NHSC/PACS Webinar PACS Point Source Photometry. Aperture Photometry and Photometric Uncertain5es. Roberta Paladini NHSC PACS.

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1 NHSC/PACS Webinar PACS Point Source Photometry Aperture Photometry and Photometric Uncertain5es Roberta Paladini July

2 Content I Point- source aperture photometry in HIPE II Calibra=on errors III Photometric uncertain=es: noise per pixel and cross- correlated noise IV Aperture correc=ons V Color Corrections VI Non- linearity correc=ons Requirement: HIPE 8.0 or later version Applies to: mini scan map / large scan map It does not apply to extended sources 2

3 PART I: Point Source Aperture Photometry in HIPE 3

4 Aperture Photometry: General Q.: how do I perform aperture photometry if I have a mini map with a central source? Task in HIPE annularskyaperturephotometry uses circular target aperture annular or rectangular (rectangularskyaperturephotometry) sky aperture user can provide fixed sky value (fixedskyaperturephotometry) 5 algorithms to es5mate sky: average, median, mean- median, mode, daophot both GUI and command line versions 4

5 annularskyaperturephotometry GUI 3. The image appears in a new tab within the Editor view 2. Click on Applicable and annularskyaperturephotometry 1. Load.fits file

Then, click Accept 3 ways to iden5fy the source 1.

6 4. Scroll down : you will find an interface to enter task op=ons 5. Set: source center coordinates, source and sky radius. Then, click Accept 3 ways to iden5fy the source 1. By clicking with the mouse 2. By entering X e Y center pixel coordinates 3. By entering sky coordinates (RA and DEC) 6

7 6. The source and sky apertures are shown in the image 7. Click on result. A table will open in the Editor view 7

$fits ) Now do aperture photometry Frac=onal: whether frac:onal pixels are going to be used. 1 = True (default), 0 = False HIPE> phot = annularskyaperturephotometry(image =map, centerra= 02:00:34.$

8 annularskyaperturephotometry command line - I Load.fits file containing map HIPE>map=FitsArchive().load(dir+ AlphaBoo_070.fits ) Now do aperture photometry Frac=onal: whether frac:onal pixels are going to be used. 1 = True (default), 0 = False HIPE> phot = annularskyaperturephotometry(image =map, centerra= 02:00:34.388,centerDec= - 22:28:14.89,radiusArcsec=12,innerArc sec=20,outerarcsec=25,frac5onal=1,algorithm=4) Algorithm: sky es5ma5on algorithm. 0 for average, 1 for median, 2 for mean- median, 3 for mode, 4 for Daophot. 8

9 annularskyaperturephotometry command line - II Recommended source and sky apertures (arcsec) Blue Green Red Source aper 12 (5.5) 12 (5.6) 22 (10.5) Sky aper (inner) Sky aper (outer) For sources fainter than ~ 500 mjy, smaller apertures are recommended (see values in parenthesis). 9

10 Documenta=on for Part I annularskyaperturephotometry: h4p://herschel.esac.esa.int/hcss- doc- 8.0/print/howtos/howtos.pdf ( Sect. 4.12) Apertures: hgp://herschel.esac.esa.int/twiki/pub/public/pacscalibra5onweb/pacs_bolo_fluxcal_report_v1.pdf (PICC- ME- TN- 037) Simple Aperture Photometry Plugin (NEW!): hgps://nhscsci.ipac.caltech.edu/pacs/scripts/plugins/pacssimpleaperturephotometry_1.0.jar ( performes aperture photometry of unblended sources on single or mul5ple PACS frames. Calls the annularskyaperturephotometry task.) 10

11 PART II: PACS Point Source Calibration Errors 11

12 Calibra=on: Summary In the FM6 calibra5on framework (- > responsivity file valid for HIPE 8): PACS photometer flux calibra5on is based on the observa5ons of 5 fiducial stars (β And, α Cent, α Tau, α Boo, γ Dra) These primary calibrators are complemented with a set of secondary calibrators, namely 18 large main- belt asteroids Both stars and asteroids have been observed mul5ple 5mes in all 3 bands with 20 /s scan- speed, in 2 scan direc5ons (70 0 and ) and in high gain All the data have been processed in a homogeneous way. The final flux densi5es have been derived using aperture and color correc5ons Model uncertain5es amount to 5% All primary calibrators (i.e. 5 fiducial stars) are in the linear regime PACS photometer observa5ons of point sources below ~100 Jy are accurate to within 3%, 3% and 5% in the blue, green and red band, respec5vely. 12

13 70µm 13

14 100µm 14

15 160µm Median/stdev: / (54 obs) 15

16 Preview FM6 (HIPE 8) FM7 (HIPE 9): a new flat- field and Point- Spread func5ons have been re- derived, leading to an improved responsivity file which is being implemented in HIPE 9 Note though that this will only correspond to a change in responsivity of < 1% in the blue/green band and ~2% in the red 16

17 Documenta=on for Part II PACS photometer Point Source Flux Calibra5on: hgp://herschel.esac.esa.int/twiki/pub/public/pacscalibra5onweb/pacs_bolo_fluxcal_report_v1.pdf (PICC- ME- TN- 037) and hgps://nhscsci.ipac.caltech.edu/sc/index.php/pacs/absolutecalibra5on ( web pages) hgp://herschel.esac.esa.int/twiki/bin/view/public/pacscalibra5onweb (PACS calibra5on page at ESA) 17

18 PART III: Photometric uncertainties noise per pixel and correlated noise 18

19 Current Status Q: In HIPE 8, the Level 2 error map is populated with zeros: why? 1. In Level 1 of the mini- scan map PACS processing pipeline, a high- pass filter is applied in order to remove the 1/f noise 2. because of that, the 5meline noise power spectrum changes dras5cally, making the standard error propaga5on unfeasible 3. therefore, error propaga5on is not supported and the Level 2 error map is set to zero 19

