SPIRE spectroscopy data analysis: FTS spectra - Herschel

Day 4: SPIRE !
Analysing SPIRE FTS spectra!
Rosalind Hopwood !
1 hAp://herschel.esac.esa.int/twiki/pub/Public/SpireCalibraHonWeb/
FTS-­‐flyer-­‐landscape_v12_A4.pdf THE FTS
The FTS flyer ICC#
Spe
The SPIRE Fourier
Transform Spectrometer
SSW
c
Herschel
Pho tro
to
SPATIAL DOMAIN: INTERFEROGRAM
SLW
KEY LITERATURE
SPIRE Handbook,
SPIRE Data Reduction Guide
Swinyard et al., 2014
Hopwood et al., 2015
WAVELENGTH
COVERAGE
SLW
SSW
447-1018 GHz
671-294 µm
944-1568 GHz
318-191 µm
INSTRUMENTAL 970-440 kms-1 450-280 kms-1
LINE WIDTH HR
1.2 GHz
1.2 GHz
CALIBRATION ACCURACY
Point-source : 6%
Extended-source :
1% sparse mode & 7% mapping mode
Frequency
dependent
beam
CONTINUUM OFFSET (additive):
Point-source
calibration
Extended
calibration
MAPPING MODES
2.6’ FoV
Sparse: single pointing
Intermediate: 4 point jiggle
Full: 16 point jiggle
SPARSE OR MAPPING
RASTER PATTEREN
User defined FoV
Fringing
Glitches
SLW
SSW
0.4 Jy
0.3 Jy
3.4x10-20
1.1x10-19
Wm-2Hz-1sr-1! Wm-2Hz-1sr-1!
SLW CUBE
SSW CUBE
Small-scale shape
in the spectrum
‘Beats’: strong
CO ladder in the
spectrum
SPECTRAL DOMAIN: SPECTRUM
SLW
LINE
PROFILE
J=12-11
J=11-10
J=10-9
HR
J=9-8
J=8-7
J=7-6
J=5-4 J=6-5
SSW
SPECTRAL RESOLUTION
HIGH (HR) 1.2 GHz, LOW (LR) 25 GHz
Herschel Science Archive Level-2
SPARSE naming example for HR
Point-source calibrated Spectra ! “HR_spectrum_point”
Extended calibrated ! “HR_spectrum_ext”
MAPPING naming example for HR SLW
Spectral cubes ! “HR_SLW_cube”
Unaveraged spectra ! “HR_SLW_spectrum2d”
Herschel Online Data Processing Workshop 19th June 2015 2 Analysing SPIRE FTS spectra Reference material SPIRE DRG: Chapter 7 for the Spectrometer SPIRE Handbook: hAp://herschel.esac.esa.int/Docs/SPIRE/spire_handbook.pdf FTS calibra6on: Swinyard et al. 2014 (arXiv:1403.1107) FTS calibra6on program: Hopwood et al. 2015 (arXiv:1502.05717) FTS Mapping: Benielli et al. 2014 (arXiv:1401.2040)* Experimental Astronomer, Volume 37, Issue 2, July 2014 •  Five FTS papers (*including the mapping paper above) Ø  Fulton et al. FTS RSRFs arXiv:1401.2049 Ø  Hopwood et al. Telescope model correcHon arXiv:1401.2047 Ø  Lu et al. Bright source mode arXiv:1401.2045 Ø  Valtchanov et al. RelaHve poinHng offsets arXiv:1401.2043 •  SECT: Wu et al. 2013 (arXiv:1306.5780) •  Beam profile: Makiwa et al. 2013 (Applied Op<cs, Vol. 52, Issue 16, p. 3864-­‐3875) •  Pipeline: Fulton et al. 2010 (to be updated soon) (SPIE Conference Series, 2010) • 
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Herschel Online Data Processing Workshop 19th June 2015 3 Analysing SPIRE FTS spectra DocumentaHon is your first port of call SPIRE Data Reduc6on Guide (SDRG): Chapter 7 for the Spectrometer Relevant secHons for this session are: •  7.4 PoinHng consideraHons •  7.5 Recipes for faint & medium strength sources •  7.6 Recipes for semi-­‐extended sources •  7.11 Spectral Analysis SPIRE Handbook (formerly the observer’s manual) For more technical stuff •  Overview of the instrument and flux calibraHon Up-­‐to-­‐date FTS Calibra6on of the SPIRE FTS (Swinyard et al. 2014) uncertainHes Characterisa6on of the SPIRE FTS (Hopwood et al. 2015) Data Analysis Guide (DAG): All the HIPE •  Chapter 3 Plocng help you should need worked examples are helpful for scripHng All you need to know about FTS data reducHon and idenHfying potenHal issues Herschel Online Data Processing Workshop 19th June 2015 4 Analysing SPIRE FTS spectra Aim for today: idenHfying, understanding and correcHng problem spectra •  Examining FTS data for potenHal problems •  Understanding where problems may originate •  CorrecHng your data •  Background subtracHon •  PoinHng offset: SECT •  ParHally extended: SECT •  (Droopy SLWC3) •  SECT: a closer look •  Spectral line ficng •  Noise esHmate •  Comparison with the photometer