Emission Spectrum and Absorption Spectroscopy

The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state.

For example, when an electron of Hydrogen transitions to a energy level of n = 3 to the base level of n = 2, it emits photons, which can be recorded as the emission spectrum.

Emission is the process by a higher energy particle converts to a lower one through emission of a photon, resulting in the production of light.

The emission spectra is produced when the electrons of the atom are excited and can change it's energy level. This produces a photon.

The emission spectrum allows us to understand the sources chemical composition, temperature, density, mass, distance, luminosity, and relative motion. These spectrum samples consists of absorption lines of celestial objects with emission spectra.

Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation such as visible light which radiates from stars and galaxies. Astronomical spectroscopy uses Doppler shift measurements as well, to determine a objects age and distance. Spectrum samples are also known to show spread shifts of celestial objects.

Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation. Absorption spectroscopy uses frequency or wavelength as a function. 

Absorption spectroscopy works when a sample absorbs energy (such as photons) from the radiating field and the intensity of the absorption varies as a function of frequency. This variation is the absorption spectrum. 

Absorption lines are Typically classified by the nature of the quantum mechanical change induced in the molecule or atom, 

Absorption spectrum samples are completely different from the emission spectrum, due to the different intensity pattern. Emission spectrum samples

Early Universe and Re-ionization

After the Big Bang, the known universe went through many phases or epochs. These epochs were characterized through certain actions that were occurring in the universe. Such actions included light characteristics, atomic and subatomic patterns and actions.

During the creation of the universe, early atoms formed, and the universe consisted of roughly 75% hydrogen and 25% helium. For about a billion years, the gas in the universe was going through two major phase changes. In the first phase change, gas atoms went through combination of electrons and protons to form neutral atoms. This rate of recombination was higher than the re-ionization rate. The Universe continued to become transparent as more electrons and protons combined to form neutral hydrogen. This was known as the dark ages, due to the absence of stars and their emission of light as well as the transparency of the universe. The universe was also dominated by mysterious "dark matter" which is still unable to be fully understood by modern Astrophysicists today. The second phase is when objects started to condense in the early universe, these objects had enough energy to ionize neutral hydrogen. These objects included early stars and galaxies. This is when the Universe went through the re-ionization epoch.

In order to understand the early universe we must understand the basic characteristics of early galaxies. In the beginning of the age of re-ionization, early stars began to mass and clump in clouds of dust, forming protogalactic clouds. In these clouds, gravity caused gas and dust to collapse and form stars. These young stars burned out quickly as gravity continued to collapse the clouds. As the clouds collapsed, they began to form galaxies, as gravity cased other nearby clouds to merge and collide forming larger galaxies. This plays an important part in the evolution of galaxies.

Some question many astrophysicists have is that when and how did re ionization occur? What sources caused re-ionization? What are the first galaxies? These questions also intrigue me, as I plan to look deeper and learn more about the early universe. 

In terms of myself, I really want to know more about the characteristics of these early galaxies, as well as understanding how these early galaxies could have affected the re-ionization of the universe. 

Summary of Progress on Sophomore Year

Hello all,

My junior year has already rolled into action, and I thought it would be a good idea to "round up" on what I've accomplished last year as a sophomore, generally summarizing details to put them into a much more organized manner.

I am working with Dr. John Moustakas, a professor a Siena College, NY on the topic of discovering new galaxies. Dr. Moustakas has been collaborating with a team known as CLASH (Cluster Lensing And Supernovae survey with Hubble) and has conducted extensive research on many galaxy clusters. His team just concluded research on Galaxy Cluster Abell 2744 and moved onto researching Galaxy Cluster MACSJ0416-2403.

Galaxy Cluster MACSJ0416-2403

Regarding progress of work from my sophomore year, I was able to analyze galaxy cluster Abell 2744, backed up by Dr. Moustaka's work. A lot of time was spent on understanding the background information regarding the Galaxy Cluster Abell 2744.

The Universe is believed to have been created about 13.7 billion years ago in an event called the Big-Bang. This is supported through the analysis of cosmic microwave background, thermal radiation left over from he Big Bang. Primordial atoms were created (hydrogen, helium) and they eventually clumped together forming stars. After that stars began to clump together to form the earliest galaxies. Eventually these early galaxies collided and merged with others to form the modern galaxies we know today (ie: Milky Way, M101, M64).

In order to understand our galaxies we know today, having a good understanding on the earliest galaxies is a must. These early galaxies are known as Lyman Break Galaxies (LBGs). Before we discuss (LBGs) we must understand the effect of redshift.

Redshift is the "stretching" of wavelengths, making them shift towards the red side of the electromagnetic spectrum. Redshift is caused by the constant expansion of the Universe. For example, an X-Ray stretching it's wavelength to visible light.

