1. X-ray high resolution spectra in the VO: the case of XMM-Newton RGS
R. González-Riestra
P.M. Rodríguez-Pascual
XMM-Newton Science Operations Centre
ESAC
Astronomical Spectroscopy and the Virtual Observatory, March 21st 2007, ESAC

2. Can X-Ray spectra be included in the VO ?
Not calibrated
Response matrices are not invertible
Fluxes are model dependent NO
YES
In some cases response matrices are nearly diagonal
Calibrated data - useful for some purposes, when detailed spectral analysis is not required - can be provided
Example: XMM-Newton RGS spectra
So far X ray spectra are poorly represented in the VO
Why?
The traditional view is that since x-ray response matrices cannot be inverted, x-ray data cannot be given in physical units, since fluxes are model-dependent
But this is not always the case, since sometimes the matrices are nearly diagonal, and, if no detailed spectral analysis is required, it is possible to provide data in physical units.
This is the case for X-rays high resolution spectra and in particular for xmm rgs,that i am going to refer to in this talk
Astronomical Spectroscopy and the Virtual Observatory, March 21st 2007, ESAC

3. RGS: The XMM-Newton Reflection Grating Spectrometer
Operates in parallel with the EPIC cameras and the Optical Monitor
Provides X-ray high resolution (R = ) spectroscopy in the spectral range Å
Extracted spectra can be corrected for the effective area and provided in physical units (Flux vs. Wavelength): RGS fluxed spectra
Since there might be people in the audience not familiar with xray instrumentation, these are the basic characteristics of RGS
Astronomical Spectroscopy and the Virtual Observatory, March 21st 2007, ESAC

4. Currently RGS data are not uniformly processed (different versions of SW and of Calibration Files)
Fluxed spectra are not produced in the standard pipeline processing
Database containing:
~ 4600 RGS fluxed spectra uniformly processed
Plus some ‘added value’ items relevant to the interpretation of the data
Tool for data browsing and evaluation
I am going to show here an example of a tool designed for browsing and quick look evaluation of RGS spectra
The tool provides access to 4600 spectra. these spectra have been processed in an uniform (that does not mean necessarily optimal) way
This tool, currently into development, includes access not only to the spectra, but also an associated database, with some ‘added value’ information (if you want you may call this METADATA)
BiRD
Browsing interface for RGS Data
Astronomical Spectroscopy and the Virtual Observatory, March 21st 2007, ESAC

5. a Browsing interface for RGS Data
BiRD
Astronomical Spectroscopy and the Virtual Observatory, March 21st 2007, ESAC
Search by:
Object name
Coordinates
Observing date
Observation Id
Additional search criteria:
Type of object
Quality
Hydrogen Column
Redshift
Exposure time
I do not want to put much emphasis in the interface itself, but in the tools it may provide to the user.
In addition to the normal query possibilities (object, coordinates, less usual time) there some additional keywords, as type of object, a estimation of the quality of the spectrum, redshift and galactic Hydrogen column density that is particularly important for the analysis of X-ray data (this is specific to this set of data, but the principle remains)
Optional output fields:
Simbad name
Simbad Type
Simbad Coordinates
Observing date
Exposure time
Quality
Hydrogen Column
Redshift

6. Simbad query by object or by coordinates
a Browsing interface for RGS Data
BiRD
Astronomical Spectroscopy and the Virtual Observatory, March 21st 2007, ESAC
sample selection
plotting options
This is the output page. I would like to go a bit in detail to see all the possibilities it offers:
-links to the observing log that may be useful to asses the quality of the observation
-links to simbad, and to the list of publications
ability to select/un-select records for further visualization (and some settings associated to it)
On the right hand side, spectrum visualization, and some other information relevant in the context of this dataset
blue boxes are interactive tools
XMM OLB
XSA
Publications
Simbad query by object or by coordinates
Spectrum plot
Spectral Image
X-ray Image
X-ray True Color Image

7. a Browsing interface for RGS Data
BiRD
Astronomical Spectroscopy and the Virtual Observatory, March 21st 2007, ESAC
Single Spectrum Plot
There are several plot-related parameters that allow a very basic display of the spectra (units, binning - with different possibilities, smoothing)
Most of the existent tools seems to emphasize in the multiwavelength approach. Since it is not relevant here, in this tool we have allowed here the possibility to select a sub-sample of data (in the previous page) and either plot them together, or plot their average.
This may be useful for some obvious purposes
to compare spectra of variable objects
to improve the s2n ratio by averaging several spectra of the same target
to visualize the average spectrum of a type of objects
important: as records can be selected/un-selected, the user can make his/her own sample

8. a Browsing interface for RGS Data
BiRD
Astronomical Spectroscopy and the Virtual Observatory, March 21st 2007, ESAC
For a single object
For a class of objects
For an user-defined sample
Multiple Spectra Plot
Average Spectrum Plot

9. a Browsing interface for RGS Data
BiRD
Astronomical Spectroscopy and the Virtual Observatory, March 21st 2007, ESAC
A related utility is the possibility to examine the X-ray image taken simultaneously with the spectrum.
There are different ‘flavors’, but the most useful one, in this case that we are dealing with an slit less spectrograph with a ‘large’ FOV in the direction perpendicular to the dispersion (5 arcmin) is the possibility to compare both images and the spatial profiles.
This may be particularly important:
When there are several emitting objects in the FOV, spectra can be superimposed, depending on the orientation. This should be carefully checked, since it can affect the interpretation of the spectra
in the case of extended objects

10. a Browsing interface for RGS Data
BiRD
Astronomical Spectroscopy and the Virtual Observatory, March 21st 2007, ESAC
These are a couple of examples of the utility of diplaying the spectral image

11. A wish list for a visualization tool for spectra
Data sets uniformly processed and calibrated
Estimation of the quality of the data
Basic plotting and display tools (rebinning, smoothing ...)
Comparison of spectra and images, if applicable
Ability to build sub-samples of data with specific characteristics (date of observation, redshift...)
Access to additional information (object classification, parameters pertinent to the specific dataset, publications…) of relevance for the interpretation of the data
I have shown here an example of a simple interface that includes some tools for an easy and quick evaluation of spectroscopic data.
This tool cover the basic needs of an average user:
Basic plotting and display facilities
Ability to build samples of data for further manipulation
Estimation of the quality of the data
Access to other information relevant for the analysis of the data
Although this tool has been designed for X-ray spectra, the principle can be easily applied to any other dataset with different specific characteristics and needs.
Astronomical Spectroscopy and the Virtual Observatory, March 21st 2007, ESAC