PACS spectroscopy Data Analysis

Transcription

1 PACS spectroscopy Data Analysis Elena Puga Herschel Science Centre ESA 27/10/2016 Exploiting the Herschel Science Archive E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 1

2 Outline 1. Examining PACS cubes PACS IFU Footprint viewer 2. Calibrated spectra for point sources 3. Calibrated spectra for semi-extended sources 4. Non-uniform illumination in the PACS IFU field-of-view Cube calibration Forward Modelling to assess flux loss in cubes E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 2

3 PACS Spectrometer Data Analysis This analysis is HIPE based Although all PACS Spectrometer data products are provided as FITS files, alternative software may not be entirely suitable for PACS data analysis Aimed at solving remaining artifacts or additional calibration corrections that are science case dependent. Details are provided in the PACS Spectrometer Data Reduction Guide (SpecDRG) E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 3

4 Examining PACS cubes PacsRebinnedCube is the level2/level2.5 final cube product for single-pointed observations Fully calibrated for extended sources [Jy/spaxel] Undersamples PSF with 5x5 9.4 x9.4 -size spaxel Spatially non-uniform cube Spatial direction E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 4

5 Examining PACS cubes PacsRebinnedCube is the level2/level2.5 final cube product for singlepointed observations Fully calibrated for extended sources [Jy/spaxel] Undersamples PSF with 5x5 9.4 x9.4 -size spaxel Spatially non-uniform cube HIPE 14.2 Spectrum Explorer Cube pane flips XY axes to display PacsRebinnedCubes uniformly in the native PACS IFU Footprint view Spectrum Explorer: Spacecraft orientation Postcard image: sky orientation (including roll angle) E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 5

6 Examining PACS cubes PacsRebinnedCube is the level2/level2.5 final cube product for single-pointed observations Fully calibrated for extended sources [Jy/spaxel] Undersamples PSF with 5x5 9.4 x9.4 -size spaxel Spatially non-uniform cube HIPE 14.2 Spectrum Explorer Cube pane flips XY axes to display PacsRebinnedCubes uniformly in the native PACS IFU Footprint view Spaxel indices (column,row) or alternatively Modules [0...24] PACS IFU 5x5 Footprint on sky coordinates in HIPE with pacsfootprintviewer GUI using task pacsspectralfootprint E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 6

7 PACS Spectral Footprint Viewer Tool Projects IFU footprint on sky coordinates. Documented in Sect SpecDRG Requires: Image with WCS (Photomer Map, or layer extracted from Nyquist/oversampled level2/2.5 spectral cube) PacsRebinnedCube or SlicedPacsRebinnedCube NGC6302 E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 7

8 PACS Spectral Footprint Viewer Tool Useful to visualize raster sampling in mapping observations footprintapi = pacsspectralfootprint(input=map, plotlabels=false, spaxelradius=0.1) footprintapi.addfootprint(slicedpacsrebinnedcube) E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 8

9 PACS Spectra for point sources The PACS Spectrometer absolute flux calibration links observations of science targets to observations of point sources with known flux densities [Jy] via a standard (uniformly illuminated) candle like the telescope emission (~200Jy) or the PACS internal calibration sources The Point Source Correction Factor (PSCF) accounts for the fraction of the total flux seen by the central spaxel/central 9 spaxels varying with wavelength. E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 9

10 PACS Spectra for point sources The PACS Spectrometer absolute flux calibration links observations of science targets to observations of point sources with known flux densities [Jy] via a standard (uniformly illuminated) candle like the telescope emission (~200Jy) or the PACS internal calibration sources The Point Source Correction Factor (PSCF) accounts for the fraction of the flux seen in the central spaxel/central 9 spaxels varying with wavelength. E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 10

11 PACS Spectra for point sources The PACS Spectrometer absolute flux calibration links observations of science targets to observations of point sources with known flux densities [Jy] via a standard (uniformly illuminated) candle like the telescope emission (~200Jy) or the PACS internal calibration sources The Point Source Correction Factor (PSCF) accounts for the fraction of the flux seen in the central spaxel/central 9 spaxels varying with wavelength. x source [tel]= signalsource signal telescope Fsource [Jy ]= x source PSCF F x Ceres PSCF Ceres x source Fsource [Jy ]= F PSCF telescope Level 2 SPG pipeline E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 11

12 PACS Spectra for point sources HIPE task extractcentralspectrum extracts spectra of the central (s1) and central 9 (s9) spaxels and applies correspondent PSCF Details in Sect in the SpecDRG Calibration files used: pointsourceloss Central spaxel has higher SNR spectrum, but suceptible to flux loss due to pointing mishaps Central 9 spaxels have lower SNR, but robust against pointing issues. In fact, absolute flux calibration is established on central 9 spaxels and transferred to central spaxel, via calibration file central/central9, calculated on Neptune raster. E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 12