Herschel Online Data Processing Workshop 19th June 2015 5 Analysing SPIRE FTS spectra Aim for today: idenHfying, understanding and correcHng problem spectra •  Examining FTS data for potenHal problems •  Understanding where problems may originate (Array footprint plot) •  CorrecHng your data •  Background subtracHon •  PoinHng offset: SECT HIPE SPIRE Spectrometer •  ParHally extended: SECT useful scripts •  (Droopy SLWC3) •  SECT: a closer look •  Spectral line ficng •  Noise esHmate •  Comparison with the photometer In HIPE Scripts menu Herschel Online Data Processing Workshop 19th June 2015 6 Analysing SPIRE FTS spectra A note on the Spectrometer useful scripts Designed to: •  help facilitate FTS data processing/analysis •  be easily understood -­‐> if not, let us know •  be easy to edit •  to compliment each other e.g. Herschel Online Data Processing Workshop 19th June 2015 7 Analysing SPIRE FTS spectra: a note on HSA data HSA L2 data is now HIPE 13 processed no need to rerun the pipeline unless: -­‐  You want a closer look at intermediate steps -­‐  Get the unaveraged scans -­‐  Exclude the vigneAed detectors from your maps: just the last bit of the script ‘SPIRE Calibra6on’ view: See what’s new in the SPIRE calibraHon Herschel Online Data Processing Workshop 19th June 2015 8 Analysing SPIRE FTS spectra: a note on HSA data HSA L2 data is now HIPE 13 processed no need to rerun the pipeline unless: -­‐  You want a closer look at intermediate steps -­‐  Get the unaveraged scans -­‐  Exclude the vigneAed detectors from your maps: just the last bit of the script ‘SPIRE Calibra6on’ view: See what’s new in the SPIRE calibraHon Herschel Online Data Processing Workshop 19th June 2015 9 Analysing SPIRE FTS spectra: a note on HSA data HSA L2 data is now HIPE 13 processed no need to rerun the pipeline unless: -­‐  You want a closer look at intermediate steps -­‐  Get the unaveraged scans -­‐  Exclude the vigneAed detectors If your data is pre-­‐HIPE from your maps: just the last bit of 13 processed, download the script it again now! ‘SPIRE Calibra6on’ view: See what’s new in the SPIRE calibraHon Herschel Online Data Processing Workshop 19th June 2015 10 Analysing SPIRE FTS spectra Examining FTS data Downloading an observaHon straight from the HSA into HIPE: e.g. observa<on = getObserva<on(1342197486, useHsa=True) Check out the Summary informaHon Herschel Online Data Processing Workshop 19th June 2015 11 Analysing SPIRE FTS spectra Examining FTS data Downloading an observaHon straight from the HSA into HIPE: e.g. observa<on = getObserva<on(1342197486, useHsa=True) Check out the Browse Product image Herschel Online Data Processing Workshop 19th June 2015 Spectra from the centre detectors 12 Analysing SPIRE FTS spectra Examining FTS data Downloading an observaHon straight from the HSA into HIPE: e.g. observa<on = getObserva<on(1342197486, useHsa=True) Check out the Browse Product image ANY PROBLEMS? Spectra from the centre detectors Not for this one! Herschel Online Data Processing Workshop 19th June 2015 13 Analysing SPIRE FTS spectra See a problem -­‐> documentaHon is your first port of call SPIRE Data Reduc6on Guide (SDRG): Chapter 7 for the Spectrometer Relevant secHons for this session are: •  7.4 PoinHng consideraHons •  7.5 Recipes for faint and medium strength sources •  7.6 Recipes for semi-­‐extended sources •  7.11 Spectral Analysis 7.6.2 Does my spectrum need correcHng? Herschel Online Data Processing Workshop 19th June 2015 14 Analysing SPIRE FTS spectra 7.6.2 Does my spectrum need correcHng? ① Point-­‐source embedded in extended emission ② Point-­‐source observed with a significant poinHng offset ③ A source with parHally extended morphology All three issues lead to a jump between SLW and SSW: SeparaHng the cause of the jump is necessary This may