Hubble’s Slitless Spectroscopy
Patrick McCarthy – Carnegie Observatories
HST III Venice, October 2010
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Hubble’s Slitless Spectroscopy
• Slitless Spectra
• Stars & Planets
• Super Novae
• Faint Galaxies in the Visible
Star forming & Passive systems
• Distant Galaxies in the Near-IR
See poster by H. Atek & talk by A. Straughn
HST III Venice, October 2010
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Slitless Spectroscopy
No entrance aperture
- Disperser, PSF & Object shape set resolution
- Focal plane image is a stack of
monochromatic images of all objects
- No unique mapping between x,y and λ
- Good software is essential!
[NII]
Hα
[SII]
[NII]
SN 1987A
HST III Venice, October 2010
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Slitless Spectroscopy
Backgrounds & Foregrounds –
- All pixels see the full background
- Wider band-pass
more background
- Background is dispersed and reintegrated, so higher
dispersion
less contrast
- Low dispersion is preferred
Best Targets:
Compact objects with strong features
Cool stars, Planets, SNe, Distant Galaxies, AGN
HST III Venice, October 2010
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Slitless Spectroscopy
Good software is essential
“AxE” package developed by ECF in Garching
- Background removal
- Image plane – Spectral plane mapping
- Spectral extraction, wavelength calibration and flat-fields
ECF Archive
- NICMOS slitless grism spectra
- 48,000 calibrated ACS slitless spectra
Two-Day Workshop on Slitless Grism Spectroscopy with Hubble
STScI - November, 15-16
See STScI website for details
HST III Venice, October 2010
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Grisms for Slitless Modes on HST
R is 2-pixel resolution for point source
HST III Venice, October 2010
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Water Ice in the outer Solar System
NICMOS G141 & G206 Spectra
Pluto
Charon
HST III Venice, October 2010
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Exoplanet Atmospheres
NICMOS G141 &
G206 Spectra of
Exoplanet eclipse
Swain, Tinetti et al. Nature
HST III Venice, October 2010
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High Redshift SNe Spectroscopy
ACS G800L
spectra of
type Ia SNe to z ~ 1
Blakeslee et al. 2003
HST III Venice, October 2010
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ACS Grism Spectroscopy
ACS G800L
spectra of
Faintest Lyman
Break
galaxies at
z~5
Rhoads et al.
2009
“GRAPES”
HST III Venice, October 2010
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ACS Grism Spectroscopy
ACS G800L
spectra of
Passive Galaxies
in the UDF
Daddi et al. 2005
HST III Venice, October 2010
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NICMOS Grism Spectra
NICMOS G141 spectra
of Hα emitters
1 – 3 orbits per frame
1 emission line in every
3rd frame
1 line per object, max!
McCarthy et al. ‘99
HST III Venice, October 2010
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Hα Luminosity Functions
Yan et al. 99, Hopkins et al. 2000, Shim et al. 2009
HST III Venice, October 2010
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Hα Luminosity Density
Shim et al. 2009
HST III Venice, October 2010
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Cycle 17 WFC3 Grism Programs
ERS
Amber Straughn
Pathfinder
1 Field in both G102 & G141 GOODS-S
2 orbits each
GO1161
Ben Weiner
WISPS
56 orbits G141 in GOODS North
25 pointings, 2-orbits each
Matt Malkan
“Wide-Field Infrared Spectroscopic Parallel Survey”
To Date:
250 pure parallel orbits
G102 & G141
~60 pointings 150 sq. arcminutes
1-5 orbits each grism
40 pointings over 100 square arcminutes
HST III Venice, October 2010
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WFC3: 30 – 40 emission-line galaxies per field
Emission-lines
Zero-Order
1st-Order
HST III Venice, October 2010
2nd-Order
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Star Forming Galaxies
WFC3 G102
+ G141
2 orbits each
[SIII]
Same
telescope,
same ruling
(G141)!
Atek et al. 2010
HST III Venice, October 2010
[HeI]108
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Star Forming Galaxies
[OIII]5007 is the strongest line, [OII]3727 is unimpressive
z~1
Atek et al. 2010
HST III Venice, October 2010
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Star Forming Galaxies
Note numerous Hβ detections –
essential to E(B-V) and [Fe/H] determinations
1.5 < z <2
Atek et al. 2010
HST III Venice, October 2010
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High Equivalent Widths
[OIII]
Hα
See Atek et al. poster
HST III Venice, October 2010
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High Equivalent Widths
Keck/Deimos
spectra of
z = 0.7
High EW
[OIII] emitter
from G141
Redshifted
“Green Peas”
“Red Beans”?
Rest-frame Wλ([OIII]) > 500A!
HST III Venice, October 2010
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High Equivalent Widths
HST III Venice, October 2010
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Sampling the Galaxy Mass Function
The WFC3 Grisms
have the sensitivity
to sample 0.1L* and
fainter galaxies to
z>2
Emission-line
corrections push
continuum 1-2 mag
fainter in some
cases
HST III Venice, October 2010
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Quenched Galaxies at z = 1.5-2
500 Myrs after quenching of star formation
1 magnitude fainter!
Van Dokkum & Bremer 2010
Atek, Malkan, McC et al. 2010
HST III Venice, October 2010
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Quenched Galaxies at z > 2
Another magnitude fainter!
Contamination
Scarlatta, PMcC et al. 2010
HST III Venice, October 2010
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Passive Galaxies at z = 1 - 3
Scarlatta, PMcC et al. 2010
HST III Venice, October 2010
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G102 Search for Lyα Emission
Lyα at
z = 6.8?
Lyα?
H ~ 25AB
Decrement?
HST III Venice, October 2010
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Cycle 18 & Beyond
“WISPS”
Malkan et al.
280 pure parallel orbits
“3DHST”
van Dokkum et al.
248 prime orbits - G141 over full CANDELS area
2-orbit depth - Built on deep imaging fields
“CANDLES” & “CLASH”
SNe grism spectroscopy
A slitless Deep or Ultra-Deep Field?
JWST
2-5μm slitless mode Hα to z = 6.5
Dedicated Slitless Missions – Euclid!
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So Long, and Thanks for All the Fish
Special Thanks to the ECF team for their dedicated effort to
support slitless spectroscopy!
Richard Hook
Harald Kuntschner
Martin Kummel
Brit Sjoberg
Colleen Sharkey
Jeremy Walsh
Piero Rosati
Marco Lombardi
Felix Stoehr
Nor Pirzkal*
Jonas Haase
Martin Kornmesser
Kim Nilsson
Michael Rosa
And……
Bob Fosbury!
HST III Venice, October 2010
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HST III Venice, October 2010
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