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20110414 Ryu Jinhyuk GALEX, THE ULTRAVIOLET SPACE TELESCOPE Contents Introduction Why do we want to observe UV wavelength? Previous UV missions About GALEX Instruments Schematic view Detector Grism Surveys Baseline surveys Legacy surveys The fate of GALEX Sciences done by GALEX Ultraviolet astronomy Temperatures between 104 – 105 K HOT stars (young and old) Many high excitation lines and resonance lines are observed in UV Ex) Ly α 1215; C IV 1550; C III] 1909 (ref: http://www.astro.virginia.edu/class/whittle/astr553/Topic15/Lecture_15.html, Mark Whittle, Virginia) Previous UV missions (ref : http://astronomy.ua.edu/keel/techniques/spacetbl.html, William Keel, Alabama) OAO-4 (Copernicus) Astronomical Netherlands Satellite (ANS) 1992. multiband all-sky survey, deep ecliptic survey. Spectroscopy possible. Operated a program of pointed observations following sky survey, through January 2001. Far-Ultraviolet Spectroscopic Explorer (FUSE) 1990 and 1995. Extreme Ultraviolet Explorer (EUVE) NASA-ESA-UK. 1978. 45-cm. spectrometers (1200 - 2000, 2000 - 3200 Å). 18-year lifetime. Winds from hot stars, coronae of cool stars, hot stars in cold galaxies, variability mapping of AGN emission regions. Astro 1 and 2: UV Intensified Telescope (UIT), Hopkins UV Telescope (HUT), Wisconsin UV Photo Polarimetry Experiment (WUPPE). 1974. 22-cm, photometry (1550 - 3300 Å). International Ultraviolet Explorer (IUE) 1972 – 1981. 80-cm. Grating spectrometer with photomultiplier. 1999 – 2007. High-resolution spectroscopy from 912 - 1150 Å. Astron 1983 – 1989. Soviet-French UV spectrometer. Very high orbit (2000 X 200,000 km). GALEX? GALaxy Evolution eXplorer All-sky UV imaging and objective-grating survey since 2003 Tracing the cosmic history of star formation at modest redshifts Led by CalTech Yonsei University is supporting science calibration and testing and supports science operations and science analysis. The first mission was planned as a 29-month mission. Instruments 50cm Ritchey-Chretien telescope Primary & secondary mirrors are hyperbolic Grism Dichroic beam splitter Two Multi Anode Microchannel Array (MAMA) detectors Instruments Dichroic beam splitter Mean reflectance of 61% over the 1400-1700Å Mean transmittance of 83% over the 1800-2750Å Blue-edge filter coated on MgF2 10% rejection of the OI 1304 airglow line Red-blocking filter on the NUV folding mirror An edge at 2800Å yields an additional factor of 10-20% rejection of the NUV zodiacal light background. Multi Anode Microchannel Array Grism NUV FUV CaF2, 75/mm Using spectral order 1 2 Wedge angle Spectral resolution ~20Å ~8Å Corresponding R ~100 ~200 1º.37 Blaze angle 2º.33 Mission Surveys 5 baseline surveys Complete in 2007 Survey Exposure Time Sky Coverage (deg2) Depth (mAB) GR2/3 tiles GR4 tiles All-sky Imaging (AIS) 100 26000 20.5 15721 28000** Medium Imaging (MIS) 1500 1000 23.5 1017 1615 Deep Imaging (DIS) 30000 80 25.0 165 193 Nearby Galaxy Survey (NGS) 1500 300 28* 296 433 Medium Spectroscopic (MSS) 150000 5 22 3 5** *surface density (mag/sq arcsec) **projected All-sky Imaging Survey (AIS) Survey All-sky Imaging (AIS) Exposure Time Sky Coverage (deg2) Depth (mAB) GR2/3 tiles GR4 tiles 100 26000 20.5 15721 28000** 12 positions in one orbit |b| < 20º regions are partially covered 28269 individual pointing's (GR 4/5) Medium Imaging Survey (MIS) Survey Exposure Time Sky Coverage (deg2) Depth (mAB) GR2/3 tiles GR4 tiles Medium Imaging (MIS) 1500 1000 23.5 1017 1615 This survey covers the SDSS spectroscopic footprint. The MIS has been extended to cover the 2dFGRS and the WiggleZ project. Deep Imaging Survey (DIS) Medium Spectroscopic Survey(MSS) Survey Exposure Time Sky Coverage (deg2) Depth (mAB) GR2/3 tiles GR4 tiles Deep Imaging (DIS) 30000 80 25.0 165 193 Medium Spectroscopic (MSS) 150000 5 22 3 5** Targets are chosen to have extensive corollary data from other surveys. Ex) COSMOS, DEEP, ELAIS, CDFS, etc. Covering 5 square degrees of fields observed as a part of the DIS. Nearby Galaxy Survey (NGS) Survey Exposure Time Sky