Astrophysical false alarms in high contrast imaging surveys · PDF fileAstrophysical false...
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DRH Workshop – Heidelberg 13-15 Apr 2010
Astrophysical false alarms in high contrast
imaging surveys
– The SPHERE/NIRSUR case –
G. Chauvin
IPAG – Institut de Planétologie et Astrophysique de Grenoble
P. Delorme (IPAG), A. Vigan, A. Zurlo, C. Moutou (LAM), M. Bonnefoy
(MPIA), M. Bonavita,, S. Desidera, D. Mesa (INAF/Padova), and
the SPHERE consortium
Planet Validation Workshop – LAM – 13-15th May 2013
DRH Workshop – Heidelberg 13-15 Apr 2010
I- SPHERE/NIRSUR survey
II- Lessons from the past
III- Classes of contaminants
IV- False alarm diagnostics
V- Adopted strategy
Planet Validation Workshop – LAM – 13-15th May 2013
Outline
DRH Workshop – Heidelberg 13-15 Apr 2010 Planet Validation Workshop – LAM – 13-15th May 2013
I- SPHERE/NIRSUR
VLT/SPHERE ((Beuzit et al. 08)
• Scientific Goal: High-Contrast Imager for Giant Planets & Disks
• Description:
- SAXO, XAO system (ITTM-DM and DTTS, PTTS)
- NIR (YJHK): IRDIS (Dual imaging Spectrograph)
and IFU 3D-spectroscopy
- VIS: ZIMPOL (Imaging Polarimeter)
- Coronagraphs: Classical Lyot, A4P and ALC
- Differential imaging capabilities
DRH Workshop – Heidelberg 13-15 Apr 2010 Planet Validation Workshop – LAM – 13-15th May 2013
I- SPHERE/NIRSUR
DRH Workshop – Heidelberg 13-15 Apr 2010 Planet Validation Workshop – LAM – 13-15th May 2013
I- SPHERE/NIRSUR
ZIMPOL IRDIS IFS
FoV Sq 3.5‟‟ (instantaneous) Up to 4‟‟ radius (mosaic)
Sq 11‟‟ Sq 1.77‟‟
Spectral Range 0.5 – 0.9 μm 0.95 – 2.32 μm 0.95 – 1.35/1.65 μm
Spectral information
BB, NB BB, NB Slit spectro: 50/400
50 / 30
Linear Polarisation
Simultaneous on same detector, x 2 arms, exchangeable
Simultaneous dual beam, exchangeable
x
Coronography: no /4Q / Lyot
Rotation at Nasmyth: Pupil-stab. (instrument fixed wrt tel.) Field-stab (slit spectro, long DIT…) No rotation: minimize crosstalk…)
AO sensitivity for high contrast: R <9.5 for NIR; R<9 for R; R<7.8 for whole VIS
Separation with improved contrast: 2 - 20 λ/D, ie 30-300 mas in R, or 80 – 800 mas in H
Mode switching: not VIS and NIR in same night
DRH Workshop – Heidelberg 13-15 Apr 2010 Planet Validation Workshop – LAM – 13-15th May 2013
I- SPHERE/NIRSUR
SPHERE GTO • 260 nights over 4 – 6yrs
• Scientific programs:
. Disks (20n) . Reflected Light (10n)
. NIRSUR (200n) . SS & Evolved stars (10n)
. Add/Tests (10n)
• NIRSUR:
Survey of >400 nearby stars (AFGKM and <1 Gyr)
Occurrence of giant planets at wide orbits (>10 AU)
Giant planet atmospheres, Evolution, Planetary systems Dynamics…
DRH Workshop – Heidelberg 13-15 Apr 2010
I- SPHERE/NIRSUR
High-Contrast Imaging of Exoplanets 1/ XAO: Atmospheric turbulence (90% Strehl in H-band)
2/ Diffraction pattern: Halo suppression
3/ Quasi-static instrumental aberrations
& post-processing
XAO, Sr~90% Diffraction + static
aberration correction
Speckle Calibration,
Differential Methods
Contrast ~ 10-3-10-4 Contrast ~ 10-5 Contrast ~ 10-7
DRH Workshop – Heidelberg 13-15 Apr 2010
I- SPHERE/NIRSUR
NIRSUR Observing Strategy • IRDIFS Mode:
• IRDIS-DBI H2H3 (12.5” FoV) & IFS-Y-J (1.77” FoV)
simultaneously
• Atmosphere: Limiting seeing and coherence time for AO