Notice how the spectrum shifts towards the red part of the spectrum the father the celestial object is from the viewer's location.

 Much of the light we see in space is in the visible part of the spectrum. However since space stretches 13.7 billion light years across (and counting) redshift causes visible light produced from the early galaxies to stretch from the visible part of the spectrum to the infrared part of the spectrum. This affects the early LBGs in great amounts. Because of the Universe's expansion, the redshift in the universe causes distant galaxies (12 billion years or older) to become invisible to visual-light observing instruments.


Another factor that affects LBGs (particularly in massive galaxy clusters) is gravitational lensing. Gravitational lensing is when the gravity that is between galaxies that make up the cluster becomes so strong, it causes light to bend. The light warps, magnifies, and duplicates the background light. Gravitational lensing allows Astronomers to look at light that would be almost impossible to see without the gravitational lens. This allows us to "cheat" and look at much earlier galaxies.

The streaks/smears of light is actually light produced from galaxies behind the Galaxy Cluster. 

Now, Lyman Break Galaxies are galaxies that are star-forming galaxies at high redshift. These galaxies are identified through a technique known as the Lyman-break technique. The Lyman Break technique is a technique used to observe a galaxies Lyman limit. The Lyman limit corresponds to the most energetic photons that can be emitted from hydrogen. The known Lyman limit is around 91 nm, this represents the energy required to remove an electron completely from a hydrogen atom, starting at the lowest energy level. The Lyman break technique is really helpful when it comes to determining the redshift of the galaxy, because it compares the observed wavelength to the emitted wavelength.

Here is the official formula for the wavelength based redshift equation:


For example,
A galaxy with a redshift of 7.2 would have it's wavelength observed at around 10,000 angstroms, due to the expansion of the universe. This causes wavelengths of light to be stretched towards the red end of the electromagnetic spectrum, hence the term "redshift" . However, technically it's real emitted wavelength would be around 1215 angstroms. This data is plugged into the equation to prove that the galaxy's wavelength is around 7.2.

Lyman break galaxies with a high redshift tend to not appear in the visual filter. This is due to the lightwavelengths  emitted from galaxies to be shifted into the infrared sectiopn of the electromagnetic spectrum. This is caused by the expansion of the universe. The Lyman break helps represent when the galaxy becomes observable, as the galaxy is observed under mulptiple filters based on designated wavelengths. For example, the Hubble Space telescope observes these Galaxy clusters under many different filters which range from wavelengths of 814 microns (visual) to 1600 (infrared).

More to Come!

Continuity of Work, and Gazing Towards the Future

On June 5th, at 7:00 pm at the Burnt Hills High School, I will be present at the symposium to present my poster based on the summary of my work so far. Many of my details come from other blog posts. Data collection from the SAOImage ds9 program as well as references from Dr. Moustakas's paper Young Galaxy Candidates in the Hubble Frontier Fields. I. Abell 2744.

I will be continuing my research on Lyman Break galaxies, studying the flux ratio, the brightness of each pixel in different filter (F814W all the way up to F160W), this will further our understanding of these mysterious distant high redshift galaxies. We can do this using a program known as SExtractor.

Hopefully I will be able to create Lyman Break Forests of the galaxy candidates in Abell 2744 as well as other galaxy clusters in the Hubble Frontier Fields Initiative.

Just recently, the Hubble Space Telescope Team unveiled a new image of the deep universe consisting of light from ultraviolet light all the way to near infrared light. this image consists of approximately 10,000 galaxies.

The farther you look back, the farther back in time you are.

Making Connections and Analyzing Lyman-Break Galaxies In the Universe

The Big Bang occurred around 13.6 billion years ago. This is supported through the analysis of cosmic microwave background, thermal radiation left over from the Big Bang. Thousands of years after the Big Bang, young stars formed and died, and eventually they grouped up together, forming the first young galaxies. The goal of my project is to discover the first galaxies to form in the 13.6 billion year old history of the Universe. Most of the data of my project is collected from the Hubble Frontier Field initiative, a current program that is analyzing galaxy clusters and their gravitational lensing. A gravitational lens is when gravity causes light to bend and warp. Due to the sheer gravitational force found within galaxy clusters, it causes light emitted from other galaxies to warp, bend, and magnify itself. This allows Hubble to "cheat" in a sort of way. Since the light from distant galaxies is too dim for Hubble and it's advanced instruments, gravitational lensing allows us to see these distant galaxies since the light is magnified. These distant galaxies are aged around 13 billions years or even older. 

