Download Deep fields around bright stars (“Galaxies around Stars”)

Deep fields around bright stars
(“Galaxies around Stars”)
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Scientific context: the morphological
evolution of faint field galaxies
Near-IR observations ground-based
observations with AO:
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PUEO/CFHT deep field observations
NACO/VLT Science Verification phase: the
Casertano Deep field
Discussion and prospects for PUEO NUI
G. Soucail (OMP)
Scientific context
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Faint galaxies: general scheme for
galaxy formation and evolution
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growth of structures by accretion and
merging of sub-halos of dark matter
star formation in the densest central
regions
The morphological evolution of
galaxies
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segregation in the morphological
evolution of galaxies with earlier
formation of spheroids (zform > 3)
the merging rate increases with redshift
G. Soucail (OMP)
Morphological distribution of
the galaxies
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Impact of HST deep imaging
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0.1” resolution in the visible (pixel size)
0.17” in the near-IR (H, diffraction limited)
Ellipticals
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Spirals
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high redshift of formation. Regular increase of the mass by
accretion of sub-entities
Strong increase of the number of spirals and their surface
brightness
Irregulars
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Increase of their number with more and more disturbed
morphologies + increase of the merging rate
G. Soucail (OMP)
Galaxies observed in the Northern and Southern Hubble
Deep Fields (composite colors from blue, yellow and
near-IR filters).
G. Soucail (OMP)
Near-IR ground-based observations with AO
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Interests
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Practical points
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The light emitted in the near-IR is dominated by old stellar populations
and is more representative of the spheroidal population
It is less sensitive to the shift of the rest frame wavelength (UV is
observed in the optical)
The average redshift of flux-limited samples is higher than in B.
Need to center the fields around 12-13 mag. stars!
Best efficiency in K and H.
2 observational tests: PUEO/CFH and NACO/VLT
G. Soucail (OMP)
PUEO/CFHT deep field observations
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Selection of reference stars
13<R<14 (USNO catalog), as blue as possible (A-type).
 About 25% of the area nonoptimal (center+periphery)
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Number counts of field
galaxies in K’
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At K<20, 2-3 galaxies per PUEO
field (35”x35”). This means that
statistically, some fields are empty!!!
G. Soucail (OMP)
Example of a 1h integration field (1)
CFH12K
Reference star: r=13.1
b=13.4 (USNO)
PUEO
Star ghost
G. Soucail (OMP)
Example of a 1h integration field (2)
CFH12K
Reference star: r=12.2
b=13.1 (USNO)
PUEO
Star ghost
G. Soucail (OMP)
Main limitations and difficulties
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The central reference star
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Detection level limited by the size of the telescope
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R=12 seems to be the max. brightness acceptable!
A blue star is preferred for a lower occultation of the field in the
near-IR
Optical counter-parts partly blinded (star halo, saturated
columns).
Particularly true for extended objects
small pixels = low S/N per pixel (limited by the sky background
noise)
Field availability, limited around bright stars only ...
G. Soucail (OMP)
NACO/VLT Science Verification phase: the
Casertano Deep field
Reference star: r=12.1
b=13.9 (USNO)
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5 hours integration in Ks
+ 5 hours in J
Immediate release of the
data
NACO field 54”x54”
+ 45ksec in F606W with
HST/WFPC2
G. Soucail (OMP)
The Casertano deep
field in 3 colors !
J
Star ghost
HST
Ks
G. Soucail (OMP)
The Casertano deep
field in 3 colors !
RJK “true” color
image
A large number
of very promising
sources!
G. Soucail (OMP)
Some detailed galaxies ...
Limiting magnitudes
K ~ 22.0 (in 5 hours)
Interacting
systems
Very red objects
Edge-on disk
G. Soucail (OMP)
Discussion
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What could be the expected gain with a PUEO NUI?
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Seems difficult in the near-IR. Observations limited essentially by the
size of the telescope.
More promising in the far-red (I, z) ... Resolution should be
equivalent (or even better) to HST, but with a field size much smaller.
PUEO NUI in I is “equivalent” in terms of resolution to NACO in H.
Need to test deconvolution tools to test the gain in spatial
sampling with AO systems (TBD...)
The main limitation will still remain the bright reference star.
Although this kind of programme cannot be leading science
case, some specific observations could be realised in this
mode.
G. Soucail (OMP)