The RBSE Journal 2008 - National Optical Astronomy ... · The RBSE Journal ii 2008 V2 The RBSE Journal 2008 The RBSE Journal is an annual on-line publication that presents the research

The 2008 RBSE

Journal

The RBSE Journal ii 2008 V2

The RBSE Journal 2008

The RBSE Journal is an annual on-line publication that presents the research of students and teachers who have participated in the Research Based Science Education program RBSE, at the National Optical Astronomy Observatory in Tucson. This program consists of a distance learning course and a summer workshop for high school teachers interested in incorporating research within their class and school. RBSE brings the research experience to the classroom with datasets, materials, support and mentors during the academic year. The journal publishes papers that make use of data from the RBSE program, or from its related programs: TOP, New Mexico Skies and the SPITZER teacher observing program. These papers represent a select set of those submitted for publication by students and occasionally RBSE teachers. All papers are reviewed both by the Editor and the Astronomer responsible for the particular research project. This year we wish to acknowledge editing help from other astronomers with special expertise in topics that are outside the RBSE projects. More information about both the RBSE and the TOP program can be found on our website, www.noao.edu/ education/arbse I want to thank Dr. Travis Rector, Dr. Greg Rudnick and Dr. Joel Parker for their generous help in reviewing these papers and working with the young scientists. Special thanks are due to Kathie Coil for her efficient editing of the final copy. Dr. Katy Garmany Editor, RBSE Journal

The RBSE Journal iii 2008 V2

Table of Contents

AGN Radio and Starbust Galaxies ................................................................................................................. 4 Alexandra JW Echtenkamp, Andrew S. Bowles, Anthony J. Sinker Breck School, Minneapolis, MN Teacher: Chelen H. Johnson, ARBSE 2007 MgII and CIII] in Active Galactic Nuclei...............................................................................................12 Sarah Johnson, Jeffrey Portu, Breanna Heilicher Breck School, Minneapolis, MN Teacher: Chelen H. Johnson, ARBSE 2007 Relative Velocities of CIV Winds as an Indicator of Black Hole Mass................................................19 Meghan Dorn Rush-Henrietta High School, Henrietta, NY Teacher: Jeffrey Paradis, ARBSE 2007 Population Distribution Analysis of the FIRST Bright Quasar Survey............................................. 24 Tanner Sagouspe and Students of the Astronomy Research Seminar Central Catholic High School, Modesto, CA Teacher: Christine Wilde, ARBSE 2007 Finding the CIV Wind in Active Galactic Nuclei................................................................................. 34 Teacher: Chelen H. Johnson, Breck School, Minneapolis, MN–ARBSE 2007 Teacher: Javier Melendez, Brophy College Prep School, Phoenix, AZ–ARBSE 2007 Teacher: Jeffrey Paradis, Rush Henrietta Senior High School, Rochester, NY–ARBSE 2007 Teacher: Thomas F. Sumrall, Forrest County AHS, Brooklyn, MS–ARBSE 2007 Teacher: Christine Wilde, Central Catholic High School, Modesto, CA–ABSE 2007 Teacher: Lynne F. Zielinski, Glenbrook North High School, Northbrook, IL–ARBSE 2007 Clusters NGC 2367: Its Age and Distance.......................................................................................................... 44 Caitlin S. Colley Sullivan South High School, Kingsport, TN Teacher: Thomas Rutherford, TLRBSE 2005 A Search for Exoplanets in NGC 957 ................................................................................................... 52 Bobby Adams, Rebecca Redmon, Veronica Buehrig Sullivan South High School, Kingsport, TN Teacher: Thomas Rutherford, TLRBSE 2005 Minor Planets The Short-term Variation of the Transneptunian Binary Objects (42355) Typhon and (90482) Orcus ........................................................................................................................................................68 Rebecca Jensen-Clem1 and Jacob Shenker International Community School, Kirkland, WA 2 Gunn High School, Palo Alto, CA Teacher: Don McCarthy, RBSE 1996-TLRBSE 2002

The RBSE Journal 4 2008 V2

Radio and Starburst Galaxies Alexandra JW Echtenkamp, Andrew S. Bowles, Anthony J. Sinker

Breck School, Minneapolis, MN Teacher: Chelen H. Johnson, ARBSE 2007

ABSTRACT Active Galactic Nuclei (AGNs) are compact regions in the center of a galaxy that can produce more radiation than the rest of the galaxy. However, in the case of radio and starburst galaxies, AGN do not produce more radiation than the rest of the galaxy. Many different types of AGN can be formed in many different types of galaxies.(1) The three strongest sources are radio galaxies, quasars, and blazars. The main focus of research will be radio galaxies from Right Ascension 07h 18m to 09h 43m as part of the FIRST Bright Quasar Survey at the Very Large Array with the optical spectra obtained with the Kitt Peak 2.1-meter telescope. The galaxies were discovered by the Faint Images of the Radio Sky at Twenty- centimeters using a radio telescope in New Mexico.(2) Research will consist of looking at all the different types of galaxies within a certain area. From there the focus will turn to all the identified radio galaxies and starburst galaxies. By looking at the elements and emission lines in the graphs we were able to determine which were radio and starburst, and which were not. From there we used the lines to calculate the redshifts, velocity, and distance. Then we compared and contrasted the characteristics of the radio galaxies to the characteristics of starburst galaxies. INTRODUCTION Radio galaxies are for the most part found in elliptical galaxies. They were discovered in the 1940s when radio telescopes were used to scan the sky.(3) 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(4), 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.(5) This structure makes the radio galaxies somewhat symmetrical.(6)


Figure 1. Parts of a Radio Galaxy.(4)

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 produce radio emission lines and are mainly formed in galaxies that are larger than their host galaxies, such as elliptical galaxies.(4) They are comprised of lobes, jets, and a core just as other radio galaxies are, and they also have 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 properties, infrared properties, kinematics, and host galaxies. 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.(7)

To understand exactly what is researched, the basic knowledge of radio and starburst galaxies must be understood. 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, they have fast moving electrons and magnetic fields, which make the high radio frequencies. The emission that occurs moves almost 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.(4) From the formation stage, the radio galaxy goes through the developmental stage. 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.(4)

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) Figure 2. A Starburst Galaxy.(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 star-forming 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) OBSERVATIONS AND DATA REDUCTION For our project, we looked at radio and starburst galaxies and then compared and contrasted them. We 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 we recognized either a starburst or radio galaxy by its graph, we used the galaxy. Since each galaxy has its own


graph, we were able to estimate whether the graph represented either a starburst or radio galaxy. We disregarded all the galaxies that were clearly not recognized as either radio or starburst galaxies. After amassing a reasonable amount of galaxies (about 70), we calculated the ratios between the prominent emission lines. To find these ratios we divided the higher wavelength by the shorter one. We had to find the ratios of all the emission lines in order to discover which elements were responsible for the emission lines. 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, we knew that the elements forming the posted ratio were the elements responsible for the two emission lines that made up our calculated ratio. Based on the placement of [OIII], Hα, and Hβ 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 us determine which galaxies appeared to be starburst or radio galaxies and then helped us disregard the other galaxies. After the elements responsible for the emission lines were found, redshifts were calculated. To find the redshifts, wavelengths for the elements that were commonly found in AGN were taken from a list also on page 20 of the “AGN Spectroscopy” packet. Then the wavelengths were plugged into a formula for redshifts and the redshift was found. The

formula for a redshift is 1+ z = λobsλrest

where λobs is the emission line that was found, λrest is

the wavelength associated with the elements responsible for the emission line and z is the redshift. Since there were more than two emission lines found in most of the AGN, more than one redshift was calculated for each AGN. In this case, the redshifts were averaged. These averaged values, or original values if there were only two emission lines found, were the redshifts used to calculate other characteristics of the galaxies, such as velocity

and distance. The formula for velocity is v = c (1+ z)2 −1

(1− z)2 +1where v is velocity, c is the

speed of light (3.0x105 km sec-1), and z is the redshift.

Distance is calculated by d = cz(1.+ 0.5z)H0(1+ z)

. In this equation d is the distance, c is the

speed of light, z is the redshift and Ho is Hubble’s constant (75km sec-1 Mpc-1). After all the calculations were made, radio galaxies and starburst galaxies were compared to one another. ANALYSIS AND RESULTS For all the galaxies that we 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. This is because Hubble’s Law only works for low-redshift objects. Our comparison of sky location yielded less conclusive results;


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. Generally speaking, however, there was a uniform lack of pattern among all observed galaxies. (Figure 4) 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. (Figure 3) Figure 3: Redshifts of AGN


Figure 4. Location of AGN.

Figure 5. Velocities and Redshifts of AGN.


Figure 6. Distances and Redshifts of AGN.

DISCUSSION 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. For future projects, more characteristics for galaxies could be calculated. For example, luminosity was not found in this project. When we put checked to see if our AGN were seen with an optical telescope using the SIMBAD website, none of them were found because nobody has studied the galaxies in this research project. It would be interesting to see if there is a difference between what we found and the optical telescope. We could also use the Sloan Digital Sky Survey/ Sky Server to enter in the galaxies that were studied. From there we could find the recognized galaxies and find further characteristics as shown by the information on the survey. Another thing we could do is compare and contrast other types of galaxies besides Radio and Starburst. We could look at Quasars, BL Lacs, and Elliptical galaxies and get a further understanding of how they function compared to the already analyzed Starburst and Radio galaxies.