Gravitational Lensing can be easily observed in Galaxy Cluster MACS J1206.2-0847. The streak-like figures of light can be easily visualized through the intense gravitational effects of the gravity within the Galaxy Cluster due to the immense amounts of dark matter.

We can select these galaxies through the use of filters and the Lyman Break Technique. Filters allow us to block and pass through levels of the electromagnetic spectrum. We use the photometric system called the Johnson-Morgan system, developed in 1953. This system uses a number of filters, U for ultra violet, B, for blue light, V, for visual light, G, for green, R for red, And I for infrared. Within the infrared filter, there are many sub categories, ranging from near infrared to far infrared. The galaxies I am analyzing can be found in the Y filter. Regarding galaxies being found in the Y filter, it means that the Lyman-Break occurs in the Y filter, or the galaxy is a Y "dropout". The Lyman-Break technique is a technique used to discover the age of the galaxy by analyzing the hydrogen atom. A Lyman-break is a term used to describe the action of a electron (on any energy level) ionizing and retreating to the first energy level. We can find the galaxies age by using the redshift equation ( Z + 1 = (Observed Lyman-Break/ Rest Frame)). A normal hydrogen Lyman break is found within the wavelengths of 912 Angstroms to 1215 Angstroms. However in space, due to the expansion of the universe, the Lyman break will be shifted towards the longer wavelengths of the electromagnetic spectrum. For example, a galaxy with a redshift of 7 will have it's Lyman-Break observed at around 10000 Angstroms rather than 1215. In other commonly used astronomical units, the observed Lyman Break would be at 1 micron rather than .1215 microns, or in nanometers; the observed Lyman-Break would be at 1000 nanometers rather than 121.5 nanometers. 

Lyman-Break Forests of YD4, YD9, ZD6, and ZD9

Equation used to find the redshift of Lyman-Break Galaxies

Now, for example, if the Lyman-Break would occur at 10000 angstroms, we would not be able to see the galaxy in the visible part of the spectrum, however, this galaxy (which is supposed to be seen in the visible part of the spectrum) is so far away, that it's emitted light is red shifted all the way into the near infrared section of the electromagnetic spectrum. In this project, I can visualize and see when the galaxy "pops" up.

  

Lyman-Break Galaxy YD7 can be observed by comparing the area inside the designated YD7 Circle. Above, is the image of YD7 in a filter known as F814W, a filter allowing visible light in while it blocks out the infrared light. Below, is the image of YD7 in a filter known as F160W. This filter allows longer wavelengths, mostly infrared light in as well as some of the visible light spectrum. The whole point of comparing the images is that if YD7 was nearby, it's Lyman-Break would in the visible part of the spectrum. But it is missing from the visible filter. However we see it appear in the near infrared part of the spectrm. This is because of the expansion of the universe, it causes the Lyman-Break to be shifted towards the longer part of the spectrum.

Abell 2744 and it's Y Dropout Galaxies Shown Through Different Filters

I am sorry I have not been updating my blog lately, I have been caught up with other tasks. However, I have been able to save a image of galaxy cluster Abell 2744 including it's distant galaxies. The reason that the distant galaxies are named YD is because the galaxies are so distant and dim, that the wavelengths we receive are literally dropping out of the Y passband on the\electromagnetic spectrum. This is because since the Universe is expanding, it causes the wavelengths to stretch along with the "fabric" of space. This causes the wavelengths we receive from these galaxies to become redshifted.

Galaxy Cluster Abell 2744 in the F160W filter 

Galaxy Cluster Abell 2744 in the F814 filter

One of the coolest things is that these distant galaxies are so distant, that they only appear in the near-infrared wavelength filter, or the F160W. This filter only allows wavelengths at 1.4 to 1.7 Microns to pass through. These wavelengths are found within the near infrared section of the electromagnetic spectrum. F814W however, is a filter allowing wavelengths of .7 to 1.0 Microns to pass through. These wavelengths are found within the optical section of the electromagnetic spectrum.

These distant galaxies are known as Lyman-break galaxies, or LBGs. Lyman-break galaxies are star-forming galaxies at high redshift (Abell 2744 has LBGs at 7 and greater). These galaxies are chosen through a technique called the Lyman-break technique. The Lyman-break technique is used by observing a galaxy's Lyman limit. This represents the energy required to remove an electron completely from a hydrogen atom, starting from it's lowest energy level. Since galaxies consist of a lot of stars, and stars consist mostly of hydrogen gas, it would be appropriate to study and observe the hydrogen atom (simply because there is an abundance of hydrogen in the universe). Because of the photons emitted from the stars within the galaxies, these photons can ionize neutral hydrogen atoms and will be absorbed by interstellar and/or intergalactic clouds of hydrogen. Any photon more energetic than the Lyman limit (912 - 1215 Angstroms) is most likely to be absorbed quickly by a hydrogen atom, because it can completely eject the only electron. This is represented by the sharp break.

