astronomical spectroscopy and the virtual observatory esac, 21-23 march 2007 vo tools and...

Astronomical Spectroscopy and the Virtual Observatory

ESAC, 21-23 March 2007

VO tools and cross-calibration

Pedro García-LarioEuropean Space Astronomy Centre

Herschel Science Centre



Calibration vs. Cross-Calibration

CALIBRATION

– Individual source analysis

– Single instrument

– Single spectral range

– Single units

– Single beam/aperture/filter

– Primary calibrators

– Raw data products

– Detailed interactive analysis

– Dedicated tools

CROSS-CALIBRATION

– Multiple source analysis

– Multiple instruments

– Multi-wavelength

– Multiple units

– Multiple beam/aperture/filter

– Secondary calibrators

– Calibrated data products

– Quick look / statistical analysis

– Multi-mission (common) tools

CL

AS

SIC

AL

OB

SE

RV

AT

OR

Y

CL

AS

SIC

AL

OB

SE

RV

AT

OR

Y

VIR

TU

AL

OB

SE

RV

AT

OR

Y

VIR

TU

AL

OB

SE

RV

AT

OR

Y



The ideal cross-calibration tool• Data browser capabilities

– Fast retrieval of all available images / photometry / line-range spectroscopy for a given source

– Flexible to incorporate additional data as soon as they become available

• Model browser capabilities– On-the-fly retrieval/selection of models, accompanied by basic fitting tools

• Able to deal simultaneously with different units – On-the-fly change of units

• Able to deal simultaneously with different spectral/spatial resolution data

– Rebinning tools / convolution tools

• Able to deal simultaneously with different beam/aperture/filters– Beam/aperture/filter corrections, including synthetic photometry from spectra

• User friendly graphical interface showing the results of the above in a common environment (platform independent)

• Quick look analysis / statistical tools– To evaluate e.g. goodness of fits and overall consistency of absolute flux calibration of

large data sets



Change of units tool



Synthetic photometry tools

MSX photometry IRAS photometry Synthetic photometry



Statistical analysis tools



Aperture photometry tools

J = 13.43 ± 0.06H = 12.07 ± 0.04K = 11.18 ± 0.04

J

H K

VDSSDSS 2MASS2MASS

2MASS2MASS 2MASS2MASS



Aperture photometry tools

J = 13.43 ± 0.06H = 12.07 ± 0.04K = 11.18 ± 0.04

J

H K

VDSSDSS 2MASS2MASS

2MASS2MASS 2MASS2MASS

Real life can be

even more complicated…



Rebinning tools



Spatial convolution tools

AKARI

IRCFIS

90 m 9 m

IRAS

12 m



ImagesSpectra

Catalogues

The cross-calibration ‘world’

Models

Otherspectra

Othercatalogues

OtherImages

Rebinning/flux units Convolution/surface brightness units

Colour correction/photometric units

Filter information/Synthetic photometry

Beam information/Aperture photometry

Spectral resolution information

Beam information

Photometric zero pointsFilter information



The (my) ideal Virtual Observatory• A system which allow users to interrogate multiple data centres and

services in a seamless and transparent way to access and visualize fully characterised astronomical data and models of very heterogeneous nature through specific protocols in a common environment…

• … accompanied by some data manipulation tools like e.g. change of units, simple arithmetics, statistical tools, spatial convolution, rebinning, synthetic photometry, aperture photometry

• … powerful to deal with large number of data sets: (over)-plotting capabilities, automated spectral/imaging classification,…

• … plus a few basic tools for quick look analysis: model fitting, line identification, redshift, radial velocity, extinction correction,…

• … which provides the capability to export your VO-processed data to your local environment according to your preferred view to complete your analysis with dedicated tools if needed

Remember: Remember: “You don’t have to do everything with the VO”“You don’t have to do everything with the VO”(A.Richards)(A.Richards)



Common problem(s)• Data characterisation model

• Use of large, uniformly calibrated data sets usually helps but it is not enough

• Full characterisation is not always possible

• Need of extra information not yet available through the VO in many cases

• Beam profile/aperture description, filter transmission profiles, photometric zero points, spectral resolution information are only examples of additional information needed to properly communicate existing VO applications (e.g. through PLASTIC)

• Quality information is a world apart because of its complexity

• Filter services and footprint services are a step forward

• Need of a common access protocol to handle this information (as part of the metadata?)

• Data providers must be conscious that this additional information is essential to handle their data properly in a VO environment

• Other information not so critical but also useful, e.g.: Object type (to facilitate queries), time info in catalogues (to generate light curves), links to publications, etc.



Summary

• VO tools and cross-calibration share many common objectives and deal with many common problems

• VO tools are already (or soon will be) able to collect and deal simultaneously with multi-wavelength images, photometry, line and range spectroscopy from an unlimited number of ground-based and space facilities

• Full data characterisation is the main common problem; some information is not yet properly handled by the VO

• Exploring synergies between VO and cross-calibration seems convenient and joining efforts ‘unavoidable’ ;-)

astronomical spectroscopy and the virtual observatory esac, 21-23 march 2007 vo tools and...

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