REFERENCES NASA’s HEASARC: Education and Public Information. 6 April 2006. NASA. 2 December 2007. Rector, Travis and Wolpa, Brenda. “AGN Spectroscopy Nature’s Most Powerful ‘Monsters’” Teacher Leaders. The National Optical Astronomy Observatory. 4 April 2004:1-32. Newman, Phil. “Active Galaxies and Quasars.” NASA Goddard Space Flight Center. NASA. 6 October, 2006. 2 December 2007. Bridle Alan. “Double Radio Sources Associated with Galactic Nuclei”. NRAO Charlottesville. 28 June 2006. AstroWeb. 3 December 2007, Jones, Mark H., Lambourne, Robert J. An Introduction to Galaxies and Cosmology. Cambridge. “Radio Galaxies”. 11 February 2007. UT Astrophysics. Zirbel Esther. “The Megaparsec Environments of Radio Galaxies.” The Astrophysical Journal. 20 February 1997: 476:489-509 Starburst Galaxies. 29 August 2006. Chandra X-Ray Observatory. 13 December 2007. Starburst Galaxy. 2007. The Internet Encyclopedia of Science. 13 December 2007. Meurer, Gerhardt R. “Galaxy Evolution.” Extragalactic Astronomy. 2007. Johns Hopkins University. 13 December 2007. < http://www.pha.jhu.edu/~meurer/research.html> Smith Gene. “A Bestiary of Active Galaxies”. 29 September 200. University of California. 3 December 2007. Keel Bill. “Radio Structure in Radio Galaxies”. November 2002. Astr.edu. 3 December 2007. Longair M. “Three Radio Galaxies”. NASA. Students for the Exploration and Development of Space. 3 December 2007. Peratt A. L. 'The Evidence for Electrical Currents in Cosmic Plasma', , IEEE Trans. Plasma Sci., Vol.18, pp.26-32, 1990.


MgII and CIII] in Active Galactic Nuclei Sarah Johnson, Jeffrey Portu, Breanna Heilicher

Breck School, Minneapolis, MN Teacher: Chelen H. Johnson, ARBSE 2007

ABSTRACT This project was aimed at determining the velocity of two component chemicals, MgII and CIII], in the winds associated with active galactic nuclei (AGNs). We classified objects based on a thorough examination of spectra of AGNs in the region centered on 07 hours of Right Ascension. Focusing on the MgII and CIII] emission lines in the identified quasars, we were able to calculate the redshift, relative velocity, and distance of each element. We are confident that our MgII and CIII] lines are correctly identified: Earth’s atmosphere cannot produce CIII] or MgII lines, and our MgII lines were consistent through multiple checks, and were found at predictable wavelengths. Furthermore, since the lines are redshifted, there is no concern of them being misidentified. MgII has lost an outer electron shell, while CIII] has lost an inner electron which takes more energy to pull away. MgII is farther away from the black hole than CIII], thus it is colder and has a slower velocity. We assumed that the MgII velocity was the quasar’s velocity and the CIII] velocity was the velocity of the wind. The wind velocity was faster than the actual velocity of the quasar. Our research showed results in the quasars with MgII and CIII] lines that were similar throughout all of our data and demonstrated that there is an indirect relationship between distance from the central black hole and wind velocity. INTRODUCTION An Active Galactic Nucleus (AGN) is all of the matter that surrounds a supermassive black hole. These galactic giants of the Universe are mostly unknown. There are four different types of AGNs, each with different characteristics. Radio Galaxies are galaxies that appear as normal galaxies in the optical spectrum, but they emit massive amounts of radio waves (1). Starburst galaxies are known for forming stars at a very fast rate. Many times this is caused by a gravitational interaction with another galaxy. BL Lacertae objects are known for having very weak emission lines, unlike quasars or radio galaxies. Spiral galaxies are the oldest type of galaxy; they consist of about a hundred billion stars, which are formed in HII regions and have characteristic arms that spiral out of the center. For our study, we will disregard the spectra for radio, starburst and BL Lacertae objects and focus on quasars. Spectral emission lines can help to differentiate the different types of AGNs. Spectroscopy allows us to study what types of light we see from an object; it is arguably the most important aspect of astronomy. Through spectroscopy we can determine the temperature, velocity, and composition of the object being examined. In terms of velocity, spectroscopy can be used to determine an object’s velocity toward or away from us via the Doppler effect. Without spectroscopy, it would be very hard, if not impossible for astronomers to tell what all of the lights in the sky are.


Figure 1. Visible spectrum of Sky with spectroscopy. (1)

To find the shift of an object, the equation λobs = (1+ z)λrest is used, where λobsis the observed wavelength, and z is the redshift of the object. If z is positive, then there is a redshift, and if z is negative, a blueshift. A redshift is seen when the object is moving away from us in the Universe, and a blueshift is seen when something is moving toward us in the Universe. Galaxies that are very far away move much faster than those that are close to our galaxy. For nearby objects, Hubble’s Law, v = H0d , where v is the object’s velocity, H0 = 75 km/s/Mpc (the Hubble constant) and d is the distance, is used to determine the distance of an AGN. The objects in our study are so distant that a more advanced model, such as the “empty Universe” model needs to be used to calculate distance which is important because it provides a third dimension to something that we can only see in two dimensions. The winds that come off an AGN are crucial in determining the velocity of the AGN, and can be seen in Figure 2. There is some speculation of a connection between the winds, especially the CIII] and MgII. To find the velocity of that wind, the equation

v = c (1+ z)2 −1

(1+ z)2 +1 is used, where v is the velocity, and z is the redshift.


Figure 2. Diagram of a typical AGN. (2)

In our project, we examined AGNs specifically near Right Ascension 07 hours. The data we are using will be from the FIRST Bright Quasar Survey taken at the Very Large Array with the optical spectra obtained with the Kitt Peak 2.1-meter telescope. The FIRST Survey is an acronym for “Faint mages of the Radio Sky at Twenty-centimeters”. Through the analysis of the quasar’s MgII and CIII] emission lines, we determined the quasar’s velocity, as shown in Figure 2. By analyzing the winds and where they occur, we were able to see what direction the AGN is moving in and other characteristics of that region of the sky. The velocity relates to the distance from the continuum source. The difference in the velocities of the MgII and CIII] lines in the AGN spectrum indicate the velocity of the wind as the object is moving. MgII and CIII] lines don’t change based on high or low states of the spectrum, and both are fairly broad lines. In broad-line profiles, each velocity has a range of ionization, but there is a “preference for higher ionization at higher velocities” (4). Although MgII and CIII] are low-ionization and low-density atoms, CIII] is more highly ionized than MgII. High and low states of AGN cause ionization radii to expand or contract, and can be caused by changes in the continuum source radius or velocity. “Peaks in the emission-line profiles can be transient responses to variation of the continuum source. Averaging over time, there is equal flux from the blue and red sides of the profile, but the blue side is more likely to have a prominent narrow peak” (3). The terminal velocity of the wind is determined by the width of the emission lines and the ionization state. High ionization lines are produced from an outflowing wind, while low ionization lines


tend to come through a thick accretion disk. (3) Ionization increases as atomic radius increases and the electron shells expand, thus increasing the velocity. Near the source of the emission, there is strong absorption and minimal velocity; however, for electron shells with an increasing radius, the width of the emission lines increase and absorption becomes weaker. “Velocity offset is largest for ions with the highest ionization” (3) because there is more obscuration, which is directly related to velocity (2, 3). The quasars in our survey have a spectrum similar to that in Figure 3. (1) However, our spectra are not as clean as that shown due to the fact that it is a composite of over 100 quasars that have been averaged together. As illustrated, the CIII] and MgII lines stick out at distinct points and can be easily recognized. By determining the redshift or blueshift and its relation to the wind velocity of CIII] and MgII winds of some of the quasars in our region of the sky, we are hoping to be able to give more insight into the relatively unknown realm of AGNs. Figure 3. Typical Quasar Spectra. (1)

ANALYSIS AND RESULTS The purpose of our research was to determine how different elements, specifically MgII and CIII], and their distance from the black hole affects the velocity of their winds. Energy from the accretion disks around the black hole in the center of the galaxy heats up the dust and galaxy, and creating emission lines that, if the galaxy is near enough we can see. The farther away from the black hole, the more slowly the clouds and dust move, and the colder they are. The torus circles the accretion disk, and is cold enough to see infrared radiation, however, it is too thick to see through, and can obscure the view.


