Jeff Cooke
Jeff Cooke

Centre for Astrophysics & Supercomputing, Swinburne University of Technology
PO Box 218, Mail number H39, Hawthorn, VIC 3122 Australia
office: +61 3 9214 5392 -- fax: +61 3 9214 8797 -- US phone: 619 913 2850 -- email: jcooke@astro.swin.edu.au

     
  Office:
AR 312
Calendar
 

Main areas of research:

Galaxy evolution, galaxy interactions, absorption-line systems, high redshift supernovae

Press releases:
The most distant supernovae
LBG-2377
Check this out (I think I recognize #1)!
Top 10 Most Important Supernovae
(for the original site - click here)

Brief descriptions of a few of the projects that have been keeping me busy:

Detection of z > 2 supernovae - I pioneered a technique to detect supernovae (SNe) in z > 2 Lyman break galaxies (LBGs) by exploiting the exceptional properties of type IIn SNe (Cooke 2008a). Previously, core-collapse supernovae had not been detected beyond z ~ 0.7. Detections at z ~ 2 enable the measurement of the high-redshift supernova rate during the epoch of peak star formation in the universe and provide a new avenue to explore the feedback processes that affect galaxy formation and the enrichment of the interstellar and intergalactic medium. In addition, high-redshift type IIn SN detections offer the tantalizing possibility to measure the form of the high-redshift stellar initial mass function directly for the first time.
I obtained deep spectroscopy of the first 10 z ~ 2 SNe in the Canada-France-Hawaii Telescope Legacy Survey Deep fields (z = 1.9 - 2.4) using the LRIS and DEIMOS instruments on the Keck telescopes. The first two are presented in (Cooke et al. 2009a). Nine of the z ~ 2 SNe show ultraviolet (UV) emission lines intrinsic to type IIn SNe, with a few having strong Lyman alpha emission (Cooke et al. 2011a in prep.). The recently discovered tenth event is a UV luminous SNe that exhibits a light curve and spectrum reminiscent of lower redshift events considered to be pair-instability supernovae (PISNe). Thus, this SN may be the death of a star similar to the very first generation of stars ( population III stars) also believed to result in PISNe. Such UV luminous SNe should be detectable to z ~ 4 in existing surveys and to z ~ 6 in upcoming surveys. Overall, these data demonstrate the power of this technique and the ability to detect, confirm, and study supernovae at redshifts higher than previously thought possible.

Lyman break galaxy interactions at z ~ 3 - I am leading several related projects that investigate the observed and predicted behavior of close and interacting LBGs at z ~ 3. We are using deep Keck optical imaging and spectroscopic surveys (Cooke et al. 2005), deep Palomar and Large Binocular Telescope infrared spectroscopy, and an analysis of a high resolution hybrid numerical/analytical cosmological simulation (Berrier & Cooke 2011) to examine spectroscopic interacting galaxy pairs and spectro-photometric close pairs. Relationships found between spectroscopic properties and pair separation (Cooke et al. 2010) and the clustering behavior of LBG sub-types (Cooke & Omori 2011b, in prep.), is providing valuable insight regarding the morphological changes and triggered star formation LBGs encounter from interactions, connections between restframe UV and optical properties, the LBG merger rate, and implications on assembly histories from spectroscopic indicators. The discovery of the luminous LBG-2377 (image on right) has provided some key data for this work (Cooke et al. 2008b).

Broadband selection of Lyman alpha emitters - Complementary to the above work, I developed a technique to pre-select LBGs with desired spectroscopic properties and Lyman alpha emitters (LAEs) to high efficiency using broadband imaging alone (Cooke 2009b). This technique has enabled the clustering studies discussed above that would be nearly impossible otherwise given the large number of LBG spectra that would be required (~100,000). The number of LAEs detected using this technique is an order of magnitude larger than previously possible via narrow-band and blind spectroscopic surveys. In addition, the larger redshift path accessible enables the LAE correlation function and the LAE cross-correlation with LBGs to be measured to high precision.

