Supernovae in Distant Galaxies

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1 Hubble Space Telescope Cycle 11 General Observer Proposal Principal Investigator: Mr. Anthony Martorano Institution: Stony Brook University USA/NY Electronic mail: Scientific category: HOT STARS Scientific keywords: SUPERNOVAE, COSMOLOGICAL PARAMETERS AND DISTANCE SCALE, HIGH REDSHIFT GALAXIES, HUBBLE DEEP FIELDS, EMISSION LINES Instruments: ACS Proprietary period: 12 Cycle 11 primary orbits: 70 Cycle 11 parallel orbits: 0 Special Proposal Types: Innovative Abstract The Purpose of this investigation is to locate supernovae throughout the universe. This is a target of opportunity project (TOO), since I am trying to locate new supernovae. I am mainly concerned with locating supernovae in high-redshift galaxies, so I will be observing thegalaxieswithinthehubbledeepfield. IplantousetheACSforopticalimagingtodetect supernovae, and also to use the COS to take spectra of the supernova in the ultraviolet band. The reason for taking the spectra of these supernovae is to determine the type of supernovae. Spectra that don t show hydrogen emission lines are classified as type Ia supernovae, and this is what I am interested in observing. Type 1a supernovae are important in astronomy because they all have a very similar absolute magnitude. The reason for this is because when a white dwarf in a binary system accretes matter from a companion star, once it reaches a certain mass known as the Chandrasekhar mass,the white dwarf goes supernova. This makes all supernova 1a very consistent, ad allows astronomers to use them as standard candles. Analyzing the light curve of the supernovae will also help to determine if the supernovae are of type Ia, since these supernovae have very characteristic light curves. Observing type Ia supernovae will help determine distances and redshifts to far away galaxies. This has many important implications in the study of cosmology such as determining the scale factor and

2 Hubble parameter at the time that the supernova took place. 2

3 Investigator Institution Country PI: Mr. Anthony Martorano Stony Brook University USA/NY Total number of investigators: 1 Observing Summary: Configuration,mode,aperture Total Target RA DEC V spectral elements orbits Flags HUBBLE DEEP FIELD Unknown ACS/WFC,COS/FUV 70 TOO IMAGING Unknown Grand total orbit request 70 3

4 Scientific Justification The are many important scientific reasons for observing distant type Ia supernovae. By determining the redshift to the galaxies in which these supernovae take place, this provides us with a lot of information about the universe at that time. For instance, determining the redshift will allow us to calculate the scale factor at the time of the explosion. Thus, we will be able to determine the expansion rate of the universe at that time. If we can collect enough data on different distant supernovae, we can see how the scale factor varies over time. The redshift also allows us to determine the value of the Hubble Parameter at the time of the supernova. This gives us a lot of insight into the universe at earlier times. This data is crucial because it will help us confirm theoretical cosmological predictions, in particular it will help us determine if the Benchmark Model of the universe is accurate. If we can confirm that the Benchmark Model is a good fit for our universe from observational data, then we can conclude that the universe did in fact start with a hot big bang. This can also give us more insight to how the universe will end. This is why observing and studying these supernovae in distant galaxies are very important. When we look at a high redshift galaxy through a telescope, we are essentially looking back in time, because the light that we are seeing had to travel very far distances. The distance to these galaxies can be calculated by observing the redshift. By observing the very distant universe, we are essentially looking at the universe at a time very soon after it became transparent. According to the Benchmark Model, the universe is believed to have been opaque until about 350,000 years after the big bang. If the distant galaxies we can observe are found to be around this time, this would be strong evidence that the Benchmark Model is correct. To summarize, observing type 1a supernovae in distant galaxies can provide us with a lot of information on the early universe. This will help to confirm or dismiss current models of the universe, which is very important when it comes to understanding how the universe was created, and hypothesizing how the universe will end. Description of the Observations I will observe distant galaxies in the Hubble Deep Field for 70 orbits. Exposure times will be in the range from 330 seconds to 450 seconds. The exposure times are high because the light from distant galaxies is very dim, so the larger exposure times will allow us to see more light from the galaxies. Previous Hubble Deep Field images have exposure times between 330 and 450 seconds, which is why I chose that range. We want a high signal to noise ratio so we can make accurate measurements when analyzing the data. S/N of 10 or higher is optimal. Special Requirements These observations are TOO observations. The Hubble Deep Field contains approximately 3000 galaxies. It is estimated that there are about two supernovae per galaxy per century. 4

5 Since we will be observing approximately 3000galaxiesfor a year, we can expect to see about 60 supernovae. Therefore, the probability of occurrence is high, and we hope that we will get good data on at least 15 type 1a supernovae. Coordinated Observations Justify Duplications The reason for observing these distant galaxies that have already been observed is to analyze the new data to find new supernovae that can be studied in detail. The new data that will be analyzed will give us insight to many aspects in cosmology, and will help us confirm if our current models of the universe are correct. Previous HST Programs 5