Table 1. Redshift, Velocity and Distance.

location MgII

redshift CIII]

redshift

MgII velocity (km/s)

CIII] Velocity (km/s)

Relative Velocity (km/s)

distance (Mpc)

Relative Distance

(Mpc) bq0713p3656 1.59 1.67 222160 226189 -4029 -8056938 8056938bq0719p3307 1.37 1.63 209323 224213 -14890 -29777326 29777326bq0721p2227 1.63 1.62 224213 223707 506 1013855 1013855bq0722p2856 1.21 1.51 198030 217809 -19779 -39556120 39556120bq0722p2941 1.2 1.79 197260 231695 -34434 -68866985 68866985bq0724p2517 1.23 1.45 199546 214316 -14770 -29538063 29538063bq0726p3019 1.29 1.05 203909 184671 19238 38478918 38478918bq0733p4555.2 1.18 1.04 195696 183757 11939 23879470 23879470bq0758p3222 1.2 1.21 197260 198030 -770 -1538019 1538019bq0803p2727 1.2 1.22 197260 198792 -1532 -3061959 3061959bq0809p4134 1.22 1.19 198792 196482 2310 4622273 4622273bq0810p5025 1.19 1.2 196482 197260 -778 -1554311 1554311bq0828p4922 1.53 1.49 218929 216668 2261 4523909 4523909bq0835p4826 1.37 1.4 209323 211243 -1920 -3837012 3837012bq0836p3455 1.39 1.46 210609 214913 -4304 -8605458 8605458bq0846p2502 1.41 1.44 211870 213714 -1844 -3686149 3686149

In the region of the sky around 07 hours of Right Ascension, we examined 231 AGNs, 24% of which were quasars (see Figure 4. Classification of AGN). However, we disregarded spectra of quasars that did not meet our requirements of distinct MgII and CIII] emission lines. We are confident that the CIII] lines are from AGNs because Earth will never produce CIII] emission lines. Of the 231 spectra, we were able to successfully analyze 16 (7%) of the spectra (see Figure 5. Classification of AGN with MgII and CIII] Lines). Of these quasars, seven of the 16 (44%) had relative velocities within -5000 km/s to -1 km/s (see Figure 6. Histogram of Relative Velocities). This means that the quasar’s wind is moving toward us at a relatively slow speed. Figure 4. Classification of Selected AGN.


Figure 5. Classification of AGN with Distinct MgII and CIII] Emission Lines.

Figure 6. Histogram of Relative Velocities.

DISCUSSION The ionization state of each atom affects its velocity and distance from the black hole. MgII, which is farther away from the black hole than CIII] has lost an outer shell electron. Because inner electrons take more energy to move, CIII] is a hotter gas, which


results in its higher velocity than the MgII (see Table 1. Redshift, Velocity and Distance). From the positive velocities of the MgII and CIII] lines, we can determine that both the MgII and CIII] emission lines were redshifted and are in the part of the galaxy that is moving away from us. MgII is farther away from the black hole than CIII], therefore it also has a slower velocity. Due to this difference in distance, we assumed that the CIII] velocity is the velocity of the gas, while the MgII is the quasar velocity because of its large distance from the black hole. Further projects could compare the MgII and CIII] lines with CIV emission lines, examining whether the CIV affects the MgII and CIII]. The difference between luminosity and distance could also be studied. REFERENCES Rector, Travis A. and Brenda A. Wolpa. “AGN Spectroscopy: Nature’s Most Powerful ‘Monsters.’” The National Optical Astronomy Observatory 4 April, 2004. Johnson, Chelen H. AGN Spectroscopy: Studying the Monsters of Astronomy. 2007. Hutchings, J.B., G.A. Kriss, R.F. Green, M. Brotherton, M.E. Kaiser, A.P. Koratkar, and W. Zheng. “Evidence for an Accelerating Wind as the Broad-Line Region in NGC 3516.” The Astrophysical Journal 559:173-180, 20 September 2001. Breck Upper School Lib. 3 Dec. 2007 . Tytler, David and Xiao-Ming Fan. “Systematic QSO Emission-Line Velocity Shifts and New Unbiased Redshifts.” The Astrophysical Journal 79:1-36, March 1992. Breck Upper School Lib. 3 Dec. 2007.


Relative Velocities of CIV Winds as an Indicator of Black Hole Mass Meghan Dorn.

Rush-Henrietta High School, Henrietta, NY Teacher: Jeffrey Paradis, ARBSE 2007

ABSTRACT Producing almost 1/5 of the energy in the universe, quasars are of great importance to astronomers (Elvis, 2003). I present spectra of 62 selected quasars and the relative velocities of particles around them, in or near the torus. Hypothesizing that differences between relative velocities of elements MgII and CIV are due to the individual size of the black hole, based on the evidence, I have concluded that this relationship does not exist. Further study is proposed based on multiple contributing factors within the structure of the quasar that may have implications on the relative velocities of particles. INTRODUCTION Active galaxies are energetic galaxies that emit thousands of times more energy per second than the Milky Way. Radiation emitted from the black hole in the center is mostly long-wavelength and non-thermal (Chaisson, 2005). The nucleus of an active galaxy produces more radiation than the rest of the galaxy and is solely gravitationally driven. Their observed redshifts indicate extremely large distances from Earth. Discovered in 1963, the currently accepted model is an accretion disk surrounding a super massive black hole (SMBH). These SMBHs are millions or billions of times more massive than our Sun. In addition, the luminosity of a quasar is billions of times that of the Sun, often on the magnitude of 10^38 to 10^42 Watts1. When magnetic field lines, which are produced by the rotation of the accretion disk, interact with the accretion disk itself, they release energy that powers the jets that emerge from the center of the quasar. The jets are perpendicular to the plane of the accretion disk feeding the SMBH and contain gamma rays and x-rays. The radiation emitted is electromagnetic and mostly in the form of synchrotron radiation. ANALYSIS AND RESULTS My data consists of 62 quasars that are from a database of 1300 galactic spectra taken from the VLA FIRST Survey (Faint Images of the Radio Sky at Twenty-Centimeters). This data was obtained from Dr. Travis Rector of the 1 The Sun’s luminosity is just 3.8x10^26W. University of Alaska. The selection consists of quasars that exhibit carbon IV (CIV), carbon III (CIII), and magnesium II (MgII) emission lines. The chosen emission lines are broad and not difficult to pick out of the spectra. By using a small redshift value, these two elements were easier to pick out in lower redshifted galaxies. I intended to look at interactions of energy emitted from the quasar jets, with dust in their path. Focusing on the redshifts of these emission lines, I determined the relative velocity of the CIV line in relation to the MgII. The significance of the relative velocity is to show the direction of the movement of the particles being compared. This does not indicate the shift of the


entire galaxy, which is no doubt redshifted, but rather the cone of particles interacting with the jets that are visible. Relative motion of the excited particles could be toward the observer or away, indicating a blue or red shift. The equation for the redshift of each emission line is as follows, where z is redshift and lambda means the wavelength. Large differences in redshifts were ignored due to possible observational error. Values outside of what is generally expected for these velocities suggest that the measured or calculated values are inaccurate. A typical quasar spectrum is shown in figure 1.

Observed redshift is due to the Doppler Effect which occurs when an object is moving away from the observer. Using the following equation, the difference in redshift (zMgII-zCIII) of each of the two emission lines calculated the relative velocity of those particles. This was repeated for each of the quasars, producing a large range of velocities. Z is the value of the redshifts and c, the speed of light, is a constant (c= 3x105 km s-1). Of all the galactic spectra on file, the 62 quasars selected, all of them were chosen because they exhibited a similar redshift between the CIII and MgII lines, but the CIV was slightly askew, resulting in the relative velocity. The quasars needed to have visible emission lines on the spectra, or there would be nothing to measure. After most spectra was rejected for this investigation, spectra that had an unusually large difference in relative velocities were also taken out of the selection. See appendix A for data.

1)1(1)1(

2

2

++−+

=zzcv

rest

obszλλ

=+1


Figure 1

Source: Rector, Travis A. and Brenda A. Wolpa. “AGN Spectroscopy: Natures Most Powerful ‘Monsters’” ARBSE, 1-31 DISCUSSION To explain this large range, I hypothesized that a quasar having a larger black hole would have a higher velocity of gas and dust moving away from its jets. From the FIRST Survey, I retrieved cutouts2 of each quasar that gave me the radio brightness of whichever particular quasar in mJy/beam.3 That data could then be translated into luminosity using the inverse square law:

The luminosity was then plotted against ( figure 2) the relative velocity to see if there was any correlation. From Appendix A, the log of the luminosity and relative velocity was taken in order to scale the data.

24 dLBπ

=


Figure 2

Based on the graph no correlation was found whatsoever between the relative velocity and the black hole, but there is still promising work to be done. The theory of the Eddington limit proposes that when there is radiation being emitted such as in a jet from a quasar, there is an outward force of luminosity in addition to the gravity pulling inward (Heinzeller and Duschl, 2007). Luminosity of quasars would not only be dependent on 2 A cutout is a picture and known information about that particular quasar. 3 These units are millijanskies which are a unit of the flux. the size of the black hole but also the amount of matter being accreted onto it. My hypothesis did not take into account how much matter was being accreted onto the black holes in question, only on the size itself. A smaller black hole could exhibit higher velocities and greater luminosity if more were being accreted onto it based on the density of the material near the black hole. It would be sensible that a large black hole would produce greater velocities, but if the case were such that it had a small amount of matter being accreted onto that larger black hole, it would not. With two variables, the relation of the size of the black hole to the relative velocity of the quasar would be very loose if the second variable was not also taken into account. A problem that occurred with my data was that some of the relative velocities of the quasars appeared to be blueshifted, but there is no evidence yet discovered that blueshift has been observed in a quasar. This is true, due to the fact that the universe is expanding and all quasars would be moving away from us, but of the 62 selected quasars, those that show a positive relative velocity indicate a slightly lower redshift in CIV compared to the CIII and MgII. I propose that we are not viewing a blueshift in the quasar itself, but it is a possibility that the particle with the lower redshift than the other, producing a small difference in those redshifts, is moving towards us in the jet that is in our line of sight. This is indicative that gas from the quasar is moving toward us, rather than the quasar itself.