be difficult and someHmes not possible Herschel Online Data Processing Workshop 19th June 2015 15 Analysing SPIRE FTS spectra 7.6.2 Does my spectrum need correcHng? A fourth issue: now corrected in HIPE 13… for the most part HIPE 13 HIPE 12 This issue was only significant for faint sources The nonlinearity correcHon has been updated for HIPE 13 It corrects an issue for observaHons taken at the beginning of each pair of FTS operaHonal days There are a few rare excepHons If you see your HIPE 13 reduced SLWC3 spectrum “drooping” contact the helpdesk Herschel Online Data Processing Workshop 19th June 2015 16 Analysing SPIRE FTS spectra 7.6.2 Does my spectrum need correcHng? A fourth issue: now corrected in HIPE 13… for the most part HIPE 13 HIPE 12 This issue was only significant for faint sources The nonlinearity correcHon has been updated for HIPE 13 It corrects an issue for observaHons taken at the beginning of each pair of FTS operaHonal days There are a few rare excepHons If you see your HIPE 13 reduced SLWC3 spectrum “drooping” contact the helpdesk Herschel Online Data Processing Workshop 19th June 2015 17 Analysing SPIRE FTS spectra ①  Point-­‐source embedded in extended emission AFGL4106: post-­‐red supergiant binary; medium source (> 10Jy) observa<on_1 = getObserva<on(1342246991, useHsa=True) Check out the browse product image ANY PROBLEMS? Herschel Online Data Processing Workshop 19th June 2015 18 Analysing SPIRE FTS spectra ①  Point-­‐source embedded in extended emission AFGL4106: post-­‐red supergiant binary; medium source (> 10Jy) observa<on_1 = getObserva<on(1342246991, useHsa=True) ANY PROBLEMS? •  The extended background is point-­‐
source calibrated, which leads to a poor conHnuum shape and extra fringing •  SLW is more strongly affected due to larger beam size (～2 ×SSW) •  Large-­‐scale conHnuum shape can be corrected SLWC3 SSWD4 Poor shape Fringing > 850 < 750 GHz GHz for SLW jump between the bands Herschel Online Data Processing Workshop 19th June 2015 19 Analysing SPIRE FTS spectra ①  Point-­‐source embedded in extended emission Useful script: Spectrometer array footprint plot Plots the FTS footprint over a photometer map •  If no photometer map inpuAed then photObsids used (if there are any) •  Photometer map should be FIR/submm •  Use to idenHfy a background/foreground •  Use to check for contaminaHng neighbours Hopwood et al. 2015. Script edited for plocng colours. Herschel Online Data Processing Workshop 19th June 2015 20 Analysing SPIRE FTS spectra ①  Point-­‐source embedded in extended emission Useful script: Spectrometer array footprint plot Hopwood et al. 2015 figure 2. Script edited for plocng colours. Point-­‐like Point-­‐like sicng in GalacHc Cirrus (IRAS 100 µm) ParHally extended morphology Herschel Online Data Processing Workshop 19th June 2015 21 AFGL4106 Analysing SPIRE FTS spectra ①  Point-­‐source embedded in extended emission Useful script: Spectrometer SLW 1st ring background subtrac<on SSW 2nd ring MENTION LOST FLUX Herschel Online Data Processing Workshop 19th June 2015 22 AFGL4106 Analysing SPIRE FTS spectra ①  Point-­‐source embedded in extended emission Useful script: Spectrometer SLW 1st ring background subtrac<on Shape improved < 750 GHz SSW 2nd ring Fringing > 850 GHz for SLW sHll there Jump between the bands is corrected Herschel Online Data Processing Workshop 19th June 2015 23 Analysing SPIRE FTS spectra ①  Point-­‐source embedded in extended emission Useful script: Spectrometer background subtrac<on A word of cau6on •  There is real flux in the detector rings •  See Hopwood et al. 2015 for more details •  For a point source (Uranus/Neptune) bang on the centre there is around •  1.9% in SLW 1st ring •  Only 0.1% in SSW 2nd ring •  (1.4% SSW 1st ring: not used) •  Point source calibraHon accounts for this “missing” bit •  Lots more flux in for semi-­‐extended sources •  For AFGL4106 the results are worth the loss: ficng is easier Hopwood et al. 2015 SLW 1st ring SSW 1st ring SSW 2nd ring BGS script results Herschel Online Data Processing Workshop 19th June 2015 AFGL4106 24 Analysing SPIRE FTS spectra ② Point-­‐source observed with a significant poinHng offset AFGL2688: point-­‐like source with FWHM 6.6” afgl2688Obs = getObserva<on(1342198270, useHsa=True) See the DRG 7.4. PoinHng ConsideraHons Herschel Online Data Processing Workshop 19th June 2015 25 Analysing SPIRE FTS spectra ② Point-­‐source observed with a significant poinHng offset AFGL2688: point-­‐like source with FWHM 6.6” afgl2688Obs = getObserva<on(1342198270, useHsa=True) In this case the jump must be due to a poinHng offset Jump between the bands See the DRG 7.4. PoinHng ConsideraHons Herschel Online Data Processing Workshop 19th June 2015 26 Analysing SPIRE FTS spectra ② Point-­‐source observed with a significant poinHng offset AFGL2688: point-­‐like source with FWHM 6.6” afgl2688Obs = getObserva<on(1342198270, useHsa=True) See the DRG 7.4. PoinHng ConsideraHons raDecOffset and bsmOffset give info on KNOWN poinHng offset. The APE is sHll associated to the poinHng. Herschel Online Data Processing Workshop 19th June 2015 27 Analysing SPIRE FTS spectra ② Point-­‐source observed with a significant poinHng offset AFGL2688: point-­‐like source with FWHM 6.6” afgl2688Obs = getObserva<on(1342198270, useHsa=True) See the DRG 7.4. PoinHng ConsideraHons raDecOffset and bsmOffset give info on KNOWN poinHng offset. The APE is sHll associated to the poinHng: raDecOffset “The offset between the commanded posiHon and the actual reconstructed poinHng, which includes any systemaHc BSM offset (bsmOffset), but not the APE.” bsmOffset “BSM offset posiHon (0.0 or 1.72 arcsec), which is corrected for by the point-­‐source calibraHon. This systemaHc offset is included in the raDecOffset value.” Herschel Online Data Processing Workshop 19th June 2015 28 AFGL2688 Analysing SPIRE FTS spectra ② Point-­‐source observed with a significant poinHng offset SECT: correc<ng for poin<ng offset A. Using HIPE to get the poinHng info: See the DRG 7.4. PoinHng ConsideraHons See the DRG 7.6. Recipes for semi-­‐extended sources B. Using the relaHve poinHng method of Valtchanov et al. 2014: 6.21” ± 0.32” -­‐  Needs repeated observaHons -­‐  A reference observaHon is used to correct the others -­‐  BSM offset should not be subtracHng for input into SECT: -­‐  SECT automaHcally de-­‐corrects this offset, if necessary Which gives us: A) 3.37” the “Herschel” offset B) 6.21” the relaHve offset Herschel Online Data Processing Workshop 19th June 2015 29 AFGL2688 Analysing SPIRE FTS spectra ② Point-­‐source observed with a significant poinHng offset Semi Extended CorrecHon Tool SECT: the GUI The semiExtendedCorrector task: Input variables: -­‐ Point source calibrated spectrum object (SPSS) -­‐ SPIRE calibraHon context OpHons: -­‐ For plots: doPlots -­‐ To opHmise source model diameter: opHmiseDiameter -­‐ UnHck applyCorrec<on to get the correcHon itself back -­‐ gaussRefBeamDiam -­‐ couplingThreshold Herschel Online Data Processing Workshop 19th June 2015 Used to set the reference beam 30 Analysing SPIRE FTS spectra ② Point-­‐source observed with a significant poinHng offset SECT: the reference beam The semiExtendedCorrector task The reference beam: -­‐ Used to normalise the spectrum so the output is equivalent to a spectrum observed with a frequency independent Gaussian beam -­‐ Default FWHM is 40” -­‐ FWHM can be set to match See the DRG another telescope 7.6. Recipes for -­‐ Set FWHM large to remove semi-­‐extended effect of reference beam (the sources whole source distribuHon is within the beam Figure 7.52. The reference beam. -­‐ The final