20 Current Recommended Solu=on Concept: The photometric error for point- source aperture photometry can be es5mated from empty background in the image Method: Do aperture photometry of background at different posi5ons (10+) and take r.m.s. as es5mate 20

21 Preview: Op=mal Solu=on (to be implemented in HIPE 10) Let s step back.. The noise in a PACS map has 2 components: 1) noise per pixel: this normally scales as the inverse of the square root of the observing 5me (i.e. the coverage) this component should be es5mated via error propaga5on (but high- pass filter makes it very inaccurate) 2) cross- correlated noise: residual (low- level) 1/f noise leu in the 5melines auer applying high- pass filter projec5on of 5melines into map (e.g. via the PhotProj task). In par5cular, the projec5on parameters (output pixel size and drop size) control the level of cross- correla5on induced in the map Upcoming solu5on (soon implemented in HIPE): error es5mate for high- redundancy and low- redundancy cases, separately. Noise behavior as func5on of high- pass filter radius, source masking, output pixel size and drop size. 21

22 Documenta=on for Part III Current status and solu5on: hgp://herschel.esac.esa.int/twiki/bin/view/public/dpknownissues?template=viewprint (see PACS photometer scan mapping - > No absolute noise map ) Upcoming implementa5on of op5mal solu5on: soon to be available! 22

23 PART IV: Aperture Corrections 23

Aperture Correc=ons I Any aperture photometry performed with a given source aperture radius is inevitably affected by flux loss, due to the fact that any finite radius cannot capture all

24 Aperture Correc=ons I Any aperture photometry performed with a given source aperture radius is inevitably affected by flux loss, due to the fact that any finite radius cannot capture all the source flux To correct for this effect, one has to apply aperture correc:ons For PACS, aperture correc5ons are defined in terms of Encircled Energy Frac:ons (EEFs): Point Spread Func5on 24

Aperture Correc=ons II PACS aperture correc5ons are derived from observa5ons of Vesta and Mars Aperture correc5ons depend on the responsivity version (FM6, FM7, etc.

25 Aperture Correc=ons II PACS aperture correc5ons are derived from observa5ons of Vesta and Mars Aperture correc5ons depend on the responsivity version (FM6, FM7, etc..) In HIPE, aperture correc5ons are applied with the task: photaperturecorrec:onpointsource() Aperture correc=ons are contained in caltree HIPE > caltree=getcaltree() HIPE > caltree.refs[ photometer ].product.refs[ aperturecorrec5on ].product HIPE > apcorr_r = apcorr[ fm6apertureradius ].data HIPE > apcorr70 = apcorr[ fm6bandblue ].data HIPE > apcorr100 = apcorr[ fm6bandgreen ].data HIPE > apcorr160 = apcorr[ fm6bandred ].data 25

26 Documenta=on for Part IV Aperture correc5ons: hgp://herschel.esac.esa.int/twiki/pub/public/pacscalibra5onweb/bolopsf_20.pdf (PICC- ME- TN- 033) and hgps://nhscsci.ipac.caltech.edu/sc/index.php/pacs/aperturecorrec5ons ( web pages) 26

27 PART V: Color Corrections 27

Color Correc=ons Color correc:ons are needed to convert PACS monochroma5c flux densi5es ( νf ν = λf λ = const) to the true object SED flux densi5es at the PACS reference wavelengths (70µm, 100µm,

28 Color Correc=ons Color correc:ons are needed to convert PACS monochroma5c flux densi5es ( νf ν = λf λ = const) to the true object SED flux densi5es at the PACS reference wavelengths (70µm, 100µm, 160µm) The effec5ve response of the PACS filter is given by: Filter Transmission X Detector Rela5ve Spectral Response HIPE > cal = getcaltree().photometer.absorp5on HIPE > cal = getcaltree().photometer.filtertransmission Color correc5ons for various source SEDs can be found in PICC- ME- TN- 038: hgp://herschel.esac.esa.int/twiki/pub/public/pacscalibra5onweb/cc_report_v1.pdf 28

29 Documenta=on for Part V Color correc5ons and PACS bolometer response: hgp://herschel.esac.esa.int/twiki/pub/public/pacscalibra5onweb/cc_report_v1.pdf (PICC- ME- TN- 038) and hgps://nhscsci.ipac.caltech.edu/sc/index.php/pacs/colorcorrec5ons ( web pages) hgps://nhscsci.ipac.caltech.edu/sc/index.php/pacs/spectralresponse ( web pages) 29

30 PART VI: Non-linearity Corrections 30

Non- linearity: Summary Our knowledge of PACS flux non- linearity is based on pre- flight ground- based calibra5on non- linearity correc5on is of the order of 10% for a signal ~ 60 Jy/pixel this is a

31 Non- linearity: Summary Our knowledge of PACS flux non- linearity is based on pre- flight ground- based calibra5on non- linearity correc5on is of the order of 10% for a signal ~ 60 Jy/pixel this is a small effect (i.e. 0-15%) even for very bright sources (> 100 Jy) the effect is independent of the gain se{ng In HIPE 8, the non- linearity correc5on is applied (Level 1) by the task: photnonlinearitycorrec:on() 31

32 Documenta=on for Part VI Flux non- linearity: hgps://nhscsci.ipac.caltech.edu/sc/index.php/pacs/nonlinearity ( web page) and hgp://herschel.esac.esa.int/twiki/pub/public/pacscalibra5onweb/photminiscan_releasenote_ pdf (PICC- ME- TN- 033, see Sect. 6.3) 32

33 Thank you! 33

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