Luminosity vs Relative Velocity

133

134

135

136

137

138

139

140

141

0 2 4 6 8 10 12Relative Velocity


An explanation for the negative and positive velocities would be the location of the particles that are interacting with energy from the quasar. If a particle were to be closer to the jets, it stands to reason that it would be moving faster than a particle farther away from the jet. Those particles moving faster would appear to have a larger redshift. So, when the redshifts subtracted and the relative velocity determined to be positive, if the particles were in another case in opposite locations, the difference would cause the relative velocity to be negative, but quasars are a point source so it would be near impossible to see which regions individual particles would be in. A more acceptable conclusion would be that the viewer was seeing redshifted particles on one side of the quasar moving away from us, but the particle that appeared less redshifted would be on the other side, interacting with the jet that is moving towards us, while the quasar was, overall, moving away. SUMMARY AND ACKNOWLEDGEMENTS-- My hypothesis that a larger flux would produce a higher relative velocity was proven to be inaccurate, but there is still promising work to be done. Further ideas to explore would be to measure the impact of the shape and angle of the jets, luminosity, and amount of matter accreting onto the black hole all as variables that determine the velocities of the matter around the jets. Martin Elvis of the Harvard-Smithsonian Center for Astrophysics has begun to address the impact of the shape of the cone created by the magnetic field lines interacting with the energy from the quasar in his article A Structure for Quasars, 2000. He proposes that the viewing angle dictates the range of velocities that is seen within that particular quasar. The range of velocities seen within my selection may not be closely related to the size of the black hole, but may in fact have more to do the structure and geometry of the jets. This is along the lines of what Elvis is proposing in his article- that the viewing angle of the quasar will most likely indicate the range of redshifts and therefore velocities seen. One may go further from the Eddington limit and say that the amount of matter being accreted onto the black hole in the center of the quasar and the size of that black hole are only factors that determine the angle of the cones of energy (jets) which would be an important contributing variable as to the input of what creates the velocities seen. REFERENCES— Chaisson, Eric and Steve McMillan. Astronomy Today. New Jersey: Pearson Education, Inc., 2005 D. Heinzeller and W. J. Duschl. “On the Eddington Limit in Accretion Discs” Monthly Notices of the Royal Astronomical Society 374 (3), 1146–1154, January 2007 Elvis, Martin. “A Structure for Quasars” The Astrophysical Journal, 545: 63-76, 2000 December 10


Elvis, Martin. “Solving Quasars” PowerPoint available online from Fermilab Colloqium 29 October 2003 Rector, Travis. AGN Spectroscopy: Studying Natures Most Powerful “Monsters.” RBSE Journal: Tucson, Arizona, 1999


Population Distribution Analysis of the FIRST Bright Quasar Survey Tanner Sagouspe and Students of the Astronomy Research Seminar

Central Catholic High School, Modesto, CA Teacher: Christine Wilde, ARBSE 2007

ABSTRACT The students in the Astronomy Research Seminar at Central Catholic High School have been working to identify the population of objects in the Bright Quasar Survey. We were given 560 objects to examine; Mrs. Wilde split the class into five main groups that eventually separated into approximately two groups per primary group. Using Graphical Analysis on the school computers we worked diligently for three months in opening assigned columns of Bright Quasar Objects and working together to uncover which category the object fell under: BL Lac, elliptical galaxy, quasar, radio galaxy, or starburst. After completing our study of the objects we found that quasars were the most abundant objects in the night sky with 57%, followed by radio galaxies with 17%, elliptical galaxies with 13%, starbursts with 8%, and finally with the least, BL Lac objects with a minuet percentage of 5%. Upon completion of the study we also created a catalog in which all of the objects studied are listed and placed under their appropriate category.

INTRODUCTION Our research question entailed examining the given data and accumulating the number of various Bright Quasar Objects given in the FIRST Bright Quasar Survey. We hoped to catalog approximately the first 40 lines of objects, which were 560 objects, and properly categorize them into the previously given list of possible objects: BL Lac, elliptical galaxy, quasar, radio galaxy, or starburst. Upon finishing the designated work we intended to find out what percentage of the night time sky was filled with said amount of objects. Discussing further into the objects we are able to see the precise differences in the Bright Quasar Objects. A BL Lac is an active galaxy whose jets are pointed at the Earth and is in fact one of the two branches of blazar type galaxies. The elliptical galaxies are one of the three main types of galaxies and are easily characterized by their elliptical shape. A quasar is an active galaxy in which its jets are not pointed at Earth like a BL Lac, but in a different direction so they are able to be seen in their entirety. Starburst galaxies are galaxies in which there are abnormally large numbers of star births occurring at a given time. They are determined to be starburst galaxies based on the star formation inside the galaxy in relation to its relative age compared to that of an average galaxy. Radio galaxies are galaxies that emit large amounts of radio waves from the area around the super massive black holes at their center.

OBSERVATION AND DATA REDUCTION The study of the Bright Quasar Objects began once we received the data we were chosen to examine. Opening the graphs with Graphical Analysis on school computers we began by splitting into our assigned groups and assigned computers where we would begin the study. When working in our groups we began to notice trends in comparing as far as


numbers in certain objects. Our groups, after running through multiple lines of data, noticed the common reoccurrence of quasars in the night sky. It was nearly impossible to go through a set of objects, 15 objects total, without coming across at least three or four quasars. After all of our calculations were completed we came up with some astonishing results. Our prior hypothesis was correct in which we presumed that quasars were going to take up a great portion of the night time sky with an astounding 57%. The rest of the sky was filled with loosely distributed objects, as shown in Chart 1 in the Analysis and Results section, with the most being radio galaxies with a 17%, elliptical galaxies 13%, starbursts 8%, and BL Lacs at 5%.

ANALYSIS AND RESULTS

Quasar Radio Elliptical BL LAC Starburst 119.0131 729.3046 306.0044 721.2928 926.3453509.4139 758.392 748.3709 749.3556 0004p0051

750.413 824.3342 754.3937 807.3043 0013p000.01 751.2919 924.3415 820.3459 0050m0929 00181m1022.2754.2941 929.3757 821.3107 0051p0126 0028p0055

807.3043 930.3439 932.3537 0127m0151.4 0031m0136 809.2912 933.2845 938.3051 0135m0019 0038p0010.01 809.4139 936.3021 951.3614 0149p0017 0039m1111

900.3646 943.3614 1001.3052 0204m0528 0043m0925 910.3759 954.3809 1038.391 0208m0502 0043m1035 915.2933 956.362 1041.3718 0304m0054.6 0113p0116

932.284 1002.3453 0012p0041 0737p2942 0125m0018 934.3542 1005.3414 0019m0104 0742p2318.4 0138m0002.01

942.401 0012p0125 001m0020 0746p3926.tot 0201p0134 943.2938 0058m1114 001m0041 0803p2437 0207m0686

953.3225 0059m0215.01 0035m1019 0820p3640 0212m0030 953.3917 0100m0200 0041m1108 0824p3916.tot 0220m0134 955.3335 0113p0116 0043m0026 0854p2223 0232p0040

958.3224 0125m0044 0105m0033_2 0854p4408.3 0234m0124_A 1025.4012 0128m0033 0120m0832 0910p3329 0247p0023 1033.3555 0135m0213.01 0203m0900 1012p4229 0249m0828

1106.3051 0142m0029 0215m0528 1024p2332 0711p3015 46130104 0151m0634 0228p0130 1038p4227 0712p3627 0000m1021 0151m0932 0243p0046 1043p2408 0714p5343_A 0002m0004.2 0200m085 0303p0024 1052p2405 0718p4435 0002p0021.2 0203m0242 042p2400 1058p5443 0724p3755 0004p0000.2 0218m0033 0702p5643.2 1100p4019 0738p2504 0005m1010 0225m0743 0703p4436 1101p3229 0758p3647 0007p0053 0245p0108 0703p4443 1109p2411 0759.3150.01 0011p0122.tot 0246m0642 0704p4439_A 0809p3445 0012m0131 0247p0023 0704p448 0831p3942 0012m1022 0249m0828 0704p5438 0834p1557 0014m0107 0256p0039 0709p4836 0835p2435.01 0014m091812_2 0317m0054 0712p5327 0845p5519 0014p0039 0319p0005.01 0714p3536 0849p4028


