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PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only
ID: 6598
Version: 7
Check-in Date: 06-Mar-1997
09:18:21
1.Proposal Title:
The Reddest Objects in the Universe
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2. Scientific Category 3. Proposal For 4. Cycle
COSMOLOGY GO 6
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5. Investigators
Contact?
PI: ARJUN DEY KITT PEAK NATIONAL OBSERVATORY
CoI: James R. Graham University of California, Berkeley N
CoI: Hyron Spinrad University of California, Berkeley N
CoI: Kurt Adelberger Caltech N
CoI: Charles Steidel Caltech N
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6. Abstract
Recent deep K--band imaging surveys have discovered a new population of infrared
bright, extremely red (R-K~gt 6), objects (EROS). There are no optical spectra for
these bizarre objects on account of their faintness (R ~gt 24.5), and therefore
their nature and redshift are uncertain. However we do have some intriguing clues
which suggest that HST imaging will be decisive in unraveling this engima. The EROS
are common: their surface density is similar to that of luminous quasars. They are
just spatially resolved in IR Keck images with 0.''4 seeing, and therefore they are
almost certainly distant galaxies. IR spectra from Keck of one object suggests z =
1.44. Very red colors would then follow naturally from shifting of the 4000Angstrom\
break to 1 Mu m. If all the EROS are at moderate redshifts (z~ 1-2), their
luminosities are several L^* and their volume space density is comparable to that of
active galaxies of similar luminosity. The morphology of the EROS will provide a
major clue to their nature -- are they ellipticals, disks or disturbed system? The
EROS are small with sizes of about 0.''5 and only HST offers the spatial resolution
necessary provide this information. Therefore, we propose to obtain broad band
images using the F814W filter in order to determine the morphologies and surface
photometry of these objects. This program will complement an ongoing Keck imaging
and spectroscopic study of these objects at near infrared wavelengths.
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Observations Description
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We propose to image a small sample of very red, radio quiet, galaxies in the
F814W filter. The objects in the sample are very faint, and typically have I
magnitudes in the range 23 < I < 25. Since some of the objects may be very low
surface brightness and diffuse, we estimate that we will require roughly two
orbits per target in order to get morphological information on the objects and
to aid in cosmic ray removal. We will image each target on a WF CCD and use
pixel substepping to slightly increase our sampling and better the resolution.
Our choice of using the WF CCD resolution rather than the PC is a compromise
between using the better sensitivity of the WF CCDs to diffuse objects, and
still regaining some of the resolution if the objects are very centrally
nucleated and compact. In 5400s through the F814W filter, we estimate that we
should be able to detect (at 5Sigma) surface brightnesses of 24.7 AB
mag/sq.arcsec.\\\\\\\\\\\\\\\\ (0.47MuJy/sq.arcsec.) in a 3* 3 pixel
(0.''3*0.''3) aperture on the WF2 CCD. Our point source 5Sigma detection
threshold will be ~ 27.9 AB mag (0.026MuJy). We therefore request two orbits
per target, or a total of 20 orbits for this project.
Real Time Justification
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None. We have begun a near--IR spectroscopic and imaging study of these objects
using the W.\\\\\\\\\\\\\\\\ M.\\\\\\\\\\\\\\\\ Keck Telescope. In addition,
some HST observations (in bluer bands than those proposed here) of a few of the
target fields already exist, but in many cases are of insufficient signal--to--
noise ratio (either because of the observed wavelength or due to the short
integration) for a detailed study of the morphology of the red objects. The
combination of the spectroscopy (for redshift and possible emission line ratios
/ continuum break indices), broad band optical and near--IR colors, and optical
and IR morphologies at high spatial resolution (~ 0"per1 in the optical with
HST, and ~ 0"per5 with NIRC on Keck) will provide us with all the information
necessary to understand this high space density population of mysterious
objects.