13 ExtractCentralSpectrum The task provides with a pointing correction scaling the central spaxel extracted spectrum to the point source calibrated central 9 spectrum Analogue to correcting the central spaxel spectrum by the slope ratios of the source and a perfectly centred point source, and then apply the aperture correction Final spectrum c129 is HIGHER SNR AND ROBUST against pointing offsets E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 13

14 ExtractCentralSpectrum The task provides with a pointing correction scaling the central spaxel extracted spectrum to the point source calibrated central 9 spectrum Analogue to correcting the central spaxel spectrum by the slope ratios of the source and a perfectly centred point source, and then apply the aperture correction Final spectrum c129 is HIGHER SNR AND ROBUST against pointing offsets Only applicable on: - Point sources - Detected in central spaxel - Isolated - Background free Correction is calculated according to instrument mode: Line and Small Range : median correction (shown in command line) Range and SEDs : wavelength dependent E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 14

15 ExtractCentralSpectrum Plots Blue indicates slope ratios and may be indicative of semi-extended source if values are > 2 Green the correction applied to the central spaxel spectrum, before applying PSCcentral E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 15

16 PACS Spectra for semi-extended sources The spectrum of a source with spatially extended morphology observed in single pointing will be underestimated. Correction to account for the the coupling of the source flux distribution model with the system response Fsource [Jy ]= ηc1 = x source PSCF η FCeres s x Ceres (beam) f source (y, z)nbeamss ( y, z)dy dz PSCF c1 E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 16

17 PACS Spectra for semi-extended sources Requires: Model of the source's brightness distribution Diameter within the central 9 spaxels (<15 ) Beam efficiencies Assumptions: HIPE Chosen model is representative of source's distribution Source model is valid at all wavelengths per band task pacsextendedtopointcorrection (E2P hereafter) Possible model inputs: - In-built analytical functions: Top-hat, Gaussian - User-provided analytical function in the form of a Python class with a function getflux - User provided high spatial resolution map (e.g. ALMA map) Documented in Sect. 8.6 in the SpecDRG E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 17

18 PACS Spectra for semi-extended sources Requires: Model of the source's brightness distribution Diameter within the central 9 spaxels (<15 ) Beam efficiencies Assumptions: HIPE Chosen model is representative of source's distribution Source model is valid at all wavelengths per band task pacsextendedtopointcorrection (E2P hereafter) Documented in Sect. 8.6 in the SpecDRG E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 18

19 PACS Spectra for semi-extended sources NGC7027 planetary nebula Symmetric Gaussian FWHM=12 E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 19

20 Non-uniform Illumination in the IFU's FOV The PACS Spectrometer beam efficiencies are maps of the response of each detector on the sky. They are a reconstruction of what every pixel sees as Neptune was rastered across each detector's aperture on the sky. Therefore, the coaddition of the 25 beams for all spaxels yields the illumination pattern PACS Illumination um E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 20

21 Non-uniform Illumination in the IFU's FOV In our extended-source calibration, it is assumed a flat response over the 9.4 x9.4 area of each spaxel Simple modeling This is not fulfilled, particularly at short wavelengths! Deconvolving the beam with the Photometer's PSF reveals an active area of ~8 x8 62 um 145 um E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 21

22 Cube Calibration PacsRebinnedCubes and spectral cubes for mapping observations are calibrated for fully extended emission f s [ ] [ ] [ ] Jy Jy Jy 1 =x s [tel] f telescope =x s [ tel] f telescope spaxel spaxel beam spaxel ESCF beam [ Pipeline After HIPE 13.0 E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 22 ]

23 Cube Calibration PacsRebinnedCubes imperfect for and spectral cube calibration in surface brightness may be Off centred point sources Crowded fields Semi extended structures x s [ tel] f telescope [ ] 2 Jy 9.4 =ξs [ Jy ] spaxel spaxel Pipeline After HIPE 13.0/ESCF ξ s = (beam) f source ( y, z)nbeams s (y, z)dy dz E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 23

24 Forward model to assess flux loss in cubes Forward Model Tool in HIPE 15.0 will simulate PACS cubes according to userprovided source flux distribution model (spatially and spectrally) to perform this calculation in a transparent way. Forward modelling of extreme cases produces: Point source: PSCF Fully extended source: ESCF Observation Simulation E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 24

25 Forward model to assess flux loss in cubes Forward Model Tool in HIPE 15.0 will simulate PACS cubes according to userprovided source flux distribution model (spatially and spectrally) to perform this calculation in a transparent way. Forward modelling of extreme cases produces: Point source: PSCF Fully extended source: ESCF Observation Simulation E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 25

26 Forward model to assess flux loss in cubes Forward Model Tool in HIPE 15.0 will simulate PACS cubes according to userprovided source flux distribution model (spatially and spectrally) to perform this calculation in a transparent way. Forward modelling of extreme cases produces: Point source: PSCF Fully extended source: ESCF Observation Simulation The ratio gives idea on surface brightness losses E. Puga Exploiting the Herschel Science Archive: PACS Spectrometer Data Analysis ESAC 27/10/2016 Slide 26