Lyman Breaks (straight vertical lines)  can be seen around 1.0 Microns 

A regular galaxy will have it's Lyman break at the 912-1215 angstroms. However, a galaxy such as YD9 with a red shift of 8.1 would have it's Lyman break red shifted all the way into 1.0 Microns rather than having it around 912 - 1215 Angstroms. The only way to observe these galaxies are through observing them through different filters. The Lyman-break can literally be seen through shifting through the F814W and the F160W. This is so, because the wavelengths are so redshifted, no photons can be observed through the regular optical filters. Filters that allow the near infrared will allow the redshifted wavelengths to pass through. 

(Above) YD1 can be barely seen through the F160W filter
(Below) YD1 cannot be seen through the F814W filter. This is so because the Lyman Break is so redshifted, that it is in the near infrared part of the electromagnetic spectrum

(Above) YD9 is clearly shown in the F160W filter, while it is barely observable in the F814W filter (Below)

My biggest question as of right now, is how do Astronomers simply "pick" these distant Galaxies? Do they just know that these are good candidates for LBGs? Or is there much more of a process to finding these LBGs?

More soon!

Continuing to read papers, working on ds9, and much more!

I located distant galaxy candidates in Abell 2744, on the program SAOImage ds9. I found these objects by punching in data regarding the distant object's right ascension and declination. However, discovering these distant objects in the future will not be based on their right ascension and declination, but based on other information such as redshift. I do not have an image with the green circles and labels pointing out the location of these distant galaxies, but as soon as I do, I will be able to post them onto the blog. 

I am also reading papers, and I will be giving a summary about them in the future!

-Ben Schiher 

Gravitational lensing "copying" a distant quasar 

Hydrogen, the Element of the Universe

Hydrogen is the most abundant element in the universe. Stars use hydrogen their nuclear fusion process. Nebulae consists of large amounts of hydrogen that allow young stars to form.

Stars like the sun, produce energy through nuclear fusion, where hydrogen atoms are fused together to create products such as neutrons and helium

The Mystic Mountain in the Great Carina Nebulae (NGC 3372). This nebula is filled with hydrogen, just like the rest of the other nebulae.

The hydrogen atom consists of a proton and an electron which are bound together. The proton has a negative charge while the electron has a positive charge. Because they have different charges, the proton and electron constantly interact and stay with each other.

However, the electron can escape. If a electron escapes from the proton. the atom is ionized. In astronomy the former type of ionization is much more common. It is easy to visualize that the electron orbits the proton, most of use visualize a planet (electron) revolving around the sun (proton). However, the electron exists as a cloud orbiting around the nucleus. The density of this cloud is the strongest in the center, and it thins out.

The brighter/denser areas is where the electron is most likely found orbiting

The amount of energy in a electron determines how far away the electron is from the proton. Electrons can only have a certain amount of energy for each orbital state. Each orbital state has a specific range of stored energy. The lowest energy an electron can have is called the ground state. The ground state is the closest orbital to the proton.  When the electron has higher energy than this lowest energy, it is excited, and It moves out, into the next orbital state (ie 1st, 2nd, 3rd Excited state orbital). 

These states of hydrogen are quantized. The electron in hydrogen can only have a certain amount of energy stored. These are called hydrogen's energy levels. The different energy levels are denoted by the quantum number n. For example, electrons with a high n (100) are weakly bound.

A hydrogen electron with a high energy level can be striped or ionized with energy called ionization energy. The energy levels are usually referred as being negative quantities. 

A hydrogen atom with excess energy is said to be excited. Two primary ways to excite an atom are through absorbing light and collisions. When two atoms collide energy is exchanged. Sometimes the energy is used to excite an electron from a lower energy level to a higher energy level.  The amount of collisions and how energetic their collisions are will depend on how tightly the hydrogen atoms are spaced and their average temperature.

....

This was a much more tougher lab than the others. This is so because I have not yet taken chemistry yet, but the Hydrogen Atom simulator really helped me visualize how energy such as Lyman, Balmer, and Paschen series of energy affected the hydrogen atom's electron. I learned that as the electron gets farther away from the proton, the less energy the electron can absorb. Much more energy levels can cause the electron to move or excite and ionize the electron. As I was conducting this lab, I had one major question, how do astronomers use energy levels to study such distant objects like galaxies? Another minor question was that what is the significance of the Lyman, Balmer, and Paschen series of energy, and what is their significance to astronomy?