spectrum is normalised to include the emission inside the reference beam. -­‐ The source distribuHon is assumed to be independent of frequency. Herschel Online Data Processing Workshop 19th June 2015 31 Analysing SPIRE FTS spectra ② Point-­‐source observed with a significant poinHng offset SECT: the source distribu<on model The semiExtendedCorrector task: sourceModel -­‐ Gaussian/top hat/Sersic -­‐ x and y offsets can be set -­‐ The profile is shown under the FTS array footprint in the boAom panel -­‐ Errors increase for source models larger than the SSW beam size -­‐ A point-­‐source can be inpuAed as a Gaussian with diameter 0.01” -­‐ Greater control of SECT can be achieved with a script See the DRG SECT takes into consideraHon: -­‐  SLWC3 is offset to SSWD4 by 2.2” -­‐  ObservaHons before OD 1011 were taken with the BSM set to 1.72” -­‐  These issues are corrected for by the point source calibraHon so SECT 7.6. Recipes for semi-­‐extended de-­‐corrects for internally sources Herschel Online Data Processing Workshop 19th June 2015 32 AFGL2688 Analysing SPIRE FTS spectra ② Point-­‐source observed with a significant poinHng offset SECT: correc<ng for poin<ng offset Running SECT in a script for the miss-­‐pointed AFGL2688 observa6on: # Get the SPIRE calibra6on cal = spireCal(pool=“spire_cal_13_1”) # Get the Level-­‐2 point-­‐source calibrated product (spss) spss = afgl2688Obs.level2.getProduct(“HR_spectrum_point”) See the DRG 7.6. Recipes for semi-­‐extended sources # CreaHng the model image (for a point source): # (SourceModel, diameter, x offset, y offset, eccentricity, rotaHon angle) shape = SemiExtendedSourceModelShape(“gaussian”, 6.6, offset, 0.0, 0.0, 0.0) # Run the tool -­‐ the output is the corrected spectrum correctedSpectrum = semiExtendedCorrector(spectrum=spss, calibra<on=cal, \ doPlots=1, sourceModel=shape) For more SECT examples and an example script go to the 2014 spectroscopy workshop page: hdp://herschel.esac.esa.int/twiki/bin/view/Public/OnlineSpectroscopyWorkshop2014 Herschel Online Data Processing Workshop 19th June 2015 33 Analysing SPIRE FTS spectra AFGL2688 ② Point-­‐source observed with a significant poinHng offset SECT: correc<ng for poin<ng offset Running SECT in a script for the miss-­‐pointed AGL2688 observa6on: A) metaData offset = 3.37” B) rela<ve offset = 6.21” Step between the bands is reduced See the DRG 7.6. Recipes for semi-­‐extended sources RA and Dec requested might not be at the submm peak Step between the bands is removed RelaHve offset method gives the beAer result: but only possible if there are lots of observaHons of the same source Herschel Online Data Processing Workshop 19th June 2015 34 Analysing SPIRE FTS spectra ③ A source with parHally extended morphology NGC6302: the BuAerfly nebula with FWHM 18” ngc6302Obs = getObserva<on(1342265809, useHsa=True) See the DRG 7.6. Recipes for semi-­‐extended sources -­‐ raDecOffset is minimal (0.25”) -­‐ OD is > 1011 so bsmOffset is 0 Herschel Online Data Processing Workshop 19th June 2015 35 Analysing SPIRE FTS spectra ③ A source with parHally extended morphology NGC6302: the BuAerfly nebula with FWHM 18” ngc6302Obs = getObserva<on(1342265809, useHsa=True) Large jump between the bands! See the DRG 7.6. Recipes for semi-­‐extended sources -­‐ raDecOffset is minimal (0.25”) -­‐ OD is > 1011 so bsmOffset is 0 Herschel Online Data Processing Workshop 19th June 2015 36 Analysing SPIRE FTS spectra ③ A source with parHally extended morphology FTS calibraHon Point-like!
Semi-extended!
Extended!
Point-like!
Semi-extended!
Extended!
See the DRG 7.6. Recipes for semi-­‐extended sources Herschel Online Data Processing Workshop 19th June 2015 37 Analysing SPIRE FTS spectra ③ A source with parHally extended morphology FTS calibraHon Point-like!
Semi-extended!
Extended!
Point-like!
