A GALEX and NDWFS Investigation of Star Forming

Galaxies at z=1 and 2

Charles G. Hoopes, Timothy M. Heckman (JHU)

Buell T. Jannuzi, Arjun Dey, Michael J. I. Brown, Alison Ford (NOAO)

and Davis Schiminovich (Columbia)

June 2, 2004

June 2, 2004 GALEX-NDWFS Investigation of Galaxies at z=1-2

The Galaxy Evolution Explorer (GALEX)

• Launched April 28, 2003• Imaging in two UV bands

– FUV: λ=1516Å, Δλ=268Å– NUV: λ=2267Å, Δλ=732Å– Spatial resolution ~5”– FOV ~1.2 deg2

• Slitless Spectroscopy– 1350-2800Å– Spectral resolution R=80-300

• Conducting several surveys of varying depth and area, as well as pointed observations

June 2, 2004 GALEX-NDWFS Investigation of Galaxies at z=1-2

Mapping the History of Star Formation in the Universe

• SF history of universe mapped out to z>5

• Relatively little known about z<3

• Different techniques used for different redshift intervals

(From Giavalisco 2002 and Barger et al 2000)

June 2, 2004 GALEX-NDWFS Investigation of Galaxies at z=1-2

Lyman Break Galaxies at z>3: U-band dropouts

June 2, 2004 GALEX-NDWFS Investigation of Galaxies at z=1-2

Lyman Break Galaxies at z>3: U-band dropouts

June 2, 2004 GALEX-NDWFS Investigation of Galaxies at z=1-2

GALEX Observations of Bootes Region• Deep Imaging Survey

– 80 deg2, including the 9 deg2 Bootes region of the NDWFS.

– Limiting magnitude AB=25– 1 deg2 observed in 2003 (the “00” field - 43 ksec)– 2 more deg2 coming this week

• Ultra-Deep Imaging Survey– 4 deg2, including the “00” field in Bootes– Limiting magnitude AB=26– 200 ksec planned (100 in 2004)

• Deep Spectroscopic Survey– 2 deg2, including the “00” field– Limiting magnitude AB=22.5-24

Supplemented NDWFS data with deep Uobservations (AB=26) in the “00” field

June 2, 2004 GALEX-NDWFS Investigation of Galaxies at z=1-2

z=1: FUV Dropouts

• SExtractor (Bertin & Arnouts 1996) dual band catalog in NUV/FUV matched with U-band

• Spatial resolution difference (~5” for GALEX, <1” for U-band) creates identification problems

• Compare colors to model colors of redshifted starburst spectra (following Steidel et al.)

June 2, 2004 GALEX-NDWFS Investigation of Galaxies at z=1-2

z=2: NUV Dropouts

• SExtractor single-band catalogs matched in Bw, U, NUV

• Spatial resolution problems remains

• Compare colors to model colors of redshifted starburst spectra (following Steidel et al.)

June 2, 2004 GALEX-NDWFS Investigation of Galaxies at z=1-2

UV Luminosity• Luminosities calculatedfrom filter redward of Lyman break

• Fainter z=2 galaxiesselected against, but bright z=1 galaxies wouldbe detected

• Indicates that most luminous galaxies at z=2 have faded by z=1

L* at z=0 from Treyer et al. 2004 in GALEX edition of APJLL* for LBGs from Giavalisco 2002

June 2, 2004 GALEX-NDWFS Investigation of Galaxies at z=1-2

Star Formation and Extinction

• We may be seeing the transition in star formationrates from LBGs to present-daystarbursts(see also Arnouts et al. 2004 inGALEX edition of ApJL)• Mean extinction implied byUV slope isE(B-V)~0.1 for z=1E(B-V)~0.2 for z=2

(but there is a degeneracy between redshift and UV slope,and only sensitive to E(B-V)<0.4)

June 2, 2004 GALEX-NDWFS Investigation of Galaxies at z=1-2

Future Work

• Improved matching techniques, photo-z

• Further GALEX observations

• Spitzer observations of this region are planned

• Spectroscopic follow up

June 2, 2004 GALEX-NDWFS Investigation of Galaxies at z=1-2

Summary

• GALEX-NDWFS collaboration will shed light on galaxy evolution at z=1-2

• Large amount of GALEX data in the Bootes region is coming

• Initial results show the vigorous star formation of Lyman Break Galaxies fading from z=2 to z=1