Redshift, Hubble's Law, and it's Relationship to the Expansion of the Universe

The Universe as-we-know-it is theorized to begin from the Big Bang, the idea that the universe began small and expanded. The Big Bang wasn't much of explosion, in fact it was the heating up and spread of matter.

The first evidence of the Big Bang came from Edwin Hubble. His observations included estimating the distances of the galaxies form our own. His observations on the light from the galaxies provided intriguing information. Hubble observed that absorption lines in the spectrum were almost always "shifted" to longer wavelengths the redder area of the spectrum. Hubble called it "redshift." 

The wavelengths tend to stretch as an object moves away from the observer. For example, a police car with it's sirens on will tend to change it's pitch as the car moves towards you and away from you. This is called Doppler shift.This is because the wavelengths of the sound changes as the waves come towards you and away. The waves coming towards you tends to be shorter in wavelength and the waves moving away from you have longer wavelengths.

Now, using galaxies, the Doppler shift works the same way. Galaxies (i.e The Andromeda Galaxy) coming towards us have wavelengths shorter than what they are originally supposed to be. Distant Galaxies on the other hand are moving away from us, causing their waves to be longer than originally measured. The wavelengths tend to stretch as an object moves away form the observer.

A galaxy coming towards us has a shorter wavelength than a galaxy receding. This is important for astronomers because it helps them understand how far away the galaxy is, and how fast it is receding/coming towards us.

Hubble measured the amount of the shift in the spectra from the galaxies. He was able to calculate the recession velocities of the galaxies. This measurement is known as Hubble's Law. Hubble's Law = The velocity at which a galaxy is moving away from us is proportional to the distance of that galaxy.

Hubble's Law: V= H x D

• V: The velocity of recession
• H: Hubble's constant
• D: distance of galaxy

In order to be able to solve the law, data must be obtained. Hubble's constant is the result of comparing and observing the distance of many galaxies and compared the distances to the recession velocities of the galaxies. Hubble's constant is 22 km/s/mly

The distance of galaxies cannot be precisely measured, but astronomer have a good estimate of how far away the galaxies are. They use many methods, such as determining the parallax shift and the brightness of stars within galaxies. Parallax is the visual effect produced when nearby objects appear to shift position relative to more-distant objects. These indirect measurements of the distance of galaxies often fail when it is applied to distant galaxies. Distant Galaxies are observed by their intrinsic brightness, the amount of light actually emitted by the object.

A great picture, showing what astronomers use to discover the distance of celestial objects such as stars and galaxies

However, a much more accurate distance measurement can be made from the redshift of a galaxy. This is called the Velocity-Distance relation, and it makes it possible to infer the distance of an object from a measurement of its spectrum. The amount of the shift varies directly with the actual distance to the object. This is one of the reasons why redshift is so important.

The definition of redshift

After calculating the distance and Hubble's constant, a close estimate of the velocity of the recession of the galaxy can be made.

Hubble's law seems to imply that we are sitting at the center of the explosion, with everything moving away from us, but the expansion looks the same from any point in the universe. Hubble's law not only shows that the Universe is expanding, but we can also use the rate to determine how long this expansion has been occurring.

If we measure the distance between two galaxies and then divide the distance by the velocity of recession, then we can be able to determine how long it took for the the galaxies to reach their current distance.

For example, a galaxy 100 million light years (mly) away with a velocity of recession of 2,200 km/s would take 13.6 billion years to reach it's current distance.

Because more distant galaxies also move apart faster Hubble's law says any two galaxies reach their present separation in the same 13.6 billion years. This means that the Universe is around 14 billion years old.


This was a generally easy summary, and I did not have much questions on the expansion of the universe and redshift. I have done a lot of background reading on this topic before and this made sense to me. However I did have some questions. What is the Velocity-Distance Relation? The sources did not give much information about the exact relation. Another question was that how do astronomers really determine the time galaxies take to reach their current distance? I tried using the same format (100 mly / 2,200 km/s) and I did not end up with 13.6 billion years. I ended up with something more like .045 mly/km/s. I don't know if I am doing the math right, or if there is much more advanced math needed. 

High-Level Summary of Broadband Filters and Concepts of Right Ascension and Declination

Since celestial objects, such as galaxy clusters, are so far away how come we know much about them?

Astronomers can only study celestial objects through the light that is emitted from them. Spectroscopy is used to study of the light emitted from those objects. Spectroscopy is the study of spectra, which is light produced from the separation of components of light by their different degrees of refraction according to wavelength.

There are two important components to light. It's wavelength and it's and Frequency. Wavelength is the length between the oscillation of a wave. The frequency is the amount of wavelengths passing through a certain point.