Semi-extended!
Extended!
NGC6302 See the DRG 7.6. Recipes for semi-­‐extended sources Point-­‐source calibrated spectra for a semi-­‐extended source Herschel Online Data Processing Workshop 19th June 2015 38 Analysing SPIRE FTS spectra ③ A source with parHally extended morphology SECT: correc<ng the data for extent The SECT algorithm is based on the forward coupling efficiency to the source distribuHon: so a good knowledge of the source distribu6on is key Here we use the default SECT secngs with: -­‐  a basic ellipHcal Gaussian -­‐  FWHM of 18” -­‐  Eccentricity of 0.2 -­‐  No x-­‐ or y-­‐offset And secng the source model diameter to be opHmised (op<miseDiameter=True). see Wu et al. 2013 & DRG SecHon 7.6 Herschel Online Data Processing Workshop 19th June 2015 39 NGC6302 Analysing SPIRE FTS spectra ③ A source with parHally extended morphology SECT: the plots SECT plots the correcHon applied see Wu et al. 2013 & DRG SecHon 7.6 if applyCorrec<on = 0 the correcHon is outpuAed (instead of the corrected data) Herschel Online Data Processing Workshop 19th June 2015 40 NGC6302 Analysing SPIRE FTS spectra ③ A source with parHally extended morphology SECT: the plots SECT plots the diameters tried when it searches for the opHmum -­‐> in this case 18.5” see Wu et al. 2013 & DRG SecHon 7.6 Herschel Online Data Processing Workshop 19th June 2015 41 NGC6302 Analysing SPIRE FTS spectra ③ A source with parHally extended morphology SECT: the plots SECT plots the uncorrected and corrected spectra No more jump see Wu et al. 2013 & DRG SecHon 7.6 The corrected spectra look good, but room for improvement: Needs beder knowledge of the source model! Herschel Online Data Processing Workshop 19th June 2015 42 Analysing SPIRE FTS spectra Line ficng Useful script: Spectrometer Line Fikng Fits sinc profiles to each line + polynomial for the conHnuum fit is performed simultaneously for each detector See the DRG 7.11. Spectral analysis Herschel Online Data Processing Workshop 19th June 2015 43 Analysing SPIRE FTS spectra Line ficng to SECT corrected NGC6302 Useful script: Spectrometer Line Fikng See the DRG 7.11 and the script itself for full details, but here’s a summary -­‐  The conHnuum is usually well approximated by a polynomial: The script uses a 3rd order polynomial -­‐  The 12CO lines are included as default Either add more to the list or follow the script to add a new list or read lines in from a text file -­‐  The unresolved instrumental line shape is approximately a sinc The script fixes the width using ‘actualResolu<on’ from the metadata -­‐  If lines are parHally resolved a sincGauss profile can be used Only necessary for lines with a width > 200 km/s -­‐  The script can be run with point-­‐source or extended source calibrated spectra -­‐  Redshi• can be input where necessary The output will need adjusHng to give redshi•, but the script tells you how! See the DRG 7.11. Spectral analysis Herschel Online Data Processing Workshop 19th June 2015 44 Analysing SPIRE FTS spectra Line ficng to SECT corrected NGC6302 Useful script: Spectrometer Line Fikng 13CO lines Polynomial fits the conHnuum well Fringing le• from point-­‐
source calibraHng semi-­‐
extended emission See the DRG 7.11. Spectral analysis Missed line might be affecHng fit to the nearby CO line A good start, but more lines needed to improve the results Herschel Online Data Processing Workshop 19th June 2015 45 Analysing SPIRE FTS spectra Line ficng to SECT corrected NGC6302 Useful script: Spectrometer Line Fikng See the DRG 7.11. Spectral analysis Herschel Online Data Processing Workshop 19th June 2015 46 Analysing SPIRE FTS spectra Apodized data Good for checking lines BUT line measurements should be performed on the standard data See the DRG 7.11. Spectral analysis Herschel Online Data Processing Workshop 19th June 2015 47 See the DRG 7.5.3 Check Spectral Noise Analysing SPIRE FTS spectra Spectral noise See the DRG 7.5.3/SPIRE Handbook/public twiki (see link below) for info on FTS noise, but here’s a summary: 1. Dominates for -­‐  There are three main sources of uncertainty faint sources 1.  Random noise – beats down with integra<on <me 2.  Large-­‐to-­‐mid scale systema<c noise associated with the instrument 3.  