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Star Formation Rate in Three High-Redshift Galaxy Clusters: A Contribution to the Study of Galactic Evolution by: Vinay Patel and Matt Pellegrino


 * Questions they had...
 * How will our galaxy evolve in response to the surrounding galaxies of the Local Group?
 * What is the ultimate fate of our own galaxy?
 * This led to the development of the SFR in redshift galaxies project in our class!


 * Studying galaxy clusters
 * current focus is on the evolution of the cluster and its galactic member
 * these clusters have been studied mainly through observations
 * Butcher-Oemler effect: the tendency of galaxy colors to be bluer at higher redshifts
 * causes of cluster galaxy evolution...
 * mergers
 * strong galacy interactions
 * harassment
 * gas stripping
 * strangulation
 * STAR FORMATION!
 * EDisCS Sample: European Southern Observatory Large Program aimed at studying galaxy cluster evolution
 * Tools
 * Very Large Telescope(VLT)
 * New Technology Telescope(NTT)
 * Focal Reducer Scpetrograph(FORS2)
 * Goals of program
 * complete ultraviolet to near infrared SEDs
 * study galaxy morphology as a function of SED
 * study cluster luminosity functions(LF) as a function of redshift and cluster properties
 * estimate cluster masses through gravitational lensing
 * The Project
 * used data from the Spitzer Space Telescope
 * infrared telescope in orbit around the sun
 * because it uses infrared technology, it isn't limited by extinction and can detect 10 to 100 times more star formation that other telescopes
 * the light from stars and galaxies is often absorbed by dust and gas surrounding the stars and is re-emitted as heat, which prevents the light from being detected by most telescopes; Spitzer allows us to see this re-emitted infrared light and infer the presence of stars and galaxies which surround and heat the dust
 * and thus, astronomers are able to probe optically-blocked galaxies that were previously invisible and measure their flux
 * determined star formation rates from three high redshift galaxies: CL1037, CL1227, CL1232
 * Research
 * Three Pieces
 * 5 month period of preparation
 * 3 day meeting at the Spitzer Space Center in Pasadena, California
 * July 26, 2006-July 28, 2006
 * analyzed data and learned how to calculate star formation
 * calculated lumnosity and generate spectral energy distributions(SEDs)
 * from these five SED lines, they were able to use that ratio between the total infrared luminosity and the luminosity at one specific wavelength, which allowed for the conversion from the rest-frame luminosity to the total infrared luminosity, and finally SFR!
 * they calculated star formation for each of the five SED lines and averaged them to find the SFR for each of the galaxies that were observed
 * 8 month period of analyzing data that had been collected
 * Methodology
 * to calculate the SFR of CL1037, CL1227, and CL1232...
 * identify the clusters members
 * done by calculating the redshift of wach galaxy and then comparing this to the redshift of the cluster
 * calculating redshift
 * spectroscopically: calculated using the spectra of the cluster members
 * photometrically: calculated shift in emission lines to accuarately estimate the redshift of a galaxy; not as accurate as spectroscopic redshift
 * convert 24 micron flux of those cluster members to luminosity at a specific, rest-frame wavelength
 * model-guided extrapolation from luminosity at the rest-frame wavelength to total infrared luminosity
 * convert the total infrared luminosity to SFR
 * Results
 * CL1037
 * average SFR per cluster is 86.0574 M/yr
 * total SFR of these forty-five cluster members is 3872.59 M/yr
 * SFR by galaxy type
 * elliptical has average SFR of 28.4975 M/yr
 * lenticular has average SFR of 312.061 M/yr
 * spiral has average SFR of 81.2230 M/yr
 * irregular has average SFR of 42.2799 M/yr
 * CL1227
 * average SFR per cluster is 74.9301 M/yr
 * total SFR of these twenty-six cluster members is 1948.18 M/yr
 * SFR by galaxy type
 * elliptical has average SFR of 34.1923 M/yr
 * lenticular has average SFR of 30.1390 M/yr
 * spiral has average SFR of 90.4489 M/yr
 * irregular has average SFR of 28.7295 M/yr
 * CL1232
 * average SFR per cluster is56.6268 M/yr
 * total SFR of these fifty-five cluster members is 3114.48 M/yr
 * SFR by galaxy type
 * elliptical has average SFR of 63.5693 M/yr
 * lenticular has average SFR of 30.3968 M/yr
 * spiral has average SFR of 53.3709 M/yr
 * irregular has average SFR of 90.1752 M/yr