High Redshift Simulations using the GALEX Ultraviolet Images of Nearby Galaxies Bum-Suk Yeom 1, Young Kwang Kim 1,2, Soo-Chang Rey 1, Young Hoon Joe 3, and Armando Gil de Paz 4 1 Department of Astronomy and Space Science, Chungnam National University, Daejeon , Korea, 2 Korea Astronomy and Space Science Institute, Daejeon , Korea 3 Center for Space Astrophysics, Yonsei University, Seoul , Korea 4 Departamento de Astrofisica, Facultad de CC. Fisicas, Universidad Complutense de Madrid, E Madrid, Spain SDSS-KSG Workshop, 18 – 20 February 2008

Motivation Data and Samples Simulation Procedures Results Quantitative Morphological Analysis Summary Future Works Outline

Galaxy morphology plays an important role in the assessment of the evolutionary state of galaxies (Bohlin et al. 1991; Giavalisco et al. 1996) Prediction of optical-band morphologies at high redshift → Ultraviolet (UV) images of local galaxies with various morphologies (Bohlin et al. 1991; Giavalisco et al. 1996; Kuchinski et al. 2001; Marcum et al. 2001; Papovich et al. 2003, Lotz et al. 2006) Motivation

Previous works (Bohlin et al. 1991; Giavalisco et al. 1996; Burgarella et al. 2001; Kuchinski et al. 2001; Marcum et al. 2001; Papovich et al. 2003; Lotz et al. 2006) –UIT (Ultraviolet Imaging Telescope), FOCA, HST/FOC (Faint Object Camera) –Used small size of the samples –Not representative of the overall population of galaxies in the Local Universe To understand the morphology of galaxies at high-redshift → Simulated optical images at high redshift using more diverse and high-quality nearby galaxies obtained through the Galaxy Evolution Explorer (GALEX) UV observations Quantitative morphological analysis → Concentration (C) parameter Motivation

GALEX : Mission and Instrument –Performed the first space ultraviolet (UV) sky survey –Satellite: Launched by Pegasus-XL on April 28th 2003 Circular orbit, altitude: 700 km, inclination: 29°, period: 98 min –Telescope: 50 cm modified Ritchey-Chrétien –Instrument: Simultaneous imaging in two UV bands (FUV & NUV; ~ 1516 & 2267 Å) Circular FOV of 1.2° in diameter FWHM (FUV=4.5˝; NUV=6˝) Pixel scale : 1.5˝/pixel Data and Samples M81 & M82

Galaxy samples : 1034 galaxies –Galaxies in the GALEX Nearby Galaxy Survey (NGS) plus galaxies obtained as part of other GALEX imaging surveys (Gil de Paz et al. 2007) –Galaxies with the overall population of galaxies in the Local Universe –Ellipticals/Spirals/Irregulars (23%/61%/8%) Data and Samples (Yeom et al in preparation)

Simulation Procedures Artificially redshift our UV images into the HST ACS (Advanced Camera for Surveys) observations (HUDF, Hubble Ultra Deep Field) –General prescription outlined by Giavalisco et al. (1996) –Assumed zero evolutionary effects of stellar population

Results GALEX NUV and artificially redshifted images of M101 (z = 0.0, 0.9, 1.6, 2.4, 3.0 Wavelength = 2267, 4307, 5894, 7708, 9068 Å)

Results GALEX NUV and simulated images with various morphology –Simulated galaxies are detected 30 percent of our sample at z~3

Quantitative Morphological Analysis To study the quantitative morphological analysis at high-z galaxies → Concentration (C) parameter → C index is very stable against a spatial resolution degradation (Bershady et al. 2000) Concentration (C) parameter and results –Total flux is the within 2.5 Kron radius (Kron 1980; Graham & Driver 2005) of the galaxy’s center (Kent 1985; Bershady et al. 2000)

Quantitative Morphological Analysis

(Kent 1985; Bershady et al. 2000) Quantitative Morphological Analysis

Simulated the unprecedented nearby galaxies from the GALEX UV samples with various morphologies to investigate the optical-band morphologies seen in HST Many of the optical morphological features are still clearly observed at moderate redshift (z~1.6) At high redshift (z~3) –Most of the simulated galaxies are barely detected (30 percent of our sample) –Simulated spiral galaxies can be mistaken for S0 or E types Measurement of the morphological parameters (Concentration index, C) –E/S0 → concentration index is decreasing as a function of redshift –Spirals and Irregulars → little change globally as a function of redshift Summary

Future Works Measurement of the various morphological parameters –Asymmetry (A) index, Gini (G) coefficient, etc. Simulation of the nearby galaxies using the Swift UV data (Roming et al. 2005) with a higher resolution (0.5″/pixel)

Thank you !

Galaxy samples : 1034 galaxies –Galaxies in the GALEX Nearby Galaxy Survey (NGS) plus galaxies obtained as part of other GALEX imaging surveys (Gil de Paz et al. 2007) –Galaxies with the overall population of galaxies in the Local Universe –Ellipticals/Spirals/Irregulars (23%/61%/8%)