the age of the universe, it is very difficult to estimate their age because new clusters are always being formed. This creates the starbursts extreme luminosity making it hard to see the older parts of the galaxy//.(10)//

For this project, they looked at radio and starburst galaxies and then compared and contrasted them. They looked at the galaxies in the Right Ascension range of 07h 01m to 09h 59m in the //FIRST Bright Quasar Survey// at the Very Large Array with the optical spectra obtained with the Kitt Peak 2.1-meter telescope. When they recognized either a starburst or radio galaxy by its graph, they used the galaxy. Since each galaxy has its own graph (spectra graph), they were able to estimate whether the graph represented either a starburst or radio galaxy. They disregarded all the galaxies that were clearly not recognized as either radio or starburst galaxies. After amassing a reasonable amount of galaxies (about 70), they calculated the ratios between the prominent emission lines. Finding the ratio: divide the higher wavelength by the shorter one (knowing which element caused which for the emission line ratio). The ratio was then compared to the ones posted on the “AGN Spectroscopy” packet on page 20. When a ratio in the packet that matched the calculated ratio was found, they knew that the elements forming the posted ratio were the elements responsible for the two emission lines that made up their calculated ratio.
 * OBSERVATIONS AND DATA REDUCTION**

Based on the placement of [OIII], H α, and H β lines, we were able to differentiate between starburst and radio galaxies. Radio galaxies have a small [OIII] line before a large [OII] line. Starburst galaxies have a large [OII] line preceding a small [OIII] line. These facts helped to determine which galaxies appeared to be starburst or radio galaxies and then helped them to disregard the other galaxies.

They then found the redshift, distance and velocity (see the page calculations).

For all the galaxies that they observed, both radio and starburst, the relationship between velocity and distance was linear, which Hubble’s Law confirms. The vast majority of the galaxies we observed were of fairly low velocity. The galaxies of further distance/greater velocity seemed to be outliers in the data set (because Hubble’s Law only works for low-redshift objects).
 * ANALYSIS AND RESULTS**

Their comparison of sky location yielded less conclusive results in that the data seemed to be scattered somewhat randomly. One observable pattern was that the starburst galaxies were all concentrated in the right ascension range between 8 and 9, and the radio galaxies were all located between 7 and 10 (which really doesn’t differentiate the galaxies much). Generally speaking, however, there was a uniform lack of pattern among all observed galaxies. Nearly every galaxy we observed had a redshift between 0 and 1; the only exceptions were two radio galaxies in the 2-3 range and one starburst galaxy between 4 and 5.


 * Finishing comments**

As demonstrated by our results, radio galaxies and starbursts are similar in nearly all observable characteristics. While the elements responsible for their respective emission lines varied, the galaxies we observed had few other distinguishing characteristics.


 * My work:**

Obviously we did not have as many samples as the above group but from the 148 samples of spectra we had I managed to get 9 good spectra for radio galaxies and 5 for starburst galaxies and this is what I found.

Radio Galaxy Luminosity: 1: 26,200 2: 19,900 3: 100,000 -outlier 4: 38,600 5: 29,200 6: 40,400 7: 20,200 8: 29,100 9: 63,400

Starburst Galaxy Luminosity: 1: 6,490 2: 8,650 3: 7,100 4: 5,210 5: 1,060

Units are in candela

As one can see, the luminosity of the radio galaxies in the data set we had were at least a power of tenth higher than the starburst galaxies. From this I conclude (for now) that radio galaxies are more luminous than starburst galaxies even though other aspects seem similar.

This result is very weird because the article above said that the Starburst galaxies are the most luminous of the galaxies but the data we have says that Radio galaxies are more luminous. I don't know why it's different but I will find out here.
 * Speculation/question:**