Calibration Justification
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Additional Comments
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Data Distribution
Media: 8MM
Blocking Factor: 10
Ship To: Dr. Arjun Dey, NOAO/KPNO, 950 N. Cherry
Ave., P.O. Box 26732, Tucson, AZ 85726-
6732
Ship Via:
Email: dey@noao.edu
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TARGET LIST a) Fixed Targets
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Tar| Target | Target | Target |Coord | Radial | Flux data
No | Name | Description | Position |Eqnx | Vel. |
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1 ERO0424+0204 GALAXY,HIGH REDSHIFT RA=4H 24M 8.54S +/- 0.1S,DEC=2D 2000 R = 24.9
A GALAXY 4' 25.0" +/- 1"
Comments: Position listed is for QSO in field
2 ERO0905+3408 GALAXY,HIGH REDSHIFT RA=09H 5M 30.5S +/- 0.1S,DEC=34D 2000 R = 24.4
A GALAXY 8' 9.7" +/- 1"
3 ERO1019+0535 GALAXY,HIGH REDSHIFT RA=10H 19M 32.81S +/- 2000 R = 25.3
A GALAXY 0.1S,DEC=05D 34' 35.2" +/- 1"
Comments: Position listed is for ERO
4 ERO1215-0034 GALAXY,HIGH REDSHIFT RA=12H 15M 47.72S +/- 0.1S,DEC=- 2000 R = 24.5
GALAXY 0D 34' 34.4" +/- 1"
Comments: Position listed is for ERO R6
5 ERO1645+4626 GALAXY,HIGH REDSHIFT RA=16H 45M 2.35S +/- 2000 R = 25
A GALAXY 0.1S,DEC=46D 26' 26.9" +/- 1"
Comments: Position listed is for HR10
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Visit: 01
Visit Requirements: ORIENT 90D TO 97D
On Hold Comments: <none>
Additional Comments: <none>
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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1 ERO0424+020 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 1140 S POS TARG 2.0,0.0
4A
Comments: Positioning QSO at the `optimal' WF3 position
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2 ERO0424+020 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 1140 S SAME POS AS 1
4A
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3 ERO0424+020 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 1200 S POS TARG 2.55,0.55
4A
Comments: Dithering by dX=0.55" from previous position
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4 ERO0424+020 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 1300 S SAME POS AS 3
4A
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Visit: 02
Visit Requirements: <none>
On Hold Comments: <none>
Additional Comments: <none>
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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1 ERO0905+340 WFPC2 IMAGE WF2 F814W CR-SPLIT=NO 1 1200 S
8A
Comments: Positioning ERO at optimal WF2 position
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2 ERO0905+340 WFPC2 IMAGE WF2 F814W CR-SPLIT=NO 1 1200 S SAME POS AS 1
8A
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3 ERO0905+340 WFPC2 IMAGE WF2 F814W CR-SPLIT=NO 1 1300 S POS TARG 0.55,0.55
8A
Comments: Dithering by dX=+0.55" from previous position
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4 ERO0905+340 WFPC2 IMAGE WF2 F814W CR-SPLIT=NO 1 1300 S SAME POS AS 3
8A
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Visit: 03
Visit Requirements: <none>
On Hold Comments: <none>
Additional Comments: <none>
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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1 ERO1019+053 WFPC2 IMAGE WF3 F814W CR-SPLIT=NO 1 1170 S
5A
Comments: Positioning ERO at optimal WF3 position
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2 ERO1019+053 WFPC2 IMAGE WF3 F814W CR-SPLIT=NO 1 1170 S SAME POS AS 1
5A
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3 ERO1019+053 WFPC2 IMAGE WF3 F814W CR-SPLIT=NO 1 1200 S POS TARG 0.55,0.55
5A
Comments: Dithering by dX=0.55" from previous position
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4 ERO1019+053 WFPC2 IMAGE WF3 F814W CR-SPLIT=NO 1 1300 S SAME POS AS 3
5A
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Visit: 04
Visit Requirements: ORIENT 277D TO 283D
On Hold Comments: <none>
Additional Comments: <none>
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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1 ERO1215-003 WFPC2 IMAGE WF4-FIX F814W CR-SPLIT=NO 1 1180 S POS TARG -28.4,27.1
4
Comments: Positioning R6 at (X,Y)=(-28.4",27.1") from
WF4-FIX
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2 ERO1215-003 WFPC2 IMAGE WF4-FIX F814W CR-SPLIT=NO 1 1180 S SAME POS AS 1
4
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3 ERO1215-003 WFPC2 IMAGE WF4-FIX F814W CR-SPLIT=NO 1 1180 S POS TARG -27.85,26.55
4
Comments: Dithering R6 by dY=-0.55" from previous
position
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4 ERO1215-003 WFPC2 IMAGE WF4-FIX F814W CR-SPLIT=NO 1 1280 S SAME POS AS 3
4
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Visit: 05
Visit Requirements: ORIENT 180D TO 213D
On Hold Comments: <none>
Additional Comments: <none>
Exposures
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Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special
Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements
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1 ERO1645+462 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 1300 S POS TARG 2.0,0.0
6A
Comments: Positioning HR10 at optimal WF3 position
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2 ERO1645+462 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 1300 S SAME POS AS 1
6A
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3 ERO1645+462 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 1300 S POS TARG 2.55,0.55
6A
Comments: Dithering by dX=0.55" from previous position
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4 ERO1645+462 WFPC2 IMAGE WF3-FIX F814W CR-SPLIT=NO 1 1400 S SAME POS AS 3
6A
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Summary Form for Proposal 6598
Item Used in this proposal
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Configurations WFPC2
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Opmodes IMAGE
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Optional Parameters CR-SPLIT=NO
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Proposal Category GO
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Scientific Category COSMOLOGY
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Special Requirements ORIENT 90D TO 97D POS TARG 2.0,0.0 SAME POS AS 1 POS TARG 2.55,0.55 SAME POS AS 3 POS TARG
0.55,0.55 ORIENT 277D TO 283D POS TARG -28.4,27.1 POS TARG -27.85,26.55 ORIENT 180D TO 213D
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Spectral Elements F814W
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Target Names ERO0424+0204A ERO0905+3408A ERO1019+0535A ERO1215-0034 ERO1645+4626A
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