• Star-brightness: AO performances (R < 9.5)
• Meridian-constraint:
• maximize field rotation for ADI
• Minimize the quasi-static aberrations
• Companion faintness: Observing sequence of 1-2hrs
• Dedicated calibrations: photometric & Astrometric field
DRH Workshop – Heidelberg 13-15 Apr 2010
I- SPHERE/NIRSUR survey
II- Lessons from the past
III- Classes of contaminants
IV- False alarm diagnostics
V- Adopted strategy
Planet Validation Workshop – LAM – 13-15th May 2013
Outline
DRH Workshop – Heidelberg 13-15 Apr 2010 NIRSUR Workshop – Padova 3 – 6 May 2010
Past Deep Imaging Surveys . Magnitude limit: Hlim = 21– 23 (HA = 8-9; ΔH=14-15) (Chauvin et al. 2010)
. 65 stars observed; 240 False Alarms (FAs) . FA rate ~ 55%
28”
II- Lessons from the past
NaCo (VLT)
DRH Workshop – Heidelberg 13-15 Apr 2010
False alarms
Programme Instrument FoV Filter Nb b (o) Fc(%) Reference
Young stars VLT/NaCo 28” H/K 63 27.3 55.0 (Chauvin et al. 2010)
Young stars HST/NICMOS 19” H 45 9.9 57.7 (Lowrance et al. 2005)
Planet hosts Keck 5” K 40 -11.5 16.0 (Luhman et al. 2002)
Young & Int-old Gemini/NIRI 22” H 85 16.9 64.7 (Lafreniere et al. 2007)
Field contamination from past DI surveys:
II- Lessons from the past
Planet Validation Workshop – LAM – 13-15th May 2013
DRH Workshop – Heidelberg 13-15 Apr 2010
Proper motion study of CC-1 .
Primary star proper & parallactic
motion. Follow-up at several epochs
>> co-moving object
Orbital motion
>> physically bound
But do we want to conduct
systematic follow-up observations?
Identification: Astrometric Follow-up
II- Lessons from the past
DRH Workshop – Heidelberg 13-15 Apr 2010
Identification: Impact on the survey size . 200 GTO nights
. Obs.Time/target
. FAs Contamination (Fc)
“Systematic astrometric follow-up”: Fc = 50% 66n follow-up
Fc = 33% 50n follow-up
. Nb Visits
. Target List (Nb stars)
. Nb Follow-up Visits
Nb Targets = Nb Visits / ( 1 + Fc)
Nb “Discovery“ Nights = 200. / ( 1 + Fc)
II- Lessons from the past
Planet Validation Workshop – LAM – 13-15th May 2013
DRH Workshop – Heidelberg 13-15 Apr 2010
Identification: Impact on the survey size . 200 GTO nights
. Obs.Time/target
. FAs Contamination (Fc)
>> Identification Strategy: impact the Nb Targets observed
our chance of planet detection
the statistical significance of our complete sample
. Nb Visits
. Target List (Nb stars)
. Nb Follow-up Visits
Nb Targets = Nb Visits / ( 1 + Fc)
Nb “Discovery“ Nights = 200. / ( 1 + Fc)
II- Lessons from the past
Planet Validation Workshop – LAM – 13-15th May 2013
DRH Workshop – Heidelberg 13-15 Apr 2010
I- SPHERE/NIRSUR survey
II- Lessons from the past
III- Classes of contaminants
IV- False alarm diagnostics
V- Adopted strategy
Planet Validation Workshop – LAM – 13-15th May 2013
Outline
DRH Workshop – Heidelberg 13-15 Apr 2010
III- Classes of contaminants
1. Solar System Bodies: (B. Carry; F. Marchis)
. Asteroids: km- to 100-m size, G2 solar-type spectra
. TNOs: km-size bodies; H20 (CH4...) ice-composition
(Barucci et al. 2005)
DRH Workshop – Heidelberg 13-15 Apr 2010
1. Solar System Bodies: (B. Carry; F. Marchis)
. Asteroids: km- to 100-m size, G2 solar-type spectra
. TNOs: km-size bodies; H20 (CH4...) ice-composition
. Identification:
High-proper motion: μ(„‟/min) = 140/d(AU) >> smearing!