Small-­‐scale systema<c noise, i.e. fringing and line wings 3. Dominates -­‐  Measure the spectral noise to check of your data’s processing sources with the “error” column only represent the random noise strong lines Useful script: Es<mate Spectral Noise -­‐  Noise should be measured a•er subtracHng the lines Useful script: Line Fikng script -­‐  For faint sources and line subtracted data the noise should be at least as good as HSpot The Noise Es<mate script plots a comparison with HSpot -­‐  See the public twiki for the Spectrometer uncertainHes hAp://herschel.esac.esa.int/twiki/bin/view/Public/SpireCalibraHonWeb Herschel Online Data Processing Workshop 19th June 2015 48 See the DRG 7.5.3 Check Spectral Noise Analysing SPIRE FTS spectra EsHmaHng the noise Useful script: Spectrometer Noise Es<mate ③  A source with parHally extended morphology Plot adapted from the script Green dashed is noise esHmate for the data straight from the archive Lines dominate the noise NGC6302 Herschel Online Data Processing Workshop 19th June 2015 49 See the DRG 7.5.3 Check Spectral Noise Analysing SPIRE FTS spectra EsHmaHng the noise Useful script: Spectrometer Noise Es<mate ③  A source with parHally extended morphology Plot adapted from the script Blue is noise esHmate for SECT corrected. Noise goes up as data is corrected up Lines dominate the noise NGC6302 Herschel Online Data Processing Workshop 19th June 2015 50 See the DRG 7.5.3 Check Spectral Noise Analysing SPIRE FTS spectra EsHmaHng the noise Useful script: Spectrometer Noise Es<mate ③  A source with parHally extended morphology Plot adapted from the script Orange is noise esHmate for the SECT corrected and 12CO line fiAed and subtracted data SHll lines in there NGC6302 Herschel Online Data Processing Workshop 19th June 2015 51 See the DRG 7.5.3 Check Spectral Noise Analysing SPIRE FTS spectra EsHmaHng the noise Useful script: Spectrometer Noise Es<mate ③  A source with parHally extended morphology The noise is above HSpot due to SECT! Plot adapted from the script Red is noise esHmate for the SECT corrected and line subtracted data Most significant lines are removed The noise is above NGC6302 HSpot due to SECT! Herschel Online Data Processing Workshop 19th June 2015 52 See the DRG 7.10 Analysing SPIRE FTS sparse observaHons Comparing with the photometer: AFGL4106 HIPE task spireSynthPhotometry (used to be specMatchPhot) Background subtracted Pre-­‐background subtracHon Table dataset output -­‐ 
-­‐ 
-­‐ 
-­‐ 
Detectors SyntheHc phot SyntheHc phot errors Photometer phot Herschel On-­‐Line Spectroscopy Data Processing Workshop 24 April 2014 53 FTS spectra Analysing SPIRE Summary •  If you don’t have HIPE 13 data: update from the HSA •  The SDRG is the first port of call to look for help + info •  Background/poinHng/extent can all cause a jump between the bands •  Off-­‐axis subtracHon of backgrounds can be effecHve for point-­‐like source •  PoinHng offsets can be corrected with SECT (new dedicated poin<ng correc<on task for HIPE14) •  Source extent leads to poorly calibrated data: •  Semi-­‐extended data must be corrected with SECT •  You need a good understanding of the source •  Fit all lines (sinc) and conHnuum simultaneously •  Useful scripts provide a handy workflow within HIPE •  The best place to inspect, diagnose, correct and analyse your FTS data is in HIPE! Herschel Online Data Processing Workshop 19th June 2015 54 See the DRG 7.5.3 Check Spectral Noise Analysing SPIRE FTS spectra EsHmaHng the noise Useful script: Spectrometer Noise Es<mate ①  Point-­‐source embedded in extended emission -­‐ Background subtracHon affects large-­‐scale noise only BGS script results Noise for point-­‐source calibrate spectra HSpot Plot produced by the script Green dashed is noise esHmate for the background corrected data Lines dominate the “error” column noise Herschel Online Data Processing Workshop 19th June 2015 55 Analysing SPIRE FTS spectra The APE figure 7.37: Comparison of the 2σ APE distribuHon, shown as a blue cloud, before (le•) and a•er (right) OD 1011. See the DRG 7.4. PoinHng ConsideraHons Herschel Online Data Processing Workshop 19th June 2015 56