Coverage (deg2) Depth (mAB) GR2/3 tiles GR4 tiles Nearby Galaxy Survey (NGS) 1500 300 28* 296 433 The core of NGS targets the 71 galaxies included in the SINGS. Legacy Surveys Survey Exposure Time Sky coverage (deg2) Galactic Cap Survey SDSS Galactic cap footprint 1500 20000 Legacy Deep Survey PS-1, M31, SDSS 30000 100 Milky Way Survey SEGUE 1500 5000 Legacy Spectroscopy Project SDSS 150000 20 Deep Galaxy Survey Nearby Galaxies 15000 100 300000 7 Ultra Deep imaging Survey Current status At 4/9/2010, NASA's Jet Propulsion Laboratory announced that the FUV detector shorted out. Despite of that, the GALEX still moves on with the NUV detector. Current data release version is the GR6. There are no plans for a GR7. However, plans for a final processing of all products and construction of catalogs are under active discussion. The fate of GALEX Originally, the first mission was planned as a 29month mission, but NASA recommended to extend the lifetime. Legacy surveys and Guest Investigator programs (2005 – 2010, 6 cycles) begun at that time. Based on the 2010 Panel's recommendations NASA has announced that observations will be terminated on September 30, 2012. NASA intends to fund all previously approved programs (excluding those canceled because they could not be done without the FUV detector). The last mission? Observing the available sky to "MIS depth" (mAB ~ 22.5, ~1500 sec exposure), or 1-orbit exposures. About 16,000 deg2 are not yet imaged but can be observed safely by GALEX. Only NUV detector is available now. Publications using GALEX Status of papers (~Feb 2008) Instrument – 7 Report / Review – 12 ISM – 12 Galaxy – 169 Cosmology – 14 Star – 24 Star clusters – 9 GRB – 4 Catalog / Survey – 16 Misc - 5 TOTAL - 272 Top 5 citation Martin et al. 2005, ApJ, The Galaxy Evolution Explorer: A Space Ultraviolet Survey Mission (460) We give an overview of the Galaxy Evolution Explorer (GALEX), (...) GALEX is performing the first space UV sky survey, including imaging and grism surveys in two bands (1350-1750 and 1750-2750 Å). The surveys include an all-sky imaging survey (mAB~=20.5), a medium imaging survey of 1000 deg2 (mAB~=23), a deep imaging survey of 100 deg2 (mAB~=25), and a nearby galaxy survey. Spectroscopic (slitless) grism surveys (R=100-200) are underway with various depths and sky coverage. (...) We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the relationship of the UV and global star formation rate in local galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the redshift range 0<z<2 and probe the physical drivers of star formation in galaxies. The GALEX mission includes a guest investigator program, supporting the wide variety of programs made possible by the first UV sky survey. Top 5 citation Hopkins & Beacom, 2006, ApJ, On the Normalization of the Cosmic Star Formation History (433) (...) The data show a compellingly consistent picture of the SFH out to redshift z~6, with especially tight constraints for z<~1. We fit these data with simple analytical forms and derive conservative uncertainties. Since the z<~1 SFH data are quite precise, we investigate the sequence of assumptions and corrections that together affect the SFH normalization to test their accuracy, both in this redshift range and beyond. As lower limits on this normalization, we consider the evolution in stellar and metal mass densities, and supernova rate density, finding it unlikely that the SFH normalization is much lower than indicated by our direct fit. As a corresponding upper limit on the SFH normalization, we consider the Super-Kamiokande limit on the electron antineutrino (νe) flux from past core-collapse supernovae, which applies primarily to z<~1. (...) The traditional Salpeter IMF, assumed for convenience by many authors, is known to be a poor representation at low stellar masses (<~1 Msolar), and we show that recently favored IMFs are also constrained. (...) To resolve the outstanding issues, improved data are called for on the supernova rate density evolution, the ranges of stellar masses leading to corecollapse and type Ia