930mas/s main-Belt (2.5 AU); 50 mas/s TNOs (50 AU)
Ephemerids: - SkyBoT (http://vo.imcce.fr/webservices/skybot/)
- JPL/Horizons (http://ssd.jpl.nasa.gov/?horizons)
>> implemented with success for NaCo, Keck !
. How many asteroids/TNOs FAs? (>> could simulate the expected nb)
NIRSUR Workshop – Padova 3 – 6 May 2010
III- Classes of contaminants
Planet Validation Workshop – LAM – 13-15th May 2013
DRH Workshop – Heidelberg 13-15 Apr 2010
2. Galactic: Field Stars • Galactic Population Synthesis:
The Besançon Model (Robin et al. 2003)
The TRILEGAL Model (Girardi et al. 2005)
• Predictions calibrates using Hipparcos observations and recent
large scale surveys in optical and NIR.
• Friendly-tool to simulate Field Stars Contamination:
Inputs: Catalogue and magnitude limit (JH...)
Outputs: > Star counts / sq.deg
> properties: SpT, Teff, Age, FeH, ppm....
NIRSUR Workshop – Padova 3 – 6 May 2010
III- Classes of contaminants
Planet Validation Workshop – LAM – 13-15th May 2013
DRH Workshop – Heidelberg 13-15 Apr 2010
2. Galactic: Field Stars • The NIRSUR survey simulation
597 stars from the TDB (and their gal. coordinates)
Hlim = 23 (ΔH = 16–17 for typ. H = 6.5)
Cumulated star counts
density Map / sq.deg
(for Hlim<23)
III- Classes of contaminants
DRH Workshop – Heidelberg 13-15 Apr 2010
2. Galactic: Field Stars • NIRSUR: Cumulated star counts
• In average, 7 field stars (H < 23) per IRDIS FoV
III- Classes of contaminants
DRH Workshop – Heidelberg 13-15 Apr 2010
2. Galactic: Field Stars • NIRSUR: Complete survey field stars contamination
• 52% of IRDIS FoVs, contaminated by 1 field star with H < 23
III- Classes of contaminants
DRH Workshop – Heidelberg 13-15 Apr 2010
2. Galactic: Field Stars • NIRSUR: Contaminant predicted properties
III- Classes of contaminants
DRH Workshop – Heidelberg 13-15 Apr 2010
2. Galactic: Field Stars • NIRSUR: Contaminant predicted properties
Field MS M dwarfs!