0015m008_2 0716p4654 0716p4654 0850p2912 0019m0839 0721p4329.2 0717p5653.2 0858p1701 0027m0837 0723p3359 0723p3731 0939p2720 0029p0105 0730p2752 0724p2830 1020p3306 002m1039.01 0734p4729 0726p4706 1022p2321 0031m0011 0736p3926 0726p5726 1031p2847 0034m0054_a 0739p5152 0727p4816.2 1045p0843 0034p0118 0739p5323 0730p5619 1048p2603 0035m1019 0741p2621 0737p2846 1057p4037 0040m146AA 0745p3557 0737p5215 0047m093_2 0747p4838 0746p3308 004m0906 0748p334 0747p5730 0051p0041_2 0749p4152 0748p4550 0055m1019 0755p1447 0748p4930.tot 0057m0932.01 0801p2608 0754p3102 0059p0006 0802p3940 0754p4316_a 0100m0055 0804p3833 0757p306 01013p2212 0804p3853 0800p4639 0102m0853.01 0805p4714 0801p5045 0102m0921 0805p4810 0805p0627 0103m0024 0817p22423 0822p4711 0106m1034.01 0818p4635 0832p2233.01 0109m0928 0823p2448 0848p2804.01 0113m0852 0823p2852 0853p4754.3 0113m1014 0825p2340 0854p2811.01 0114m0008 0829p2225.01 0854p2811.6 0118m0854 0834p2221 0858p1446 0122m0032_A 0850p3039.2 08822p4711 0122m0935 0857p3313.2_A 0900p4215.2 0125m0005 0900p4215.2 0900p4215.3 0125m0018 0900p4215.3 0908p0726 0128m1032 0902p3957 0915p1716 0129m0054 0903p224.2 0924p0019 0129m0829 0903p2241.2 0942p2400 0129m0914 0903p2447 0959p2759 0130m0135 0913p2447 1020m0152 0130m1019 0914p3059 1039p3133 0130m1046 0932p0055 1055p3124 0131m0841 0933p2222 1055p3929 0132p0026 0933p2456 1103p3715 0134m0133 0934m0151 0135m0213.2 0937p2314.01 0137m0049 0941p3819 0137m0211 1018p3436 0140m0112 1026p3036 0140m0138 1035p3946 0141m0024 1038p2331 0151m0028 1038p3921 0152m0129 1039p4048m1 0155p0115 1102p2239


0158m0859 1102p3802 02002p0125 1103p3755 0200m0534 1104p3424 0200m085 1106p3539 0200m377 2 1106p4006 0201p0134 1109p4042 0202m0302 1109p4233 0203m0242 937p2314.01 0203m0900 0204m0528 0204m0528_a 0204m0721 0210m01015 0210m0517 0212m0100 0216m0444 0218m0605 0219m0737_A 0221p0101 0230m0007 0232m0910_A 0233m0012_A 0236m0121.2 0238m0001 0238m0831 0238p0123_A 0239m0709 0242m0157 0245p0108 0249m0834 0250m0852 0250p0002 0254p4408.3 0256m0119.2 0257p0005 0301p0115.2 0301p0118 0311p0056 0314p0117 0316p0137.2 036m0932 05210p011812 059m0137 0658p5413 0702p4556_A 0705p5448_A 0707p4756 0708p55032 0713p3656 0713p3820


0717p2937 0719p3307 0721p2227 0721p2726 0721p505.2 0721p5241 0722p2856 0722p2941 0722p4558 0723p2859 0724p2517 0724p4159 0725p2429 0725p2819 0726p3019 0726p4010 0726p5037.2 0727p3831 0727p5132 0728p2341.tot 0733p2721 0733p4555.2 0733p5301 0734p2504 0735p2837 0738p2127_A 0739p3043.4 0740p2537 0741p3111 0743p2712 0744.2920.1 0744p2959.4 0744p3208 0744p5149 0745p2614 0745p3142 0745p4734 0748p2200 0748p3006 0749p4510 0752p2017 0758p2624 0758p3222 0800p5010 0803p2727 0804p2722 0805p1529 0806p5041 0807p5117 0809p2753.3


0809p3122 0809p4139_2 0809p4723 0810p2321.01 0818p2814 0818p3834 0820p2353 0820p2355 0820p2905 0821p3443_2 0823p2852 0823p4104 0824p4057 0824p5552 0827p3336 0827p5333 0828p4922 082p3134 0830p2708 0830p3213.4 0831p1434 0831p2901 0832p3402 0832p3707 0833p2607 0833p3839 0833p5124 0834p3448 0835p2459 0835p4352 0835p4826 0836p3455 0836p4426 0837p2508 0844p4124 0846p0441 0846p2502 0846p3448 0847p3831 0849.3002.1 0849p2615 0852p4650.3 0857p3313.2_a2 0901p4848 0902p3957 0903p2241.2 0905p2849.2 0907p5515.2 0909p3024 0910p2612


0912m0231 0913m0042_A 0917m0000 0918p2325 0919p2914 0922p2236 0924p3547 0929p0041 0934p2902 0934p3153.01 0934p3153.2 0935m0108 0937p3615 0938p2308 0944p2331 0949m0305 0951p2635 0951p2635.01 0952p2240 0952p2352 0952p5048 0956p5152 0957m0253 0957p2356.2 1004p2225 1004p2422 1005p4332 1006p2701 1007m0208 1009p0529 1010.3003.1 1010.4132.01 1012p3309 1013p2449.2 1017p3242 101gm0318 1020p1432 1021p3437 1022p3041.01 1022p3931.01 1025p1551 1030.3102.01 1030p2555 1031p3953.2 1032p3738 1035p3232 1035p3510 1036p3703 1038p3729 1042p3811


1044p3656.4 1045p2717 1045p3440 1045p5251 1046p3427 1047p3606 1048p2222 1048p2906 1048p3026 1048p3129 1048p3531 1054p2536.6 1054p2636 1054p2703 1054p3855 1054p4152 1055p2949 1056p3166 1056p3704 1056p5019 1058p3136 1059p4051 1100p2303 1100p2314 1100p2314 1103p3729 1105p3614 1105p5320 1107p3206 1108p2555 1108p3133 1109p2038 904p8233 935p2308

Recorded FIRST Bright Quasar Survey Objects List

BL Lac Elliptical Galaxy

Quasar Radio Galaxy Starburst Total

29 75 319 93 44 560 FIRST Bright Quasar Survey Objects List Total


050

100150200250300350

BL Lac Quasar Starburst

Chart 1

Once the groups completed their work we compiled our various objects into individual Excel spreadsheets which were later converged into a single sheet. The end results showed that an overwhelming amount of quasars dominate the night time sky, tripling the number of the second closest object, radio galaxies. The BL Lac objects covered the least amount of the sky studied with only 29 recorded out of the total 560 objects. DISCUSSION In our investigation of the night time sky we found that a trend did not exist among the star placement of the different Bright Quasar Objects. Though quasars were spaced throughout the entire section of researched data there wasn’t any specific relation between the assigned columns. Our research found that the numbers of quasars, as well as other objects, varied from column to column. This was seen after each group compiled their work for individual sections of objects and saw that some columns contained as many as eight quasars, the next set of objects carried only five or six quasars. SUMMARY AND ACKNOWLEDGEMENTS We concluded that, though not consistently and equally distributed, quasars take up a large portion of the night time sky. We feel this is because of the time it takes for light to travel from the object to Earth has such a delay that we are in fact seeing galaxies from an earlier time that seem to still be feeding on adjacent stars because they appear to still be young. There were less BL Lac objects due to the fact that the chance of an AGN to be pointed directly at Earth so that its jets hit it is slim compared to having the jets facing anywhere else. I would like to acknowledge the entire Astronomy Research Seminar class for their assistance in examining and labeling the objects they were assigned: Roman Acosta, Gabriel Baduini, Mary Endsley, Zachary Fanelli, Tyler Fountain, Maya Grunder, Patrick


Hale, Ryan Hansberry, Nicollette Laroco, Anthony Luis, Ashley Mason, Joseph Mayol, David Misslbeck, Tyler Padilla, Teddy Pedrozo, Sarah Phillips, Brandon Reno, Caleigh Smith, Kayla Torres, Jacklyn Trejo, Jacob Wik, and Ethan Wiseman. The entire class would like to acknowledge Mrs. Christine Wilde for her assistance throughout the research and her insight that proved helpful when it was required.


Finding the CIV Wind in Active Galactic Nuclei Teacher: Chelen H. Johnson, Breck School, Minneapolis, MN–ARBSE 2007

Teacher: Javier Melendez, Brophy College Prep School, Phoenix, AZ–ARBSE 2007 Teacher: Jeffrey Paradis, Rush Henrietta Senior High School, Rochester, NY–ARBSE 2007

Teacher:Thomas F. Sumrall, Forrest County AHS, Brooklyn, MS–ARBSE 2007 Teacher: Christine Wilde, Central Catholic High School, Modesto, CA–ABSE 2007

Teacher: Lynne F. Zielinski, Glenbrook North High School, Northbrook, IL–ARBSE 2007 ABSTRACT The focus of this study was to classify quasars that had a blue or redshifted CIV spectral emission line that was different from usual redshifted spectrum of the quasar. Such a Doppler shifted emission line in a quasar might be the consequence of a CIV wind emanating from the accretion disk of active galaxies. The ability to determine the existence of a CIV wind requires a comparison of the CIV spectral emission line with the CIII] and MgII emission lines. This paper reveals the fraction of quasars that exhibit this CIV wind and attempts to determine the rate of motion. Comparative distances and distribution of these quasars were also studied to see if any other relationships could be found. INTRODUCTION AND BACKGROUND Active Galactic Nuclei (AGN) are the source of energy and are considered to be the hot nuclei within some bright galaxies. Standard features of AGN include a central supermassive black hole, plasma jets that stream out high energy material, an accretion disk feeding the black hole, an obscuring torus of thick matter, and broad and narrow line regions considered to be nebular-style material. From a close examination of spectra, scientists can determine the characteristics associated with each AGN type. The term ‘AGN’ encompasses many different types of very bright galaxies. Typically, AGN are believed to be present in objects that include starburst galaxies, radio galaxies, quasars, and BL Lacertae (BL Lac) objects. The best way to distinguish between and identify AGN types is through the spectral comparison of AGN candidate galaxies to normal galaxies, such as elliptical galaxies. Part of this team’s objective was to do such a comparison. In addition to identifying galaxy types, the team focused on identifying candidate quasar spectra that showed a set of uniquely blue or redshifted spectral lines. In order to make the appropriate comparisons, a set of baseline spectra needed to be chosen. Normal elliptical galaxy spectral light is believed to come from stars and from nebulae where stars are being formed within the galaxy. Comparatively, AGN have a specific set of spectral characteristics that identifies them in a manner similar to the way human fingerprints exhibit unique patterns. Examples can be found in the AGN documentation on the RBSE website. These sample spectra were used in this study to find candidate quasars that might contain the unique spectral lines needed to complete this investigation.