The Electromagnetic Spectrum shows that there is much more forms of energy than just the light you are seeing right now. The different types of light are distinguished by their wavelength and their frequency. The types of electromagnetic energy vary from Gamma Waves (high frequency, short wavelength) to Radio Waves (low frequency, long wavelength).

Broadband filters are used to control and pick the range of wavelengths over which the brightness is measured. This is so because astronomers can not measure the intensity of light and its wavelengths simultaneously. A filter is a precisely manufactured piece of colored glass that is placed in a telescope. The percentage of each wavelength is carefully designed to collect pieces of information. A broadband filter allows a large range of wavelengths to pass through each filter. Broadband filters are usually described in terms of FWHM (full width at half maximum). FWHM is a measurement of the wavelength range of the pass band at half the maximum transmittance. Certain types of broadband filters are Ultraviolet, Blue, Visual, and Red. These filters are commonly used in astronomy to measure the brightness of stars. Astronomers are also interested in the difference between filter brightness values. These are known as color indices and their values often indicate other astronomical values.

UBVR Filter's and their transmittance. Broadband filters allow a large amount of wavelengths to pass through each filter.

Another important part of astronomy is it's coordinate system. This is important because it allows Astronomers to accurately plot celestial objects in the celestial sphere. The celestial sphere is an imaginary sphere of infinite radius with Earth at the center.

Earth uses longitude and latitude to plot its geographic marks, however in the celestial sphere astronomers use right ascension and declination. Right ascension is related to longitude and declination is related to latitude.

Right ascension is very similar to longitude but runs in a 24 hour circle using hour increments instead of degrees. For Earth, the prime meridian represents a 0 in longitude. In the celestial sphere coordinate system, the Vernal Equinox Point is a line representing 0hrs. The Vernal Equinox Point is right above the Prime Meridian. Right ascensions' scale starts at the Vernal Equinox Point at 0hrs goes east until 24 hours. For example, 15 degrees east of Greenwich, England is 1 hour right ascension. The half-circle with right ascension is called the 0 hour circle.

Declination, on the other hand, is like latitude. However, it does not use north or south. Declination starts at the "equator" which represents 0 degrees. Above the equator in the celestial sphere, objects are represented using a + sign. A object below the equator is represented with a -. The celestial sphere coordinate system has two poles, the north celestial pole and the south celestial pole. Both are directly above their corresponding pole on Earth. The scale of declination goes from 0-90 degrees, +90 being the north celestial pole and -90 being the south celestial pole.

I did have some troubles with the broadband filters section. The lab section did help me out visualize how broadband filters can change the wavelengths and intensity of light, and how the intensity of light determines stellar object's colors. However, the FWHM really didn't make much sense to me as well as how astronomers really use broadband filters. One question I had in mind was what is the broadband's importance and what can they do other than helping astronomers learn about certain star's brightness's. For the coordinate systems regarding right ascension and declination, it was pretty simple. I really understood the concepts easily except for the 0 hour circle. If you could clear me up on that, it would be great!

In the meanwhile, I am working on a hydrogen lab and I will post another summary in the future, alongside a summary regarding the expansion of the universe.

-Ben Schiher

SAOImage ds9 image of Abell 2744 (Pandora's Cluster)

Here is a working picture of the Abell 2744 Galaxy Cluster in zscale! Right below it is an optical image of Abell 2744

Here is Abell 2744 portrayed on SAOImage ds9, Each CCD Pixel represents a measurement of the photons collected

Optical Image using the Advanced Camera for Surveys (ACS) and the Wide Field Camera 3 (WFC3) by the Hubble Space Telescope

Continuing to Work on SAOImage ds9 and Working on Basic Astronomy

2/20/14

Hello All!

Just another weekly update, I am still working on the ds9 image program, and I am beginning to work on tutorials that will increase my knowledge of the program. I am leaning about how astronomers use broadband filters to isolate various parts of the electromagnetic spectrum. I am also working on basic astronomy, learning about right ascension and declination.

More to come!

Ben Schiher

I seem to having a issue with saving images on ds9... almost all of my images look like this, having a sliver of what the actual image looks like on the program. 

Introduction on using SAOImage ds9 Program

2/13/14

Hello All!

I am currently fiddling around with SAOImage ds9, and I looked at an Image of Abell 2744. I also played around with the scales and  There is still a lot to learn and figure out, so I will be sure to update!

Unfortunately the program did not allow me to save the image completely so I will try to see if it can work in the future.

Ben

CLASH: Three Strongly Lensed Images of a Candidate Z~Galaxy

2/11/14

Hello All!

This week, I will be focusing mainly on reading Clash: Three Strongly Lensed Images of a Candidate z~Galaxy. This article is going to be one of the key articles I will be mainly focusing on.