III- Classes of contaminants
DRH Workshop – Heidelberg 13-15 Apr 2010
3. X-Galactic: (M. Turatto; P. Delorme)
• Low- and high-redshift galaxies
HST/NICMOS deep field study
Galaxies counts & morphology (H < 24)
(Teplitz et al. 1998)
III- Classes of contaminants
DRH Workshop – Heidelberg 13-15 Apr 2010
3. X-Galactic: (M. Turatto; P. Delorme)
• Low- and high-redshift galaxies
HST/NICMOS deep field study
Galaxies counts & morphology (H < 24)
(Teplitz et al. 1998)
• Counts = 2.1 X-Gal/FoV
IRDIS (H < 23):
. Morphology:
z = 0.3, 3kpc Ø = 0.6”
z = 1-4, 4-8kpc Ø = 0.4-1.0”
III- Classes of contaminants
DRH Workshop – Heidelberg 13-15 Apr 2010
III- Classes of contaminants
3. X-Galactic: (M. Turatto; P. Delorme)
• QSOs (Active nucleus galaxies)
Chandra Survey: 60 QSOs over 300 sq. arcmin; (Barger et al. 2002)
> QSO counts: (J<23) 0.01 QSO / IRDIS FoV
• Low & High-z Star forming regions
Giant HII regions (200pc size); At z = 0.3 - 4, Ø = 25 – 45 mas
• Intergalactic Globular Clusters
ACS Deep field (Williams et al. 2007)
> IGC counts (H < 22): 0.04 IGC / IRDIS FoV
• High-z Super Novae
SNe computation (Dahlen & Fransson et al. 1999, SNe rates)
> SNe counts: 0.004 SNe / IRDIS FoV
DRH Workshop – Heidelberg 13-15 Apr 2010
False alarms summary, Classe Type Contamination
(Nb/IRDIS FoV)
Comments
Solar System Asteroids/TNOs ? smearing, ephemerids
Galactic Field Stars 7 M-stars for H = [17-25]
point-like. same H2H3 color as L-type EGPs
X-Gal Low & High-z Gal. 2. resolved
QSOs 0.01 negligible
X-SFRs ? negligible
IGCs 0.04 negligible
SNe 0.004 negligible
>> Major source of astro-FAs: background field M-dwarfs
III- Classes of contaminants
Planet Validation Workshop – LAM – 13-15th May 2013
DRH Workshop – Heidelberg 13-15 Apr 2010
I- SPHERE/NIRSUR survey
II- Lessons from the past
III- Classes of contaminants
IV- False alarm diagnostics
V- Adopted strategy
Planet Validation Workshop – LAM – 13-15th May 2013
Outline
DRH Workshop – Heidelberg 13-15 Apr 2010
Identification, available diagnostics:
1. Database/Preparatory observations:
cross-correlation with on-line catalogues
building a Deep Imaging Database
2. NIRSUR spectro-photometric diagnostics
ability to identify false alarms
3. Astrometric follow-up
Astrometric precision & target proper motion
IV- False alarms diagnostics
Planet Validation Workshop – LAM – 13-15th May 2013
DRH Workshop – Heidelberg 13-15 Apr 2010
False Alarm Operation Diagramme
1 Visit
Detection
Non-detection
New
Identified
Data Analysis NIRSUR Diagnostics
Identified
Un-identified
Follow-up TDB
TDB
Identified
1. 2. 3.
NIRSUR Workshop – Padova 3 – 6 May 2010
Priority?
Planet Validation Workshop – LAM – 13-15th May 2013
IV- False alarms diagnostics
DRH Workshop – Heidelberg 13-15 Apr 2010
1. Database/Preparatory observations
1.1 Literature: compilation of published surveys
(catalogue, instrument, observing mode, detection performances,
source identification...)
1.2 Collecting Deep Imaging Data (DIVA)
Status: currently 400 stars (300 potential targets for NIRSUR)
Interface with the NIRSUR Target Database
1.3 NaCo Large Programme (Preparatory survey)
ADI H-band observation: 110 new stars
NIRSUR Workshop – Padova 3 – 6 May 2010 Planet Validation Workshop – LAM – 13-15th May 2013
IV- False alarms diagnostics
DRH Workshop – Heidelberg 13-15 Apr 2010
2. NIRSUR diagnostics
Observing modes
. IRDIS DBI:
H2H3, H2, H3 photometry
. IFS (0.95-1.35 μm):
Y-J Rec. photometry
LRS
IRDIS DBI (H2H3)
IFS (0.95-1.35 μm)
12.5’’ 1.77’’
Outer FoV
Inner FoV
NIRSUR Workshop – Padova 3 – 6 May 2010
IV- False alarms diagnostics
DRH Workshop – Heidelberg 13-15 Apr 2010
2. NIRSUR diagnostics
2.1 Outer “IRDIS alone” FoV
Single IRDIS detection:
H2 or H3 or H2H3
Cannot discriminate!
Double IRDIS detection:
H2 and H3 (H2 and H2H3...)
Can easily discriminate cool
T2 to Y EGPs from field stars.
>> Problem for young L-type EGPs!
>> Expect a lot of M field stars!