AGN are commonly associated with quasars. Relative to normal galaxies, quasar spectra are redshifted according to Hubble’s Law due to the cosmological expansion of the Universe. This team’s first goal was to identify a set of objects whose spectra resembled that of a typical quasar. In this study, the data were part of the FIRST Bright Quasar Survey, taken at a wavelength of 20 centimeters at the Very Large Array and contains over 1300 spectra. This team created the flow chart shown in Figure 1 to help characterize and identify each of the FIRST Bright Object Survey candidate spectra. The flow chart breaks down the specific spectroscopic characteristics that were needed to find the redshifted quasars needed for this team’s project goal. Figure 1. Flow Chart for Classification of AGN.

From the redshifted quasars identified, the team looked for specific spectral line identifiers. Of particular interest were the CIV, CIII], & MgII emission lines, believed to be indicators of hot gases. All lines can be redshifted in spectra, but when the gas is heated, it may move in a different direction, causing a blueshift. Some quasars show a CIV emission line that is shifted differentially relative to the normal redshift of the CIII] and MgII emission lines. These CIV emission lines are blueshifted.


CIV winds

The unusual blueshift in the CIV emission line may be caused by a wind from the AGN’s accretion disk due to the moving gas inside the quasar. Because the CIV emission line is blueshifted, the resultant wind producing it is nicknamed the “CIV wind”. Figure 2 shows a representation of the probably location of the CIV wind relative to the rest of the AGN. It is purported that high-energy particles, such as ultraviolet and/or x-rays, may be the cause of the heating in AGN broad line regions, and hence, the cause of the blueshifted CIV wind. Figure 2, CIV Wind Location on AGN Model. (original image from Max-Planck Institute of Extraterrestrial Physics.)

In a manner similar to the direction of the plasma jets emanating perpendicularly from the black hole in the accretion disk, the CIV wind also emanates outward from the accretion disk in a perpendicular direction. However, the cone of the CIV wind is believed to be wider than the plasma jets. This leads to the research goal for this project, which was two-fold. The first goal was to determine the fraction of quasars that exhibit the CIV blueshift. The second goal was to determine the rate at which the CIV wind is moving.

Observations and Data Reduction This investigation used the data acquired from the FIRST Bright Quasar Survey, containing approximately 1300 bright objects. The approach taken to achieve the research goal began by classifying the AGN in the FIRST Bright Quasar Survey using the flow chart (see Figure 1) created by the team. Once identified, the quasar candidates were studied to locate the MgII, CIII], and CIV emission lines. A typical quasar spectrum exhibiting the CIV blueshift is shown in Figure 3. Note the locations of the MgII, CIII], and CIV emission lines on the figure.


CIV

CIII]

MgII

Figure 3. Sample Spectra of Desired Quasar. Once the candidate quasar spectra were identified, the redshift of the CIV and MgII emission lines were calculated using the formula:

z +1= λobsλrest

, where z represents the redshift and λobs represents the observed wavelength, and λrest

rest wavelength. The motion of the CIV wind was measured and determined using the following

velocity equation: v = c (1+ z)2 −1

(1+ z)2 +1, where v represents the velocity, z represents the redshift and c

represents the speed of light Together, these equations allowed the team to determine the fraction of quasars that exhibit the CIV blueshift and the rate at which the CIV wind is moving. ANALYSIS OF RESULTS AND DISCUSSION Of the 1300 objects available in the FIRST Bright Quasar Survey, the team sampled 519 spectra. After much discussion, the team classified 275 AGN. Also during this time frame, the flow chart system for classification was developed. As a result, the team would recommend that anyone attempting to classify similar data should first create a flow chart for AGN classification and then document the classification of every object studied. Another recommendation is that a very systematic method of recording data is required for this type of study since AGN are difficult to classify. Of the 275 objects classified, 134 quasars were identified; this represents 49% of the objects classified. In comparison, 15% were classified as BL Lac objects, 14% were classified as elliptical galaxies, 12% were classified as starburst galaxies, and 10% were classified as radio galaxies. Figure 4 shows a pie chart depicting the percentage of each AGN object class. Figure 4. Distribution of AGN Objects.


Distribution of AGN Objects

(N = 275)

Quasar49%

BL Lac15%

Radio galaxies10%

Elliptical galaxies14%

Starburst galaxies

12%

Of the 134 quasars classified, 33 fit the team’s profile for quasars containing detectable CIV, CIII], and MgII emission lines, as well as having the desired blueshift type. This represents 24.6%, nearly one-fourth of the quasars investigated, fit the profile. Another interesting observation was that approximately half of the quasars exhibiting the CIV wind were redshifted at 48.5%, and half were blueshifted, at 51.5%. In approximately 3% of the total quasars, neither a redshift nor a blueshift were detected. A possible explanation for this could be the orientation of the object relative to Earth. In a wide cone, or funnel, the perspective of the observer could dictate the redshift. All quasars are moving away from us so the blueshift must be accounted for by a property of the quasar. After identifying the CIV wind velocity, the relative velocities were calculated. Relative velocity, in this case, is defined vCIV – vMgII. Figure 5 shows a bar chart graphing the number of quasars redshifted and blueshifted relative to a range of speeds. The result was that an average relative velocity for redshifted quasars was –1109 km/s and the average relative velocity for blueshifted quasars was +581 km/s. The graph clearly illustrated that the majority of the nearby CIV wind Doppler shifted quasars lay between –500 km/s and +1000 km/s. Figure 5. Relative Velocity of CIV Wind in Quasars.


Relative Velocities of CIV Wind

02468

1012

-5000

to -4

500

-4499

to -4

000

-3999

to -3

500

-3499

to -3

000

-2999

to -2

500

-2499

to -2

000

-1999

to -1

500

-1499

to -1

000

-999 t

o -50

0

-499 t

o 0

1 to 5

00

501 t

o 100

0

1000

to 15

00

1501

to 20

00

2001

to 25

00

relative velocities (km/s)

Blueshift

Redshift

The results for the relative velocities led the team to question the values. In theory, if the accretion disk heats the gases creating the CIV wind, then both redshifted and blueshifted CIV winds should be expected. However, due to the orientation of the quasar relative to Earth, the redshifted CIV emission lines were expected to be obscured by the torus. The large velocity range of the CIV cone could indicate that some CIV wind cones are wider or narrower depending on the speed of the hot gases emanating from the accretion disk. Considering the presence of both blueshifted and redshifted CIV lines, it seems plausible that the observed quasars show both the near and far side of the jets emanating from the accretion disk. The redshifted lines would represent jets on the far side of the quasar, and, similarly, the blue on the near side. The small blueshift we observed could be accommodated by the true redshift of the AGN, and the orientation of the jet toward Earth. Generally, the accretion disk and the torus are considered to be optically thick and would create the tendency to see only the blueshifted component.

Another possibility to explain the blueshift could be due to a wider angle of the cone and the position of the observer. Elvis suggests that the cone, or funnel-shaped outflow, is critical to the observer. The differences between higher and lower angles relative to the accretion disk dictate the strength of the narrow absorption line (NAL) regions, broad absorption line (BAL) regions and what he calls, embedded broad emission line regions (BELR). These differences in perspective may provide the range of velocities and redshift to accommodate our observations. According to Leighly and Moore, “These profiles are most simply explained if the high-ionization gas is accelerated toward us in a wind, while the low-ionization gas is emitted on the surface of the accretion disk or in the low-velocity base of the wind.” This would accommodate large differences in velocity, and again, depending on perspective, type of shift. This discussion led to other questions, which should be considered for further study:


- How would position angle and orientation of AGN affect the percentage of CIV wind detected?

- Do other quasar surveys yield similar results? - Using high-energy data (e.g., Chandra) can the intrinsic velocities of the CIV winds

be determined? In addition, the team asked one more question: Could there be a relationship between these AGN and their distance and location in the universe? The team took a look at this question, and began

by using the following equation for calculating the quasar distance: d = czH0

(1+ 0.5z)(1+ z)

, where c

represents the speed of light, z represents redshift, and Ho represents Hubble’s constant at a value of 75 km/s /Mpc. The calculations revealed that the majority of these quasars were located in a distance range between 4000 – 5000 Mpc. Figure 6. Distance to Quasars Containing CIV Wind Doppler Shifts.