I will be posting questions I have on the article next week.

Ben Schiher

Article:
http://arxiv.org/pdf/1211.3663v1.pdf

Dupont Essay Challenge Entry

2/5/2014

Together, we can be innovative everywhere

Today, I typed a small 733 word essay on the topic of Gravitational Lensing, It was for the DuPont Essay Challenge, and the challenge I chose was "Together, we can be innovative everywhere". So, I typed up a a essay based on my current knowledge of gravitational lensing and dark matter. If there is any wrong or mislead information, please let me know!

                December, 1995. The Hubble Space telescope peers deep into the constellation Ursa Major for 10 consecutive days. The area was blank to human eyes, and when the Hubble Space Telescope took the exposure with its wide field and planetary camera 2, over 3,000 galaxies were discovered in the image. Since then, Hubble has been able to look deeper into space. In 2003, the Hubble Space Telescope completed the Hubble Ultra Deep Field Image. The exposure looked even deeper into the universe, revealing early distant galaxies that looked at galaxies as young as 400 million years old. Astronomers continue to try and look deeper into the universe. In 2018, the James Webb Space Telescope will be launched and it will be capable to look deeper than ever before. But before the telescope is sent up into space, there is one more way to look even deeper into space and it is called gravitational lensing.

                According to Albert Einstein’s general theory of relativity, light bends when it passes by a body of mass. This is proven by the bending of light from distant galaxies behind galaxy clusters. The light emitted from the galaxies are not only warped, but they are magnified through the process of gravitational lensing. Astronomers have been able to tell that some of the distant galaxies are 300 million years old, which sets a new bar for the farthest ever peered into the universe. The Hubble Telescope uses the wide field camera 3 and the advanced camera for surveys to look deep into space to observe galaxy clusters such as Abell 2744, or the Pandora Cluster. However, the beginning of the research of cluster lensing was the CLASH Initiative. CLASH stands for Cluster Lensing And Supernova survey with Hubble. The program observed 25 massive galaxy clusters with HST’s new panchromatic imaging capabilities. The goals of the project is to map the distribution of dark matter in galaxy clusters using strong and weak gravitational lensing. Dark matter is non-baryonic matter that is currently unknown to science. However, we can learn more about dark matter through the learning how its gravity effects light through either weak or strong gravitational lensing. The CLASH initiative also detected and characterized some of the most distant galaxies yet discovered at z> 7 (when the Universe was younger than 800 million years old). Also CLASH studied the internal structure and evolution of the galaxies in and behind these clusters. CLASH was so successful that it planted the seed for the Hubble Frontier Field program. The Hubble Frontier Field program continued on with CLASH’s work as its basis. The HFF initiative’s goal was to undertake a revolutionary deep field observing program to peer deeper into the Universe than ever before and provide a first glimpse of the James Webb Space Telescope. The HFF observed dozens of massive galaxy clusters and selected candidates based on their lensing properties. Such properties are that the clusters are known to be massive and highly efficient lenses, the clusters have several sets of known multiple image systems confirmed with spectroscopic redshifts, and most of the clusters have high-quality magnification. Images produced from the HFF will improve understanding of galaxies during the epoch of reionization and provide unprecedented measurements of the dark matter within massive clusters. This is innovative because this will help us understand how the first galaxies looked like, helping us solve the mysterious puzzle of how galaxies formed and evolved after the big bang. Not only does this help us understand what the earliest galaxies looked like, but it will help us understand and make a step towards understanding Dark Matter. Who knows? Maybe learning how clusters bend light will crack the code of dark matter? If we do continue to study and research gravitational lensing, we will open a door to learning more about the early universe.

                Since 1995, humanity has been looking deeper into the universe. Astronomers have discovered that using gravitational lensing, we can discover galaxies as young as 300 million years old, younger than any other galaxies we have discovered. Also, using the lensing from clusters, astronomers can truly understand and learn more about dark matter and its distribution throughout the universe. This innovation will shape the course of astronomy in the future along with the James Web Space Telescope, which will peer even deeper into the universe, helping astronomers learn more about the early universe.           

                                                                                                                                                              

Summary of the Hubble Frontier Fields Initiative

2/4/2014

Summary of the Hubble Frontier Fields Initiative

"The history of astronomy is the history of receding horizons." - Edwin Hubble

The Hubble Frontier Field initiative is a project that primarily uses the Hubble Space Telescope. The telescope observes distant galaxies, magnified through gravitational lensing from galaxy clusters. This Initiative is currently being done to help astronomers look deeper into the universe, to learn more about learn more about dark matter, and to learn about the first galaxies after the Big Bang. Galaxy clusters are large groups of galaxies, held together through non-baryonic (matter not made up of neutrons, protons and electrons, and thus not likely any of the known chemical elements) matter; another name for this mysterious matter is “dark matter.” In Einstein’s theory of relativity states that light passing near a mass of object is bent by the curvature of space. A cluster of Galaxies can act as a lens and bend the light in our direction so Hubble can view it.

