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Keck treasury surveys add deep spectral data to "GOODS-North" field(Forwarded)
W.M. Keck Observatory
Kamuela, HI Media Contact: Laura K. Kraft, (808) 885-7887, December 31, 2003 KECK TREASURY SURVEYS ADD DEEP SPECTRAL DATA TO "GOODS-North" FIELD KAMUELA, Hawaii -- Two teams of astronomers based at the W. M. Keck Observatory and the University of Hawaii have completed deep new spectroscopic surveys of galaxies within the boundaries of the northern hemisphere field of the Great Observatories Origins Deep Survey (GOODS). The "Team Keck Treasury Redshift Survey" (TKS) is available to the public on the Web at: http://www2.keck.hawaii.edu/science/tksurvey/ while a parallel project led by University of Hawaii astronomers is available at http://www.ifa.hawaii.edu/~cowie/hhdf/acs.html These surveys will improve the value of existing GOODS images and will help researchers distinguish whether a faint blob seen in the GOODS images corresponds to a nearby star or a distant quasar, information that cannot be gleaned from space telescope pictures alone. "Our Team Keck survey follows in the footsteps of several key redshift surveys of the Hubble Deep Field-North completed with the Keck Low Resolution Imaging Spectrograph between 1996 and 2000, and is complemented by two similar projects, Len Cowie's DEIMOS survey and a sample of fainter targets observed with the Gemini North telescope," said Frederic Chaffee, Director of the W. M. Keck Observatory in Hawaii and participant in the TKS project. "We saw the need for this data set and because we have one of the few telescopes in the world that can do this, decided to donate the necessary observing time to the project." The GOODS effort is the most ambitious survey of the early universe ever conducted by the world's largest and most sensitive space- and ground-based telescopes. It includes data from the Spitzer Space Telescope, Hubble, Chandra, XMM-Newton and from the most powerful ground-based facilities in the world, such as the W. M. Keck Observatory. The GOODS project provides extremely deep, multi-wavelength observations for an exceptionally wide range of targets at varying distances in two regions of the sky, one in the northern hemisphere and one in the south. The GOODS-North survey spans a region 16 by 10 arcminutes in size, or about one-fourth the size of the full moon. The galaxy redshift surveys led by Team Keck the University of Hawaii team will be used in conjunction with other surveys for a great variety of applications for this intermediate- and high-redshift data set. University of Hawaii astronomer Len Cowie leads the Hawaii survey of the GOODS-North region and, with Amy Barger at the University of Wisconsin, has led efforts to identify these sources in deep X-ray and submillimeter observations of the same field. Prof. Cowie commented, "The GOODS fields take advantage of the new large cameras that survey larger areas of sky compared to the original Hubble Space Telescope studies. The wider fields allow us to study rare and exotic objects, such as X-ray bright galaxies with black holes at their nuclei or very heavily dust-enshrouded star-forming galaxies in the early universe. The spectra can also be combined with our distant galaxy searches to see the way that structure develops over the universe's first billion years." The TKS and University of Hawaii catalogs provide redshifts for 1946 objects in the GOODS-North field to magnitudes as faint as 24.4 (at 7,000 Angstroms). The survey's faintest targets are over twenty million times fainter than the dimmest objects visible to the unaided human eye. The objects with measured redshifts include 163 stars within our own Milky Way galaxy, plus galaxies and quasars as distant as redshift 5.19. The redshift and quality of each object's spectrum was independently classified by at least two team members to ensure consistency in the final catalog. In addition to the measured redshifts, the Keck and University of Hawaii teams will ultimately make all the spectra publicly available for downloading on their Web sites. Being able to analyze these spectra independently will help astronomers worldwide extract additional information that cannot be obtained from the redshifts alone, such as velocity dispersions, elemental abundances and dynamical measurements that enable meaningful comparisons between astronomical objects. These surveys were made possible through the use of one of the world's largest and most powerful astronomical survey instruments, the Deep Imaging Multi-Object Spectrograph (DEIMOS) installed on the Keck II 10-meter telescope. DEIMOS powers through surveys by taking high-resolution spectra of more than 130 objects at once, allowing the entire survey of over 2000 objects to be completed in the equivalent of five nights on the telescope. The surveys were conducted over a period of twelve nights in the spring of 2003 with additional observations provided by the Deep Extragalactic Evolutionary Probe (DEEP2) Survey team. Astrometry for the catalog was obtained by cross-correlating the United States Naval Observatory and Sloan Digital Sky Survey catalogs as well as radio observations from the VLA. For additional technical information, such as mask design, observing modes and data reduction techniques, please visit the TKS Web site at http://www2.keck.hawaii.edu/science/tksurvey/ The TKS team includes Gregory Wirth, principal investigator, and Paola Amico, Fred Chaffee, Al Conrad, Bob Goodrich, Grant Hill, James Lyke, Shui Kwok, Jeff Mader, David Le Mignant, and Hien Tran of the California Association for Research in Astronomy at the W. M. Keck Observatory in Hawaii. TKS collaborators include Christopher Willmer, Sandra Faber, and David Koo of the University of California Observatories/Lick Observatory and UC Santa Cruz, plus Marc Davis of UC Berkeley. University of Hawaii researchers Len Cowie, Amy Barger, Peter Capak, Esther Hu and Toni Songaila completed the University of Hawaii survey and also served as co-investigators in the TKS program. The Keck team will also participate in CATS, the Center for Adaptive Optics Treasury Survey, which will use adaptive optics to produce detailed, near-infrared images of these same galaxies in the GOODS-North field. The TKS project was funded in part by the National Science Foundation's "Small Grants for Exploratory Research" initiative, under Grant No. AS-0331730 and the University of Hawaii effort by NASA and NSF grants primarily. Any opinions, findings and conclusions or recommendations expressed herein do not necessarily reflect those of the National Science Foundation or NASA. The W. M. Keck Observatory is managed by the California Association for Research in Astronomy, a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. Together, these groups manage the world's largest optical and infrared telescopes. Visit the observatory online at http://www.keckobservatory.org/ IMAGE CAPTIONS: [Image 1: http://www2.keck.hawaii.edu/news/tksurvey/ktrs12big.jpg (80KB)] A sample image showing a small part of the GOODS-North field as seen in red light. The green markings represent DEIMOS slits that were machined according to the position of galaxies in the GOODS-North field. The DEIMOS instrument enables astronomers to acquire high-resolution spectra of more than 130 objects in a single exposure. Image Credit: W. M. Keck Observatory [Image 2: http://www2.keck.hawaii.edu/news/tks...echart_dec.jpg (122KB)] A "pie diagram" map showing how the galaxies in the survey are distributed in space. Note the numerous "walls" and "voids" observed in this field due to clustering of galaxies. Image Credit: W. M. Keck Observatory [Image 3: http://www2.keck.hawaii.edu/news/tks...fig-z-vs-R.jpg (120KB)] This diagram plots the distance of galaxies (as measured by their redshift, z) versus their brightness (magnitude, in which higher numbers indicate fainter objects). The faintest objects that can be seen with the unaided human eye are over 15 million times brighter than the faintest objects captured in this Keck survey. Image Credit: W. M. Keck Observatory [Image 4: http://www2.keck.hawaii.edu/news/tksurvey/fig-zdist.jpg (77KB)] This plot shows the number of galaxies as a function of redshift in the Keck survey. Redshifts, which are proportional to a galaxy's distance from Earth, were measured from emission lines (Hydrogen Balmer series, [N II], [S II], [O III], [O II]) and Calcium (H and K) absorption features in galaxy spectra. Image Credit: W. M. Keck Observatory |
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