supernovae, and the antineutrino and neutrino backgrounds from core-collapse supernovae. Top 5 citation Le Floc'h et al. 2005, ApJ, Infrared Luminosity Functions from the Chandra Deep Field-South: The Spitzer View on the History of Dusty Star Formation at 0 <~ z <~ 1 (405) We analyze a sample of ~2600 Spitzer MIPS 24 μm sources brighter than ~80 μJy and located in the Chandra Deep Field-South to characterize the evolution of the comoving infrared (IR) energy density of the universe up to z~1. (...) We then determine an estimate of their total IR luminosities using various libraries of IR spectral energy distributions. We find that the 24 μm population at 0.5<~z<~1 is dominated by ``luminous infrared galaxies'' (i.e., 1011 Lsolar<=LIR<=1012 Lsolar) (...) we find very strong evolution of the contribution of the IR-selected population with lookback time. (…) we find considerable degeneracy between strict evolution in luminosity and a combination of increases in both density and luminosity [L*IR~(1+z)3.2+0.7-0.2, φ*IR~(1+z)0.7+0.2-0.6]. (...) Our results imply that the comoving IR energy density of the universe evolves as (1+z)3.9+/0.4 up to z~1 and that galaxies luminous in the infrared (i.e., L >=1011 IR Lsolar) are responsible for 70%+/-15% of this energy density at z~1. Taking into account the contribution of the UV luminosity evolving as (1+z)~2.5, we infer that these IR-luminous sources dominate the star-forming activity beyond z~0.7. (…) Top 5 citation Faber et al. 2007, ApJ, Galaxy Luminosity Functions to z~1 from DEEP2 and COMBO-17: Implications for Red Galaxy Formation (431) The DEEP2 and COMBO-17 surveys are compared to study luminosity functions of red and blue galaxies to z~1. (...) After z~1, M*B has dimmed by 1.2-1.3 mag for all colors of galaxies, φ* for blue galaxies has hardly changed, and φ* for red galaxies has at least doubled (our formal value is ~0.5 dex). Luminosity density jB has fallen by 0.6 dex for blue galaxies but has remained nearly constant for red galaxies. These results imply that the number and total stellar mass of blue galaxies have been substantially constant since z~1, whereas those of red galaxies (near L*) have been significantly rising. To explain the new red galaxies, a ``mixed'' scenario is proposed in which star formation in blue cloud galaxies is quenched, causing them to migrate to the red sequence, where they merge further in a small number of stellar mergers. (…) The red sequence therefore likely builds up in different ways at different times and masses, and the concept of a single process that is ``downsizing'' (or upsizing) probably does not apply. Our claim in this paper of a rise in the number of red galaxies applies to galaxies near L*. Accurate counts of brighter galaxies on the steep part of the Schechter function require more accurate photometry than is currently available. Top 5 citation Pérez-González et al. 2005, ApJ, Spitzer View on the Evolution of Star-forming Galaxies from z = 0 to z ~ 3 (288) We use a 24 μm-selected sample containing more than 8000 sources to study the evolution of star-forming galaxies in the redshift range from z=0 to z~3. (...) The derived redshift distribution of the sources detected by our survey peaks at around z=0.6-1.0 (the location of the peak being affected by cosmic variance) and decays monotonically from z~1 to z~3. (...) The cosmic star formation rate (SFR) density goes as (1+z)4.0+/-0.2 from z=0 to 0.8. From z=0.8 to z~1.2, the SFR density continues rising with a smaller slope. At 1.2<z<~3, the cosmic SFR density remains roughly constant. The SFR density is dominated at low redshift (z<~0.5) by galaxies that are not very luminous in the infrared (LTIR<1011 Lsolar, where LTIR is the total infrared luminosity, integrated from 8 to 1000 μm). The contribution from luminous and ultraluminous infrared galaxies (LTIR>1011 Lsolar) to the total SFR density increases steadily from z~0 up to z~2.5, forming at least half of the newly born stars by z~1.5. Ultraluminous infrared galaxies (LTIR>1012 Lsolar) play a rapidly increasing role for z>~1.3.