Relationships between star forming galaxies and QSO absorption-line systems - I have conducted two large imaging and spectroscopic surveys for high redshift (z = 2 - 5) LBGs and damped Lyman alpha systems (DLAs). These surveys exploit the sensitivity and field-of-view of the Keck LRIS and DEIMOS, Palomar COSMIC, MMT MegaCam, and Subaru SuprimeCam instruments (Cooke et al. 2005, 2011c in prep.). A primary goal of these surveys is to measure the 3-D distribution of LBGs and DLAs at z ~ 3 and z ~ 4 via the spatial correlation and cross-correlation functions. The measurements from these surveys help determine fundamental properties such as galaxy bias, mass, luminosity, and evolutionary paths. The first measurement of the mass of z ~ 3 DLAs is presented in (Cooke et al. 2006a, 2006b). The larger, wide-field z = 2 - 5 survey will improve the statistics and probe extended sightlines via bright LBGs to provide, for the first time, the geometry of DLAs at high redshift.

THE LATEST - I am finishing up an exciting project to measure the mean near UV spectrum and dispersion of type Ia SNe Cooke et al. 2011d). Type Ia SNe are excellent standard candles and have been used to show that the expansion rate of the universe is accelerating. To probe the universe at early times, the necessary high redshift observations sample restframe UV wavelengths. Recent work has found a dispersion in the near UV which could have a important impact on future surveys. This project utilizes the Palomar Transient Factory to detect type Ia SN events as early as 16 days before they reach maximum brightness. We use multiple large aperture telescopes, such as the Palomar 5m, VLT 8m, Gemini 8m, and Keck 10m, to spectroscopically confirm and phase the events. Finally, we use the Hubble Space Telescope to obtain near UV and optical spectra.

Click here to access the ADS link displaying a list of articles describing some of my work.

 

 


Welcome to my office


A false color (negative) image of interacting Lyman break galaxies (termed LBG-2377) comprise the brightest LBG at z ~ 3 known to date (Cooke et al. 2008). These "embryo" galaxies show evidence that they are merging and provide information on the physical properties and formation processes of galaxies about 11.4 billion years ago, when the universe was only 15% its current age.

LBGs, like those above, are visible because they are undergoing a burst of star formation. One cause of this burst may be the merging of galaxies, as is the case for the much closer galaxies NGC 4038 and NGC 4039 (image to the right) known as the Antennae Galaxies.

The search for z ~ 2 Type IIn supernovae in the Deep component of the CFHTLS has spectroscopically confirmed 10 to date, with more to come.

The images directly to the right illustrate the first step in finding these distant objects. Each frame shows the same tiny section of a large one-square-degree image over three consecutive years and is centered on a z ~ 2 galaxy that was discovered to host a supernova. The frames consist of an entire year's worth of images stacked together to better reveal these faint objects.

Below the three images is the 2004 image with the constant light from the galaxies subtracted away, revealing the supernova.

The 10 supernovae lay between z = 1.9 - 2.4. Deep spectroscopy with the Keck telescopes is used for confirmation and study.

With these discoveries, we are witnessing light from explosions that happened nearly 11 billion years ago. Such detections are crucial in understanding early stellar and galaxy formation processes.
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The Hubble Space Telescope

The Milky Way can be seen, as well as two of our closest companion galaxies, the Large and Small Magellenic Clouds, in this long-exposure image of the 4 meter telescope at the CTIO located in the Southern Hemisphere (Chile).
Work
 
  Astronomy 110
Physics 20A  
  Physics 7D
Curriculum Vitae
 
  Astro Grad Seminar
Centre for Astrophysics & Supercomputing
Swinburne
 
  Caltech Astronomy Department
Center for Cosmology
UC Irvine
 
  Center for Astrophysics and Space Sciences
UC San Diego
W. M. Keck Observatory  
  Palomar Observatory