 (Top)
A representation of how light bends due to the gravity in Abell 2744, or Pandora's cluster
(Bottom)
A quick video simulating gravitational lensing 

The light is also magnified which allows us to see more distant galaxies making the Frontier Field initiative a step towards understanding the early universe. The HFF initiative allows us to see galaxies that appeared in the first few hundred million years of the universe.The Frontier Fields are selected to be among the strongest lensing clusters on the sky. There are currently a handful of Frontier Field candidates shown here below.

Cluster	z	RA	DEC
Abell 370	0.37	02:39:52.8	-01:34:36
MACSJ0329.6-0211	0.45	03:29:40.3	-02:11:42
MACSJ0416.1-2403	0.42	04:16:08.4	-24:04:21
MACSJ0451.0+0006	0.429	04:51:54.6	+00:06:17
MACSJ0717.5+3745	0.545	07:17:35.6	+37:44:44
MACSJ0744.9+3927	0.686	07:44:52.8	+39:27:24
MACSJ1149.5+2223	0.543	11:49:35.7	+22:23:55
MACSJ1423.8+2404	0.54	14:23:48.3	+24:04:47
Abell 2744	0.308	00:14:23.4	-30:23:26
MACSJ0257-2325	0.505	02:57:08.8	-23:26:03
MACSJ0520.7-1328	0.340	05:20:42.0	-13:28:48

These candidates were selected primarily based upon their lensing properties. Such properties are as of the following.

•         The clusters are known to be massive and highly efficient lenses
•          The clusters have several sets of known multiple image systems confirmed with spectroscopic red shifts
•          Most of the clusters have high-quality magnification maps based on data in hand.

       

Frontier Field Abell 2744 (Pandora's Cluster)

       A perfect example of gravitational lensing is the long-exposure image of massive galaxy cluster Abell 2744 (Pandora's Cluster). This cluster warps space to brighten and magnify images of far-more-distant background galaxies as they looked over 12 billion years ago. The Hubble Image above reveals nearly 3,000 of these background galaxies interleaved with images of hundreds of foreground galaxies in the cluster. Though the Pandora Cluster has been intensively studied as one of the most massive clusters in the universe, the Frontier Fields exposure reveals new details of the cluster population. Hubble sees dwarf galaxies in the cluster as small as 1/1,000th the mass of the Milky Way. On the other side, there has been galaxies discovered that are 100 times massive as the Milky Way. Images like the one above can help astronomers map out the dark matter in the cluster with detail, by charting its distorting effects on background light. Dark matter makes up the bulk of the mass of the cluster. 

      

The Frontier Field initiative has many goals. The Frontier Field is undertaking a revolutionary deep field observing program to peer deeper into the Universe than ever before, combined with the natural lensing of the galaxy clusters. The Hubble Space Telescope will produce the deepest observations of clusters and their lensed galaxies ever obtained. The initiative will help astronomers learn more of the distant galaxies that are magnified through the natural lens of clusters. Images taken by the telescope will reveal distant galaxy populations ~10-100 times fainter than any previously observed and improve the statistical understanding of galaxies during the epoch of reionization, and provide new measurements of dark matter within the galaxy clusters.

The Frontier Field Initiative challenges and answers many scientific questions about the early universe. Such questions were as the following.

• How far back into the universe can we look?
• What is the faintest- and possibly most distant- galaxy we can see not with the Hubble Space Telescope?
• What is the distribution of Dark Matter in the known universe?
• What did the first galaxies look like?       

As I read through and took notes from many websites containing vast data and information regarding the Frontier Fields, I had a few questions. What is reionization? What is its importance to the Frontier Fields? Another question was that why does the Hubble Space Telescope have to stare at a blank spot for hours? Do all galaxy clusters have gravitational lensing? If not, what makes them different from the galaxies that do have gravitational lensing? I believe these questions will help me continue on with research and help me understand the "hot topic" in Astronomy known as gravitational lensing.

- Ben Schiher

Resources:

• http://hubblesite.org/newscenter/archive/releases/2014/01/
• http://www.stsci.edu/~postman/CLASH/For_Astronomers.html
• http://www.stsci.edu/hst/campaigns/frontier-fields/
• http://hubblesite.org/newscenter/archive/releases/2012/36/
• frontierfields.org

Thanks to,

Dr. John Moustakas, Siena College