Distances to Quasars

02468

101214

3000-3499 3500-3999 4000-4499 4500-4999 5000-5500distances in Mpc

In addition, these quasars’ positions in the Universe were plotted using their Right Ascension and Declination coordinates in two ways. The Figure 7 plot shows them on a straight graph, while the Figure 8 plot was done on an overlay of a universe map. The blue dots represent the quasars used in this team’s study. The locations of the quasars are probably a result of the locations of the original FIRST Bright Quasar Survey objects, and therefore, no real conclusions could be made relative to location based on this data alone.


Figure 7. Quasar Location Plot based on Right Ascension and Declination

Figure 8. Quasar Locations Overlaid on a Map of Universe. (The black dots represent the locations of this quasar set)

0 4 8 12 16 20 24


SUMMARY Much was learned from this project investigation. Both research goals were accomplished. First, it was determined that approximately 25% or ¼ of the quasars identified fit the profile for AGNs containing CIV, CIII], and MgII emission lines, and having the correct blueshift type. The second goal was to determine the rate at which the CIV wind is moving. From our data, the CIV wind shifted in a peak region between –500 km/s and +500 km/s. This was unexpected because there seemed to be a nearly equal distribution of blueshifted and redshifted CIV winds and there also seemed to be a wide distribution of velocities that may indicate a broad CIV wind cone range. An unexpected consequence of this investigation was that the blueshifted CIV wind quasars were present in low-z quasars and that these low-z quasars were commonly found at distances between 3500 and 5000 Mpc. Finally, the team also looked at the distances and locations of the quasars identified and found that there was no pattern for their distribution. REFERENCES Brotherton, et al. “Statistics of QSO Broad Emission-Line Profiles. II. The CIV λ1549, CIII] λ1909, and MgII λ 2798 Lines.” ApJ 423: 131-142, 01 March 1994. Elvis, M. “A Structure for Quasars.” ApJ 545: 63-76, 10 December 2003. Ferland. “The CIII] λ1909 Effective Wavelength-Redshift Relationship in Quasars.” ApJ 249: 17-22, 01 October 1981. Gaskell. “A Redshift Difference between High and Low Ionization Emission-Line Regions in QSOs -- Evidence for Radial Motions.” ApJ 263: 79-86, 01 Dec 1982. Leighly, Karen & Moore, John. “Hubble Space Telescope. STIS Ultraviolet Spectral Evidence Of Outflow In Extreme Narrow-Line Seyfert 1 Galaxies. I. Data And Analysis.” ApJ 611: 107-124, 10 August 2004. McIntosh, et al. “Redshifted and Blushifted Board Lines in Luminous Quasars.” ApJ 517: L73-L76, 01 June 1999. Mueller-Sanchez, Francisco, et al. Nearby AGN Research” Infrared and Submillimeter Astronomy Group at Max-Planck Institute For Extraterrestrial Physics. 15 May 2007. Richards, et. al. “Broad Emission-Line Shifts in Quasars: An Orientation Measure for Radio-Quiet Quasars?” AJ 124: 1-17, July 2002. Shuder. “Emission-Line Profiles in Low-Redshift QSOs.” AJ 280: 491-498, 15 May 1984. Tytler, et al. “Systematic QSO Emission-Line Velocity Shifts and New Unbiased Redshifts.” ApJS 79: 1-36, March 1992.


Wills, et al. “Statistics of QSO Broad Emission-Line Profiles. I. The CIV λ1549 and the λ1400 Feature.” ApJ 415: 563-579, 01 October 1993.


NGC 2367: Its Age and Distance Caitlin S. Colley

Sullivan South High School, Kingsport, TN Teacher: Thomas Rutherford, TLRBSE 2005

ABSTRACT The distance to the open cluster NGC 2367 was determined along with its age. The cluster was examined using data collected with “V” and “B” photometric filters. The images were taken with a 14-inch telescope located near Cloudcroft, New Mexico. NGC 2367 was found to lie at a distance of 2570 parsecs (7430 light years) from the earth. The age of the cluster was determined to be no older than 19.8 million years. Few M-type stars were evident. INTRODUCTION An open cluster is a group of stars that are held together by gravity and whose stars lie at essentially the same distance from the earth. They are all thought to have formed at the same time, from the same materials, and under identical conditions (Chaisson 2005). However, the stars in the open cluster do have different masses which make them age at different rates. The study of open clusters is important because they can provide information on the structure of the galaxy, provide clues to stellar evolution, and aid in calibrating knowledge of star brightnesses (Moffat 1972). The images used in this study were collected in January 2007 using a CCD camera mounted on a Celestron C14 telescope. The telescope was located at a robotic observatory near Cloudcroft, New Mexico, called New Mexico Skies. The telescope time was funded by the NOAO/RBSE Program. The cluster NGC 2367 was chosen because it had not been researched extensively. The cluster had been examined in the early 1970’s (Moffat 1972) and more recently in 2005 by McSwain (2005). OBSERVATIONS AND DATA REDUCTION Ten images were taken using each filter (B and V). Each exposure was 60 seconds in length. The 10 images were then stacked using the software MaximDL in order to give an image that was the equivalent of a single 600-second exposure. This technique improves the signal/noise ratio of the image; increasing the amount of signal (star images) at a greater rate than it increases the noise level (Starizona 2008). The resulting images were processed using the kernal function of MaximDL. This removed excess hot pixels which were present in the images. The setting for the kernal filter was 10%.


Image 1. An image of the open cluster NGC 2367 in B. The brightnesses in the image were inverted for clarity. The stars of the cluster lie just to the left of center in the “V” like formation. The brighter stars to the right were thought not to be a part of the cluster based upon their omission from numerous sources, including the WebDA site.

Originally, it was planned to use the star identification system used by Moffat (1972). However, Moffat’s image (WebDA) was of such poor quality that it was not possible to determine to which star a particular reference number belonged. Arbitrary reference numbers were therefore assigned to the stars as seen in Image 2. The stars labeled 24 and 25 in image 2 were used as the reference stars. Image 2. The stars in this study were identified according to the following numbering system. The MaximDL software compared the brightnesses entered for stars 24 and 25 and then used that information to calculate to brightnesses for the other stars in the images. It then produced an


output file that was compatible with Microsoft Excel, allowing further manipulation of the data to be performed. When the brightness of a star in B is subtracted from its brightness in V, the star’s true color (color index) may be determined according to the following equation: B - V = Star’s Color Index Equation 1 However, interstellar dust lies between the Earth and all astronomical objects. Because of this, light from the cluster was both dimmed (extinction) and reddened as it traveled toward the earth (Seeds 2005). This means that the stars appear to be both redder and dimmer than they actually are. The amount of reddening of the stars in NGC 2367 was 0.331 magnitude (WebDA 2006). This number was subtracted from each star’s (B-V) value giving the stars’ true color indices. In addition, extinction was compensated for by multiplying the reddening value (0.331 mag) by 3.2 and subtracting that value from the stars’ V brightnesses (Clemens 2007). These corrected values may be seen in Table 1.


Table 1. The B and V values for the stars in NGC 2367 were corrected for interstellar reddening and interstellar extinction according to the method mentioned in the text. The apparent duplicate entries (marked with an asterisk) were due to stars being too close together to measure separately. Star 3 (marked with two asterisks) was determined to not be a member of the cluster due to its placement on the ZAMS graph.

Star B V B-V (B-V)RED (V)RED Spectral Type

NGC 2367-1 11.09 10.61 0.48 0.15 9.55 B NGC 2367-2 13.39 13.03 0.36 0.03 11.97 A NGC 2367-3** 13.50 11.83 1.67 1.34 10.77 M NGC 2367-4 10.53 10.30 0.23 -0.10 9.24 B NGC 2367-5 13.54 13.20 0.33 0.00 12.14 A NGC 2367-6 13.04 12.85 0.19 -0.14 11.79 B NGC 2367-7 13.08 12.69 0.39 0.06 11.63 A NGC 2367-8 12.93 12.45 0.48 0.15 11.39 A NGC 2367-9 12.97 12.56 0.41 0.08 11.50 A NGC 2367-10 10.97 10.83 0.14 -0.19 9.77 B NGC 2367-11 12.73 12.24 0.50 0.17 11.18 A NGC 2367-12 12.88 12.66 0.22 -0.11 11.60 B NGC 2367-13* 10.36 10.29 0.07 -0.26 9.23 B NGC 2367-14* 10.36 10.29 0.07 -0.26 9.23 B NGC 2367-15 12.49 12.28 0.21 -0.12 11.22 B NGC 2367-16 12.84 12.24 0.59 0.26 11.18 F NGC 2367-17 9.82 9.77 0.05 -0.28 8.71 B NGC 2367-18 12.13 11.28 0.84 0.51 10.22 F NGC 2367-19 10.68 10.48 0.20 -0.13 9.42 B NGC 2367-20* 8.78 8.72 0.06 -0.27 7.66 O NGC 2367-21* 8.78 8.72 0.06 -0.27 7.66 O NGC 2367-22 13.17 12.86 0.30 -0.03 11.80 A NGC 2367-23 13.46 13.20 0.26 -0.07 12.14 A NGC 2367-24 14.29 13.75 0.53 0.20 12.69 A NGC 2367-25 12.35 11.77 0.58 0.25 10.71 F NGC 2367-26 13.11 12.51 0.59 0.26 11.45 F NGC 2367-27 13.30 12.84 0.46 0.13 11.78 B NGC 2367-28 11.07 10.61 0.46 0.13 9.55 B

ANALYSIS AND RESULTS Once the correct (B-V) values were determined for the stars in the cluster, they were classified by spectral type (O, B, A, F, G, K, and M). The criteria for making this determination may be found in Table 2.


