Hubble Space Telescope
Cycle 11 General Observer Proposal
Supernovae in Distant Galaxies
Principal Investigator: Mr. Anthony Martorano
Institution: Stony Brook University
USA/NY
Electronic mail: anthony.martorano@stonybrook.edu
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
the galaxies within the Hubble Deep Field. I plan to use the ACS for optical imaging to detect
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
Mr. Anthony Martorano
Supernovae in Distant Galaxies
Hubble parameter at the time that the supernova took place.
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Mr. Anthony Martorano
Supernovae in Distant Galaxies
Investigator
PI: Mr. Anthony Martorano
Total number of investigators: 1
Observing Summary:
Target
RA
HUBBLE
12 36 49.4
DEEP FIELD
DEC
62 12 58
Institution
Stony Brook University
V
Unknown
3
Configuration,mode,aperture
spectral elements
ACS/WFC,COS/FUV
IMAGING Unknown
Grand total orbit request
Country
USA/NY
Total
orbits
70
70
Flags
TOO
Mr. Anthony Martorano
Supernovae in Distant Galaxies
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.
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Mr. Anthony Martorano
Supernovae in Distant Galaxies
Since we will be observing approximately 3000 galaxies for 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
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