Transcript A GALEX and NDWFS Investigation of Star Forming Galaxies at z=1 and 2 Charles G.

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
The Galaxy Evolution Explorer (GALEX)
• Launched April 28, 2003
• Imaging in two UV bands
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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 U
observations (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 calculated
from filter redward of
Lyman break
• Fainter z=2 galaxies
selected against, but
bright z=1 galaxies would
be 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 APJL
L* 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 formation
rates from LBGs to present-day
starbursts
(see also Arnouts et al. 2004 in
GALEX edition of ApJL)
• Mean extinction implied by
UV slope is
E(B-V)~0.1 for z=1
E(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
June 2, 2004
GALEX-NDWFS Investigation of
Galaxies at z=1-2