IV- False alarms diagnostics
DRH Workshop – Heidelberg 13-15 Apr 2010
2. NIRSUR diagnostics
2.2 Inner “IRDIS/IFS ” FoV
Single IFS detection:
Y-J low-res spectra
(Sp. indexes, cross-libs)
High SNR: can well discrim-
inate L-,T- and Y-types
from FAs
.
IFS Extraction simulations (Dino):
L0-type EGP, 10-6 (ΔJ = 15) at 0.5”
>> low SNR: more difficult
for L-types than T, Y-types
>> Smaller FoV (less FAs)
IV- False alarms diagnostics
DRH Workshop – Heidelberg 13-15 Apr 2010
2. NIRSUR diagnostics Summary:
. Outer “IRDIS alone” FoV
. Important Nb of FAs/FoV (Fc ~ 50%)
. Single detection no diagnostics
. Double detection no discrimination btw warm L-types
(early-T) EGPs and field M stars
. Inner “IRDIS/IFS” FoV
. Less FAs/FoV (Fc of a few %)
. “IFS” detection good discrimination
low S/N, more difficult for L-types
. Combined “IRDIS/IFS” improved diagnostics
NIRSUR Workshop – Padova 3 – 6 May 2010
IV- False alarms diagnostics
DRH Workshop – Heidelberg 13-15 Apr 2010
3. Astrometric Follow-up
TDB, NIRSUR target proper motion
Easy confirmation over a
few months with a ~5mas
accuracy
IV- False alarms diagnostics
DRH Workshop – Heidelberg 13-15 Apr 2010
Available diagnostics – summary (Contaminants: mostly field M dwarfs, 52% Outer FoV)
1. Archive/TDB: - relevant for Outer FoV
- Follow-up obs. reduction to be quantified
2. NIRSUR Diagnostics: - handicap for the Outer FoV: L (early-T) type EGPs
- Inner FoV: less problematic
(lower contamination and better diagnostics)
>> enable to derive the CC (Mass, Δproj) if bound!
3. Astrometry: - Firm identification (a few months)
- But, impact Nb of targets observed
IV- False alarms diagnostics
DRH Workshop – Heidelberg 13-15 Apr 2010
I- SPHERE/NIRSUR survey
II- Lessons from the past
III- Classes of contaminants
IV- False alarm diagnostics
V- Adopted strategy
Planet Validation Workshop – LAM – 13-15th May 2013
Outline
DRH Workshop – Heidelberg 13-15 Apr 2010
V- Strategy & Planet Validation
Adopted strategy 1. Scientific Goals Detection & statistical completeness
2. Sample selection: Age, distance, SpT, FeH, (Galactic latitude)
Selection: Detection or Statistics driven?
Expected Fc ~50%
BUT, we want the Follow-up to be < 30%
3. Physical window Focus on close and low-mass companions
Physical cutoff: < 200 AU (r < 4”) and < 60 Mjup
Planet Validation Workshop – LAM – 13-15th May 2013
DRH Workshop – Heidelberg 13-15 Apr 2010
V- Strategy & Planet Validation
Adopted strategy 4. Candidate Ranking: 1/ Top-priority: CH4 or spectral signatures
for Follow-up 2/ Others, focus on the closest and lightest EGPs
Predicted mass & distance; Contamination Probability;
Ranking: merit function with (M, a) cutoff
depending on predicted M, a and Fc
5. Follow-up: Total should not follow-up more than 30%
Priority according to the candidate ranking
Complete on a physical distance parameter space
Planet Validation Workshop – LAM – 13-15th May 2013
DRH Workshop – Heidelberg 13-15 Apr 2010 Planet Validation Workshop – LAM – 13-15th May 2013
Outline Adopted strategy
6. Characterization: a/ Primary refined parameters (Age, d)
> Alice Zurlo’s Talk
b/ Atmosphere
IFS and IRDIS extended diagnostics
(spectroscopy and additional photometric filter)
c/ Predicted Physical properties (Mass)
d/ Orbital properties (sma, ecc.)
e/ Circumstellar environment (disk, planets…)