Table 2. The spectral type of a star can be determined by measuring its (B-V) value. A star’s spectral type is also an indicator of its life expectancy (Washington 2005).

Color Index (B-V) Spectral Type Life Span (years) -0.4 O 1 × 1011

When the stars of NGC 957 are plotted on an H-R diagram containing the Schmidt-Kaler ZAMS (Zero-Age-Main-Sequence) line (1982), an estimate of the age of the cluster can be made. This involves checking to see where the cluster’s stars are beginning to curve off from the main-sequence (Seeds 2005). NGC 2367 is estimated to be about 19.8 million years old, based on the lack of a ZAMS turnoff and the presence of an O-type star. Graph 1. The ZAMS (Zero-Age Main Sequence) line (Schmidt-Kaler 1982) is overlaid with a graph of NGC 2367’s stars. No turn-off from the ZAMS line is evident. The star to the far right (Star 3) is not a cluster member.

A star in an open cluster must have its absolute magnitude known in order to have its distance from earth calculated (Comins 2003). Since this value was unknown, a “stand in” star was chosen. The star chosen for this was Canopus (alpha Carinae) because its (b-v) value of 0.15 is the same as the (b-v) value of star 1 (also 0.15).


Star 1 has an apparent V magnitude of 9.55. Canopus’ absolute magnitude (V) is -2.5. Stars that have similar (b-v) values, like star 1 and Canopus, should also have the similar absolute magnitudes. Using the distance modulus equation (Comins 2003) allows the distance to NGC 2367 to be calculated as shown in equation 2. d=10(m-M+5)/5 Equation 2 where d is the distance to the star in parsecs, m is the apparent V magnitude, and M is the absolute V magnitude. The distance to the cluster was calculated to be about 2570 parsecs or 8380 light years. This is a somewhat greater distance than that calculated by Moffat (1972) who calculated a distance of 2004 parsecs (6530 light years). Moffat, however, determined this value using a photoelectric photometer, not a CCD imager—this may explain some of the discrepency. Graph 2. A frequency graph of the spectral types of stars in NGC2367. Most stars in the cluster are of the B and A types, although one O type is also present. This study showed only one M class star, even though this is the most common type of star. The lack of detected M stars may be due to the presence of a full moon when the images were taken. Furthermore, M-class stars are faint, making them more difficult to detect than the brighter spectral types.

Spectral Type Distribution of NGC2367

2

12

9

4

0 0

1

0

2

4

6

8

10

12

14

O B A F G K M

Spectral Types

Num

ber o

f Sta

rs

DISCUSSION Since there is no apparent ZAMS turn-off, this cluster is relatively young. It is estimated to be approximately 19.8 million years old after interpolation of the values in Table 1. This is confirmed by the presence of an O-type star, which provides additional evidence that this is a young cluster.


One star, NGC2367-3 was determined to not be a member of the cluster due to its placement far from the ZAMS line. Also, the (b-v) value of star NGC 2367-21 was possibly compromised due to its closeness to the O-type star NGC 21367-20, making it impossible to determine its true value. McSwain (2005) determined that the distance to NGC 2367 was 2330 parsecs (7600 light years) and that it was 5.5 million years old. The age agrees well with the current study’s result of 2570 parsecs. The age of the cluster was estimated at 19.8 million years, which is somewhat older than McSwain’s value of 5.5 million years. McSwain’s use of a much larger telescope (0.9 meter versus the 0.36 meter used in this study) would provide a larger sample of cluster members, which might explain McSwain’s younger age for the cluster. SUMMARY Using values measured from New Mexico Skies images, the age and distance of the open cluster NGC 2367 was estimated to be 19.8 million years and to lie at a distance of 2570 parsecs (8380 light years) from the earth. The cluster’s young age was also evident from the presence of an O-type star. Additionally, there was no turn-off from the ZAMS line. ACKNOWLEDGEMENTS Thanks to Mr. Tom Rutherford for his patience, guidance, and the knowledge he instilled in me. Astronomy was not something I expected to find an interest in, but his infectious spirit towards this project spread to me and I am glad he opened my eyes to so many things, including how to find north. I would also like to thank my father for sharing the computer and letting me work in between his intense solitaire games, and to my mother for lying in our backyard watching the stars with me. REFERENCES Vogt N., Moffat A.F.J. “Southern Open Star Clusters I.” 1972, Astronomy Astrophysics Supplement Series, Supplement 7, (1972): 133-138. NASA Astrophysics Data System. Chaisson, Eric and Steve McMillan. Astronomy Today, 5th ed. New Jersey: Prentice Hall, Inc. 2005. 505. Seeds, Michael. Foundations of Astronomy, 8th ed. Belmont, CA: Brooks/Cole. 2005. 200. Starizona. “Optimum Exposures”. . 2008. Accessed 28 March 2008. WEBDA. Institute for Astronomy of the University of Vienna. 22 September 2003. http://www.univie.ac.at/webda/cgi-bin/ocl_page.cgi?cluster=ngc2367.


Clemons, Christie and Rachel Reece. “The Age and Distance of the Open Cluster NGC 2345.” RBSE Journal. 2007. 27 March 2008. University of Washington. “Cluster Color Magnitude Diagrams and the Age of Stars.” 16 May 2005. 30 March 2008. Schmidt-Kaler, Th. 1982, Landolt-Börnstein, Numerical data and Functional Relationships in Science and Technology, New Series, Group VI, vol. 2(b), ed. K. Schaifers, & H. H. Voigt (Berlin: Springer Verlag), 14 Comins, Neil F. and William J. Kaufmann III. Discovering the Universe, 6th ed. New York, NY: W. H. Freeman and Company. 2003. 277, 369. Mcswain, M. Virginia and Douglas R. Gies. “The Evolutionary Status of Be Stars: Results from a Photometric Study of Southern Open Clusters.” The Astrophysical Journal Supplement Series, 161:118–146, 2005 November.


A Search for Exoplanets in NGC 957 Bobby Adams, Rebecca Redmon, Veronica Buehrig

Sullivan South High School, Kingsport, TN Teacher: Thomas Rutherford, TLRBSE 2005

ABSTRACT Approximately 200 stars in the open cluster NGC 957 were examined. The cluster was imaged using “B”, “V”, and “R” photometric filters attached to a CCD camera. The “R” images were examined for the shallow, D-shaped changes in brightness that typifies a transiting exoplanet. The “B” and “V” images were examined in order to determine the stars’ spectral types, allowing both the age and the distance to the open cluster to be determined. No changes attributable to an exoplanet transit were detected. NGC 957 was estimated to be less than 10 million years old based on the lack of a ZAMS turnoff. The open cluster was calculated to lie at a distance of 1380 parsecs (4500 light years) from the earth. INTRODUCTION An exoplanet, or extrasolar planet, is a planet that is found outside of the solar system (Comins 2003). As of this writing, 277 exoplanets have been discovered (JPL 2008). The study of such planets is important for several reasons:

1) Based on the current ideas of how solar systems form, planets should be common around other stars.

2) The earth’s solar system is made of eight planets and numerous other bodies. The

type of planet depends on its distance from the sun with the inner planets being small and rocky while the outer ones are large and gaseous. Is this same pattern followed elsewhere?

3) The solar system contains only certain sizes of planets. Can planets exist outside of

this size range? Can they be larger than Jupiter or smaller than Mercury? The first detection of a planet outside the earth’s solar system occurred in 1992, with the discovery of two planets orbiting the pulsar PSR 1257+12 (Bisnovatyi-Kogan, G.S. 1993). The planets were detected because of the effect that they were having on the timing of the pulsar’s radio emissions (Wolszczan 1992). The first detection of a planet orbiting a main-sequence star was in 1995, when 51 Pegasi was found to have an orbiting planet (51 Pegasi b). This planet orbits its star once every 4.2 days (Kaler 2005). It was discovered by the effect that it had on the radial velocity of its parent star (Mayor 1995).

In 1999, the star HD 209458, located in the constellation of Pegasus, was found to have an orbiting planet. Although this planet was first detected by Doppler shift, it was soon found to


actually cross the face of its parent star. This exoplanet transit confirmed that the drop in the brightness of the star that occurred as the planet crossed its face was detectable from earth (Malatesta 2004). Typical exoplanet transits last from about 1-4 hours (Gary 2007), although there can be transits outside of this range. Exoplanet transits are very shallow, resulting in a brightness drop of only a few percent or less. They also have periods ranging from 1-21 days (Gary 2007), meaning that only one transit would be detectable during the observing run. Since at least two transit minima are needed to determine a period for a transiting planet no such determination can be made from this data, due to the brevity of the observing run. However, if the period of an exoplanet transit can be determined from additional studies, then the planet’s orbital inclination, its mass, its parent star’s mass, its size, its distance from its star, and its orbital period can be determi

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